CD16a-binding polypeptide

Abstract

The invention provides CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and which further comprises at least one additional functional portion, wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker, wherein the or each linker is as defined in the specification. The invention further provides pharmaceutical compositions comprising the hBCMA-binding polypeptide, and the use of the hBCMA-binding polypeptide or pharmaceutical compositions as a medicament, particularly for use in the treatment or prophylaxis of cancers.

Description

[0001] Novel polypeptides Field of the Invention The present invention relates to immune cell-engaging polypeptides comprising a CD16a-binding polypeptide and at least one additional functional portion, or comprising at least two CD16a-binding polypeptides and optionally at least one additional functional portion, having a linker as described here. The present invention also relates to immune cell-engaging polypeptides comprising a CD16a- binding polypeptide. The present invention also relates to pharmaceutical compositions comprising said immune cell-engaging polypeptides, and their use in the treatment and / or prophylaxis of cancer. Background of the Invention Immunotherapy has proven to be an effective treatment of several cancers with approved therapies constituting monoclonal and bispecific antibodies, immunomodulatory drugs and CAR-T treatments. Despite activity of these treatments, however, some patients exhibit very short responses or fail to respond to treatment. Side effects from some immunotherapies can be severe, especially side effects related to an exacerbated cytokine release. Indeed, cytokine release syndrome is one of the most common serious adverse effects of T cell-engaging immunotherapeutic agents (Shimabukuro-Vornhagen A et al. Cytokine release syndrome. J Immunother Cancer.2018;6(1):56. doi:10.1186 / s40425-018-0343-9). Many patients will also, eventually, become resistant to available treatments. Thus despite recent advances, there is still a need for additional treatment options in cancer immunotherapy. One apparent obstacle with current treatment modalities is suboptimal distribution to tumorous tissue. Rates of tissue distribution are negatively correlated with molecular size, and so larger molecules such as antibodies have less efficient tumour penetration than smaller ones. Another issue is immune evasion by cancer cells, which often involves inhibitory immune signals in the tumour environment. Examples of such signals include: the production of immunosuppressive cytokines and other molecules, such as TGFβ or VEGF; cell-mediated immunosuppression, e.g. via tumour-derived regulatory T cells; modulation of antigen presentation and MHCI expression; or altered expression of other ligands, e.g. increased expression of inhibitory checkpoint ligands (such as Programmed death-ligand 1 (PD-L1) and HLA- E), which reduces tumour cell killing by CD8+ T cells and natural killer (NK) cells (Vinay D et al, Immune evasion in cancer: Mechanistic basis and therapeutic strategies, Seminars in Cancer Biology.2015:35 (Supplement):S185, https: / / doi.org / 10.1016 / j.semcancer.2015.03.004; Ben-Shmuel A et al, Unleashing Natural Killer Cells in the Tumor Microenvironment - The Next Generation of Immunotherapy? Front Immunol.2020;11:275, doi:10.3389 / fimmu.2020.00275). NK cells are a component of the innate immune system whose functions include cytokine secretion and cell killing via secretion of perforin- and granzyme-containing cytolytic granules. They are capable of antibody-dependent cellular cytotoxicity (ADCC) when target cells, such as tumour cells, are bound by IgG antibodies. Binding of the Fc antibody region to the CD16 receptor (FCγRIII) on NK cells overrides inhibitory signals, triggering cytokine secretion and lysis of the target cell (Vivier E et al, Functions of natural killer cells, Nat Immunol.2008;9:503, https: / / doi.org / 10.1038 / ni1582; Pallmer K and Oxenius A, Recognition and regulation of T cells by NK cells, Front Immunol 2016, 7:251, https: / / doi.org / 10.3389 / fimmu.2016.00251). CD16 is expressed in two forms, CD16a and CD16b, which vary in their expression patterns and affinities for IgG Fc. CD16a is the form predominantly expressed on NK cells, as well as being found on monocytes. CD16b, in contrast, is mostly found on neutrophils, though its expression can also be induced on eosinophils. Despite the high degree of sequence similarity (around 96%) between CD16a and CD16b, CD16a has a much higher binding affinity for IgG. (Roberts JT and Barb AW, A single amino acid distorts the Fc γ receptor IIIb / CD16b structure upon binding immunoglobulin G1 and reduces affinity relative to CD16a, J Biol Chem.2018;293(51):19899-19908, doi:10.1074 / jbc.RA118.005273). Genotypic variation of the CD16a (FcγRIIIa) receptor itself can also alter its binding affinity: the FcγRIIIa-176V / F polymorphism (rs396991) (in some publications where the leader sequence is excluded, position 176 is reported as position 158 and this numbering is also used in the Examples herein) results in either a valine (V) or phenylalanine (F) at position 176, giving rise to variable binding phenotypes (F / F: low affinity; V / V or V / F: high affinity, and therefore higher NK cell-mediated ADCC). (Chong KT et al., Distribution of the FcγRIIIa 176 F / V polymorphism amongst healthy Chinese, Malays and Asian Indians in Singapore, Br J Clin Pharmacol 2006;63(3): 328-332, doi: 10.1111 / j.1365- 2125.2006.02771.x). Recently, there has been increasing interest in harnessing the NK cell response for cancer immunotherapy. These include use of checkpoint inhibitor blockers, the ex vivo expansion and administration of NK cells, production of CAR-NK cells (analogous to CAR-T cell therapies), and the use of bi- or multivalent NK cell engagers that cross- link NK cells to cancer cells expressing specific antigens (Hofer E and Koehl U, Natural Killer Cell-Based Cancer Immunotherapies: From Immune Evasion to Promising Targeted Cellular Therapies, Front Immunol.2017;8:745, https: / / doi.org / 10.3389 / fimmu.2017.00745). Antibody-based NK engagers under development include Affimed’s AFM13 (an anti- CD16a / CD30 tetravalent bispecific antibody) and AFM24 (an anti-CD16a / EGFR IgG1- scFv fusion antibody). Both AFM13 and AFM24 have additionally been tested for their ability to induce tumour cell killing by macrophages via antibody-dependent cellular phagocytosis (ADCP) (Wingert S et al, Preclinical evaluation of AFM24, a novel CD16A-specific innate immune cell engager targeting EGFR-positive tumors. MAbs.2021;13(1):1950264. doi:10.1080 / 19420862.2021.1950264; Wingert S et al, CD16A-Specific Tetravalent Bispecific Immune Cell Engagers Potently Induce Antibody-Dependent Cellular Phagocytosis (ADCP) on Macrophages, Blood 2018;132(Supplement 1):1111, https: / / doi.org / 10.1182 / blood-2018-99-118427). Other bi- and multivalent NK engagers include the camelid VHH antibody-derived BiKEs and TriKEs, such as GT Biopharma’s GTB-3650 which contains CD33- and CD16a-targeting regions joined to the costimulatory molecule IL15. A further bispecific cell engager under development is RO7297089. RO7297089 is a bispecific tetravalent antibody targeting CD16a and BCMA (B‑Cell Maturation Antigen). BCMA is highly expressed on MM cells. The properties of the antibody compound were described in Kakiuchi-Kiyota et al. (Leukemia (2022) 36:1006–1014; https: / / doi.org / 10.1038 / s41375-021-01478-w), The findings from a Phase I dose- escalation study of RO7297089 in patients with Relapsed / Refractory Multiple Myeloma (Study registration NCT04434469) were reported by Plesner et al. (Poster Abstract 2755, Session 653, American Society of Hematology (ASH) Conference, 12 December 2021). Despite this progress, antibody-derived NK engagers still share the inherent difficulties associated with existing antibody cancer therapeutics, especially with regard to immunogenicity and tissue penetration. There therefore remains a need for improved cancer immunotherapeutics that can be delivered more efficiently to the tumour, while retaining the target specificity of antibodies and antibody-based drugs and avoiding potential side-effects. The present invention seeks to address the afore-mentioned needs. Summary of the Invention The present invention provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and which further comprises at least one additional functional portion, wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker, wherein the or each linker comprises one or more groups selected from the group consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooxtane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione, wherein n is 1 to 30, wherein m is 1 The present invention also provides CD16a-binding oligomer, which comprises at least two CD16a-binding polypeptides, wherein each CD16a-binding polypeptide comprises at least one motif that binds to CD16a, and wherein each CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and wherein the CD16a-binding polypeptides are each separated by a linker, wherein the or each linker comprises one or more groups selected from the group consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooctane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione, wherein n is 1 to 30, wherein m is 1 and wherein the CD16a-binding oligomer optionally further comprises at least one additional functional portion, wherein the CD16a-binding oligomer and an additional functional portion are separated by a linker, and wherein the or each linker comprises one or more groups selected from the groups consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooctane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione, wherein n is 1 to 30, wherein m is 1 The present inventors have surprisingly found that CD16a-binding polypeptides and CD16a-binding oligomers of the invention based on a non-antibody scaffold are effective in engaging NK cells and triggering ADCC-mediated cancer cell killing. Such CD16a-binding polypeptides and CD16a-binding oligomers are especially effective in engaging NK cells and triggering ADCC-mediated cancer cell killing. Furthermore, the CD16a-binding oligomers and CD16a-binding polypeptides of the invention comprising the specific synthetic linkers as described herein may be synthesised by chemical methods, for example by solid phase synthesis, leading to advantages in respect of ease of production and purity of the oligomers and polypeptides, as well as increased choice of spacing and arrangement of the polypeptides and oligomers. This allows modulation of the properties of the polypeptides and oligomers, such as length and flexibility (or rigidity), as well as optimisation of spatial arrangement to maximize biological function. For example, the synthetic linkers of the present invention allow precise control of distance and conformational freedom between each CD16a-binding polypeptide and / or other functional portion(s). Control of the ordering and arrangement of targeting domains of the polypeptides and oligomers is also possible. For example the synthetic linkers described herein allow the possibility to connect the N-terminal of a CD16a-binding polypeptide with the N-terminal of another CD16a-binding polypeptide and / or other functional portion, and the possibility to connect the C-terminal of a CD16a-binding polypeptide with the C-terminal of another CD16a-binding polypeptide and / or other functional portion. Using synthetic linkers as described herein also allows the possibility of connecting CD16a-binding polypeptides and / or other functional portion at a position within the N-terminal portion or C-terminal portion of a CD16a-binding polypeptide, as well as using branched linkers. Finally, the linkers of the present invention are both stable and non-toxic, and thus are especially suitable for use with the polypeptides and oligomers of the present invention, which find utility as anti- cancer immunotherapeutics. The invention also provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]; wherein the CD16a-binding motif sequence is selected from SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044) of Figure 14. The invention also provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]; wherein the sequence of the CD16a-binding polypeptide is selected from SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) of Figure 12. The invention therefore provides novel CD16a engagers that shows promise as an anti-cancer immunotherapeutic. The invention further provides a method of making the CD16a-binding polypeptide or CD16a-binding oligomer of the invention. The invention also provides a pharmaceutical composition comprising a CD16a- binding polypeptide, CD16a-binding oligomer, or CD16a binder-drug conjugate of the invention. The invention further provides a CD16a-binding polypeptide, CD16a-binding oligomer, CD16a binder-drug conjugate, or pharmaceutical composition of the invention for use in medicine, in particular in the treatment of a cancer. The invention also provides the use of a CD16a-binding polypeptide, CD16a-binding oligomer, CD16a binder-drug conjugate, or pharmaceutical composition of the invention for the manufacture of a medicament for the treatment of cancer. The invention also provides a method of treating cancer in which the method comprises administering to a patient in need thereof a CD16a-binding polypeptide, CD16a-binding oligomer, CD16a binder-drug conjugate, or pharmaceutical composition of the invention. The invention further provides a kit comprising a CD16a-binding polypeptide, CD16a- binding oligomer, CD16a binder-drug conjugate, or pharmaceutical composition of the invention and, optionally, one or more further therapeutic agent(s). Such a kit finds particular use in the treatment and / or prophylaxis of cancer. Description of the Drawings Figure 1 shows (a) schematic domain construction of the binding polypeptides described in the present disclosure; (b) examples of results from a phage-ELISA experiment used to screen individual clones present in the phage output after selection cycle four. In (b), assay responses to coating antigens (1) HSA, (2) Streptavidin, (3) SLAMF7 and (4) hCD16a F158 were measured and representative results for clones corresponding to CD16a-binding polypeptides A10, H09 and A11, respectively, are shown. Figure 2 shows an SDS-PAGE analysis of the expressed and IMAC-purified His6- CD16a-binding polypeptide -ABDWT constructs corresponding to SEQ ID 78 (lane 1), SEQ ID 76 (lane 2), and SEQ ID 77 (lane 3). Lane M, marker proteins with molecular masses in kilodaltons. Figure 3 shows sensorgrams obtained after injection of the three purified hCD16a binding variants His6-A10-ABDWT[SEQ ID 76], His6-H09-ABDWT[SEQ ID 78] and His6- A11-ABDWT [SEQ ID 77] at concentrations ranging from 5 nM to 2.56 μM over sensor chip flow cell surfaces immobilised with hCD16a F158 or hCD16a V158. Figure 4 shows the resulting sensorgrams from the pairwise epitope binding assay using fusion proteins His6-A10-ABDWT[SEQ ID 76], His6-H09-ABDWT[SEQ ID 78] and His6-A11-ABDWT[SEQ ID 77] in competitive binding studies to hCD16a F158 and hCD16a V158. Figure 5 shows an SDS-PAGE analysis of different expressed and IMAC-purified hCD16a-binding constructs His6-A10-Cys [SEQ ID 79] (Lane 1) and His6-A11-Cys [SEQ ID 80] (Lane 2). The larger molecular weight bands visible in lanes 1 and 2 correspond to an expected presence of also dimeric species, held together via a disulfide bond formed between the C-terminal cysteines present in these constructs. Lane M, marker proteins with molecular masses in kilodaltons. Figure 6 shows sensorgrams obtained after injection of hCD16a F158 or hCD16a V158 over immobilised hCD16a monomeric binding variants His6-A10-Cys [SEQ ID 79] and His6-A11-Cys [SEQ ID 80]. Figure 7 shows CD spectra (from before and after heating) and thermal melting curves for CD16a-binding polypeptides A10, H09 and A11 [SEQ ID 1, 74 and 75], all equipped with a C-terminal His6tag. Figure 8 shows sensorgrams obtained after injection of 14 alanine-substituted variants (polypeptide-YY-His6format), at a common concentration of 200 nM), over a sensor chip surface containing CD16a (F158) protein. Figure 9 shows CD spectra (from before and after heating) for 14 alanine-substituted variants (polypeptide-YY-His6format) of CD16a-binding polypeptide A10. Figure 10a shows thermal melting curves for 14 alanine-substituted variants (polypeptide-YY-His6format) of CD16a-binding polypeptide A10. Figure 10b shows the results of binding experiments of a fusion proteins containing the polypeptide with SEQ ID 1 or one of 13 CD16a-binding polypeptide A10 variants in the form of anti-BCMA-A10*-His6fusion proteins containing an A10* polypeptide corresponding to SEQ IDs 11, 12, 15, 17, 18, 19, 25, 29, 43, 49, 51, 53 or 33 (polypeptide-YY-His6 format) with CD16a F158. Figure 10c shows a plot of the respective on-rate (M-1 s-1) and off-rate (s-1) kinetic constants for the compounds analysed in Figure 10b. Figure 11 shows the structures (i.e. the ([N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] sequences) and binding data of example CD16a binding polypeptide functional portions of the invention. Figure 12 shows the structures (i.e. the ([N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] sequences) and binding data of example CD16a binding polypeptides of the invention. Figure 13 shows the sequences of binding motifs (i.e. the [Helix 1]-[Separating portion]-[Helix 2] sequence) of example CD16a binding polypeptide functional portions of the present invention. Figure 14 shows the sequences of binding motifs (i.e. the [Helix 1]-[Separating portion]-[Helix 2] sequence) of example CD16a binding of the present invention. Figure 15 shows (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – SEQ ID NO.1) and one additional functional portion (a BCMA binding moiety, e.g 1-E6, – SEQ ID 226): and (b) a schematic representation of dimeric constructs of the invention comprising one CD16a binding polypeptide (e.g. A10 – SEQ ID NO.1) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID 226). Figures 16 and 17 show (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – SEQ ID NO.1) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID 226); and (b) a schematic representation of trimeric constructs of the invention comprising one CD16a binding polypeptide (e.g. A10 – SEQ ID NO.1) and two additional functional portions (two BCMA binding moieties, e.g.1-E6, – SEQ ID 226). Figure 18 shows (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – SEQ ID NO.1) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID 226); and (b) a schematic representation of trimeric constructs of the invention comprising one CD16a binding polypeptide (e.g.A10 – SEQ ID NO.1) and two additional functional portions ( BCMA binding moieties, e.g.1-E6, – SEQ ID 226). Figure 19 shows (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – SEQ ID NO.1) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID 226); and (b) a schematic representation of multimeric constructs of the invention comprising one or two CD16a binding polypeptide (e.g. A10 – SEQ ID NO.1) and two or more than two additional functional portions ( BCMA binding moieties, e.g.1-E6, – SEQ ID 226). Figure 20 shows the sequence and structure of the hCD16a × hBCMA dual engager dimeric constructs synthesised in Example 10 (aindicates that structure is shown in its non-oxidised form; * indicates that a K residue side chain is modified as shown in the structure to have a linker attached to its side chain). Figure 21 shows the shows the sequence and structure of the hCD16a × hBCMA dual engager trimeric constructs synthesised in Example 11 (* indicates that a K residue side chain is modified as shown in the structure to have a linker attached to its side chain; ∞ indicates that a K residue side chain is modified as shown in the structure to have a linker attached to its side chain and that the K also has an linker attached at its N-terminus). Figure 22 shows the shows the sequence and structure of the hCD16a × hBCMA dual engager multimeric constructs synthesised in Example 11 (* indicates that a K residue side chain is modified as shown in the structure to have a linker attached to its side chain). Figure 23 shows the structures (i.e. the ([hBCMA N-terminal portion]-[Helix 1]-[ hBCMA Separating portion]-[hBCMA Helix 2]-[ hBCMA C-terminal portion] sequences) of hBCMA binding polypeptide functional portions of the present invention. Figure 24 shows the sequences of hBCMA binding motifs (i.e. the [hBCMA Helix 1]- [Separating portion]-[ hBCMA Helix 2] sequence) of example hBCMA binding polypeptide functional portions of the present invention. Figure 25 shows the sequence and structure of the hBCMA peptides, precursors to engager constructs, synthesised in Example 11B and hCD16a × hBCMA dual engager trimeric constructs synthesised in Example 11C; * indicates that a K residue side chain is modified as shown in the structure to have a linker attached to its side chain). Detailed Description The present inventors have found that polypeptides as disclosed herein are effective binders of CD16a and effectively engage immune cells. The polypeptides have been found to trigger strong ADCC responses against cancer cells in an in vitro model. Notably, the inventors have found that such anti-cancer responses compare favourably in the model with those obtained using the monoclonal antibody elotuzumab, which is approved for treatment of multiple myeloma. The polypeptides have also been found to induce strong killing of cancer cells in an in vitro model. The inventors have further found that such anti-cancer responses compare favourably in the model with those obtained using a biosimilar of belantamab mafodotin, which is an antibody-drug conjugate for treatment of multiple myeloma. In its broadest aspect, the invention provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and which further comprises at least one additional functional portion, wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker, wherein the or each linker comprises one or more groups selected from the group consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooxtane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione, wherein n is 1 to 30, wherein m is 1

[0002] The invention also provides CD16a-binding oligomer, which comprises at least two CD16a-binding polypeptides, wherein each CD16a-binding polypeptide comprises at least one motif that binds to CD16a, and wherein each CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and wherein the CD16a-binding polypeptides are each separated by a linker, wherein the or each linker comprises one or more groups selected from the group consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooctane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione, wherein n is 1 to 30, wherein m is 1 and wherein the CD16a-binding oligomer optionally further comprises at least one additional functional portion, wherein the CD16a-binding oligomer and an additional functional portion are separated by a linker, and wherein the or each linker comprises one or more groups selected from the groups consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooctane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione, wherein n is 1 to 30, wherein m is 1 The invention further provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]; wherein the CD16a-binding motif sequence is selected from SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044) of Figure 14. The invention further provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]; wherein the sequence of the CD16a-binding polypeptide is selected from SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) of Figure 12. The various elements of the polypeptides of the invention will now be described in further detail: Overall structure The polypeptides of the present invention may be based on three-helix scaffolds, sometimes referred to as ‘affibodies’. Affibodies are small (around 6.5 kDa) engineered affinity ligands, based on the Z-domain polypeptide, which is a mutated version of the B-domain in the immunoglobulin-binding region of staphylococcal protein A (Nord K et al., Binding proteins selected from combinatorial libraries of an α-helical bacterial receptor domain, Nature Biotech, 1997:15:772, doi: 10.1038 / nbt0897-772). In a full length affibody, the C-terminal portion includes [Second separating portion]-[Helix 3]-[C-terminal sequence]. The general structure of an affibody is shown in Figure 1a. The portions of the molecules of the invention referred to as Helix 1 and Helix 2 (and Helix 3, when present) are generally helical in structure. In some rare embodiments, it can be found that the structure established by the sequence with particular residues can be not strictly helical. Such compounds are to be considered within the broadest aspect of the invention. More preferably, the residues in the Helix 1 and Helix 2 portions do result in those structures being helical, in the sense of being alpha-helical. Sequences of the polypeptides of the invention The sequence of the CD16a-binding polypeptides as disclosed herein may be expressed in terms of their constituent amino acids or in terms of nucleic acid sequences encoding polypeptides having those amino acid sequences. In the context of the present disclosure, the term “amino acid” encompasses any naturally occurring amino acid or unnatural amino acid. The term “unnatural amino acid” as used herein refers to non-proteinogenic (i.e. non-encoded) amino acids, which may either be found in nature or are chemically synthesised (for example citrulline, hydroxyproline, beta-alanine, ornithine, norleucine, 3-nitrotyrosine, pyroglutamic acid, nitroarginine, homoleucine or tert-butylalanine). It includes α, β, γ and δ amino acids. It includes an amino acid in any chiral configuration. The amino acid may, especially, be a naturally occurring α amino acid. The amino acid may, especially, be a naturally occurring L amino acid. The amino acid may, especially, be a naturally occurring L-α amino acid. Within a polypeptide chain (for example a CD16a-binding polypeptide as disclosed herein), the amino acids are linked by peptide bonds between the carboxyl group of one amino acid and the amine group of the next amino acid in the chain. An individual amino acid is called a “residue” or “amino acid residue” once it is linked in a polypeptide chain. The amino acid sequences herein are shown with the N-terminus to the left, and where sequences are set out across multiple lines, the N-terminus is to the top left. Unless indicated otherwise, the amino acid residues in the sequences are L-amino acids. The amino acid sequences listed in the application are shown using standard letter abbreviations for amino acids. The specific sequences given herein relate to specific embodiments of the invention. The present disclosure also includes derivatives of all the sequences described herein (for example, derivatives of each of the CD16a-binding polypeptide and CD16a- binding oligomer sequences described here). Derivatives of the sequences described herein are preferably derivatives wherein from 1 to 5 (for example 1, 2 or 3 amino acid residues) may be replaced by an alternative residue, for example a different naturally occurring amino acid or a different unnatural amino acid; or a different naturally occurring amino acid excluding methionine or a different unnatural amino acid. Preferably, an unnatural amino acid according to the present invention is one that is isosteric with a naturally occurring amino acid, for example norleucine. In one embodiment, an unnatural amino acid according to the present invention is one selected from norleucine, homoleucine and tert-butylalanine For example, in one embodiment, one or more (for example each) methionine residues of the sequences described herein may be replaced by a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine, leucine, glutamine, norleucine, homoleucine and tert-butylalanine (for example isoleucine, leucine, glutamine, and norleucine; or norleucine, homoleucine and tert-butylalanine); and especially isoleucine and norleucine. For example, from 1 to 5 methionine residues, from 1 to 3 methionine residues (for example 1, 2 or 3 methionine residues), or 1 or 2 methionine residues, or 1 methionine residue, when present, may be replaced by a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine, leucine, glutamine, valine, norleucine, homoleucine and tert-butylalanine (for example isoleucine, leucine, glutamine, and norleucine; or norleucine, homoleucine and tert- butylalanine); and especially isoleucine and norleucine. For example, in embodiments wherein X11may be or is methionine, the residue at X11may be replaced by a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine, leucine, glutamine, norleucine, homoleucine and tert-butylalanine; and especially isoleucine and norleucine. For example, in embodiments wherein X35may be or is methionine, the residue at X35may be replaced by a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine, leucine, glutamine, norleucine, homoleucine and tert-butylalanine; and especially isoleucine and norleucine. For example, in embodiments wherein X11and X35may be or are methionine, the residues at X11and X35may be replaced by a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine, leucine, glutamine, norleucine, homoleucine and tert-butylalanine; and especially isoleucine and norleucine. For example, in embodiments wherein X32may be or is methionine, the residue at X32may be replaced by a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine, leucine, glutamine, norleucine, homoleucine and tert-butylalanine; and especially isoleucine and norleucine. Alternatively, or additionally, in certain embodiments, the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may contain amino acid substitutions wherein one or more residues is replaced by an unnatural amino acid. For example, in one embodiment, one or more residues of the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may be replaced by an unnatural amino acid, for example norleucine, homoleucine or tert-butylalanine. For example, from 1 to 15 residues may be replaced by unnatural amino acid(s), for example from 1 to 10 residues (for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 residues), from 1 to 5 residues (for example 1, 2, 3, 4 or 5), from 1 to 3 residues (for example 1, 2, or 3), or 1 residue may be replaced by unnatural amino acid(s) (for example norleucine, homoleucine or tert- butylalanine). For example, in one embodiment, one or more leucine residues of the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may be replaced by an unnatural amino acid, and preferably norleucine. For example, from 1 to 5 leucine residues, from 1 to 3 leucine residues (for example 1, 2 or 3 leucine residues), or 1 or 2 leucine residues, or 1 leucine residue, when present, may be replaced by unnatural amino acid (for example norleucine). For example, in certain embodiments, in the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here), at a position at which a leucine residue is recited, the polypeptide has the sequence with the leucine residue independently substituted for an unnatural amino acid, and preferably norleucine. Alternatively, or additionally, in one embodiment, one or more methionine residues of the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may be replaced by an unnatural amino acid, for example norleucine, homoleucine or tert-butylalanine and preferably norleucine. For example, from 1 to 5 methionine residues, from 1 to 3 methionine residues (for example 1, 2 or 3 methionine residues), or 1 or 2 methionine residues, or 1 methionine residue, when present, may be replaced by unnatural amino acid (for example norleucine). For example, in certain embodiments, in the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here), at a position at which a methionine residue is recited, the polypeptide has the sequence with the methionine residue independently substituted for an unnatural amino acid for example norleucine, homoleucine or tert-butylalanine, and preferably norleucine. For example, in embodiments wherein X11may be or is methionine, the residue at X11may be replaced by an unnatural amino acid(s) (for example norleucine). For example, in embodiments wherein X35may be or is methionine, the residue at X35may be replaced by an unnatural amino acid(s) (for example norleucine). For example, in embodiments wherein X11and X35may be or are methionine, the residues at X11and X35may be replaced by unnatural amino acids (for example norleucine). For example, in embodiments wherein X32may be or is methionine, the residue at X32may be replaced by an unnatural amino acid(s) (for example norleucine). In certain embodiments, one or more methionine residues of the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may be oxidised, for example in the form of methionine sulfoxide (“Met(O)”). For example, from 1 to 5 methionine residues, from 1 to 3 methionine residues (for example 1, 2 or 3 methionine residues), or 1 or 2 methionine residues, or 1 methionine residue, when present, may be oxidised (for example may be Met(O)). For example, in embodiments wherein X11may be or is methionine, when present the methionine at X11may be oxidised (for example Met(O)). For example, in embodiments wherein X35may be or is methionine, when present the methionine may be oxidised (for example Met(O)). For example, in embodiments wherein X11and X35may be or are methionine, when present the methionines at X11and X35may be oxidised (for example Met(O)). For example, in embodiments wherein X32may be or is methionine, when present the methionine may be oxidised (for example Met(O)) Alternatively, or additionally, in certain embodiments, the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) comprise a peptide purification tag or moiety (for example a histidine-tag (for example a polyhistidine tag optionally comprising tyrosine) or a methionine-tag (for example a single methionine tag or a polymethionine tag)), a signalling tag or moiety (for example a glycine residue, or a signal peptide, for example selected from signal peptides of OmpA, DsbA, PhoA, and PelB), a fluorophore tag (for example Alexa448 (AlexaFluorTM488) or Alexa647(AlexaFluorTM)), or a tag or moiety to assist conjugation, a cysteine tag (for example a single cysteine at the C or N terminal)) or a tag to assist in detection in biological samples (for example an alfa, flag or myc-tag). Such tags and / or moieties may, preferably, be present at the N-terminal and / or the C-terminal of the CD16a- binding polypeptide and CD16a-binding oligomer sequences described herein. In an embodiment, the CD16a-binding polypeptides and CD16a-binding oligomers described herein may comprise one or more of the following: a peptide purification tag or moiety (for example a histidine-tag (for example a polyhistidine tag optionally comprising tyrosine) or a biotin tag; a fluorophore tag (for example Alexa448 (AlexaFluorTM488) or Alexa647(AlexaFluorTM)); and a tag to assist in detection in biological samples (for example an alfa tag). Such tags and / or moieties may preferably be present at the N-terminal and / or the C-terminal of the CD16a-binding polypeptide and CD16a-binding oligomer sequences described herein. Therefore, the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may further comprise an additional sequence of at least 1 histidine residue (and optionally at least 1 tyrosine residue) and / or at least 1 methionine residue; for example at least 4, at least 5, or at least 6 histidine residues (and optionally at least 1 tyrosine residue, for example 1, 2 or 3 tyrosine residues) and / or at least 1 methionine residue. In one embodiment, the sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may further comprise an additional sequence of at least 6 histidine residues and optionally at least 1 tyrosine residue (for example 6 histidine residues (e.g. HHHHHH) or 6 histidine residues and two tyrosine residues (e.g. YYHHHHHH)) and / or at least 1 methionine residue (for example 1 or 2 methionine residues). A peptide purification tag or moiety, for example a histidine-tag or a methionine-tag as described above, may preferably be present at the N-terminal and / or the C-terminal of the CD16a- binding polypeptide and CD16a-binding oligomer sequences described herein. For example, an additional sequence of at least 6 histidine residues (for example 6 histidine residues; or 6 histidine residues and two tyrosine residues) and / or at least 1 methionine residue (for example 1 or 2 methionine residues) may be present at the N-terminal and / or the C-terminal of the CD16a-binding polypeptide and CD16a- binding oligomer sequences described herein. The sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may further comprise an additional sequence of at least one cysteine (for example one cysteine) at the N- terminal or the C-terminal. The sequences described herein (for example, the CD16a- binding polypeptide and CD16a-binding oligomer sequences described here) may further comprise a fluorophore tag (for example a 448Alexa tag) at the N-terminal or the C-terminal. The sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may further comprise a signal peptide, for example selected from OmpA, DsbA, PhoA, and PelB, at the the N-terminal or the C-terminal, preferably the N-terminal. The sequences described herein (for example, the CD16a-binding polypeptide and CD16a-binding oligomer sequences described here) may further comprise an additional sequence of at least one glycine (for example one glycine) at the N-terminal or the C-terminal. In certain embodiments, the CD16a-binding polypeptide is one wherein the CD16a binding efficacy is at least 1%, at least 5%, or preferably at least 10% (more preferably at least 15%, 20% 25% or 50%) of SEQ ID NO: 1, 74 or 75. When a CD16a- binding polypeptide is described herein as having CD16a binding efficacy that is at least X% of a specific peptide (e.g. SEQ IS NO: 1, 74 or 75), it is understood that the IC50concentration of the polypeptide for binding to the CD16a receptor is no more than 100 / X times the IC50concentration for the specific peptide (SEQ ID NO: 1, 74 or 75) to the CD16a receptor, when measured under the same conditions. For example, if the binding efficacy of a CD16a-binding polypeptide is at least 5%, and more preferably at least 10%, 20%, 25% or 50% of the CD16a binding efficacy of the specific peptide (e.g. SEQ ID NO: 1, 74 or 75), that is to say that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 20 times and more preferably 10 times, 5 times, 4 times or 2 times, respectively, the IC50concentration for the specific peptide (e.g. SEQ ID NO: 1, 74 or 75) to the CD16a receptor, when measured under the same conditions. In certain embodiments, alternatively, or additionally, the CD16a-binding polypeptide is one that competes with SEQ ID NO: 1, 74 and / or 75. The CD16a-binding polypeptides of the present invention have binding affinity for the CD16a receptor; and may optionally have binding affinity for the CD16b receptor. For example, in certain embodiments the CD16a-binding polypeptides of the present invention have similar binding affinity for the CD16a receptor and CD16b receptor; in certain embodiments, the CD16a-binding polypeptides of the present invention have stronger binding affinity for the CD16a receptor than the CD16b receptor and in certain embodiments, the CD16a-binding polypeptides of the present invention have stronger binding affinity for the CD16b receptor than the CD16a receptor. The CD16a-binding polypeptides of the present invention may have binding affinity to one or both genotypic variation of the CD16a (FcγRIIIa) receptor: the FcγRIIIa- 176V / F polymorphism (rs396991) (in some publications where the leader sequence is excluded, position 176 is reported as position 158 and this numbering is also used in the Examples herein). Preferably, the CD16a-binding polypeptides of the present invention have binding affinity for both genotypic variation of the CD16a (FcγRIIIa) receptor: the FcγRIIIa-176V / F polymorphism (rs396991). In certain embodiments, the CD16a-binding polypeptides of the present invention have a stronger binding affinity for the valine (V) position 176 phenotype, or have a stronger binding affinity for the phenylalanine (F) position 176 phenotype, or have similar binding at both the F and the V position 176 phenotype. The present invention provides a CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]. Preferably, Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, a) X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11 is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q, or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17 is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, M, R or S; or b) X9is V; X10is Q; X11is M; X13is Q; X14is F; X17is R; X18is K; X24is H; X25is H; X27is S; X28is F; X31is I; X32is K; X33is S and X35is M, and optionally wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example at least 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue; or c) X9is Q; X10is F; X11is Y; X13is R; X14is D; X17is D; X18is L; X24is E; X25is D; X27is K; X28is W; X31is Y; X32is M; X33is S and X35is I, and optionally wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example at least 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue; or d) X9is F; X10is W; X11is I; X13is E; X14is S; X17is E; X18is S; X24is I; X25is Y; X27is K; X28is W; X31is K; X32is Y; X33is S and X35is A, and optionally wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example at least 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue. In certain embodiments, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y;X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, M R or S. In a further embodiment, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R or Q; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is H or A; X27is A, I, K, Q, R, T, S or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, M, R or S. In a further embodiment, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R; X18is A, D, E, F, H, K, N, Q, R, S, T or V; X24is H; X25is H; X27is A, I, K, Q, R, T, S or V; X28is F or Y; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is A, H, I, L, M, R or S. In a further embodiment, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R or Q; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is H or A; X27 is A, I, K, Q, R, T or V; X28 is F or Y; X31 is I or L; X32 is A, E, H, K, L, N, Q or R; X33 is K or S; and X35is A, H, I, L, R or S. In a further embodiment, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R; X18is A, D, E, F, H, K, N, Q, R, S, T or V; X24is H; X25is H; X27is A, I, K, Q, R, T, or V; X28is F or Y; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has a fast binding or “on” rate for the CD16a receptor. For example, the CD16a- binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q;X11is A, D, E, F, H, I, K, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is H, I, K, L, N, Q, R, S, V, W or Y; X17is R; X18is A, D, E, F, H, K, N, Q, R, S or T; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is H, I, L, R or S. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has a slow dissociation rate or “off” rate for the CD16a receptor. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A or Q; X14is H, I, K, L, Q, R, S, T, V, W or Y; X17is R; X18is A, D, E, F, H, K, N, Q, R, S, T or V; X24is H;X25is H; X27is A, I, K, Q, R, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is A, H, I, L or R. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has a high binding affinity for the CD16a receptor, for example a KDfor the CD16a receptor of less than 250 nM. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18 and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y X10is Q; X11is A, D, E, F, H, I, K, N, Q, R, S, T, V, W or Y; X13is A or Q; X14is H, I, K, L, Q, R, S, V, W or Y; X17is R; X18is A, F, H, K, N, Q, R, S or T; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F or Y; X31is I or L; X32is E, H, K, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S. In certain preferred embodiments, the CD16a-binding polypeptide of the invention have an especially fast binding or “on” rate for the CD16a receptor. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is F, L, Q, T or Y; X10is Q; X11is A, F, H, I, L, N, Q, S, or Y; X13is A or Q; X14is I, K, Q, R or V; X17is R; X18is A, E, H, K, Q, R, T or V; X24is H; X25is H; X27is A, I, K, Q, R or V; X28is F; X31is I; X32is A, H, K, N, Q or R; X33is K or S; and X35is H, I or L. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has an especially slow dissociation rate or “off” rate for the CD16a receptor. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is I, L, Q, T or V; X10is Q; X11is A, E, F, H, I, S, V or Y; X13is Q; X14is K, L, R, V, W or Y; X17is R; X18is A, H, K, Q, R, S or T; X24is H; X25is H; X27is I, K, Q, R, T or V; X28is F; X31is I or L; X32is K, N or R; X33is K or S; and X35is I or L. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has an especially high binding affinity for the CD16a receptor, for example a KDfor the CD16a receptor of less than 100 nM. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is I, L, Q or V; X10is Q; X11is A, E, H, I, S, W or Y; X13is Q; X14is K, L, R, V, W or Y; X17is R; X18is A, H, K, Q, R, S, or T; X24is H; X25is H; X27is K, Q, R, T or V; X28is F; X31is I; X32is K, N or R; X33is K or S; and X35is I or L. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has at least two of the following: a fast binding or “on” rate for the CD16a receptor; and / or a slow dissociation rate or “off” rate for the CD16a receptor; and / or a high binding affinity for the CD16a receptor, for example a KDfor the CD16a receptor of less than 100 nM. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is I, L, Q or V; X10is Q; X11is A, E, H, I, S or Y; X13is Q; X14is K, L, R, V, W or Y; X17is R; X18is H, K, Q, R, S or T; X24is H;X25is H; X27is K, Q, R, T or V; X28is F; X31is I; X32is N or K; X33is K or S; and X35is I or L. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has an especially slow dissociation rate or “off” rate for the CD16a receptor and has a high binding affinity for the CD16a receptor, for example a KDfor the CD16a receptor of less than 100 nM. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L or V; X10is Q; X11is A, I, S or Y; X13is Q; X14is K, R or V; X17is R; X18is K, Q, R, S or T; X24is H; X25is H; X27is K, R or V; X28is F; X31is I; X32is N or K; X33is K or S; and X35is I or L. In certain preferred embodiments, the CD16a-binding polypeptide of the invention binds the CD16a and CD16b receptor. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, H, I, K, L, Q, T or V; X10is Q; X11is A, D, E, F, H, I, K, N, R, S, V, W or Y; X13is Q; X14is K, L, Q, R, S, V, W or Y; X17is R; X18is A, H, K, N, Q, R, S or T; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is A, I, L, or R. In certain preferred embodiments, the CD16a-binding polypeptide of the invention has a binding preference for the CD16a receptor compared to the CD16b receptor. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is K, Q or Y; X10is Q; X11is I or Q; X13is Q; X14is W or Y; X17is R; X18is H, K or R; X24is H; X25is H; X27is A, K or T; X28is F; X31is I; X32is A, K or Q; X33is K or S; and X35is I or L; In certain preferred embodiments, the CD16a-binding polypeptide of the invention has a binding preference for the CD16b receptor compared to the CD16a receptor. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L, V or Y; X10is Q; X11is I, N or Q; X13is Q; X14is K, R or Q; X17is R; X18is E, A or V; X24is H; X25is H; X27is K or Q; X28is F; X31is I; X32is H, K or Q; X33is K or S; and X35is I or L. In certain very preferred embodiments, the CD16a-binding polypeptide of the invention, is especially active in functional assays, e.g. a CD16 reporter assay and / or a cell killing assay. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L, Q, T or V; X10is Q; X11is I, V or Y; X13is Q; X14is K, R or Y; X17is R; X18is K, R, S or T; X24is H; X25is H; X27is I, T or V; X28is F; X31is I or L; X32is K or N; X33is K or S; and X35is I or L. In certain especially preferred embodiments, the CD16a-binding polypeptide of the invention, is very especially active in functional assays, e.g. a CD16 reporter assay and / or a cell killing assay. For example. For example, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L, T or V; X10is Q; X11is I, V or Y; X13is Q;X14is K or R; X17is R; X18is R, S or T; X24is H; X25is H; X27is I or V; X28is F; X31is I or L; X32is K or N; X33is K; and X35is I or L. In certain preferred embodiments, the CD16a-binding polypeptide of the invention is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32 X33LX35, wherein, X9 is L, Q or V; X10 is Q; X11is H, I, M, N or Y (preferably H, I, N or Y); X13is Q; X14is F, K, R or Y; X17is R; X18is A, K, Q, R or S; X24is H; X25is H; X27is Q, S, T or V; X28is F; X31is I; X32is A, H, K or N; X33is K or S; and X35is I, L or M. In another very preferred embodiment the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L, Q or V; X10is Q; X11is I, M, N or Y (preferably I, N or Y); X13is Q; X14is F, K, R or Y; X17is R; X18is A, K, R or S; X24is H; X25is H; X27is Q, S, T or V; X28is F; X31is I; X32is H, K or N; X33is K or S; and X35is I, L or M. In another very preferred embodiment the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L, Q or V; X10is Q; X11is I, M, N or Y (preferably I, N or Y); X13is Q; X14is F, K, R or Y; X17is R; X18is R; X24is H; X25is H; X27is Q, S, T or V; X28is F; X31is I; X32is H, K or N; X33is K or S; and X35is I, L or M. In another very especially preferred embodiment, the CD16a-binding polypeptide is one wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is L, Q or V; X10is Q; X11is I, M or N (preferably I or N); X13is Q; X14is F, R or Y; X17is R; X18is A, K or R; X24is H; X25is H; X27is Q, S, or T; X28is F; X31is I; X32is H or K; X33is K or S; and X35is I, L or M. In certain embodiments of the present invention, the CD16a-binding polypeptide is one that has a R at position X18. In certain embodiments of the present invention, the CD16a-binding polypeptide is one that does not have a methionine residue at position X11or at X35, for example a CD16a-binding polypeptide wherein: Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18 and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein: X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y or an unnatural amino acid (for example norleucine); X13is A, Q, or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R, S or an unnatural amino acid (for example norleucine); or X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W, Y, isoleucine, leucine, glutamine, or norleucine (for example A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W, Y, isoleucine or norleucine); X13is A, Q, or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W, or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T, or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R, S, isoleucine, leucine, glutamine, or norleucine (for example, A, H, I, L, R, S, isoleucine or norleucine ); or X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A, Q, or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S. In a further embodiment, that does not have a methionine residue at position X11or at X35, a CD16a-binding polypeptide the CD16a-binding polypeptide is one wherein: Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W Y or an unnatural amino acid (for example norleucine); X13is A, Q or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T, or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R, S or an unnatural amino acid (for example norleucine); or X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W, Y, isoleucine, leucine, glutamine, or norleucine (for example A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W, Y, isoleucine or norleucine); X13is A, Q or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W, or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, , or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q, or R; X33is K or S; and X35is A, H, I, L, R, S, isoleucine, leucine, glutamine, or norleucine (for example, A, H, I, L, R, S, isoleucine or norleucine); or X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S In a further embodiment, that does not have a methionine residue at position X11or at X35, a CD16a-binding polypeptide the CD16a-binding polypeptide is one wherein: Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, wherein, X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W, Y or an unnatural amino acid (for example norleucine); X13is A, Q or V; X14is F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R or Q; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is H or A; X27is A, I, K, Q, R, T, S or V; X28is F or Y;X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R, S or an unnatural amino acid (for example norleucine) ; or X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W Y, isoleucine, leucine, glutamine, or norleucine (for example A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W Y, isoleucine or norleucine); X13is A, Q or V; X14is F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17 is R or Q; X18 is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24 is H; X25 is H or A; X27is A, I, K, Q, R, T, S or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R S, isoleucine, leucine, glutamine, or norleucine (for example A, H, I, L, R, S, isoleucine or norleucine); or X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R or Q; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is H or A; X27is A, I, K, Q, R, T, S or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S. In certain embodiments, the CD16a-binding polypeptide is one wherein the CD16a binding efficacy is at least 1%, at least 5%, or preferably at least 10% (more preferably at least 15%, 20% 25% or 50%) of SEQ ID NO: 1 (i.e. binding efficacy of the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions). Preferably, the CD16a-binding polypeptide is one wherein the CD16a binding efficacy is at least 10% of SEQ ID NO: 1. In certain embodiments, alternatively, or additionally, the CD16a-binding polypeptide is one that competes with SEQ ID NO: 1. In advantageous embodiments of CD16a-binding polypeptides of the invention, Proline (P) and Cysteine (C) are not present in Helix 1 or Helix 2 of a CD16a binding polypeptide of the present invention. Advantageously Glycine (G) is also not present in Helix 1 or Helix 2 of a CD16a binding polypeptide of the present invention. In certain embodiments, a CD16a-binding polypeptide of the invention is one wherein: Helix 1 comprises the sequence X6X7X8X9X10X11AX13X14EIX17X18X19and / or Helix 2 comprises the sequence X23X24X25QX27X28AFX31X32X33LX35X36X37, wherein, X6is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N) or is absent (for example X6is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N)); X7is any naturally occurring amino acid (preferably H, K or R; more preferably K) or is absent (for example X7is any naturally occurring amino acid (preferably H, K or R; more preferably K)); X8 is any naturally occurring amino acid (preferably D, E, N or Q; more preferably E) or is absent (for example X8is any naturally occurring amino acid (preferably D, E, N or Q; more preferably E)); X19 is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably L) or is absent (for example X19is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably L)); X23is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N) or is absent (for example X23is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N); X36is any naturally occurring amino acid (preferably D, E, N or Q; more preferably D) or is absent (for example X36is any naturally occurring amino acid (preferably D, E, N or Q; more preferably D)); and X37is any naturally occurring amino acid (preferably D, E, N or Q; more preferably D) or is absent (for example X37is naturally occurring amino acid (preferably D, E, N or Q; more preferably D)). In certain embodiments, a CD16a-binding polypeptide of the invention is one wherein: Helix 1 comprises the sequence X6X7X8X9X10X11AX13X14EIX17X18X19and / or Helix 2 comprises the sequence X23X24X25QX27X28AFX31X32X33LX35X36X37, wherein, X6is D, E, N or Q (more preferably N) or is absent (for example X6is D, E, N or Q, and more preferably N); X7is H, K or R (preferably K) or is absent (for example X7is H, K or R; and more preferably K); X8is D, E, N or Q (preferably E) or is absent (for example X8is D, E, N or Q; and more preferably E); X19is G, A, V, L or I (preferably L) or is absent (for example X19is G, A, V, L or I; and more preferably L); X23is D, E, N or Q (preferably N) or is absent (for example X23is D, E, N or Q; and more preferably N); X36is D, E, N or Q more preferably D) or is absent (for example X36is D, E, N or Q; and more preferably D); and X37is D, E, N or Q (preferably D) or is absent (for example X37is D, E, N or Q; and more preferably D). In certain embodiments of the present invention, such as the embodiments described above: Helix 1 comprises the sequence X6X7X8X9X10X11AX13X14EIX17X18X19and / or Helix 2 comprises the sequence X23X24X25QX27X28AFX31X32X33LX35X36X37. In such embodiments, X6may be any naturally occurring amino acid or is absent; X7may be any naturally occurring amino acid or is absent; X8may be any naturally occurring amino acid or is absent; X19 may be any naturally occurring amino acid or is absent; X23may be any naturally occurring amino acid or is absent; X36may be any naturally occurring amino acid or is absent; and X37may be any naturally occurring amino or is absent. More preferably, X6may be any naturally occurring amino acid; X7may be any naturally occurring amino acid; X8may be any naturally occurring amino acid; X19may be any naturally occurring amino acid; X23may be any naturally occurring amino acid; X36may be any naturally occurring amino acid; and X37may be any naturally occurring amino. In another preferred embodiment, X6may be D, E, N, Q or is absent; X7may be H, K, R or is absent; X8may be any D, E, N, Q or is absent; X19may be G, A, V, L, I or is absent; X23may G, A, V, L, I or is absent; X36may be G, A, V, L, I or is absent; and X37may G, A, V, L, I or is absent. More preferably, X8may be E or is absent; X19may be L or is absent; X23may be D or is absent; X36may be D or is absent; and X37may be D or is absent. In an even more preferred embodiment, X6may be D, E, N or Q; X7may be H, K or R; X8may be any D, E, N or Q; X19may be G, A, V, L or I; X23may G, A, V, L, or I; X36may be G, A, V, L or I; and X37may G, A, V, L or I. In another preferred embodiment, X6may be N or is absent; X7may be K or is absent; X8may be E or is absent; X19may be L or is absent; X23may be D or is absent; X36may be D or is absent; and X37may be D or is absent. In an especially preferred embodiment, X6is N; X7is K; and X8is E. In another especially preferred embodiment, X36is D; and X37is D. In a very especially preferred embodiment, X6is N; X7is K; X8is E; X19is L; X23is D; X36is D; and X37is D. In such embodiments, Helix 1 comprises the sequence NKEX9X10X11AX13X14EIX17X18L and / or Helix 2 comprises the sequence DX24X25QX27X28AFX31X32X33LX35DD. In one embodiment, the CD16a-binding polypeptide is one wherein: Helix 1 comprises the sequence NKEVQMAQFEIRKL and Helix 2 comprises the sequence NHHQSFAFIKSLMDD; and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example, at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement). In certain embodiments, such a CD16a-binding polypeptide has a CD16a binding efficacy of at least 1%, at least 5%, or at least 10% (for example at least 15%, 20% 25% or 50%) of SEQ ID NO: 1. Preferably, such a CD16a-binding polypeptide has a CD16a binding efficacy that is at least 10% of SEQ ID NO: 1. In certain embodiments, alternatively, or additionally, such a CD16a-binding polypeptide is one that competes with SEQ ID NO: 1. In one embodiment, the CD16a-binding polypeptide is one wherein: Helix 1 comprises the sequence NKEQFYARDEIDLL and Helix 2 comprises the sequence NEDQKWAFYMSLIDD; and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example, at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement). In certain embodiments, such a CD16a-binding polypeptide has a CD16a binding efficacy of at least 1%, at least 5%, or at least 10% (for example at least 15%, 20% 25% or 50%) of SEQ ID NO: 74. Preferably, such a CD16a-binding polypeptide has a CD16a binding efficacy that is at least 10% of SEQ ID NO: 74. In certain embodiments, alternatively, or additionally, such a CD16a-binding polypeptide is one that competes with SEQ ID NO: 74. In one embodiment, the CD16a-binding polypeptide is one wherein: Helix 1 comprises the sequence NKEFWIAESEIESL and Helix 2 comprises the sequence NIYQKWAFKYSLADD; and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example, at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement). In certain embodiments, such a CD16a-binding polypeptide has a CD16a binding efficacy of at least 1%, at least 5%, or at least 10% (for example at least 15%, 20% 25% or 50%) of SEQ ID NO: 75. Preferably, such a CD16a-binding polypeptide has a CD16a binding efficacy that is at least 10% of SEQ ID NO: 75. In certain embodiments, alternatively, or additionally, such a CD16a-binding polypeptide is one that competes with SEQ ID NO: 75. In one embodiment the CD16a binding motif, being the portion [Helix 1]-[Separating portion]-[Helix 2], is (i.e. has a sequence): X6X7X8X9X10X11AX13X14EIX17X18X19X20X21X22X23X24X25QX27X28AFX31X32X33LX35X36X37wherein X20is any naturally occurring amino acid, X21is any naturally occurring amino acid; and X22is any naturally occurring amino acid, and wherein optionally one or two (for example, optionally 1) of X20, X21or X22are absent; and the other residues are as defined above. More preferably, X6may be D, E, N, Q or is absent; X7may be H, K, R or is absent; X8may be any D, E, N, Q or is absent; X9, X10, X11, X13, X14, X17and X18are as defined above; X19may be G, A, V, L, I or is absent; X20may be S, T, M, P, F, Y or W (for example P or T); X21may be D, E, N or Q; X22may be G, A, V, L, I or is absent; X23may G, A, V, L, I or is absent; X36may be G, A, V, L, I or is absent; and X37may G, A, V, L, I or is absent; and wherein optionally one or two (for example optionally 1) of X20, X21, X22 are absent. Preferably, X6may be D, E, N or Q; X7may be H, K or R; X8may be any D, E, N or Q; X9, X10, X11, X13, X14, X17and X18are as defined above; X19may be G, A, V, L or I; X20may S, T, M, P, F, Y or W (for example P or T); X21 may be D, E, N or Q; and X22 may be G, A, V, L, or I; X23may G, A, V, L or I; X36may be G, A, V, L or I; and X37may G, A, V, L or I; and wherein optionally one or two (for example optionally 1) of X20, X21, X22are absent. For example, X6may be D, E, N or Q; X7may be H, K or R; X8may be any D, E, N or Q; X9, X10, X11, X13, X14, X17and X18are as defined above; X19may be G, A, V, L or I; X20may be S, T, M, P, F, Y or W (for example P or T); X21may be D, E, N or Q; and X22may be G, A, V, L, or I; X23may G, A, V, L or I; X36may be G, A, V, L or I; and X37may G, A, V, L or I. More preferably, X8may be E or is absent; X9, X10, X11, X13, X14, X17and X18are as defined above; X19may be L or is absent; X23may be D or is absent; X24, X25, X27, X28, X31, X32, X33and X35are as defined above, and X36may be D or is absent; and X37may be D or is absent. In an especially preferred embodiment, X6is N; X7is K; X8is E; X9, X10, X11, X13, X14, X17and X18are as defined above; X19is L; X20is S, T, M, P, F, Y or W (for example P or T), X21is D, E, N or Q (for example N); and X22is G, A, V, L or, I (for example L); X23is D; X36is D; and X37is D. Even more preferably, X6is N; X7is K; X8is E; X9, X10, X11, X13, X14, X17and X18are as defined above; X19is L; X20is P or T; X21is N; and X22is L; X23is D; X36is D; and X37is D. For example, the CD16a binding motif is selected from the group consisting of SEQ ID Nos.150 to 221 (as shown in Figure 13) and SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044) (as shown in Figure 14). For example, the CD16a binding motif is selected from the group consisting of: Or is selected from the group consisting of: In one embodiment, the CD16a binding motif is selected from the group consisting of:

[0003] In one embodiment, the CD16a binding motif is selected from the group consisting of:

[0004] In another embodiment, the CD16a binding motif is selected from the group consisting of: In one very preferred embodiment, the CD16a binding motif is selected from the group consisting of:

[0005] In a polypeptide of Figure 13, Figure 14 and the tables above, the N-terminus of Helix 1 may further comprise the sequence X6X7X8; wherein X6,X7and X8are as defined above, and preferably are NKE (i.e. X6is N; X7is K; X8is E). In a polypeptide of Figure 13, Figure 14, and the tables above, the C-terminus of Helix 2 may further comprise the sequence X36X37; wherein X36and X37are as defined above, and preferably are DD i.e. X36is D; and X37is D). In a polypeptide of Figure 13, Figure 14, and the tables above, optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue. Preferably, in embodiments wherein optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue, the replacement residue is a conservative replacement. In a preferred embodiment, the sequence is the one of SEQ ID 166, 168, 178, 182, or 202 (i.e. as found in one of SEQ ID NO.s / Example Compounds 17, 19, 29, 33, and 53) (and optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue, the replacement residue is a conservative replacement). In another preferred embodiment, the sequence is the one of SEQ ID No.164, 166, 168, or 200, or SEQ ID No.164, 166 or 168 (i.e. as found in one of SEQ ID NO.s / Example Compounds 15, 17, 19, 51, or as found in one of SEQ ID NO.s / Example Compounds 15, 17, 19 ) (and optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue, the replacement residue is a conservative replacement). In another preferred embodiment, the sequence is the one of SEQ ID 150, 184 and 200 (and optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue, the replacement residue is a conservative replacement). In another preferred embodiment, the sequence is the one of SEQ ID 166, 168, 200, or 259 (Motif ID 1014) (and optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue, the replacement residue is a conservative replacement). In another preferred embodiment, the sequence is the one of SEQ ID 166, 168, 200, or 259 (Motif ID 1014) (and optionally from 1 to 5 residues (for example 1, 2, 3, 4 or 5), preferably 1, 2 or 3 residues, in the sequence are replaced by an alternative residue, the replacement residue is a conservative replacement). In preferred embodiments, the motif sequence additionally has the residues NKE at positions X6X7X8(i.e. X6is N; X7is K; X8is E). In preferred embodiments, the motif sequence additionally has the residues DD at its positions X36X37(i.e. X36is D; and X37is D). For example, the motif sequences have NKE at positions X6X7X8and DD at positions X36X37(i.e. X6is N; X7is K; X8is E; X36is D; and X37is D). Therefore, in preferred embodiments, the motif sequence may be selected from: NKEX9X10X11AX13X14EIX17X18X19X20X21X22X23X24X25QX27X28AFX31X32X33LX35X36X37; X6X7X8X9X10X11AX13X14EIX17X18X19X20X21X22X23X24X25QX27X28AFX31X32X33LX35DD; and NKEX9X10X11AX13X14EIX17X18X19X20X21X22X23X24X25QX27X28AFX31X32X33LX35DD. As mentioned above, in embodiments of the invention a number of residues may each be substituted by an alternative residue, as described herein. For example, in the embodiments described above, even when not explicitly mentioned, optionally 1 to 5 (for example 1, 2, 3, 4 or 5), and preferably optionally 1 to 3 (for example 1, 2, or 3), residues in the sequence of Helix 1 and / or Helix 2 defined above are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement). In any such alternative polypeptides of the invention with alternative residues in place, binding to the CD16a receptor is maintained. For example, the CD16a binding efficacy is at least 1% of the binding efficacy of the peptide of SEQ ID NO: 1 (i.e. binding efficacy of the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions (as described above)). Alternatively, or additionally, for example, in any such alternative polypeptides of the invention with alternative residues in place, the CD16a-binding polypeptide is one that competes with SEQ ID NO: 1. In certain preferred embodiments, the binding efficacy is at least 5%, and more preferably at least 10%, 20%, 25% or 50% of the binding efficacy of the peptide of SEQ ID NO: 1 (i.e. binding efficacy of the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions). In advantageous embodiments of CD16a-binding polypeptides of the invention, Proline (P) and Cysteine (C) are not present in CD16a binding motif of a CD16a binding polypeptide of the present invention. Advantageously Glycine (G) is also not present in the CD16a binding motif of a CD16a binding polypeptide of the present invention. In certain embodiments of the invention, the CD16a-binding polypeptide is one wherein: i) Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 has the sequence X24X25QX27X28AFX31X32SLX35, wherein, a*) X9is V; X10is Q; X11is M; X13is Q; X14is F; X17is R; X18is K; X24is H; X25is H; X27is S; X28is F; X31is I; X32is K; and X35is M; b*) X9is Q; X10is F; X11is Y; X13is R; X14is D; X17is D; X18is L; X24is E; X25is D; X27is K; X28is W; X31is Y; X32is M; and X35is I; or c*) X9is F; X10is W; X11is I; X13is E; X14is S; X17is E; X18is S; X24is I; X25is Y; X27is K; X28is W; X31is K; X32is Y; and X35is A; or ii) Helix 1 and Helix 2 are defined as in i), wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example, at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example, at least 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue. In another embodiment, a*) X9is V; X10is Q; X11is I or norleucine; X13is Q; X14is F; X17is R; X18is K; X24is H; X25is H; X27is S; X28is F; X31is I; X32is K; and X35is I or norleucine; In an embodiment, Helix 1 comprises the sequence KEX9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32SLX35D, for example Helix 1 comprises the sequence NKEX9X10X11AX13X14EIX17X18L and Helix 2 comprises the sequence NX24X25QX27X28AFX31X32SLX35DD. As mentioned above, full identity with the sequences set out for (i) is not required (though in one preferred embodiment of the invention, the peptide does have the exact recited sequence). Of the residues denoted with an Xnlabel, in certain embodiments, at least 1 and no more than 8 of the residues may be replaced with an alternative residue. The replaced residues may be in Helix 1 or in Helix 2, or there may be 1 or more replaced residues in each of Helix 1 and Helix 2 (for example, there may be replaced residue in one of them and 1 or 2 replaced residues in the other). For example, there may be 1, 2, 3, 4, 5, 6, 7 or 8 (for example 1, 2, 3, 4 or 5, or 1, 2 or 3) replaced residues in the residues denoted with an Xnlabel, for example 1, 2, 3, 4 or 5, for example 1 or 2, or 1. As there are 15 residues with an Xnlabel, a peptide with 5 residues replaced has 67% sequence identity with the recited sequence. For replacement of 3 residues, it is 80% and for replacement of 1 residue it is 93% sequence identity. For replacement of 2 residues, it is 87% and for replacement of 1 residue it is 93% sequence identity. In an embodiment in which there are 14 residues with an Xnlabel, a peptide with 5 residues replaced has 64% sequence identity with the recited sequence. For replacement of 3 residues, it is 79% and for replacement of 1 residue it is 93% sequence identity.For replacement of 2 residues, it is 86% and for replacement of 1 residue it is 93% sequence identity. Of the residues not labelled as an Xnresidue, at least 1 and no more than 5 of the residues may be replaced with an alternative residue. Preferably, at least 1 and no more than 3 of the residues may be replaced with an alternative residue. The replaced residues may be in either Helix 1 or in Helix 2, or there may be 1 or more replaced residues in each of Helix 1 and Helix 2 (for example there may be replaced residue in one of them and 1 or 2 replaced residues in the other). For example, there may be 1, 2 or 3 replaced residues in the residues not denoted with an Xnlabel, particularly 1 or 2, for example 1. As there are 8 residues without an Xnlabel, a peptide with 3 residues replaced has 63% sequence identity with the recited sequence. For replacement of 2 residues, it is 75% and for replacement of 1 residue it is 88% sequence identity. In an embodiment, the total number of residues in the Helix 1 and Helix 2 portions that are replaced is at least 1 and no more than 11, (for example no more than 10, for example no more than 9, for example no more than 8, for example no more than 7), for example at least 1 and no more than 6, for example at least 1 and no more than 5, at least 1 and no more than 4, for example at least 1 and no more than 3, for example 1 at least 1 and no more than 2. Particularly, there may be 1, 2, 3, 4, 5 or 6 replacement residues in total in those portions. For example, an amino acid residue replacement for a residue denoted as Xnor a residue not denoted as Xnmay be a conservative replacement. That is to say that a residue is replaced with another residue in the same class, for example: An aliphatic residue (Glycine (G), Alanine (A), Valine (V), Leucine (L) or Isoleucine (I)) may be replaced with another aliphatic residue. A hydroxyl-, sulphur- or selenium- containing residue (Serine (S), Cysteine (C), Selenocysteine (U), Threonine (T) or Methionine (M)) may be replaced with another hydroxyl-, sulphur- or selenium- containing residue. An aromatic residue (Phenylalanine (F), Tyrosine (Y) or Tryptophan (W)) may be replaced with another aromatic residue. A basic residue (Histidine (H), Lysine (K), Arginine (R)) may be replaced with another basic residue. An acidic residue or amide (Aspartate (D), Glutamate (E), Asparagine (N), Glutamine (Q)) may be replaced with another acidic residue or amide. Alternatively, an amino acid residue replacement for a residue denoted as Xnor a residue not denoted as Xnmay be a non-conservative replacement, i.e. a residue is replaced with another residue in a different class, for example an aliphatic residue (Glycine (G), Alanine (A), Valine (V), Leucine (L) or Isoleucine (I)) may be replaced with an aromatic residue (Phenylalanine (F), Tyrosine (Y) or Tryptophan (W)), or for example replaced by an amino acid with opposite characteristics, for example replacement of a Lysine (K) residue with an Aspartic acid (D) residue. In one embodiment, the CD16a-binding polypeptide is one wherein: a*) Helix 1 comprises the sequence VQMAQFEIRK (SEQ ID No 230) and Helix 2 comprises the sequence HHQSFAFIKSLM (SEQ ID No 231). For example, Helix 1 comprises the sequence NKEVQMAQFEIRKL (SEQ ID No 232) and Helix 2 comprises the sequence NHHQSFAFIKSLMDD (SEQ ID No 233). In such embodiments, optionally at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement); In a further embodiment, the CD16a-binding polypeptide is one wherein: b*) Helix 1 comprises the sequence QFYARDEIDL (SEQ ID No 234) and Helix 2 comprises the sequence EDQKWAFYMSLI (SEQ ID No 235). For example, Helix 1 comprises the sequence NKEQFYARDEIDLL (SEQ ID No 236) and Helix 2 comprises the sequence NEDQKWAFYMSLIDD (SEQ ID No 237). In such embodiments, optionally at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement); In a further embodiment, the CD16a-binding polypeptide is one wherein: c*) Helix 1 comprises the sequence FWIAESEIES (SEQ ID No 238)and Helix 2 comprises the sequence IYQKWAFKYSLA (SEQ ID No 239). For example, Helix 1 comprises the sequence NKEFWIAESEIESL(SEQ ID No 240) and Helix 2 comprises the sequence NIYQKWAFKYSLADD (SEQ ID No 241). In such embodiments, optionally at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5; or for example at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement); As discussed above, a number of residues may each be substituted by an alternative residue. The CD16a-binding polypeptide of the invention has the overall structure [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]. The separating portion may be a sequence of from 1 to 5 (for example 1, 2, 3, 4 or 5) naturally occurring amino acids. Preferably, the separating portion is a sequence of from 2 to 5 (for example 2, 3, 4 or 5) naturally occurring amino acids. For example, the separating portion is a sequence of from 3 to 5 (for example 3, 4 or 5) naturally occurring amino acids. Preferably the separating portion is a sequence of 3 amino acids. In certain embodiments, the separating portion has the sequence X20X21X22, wherein X20is any naturally occurring amino acid, X21is any naturally occurring amino acid; and X22is any naturally occurring amino acid; and wherein optionally one or two of X20, X21or X22are absent. For example, none of X20, X21or X22is absent, one of X20, X21or X22is absent, or two of X20, X21or X22are absent. More preferably, none of X20, X21or X22is absent or one of X20, X21or X22is absent. Most preferably none of X20, X21or X22is absent, i.e. the separating portion has the sequence X20X21X22, wherein X20is any naturally occurring amino acid, X21is any naturally occurring amino acid; and X22is any naturally occurring amino acid. Preferably, X20is S, T, M, P, F, Y or W (for example P or T); X21is D, E, N or Q; and X22is G, A, V, L or I; wherein optionally one or two (for example one) of X20, X21or X22are absent. In preferred embodiments, X20is S, T, M, P, F, Y or W (for example P or T), X21is D, E, N or Q; and X22is G, A, V, L, I. More preferably, X20is P or T; X21is N; and X22is L. For example, the separating portion has the sequence PNL or TNL. The N-terminal portion may be absent or may be a sequence of 1 to 15 naturally occurring amino acids. For example, the N-terminal portion may be absent or may be a sequence of from 1 to 10, from 1 to 8, from 1 to 6, or from 1 to 5 naturally occurring amino acids, for example 1, 2, 3, 4 or 5 naturally occurring amino acids. In certain embodiments, the N-terminal portion has the sequence X1X2X3X4X5, wherein X1is any naturally occurring amino acid or is absent; X2is any naturally occurring amino acid or is absent; X3is any naturally occurring amino acid or is absent; X4is any naturally occurring amino acid or is absent; and X5is any naturally occurring amino acid or is absent. Preferably, the N-terminal portion has the sequence X1X2X3X4X5, wherein X1is G, A, V, L, I or is absent, X2is D, E, N, Q or is absent, X3is D, E, N, Q or is absent, X4is H, K, R or is absent, and X5 is F, Y, W or is absent. More preferably, X1 is V, G or absent (for example V or absent); X2is D or absent; X3is N or absent; X4is K or absent; and X5is F or absent. In certain embodiments, preferably none of X1, X2, X3,X4and X5is absent; X1is absent and the other residues are not absent; X1 and X2 are absent and the other residues are not absent; X1, X2and X3are absent and the other residues are not absent; X1, X2, X3and X4are absent and the other residue is not absent; or all of X1, X2, X3,X4and X5are absent. In certain especially preferred embodiments, the N-terminal portion has the sequence X1X2X3X4X5wherein X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; X1is absent, X2is D, X3is N, X4is K, and X5is F; X1is absent, X2is absent, X3is N, X4is K, and X5is F; X1is absent, X2is absent, X3is absent, X4is K, and X5is F; X1is absent, X2is absent, X3is absent, X4is absent, and X5is F; or X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent. For example, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; or X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent, i.e. the N-terminal portion has the sequence VDNKF, GDNKF or is absent; and more preferably has the sequence VDNKF or is absent. In one preferred embodiment, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F, i.e. the N-terminal portion has the sequence VDNKF or GDNKF; and more preferably the N-terminal portion has the sequence VDNKF. In one preferred embodiment, X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent, i.e. the N-terminal portion is absent. The C-terminal portion may be absent or may be a sequence of 1 to 50 naturally occurring amino acids. For example, the C-terminal portion may be absent or may be a sequence of from 1 to 40, 1 to 35, 1 to 30, from 1 to 25, from 1 to 22, or from 1 to 21 naturally occurring amino acids. Preferably, the C-terminal portion may be absent or may be a sequence of from 10 to 35, 10 to 30, from 15 to 25, from 18 to 22, from 1 to 21 naturally occurring amino acids, for example 18, 19, 20, 21 or 22 naturally occurring amino acids. Preferably, the C-terminal portion has a sequence such that it enhances target binding by the CD16a-binding motif of Helix 1 and Helix 2. In certain embodiments, the C-terminal portion is absent or has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is a sequence of 1 to 14 naturally occurring amino acids, X39 is any naturally occurring amino acid, X56 is any naturally occurring amino acid or is absent, X57is any naturally occurring amino acid or is absent, and X58is any naturally occurring amino acid or is absent, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In certain embodiments, X38is a sequence of 1 to 9, 1 to 7 or 1 to 5 naturally occurring amino acids. More preferably X38is a sequence of 1 to 4, for example 1, 2, 3 or 4 amino acids. In one especially preferred embodiment, X38is any naturally occurring amino acid (i.e. any single (one) naturally occurring amino acid residue). In one preferred embodiment, the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, X39is S, T, M, P, F, Y or W, X56is G, A, V, L, I or is absent, X57is P or is absent, and X58is H, K, R or is absent, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In another preferred embodiment, the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58, wherein X56is G, A, V, L, I or is absent, X57is P or is absent, and X58is H, K, R or is absent, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In an especially preferred embodiment, the C-terminal portion has the X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, X39is S, X56is A or is absent, X57is P or is absent, and X58is K or is absent, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In another especially preferred embodiment, the C-terminal portion has the PSQSANLLAEAKKLNDAQX56X57X58, wherein X56is A or is absent, X57is P or is absent, and X58 is K or is absent, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. For example, in certain embodiments the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, and X39is S; and: X56is A, X57is P, and X58is K; or X56is A, or X57is P, and X58is absent; orX56is A, X57is absent, and X58is absent; or X56is absent, X57is absent, and X58is absent. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. Or, for example, the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58, wherein X56is A, X57is P, and X58is K; or X56is A, or X57is P, and X58is absent; or X56is A, X57is absent, and X58is absent; or X56is absent, X57is absent, and X58is absent. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In one preferred the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, and X39is S; and X56is A, X57is P, and X58is K. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. Or, for example, the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58, wherein X56is A, X57is P, and X58is K. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In an alternative preferred embodiment the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, and X39is S; and: X56is absent, X57is absent, and X58is absent. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. Or, for example, For example, the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58, X56is absent, X57is absent, and X58is absent. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In one embodiment, the N-terminal portion has the sequence X1X2X3X4X5wherein X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; X1is absent, X2is D, X3is N, X4is K, and X5is F; X1is absent, X2is absent, X3is N, X4is K, and X5is F; X1is absent, X2is absent, X3is absent, X4is K, and X5is F; X1is absent, X2is absent, X3is absent, X4is absent, and X5is F; or X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent (for example, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F, or X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent); and the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, X39is S, T, M, P, F, Y or W, X56is G, A, V, L, I or is absent, X57is P, and X58is H, K, or R, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement; and more preferably X38is P, X39is S, X56is A, X57is P, and X58is K, and optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In another embodiment, the N-terminal portion has the sequence X1X2X3X4X5wherein X1 is V or G (preferably V), X2 is D, X3 is N, X4 is K, and X5 is F; X1 is absent, X2 is D, X3is N, X4is K, and X5is F; X1is absent, X2is absent, X3is N, X4is K, and X5is F; X1is absent, X2is absent, X3is absent, X4is K, and X5is F; X1is absent, X2is absent, X3is absent, X4 is absent, and X5 is F; or X1 is absent, X2 is absent, X3 is absent, X4 is absent, and X5is absent (for example, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F, or X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent); and the C- terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58, wherein X56is G, A, V, L, I or is absent, X57is P, and X58is H, K, or R, and optionally wherein from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement; and more preferably X56is A, X57is P, and X58is K, and optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In one very preferred embodiment, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; and X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K). In an alternative very preferred embodiment X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent; and X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K). In another preferred embodiment, the N-terminal portion has the sequence X1X2X3X4X5, wherein X1is G, A, V, L, or I, X2is D, E, N, or Q, X3is D, E, N, or Q, X4is H, K, or R, and X5is F, Y, or W (for example, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F); and the C-terminal portion has sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, X39is S, T, M, P, F, Y or W (preferably S); and X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K); X56is G, A, V, L or I (preferably A), X57is P, and X58is absent; X56is G, A, V, L or I (preferably A), X57is absent, and X58is absent; or X56is absent, X57is absent, and X58is absent. More preferably, X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K); or X56is absent, X57is absent, and X58is absent. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In one preferred embodiment, the N-terminal portion has the sequence X1X2X3X4X5, wherein X1is G, A, V, L, or I, X2is D, E, N, or Q, X3is D, E, N, or Q, X4is H, K, or R, and X5is F, Y, or W (for example, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F); and the C-terminal portion has sequence PSQSANLLAEAKKLNDAQX56X57X58, wherein X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K); X56is G, A, V, L or I (preferably A), X57is P, and X58is absent; X56is G, A, V, L or I (preferably A), X57is absent, and X58is absent; or X56is absent, X57is absent, and X58is absent. More preferably, X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K); or X56is absent, X57is absent, and X58 is absent. In such embodiments optionally from 1 to 5 (for example 1, 2, 3, 4 or 5; preferably 1, 2 or 3) of the residues in the sequence PSQSANLLAEAKKLNDAQ are replaced by an alternative residue, for example replaced by an alternative residue that is a conservative replacement. In one very preferred embodiment, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; and X56is absent, X57is absent, and X58is absent. In an alternative very preferred embodiment, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; X56is G, A, V, L or I (preferably A), X57is P, and X58is H, K, or R (preferably K). In certain embodiments, (i) the separating portion has the sequence X20X21X22; and / or the N-terminal portion has the sequence X1X2X3X4X5 ;and / or the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58; wherein, in said separating portion, X20is P or T; X21is N; X22is L; wherein in said N-terminal portion, X1is V or G (preferably V), or absent; X2is D or absent; X3is N or absent; X4is K or absent; X5is F or absent; and wherein in said C-terminal portion, X56 is A or absent; X57 is P or absent; X58 is K or absent. Alternatively, (ii) the separating portion, N-terminal portion, and C-terminal portion are as defined in (i) above, wherein optionally (a) within each portion 1, 2 or 3 residues are replaced by an alternative residue; or (b) within those portions taken together at least 1 and no more than 5 (for example, 1, 2, 3, 4, or 5) residues are replaced by an alternative residue. In such embodiments, preferably the separating portion has the sequence PNL or TNL. Alternatively, or additionally, in such embodiments, the N-terminal portion has the sequence VDNKF. In one embodiment, the N-terminal portion may comprise the sequence X1X2X3X4X5, wherein: X1is V, or absent; X2is D or absent; X3is N or absent; X4is K or absent; X5is F or absent. For example, the N-terminal portion may comprise the sequence VDNKF. The separating portion may comprise the sequence X20X21X22, wherein: X20is P or T; X21is N; X22is L. For example, the separating portion may comprise the sequence PNL. The C-terminal portion may comprise the sequence PSQSANLLAEAKKLNDAQX56X57X58, wherein: X56is A or absent; X57is P or absent; X58is K or absent. For example, the C-terminal portion may comprise the sequence PSQSANLLAEAKKLNDAQAPK or PSQSANLLAEAKKLNDAQ. The C-terminal portion may have the structure [Second separating portion]-[Helix 3]-[C-terminal sequence]. For example: - the Second separating portion comprises the sequence PS; - the Helix 3 portion comprises the sequence QSANLLAEAKKLNDAQ; - and the C-terminal sequence comprises the sequence APK or is absent. In such embodiments, within those five portions (N-terminal portion, separating portion, second separating portion, Helix 3, and C-terminal sequence) taken together, at least 1 and no more than 8 (for example 5) of the residues may be replaced by an alternative residue. For example, the number of replaced residues is at least 1 and no more than 7, at least 1 and no more than 6, at least 1 and no more than 5, at least 1 and no more than 4, for example at least 1 and no more than 3, for example at least 1 and no more than 2. Particularly, there may be 1, 2, 3, 4 or 5 replacement residues in total in those portions. Thus, in such embodiments, across the entire CD16a-binding polypeptide of the invention (i.e. across the entire overall structure [N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]), at least 1 and no more than 11 of the residues may be replaced by an alternative residue. For example, the number of replaced residues is at least 1 and no more than 10, for example at least 1 and no more than 9, for example at least 1 and no more than 8, for example at least 1 and no more than 7, for example at least 1 and no more than 6. Particularly, there may be 1, 2, 3, 4, 5, 6, 7,8, 9, 10 or 11 replacement residues in total across the entire overall structure [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C- terminal portion]. In advantageous embodiments of CD16a -binding polypeptides of the invention, where the C-terminal portion comprises a helical or substantially helical region (for example Helix 3 as described immediately above; for example the sequence QSANLLAEAKKLNDAQ), Proline (P) and Cysteine (C) are not present in that helical or substantially helical region. In another embodiment, additionally Glycine (G) is also not present in that helical or substantially helical region for example Helix 3 as described immediately above; for example the sequence QSANLLAEAKKLNDAQ). In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1 to 75 (as shown in the table Figure 11), and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (as shown in the table Figure 12). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1 to 75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1 to 75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043). In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1 to 73 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1 to 73. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1 to 73. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.11 to 73 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.11 to 73. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.11 to 73. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1 to 67 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.11 to 67. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1 to 67. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) as shown in the table Figure 12. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043). In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.19, 33, 17, 29, 53, 16, 25, 15, 51, 36, 49, 55, 43, 24, 56, 12, 28, 21, 59, 52, 32, 18, 27, 35 and 11 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.19, 33, 17, 29, 53, 16, 25, 15, 51, 36, 49, 55, 43, 24, 56, 12, 28, 21, 59, 52, 32, 18, 27, 35 and 11. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.19, 33, 17, 29, 53, 16, 25, 15, 51, 36, 49, 55, 43, 24, 56, 12, 28, 21, 59, 52, 32, 18, 27, 35 and 11. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.34, 45 and 51 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.34, 45 and 51. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.34, 45 and 51. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.26, 35 and 47 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.26, 35 and 47. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.26, 35 and 47. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1, 12, 17, 19, 29, 33, 49, 51, and 53 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1, 12, 17, 19, 29, 33, 49, 51, and 53. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1, 12, 17, 19, 29, 33, 49, 51, and 53. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.12, 17, 19, 29, 33, 49, 51, and 53 as shown in the table Figure 11. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.12, 17, 19, 29, 33, 49, 51, and 53. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.12, 17, 19, 29, 33, 49, 51, and 53. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.17, 19, 29, 33, and 53 as shown in the table Figure 23. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.17, 19, 29, 33, and 53. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.17, 19, 29, 33, and 53. In one preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.15, 17, 19, and 51 as shown in the table Figure 23. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.15, 17, 19, and 51. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.15, 17, 19, and 51. In one preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.15, 17 and 19 as shown in the table Figure 23. In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.15, 17 and 19. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.15, 17 and 19. In one preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO. 1, 17, 19, 35, and 51 (as shown in the table in Figure 11) and 245 (Example ID 1001) (as shown in the table Figure 12). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.1, 17, 19, 35, 51 and 245 (Example ID 1001). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1, 17, 19, 35, 51 and 245 (Example ID 1001). In one preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO. 1, 17, 19, 35, and 51 (as shown in the table in Figure 11) and 245 (Example ID 1001) (as shown in the table Figure 12). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.1, 17, 19, 51 and 245 (Example ID 1001). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1, 17, 19, 35, 51 and 245 (Example ID 1001). In one preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.17, 19, and 51 (as shown in the table in Figure 11), and 245 (Example ID 1001) (as shown in the table Figure 12). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.17, 19, 51 and 245 (Example ID 1001). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.17, 19, 51 and 245 (Example ID 1001). In one very preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1, 35 and 51 (as shown in the table in Figure 11) and SEQ ID NO.245 (Example ID 1001) (as shown in the table Figure 12). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.1, 35, 51 and 245 (Example ID 1001). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1, 51 and 245 (Example ID 1001). In one very preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1 and 51 (as shown in the table in Figure 11) and SEQ ID NO.245 (Example ID 1001) (as shown in the table Figure 12). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.1, 51 and 245 (Example ID 1001). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1, 51 and 245 (Example ID 1001). In another very preferred aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.1, 35 and 51 (as shown in the table in Figure 11). In such sequences, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from of SEQ ID NO.1, 35 and 51. In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.1, 35 and 51. In one aspect of the invention, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.245 (Example ID 1001), as shown in the table Figure 12. In such a sequence, optionally from 1 to 5 (preferably optionally 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement. In one embodiment, the CD16a binding polypeptide comprises a sequence selected from SEQ ID NO.245 (Example ID 1001). In one embodiment, the CD16a binding polypeptide has a sequence selected from the group consisting of SEQ ID NO.245 (Example ID 1001). In one preferred aspect of the invention, the CD16a binding polypeptide comprises the sequence: a*)VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQ APK [SEQ ID NO: 1]; In a further aspect of the invention the CD16a binding polypeptide comprises the sequence: b*)VDNKFNKEQFYARDEIDLLPNLNEDQKWAFYMSLIDDPSQSANLLAEAKKLNDAQ APK [SEQ ID NO: 2]; In a further aspect of the invention the CD16a binding polypeptide comprises the sequence: c*)VDNKFNKEFWIAESEIESLPNLNIYQKWAFKYSLADDPSQSANLLAEAKKLNDAQAP K [SEQ ID NO: 3]. In a further preferred aspect of the invention the CD16a binding polypeptide comprises the sequence: VDNKFNKELQNAQREIRALPNLNHHQQFAFIHKLIDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 35]. In a further preferred aspect of the invention the CD16a binding polypeptide comprises the sequence: VDNKFNKEQQIAQYEIRKLPNLNHHQTFAFIKSLLDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 51]. As discussed above, a number of residues in the polypeptides of the invention may be substituted by an alternative residue. For example, in a polypeptide as set out in a*), b*) or c*) immediately above (or SEQ ID No.35 or 51 immediately above) , at least 1 and no more than 5 of the residues may be replaced by an alternative residue. For example, the number of replaced residues is at least 1 and no more than 4, for example at least 1 and no more than 3, for example 1 at least 1 and no more than 2. Particularly, there may be 1, 2, 3, 4 or 5 replacement residues in total in those portions. As there are 58 residues in polypeptides of this aspect of the invention, a peptide with 5 residues replaced has 91% sequence identity (91.4%) with the recited sequence. For replacement of 4 residues, it is 93% (93.1%), for replacement of 3 residues, it is 95% (94.8%), for replacement of 2 residues it is 97% (96.6%) and for replacement of 1 residue it is 98% sequence identity (98.3%). As mentioned above, in an embodiment, a*) Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. In that embodiment, as in others, a number of residues may each be substituted by an alternative residue, as described herein. In any such alternative polypeptides of the invention with alternative residues in place, binding to the CD16a receptor is maintained. For example, the CD16a binding efficacy is at least 1% of the binding efficacy of the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions. With 1% binding efficacy, it is understood that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 100 times the IC50 concentration for the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions. More preferably, the binding efficacy is at least 5%, 10%, 20%, 25% or 50% of the binding efficacy of the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions. That is to say that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 20 times, 10 times, 5 times, 4 times or 2 times the IC50concentration for the peptide of SEQ ID NO: 1 to the CD16a receptor, when measured under the same conditions. As also mentioned above, in an embodiment, b*) Helix 1 comprises the sequence QFYARDEIDL and Helix 2 comprises the sequence EDQKWAFYMSLI. In that embodiment, as in others, a number of residues may each be substituted by an alternative residue, as described herein. In any such alternative polypeptides of the invention with alternative residues in place, binding to the CD16a receptor is maintained. For example, the CD16a binding efficacy is at least 1% of the binding efficacy of the peptide of SEQ ID NO: 74 to the CD16a receptor, when measured under the same conditions. With 1% binding efficacy, it is understood that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 100 times the IC50concentration for the peptide of SEQ ID NO: 74 to the CD16a receptor, when measured under the same conditions. More preferably, the binding efficacy is at least 5%, 10%, 20%, 25% or 50% of the binding efficacy of the peptide of SEQ ID NO: 74 to the CD16a receptor, when measured under the same conditions. That is to say that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 20 times, 10 times, 5 times, 4 times or 2 times the IC50concentration for the peptide of SEQ ID NO: 74 to the CD16a receptor, when measured under the same conditions. As also mentioned above, in an embodiment, c*) Helix 1 comprises the sequence FWIAESEIES and Helix 2 comprises the sequence IYQKWAFKYSLA. In that embodiment, as in others, a number of residues may each be substituted by an alternative residue, as described herein. In any such alternative polypeptides of the invention with alternative residues in place, binding to the CD16a receptor is maintained. For example, the CD16a binding efficacy is at least 1% of the binding efficacy of the peptide of SEQ ID NO: 75 to the CD16a receptor, when measured under the same conditions. With 1% binding efficacy, it is understood that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 100 times the IC50concentration for the peptide of SEQ ID NO: 75 to the CD16a receptor, when measured under the same conditions. More preferably, the binding efficacy is at least 5%, 10%, 20%, 25% or 50% of the binding efficacy of the peptide of SEQ ID NO: 75 to the CD16a receptor, when measured under the same conditions. That is to say that the IC50concentration of the alternative polypeptide for binding to the CD16a receptor is no more than 20 times, 10 times, 5 times, 4 times or 2 times the IC50concentration for the peptide of SEQ ID NO: 75 to the CD16a receptor, when measured under the same conditions. The invention further provides a CD16a-binding polypeptide, wherein the CD16a- binding polypeptide consists of one motif that binds to CD16a, wherein said polypeptide consists of the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2], wherein the CD16a-binding motif sequence is selected from SEQ ID No.1011 to 1026 and 1044 of Figure 14 (and optionally the peptide further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions). The invention further provides a CD16a-binding polypeptide of the invention, wherein the CD16a-binding polypeptide consists of the CD16a-binding polypeptide and wherein the sequence of the CD16a-binding polypeptide is selected SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) of Figure 12 (and optionally further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions). In one very preferred embodiment the CD16a-binding polypeptide (for example a CD16a-binding polypeptide of the invention described above or below) consists of one motif that binds to CD16a, wherein said polypeptide consists of the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2] wherein the CD16a-binding motif sequence is selected from SEQ ID No.1011 to 1026 and 1044 of Figure 14 (and optionally further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions). In one very preferred embodiment the CD16a-binding polypeptide consists of a CD16a-binding polypeptide of the invention and wherein the sequence of the CD16a- binding polypeptide is selected from SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) of Figure 12 (and optionally further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions). The invention further provides a CD16a-binding polypeptide, wherein the CD16a- binding polypeptide consists of one motif that binds to CD16a, wherein said polypeptide consists of the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2], and the peptide further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions); and wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. The invention further provides a CD16a-binding polypeptide of the invention, wherein the CD16a-binding polypeptide consists of the CD16a-binding polypeptide further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions); and wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. In one very preferred embodiment the CD16a-binding polypeptide (for example a CD16a-binding polypeptide of the invention described above or below) consists of one motif that binds to CD16a, wherein said polypeptide consists of the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2], and the peptide further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions); and wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. In one very preferred embodiment the CD16a-binding polypeptide consists of a CD16a-binding polypeptide of the invention and further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions); and wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. For the avoidance of doubt, in embodiments wherein a CD16a-binding polypeptide consists of a CD16a-binding motif and / or a CD16a-binding polypeptide, the CD16a- binding polypeptide is not connected to a further CD16a-binding polypeptide, i.e. the CD16a-binding polypeptide is not a portion of a CD16a-binding oligomer of the invention. In another very preferred embodiment the CD16a-binding polypeptide (for example a CD16a-binding polypeptide of the invention described above or below) consists of one motif that binds to CD16a, wherein said polypeptide consists of the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2], and wherein the polypeptide further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example one, two or three additional functional portions). In another very preferred embodiment the CD16a-binding consists of a CD16a-binding polypeptide of the invention, and further comprises one or more additional functional portions as described below (for example 1, 2, 3, 4, 5, 6 or more); for example 1, 2 or 3 additional functional portions (preferably 1 or 2 additional functional portions); and wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. Multimeric CD16a-binding polypeptides: CD16a-binding oligomers In certain aspects, the present invention provides a CD16a-binding oligomer which comprises at least two (i.e. two or more than two, for example 2, 3, 4, 5, 6 or more; preferably 2, 3 or 4) CD16a-binding polypeptides of the present invention, wherein the CD16a-binding polypeptides of a CD16a-binding oligomers of the invention are connected via one or more linkers of the present invention as described herein. In one preferred embodiment, the CD16a-binding oligomer of the present invention comprises two CD16a-binding polypeptides of the present invention. In another embodiment, a CD16a-binding oligomer of the present invention comprises at least three, at least four, at least 5 or at least 6 CD16a-binding polypeptides of the present invention, for example 3, 4, 5 or 6 or more CD16a-binding polypeptides of the present invention. The CD16a-binding polypeptides of a CD16a-binding oligomers of the invention are connected via one or more linkers as described herein. For the avoidance of doubt, the term “separated by a linker” as used herein means connected by or connected via a linker. A CD16a-binding oligomer of the present invention is a multimeric binder, as it has multiple CD16a binding motifs, i.e. it has a CD16a binding motif ([Helix 1]-[Separating portion]-[Helix 2]) in each CD16a-binding polypeptide it comprises. A CD16a-binding oligomer of the present invention comprises, at least, a first CD16a- binding polypeptide which is a CD16a-binding polypeptide of the present invention, and a second CD16a-binding polypeptide which is a CD16a-binding polypeptide of the present invention. The first and second CD16a-binding polypeptides may have the same sequence. Alternatively, the first and second CD16a-binding polypeptides may have different sequences. A CD16a-binding oligomer of the present invention may optionally further comprise a third CD16a-binding polypeptide which is a CD16a-binding polypeptide of the present invention. The third CD16a-binding polypeptides may have the same sequence as the first and / or second CD16a-binding polypeptides sequences. Alternatively, the third CD16a-binding polypeptides may have a different sequence to the first and second CD16a-binding polypeptide. A CD16a-binding oligomer of the present invention may optionally further comprise a fourth CD16a-binding polypeptide which is a CD16a-binding polypeptide of the present invention. The fourth CD16a-binding polypeptides may have the same sequence as the first and / or second and / or third CD16a-binding polypeptides sequences. Alternatively, the fourth CD16a-binding polypeptide may have a different sequence to the first, second and third CD16a-binding polypeptides. In one preferred embodiment, a CD16a-binding oligomer of the present invention comprises a first CD16a-binding polypeptide that comprises a first binding motif selected from SEQ ID NOs.150 to 221 and SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); and a second CD16a-binding polypeptide that comprises a second binding motif selected from SEQ ID NOs.150 to 221 and SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement). The first and second CD16a-binding motifs may have the same sequence or a different sequence. In one preferred embodiment, a CD16a-binding oligomer of the present invention comprises a first CD16a-binding polypeptide that comprises a first binding motif selected from SEQ ID NOs.150 to 221 (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); and a second CD16a- binding polypeptide that comprises a second binding motif selected from SEQ ID NOs.150 to 221 (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement).The first and second CD16a-binding motifs may have the same sequence or a different sequence. In one preferred embodiment, a CD16a-binding oligomer of the present invention comprises a first CD16a-binding polypeptide that has a sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); and a second CD16a-binding polypeptide that has sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement). The first and second CD16a-binding polypeptide may have the same sequence or a different sequence. In one preferred embodiment, a CD16a-binding oligomer of the present invention comprises a first CD16a-binding polypeptide that has a sequence selected from SEQ ID NOs.1-75 (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); and a second CD16a-binding polypeptide that has sequence selected from SEQ ID NOs.1-75 (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement). The first and second CD16a-binding polypeptide may have the same sequence or a different sequence. In another embodiment, a CD16a-binding oligomer of the present invention comprises a first CD16a-binding polypeptide that has a sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); a second CD16a-binding polypeptide that has sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); and a third CD16a-binding polypeptide that has sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement). The first, second and third CD16a-binding polypeptide may have the same sequence, or each have a different sequence, or two sequences may be the same and one may be different). Optionally, a fourth CD16a-binding polypeptide that has sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement) may be present; which may be the same as any one of the first, second, or third sequences, or may be different. In one preferred embodiment, a CD16a-binding oligomer of the present invention comprises a first CD16a-binding polypeptide that has a sequence selected from SEQ ID NOs.1, 35, 74, 75, 51 or 245 (Example ID 1001) (for example 1, 74 or 75) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement); and a second CD16a-binding polypeptide that has sequence selected from SEQ ID NOs.1, 74, 75, 35, 51 or 245 (Example ID 1001) (for example 1, 74 or 75) (and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement). The first and second CD16a-binding polypeptide may have the same sequence or a different sequence (for example, the first CD16a-binding polypeptide may have SEQ ID NO.1; and the second CD16a-binding polypeptide may have SEQ ID NO.1; or the first CD16a-binding polypeptide may have SEQ ID NO.74; and the second CD16a-binding polypeptide may have SEQ ID NO.1; the first CD16a-binding polypeptide may have SEQ ID NO.75; and the second CD16a-binding polypeptide may have SEQ ID NO.1). For the avoidance of doubt, when used herein “[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]” means that the CD16a binding polypeptide sequence is N-terminus to C-terminus, left to right; and when used herein “[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]” means that the CD16a binding polypeptide sequence is C-terminus to N- terminus, left to right. For the avoidance of doubt, when used herein “ -[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]” (i.e. with the “-“ prefix added) this indicates that the point or attachment is on the N-terminal portion of the CD16a binding polypeptide (as well as that the CD16a binding polypeptide sequence is N- terminus to C-terminus, left to right). When used herein “ -[C-terminal portion]- [Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]” (i.e. with the “-“ prefix added) this indicates that the point or attachment is on the C-terminal portion of the CD16a binding polypeptide (as well as that the CD16a binding polypeptide sequence is C-terminus to N-terminus, left to right). For the avoidance of doubt, when used herein “[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion]” means that the hBCMA binding polypeptide sequence is N-terminus to C-terminus, left to right; and when used herein “[hBCMA C-terminal portion]-[hBCMA Helix 2]- [hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N-terminal portion]” means that the hBCMA binding polypeptide sequence is C-terminus to N-terminus, left to right. For the avoidance of doubt, when used herein “ -[hBCMA N-terminal portion]- [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion]” (i.e. with the “-“ prefix added) this indicates that the point or attachment is on the N-terminal portion of the hBCMA binding polypeptide (as well as that the hBCMA binding polypeptide sequence is N-terminus to C-terminus, left to right). When used herein “ -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N-terminal portion]” (i.e. with the “-“ prefix added) this indicates that the point or attachment is on the C-terminal portion of the hBCMA binding polypeptide (as well as that the hBCMA binding polypeptide sequence is C-terminus to N-terminus, left to right). In one embodiment, the CD16a-binding oligomer of the present invention comprises at least 2 (for example 2) CD16a-binding polypeptides, and the CD16a-binding oligomer comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion], [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion], [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]- [linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion], or [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]- [linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]; wherein each N-terminal portion in the oligomer may have the same sequence or have different sequences; each C-terminal portion in the oligomer may have the same sequence or have different sequences; each separating portion in the oligomer may have the same sequence or have different sequences; each Helix 1 portion in the oligomer may have the same sequence or have different sequences; and each Helix 2 portion in the oligomer may have the same sequence or have different sequences; and wherein the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide. Preferably the linker is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid. In embodiments where the linker is attached to the [N-terminal portion] of a CD16a binding polypeptide, preferably the N-terminal portion has the sequence X1X2X3X4X5and the linker is attached at position X1of the [N-terminal portion] (for example, at the N-terminus or at the side chain of position X1(for example wherein X1is lysine)), or at the side chain of position X4of the [N-terminal portion] (for example wherein X4is lysine). In embodiments where the linker is attached to the [C-terminal portion] of a CD16a binding polypeptide, preferably the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58and the linker is attached at position X58of the [C-terminal portion] (for example, at the C-terminus or at the side chain of position X58(for example wherein X58is lysine)), or at position X50of the [C-terminal portion] wherein X50is lysine. In one embodiment, preferably the linker comprises one or more group selected from the group consisting of triazole (especially 1,4-triazole, , ,

[0006] wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1to 8, or 2 to 8 (and especially 2, 3, 4, 8, 12 or 24), and especially 2, 3, 4 or 8). In one embodiment, the CD16a-binding oligomer of the present invention comprises at least 3 (for example 3) CD16a-binding polypeptides. For example, the CD16a- binding oligomer comprises the following structure [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C- terminal portion], [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C- terminal portion], [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]- [Linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C- terminal portion], [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]- [Linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C- terminal portion], [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]- [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N- terminal portion], [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]-[Linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N- terminal portion], [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]- [Linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]- [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N- terminal portion], or [C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]- [Linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]-[Linker]-[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N- terminal portion]; wherein each linker portion in the oligomer may have the same sequence or have different sequences; each N-terminal portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each C-terminal portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each separating portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each Helix 1 portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; and each Helix 2 portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; and wherein each linker may be the same or may be different, and each linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide (and preferably wherein each linker is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N- terminal portion] of each CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid). In such embodiments, preferably at least one linker (for example each linker) comprises one or more group selected from the group consisting of triazole wherein y is 1 to 10 (for example y is 1 to 5), , wherein n is 1 to 30 (for example 1 to 24 or 2 to 8). In one embodiment, the CD16a-binding oligomer of the present invention comprises at least 3 (for example 3) CD16a-binding polypeptides, wherein the CD16a-binding oligomer comprises the following structure, wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; B represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion] and C represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]; and wherein each N-terminal portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each C-terminal portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each separating portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each Helix 1 portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; and each Helix 2 portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; and wherein the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide. For example, the linker is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid. In such embodiments, preferably the linker comprises one or more group selected from the group consisting of triazole (for example one or two triazoles, for example one or two 1,4-triazoles) and , wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1 to 8, or 2 to 8 (and especially 2, 3, 4, 8, 12 or 24), and especially 2, 3 or 4 (for example 2 or 3). In such embodiments the linker mayoptionally additionally comprises group.In another embodiment, the CD16a-binding oligomer of the present invention comprises at least 3 (for example 3) CD16a-binding polypeptides, wherein the CD16a-binding oligomer comprises the following structure, Wherein, A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; and B represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]; and wherein each N-terminal portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each C-terminal portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each separating portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each Helix 1 portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; and each Helix 2 portion in the oligomer may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; wherein each linker may be the same or may be different, and each linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide. In one embodiment, preferably at least one (for example each) linker comprises one or more group selected from the group consisting of triazole (especially 1,4-triazole, , wherein n is 1 to 30 (for example 1 to 24 or2 to 8). In certain embodiments of the present invention, a CD16a-binding oligomer of the present invention may comprise two CD16a-binding polypeptides, each of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, each of the two CD16-a binding polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, a CD16a-binding oligomer of the present invention may comprise two CD16a-binding polypeptides, one of which has a sequence in which Helix 1 comprises the sequence QFYARDEIDL and Helix 2 comprises the sequence EDQKWAFYMSLI, and the other of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, one of the two CD16a binding polypeptides may have the sequence: VDNKFNKEQFYARDEIDLLPNLNEDQKWAFYMSLIDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 2] and The other may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, a CD16a-binding oligomer of the present invention may comprise two CD16a-binding polypeptides, one of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM, and the other of which has a sequence in which Helix 1 comprises the sequence FWIAESEIES and Helix 2 comprises the sequence IYQKWAFKYSLA. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, one of the two polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1] and The other may have the sequence: VDNKFNKEFWIAESEIESLPNLNIYQKWAFKYSLADDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 75]. For example, such a CD16a-binding oligomer may comprise three CD16a-binding polypeptides, each of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, each of the three polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, a CD16a-binding oligomer of the present invention may comprise three CD16a-binding polypeptides, two of which have a sequence in which Helix 1 comprises the sequence QFYARDEIDL and Helix 2 comprises the sequence EDQKWAFYMSLI, and the other one of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, two of the three polypeptides may have the sequence: VDNKFNKEQFYARDEIDLLPNLNEDQKWAFYMSLIDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 74] and The other one may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, CD16a-binding oligomer of the present invention may comprise three CD16a-binding polypeptides, one of which has a sequence in which Helix 1 comprises the sequence QFYARDEIDL and Helix 2 comprises the sequence EDQKWAFYMSLI, and the other two of which have a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, one of the three polypeptides may have the sequence: VDNKFNKEQFYARDEIDLLPNLNEDQKWAFYMSLIDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 74] and The other two may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, CD16a-binding oligomer of the present invention may comprise three CD16a-binding polypeptides, one of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM, and the other two of which have a sequence in which Helix 1 comprises the sequence FWIAESEIES and Helix 2 comprises the sequence IYQKWAFKYSLA. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, one of the three polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1] and The other two may have the sequence: VDNKFNKEFWIAESEIESLPNLNIYQKWAFKYSLADDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 75]. In an alternative example, CD16a-binding oligomer of the present invention may comprise three CD16a-binding polypeptides, two of which have a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM, and the other one of which has a sequence in which Helix 1 comprises the sequence FWIAESEIES and Helix 2 comprises the sequence IYQKWAFKYSLA. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, two of the three polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1] and The other one may have the sequence: VDNKFNKEFWIAESEIESLPNLNIYQKWAFKYSLADDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 75]. For example, such CD16a-binding oligomer of the present invention may comprise four CD16a-binding polypeptides, each of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, each of the four polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, CD16a-binding oligomer of the present invention may comprise four CD16a-binding polypeptides, two of which has a sequence in which Helix 1 comprises the sequence QFYARDEIDL and Helix 2 comprises the sequence EDQKWAFYMSLI, and the other two of which has a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, two of the four polypeptides may have the sequence: VDNKFNKEQFYARDEIDLLPNLNEDQKWAFYMSLIDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 74] and The other two may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1] In an alternative example, CD16a-binding oligomer of the present invention may comprise four CD16a-binding polypeptides, two of which have a sequence in which Helix 1 comprises the sequence VQMAQFEIRK and Helix 2 comprises the sequence HHQSFAFIKSLM, and the other two of which have a sequence in which Helix 1 comprises the sequence FWIAESEIES and Helix 2 comprises the sequence IYQKWAFKYSLA. As set out elsewhere, such sequences may have a number of residues substituted by an alternative residue. For example, two of the four polypeptides may have the sequence: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1] and The other two may have the sequence: VDNKFNKEFWIAESEIESLPNLNIYQKWAFKYSLADDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 75]. Linkers A linker connects together two or more functional portions (defined further herein below) of the polypeptides of the invention. For example, a linker may connect together two or more CD16a binding polypeptides of the present invention (for example in a CD16a-binding oligomer of the invention), or a linker may connect together a CD16a binding polypeptide of the present invention and one or more additional functional portion(s) as defined herein. A linker may also connect together an additional functional portion and an additional functional portion in embodiments where more than one additional functional portion is present in a polypeptide or oligomer of the present invention. For the avoidance of doubt, a linker may connect two functional portions of the polypeptides / oligomers of the invention (for example, connect two CD16a binding polypeptides of the present invention, or connect a CD16a binding polypeptide of the present invention and an additional functional portion (for example a BCMA binding polypeptide)). Alternatively, a linker may connect together more than two (for example three, four or more) functional portions of the polypeptides of the invention. For example one linker may connect two, three, four, or more, functional portions of the polypeptides of the invention (each functional portion may be a CD16a binding polypeptide of the present invention or an additional functional portion (for example a BCMA binding polypeptide)). For example, a linker may connect one CD16a binding polypeptide and two additional functional portions (for example two BCMA binding polypeptide). Alternatively, for example, a linker may connect four polypeptides , for example it may connect two CD16a binding polypeptides and two additional functional portions; or one CD16a binding polypeptides and three additional functional portions. For the avoidance of doubt one CD16a binding polypeptide, or CD16a binding oligomer, or additional functional portion (for example a BCMA binding polypeptide) may be attached to more than one linker. For the avoidance of doubt, a wavy line drawn perpendicular to a free bond in a formula herein indicates a free valence. In particular, a wavy line drawn perpendicular to a free bond in a formula of a linker group (or a part of linker group) herein indicates a free valence, and in particular, a free valence that may be attached to, for example, a further linker group or a part of a linker group, a hydrogen, an - NH2group, an -OH group, a CD16a binding polypeptide of the present invention, a CD16a binding oligomer of the present invention, or an additional functional portion (for example a BCMA binding polypeptide). A linker of the present invention is a synthetic linker as it comprises one or more group that is not an amino acid. More specifically, a linker of the present invention comprises one or more groups (for example, one, two, three, four, five or more groups) selected from the group consisting of triazole (for example a 1,4- or 1,5- substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di-fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooxtane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H-pyrrole-2,5-dione, Examples of triazole groups include, but are not limited to, 1,4- and 1,5- substituted Examples of bicyclic rings comprising a triazole ring include, but are not limited to triazole fused cyclooctane and triazole fused mono- or di-fluorocyclooctane, for example Examples of tricyclic rings comprising a triazole ring include, but are not limited to, triazole fused bicyclononane, for example Examples of tetracyclic rings comprising a triazole ring include, but are not limited to, dibenzocyclooctane and dibenzoazacyclooctane, for example

[0007] . Examples of bicyclic rings comprising a pyridazine ring include, but are not limited to, ,

[0008] Examples of tricyclic rings comprising a pyridazine ring groups include, but are not . The structure of 1H-pyrrole-2,5-dione is as follows: . In certain embodiments, the linker may comprise two 1H-pyrrole-2,5-dione groups, for example, the linker may comprise (for example

[0009] example 1 to 24, 1 to 12, 1 to 10, 1 to 8, or 2 to 8 (and especially 4) or wherein n is to 1 to 30 (for example 1 to 24 or 1 to 20 (and especially 3, 6, 11 or 19) (for example In embodiments wherein the linker comprises a group, wherein n is 1 to 30, preferably n is 1 to 24 (for example n is 1 to 16, 1 to 12, 1 to 10, 1 to 8, or 2 to 8 (and especially 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 19, 20 or 24; and more especially 2, 3, 4, or 8). In embodiments wherein the linker comprises a group, preferably m is 1 to 16 (for example m is 1 to 12, 1 to 10, 1 to 8 or 2 to 8, and especially 2, 3, 4, or 8). In embodiments wherein the linker comprises group, preferably p is 1 to 10 (for example 1 to 8, or 1 to 6, and especially 1, 2, 4, 6 or 8). group, the linker preferably comprises the following structure, . In embodiments wherein the linker comprises the linker preferably additionally comprise at least one (for example one) group, wherein n is 1 to 30 (1 to 24, 1 to 16, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 8). For example, the linker may comprise the following structure: wherein n is 1 to 12, 1 to 10, 1 to 8, or 2 to 8, and especially 8. In certain embodiments the linker comprises group, wherein z is 1 to 4 (for example 1 or 2, and preferably 1) and especially a example z is 1 and the group wherein z is 1, 2 or 3 (and preferably 1 or 2, for example z is 2 and the group is certain embodiments, the linker comprises (or is) a group selected from In one preferred embodiment, a linker of the present invention comprises a group, wherein y is 1 to 10 (for example, y is 1 to 8 or 1 to 6, especially 3, 4, 5 or 6, and more especially 1 to 5, and most especially 4 or 5). In one such embodiment y is 4, i.e. the linker comprises , for example comprises . In another preferred embodiment, a linker of the present invention comprises a group, wherein y is 1 to 10 (for example, y is 1 to 8 or 1 to 6, especially 3, 4, 5 or 6, and more especially 1 to 5, and most especially 4 or 5). In one such embodiment y is 5, i.e. the linker comprises a , example comprises . In one preferred embodiment, a linker of the present invention comprises (or is) a group, for example the linker comprises (or is) a

[0010] In one preferred embodiment, a linker of the present invention comprises (or is) a . In certain embodiments, a linker of the present invention comprises (or is) a group, for example a linker of the present invention comprises (or is) a group selected from

[0011] In certain very preferred embodiments, the linker is

[0012] . In further embodiments, the linker is: In another preferred embodiment, a linker of the present invention comprises (or is) In one preferred embodiment, a linker of the present invention comprises (or is) a comprises (or is) a group selected from: , wherein preferably the ester part of such a group is attached to a lysine side chain (for example attached to the NH2of the lysine side chain) of terminal or non-terminal lysine of a [N-terminal portion] or [C-terminal portion] of a CD16a binding polypeptide of the invention. For example, in embodiments where the linker is attached to the [N-terminal portion] of a CD16a binding polypeptide, and the N-terminal portion has the sequence X1X2X3X4X5, the linker is attached at the side chain of position X1of the [N-terminal portion] wherein X1is lysine, or at the side chain of position X4of the [N-terminal portion] wherein X4is lysine; and especially at the side chain of position X4of the [N-terminal portion] wherein X4is lysine. For example, in where the linker is attached to the [C-terminal portion] of a CD16a binding polypeptide, and the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, the linker is attached at the side chain of position X58of the [C-terminal portion] wherein X58is lysine, or at the side chain of position X50of the [C-terminal portion] wherein X50is lysine; and especially at the side chain of position X50of the [C-terminal portion] wherein X50is lysine. In certain preferred embodiments, a linker of the present invention comprises two or more groups (for example, two, three, four, five or more groups) selected from the group consisting of triazole (for example 1,4-triazole, and in particular , , ,

[0013] wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1to 8, or 2 to 8 (and especially 2, 3, 4, 8, 12 or 24), and especially 2, 3, 4 or 8). In embodiments wherein a linker connects together two functional portions of the polypeptides of the invention, preferably the linker comprises a triazole (for example one or two triazoles (preferably one triazole), for example one or two 1,4-subtitued ,

[0014] . In certain embodiments (for example, embodiments wherein a linker connects together two functional portions of the polypeptides of the invention), the linker comprises one or more group selected from the group consisting of triazole (forexample a 1,4-subtitued triazole) and , wherein n is 1 to 30 (forexample 1 to 24, 1 to 12, 1 to 10, 1 to 8, or 2 to 8 (and especially 2, 3, 4, 8, 12 or 24), and especially 2, 3, 4, 8, 16 or 24). For example, the linker comprises (or is) the following group:

[0015] 1 to 12, 1 to 10, 1 to 8, or 2 to 8 (and especially 2, 3, 4, 8, 12 or 24, and very especially 8 or 24). In certain embodiments (for example, embodiments wherein a linker connects together two functional portions of the polypeptides of the invention), the linker comprises (or is) the following group: In certain embodiments (for example, embodiments wherein a linker connects together two functional portions of the polypeptides of the invention), the linker comprises one or more group selected from dibenzoazacyclooctane (for example,, to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 4, 6 or 8). In certain embodiments the linker comprises (or is) a dibenzoazacyclooctane group. In certain embodiments the linker comprises a dibenzoazacyclooctane and , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 4, 6 or 8). In such embodiments, preferably the linker comprises (or is) the following group: , ,

[0016]

[0017] , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 4, 6 or 8; and more especially 8). In certain embodiments, a linker of the present invention (for example, a linker as defined above) additionally comprises a group selected from the group consisting of ). For example, in embodiments wherein a linker connects together three or more functional portions of the polypeptides of the invention, preferably a linker of the present invention (for example, a linker as defined above) additionally comprises agroup selected from the group consisting , In certain embodiments (for example embodiments wherein a linker connects together three or more functional portions of the polypeptides of the invention), preferably the linker comprises one or more groups selected from triazole (for example one or two (preferably two)triazoles, for example one or two 1,4-subtitued triazoles), and optionally further comprises one or more , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4). In such embodiments the linker may optionally additionally comprises ). In such embodiment, preferably the linker comprises two or more triazoles, and , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, group.In certain very preferred embodiments (for example embodiments wherein a linker connects together three or more (for example three) functional portions of the polypeptides of the invention), preferably the linker comprises one or more (forexample one, two or three, preferably two) , one or more (forexample one, two or three, preferably three) , wherein n is 1 to 30(for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4, and very especially n is 2 or 3 (for example 3)), and one for more (for example one) . In such embodiment, when more than one is present, preferably each n is the same (e.g. each n is 3). In certain very preferred embodiments (for example embodiments wherein a linker connects together three or more (for example three) functional portions of the polypeptides of the invention), preferably the linker comprises one or more (forexample one, two or three, preferably two) wherein y is 1 to10 (for example 1 to 5, preferably 4 or 5 and very especially 4), one or more (forexample one, two or three, preferably three) , wherein n is 1 to 30(for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4, and very especially n is 2 or 3 (for example 3)), and one for more (for example one) . In such embodiment, when more than one is present, preferably each n is the same (e.g. each n is 2). In such embodiment, when more than one present, preferably each y is the same (e.g. each y is 2). In embodiments wherein a linker connects together three or more functional portions (for example 3 functional portions (for example one CD16a binding polypeptide and two additional functional portions (e.g. two BCMA binding

[0018] portions)), preferably the linker comprises (or consists of) the following group: ,

[0019] In another embodiment wherein a linker connects together three or more functional portions (for example 3 functional portions (for example one CD16a binding polypeptide and two additional functional portions (e.g. two BCMA binding portions)) of the polypeptides of the invention, preferably the linker comprises (or

[0020] . In another embodiment wherein a linker connects together three or more functional portions (for example 3 functional portions (for example one CD16a binding polypeptide and two additional functional portions (e.g. two BCMA binding portions)) of the polypeptides of the invention, preferably the linker comprises (or consists of) the following group: . In another embodiment wherein a linker connects together three or more functional portions (for example 3 functional portions (for example one CD16a binding polypeptide and two additional functional portions (e.g. two BCMA binding portions)) of the polypeptides of the invention, preferably the linker comprises (or consists of) the following group: ,

[0021] . In another embodiment wherein a linker connects together three or more functional portions (for example 3 functional portions (for example one CD16a binding polypeptide and two additional functional portions (e.g. two BCMA binding portions)) of the polypeptides of the invention, preferably the linker comprises (or

[0022]

[0023] In another embodiment (for example an embodiment wherein a linker connects together three or more functional portions), the linker comprises one or more group selected from triazole (for example one or two triazoles, for example a 1,4-traizole) and , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4). In such embodiments the linker mayoptionally additionally comprises group, a group). In one preferred embodiment, the linker comprises one or two triazole (for example one or two triazoles 1,4-traizole) , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1to 8, or 2 to 8, and especially group. For example,the linker comprises (or is) the following group: wherein q is 1 to 30 (preferably q is 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 8) and each n is independently 1 to 30 (preferably n is 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4). For example the linker comprises (or is) comprises (or is) the following group: 1 to 30 (preferably q is 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 8) and each n is independently 1 to 30 (preferably n is 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4). For example the linker comprises (or is) In another embodiment (for example an embodiment wherein a linker connects together three or more functional portions), the linker comprises one or more group selected from the group consisting of dibenzoazacyclooctane and , wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1 to 8, or 2 to 8, and especially 2, 3 or 4). In such embodiments the linker may optionally additionally

[0024] ). For example, the linker comprises one, two or more dibenzoazacyclooctane groups (for example two dibenzoazacyclooctane, or three dibenzoazacyclooctane groups), and optionally further comprises one or more , wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1 to 8, or 2 to 8, and especially 2, 3 or 4). In such embodiments the linker may optionally additionally comprises ). For example, the linker comprises (or is) the following group:

[0025] . A linker of the present invention may optionally additionally comprise one or more amino acid, for example 1 to 30 amino acids, and in particular 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25 or 30 amino acids. The amino acid(s) may be any naturally occurring or non-naturally occurring amino acid. In preferred embodiments, the linker of the present invention may additionally comprise one or more amino acid, for example 1 to 30 amino acids, selected from the group consisting of C, K, G and S. In certain embodiments, the linker of the present invention may additionally comprise at least one (for example 1 to 30, and in particular 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25 or 30; and preferably 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10; for example 1 to 8, and more preferably 1, 7 or 8) amino acid selected from the group consting of G, K, and C. Additionally, or alternatively, the linker of the present invention may additionally comprises the sequence GGGSG [SEQ ID NO 139], GGGGS [SEQ ID NO 140], GGSGG [SEQ ID NO 141], GSGGG [SEQ ID NO 142] and / or SGGGG [SEQ ID NO 143]; for example the linker may further comprise one G, K or C amino acid and / or further comprises the sequence GGS, SGG, GGSGGS [SEQ ID NO 81], SGGSGG [SEQ ID NO 82], GGSGGSG [SEQ ID NO 83], GSGGSGG [SEQ ID NO 84], GGSGGSGK [SEQ ID NO 85], or KGSGGSGG [SEQ ID NO 86]. In another embodiment, for example, a linker of the present invention may additionally comprises the sequence GGGSG, GGGSGGGGSG [SEQ ID NO 144], GGGSGGGGSGGGGSG [SEQ ID NO 145], GGGSGGGGSGGGGSGGGGSG [SEQ ID NO 146], GGGGS, GGGGSGGGGS [SEQ ID NO:87], GGGGSGGGGSGGGGS [SEQ ID NO:88], GGGGSGGGGSGGGGSGGGGS [SEQ ID NO:89], GGSGG, GGSGGGGSGG [SEQ ID NO 147], GGSGGGGSGGGGSGG [SEQ ID NO 148], GGSGGGGSGGGGSGGGGSGGGGSGG [SEQ ID NO 149], GSGGG, GSGGGGSGGG [SEQ ID NO 90], GSGGGGSGGGGSGGG [SEQ ID NO 91], GSGGGGSGGGGSGGGGSGGG [SEQ ID NO 92], SGGGG, SGGGGSGGGG [SEQ ID NO 518], SGGGGSGGGGSGGGG [SEQ ID NO 93], or SGGGGSGGGGSGGGGSGGGG [SEQ ID NO 94]. For the avoidance of doubt, a linker of the present invention may not comprise any amino acids. In certain preferred embodiments, a linker of the present invention does not comprise any amino acids. In certain preferred embodiments, a linker of the present invention comprises or has the following structure (wherein the amino acids sequences are written N-terminus to C-terminus, left to right; or curved lines represent bonds (the curved line is used to explicitly show a bond between two N-termini or between two C-termini ): “triazole linker C” is:

[0026] In certain preferred embodiments, a linker of the present invention comprises or has the following structure: wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG;

[0027] wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG; wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG;

[0028] wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG; wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG;

[0029] wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG;. wherein each attachment pointindicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG; or wherein each attachment point indicated by a wavy line is directly attached to a functional portion or attached to a functional portion via an amino acid sequence, for example an amino acid sequence consisting of GGSGGSG or GSGGSGG. In embodiments of the invention, a CD16a binding polypeptide, or a CD16a-binding oligomer, comprises at least one linker as described herein. In embodiments of the invention, said linker is between, and thus separates, two or more CD16a-binding polypeptides, for example in a CD16a-binding oligomer of the present invention, or is between, and thus separates, one or more CD16a-binding polypeptide or one or more CD16a-binding oligomer and one or more additional functional portion, for example an immune signalling molecule or an additional binding moiety (for example as described in further detail below). In certain embodiments of the invention, the linker is a branched linker and said linker is between, and thus separates, three or more function portions as described herein. For example, said linker is between, and thus separates, three or more CD16a-binding polypeptides (for example in a CD16a-binding oligomer of the present invention), or is between, and thus separates, one or two or more CD16a-binding polypeptide and one or two or more additional functional portions, for example an immune signalling molecule or an additional binding moiety (for example as described in further detail below). In embodiments and aspects of the present invention that comprise more than one linker, each linker may be the same, or may be different, or some linkers may be the same, and some may be different (for example in embodiments having more than one linker as described herein). With regard to the description above of binding polypeptides comprising a CD16a- binding polypeptide according to the disclosure, it is to be noted that the designation of first, second and further moieties is made for clarity reasons to distinguish between CD16a-binding polypeptide or polypeptides according to the invention on the one hand, and binding moieties exhibiting other functions on the other hand. These designations are not intended to refer to the actual order of the different regions of the binding polypeptide. Similarly, the designations first and second moiety (or monomer unit) are made for clarity reasons to distinguish between said units. Thus, for example, said first moiety (or monomer unit) may without restriction appear at the N-terminal end, in the middle, or at the C-terminal end of the binding polypeptide. Additional functional portions CD16a binding polypeptides as disclosed herein may be connected via a linker (for example one or more linkers) as described herein, to one or more additional functional portions. CD16a binding oligomers as disclosed herein may be connected via a linker (for example one or more linkers) as described herein, to one or more additional functional portions. Therefore, one embodiment of the present invention provides a CD16a binding polypeptide or a CD16a binding oligomer as described herein further comprising at least one (i.e. one or more) additional functional portions, wherein the CD16a-binding polypeptide or CD16a-binding oligomer and the additional functional portion are connected by a linker as described herein. For the avoidance of doubt, the term “separated by a linker” as used herein means connected by or connected via a linker. A ‘functional portion’, as used herein, refers to a component or ‘moiety’ with a specific desired biological activity. The one or more (i.e. the at least one) additional functional portion may for example be a signalling molecule. Examples of suitable signalling molecules include immune signalling molecules such as cytokines, for example IL-15 and derivatives thereof. The one or more (i.e. at least one) additional functional portion may be one or more additional binding moiety(ies), for example one or more binding partner(s) recognising a cell surface protein or antigen, for example an immune cell surface protein or a cell surface tumour antigen (also referred to as a cancer cell surface antigen). Cell surface tumour antigens may for example be tumour-associated antigens or tumour-specific antigens. Examples of additional functional portions include additional binding moieties that are binding partners recognising B-cell maturation antigen (BCMA), cytotoxic T- lymphocyte-associated protein 4 (CTLA-4), Programmed cell death protein 1 (PD-1), disintegrin and metalloprotease 17 (ADAM17), Programmed death-ligand 1 (PD-L1), SLAM family member 7 (SLAMF7), Epithelial Cell Adhesion Molecule (EPCAM), Epidermal growth factor receptor (EGFR / ErbB-1), Epidermal growth factor receptor variant 3(EGFRvIII),erb-b2 tyrosine kinase 2 (ERBB2 / HER2 / CD340), prostate-specific membrane antigen (PSMA), Claudin8.2 (CLDN18.2), delta like protein 3 (DLL3), mucin 16 (MUC16), mucin 17 (MUC17), mucin 1 (MUC1), Trophoblast glycoprotein (TPBG / 5T4 / WAIF1), V-set domain-containing T-cell activation inhibitor 1 (B7- H4 / VTCN1 / B7x / B7S1), cluster of differentiate 20 (CD20), B-Lymphocyte Surface Antigen B4 (CD19), Sialic Acid-Binding Ig-Like Lectin 2 (CD22), TNF receptor superfamily member 8 (CD30), Natural cytotoxicity triggering receptor 1 (NKp46), or NKG2D. Examples of additional functional portions include additional binding moieties that are binding partners recognising a cell surface tumour antigen or cancer cell surface target selected from the group consisting BCMA, ADAM17, SLAMF7, PD-L1, EPCAM, EGFR / ErbB-1, EGFRvIII, ERBB2 / HER2 / CD340, PSMA, CLDN18.2, DLL3, MUC16, MUC17, MUC1, TPBG / 5T4 / WAIF1 and B7- H4 / VTCN1 / B7x / B7S1. Examples of additional functional portions include additional binding moieties that are binding partners recognising an immune cell surface protein or immune cell surface target selected from the group consisting of CTLA-4, PD-1, NKp46, NKG2D CD20, CD19, CD22 and CD30. Examples of additional functional portions include additional binding moieties that are binding partners recognising a cell surface tumour antigen or cancer cell surface target expressed in haematological malignancies, for example BCMA, CD20, CD19, CD22 or CD30. (For the avoidance of doubt, such examples of additional binding moieties, for example binding partners recognising cell surface proteins or antigens, are non-limiting and are specified here by way of illustration.) The additional binding moiety as referred to in this context is not a CD16a binding polypeptide of the present invention. In embodiments of the present invention a CD16a binding polypeptide or CD16a- binding oligomer of the present invention further comprises at least one (i.e. one or more) additional functional portion (for example one or more additional binding moiety(ies) and / or signalling molecule), wherein the CD16a-binding polypeptide or CD16a-binding oligomer and each additional functional portion are separated by a linker as described above. For example, the CD16a binding polypeptide or CD16a- binding oligomer further comprises to one, two, three, four or more additional functional portions (for example one, two, three, four or more additional binding moieties and / or signalling molecules). In certain preferred embodiment, the CD16a binding polypeptide or CD16a-binding oligomer further comprises one or two additional functional portions (for example one or two additional binding moieties or signalling molecules). In one preferred embodiment, the CD16a binding polypeptide or CD16a-binding oligomer further comprises one additional functional portion (for example one additional binding moiety or signalling molecule). In one especially preferred embodiment, the CD16a binding polypeptide or CD16a-binding oligomer further comprises two additional functional portions (for example two additional binding moiety(ies) or signalling molecule). In certain preferred embodiments, an additional functional portion is a signalling molecule. A signalling molecule, for example an immune signalling molecule such as a cytokine, for example IL-15 or derivatives thereof, may be attached at the N- terminal end or the C-terminal end of a CD16a-binding polypeptide or a CD16a- binding oligomer, separated by a linker as described herein. One or more signalling molecule(s) may, alternatively, be attached between two CD16a-binding polypeptides in a CD16a-binding oligomer separated from each CD16a-binding polypeptide by a linker as described herein. Preferably, the signalling molecule(s) may be attached at the N-terminal portion (for example the N-terminus) or the C- terminal portion (for example the C-terminus) of a CD16a-binding polypeptide or a CD16a-binding oligomer via a linker as described above. In certain preferred embodiments, an additional functional portion is an additional binding moiety. For example, an additional functional portion is an additional binding moiety that is a binding partner recognising one of the following: CTLA-4, PD-1, BCMA, ADAM17, PD-L1, SLAMF7, EPCAM, EGFR / ErbB-1, EGFRvIII, ERBB2 / HER2 / CD340, PSMA, CLDN18.2, DLL3, MUC16, MUC17, MUC1, TPBG / 5T4 / WAIF1, B7-H4 / VTCN1 / B7x / B7S1, CD20, CD19, CD22 or CD30. For example, an additional functional portion is an additional binding moiety that is specific for one of the following: CTLA-4, PD-1, BCMA, ADAM17, PD-L1, SLAMF7, EPCAM, EGFR / ErbB-1, EGFRvIII, ERBB2 / HER2 / CD340, PSMA, CLDN18.2, DLL3, MUC16, MUC17, MUC1, TPBG / 5T4 / WAIF1, B7-H4 / VTCN1 / B7x / B7S1, CD20, CD19, CD22 or CD30. In certain preferred embodiments, an additional binding moiety is specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). In certain preferred embodiments, an additional binding moiety is specific for an immune cell surface target (for example a NK cell target, for example NKp46, NKG2D , PD-1, etc). An additional binding moiety, for example a binding partner recognising the cell surface tumour antigen BCMA, may be attached at the N-terminal portion (for example the N-terminus) or the C-terminal portion (for example the C-terminus) of a CD16a-binding polypeptide or a CD16a-binding oligomer, separated by a linker as described herein. The one or more additional binding moiety(ies) may, alternatively, be attached between two CD16a-binding polypeptides in a CD16a-binding oligomer separated from each CD16a-binding polypeptide by a linker as described herein. Preferably, the additional binding moiety(ies), for example a binding partner recognising the cell surface tumour antigen BCMA, may be attached at the N- terminal portion (for example the N-terminus) or the C-terminal portion (for example the C-terminus) of a CD16a-binding polypeptide or a CD16a-binding oligomer, separated by a linker as described above. More preferably, the additional binding moiety(ies), for example a binding partner recognising the cell surface tumour antigen BCMA, may be attached at the N-terminal portion (for example the N-terminus) or the C-terminal portion (for example the C-terminus) of a CD16a- binding polypeptide or a CD16a-binding oligomer, separated by a linker as described above. The present inventors have surprisingly found that a ‘dual engager’ polypeptide comprising a CD16a binding polypeptide or a CD16a binding oligomer and at least one additional functional portion wherein the CD16a-binding polypeptide or CD16a- binding oligomer and the additional functional portion are separated by a linker, as disclosed herein, can retain its CD16a binding ability when fused to an additional binding moiety targeting the myeloma antigen BCMA. This ‘dual engager’ polypeptide comprising a CD16a binding polypeptide as disclosed herein attached to a BCMA binding moiety and separated by a linker as defined here is also surprisingly capable of activating NK cells in the presence of BCMA-expressing tumour cells. In one preferred embodiment, the CD16a-binding polypeptide or CD16a-binding oligomer of the present invention further comprises one or more additional functional portions, for example at least one, at least two, or at least three or at least four additional functional portions. For example, in particular embodiments, CD16a- binding polypeptide or CD16a-binding oligomer of the present invention further comprises 1, 2, 3, 4 or 5 additional functional portions. In especially preferred embodiments, the CD16a-binding polypeptide or CD16a-binding oligomer of the present invention further comprises one, two or three additional functional portions, and more preferably one or two, and most especially two. In especially preferred embodiments, the CD16a-binding polypeptide or CD16a-binding oligomer of the present invention further comprises one or two (preferably two) additional functional portions, wherein each additional functional portion is a BCMA binding polypeptide. In very especially preferred embodiments, the CD16a-binding polypeptide of the present invention further comprises one or two (preferably two) additional functional portions, wherein each additional functional portion is a BCMA binding polypeptide. In embodiments wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least two, at least three or at least four additional functional portions (for example 2, 3, 4 or 5 additional functional portions), each additional functional portion may be the same, or may be different, or some additional functional portions may be the same, and some additional functional portions be different (for example in embodiments having at least 3 or at least 4 additional functional portions (for example 3, 4, 5, 6 or more additional functional portions)). In embodiments wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least two, at least three or at least four additional functional portions (for example 2, 3, 4 or 5 additional functional portions), each additional functional portion may have the same function, or may have different functions, or some additional functional portions may have the same function, and some may have different functions (for example in embodiments having at least 3 or at least 4 additional functional portions (for example 3, 4, 5, 6 or more additional functional portions)). In embodiments wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least two, at least three or at least four additional functional portions (for example 2, 3, 4 or 5) additional functional portions, a first additional functional portion may comprise an additional binding moiety (for example an additional binding specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target); and a second additional functional portion may comprise an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. For example, in one preferred embodiment, a first additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA) and a second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof. In particular, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof. Alternatively, for example, in one preferred embodiment, a first additional functional portion may comprise an additional binding moiety specific for a immune cell target (for example a NK cell target) and a second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof. In particular, a first additional functional portion may comprise an additional binding moiety specific for NK cell target; and second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof. In a very preferred embodiment, a first additional functional portion may comprise an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target); and a second additional functional portion may comprise an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target). For example, a first additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA); and a second additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). In particular, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and a second additional functional portion may comprise an additional binding moiety specific BCMA. Alternatively, for example, a first additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA); and a second additional functional portion may comprise an additional binding moiety specific for an immune cell surface target (for example a NK cell target). In particular, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and a second additional functional portion may comprise an additional binding moiety specific for a NK cell target. In another embodiment, a first additional functional portion may comprise an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof; and a second additional functional portion may comprise an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. When present, (for example in embodiments wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least three or at least four additional functional portions (for example 3, 4 or 5)) a third additional functional portion may comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target), or comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. Preferably, when present, a third additional functional portion may comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target; and especially additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA). When present, (for example in embodiments wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least four additional functional portions (for example 4 or 5)) a fourth additional functional portion may comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target), or comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. Preferably, when present, a fourth additional functional portion may comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target; and especially additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA). When present, (for example in embodiments wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least five additional functional portions (for example 5 or 6)) a fifth additional functional portion may comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target), or comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. In one preferred embodiment, the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least three (for example 3, 4 or 5) additional functional portions, a first additional functional portion may comprise an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target); and a second additional functional portion may comprise an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof; and a third additional functional portion may comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for an immune cell target, for example a NK cell target). In one embodiment, a first additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA); and a second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof; and a third additional functional portion may comprises an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA) or a immune cell target (for example a NK cell target). In particular, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and a second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof; and a third additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). In another embodiment, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and a second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof; and a third additional functional portion may comprise an additional binding moiety specific for an immune cell target (for example a NK cell target). For example, a first additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA); and a second additional functional portion may an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA); and a third additional functional portion may comprises an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA) or a immune cell target (for example a NK cell target). In particular, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and a second additional functional portion may comprise an additional binding moiety specific for BCMA; and a third additional functional portion may comprise an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). In another embodiment, a first additional functional portion may comprise an additional binding moiety specific for BCMA; and a second additional functional portion may comprise an additional binding moiety specific for BCMA; and a third additional functional portion may comprise an additional binding moiety specific for an immune cell target (for example a NK cell target). In embodiments of the invention a CD16a-binding polypeptide, or CD16a-binding oligomer, comprising an additional functional portion of the present invention has an additional functional portion separated from the CD16a-binding polypeptide or the CD16a-binding oligomer by a linker. The linker may be any linker described herein. In certain embodiments, a CD16a-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]-[additional functional portion]; [additional functional portion]-[additional functional portion]-[linker]-[N- terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; wherein, the linker, or each linker, is a linker as described herein; wherein when more than one additional functional portion is present, each additional functional portion may be the same, or may be different; and wherein the linker, or each linker, is attached to any amino acid of the indicated [C- terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide. A schematic representation of CD16a binding polypeptide according to this aspect of the invention and comprising one additional functional portion is provided in Figure 15b, wherein the linker comprises a triazole. Preferably the linker, or a linker (for example each linker), is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine). In embodiments where the linker is attached to the [N-terminal portion] of a CD16a binding polypeptide, preferably the N-terminal portion has the sequence X1X2X3X4X5and the linker is attached at position X1of the [N-terminal portion] (for example, at the N-terminus or at the side chain of position X1(for example wherein X1is lysine)), or at the side chain of position X4of the [N-terminal portion] (for example wherein X4is lysine). In embodiments where the linker is attached to the [C-terminal portion] of a CD16a binding polypeptide, preferably the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58and the linker is attached at position X58of the [C-terminal portion] (for example, at the C-terminus or at the side chain of position X58(for example wherein X58is lysine)), or at position X50of the [C-terminal portion] wherein X50is lysine. In one embodiment the linker, or a linker (for example each linker), is attached to a non-terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [C-terminal portion] in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). When more than one additional functional portion is present and the additional functional portions are attached (i.e. the CD16a-binding polypeptide comprises the structure “[additional functional portion]-[additional functional portion]”), the additional functional portions may be separated by a linker (i.e connected by or connected via a linker), and preferably separated by a linker a linker of the present invention. When more than one linker is present, each linker may be the same, or may be different. In one embodiment, preferably the linker comprises one or more group selected from the group consisting of triazole (especially 1,4-triazole, , ,

[0030] wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1to 8, or 2 to 8 (and especially 2, 3, 4, 8, 12 or 24), and especially 2, 3, 4 or 8). In such embodiments, more preferably the CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]; and even more preferably comprises the following structure: [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]; wherein, the linker is a linker as described herein; and wherein the linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide. Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine). In another embodiment the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [C- terminal portion] in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). In one preferred embodiment, the linker is attached to the terminus of the terminal amino acid and the linker comprises, or has, the following structure: . The linker may optionally additionally comprise one or more amino acid, for example 1 to 30 amino acids. For example the linker may further comprise one G, K or C amino acid and / or further comprises the sequence GGS, SGG, GGSGGS, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG, for example GGSGGSG or GSGGSGG. In certain embodiments, the linker is attached to the side-chain of the terminal amino acid or a non-terminal amino acid of the [N-terminal portion] or the [C- terminal portion] and the linker comprises, or has, the following structure: ,and more preferably wherein the terminal amino acid or the non-terminal amino acid is a lysine and the ester part of such a group is attached to the lysine side chain (for example attached to the NH2of the lysine side chain) of the terminal or non- terminal lysine of the [N-terminal portion] or [C-terminal portion]. In certain embodiments, the linker is attached to the side-chain of a lysine at X50 of the [C-terminal portion] in embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). In certain embodiments, the linker is attached to the side-chain of a terminal lysine at X1of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5. In certain embodiments, the linker is attached to the side-chain of a terminal lysine at X58of the [C-terminal portion] in embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). The linker may optionally additionally comprise one or more amino acid, for example 1 to 30 amino acids. For example the linker may further comprise one G, K or C amino acid and / or further comprises the sequence GGS, SGG, GGSGGS, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG, for example GGSGGSG or GSGGSGG. In embodiments wherein a CD16a-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]-[additional functional portion]; [additional functional portion]-[additional functional portion]-[linker]-[N- terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; each additional functional portion may preferably be an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). More preferably each additional functional portion is an additional binding moiety specific for BCMA. Even more preferably, each additional functional portion is an additional binding moiety specific for hBCMA that is a hBCMA binding polypeptide and which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion] the hBCMA binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]. Even more preferably, such a hBCMA binding polypeptide is a hBCMA binding polypeptide as defined in International Application No. PCT / EP2023 / 064625, the contents of which are incorporated herein by reference. In such embodiments the linker, or a linker, is attached to any amino acid of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the indicated hBCMA binding polypeptide. Preferably the linker, or a linker, is attached to the terminal amino acid of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the indicated hBCMA binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine). In another embodiment the linker, or a linker, is attached to a non-terminal amino acid of the [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of the indicated hBCMA binding polypeptide, for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [hBCMA N-terminal portion] in embodiments wherein the hBCMA [N- terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [hBCMA C-terminal portion] in embodiment wherein the [hBCMA C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). In one preferred embodiment, the CD16a-binding polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion]; [hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion]-[linker]-[C-terminal portion]- [Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]; [hBCMA C-terminal portion]-[hBCMA Helix 2]- [hBCMA Separating portion]- [hBCMA Helix 1]-[hBCMA N-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]. For example, the CD16a-binding polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion]; or [hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion]-[linker]-[C-terminal portion]- [Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]. Alternatively, for example, the CD16a-binding polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion]; or [hBCMA C-terminal portion]-[hBCMA Helix 2]- [hBCMA Separating portion]- [hBCMA Helix 1]-[hBCMA N-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]. Most preferably the CD16a-binding polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or [hBCMA C-terminal portion]-[hBCMA Helix 2]- [hBCMA Separating portion]- [hBCMA Helix 1]-[hBCMA N-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]. In such embodiments the linker is attached to any amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to any amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide. More preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion]. For example, the linker is attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example a terminal lysine) of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide, and / or (preferably and) attached to the terminal amino acid or attached to the side chain of the terminal amino acid (for example a terminal lysine) of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion]. In another embodiment, the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide (for example attached to a non-terminal lysine of the indicated [C- terminal portion] or [N-terminal portion], and especially attached to a non-terminal lysine at X4of the [N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or attached to a non-terminal lysine at X50of the [C-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and / or attached to a non-terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] (for example attached to a non-terminal lysine of the indicated [hBCMA C- terminal portion] or [hBCMA N-terminal portion], and especially attached to a non- terminal lysine at position X4of the [hBCMA N-terminal portion] polypeptide in embodiments wherein the [hBCMA N-terminal portion] has the sequence X1X2X3X4X5or a non-terminal lysine at position X50of the [hBCMA C-terminal portion] in embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). In one preferred embodiment, the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide (for example attached to a non-terminal lysine at X4of the [N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or attached to a non-terminal lysine at X50of the [C-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, and attached to the terminal amino acid or attached to the side chain of the terminal amino acid (for example a terminal lysine) of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion]. In one embodiment, the CD16a binding polypeptide may optionally comprise a further CD16a binding polypeptide such that the CD16a binding polypeptide is a CD16a binding oligomer. In one preferred embodiment the CD16a binding polypeptide does not comprise a further CD16a binding polypeptide (i.e. the a CD16a-binding polypeptide consists of a CD16a-binding motif and / or a CD16a- binding polypeptide). In one preferred embodiment, the CD16a polypeptide comprises (or consists of) a compound selected from the group consisting of L1 to L16. In certain embodiments, a CD16a-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; X represents an additional functional portion; and Y represents an additional functional portion; and wherein the linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide. A schematic representation of CD16a binding polypeptide according to this aspect of the invention is provided in Figure 16b, wherein the linker comprises two triazoles. In such embodiments, preferably the linker comprises one or more groups selected from triazole (for example one or two (preferably two) triazoles, for example one or two 1,4-subtitued triazoles as described here), and , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4, for example 2 or 3); and the linker may optionally additionally comprises comprises two or more triazoles, and optionally one or more wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, andespecially 2, 3 or 4, for example 2 or 3); and optionally group.Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine). In another embodiment the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [C-terminal portion] in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). In one embodiment, the CD16a binding polypeptide may optionally comprise a further CD16a binding polypeptide such that the CD16a binding polypeptide is a CD16a binding oligomer. In one preferred embodiment the CD16a binding polypeptide does not comprise a further CD16a binding polypeptide (i.e. the a CD16a-binding polypeptide consists of a CD16a-binding motif and / or a CD16a- binding polypeptide). In certain embodiments, preferably A represents: -[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion], i.e. the CD16a-binding polypeptide comprises the following structure: In such embodiments the linker is attached to any amino acid of the indicated [N- terminal portion] of the CD16a binding polypeptide. Preferably, the linker is attached to the terminal amino acid of the indicated [N-terminal portion] of the CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine). In another embodiment the linker is attached to a non-terminal amino acid of the indicated [N-terminal portion] of the CD16a binding polypeptide, for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5). In embodiments wherein the CD16a-binding polypeptide comprises the following structure, (for example ) preferably each additional functional portion is an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). More preferably each additional functional portion is an additional binding moiety specific for BCMA. Even more preferably, each additional functional portion is an additional binding moiety specific for hBCMA that is a hBCMA binding polypeptide and which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion] the hBCMA binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]. Even more preferably, such a hBCMA binding polypeptide is a hBCMA binding polypeptide as defined in International Application No. PCT / EP2023 / 064625, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide). Therefore, in one preferred embodiment, the CD16a-binding polypeptide comprises the following structure, Wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; X represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N- terminal portion]; and Y represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N- terminal portion]; wherein each hBCMA N-terminal portion may have the same sequence or have different sequences; each hBCMA C-terminal portion may have the same sequence or have different sequences; each hBCMA separating portion may have the same sequence or have different sequences; each hBCMA Helix 1 portion may have the same sequence or have different sequences; and each hBCMA Helix 2 portion may have the same sequence or have different sequences; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide and attached to any amino acid of each indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. In such embodiments preferably the linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and the attached to terminal amino acid of the indicated [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. For example, the linker is attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine) of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide, and attached to the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine) of each indicated [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. In one very preferred embodiment, the linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid or the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine) of each indicated [hBCMA C-terminal portion] and / or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. In such embodiments preferably the linker comprises (or consists of) a group selected from the following group:

[0031] , . In such embodiments, it is especially preferred that the CD16a-binding polypeptide comprises the following structure: . In such embodiments the linker is attached to any amino acid of the indicated [N- terminal portion] of the CD16a binding polypeptide. In such embodiment, preferably X represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] and Y represents -[hBCMA N- terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]- [hBCMA C-terminal portion]; or -[hBCMA C-terminal portion]-[hBCMA Helix 2]- [hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N-terminal portion] and Y represents -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N-terminal portion]. In one embodiment, the CD16a binding polypeptide may optionally comprise a further CD16a binding polypeptide such that the CD16a binding polypeptide is a CD16a binding oligomer. In one preferred embodiment the CD16a binding polypeptide does not comprise a further CD16a binding polypeptide(i.e. the a CD16a-binding polypeptide consists of a CD16a-binding motif and / or a CD16a- binding polypeptide). In one preferred embodiment, the CD16a polypeptide comprises (or consists of) a compound selected from the group consisting of L17 to L28 and L31 to L37. In certain embodiments, a CD16a-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: ; and more preferably ; Wherein X represents an additional functional portion; and Y represents an additional functional portion; wherein each linker may be the same or different, and each additional functional portion may be the same or different; and wherein each linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide. A schematic representation of CD16a binding polypeptide according to this aspect of the invention is provided in Figure 17b, wherein each linker comprises a triazole. In such embodiments, preferably one linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion], and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] (for example attached to the side chain of a non- terminal lysine). For example, one linker is attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example a terminal lysine) of the indicated [C-terminal portion] or [N-terminal portion], and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] (for example attached to the side chain of a non-terminal lysine). In one preferred embodiment, one linker is attached to the terminus of the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion], and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5,or for example a lysine at X50of the [C-terminal portion] in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5. In another embodiment, one linker is attached to the side chain of the terminal amino acid (for example the side chain of the terminal lysine) of the indicated [C- terminal portion] or [N-terminal portion], and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N- terminal portion] (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50 of the [C-terminal portion] in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5. In another embodiment, both linkers are attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion], wherein one is attached to the terminus of the terminal amino acid of the [C-terminal portion] or [N-terminal portion], and one attached to the side chain of the terminal amino acid of the [C- terminal portion] or [N-terminal portion] (for example attached to the side chain of a terminal lysine). In certain embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, one linker is attached to the side-chain of a lysine at X4of the [N-terminal portion] and the other linker is attached to the N-terminus or a side-chain of a lysine at X1of the [N-terminal portion]. In certain embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, one linker is attached to the side-chain of a lysine at X50of the [C-terminal portion] and the other linker is attached to the C-terminus or a side-chain of a lysine at X58of the [C- terminal portion]. In such embodiments, the linker attached to the terminus of the terminal amino acid preferably comprises, or has, the following structure: . The linker may optionally additionally comprise one or more amino acid, for example 1 to 30 amino acids. For example the linker may further comprise one G, K or C amino acid and / or further comprises the sequence GGS, SGG, GGSGGS, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG. In such embodiments, the linker attached to the side-chain of the terminal amino acid or attached to the side-chain of the non-terminal amino acid of the [N-terminal portion] or the [C-terminal portion] comprises, or has, the following structure:

[0032] preferably wherein the terminal amino acid or the non-terminal amino acid is a lysine and the ester part of such a group is attached to the lysine side chain (for example attached to the NH2of the lysine side chain) of the terminal or non-terminal lysine of the [N-terminal portion] or [C-terminal portion]). The linker may optionally additionally comprise one or more amino acid, for example 1 to 30 amino acids. For example the linker may further comprise one G, K or C amino acid and / or further comprises the sequence GGS, SGG, GGSGGS, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG. In one embodiment, the CD16a binding polypeptide may optionally comprise a further CD16a binding polypeptide such that the CD16a binding polypeptide is a CD16a binding oligomer. In one preferred embodiment the CD16a binding polypeptide does not comprise a further CD16a binding polypeptide (i.e. the a CD16a-binding polypeptide consists of a CD16a-binding motif and / or a CD16a- binding polypeptide). In certain embodiments, the CD16a-binding polypeptide comprises the following structure: In such embodiments each linker is attached to any amino acid of the [N-terminal portion]. Preferably, one linker is attached to the terminal amino acid of the indicated [N-terminal portion], for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine) and the other linker is attached to a non-terminal amino acid of the indicated [N-terminal portion], for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5. In embodiments wherein the CD16a-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: or ; and more preferably ; preferably each additional functional portion is an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). More preferably each additional functional portion is an additional binding moiety specific for BCMA. Even more preferably, each additional functional portion is an additional binding moiety specific for hBCMA that is a hBCMA binding polypeptide and which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion] the hBCMA binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]. Even more preferably, such a hBCMA binding polypeptide is a hBCMA binding polypeptide as defined in International Application No. PCT / EP2023 / 064625, the contents of which are incorporated herein by reference. In such embodiments each linker is attached to any amino acid of the [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of the indicated hBCMA binding polypeptide. More preferably, each linker is attached to the terminal amino acid of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the indicated hBCMA binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example a terminal lysine) of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the indicated hBCMA binding polypeptide. Therefore, in one preferred embodiment, the CD16a-binding polypeptide comprises the following structure: ; and more preferably ; wherein X represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C- terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]- [hBCMA N-terminal portion]; and Y represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N- terminal portion]; wherein each hBCMA N-terminal portion may have the same sequence or have different sequences; each hBCMA C-terminal portion may have the same sequence or have different sequences; each hBCMA separating portion may have the same sequence or have different sequences; each hBCMA Helix 1 portion may have the same sequence or have different sequences; and each hBCMA Helix 2 portion may have the same sequence or have different sequences; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide and attached to any amino acid of each indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. In such embodiments preferably each linker comprises (or consists of) a group selected from the following group: The linker may optionally additionally comprise one or more amino acid, for example 1 to 30 amino acids. For example the linker may further comprise one G, K or C amino acid and / or further comprises the sequence GGS, SGG, GGSGGS, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG. In such embodiments, preferably one linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] (for example attached to the side chain of a non-terminal lysine) of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide. For example, one linker is attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example a terminal lysine) of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] (for example attached to the side chain of a non-terminal lysine) of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide. In one preferred embodiment, one linker is attached to the terminus of the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [C-terminal portion] of the CD16a binding polypeptide in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide. In another embodiment, one linker is attached to the side chain of the terminal amino acid (for example the side chain of the terminal lysine) of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [C-terminal portion] of the CD16a binding polypeptide in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide. In an alternative embodiment, one linker is attached to the terminus of the terminal amino acid (for example the side chain of the terminal lysine) of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide, and the other linker is attached to the side chain of the terminal amino acid (for example the side chain of the terminal lysine) of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of the hBCMA binding polypeptide. In one embodiment, the CD16a binding polypeptide may optionally comprise a further CD16a binding polypeptide such that the CD16a binding polypeptide is a CD16a binding oligomer. In one preferred embodiment the CD16a binding polypeptide does not comprise a further CD16a binding polypeptide (i.e. the a CD16a-binding polypeptide consists of a CD16a-binding motif and / or a CD16a- binding polypeptide). In one preferred embodiment, the CD16a polypeptide comprises (or consists of) a compound selected from the group consisting of L29 and L30. In certain other embodiments, a CD16a binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; X represents an additional functional portion; Y represents an additional functional portion; and Z represents an additional functional portion; and wherein the linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide. In such embodiments, for example, the linker may comprises one or more group selected from the group consisting of triazole (for example two, three or four triazole groups, for example 1,4-triazole groups), and , preferably wherein n is 1 to 30 (for example 1 to 24, 1 to 12, 1 to 10, 1 to 8, or 2 to 8, and especially 2, 3, 4, 8, 12 or 24)). In such embodiments the linker may additionally comprises

[0033] . Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] and [N-terminal portion] of the CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine). In another embodiment the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide, for example attached to the side chain of a non-terminal amino acid (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [N-terminal portion] in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [C-terminal portion] of the CD16a binding polypeptide in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). Preferably one, two or three (for example one or two) additional functional portions are each an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). More preferably each additional functional portion is an additional binding moiety specific for BCMA. Even more preferably, one, two or three (for example one or two) additional functional portion are each an additional binding moiety specific for hBCMA that is a hBCMA binding polypeptide and which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion] the hBCMA binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]. Even more preferably, such a hBCMA binding polypeptide is a hBCMA binding polypeptide as defined in International Application No. PCT / EP2023 / 064625, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide). Therefore, in one preferred embodiment, the CD16a-binding polypeptide comprises the following structure, Wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; X represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N- terminal portion]; and Y represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N- terminal portion]; And Z represents additional functional portion, or -[hBCMA N-terminal portion]- [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]-[hBCMA N-terminal portion]; wherein each hBCMA N-terminal portion may have the same sequence or have different sequences; each hBCMA C-terminal portion may have the same sequence or have different sequences; each hBCMA separating portion may have the same sequence or have different sequences; each hBCMA Helix 1 portion may have the same sequence or have different sequences; and each hBCMA Helix 2 portion may have the same sequence or have different sequences; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide and attached to any amino acid of each indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. In certain embodiments, a CD16a-binding oligomer of the present invention comprising an additional functional portion comprises the following structure: , , ,

[0034]

[0035] [N-terminal portion]-[Helix l]-[Separating portion]-[Helix 2]-[C-terminal portion] ; wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; when present, B represents -[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] or -[C-terminal portion]-[Helix 2]- [Separating portion]-[Helix 1]-[N-terminal portion]; X represents an additional functional portion; and, when present, Y represents an additional functional portion; wherein “linker”, “linker 1”, “linker 2” and “linker 3” are linkers as described here, and each “linker”, “linker 1”, “linker 2” and / or “linker 3” may be the same or different, wherein each linker (for example, “linker”, “linker 1”, “linker 2” and / or “linker 3”) is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide (and preferably each linker (for example, “linker”, “linker 1”, “linker 2” and / or “linker 3”) is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide). In such embodiments wherein two additional functional portions are attached (i.e. linked together) they are preferably separated by a linker, and more preferably wherein the linker is a linker as described herein. Preferably, “linker” comprises one or more groups selected from triazole, and wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4). Preferably, “linker 1” comprises one or more groups selected from triazole , wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4, for example 2 or 3) and . Preferably, “linker 2” comprises one or more groups selected from triazole. Preferably, “linker 3” comprises one or more groups selected from triazole, wherein n is 1 to 30 (for example 1 to 24, 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially In certain embodiments, the CD16a-binding oligomer comprising an additional functional portion comprises the following structure: (for example it has the structure [additional functional portion]-[linker]-[N- terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]); (for example it has the structure [additional functional portion]-[additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]); , ,

[0036] wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]- [N-terminal portion]; B represents -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]; X represents an additional functional portion; and, when present, Y represents an additional functional portion; each the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide (and preferably each linker is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each CD16a binding polypeptide, for example attached to the terminus of the terminal amino acid or attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine)) wherein each linker is a linker as described here and each linker may be the same or different; each N-terminal portion may have the same sequence or have different sequences; each C-terminal portion may have the same sequence or have different sequences; each separating portion may have the same sequence or have different sequences; each Helix 1 portion may have the same sequence or have different sequences; and each Helix 2 portion may have the same sequence or have different sequences. In certain embodiments, each additional functional portion of a CD16a-binding oligomer comprising an additional functional portion of the present invention is an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA). More preferably each additional functional portion is an additional binding moiety specific for BCMA. Even more preferably, each additional functional portion is an additional binding moiety specific for hBCMA that is a hBCMA binding polypeptide and which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion] the hBCMA binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]. Even more preferably, such a hBCMA binding polypeptide is a hBCMA binding polypeptide as defined in International Application No. PCT / EP2023 / 064625, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [hBCMA C- terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide). In such embodiments, X represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]- [hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C-terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]- [hBCMA Helix 1]-[hBCMA N-terminal portion]; and when present,Y represents -[hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2]-[hBCMA C-terminal portion] or -[hBCMA C- terminal portion]-[hBCMA Helix 2]-[hBCMA Separating portion]-[hBCMA Helix 1]- [hBCMA N-terminal portion]; wherein each hBCMA N-terminal portion may have the same sequence or have different sequences; each hBCMA C-terminal portion may have the same sequence or have different sequences; each hBCMA separating portion may have the same sequence or have different sequences; each hBCMA Helix 1 portion may have the same sequence or have different sequences; and each hBCMA Helix 2 portion may have the same sequence or have different sequences; and the linker or a linker (for example “linker”, “linker 1”, “linker 2” or “linker 3”) is attached to any amino acid of each indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. Preferably, the linker or a linker (for example “linker”, “linker 1”, “linker 2” or “linker 3”) is attached to a terminal amino acid or the side chain of a terminal amino acid (for example attached to the side chain of a terminal lysine) of the indicated [hBCMA C-terminal portion] or [hBCMA N-terminal portion] of each hBCMA binding polypeptide. In certain embodiments, a CD16a-binding oligomer of the present invention comprising an additional functional portion comprises at least three CD16a-binding polypeptides, and comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[N-terminal portion]-[Helix 2]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]-[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]- [additional functional portion]; [additional functional portion]-[additional functional portion]-[linker]-[N- terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[N-terminal portion]-[Helix 2]-[Separating portion]-[Helix 2]-[C- terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; wherein each linker is a linker as described here and each linker may be the same or different, or two linkers may be the same and one be different; each N-terminal portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each C-terminal portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each separating portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; each Helix 1 portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence; and each Helix 2 portion may have the same sequence, have different sequences, or two may have the same sequence and one may have a different sequence. In such embodiments, each linker is preferably different; and wherein each linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of each CD16a binding polypeptide (and preferably each linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of each CD16a binding polypeptide). In such embodiments, more preferably the CD16a-binding oligomer comprises the following structure: [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[N-terminal portion]-[Helix 2]-[Separating portion]-[Helix 2]-[C-terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or [additional functional portion]-[additional functional portion]-[linker]-[N- terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]- [Linker]-[N-terminal portion]-[Helix 2]-[Separating portion]-[Helix 2]-[C- terminal portion]-[Linker]- [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]. In the above embodiments defining the structure of the CD16a-binding polypeptide or CD16a-binding oligomer comprising an additional functional portion, each additional functional portion may be any one described herein. For example, each additional functional portion may be independently selected from an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or an immune cell target, for example a NK cell target); and an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. For example, each additional functional portion may be independently selected from an additional binding moiety specific for a cancer cell surface target (for example a myeloma cell surface antigen, for example BCMA); an additional binding moiety specific for an immune cell target (for example a NK cell target); and an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. For example, each additional functional portion may be independently selected from an additional binding moiety specific for BCMA; an additional binding moiety specific for a NK cell target; and an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. For example, each additional functional portion may be independently selected from an additional binding moiety specific for BCMA; and an additional binding moiety specific for a NK cell target; and an a cytokine, for example IL-15 or derivatives thereof. For example, each additional functional portion may be independently selected from an additional binding moiety specific for BCMA; and an additional binding moiety specific for a NK cell target; and IL-15 or derivatives thereof. In one preferred embodiment, each additional functional portion may be independently selected from an additional binding moiety specific for BCMA; and an additional binding moiety specific for a NK cell target; and an a cytokine, for example IL-15 or derivatives thereof. In one preferred embodiment, each additional functional portion may be independently selected from an additional binding moiety specific for BCMA; and an additional binding moiety specific for a NK cell target. In one preferred embodiment, each additional functional portion is an additional binding moiety specific for BCMA. In the above embodiments defining the structure of the CD16a-binding polypeptide or CD16a-binding oligomer comprising an additional functional portion, each additional functional portion may be an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA). For example, each additional functional portion may be an additional binding moiety for BCMA. In a preferred embodiment, an additional binding moiety for BCMA is a hBCMA- binding polypeptide which comprises at least one motif that binds to hBCMA, wherein said hBCMA binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the hBCMA binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]. For example, it is a hBCMA-binding polypeptide as defined in the International Application No. PCT / EP2023 / 064625. The contents of that PCT application are herein incorporated by reference. In particular, the hBCMA-binding polypeptide is one wherein: i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35, wherein, independently from each other, a) X9and X10are any naturally occurring amino acid; X11is E, F, H, Q, T or Y; X14is any naturally occurring amino acid; X17is A, E, Q, S, T or V; X18is any naturally occurring amino acid; X25 is F or Y; X31 is I, M, or V; X33 is K or S; X35 is I, L, M, or V; or ii) Helix 1 and Helix 2 are defined as in i), wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example at least 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue. For example, the hBCMA-binding polypeptide is one with hBCMA binding efficacy is at least 1% of the sequence VDNKFNKENQFADEEIAALPNLNFYQKWAFIRKLMDDPSQSANLLAEAKKLNDAQAP K [SEQ ID 226]. In a very preferred embodiment, the hBCMA-binding polypeptide is the polypeptide of SEQ ID 226. In another very preferred embodiment, the hBCMA-binding polypeptide is a polypeptide comprising (or having) a sequence selected from the group consisting of SEQ ID No.273-281 (Example sequences 1027 to 1035) of Figure 23 and a sequence of Table A below, or a derivative thereof (for example wherein from 1 to 5 (for example 1, 2 or 3 amino acid residues) are replaced by an alternative residue, for example a different naturally occurring amino acid or a different unnatural amino acid; or a different naturally occurring amino acid excluding methionine or a different unnatural amino acid). Table A: hBCMA-binding polypeptide sequences

[0037] In another very preferred embodiment, the hBCMA-binding polypeptide is a polypeptide comprising a sequence selected from the group consisting of SEQ ID No. 282-288 (Example sequences 1036 to 1042) of Figure 24 and a sequence of Table B below, or a derivative thereof (for example wherein from 1 to 5 (for example 1, 2 or 3 amino acid residues) are be replaced by an alternative residue, for example a different naturally occurring amino acid or a different unnatural amino acid; or a different naturally occurring amino acid excluding methionine or a different unnatural amino acid). Table B: hBCMA-binding motif sequences

[0038] The invention further provides a hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix 2]-[hBCMA C-terminal portion], the hBCMA-binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion ]-[hBCMA Helix 2], wherein the sequence of the CD-16a-binding motif is selected from SEQ ID NOs 282 to 288 (Example IDs 1036 to 1042). The invention further provides a hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, wherein said polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]- [hBCMA Helix]-[hBCMA C-terminal portion], the hBCMA-binding motif being the portion [hBCMA Helix 1]-[hBCMA Separating portion]-[hBCMA Helix 2], wherein the sequence of the hBCMA-binding polypeptide is selected from SEQ ID NOs: 273 to 281 (Example IDs 1027 to 1035). The multi-specific engagers of the invention may demonstrate “bi-paratopic binding” or a “bi-paratopic effect”. This is demonstrated where two domains of a CD16a- binding polypeptide according to the present invention both contribute to CD16a- binding. The present invention, therefore, further provides dimeric engagers comprising two CD16a domains which demonstrate bi-paratopic binding. CD16a binder-drug conjugates Alternatively or additionally, a CD16a binding polypeptide or CD16a -binding oligomer as disclosed herein may be attached to a therapeutic agent to form a CD16a binder-drug conjugate. Therefore, in an embodiment, the at least one CD16a binding polypeptide or CD16a-binding oligomer is typically covalently attached to one or more therapeutic agent(s), optionally via a linker or linkers, for example a linker or linkers as described above. Non-limiting examples of such therapeutic agents include cytotoxic drugs, for example mitomycin C, desmethyltopotecan, SN- 38, MMAE, MMAF, doxorubicin, pyrrolobenzodiazepine, amanitin, maytansinoids (for example maytansinoid DM1 or maytansinoid DM4), or duostatins (for example duostatin 5.2). For the avoidance of doubt, during the generation of a CD16a binder-drug conjugate according to the invention, the one or more therapeutic agent(s) (for example MMAF) is necessarily modified by the reaction between the functional group at the point of attachment (for example –NH, –OH or –SH (for example in a Cys)) and any attachment groups or linkers used. The skilled person will therefore understand that the therapeutic agent in a CD16a binder-drug conjugate (for example a CD16a binder-MMAF conjugate) comprises such a modification. Polypeptide-oligonucleotide conjugates Alternatively or additionally, a CD16a binding polypeptide or CD16a -binding oligomer as disclosed herein may be attached to an oligonucleotide. The oligonucleotide can be a single- or double-stranded DNA, RNA or PNA molecule. The function of the oligonucleotide could be as a messenger, antisense, interference or guide to be used for gene expression regulation or specific gene editing purposes. Polypeptide production The polypeptides and oligomers of the invention can be manufactured using methods known in the art. For example, they can be prepared by chemical synthesis methods or by recombinant protein production techniques in, for example, bacterial, yeast, insect, fungal, plant or mammalian cells. Preferably, they are prepared by chemical synthesis, for example by solid phase synthesis. Linkers of the present invention may be synthesised according to methods known in the art, for example as described in Bird, R. E., et al, Bioconjugate Chem, 2021, 32, 2457 – 2479; Forte, N., et al, DDTEC 2018, 562, Neumann, S., et al, Marcomol. Rapid Commun.2020, 41, 1900359, and Blackman, M. L., et al, J. Am. Chem. Soc..2008, 130, 13518-13519. Polypeptides and oligomers of the invention may also be fused, via recombinant or chemical synthesis techniques (preferably by chemical synthesis techniques) as described above, to a different molecule with therapeutic potential, for example an immunoglobulin with therapeutic potential. Derivatives, Salts and Solvates The present invention provides polypeptides and oligomers, derivatives of such polypeptides and oligomers, and salts or solvates of such polypeptides and oligomers, and derivatives thereof. Whilst in some embodiments, the invention relates to a polypeptide or oligomer of the invention and is not a derivative, in other embodiments the invention relates to a derivative of a polypeptide and oligomer of the invention. The derivative may for example comprise one or more derivatisations selected from amidation and / or acylation. In certain embodiments it is preferred that the polypeptides and oligomers of the invention may be amidated at their C-terminal. Such a modification is very common in nature with approximately half of naturally occurring peptides being susceptible to amidation at their C-terminal. The present invention encompasses all of the generic and specific sequences disclosed herein, including in the sequence listing and drawings and examples, in both amidated and non-amidated forms, the amidation, where present being especially preferred on the C-terminal of the peptide sequence. In certain embodiments it is preferred that the polypeptides and oligomers of the invention may be acylated at their N-terminal. The present invention encompasses all of the generic and specific sequences disclosed herein, including in the sequence listing and drawings and examples, in both acylated and non-acylated forms, the acetylation, where present being especially preferred on the N-terminal of the peptide sequence. Salt forms of the polypeptides and oligomers of the invention, and of derivatives of such polypeptides and oligomers, also form part of the invention. In some embodiments the salt is a salt of a polypeptide or oligomer of the invention. In other embodiments the salt is a salt of a derivative of polypeptide or oligomer of the invention. Salts of polypeptide or oligomer of the invention include those which are pharmaceutically acceptable, i.e. which are suitable for use in medicine. However, salts having non-pharmaceutically acceptable counterions are also within the scope of the present invention, for example, for use as intermediates in the preparation of the polypeptide or oligomer of the invention. Suitable salts according to the invention include those formed with organic or inorganic acids or bases. Pharmaceutically acceptable acid addition salts include those formed with hydrochloric, hydrobromic, sulphuric, nitric, citric, tartaric, acetic, phosphoric, lactic, pyruvic, acetic, trifluoroacetic, succinic, perchloric, fumaric, maleic, glycolic, salicylic, oxaloacetic, methanesulfonic, ethanesulfonic, p- toluenesulfonic, formic, benzoic, malonic, naphthalene-2-sulfonic, benzenesulfonic, and isethionic acids. Other acids such as oxalic acid may be useful as intermediates in obtaining the compounds of the invention in final form. Pharmaceutically acceptable salts with bases include ammonium salts, alkali metal salts, for example potassium and sodium salts, alkaline earth metal salts, for example calcium and magnesium salts, and salts with organic bases, for example dicyclohexylamine and N-methyl-D-glucomine. More preferably, the salt of a polypeptide, oligomer or derivative of the present invention is the hydrochloride salt, trifluoroacetate salt or acetate salt (i.e. the addition salt formed from hydrochloric acid, trifluoroacetic acid or acetic acid). More preferably, the salt is the acetate salt. Those skilled in the art of organic and / or medicinal chemistry will appreciate that many organic compounds can form complexes with solvents in which they are reacted or from which they are precipitated or crystallized. Such complexes are known as "solvates". For example, a complex with water is known as a "hydrate". The invention also encompasses solvates of the polypeptides and oligomers of the present invention, solvates of derivatives of the polypeptides and oligomers of the present invention, and solvates of salts of the derivatives. Those skilled in the art of organic and / or medicinal chemistry will also appreciate than many organic compounds can exist in different forms, including as amorphous material and / or in one or more crystalline forms. Different physical forms of organic compounds are known as polymorphs. The invention also encompasses all such different physical forms of the polypeptides and derivatives of the invention, as well as different physical forms of their derivatives and salts. Modulation of polypeptide properties The pharmacokinetic properties of the polypeptides of the invention can be modulated by methods known in the art. For example, they can be linked to a moiety extending the plasma half-life, such as a polyethylene glycol polymer, an unstructured polypeptide (such as XTEN or PAS), or an FcRn binding ligand such as serum albumin or the Fc domain of an immunoglobulin. Formulations Polypeptides according to the invention (for example, a CD16a-binding polypeptide or CD16a-binding oligomer of the present invention, or a CD16a binder-drug conjugate) may be present in a formulation and particularly in a pharmaceutical formulation. In certain embodiments, the invention provides a nucleic acid molecule encoding the CD16a-binding polypeptide or CD16a-binding oligomer of the invention wherein the CD16a-binding polypeptide or CD16a-binding oligomer of the invention comprises a CD16a binding motif of SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044) or comprises or consists of a sequence of SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043). Such a nucleic acid molecule encoding the CD16a-binding polypeptide or CD16a-binding oligomer of the invention may be used as a medicament, for example may be used for the treatment of cancer. The nucleic acid molecule may, for example, be a DNA or an RNA molecule, for example a mRNA molecule. Nucleic acid molecules according to the invention may be present in a formulation and particularly in a pharmaceutical formulation. As such, the present invention further provides a formulation and particularly in a pharmaceutical formulation of a nucleic acid molecule (for example, a DNA or RNA, and in particular a mRNA molecule) encoding the CD16a-binding polypeptide or CD16a-binding oligomer of the invention. Pharmaceutical formulations include for example those suitable for oral, parenteral (including subcutaneous, intradermal, intraosseous infusion, intramuscular, intravascular (bolus or infusion), and intramedullary), or intraperitoneal administration, although the most suitable route may depend upon, for example, the condition and disorder of the subject under treatment. In one embodiment of the invention, a CD16a binding polypeptide or CD16a binding oligomer (in particular a CD16a binder-drug conjugate) or nucleic acids (for example DNA or RNA molecules of the present invention, for example an mRNA molecule) according to the invention is administered as a pharmaceutical formulation suitable for oral or parenteral (including subcutaneous, intradermal, intraosseous infusion, intramuscular, intravascular (bolus or infusion), and intramedullary) administration. Pharmaceutical formulations suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution or a suspension in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion. Peptides of the invention may also be presented as a bolus, electuary or paste. Various pharmaceutically acceptable carriers and their formulation are described in standard formulation treatises, e.g., Remington's Pharmaceutical Sciences by E. W. Martin. See also Wang, Y. J. and Hanson, M. A., Journal of Parenteral Science and Technology, Technical Report No. 10, Supp.42:2S, 1988. Formulations for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. Preferably, the formulations may be presented in unit dosage or divided dosage containers, for example sealed ampoules and vials. The formulation may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example saline, a physiologically acceptable solution or water-for-injection, immediately prior to use. Extemporaneous injection and infusion solutions and suspensions may be prepared from sterile powders, granules or other dry composition. Exemplary compositions for parenteral administration include injectable solutions or suspensions which can contain, for example, suitable non-toxic, parenterally acceptable diluents or solvents, such as mannitol, 1,3-butanediol, water, Ringer’s solution, an isotonic sodium chloride solution, or other suitable dispersing or wetting and suspending agents, including synthetic mono- or diglycerides, and fatty acids, including oleic acid, or Cremaphor. Dosage regimens A CD16a-binding polypeptide or CD16a binding oligomer (in particular a CD16a binder-drug conjugate) of the invention, and a pharmaceutical formulation comprising such a polypeptide, oligomer or binder-drug conjugate, or nucleic acid molecules of the invention (for example, DNA or RNA molecules of the present invention, for example a mRNA molecule of the present invention), and pharmaceutical formulations comprising those nucleic acid molecules, find use in the treatment and / or prophylaxis of cancer, for example multiple myeloma. The amount of a CD16a-binding polypeptide or CD16a binding oligomer (in particular a CD16a binder-drug conjugate) or nucleic acid molecule, required to achieve a therapeutic effect will vary with the particular route of administration and the characteristics of the subject under treatment, for example the species, age, weight, sex, medical conditions, the particular disease and its severity, and other relevant medical and physical factors. An ordinarily skilled physician can readily determine and administer the effective amount of the CD16a-binding polypeptide, CD16a oligomer, CD16a binder-drug conjugate and / or composition comprising the same, or nucleic acid molecule and / or composition comprising the same, required for treatment and / or prophylaxis of cancer. A CD16a-binding polypeptide, CD16a binding oligomer (in particular a CD16a binder- drug conjugate) or nucleic acid molecule of the invention, or a pharmaceutical formulation thereof, may for example be administered daily, weekly, every second, third or fourth week or even as a high single dose depending on the subject and severity of the cancer to be treated. A CD16a-binding polypeptide, CD16a binding oligomer (in particular a CD16a binder- drug conjugate) or nucleic acid molecule of the invention, or a pharmaceutical formulation thereof, may for example be administered as a parenteral or oral dosage. Parenteral administration includes intravenous (into a vein, for example a central or a peripheral vein, bolus or infusion), intra-arterial (into an artery, for example a central or a peripheral artery), intraosseous infusion (into the bone marrow), intra-muscular (into muscle), intradermal (into the dermis), and subcutaneous (under the skin) administration. In one preferred embodiment, the dosage of the present invention is administered intravenously or intra-arterially, and more preferably by intravenous infusion (for example central intravenous infusion or peripheral intravenous infusion). In another preferred embodiment, the dosage of the present invention is administered by subcutaneous injection. As such, pharmaceutical formulations especially useful for the present invention are those suitable for intravenous administration, more especially intravenous infusion, or subcutaneous administration. A CD16a-binding polypeptide, CD16a binding oligomer (in particular a CD16a binder- drug conjugate) or nucleic acid molecule of the invention, and pharmaceutical formulations thereof, may be administered as part of a treatment cycle. In a treatment cycle, said polypeptides may be administered on day 1 of the cycle, wherein the cycle lasts X days, with no further administration of the CD16a-binding polypeptides or CD16a-binding oligomers of the invention for the next X-1 days. X may be, for example, from 1 to 42, for example from 2 to 14 days. Alternatively, the CD16a-binding polypeptides or CD16a-binding oligomers may be administered as a split dose, for example on for example on days 1 and 2 of the cycle. The cycle may be repeated one or several times depending on the category, class or stage of the cancer to be treated. For example, the cycle may be repeated from 1 to 100 times, for example from 2 to 50 times, for example 8 to 40 times, for example 8 or 16 times. For example, the CD16a-binding polypeptides or CD16a-binding oligomers or nucleic acid molecules of the invention may be administered for 8 repeats of a 7 day cycle, followed by 16 repeats of a 14 day cycle, optionally followed by further repeats of a 28 day cycle. An ordinarily skilled physician or clinician can readily determine the number of cycles of CD16a-binding polypeptide (for example CD16a binder-drug conjugate) required to prevent, counter or arrest the progress of the cancer. Combination treatments Whilst a CD16a-binding polypeptide or CD16a binding oligomer (in particular a CD16a binder-drug conjugate) or nucleic acid molecules disclosed herein may be used as the sole active ingredient in the present invention, it is also possible for it to be used in combination with one or more further therapeutic agent(s), and the use of such combinations provides one embodiment of the invention. Such further therapeutic agents may be agents useful in the treatment and / or prophylaxis of cancer, or other pharmaceutically active materials. Such agents are known in the art Non-limiting examples of further therapeutic agents for use in the present invention may include proteasome inhibitors (PIs) (for example carfilzomib, bortezomib or ixazomib), immunomodulatory agents (IMiDs) (for example lenalidomide, thalidomide or pomalidomide), alkylators (for example cyclophosphamide, melphalan, bendamustine or melflufen), anthracyclines (for example doxorubicin), steroids (for example dexamethasone, prednisone or prednisolone), BCL-2 inhibitors (for example venetoclax), histone deacetylase (HDAC) inhibitors (for example panobinostat), anti-CD38 agents (for example daratumumab or isatuximab), immune checkpoint inhibitors (for example a CTLA-4 inhibitor, a PD-1 inhibitor, or a PD-L1 inhibitor), or ADAM17 inhibitors. For example, further therapeutic agents may be selected from proteasome inhibitors (for example carfilzomib or bortezomib), immunomodulatory agents (for example lenalidomide or thalidomide), alkylators (for example melphalan or melfufen), steroids (for example dexamethasone or prednisone), anti-CD38 agents (for example daratumumab), an immune checkpoint inhibitor (for example a CTLA-4 inhibitor, a PD-1 inhibitor, or a PD-L1 inhibitor), and an ADAM17 inhibitor. The one or more further therapeutic agent(s) may be used simultaneously, sequentially or separately with / from the administration of the dosage of CD16a binding polypeptides, CD16a binding oligomers, CD16a binder-drug conjugates, or nucleic acid molecules of the invention. The individual components of such combinations can be administered separately at different times during the course of therapy or concurrently in divided or single combination forms. In an embodiment of the invention, the one or more further therapeutic agent(s) are selected from a PI, an IMiD, and a steroid. For example, the one or more further therapeutic agents are a PI (for example bortezomib or carfilzomib), an IMiD (for example lenalidomide, thalidomide and pomalidomide), and a steroid (for example, prednisone, prednisolone and dexamethasone). Preferably, the one or more therapeutic agents are bortezomib, thalidomide, and dexamethasone. In an embodiment of the invention, the one or more further therapeutic agent(s) are selected from a PI, an alkylator, and a steroid. For example, the one or more further therapeutic ag...

Claims

Claims 1. A CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and which further comprises at least one additional functional portion, wherein the CD16a-binding polypeptide and an additional functional portion are separated by a linker, wherein the or each linker comprises one or more groups selected from the group consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooxtane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione,wherein n is 1 to 30,wherein m is 12. A CD16a-binding oligomer, which comprises at least two CD16a-binding polypeptides, wherein each CD16a-binding polypeptide comprises at least one motifthat binds to CD16a, and wherein each CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2]; and wherein the CD16a-binding polypeptides are each separated by a linker, wherein the or each linker comprises one or more groups selected from the group consisting of triazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooctane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione,wherein n is 1 to 30,wherein m is 1and wherein the CD16a-binding oligomer optionally further comprises at least one additional functional portion, wherein the CD16a-binding oligomer and an additional functional portion are separated by a linker, and wherein the or each linker comprises one or more groups selected from the groups consisting oftriazole (for example a 1,4- or 1,5-substituted triazole), a bicyclic ring comprising a triazole ring (for example a triazole fused cyclooctane, mono- or di- fluorocyclooctane), a tricyclic ring comprising a triazole ring (for example a triazole fused bicyclononane), a tetracyclic ring comprising a triazole ring (for example a triazole fused dibenzocyclooctane or dibenzoazacyclooctane ring), a bicyclic ring comprising a pyridazine ring (for example a pyridazine fused cyclooctane), a tricyclic ring comprising a pyridazine ring (for example pyridazine fused bicyclononane), 1H- pyrrole-2,5-dione,wherein n is 1 to 30,wherein m is 13. The CD16a-binding polypeptide as claimed in claim 1, or the CD16a-binding oligomer as claimed in claim 2, wherein the or each CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]-[Helix 2], and wherein Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, [SEQ ID NO 120] wherein, a) X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14 is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R;X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, M, R or S; or b) X9is V; X10is Q; X11is M; X13is Q; X14is F; X17is R; X18is K; X24is H; X25is H; X27is S; X28is F; X31is I; X32is K; X33is S and X35is M, and optionally wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least at least 1 and no more than 5 (for example 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue; or c) X9is Q; X10is F; X11is Y; X13is R; X14is D; X17is D; X18is L; X24is E; X25is D; X27is K; X28is W; X31is Y; X32is M; X33is S and X35is I, and optionally wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example at least 1 and no more than 3) of the residues not labelled as Xn are replaced by an alternative residue; or d) X9is F; X10is W; X11is I; X13is E; X14is S; X17is E; X18is S; X24is I; X25is Y; X27is K; X28is W; X31is K; X32is Y; X33is S and X35is A, and optionally wherein within Helix 1 and Helix 2, at least 1 and no more than 5 (for example at least 1 and no more than 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 5 (for example at least 1 and no more than 3) of the residues not labelled as Xnare replaced by an alternative residue.

4. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 3, wherein: Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18[SEQ ID NO 127] and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35, [SEQ ID NO 120] wherein, X9is A, D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is A, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is Q or R; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is A or H; X27is A, I, K, Q, R, S, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, M, R or S.

5. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 3 or 4, wherein: Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18[SEQ ID NO 127] and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35[SEQ ID NO 120], wherein, X9 is D, F, H, I, K, L, Q, R, T, V or Y; X10 is Q; X11 is A, D, E, F, H, I, K, L, M, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is F, H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R or Q; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is H or A; X27is A, I, K, Q, R, T, S or V; X28 is F or Y; X31 is I or L; X32 is A, E, H, K, L, N, Q or R; X33 is K or S; and X35is A, H, I, L, M, R or S.

6. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 5, wherein: Helix 1 comprises the sequence X9X10X11AX13X14EIX17X18[SEQ ID NO 127] and Helix 2 comprises the sequence X24X25QX27X28AFX31X32X33LX35[SEQ ID NO 120], wherein,X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N Q, R, S, T, V, W or Y; X13is A, Q or V; X14is H, I, K, L, N, Q, R, S, T, V, W or Y; X17is R or Q; X18is A, D, E, F, H, I, K, N, Q, R, S, T or V; X24is H; X25is H or A; X27is A, I, K, Q, R, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, L, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S.

7. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is D, F, H, I, K, L, Q, R, T, V, or Y; X10is Q; X11is A, D, E, F, H, I, K, N, Q, R, S, T, V, W or Y; X13is A, Q or V; X14is H, I, K, L, N, Q, R, S, V, W, or Y; X17is R; X18is A, D, E, F, H, K, N, Q, R, S or T; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is H, I, L, R or S.

8. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is D, F, H, I, K, L, Q, T, V, or Y; X10is Q; X11is A, D, E, F, H, I, K, L, N, Q, R, S, T, V, W or Y; X13is A or Q; X14is H, I, K, L, Q, R, S, T, V, W or Y; X17is R; X18is A, D, E, F, H, K, N, Q, R, S, T or V; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F or Y; X31 is I or L; X32 is A, E, H, K, N, Q or R; X33 is K or S; and X35 is A, H, I, L or R.

9. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is D, F, H, I, K, L, Q, R, T, V or Y; X10is Q; X11is A, D, E, F, H, I, K, N, Q, R, S, T, V, W or Y; X13is A or Q; X14is H, I, K, L, Q, R, S, V, W or Y; X17is R; X18is A, F, H, K, N, Q, R, S or T; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F or Y; X31is I or L; X32is E, H, K, N, Q or R; X33is K or S; and X35is A, H, I, L, R or S.

10. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein:X9is F, L, Q, T or Y; X10is Q; X11is A, F, H, I, L, N, Q, S or Y; X13is A or Q; X14is I, K, Q, R or V; X17is R; X18is A, E, H, K, Q, R, T or V; X24is H; X25is H; X27is A, I, K, Q, R or V; X28is F; X31is I; X32is A, H, K, N, Q or R; X33is K or S; and X35is H, I or L.

11. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is I, L, Q, T or V; X10is Q; X11is A, E, F, H, I, S, V or Y; X13is Q; X14is K, L, R, V, W or Y; X17is R; X18is A, H, K, Q, R, S or T; X24is H; X25is H; X27is I, K, Q, R, T or V; X28is F; X31is I or L; X32is K, N or R; X33is K or S; and X35is I or L.

12. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is I, L, Q or V; X10is Q; X11is A, E, H, I, S, W or Y; X13is Q; X14is K, L, R, V, W or Y;X17is R; X18is A, H, K, Q, R, S or T; X24is H; X25is H; X27is K, Q, R, T or V; X28is F; X31is I; X32is K, N or R; X33is K or S; and X35is I or L; for example wherein: X9is I, L, Q or V; X10is Q; X11is A, E, H, I, S or Y; X13is Q; X14is K, L, R, V, W or Y;X17is R; X18is H, K, Q, R, S or T; X24is H; X25is H; X27is K, Q, R, T or V; X28is F; X31 is I; X32 is N or K; X33 is K or S; and X35 is I or L.

13. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is L or V; X10is Q; X11is A, I, S or Y; X13is Q; X14is K, R or V; X17is R; X18is K, Q, R, S or T; X24is H; X25is H; X27is K, R or V; X28is F; X31is I; X32is N or K; X33is K or S; and X35is I or L.

14. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein:X9is D, H, I, K, L, Q, T or V; X10is Q; X11is A, D, E, F, H, I, K, N, R, S, V, W or Y; X13is Q; X14is K, L, Q, R, S, V, W or Y; X17is R; X18is A, H, K, N, Q, R, S or T; X24is H; X25is H; X27is A, I, K, Q, R, T or V; X28is F or Y; X31is I or L; X32is A, E, H, K, N, Q or R; X33is K or S; and X35is A, I, L, or R; or X9is K, Q or Y; X10is Q; X11is I or Q; X13is Q;X14is W or Y; X17is R; X18is H, K or R; X24is H; X25is H; X27is A, K or T; X28is F; X31is I; X32is A, K or Q; X33is K or S; and X35is I or L; or X9is L, V or Y; X10is Q; X11is I, N or Q; X13is Q;X14is K, R or Q; X17is R; X18is E, A or V; X24is H; X25is H; X27is K or Q; X28is F; X31is I; X32is H, K or Q; X33is K or S; and X35is I or L.

15. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 6, wherein: X9is L, Q, T or V; X10is Q; X11is I, V or Y; X13is Q; X14is K, R or Y; X17is R; X18 is K, R, S or T; X24 is H; X25 is H; X27 is I, T or V; X28 is F; X31 is I or L; X32 is K or N; X33is K or S; and X35is I or L; for example wherein X9 is L, T or V; X10 is Q; X11 is I, V, or Y; X13 is Q;X14 is K or R; X17is R; X18is R, S or T; X24is H; X25is H; X27is I or V; X28is F; X31is I or L; X32is K or N; X33is K; and X35is I or L.

16. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 3, wherein: X9is L, Q or V; X10is Q; X11is H, I, M, N or Y (preferably H, I, N or Y); X13is Q; X14is F, K, R or Y; X17is R; X18is A, K, Q, R or S; X24is H; X25is H; X27is Q, S, T or V; X28is F; X31is I; X32is A, H, K or N; X33is K or S; and X35is I, L or M; and more preferably wherein, X9is L, Q or V; X10is Q; X11is I, M, N or Y (preferably I, N or Y); X13is Q; X14is F, K, R or Y; X17is R; X18is A, K, R or S; X24is H; X25is H; X27is Q, S, T or V; X28is F; X31is I; X32is H, K or N; X33is K or S; and X35is I, L or M; and most preferably wherein X9is L, Q or V; X10is Q; X11is I, M or N (preferably I or N); X13is Q; X14is F, R or Y; X17is R; X18is A, K or R; X24is H; X25is H; X27is Q, S, or T; X28is F; X31is I; X32is H or K; X33is K or S; and X35is I, L or M.

17. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 16, wherein X18is R.

18. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 17, wherein the CD16a binding efficacy is at least 10% of SEQ ID NO: 1; and / or wherein the or each CD16a-binding polypeptide competes with SEQ ID NO:

1.

19. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 17, wherein: Helix 1 comprises the sequence X6X7X8X9X10X11AX13X14EIX17X18X19and / or Helix 2 comprises the sequence X23X24X25QX27X28AFX31X32X33LX35X36X37[SEQ ID NO 128], wherein, X6is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N) or is absent; X7 is any naturally occurring amino acid (preferably H, K or R; more preferably K) or is absent; X8is any naturally occurring amino acid (preferably D, E, N or Q; more preferably E) or is absent; X19is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably L) or is absent; X23is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N) or is absent;X36is any naturally occurring amino acid (preferably D, E, N or Q; more preferably D) or is absent; and X37is any naturally occurring amino acid (preferably D, E, N or Q; more preferably D) or is absent; and preferably wherein X6is N; X7is K; and X8is E; and / or wherein X36is D; and X37is D; for example wherein X6is N; X7is K; X8is E; X19is L; X23is N; X36is D; and X37is D.

20. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 5, wherein: Helix 1 comprises the sequence NKEVQMAQFEIRKL [SEQ ID NO 129] and Helix 2 comprises the sequence NHHQSFAFIKSLMDD [SEQ ID NO 130]; and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5) (for example, at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement); and, for example, wherein the CD16a binding efficacy is at least 10% of SEQ ID NO: 1; and / or wherein the or each CD16a- binding polypeptide competes with SEQ ID NO:

1.

21. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 3, wherein: Helix 1 comprises the sequence NKEQFYARDEIDLL [SEQ ID NO 131] and Helix 2 comprises the sequence NEDQKWAFYMSLIDD [SEQ ID NO 132]; and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5) (for example, at least 1 and no more than 3 (for example 1, 2, or 3)) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement); and, for example, wherein the CD16a bindingefficacy is at least 10% of SEQ ID NO: 74; and / or wherein the or each CD16a- binding polypeptide competes with SEQ ID NO:

74.

22. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 3, wherein: Helix 1 comprises the sequence NKEFWIAESEIESL [SEQ ID NO 133] and Helix 2 comprises the sequence NIYQKWAFKYSLADD [SEQ ID NO 134]; and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5) (for example, at least 1 and no more than 3 (for example 1, 2, or 3) residues in the sequence of Helix 1 and / or Helix 2 are replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement); and, for example, wherein the CD16a binding efficacy is at least 10% of SEQ ID NO: 75; and / or wherein the or each CD16a- binding polypeptide competes with SEQ ID NO:

75.

23. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 22, wherein the separating portion is a sequence of 1 to 5 (preferably 2 to 5, for example 2, 3, 4 or 5; or for example 3 to 5, for example 3, 4 or 5, and more preferably 3) naturally occurring amino acids.

24. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 23, wherein the separating portion has the sequence X20X21X22, wherein X20is any naturally occurring amino acid (preferably S, T, M, P, F, Y or W; more preferably P or T); X21is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N); X22is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably L); and wherein optionally one or two (for example optionally 1) of X20, X21, X22are absent;and preferably wherein X20is P or T; X21is N; and X22is L (for example, the separating portion has the sequence PNL or TNL).

25. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 24, wherein the N-terminal portion is absent or is a sequence of 1 to 15 (preferably 1 to 10 or 1 to 8, more preferably 1 to 5, for example 1, 2, 34 or 5) naturally occurring amino acids.

26. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 25, wherein the N-terminal portion has the sequence X1X2X3X4X5, wherein X1is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably V or G; and most preferably V) or is absent; X2is any naturally occurring amino acid (preferably D, E, N or Q; more preferably D) or is absent; X3is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N) or is absent; X4is any naturally occurring amino acid (preferably H, K or R; more preferably K) or is absent; and X5is any naturally occurring amino acid (preferably F, Y or W; more preferably F) or is absent; and preferably wherein X1 is V, G or absent (preferably V or absent), X2 is D or absent, X3is N or absent, X4is K or absent, and X5is F or absent.

27. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 26, wherein the N-terminal portion is absent, or the N- terminal portion has the sequence X1X2X3X4X5wherein X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; or X1is absent, X2is D, X3is N, X4is K, and X5is F; orX1is absent, X2is absent, X3is N, X4is K, and X5is F; or X1is absent, X2is absent, X3is absent, X4is K, and X5is F; or X1is absent, X2is absent, X3is absent, X4is absent, and X5is F.

28. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 27, wherein the C-terminal portion is absent or is a sequence of 1 to 50 (for example 1 to 35, 1 to 30, 15 to 25 or 18 to 22) naturally occurring amino acids.

29. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 28, wherein the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58[SEQ ID NO 135], wherein, X38is a sequence of 1 to 14 (preferably 1 to 9 or 1 to 7, more preferably 1 to 4, for example 1, 2, 3 or 4) naturally occurring amino acids (and preferably X38is any naturally occurring amino acid (most preferably X38is P)); X39is any naturally occurring amino acid (preferably S, T, M, P, F, Y or W; more preferably S); X56is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably A) or is absent; X57is any naturally occurring amino acid (preferably P) or is absent; and X58is any naturally occurring amino acid (preferably H, K or R; more preferably K) or is absent; (for example X38is P; X39is S; X56is A or absent; X57is P or absent; X58is K or absent) and optionally wherein, at least 1 and no more than 5 (for example 1, 2, 34 or 5) (preferably at least 1 and no more than 3 (for example 1, 2, or 3)) of the residues in the sequence QSANLLAEAKKLNDAQ [SEQ ID NO 136] are replaced by an alternative residue;and preferably optionally wherein, at least 1 and no more than 5 (for example 1, 2, 34 or 5) (preferably at least 1 and no more than 3 (for example 1, 2, or 3)) of the residues in the sequence QSANLLAEAKKLNDAQ [SEQ ID NO 136] are replaced by an alternative residue that is a conservative replacement.

30. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in claim 29, wherein the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58[SEQ ID NO 135], wherein X56is A, X57is P, and X58is K; X56is A; or X57is P, and X58is absent; X56is A, X57is absent; and X58is absent; or X56is absent, X57is absent, and X58is absent; and optionally wherein, at least 1 and no more than 3 (for example 1, 2, or 3) of the residues in the sequence QSANLLAEAKKLNDAQ [SEQ ID NO 136] are replaced by an alternative residue; and preferably optionally wherein, at least 1 and no more than 3 (for example 1, 2, or 3) of the residues in the sequence QSANLLAEAKKLNDAQ [SEQ ID NO 136] are replaced by an alternative residue that is a conservative replacement; and preferably wherein X38is P and X39is S.

31. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 30, wherein: (i) the separating portion has the sequence X20X21X22; and / or the N-terminal portion has the sequence X1X2X3X4X5 ;and / or the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58[SEQ ID NO 137]; wherein, in said separating portion,X20is P or T; X21is N; X22is L; wherein in said N-terminal portion, X1is V or G (preferably V), or absent; X2is D or absent; X3is N or absent; X4is K or absent; X5is F or absent; and wherein in said C-terminal portion, X56is A or absent; X57is P or absent; X58is K or absent; or (ii) the separating portion, N-terminal portion, and C-terminal portion are as defined in (i), wherein optionally (a) within each portion 1, 2 or 3 residues are replaced by an alternative residue; or (b) within those portions taken together at least 1 and no more than 10 (for example, not more than 5, for example 1, 2, 3, 4, or 5) residues are replaced by an alternative residue.

32. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 31, wherein said separating portion has the sequence PNL or TNL; and / or wherein said N-terminal portion has the sequence VDNKF [SEQ ID NO 138].

33. The CD16a-binding polypeptide as claimed in any one of claims 1 or 3 to 32, which consists of a CD16a-binding polypeptide as defined in any preceding claim, and comprising at least one (for example one, two or three) additional binding moiety(ies).

34. The CD16a-binding polypeptide as claimed in any one of claims 1 or 3 to 33 or the CD16a-binding oligomer as claimed in any one of claims 2 to 32, wherein the CD16a-binding motif sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.150 to 221 and SEQ ID No.259 to 272; preferably from SEQ ID NOs.166, 168, 178, 182, and 202, or from SEQ ID NOs.164, 166, 168, and 200 (for example 164, 166 and 168),from SEQ ID NOs.166, 168, 200, 184 and 259; from SEQ ID NOs.166, 168, 200 and 259; or from SEQ ID NOs.150, 184 and 200. and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably a residue that is a conservative replacement.

35. The CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043), and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue that is a conservative replacement; or the CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.1 to 73, and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue that is a conservative replacement; or the CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.1 and 11 to 67, and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue that is a conservative replacement; orthe CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.11 to 67, and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue that is a conservative replacement; the CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the, or each, CD16a- binding polypeptide sequence is selected from SEQ ID NOs.1, 17, 19, 35, 51 and 245 (Example ID 1001), and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue that is a conservative replacement; or the CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the, or each, CD16a- binding polypeptide sequence is selected from SEQ ID NOs.1, 35 and 51, and wherein optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue, and preferably optionally from 1 to 5 (preferably 1, 2 or 3) residues in the sequence are replaced by an alternative residue that is a conservative replacement.

36. The CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from: VDNKFNKEVQMAQFEIRKLPNLNHHQSFAFIKSLMDDPSQSANLLAEAKKLNDAQAP K [SEQ ID NO: 1] or VDNKFNKEQQIAQYEIRKLPNLNHHQTFAFIKSLLDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO:51] orVDNKFNKEQQIAQYEIRRLPNLNHHQTFAFIKSLLDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO:245].

37. The CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from: VDNKFNKEQFYARDEIDLLPNLNEDQKWAFYMSLIDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 74]; and; VDNKFNKEFWIAESEIESLPNLNIYQKWAFKYSLADDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 75].

38. The CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.12, 17, 19, 29, 33, 49, 51, and 53; for example SEQ ID NOs.17, 19, 29, 33, and 53; or wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.19, 33, 17, 29, 53, 16, 25, 15, 51, 36, 49, 55, 43, 24, 56, 12, 28, 21, 59, 52, 32, 18, 27, 35 or 11; or 34, 45 or 51; or 26, 35 or 47.

39. The CD16a-binding polypeptide as claimed in claim 1 or 3 or the CD16a- binding oligomer as claimed in claim 2 or 3, wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.15, 17, 19, and 51; for example 15, 19 or 17; or wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.1, 17, 19, 51 and 245; for example 1, 51 or 245; or wherein the sequence of the or each CD16a-binding polypeptide is selected from SEQ ID NOs.1, 17, 19, 35, 51 and 245; for example 1, 35, 51 or 245 (for example 1, 35 or 51).

40. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 39, wherein the or each CD16a-binding polypeptide does not comprise methionine.

41. The CD16a-binding polypeptide or the CD16a-binding oligomer with the sequence according to any preceding claim, wherein, at a position at which a methionine residue is recited, the polypeptide has the sequence with the methionine residue independently substituted for a different naturally occurring amino acid or an unnatural amino acid (for example a different naturally occurring amino acid or norleucine, homoleucine or tert- butylalanine); and preferably each methionine residue is independently substituted for an amino acid selected from isoleucine (I), leucine (L), glutamine (Q), valine (V), norleucine (nL), homoleucine (hL) or tert- butylalanine (t-BuA); and more preferably each methionine residue is independently substituted for a norleucine or isoleucine.

42. The CD16a-binding polypeptide or the CD16a-binding oligomer as claimed in any one of claims 3 to 41, wherein one or more residues (for example 1 to 5 residues, for example 1, 2 ,3, 4 or 5) of the or each CD16a-binding polypeptide is / are substituted for an unnatural amino acid, for example norleucine, homoleucine or tert-butylalanine; and / or wherein one or more methionine residues, when present (for example 1 or 2 methionine residue(s) when present), is / are substituted for an unnatural amino acid, for example norleucine, homoleucine or tert- butylalanine; and / or wherein one or more leucine residues, when present (for example 1 to 5 leucine residues, when present), is / are substituted for norleucine, homoleucine or tert-butylalanine; and / or wherein one or more methionine residues, when present (for example 1 or 2 methionine residue(s) when present), is / are oxidised (for example is / are Met(O)).

43. A CD16a-binding oligomer as claimed in any one of claims 2 to 43, which comprises 2, 3, 4, or 5 CD16a-binding polypeptides as defined in any one of claims 3 to 42.

44. The CD16a-binding oligomer as claimed any one of claims 2 to 43, which comprises at least two CD16a-binding polypeptides, wherein a first CD16a- binding polypeptide is as defined in any of claims 3 to 42, and a second CD16a-binding polypeptide is as defined in any of claims 3 to 42. 45 The CD16a-binding oligomer as claimed in claim 44, which comprises at least two CD16a-binding polypeptides, wherein the first and second CD16a-binding polypeptide have the same sequence.

46. The CD16a-binding oligomer as claimed in claim 44, which comprises at least two CD16a-binding polypeptides, wherein the first and second CD16a-binding polypeptide have a different sequence.

47. The CD16a-binding oligomer according to claim 44, which comprises at least two CD16a-binding polypeptides, wherein: a first CD16a-binding polypeptide comprises a first CD16a binding motif selected from SEQ ID Nos.150 to 221 and SEQ ID No.259 to 272 (Motif ID 1014 to 1026 and 1044), or comprises a sequence selected from SEQ ID NOs. 1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043); and a second CD16a-binding polypeptide comprises a second CD16a binding motif selected from SEQ ID NOs.150-221 and SEQ ID No.259 to 272, or comprises a sequence selected from SEQ ID NOs.1-75 and SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043).

48. The CD16a-binding oligomer according to claim 47, which comprises at least two CD16a-binding polypeptides, wherein the first and second CD16a-binding polypeptides have the same sequence, or the first and second CD16a binding motifs selected have the same sequence; or wherein the first and second binding motif selected or first and second CD16a-binding polypeptide have a different sequence.

49. The CD16a-binding polypeptide as claimed in any of claims 1 or 3 to 42, or the CD16a-binding oligomer as claimed in any one of claims 2 to 48, wherein the or each linker comprises one or more groups selected from the group consisting of50. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49, or the CD16a-binding oligomer as claimed in any one of claims 2 to 49, wherein at leastone linker (for example the, one or each linker) comprises one or more groups selected from the group consisting of ,p ,51. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 50, or the CD16a-binding oligomer as claimed in any one of claims 2 to 50, wherein at least one linker (for example the, one or each linker) additionally comprises a groupselected from the group consisting,52. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 51 or the CD16a-binding oligomer as claimed in any one of claims 2 to 51, wherein at least one linker (for example the, one or each linker) comprises one or more (for example one or two) groups selected from the group consisting of, ,53. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 52 or the CD16a-binding oligomer as claimed in any one of claims 2 to 52, wherein at least one linker (for example, each linker) comprises one or more (for example one or two) groups selected from the group consisting ofwherein n is 1 to 30 (for example 1 to 24 or 2 to 8);and more preferably wherein at least one linker (for example the, one or each linker) comprises one or more (for example one or two) groups selected from the groupgroup, wherein n is 1 to 30 (for example 1 to 24 or 2 to 8; and especially 2, 3, 4 or 8).

54. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 53 or the CD16a-binding oligomer as claimed in any one of claims 2 to 53, wherein at least one linker (for example the, one, or each linker) comprises one or two triazoles (for example one or twooptionally further comprises one or more (for example one, two, three or four)wherein n is 1 to 24(for example 1 to 16, 1 to 12, 1 to 8, or 2 to 8, and especially 2, 3 or 4) and / or one ormore (for example one).

55. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 52 or the CD16a-binding oligomer as claimed in any one of claims 2 to 52, comprising at least 1 (for example 1 or 2) additional functional portion, and wherein at least one (for example each) linker comprises (or is) a group selected from the group consisting of:

56. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 54 or the CD16a-binding oligomer as claimed in any one of claims 2 to 54 comprising at least 2 (for example 2) additional functional portions, whereinat least one (for example the or one) linker comprises (or is) a group selected from the group consisting of: ,.

57. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 56 or the CD16a-binding oligomer as claimed in any one of claims 2 to 56, wherein at least one linker (for example the, one or each linker) additionally comprises one or more amino acid, for example one or more amino acid selected from the group consisting of C, K, G and S (for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25 or 30 amino acid; and preferably 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acids; for example 1 to 8 amino acids, and more preferably 1, 7 or 8 amino acids)).

58. The CD16a-binding polypeptide or CD16a-binding polypeptide oligomer as claimed in claim 57, wherein at least one linker (for example the, one or each linker) additionally comprises a G, K, C, and / or further comprises the sequence GGGSG [SEQ ID NO 139], GGGGS [SEQ ID NO 140], GGSGG [SEQ ID NO 141], GSGGG [SEQ ID NO 142] and / or SGGGG [SEQ ID NO 143]; for example wherein at least one linker (for example, each linker) additionally comprises a G, K, C and / or further comprises thesequence GGS, SGG, GGSGGS, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG.

59. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 58, or the CD16a-binding oligomer as claimed in any one of claims 2 to 58, which further comprises 1, 2, 3, 4 or 5 additional functional portions, or at least two or at least three additional functional portions.

60. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 59, or the CD16a-binding oligomer as claimed in any one of claims 2 to 59, wherein the additional functional portion comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof.

61. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 59, or the CD16a-binding oligomer as claimed in any one of claims 2 to 59, wherein the additional functional portion comprises an additional binding moiety.

62. The CD16a-binding polypeptide or CD16a-binding oligomer as claimed in claim 61, wherein the additional binding moiety is specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for a NK cell target.

63. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 59, or the CD16a-binding oligomer as claimed in any one of claims 2 to 59, wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least two (for example 2, 3, 4 or 5) additional functional portions, wherein each additional functional portion may be the same or may be different.

64. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 59, or the CD16a-binding oligomer as claimed in any one of claims 2 to 59, wherein the CD16a-binding polypeptide or CD16a-binding oligomer comprises at least two (for example 2, 3, 4 or 5) additional functional portions,wherein a first additional functional portion comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for a NK cell target); and wherein the second additional functional portion comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof; or wherein a first additional functional portion comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for a NK cell target); and wherein the second additional functional portion comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for a NK cell target).

65. The CD16a-binding polypeptide or CD16a-binding oligomer as claimed in claim 64 comprising an additional functional portion, wherein the CD16a- binding polypeptide or CD16a-binding oligomer comprises at least 3 (for example 3, 4 or 5) additional functional portions, wherein a third additional functional portion comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for a NK cell target), or comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof; and preferably wherein a third additional functional portion comprises an additional binding moiety (for example an additional binding moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example BCMA, or is specific for a NK cell target).

66. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 65, wherein the CD16a-binding polypeptide comprises (or has) the following structure:[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]-[additional functional portion]; [additional functional portion]-[additional functional portion]-[linker]-[N- terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or [additional functional portion]-[linker]-[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[additional functional portion]; wherein, the linker, or each linker, is a linker as defined in any one of claims 49 to 58 (for example claim 55); wherein when more than one additional functional portion is present, each additional functional portion may be the same, or may be different; and wherein the linker, or each linker, is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the CD16a binding polypeptide.

67. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 65, wherein the CD16a-binding polypeptide comprises (or has) the following structure:wherein A represents: -[N-terminal portion]-[Helix 1]-[Separating portion]- [Helix 2]-[C-terminal portion] or -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]; X represents an additional functional portion; and Y represents an additional functional portion; wherein, the linker is a linker as defined in any one of claims 49 to 58 (for example claim 56); and wherein the linker is attached to any amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the CD16a binding polypeptide (for example, wherein the CD16a-binding polypeptide comprises the following structure68. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 65, wherein the CD16a-binding polypeptide comprises (or has) the following structure:or;and wherein X represents an additional functional portion; and Y represents an additional functional portion; wherein each linker may be the same or different, and each additional functional portion may be the same or different; wherein each linker is a linker as defined in any one of claims 49 to 58 (for example claim 55); and wherein each linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the CD16a binding polypeptide.

69. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 68, or the CD16a-binding oligomer as claimed in any one of claims 2 to 65, wherein an additional functional portion (for example, the, one, at least one, or each additional functional portion) comprises an additional binding moiety specific for BCMA which is a hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, wherein said hBCMA-binding polypeptide comprises the following structure: [hBCMA N-terminal portion]-[hBCMA Helix 1]-[hBCMA Separating portion]-[ hBCMA Helix 2]-[hBCMA C-terminal portion] the hBCMA binding motif being the portion [hBCMA Helix 1]-[ hBCMA Separating portion]-[hBCMA Helix 2]; and preferably wherein the hBCMA- binding polypeptide is a polypeptide comprising (or having) a sequence selected from the group consisting of SEQ ID No.273 to 281 (Example IDs 1027 to 1035) of Figure 20 and a sequence of Table A, or a derivative thereof (for example wherein from 1 to 5 (for example 1, 2 or 3 amino acid residues) are replaced by an alternative residue, for example a different naturally occurring amino acid or a different unnatural amino acid; or a different naturally occurring amino acid excluding methionine or a different unnatural amino acid); orthe hBCMA-binding polypeptide is a polypeptide comprising a sequence selected from the group consisting of SEQ ID NOs 282 to 288 (Example IDs 1036 to 1042) of Figure 21 and a sequence of Table B, or a derivative thereof (for example wherein from 1 to 5 (for example 1, 2 or 3 amino acid residues) are replaced by an alternative residue, for example a different naturally occurring amino acid or a different unnatural amino acid; or a different naturally occurring amino acid excluding methionine or a different unnatural amino acid).

70. A CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]; wherein the CD16a-binding motif sequence is selected from SEQ ID No.259 to 272 of Figure 14.

71. A CD16a-binding polypeptide which comprises at least one motif that binds to CD16a, and wherein said CD16a-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion] the CD16a-binding motif being the portion [Helix 1]-[Separating portion]- [Helix 2]; wherein the sequence of the CD16a-binding polypeptide is selected from SEQ ID NOs 245 to 258 (Example IDs 1001 to 1013 and 1043) of Figure 12.

73. A CD16a binder-drug conjugate comprising the CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 72, or the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69, and an additional therapeutic agent.

74. The CD16a binder-drug conjugate as claimed in claim 73, wherein the additional therapeutic agent is a cytotoxic drug, for example MMAF, MMAE, doxorubicin, pyrrolobenzodiazepine, amanitin, maytansinoids, duostatins, mitomycin C, desmethyltopotecan or SN-38.

75. The CD16a binder-drug conjugate as claimed in claim 73 or claim 74, wherein the CD16a-binding polypeptide is connected to the additional therapeutic agent via a linker.

76. A pharmaceutical composition comprising the CD16a-binding polypeptide as defined in any of claims 1, 3 to 42 or 49 to 72, or the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69.

77. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 72, the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69, the CD16a binder-drug conjugate as claimed in any of claims 73 to 75, and / or the pharmaceutical composition as claimed in claim 76, for use in medicine.

78. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 72, the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69, the CD16a binder-drug conjugate as claimed in any of claims 73 to 75, and / or the pharmaceutical composition as claimed in claim 75, for use in the treatment of cancer.

79. The CD16a-binding polypeptide as claimed in any of claims 1, 3 to 43 or 51 to 72, the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69, the CD16a binder-drug conjugate as claimed in any of claims 73 to 75, and / or the pharmaceutical composition as claimed in claim 76, for use as claimed in claim 78, wherein the cancer is multiple myeloma.

80. Use of the CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 72, the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69, the CD16a binder-drug conjugate as claimed in any of claims 73 to 75, and / or the pharmaceutical composition as claimed in claim 76, for the manufacture of a medicament for the treatment of cancer.

81. A method of treating cancer, the method comprising administering to a patient in need thereof the CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 72 the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69, the CD16a binder-drug conjugate as claimed in any of claims 73 to 75, and / or the pharmaceutical composition as claimed in claim 76.

82. A kit comprising the CD16a-binding polypeptide as claimed in any of claims 1, 3 to 42 or 49 to 72, the CD16a-binding oligomer as claimed in any of claims 2 to 65 or 69the CD16a binder-drug conjugate as claimed in any of claims 73 to 75, or the pharmaceutical composition as claimed in claim 76 and, optionally, one or more further therapeutic agent(s).

83. The kit as claimed in claim 82, wherein the one or more further therapeutic agent(s) is selected from a proteasome inhibitor (for example carlfizomib or bortezomib), an immunomodulatory agent (for example lenalidomide or thalidomide), an alkylator (for example melphalan or melflufen), a steroid (for example dexamethasone or prednisone), an anti-CD38 agent (for example daratumumab), an immune checkpoint inhibitor (for example a CTLA-4 inhibitor, a PD-1 inhibitor, or a PD-L1 inhibitor), and an ADAM17 inhibitor.

84. The kit as claimed in claim 82 or claim 83, for use in the treatment of cancer, for example multiple myeloma.