Cd16a-binding polypeptide

Abstract

The invention provides a hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, wherein said 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] and which further comprises at least one additional functional portion, wherein the hBCMA-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 human BCMA (hBCMA)-binding polypeptides comprising a hBCMA-binding polypeptide and at least one additional functional 5 portion, or comprising at least two hBCMA-binding polypeptides and optionally at least one additional functional portion, having a linker as described here. The present invention also relates to hBCMA-binding polypeptides. The present invention also relates to pharmaceutical compositions comprising said hBCMA-binding polypeptides, and their use in the treatment and / or prophylaxis of cancer. 10 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, CAR-T treatments and antibody drug conjugates. Despite activity of these treatments, however, some patients exhibit very short responses or 15 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- 20 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 25 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. 1 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). Multiple myeloma is a hematological malignancy that despite recent advances in immunotherapy is still incurable. Several surface proteins enriched on myeloma cells have been identified and served as targets for therapeutic interventions. One such target is BCMA (TNFRSF17), which is highly expressed on myeloma cells but to a lesser extent also expressed on non-malignant cells of the B cell compartment as well as plasmcytoid dendritic cells. Two B-cell stimulating ligands, a proliferation- inducing ligand (APRIL) and B-cell activating factor (BAFF), bind to BCMA and are implicated in autoimmune disorders as well as cancer (Bossen and Schneider (2006) BAFF, APRIL and their receptors: Structure, function and signalling, Seminars in Immunology, doi:10.1016 / j.smim.2006.04.006; Moreaux et al. (2004) BAFF and APRIL protect myeloma cells from apoptosis induced by interleukin 6 deprivation and dexamethasone, Blood 103 (8): 3148–3157; Samy et al. (2017) Targeting BAFF and APRIL in systemic lupus erythematosus and other antibody-associated diseases, International Reviews of Immunology, 36:1, 3-19). CAR-T cell therapies and antibody-based therapies targeting BCMA have proven efficacious in clinical practice prolonging patient overall survival. Still, not all patients show satisfactory response to treatment and patients eventually relapse in their disease (see, for example, Teoh, P.J., Chng, W.J. CAR T-cell therapy in multiple myeloma: more room for improvement. Blood Cancer J.11, 84 (2021). https: / / doi.org / 10.1038 / s41408-021-00469-5). 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 such as immunogenicity. The present invention seeks to address the afore-mentioned needs. Summary of the Invention The present invention provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; and which further comprises at least one additional functional portion, wherein the hBCMA-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 present invention also provides an hBCMA-binding oligomer, which comprises at least two hBCMA-binding polypeptides, wherein each hBCMA-binding polypeptide comprises at least one motif that binds to hBCMA, and wherein each 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]; and wherein the hBCMA-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 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 and wherein the hBCMA-binding oligomer optionally further comprises at least one additional functional portion, wherein the hBCMA-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 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 further provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; wherein the hBCMA-binding motif sequence is selected from SEQ ID No.1036 to 1042 of Figure 16. The present invention further provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; wherein the sequence of the hBCMA-binding polypeptide is selected from SEQ ID NOs 1027 to 1035 of Figure 15. The invention therefore provides novel hBCMA-binding polypeptides and hBCMA- binding oligomers that are effective in binding cancer cells (also termed ‘engagers’). They find particular use as cancer cell-binding units in conjugates and fusion proteins that can trigger cytotoxic drug-mediated or ADCC-mediated cancer cell killing and they therefore show promise in anti-cancer immunotherapeutics. The invention further provides an hBCMA-binding oligomer, which comprises at least two hBCMA-binding polypeptides of the invention. The present inventors have surprisingly found that such hBCMA-binding polypeptides and hBCMA-binding oligomers based on a non-antibody scaffold are effective in binding cancer cells and triggering cytotoxic drug-mediated or antibody- dependent cellular cytotoxicity-mediated (ADCC-mediated) cancer cell killing. Furthermore, the hBCMA-binding oligomers and hBCMA-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 po 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 hBCMA-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 hBCMA-binding polypeptide with the N-terminal of another hBCMA-binding polypeptide and / or other functional portion, and the possibility to connect the C-terminal of a hBCMA- binding polypeptide with the C-terminal of another hBCMA-binding polypeptide and / or other functional portion. Using synthetic linkers as described herein also allows the possibility of connecting hBCMA-binding polypeptides and / or other functional portion at a position within the N-terminal portion or C-terminal portion of a hBCMA-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 further provides an hBCMA binder-drug conjugate comprising the hBCMA-binding polypeptide or hBCMA binding oligomer of the invention and an additional therapeutic agent. The invention further provides a method of making the hBCMA-binding polypeptide or hBCMA binding oligomer of the invention. The invention also provides a pharmaceutical composition comprising an hBCMA- binding polypeptide, hBCMA binding oligomer, or hBCMA binder-drug conjugate, as disclosed herein. The invention further provides an hBCMA-binding polypeptide, hBCMA binding oligomer, hBCMA binder-drug conjugate, or pharmaceutical composition as disclosed herein for use in medicine, in particular in the treatment of cancer. The invention also provides the use of an hBCMA-binding polypeptide, hBCMA binding oligomer, hBCMA binder-drug conjugate, or pharmaceutical composition as disclosed herein 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 an active component that comprises an hBCMA-binding polypeptide or hBCMA binding oligomer as disclosed herein. For example, the hBCMA-binding polypeptide or hBCMA binding oligomer may be present as a cancer cell-binding unit in a conjugate or a fusion protein, such as one that can trigger cytotoxic drug-mediated or ADCC-mediated cancer cell killing. The invention also provides a method of treating cancer in which the method comprises administering to a patient in need thereof a pharmaceutical composition as disclosed herein. The invention further provides a kit comprising an hBCMA-binding polypeptide, hBCMA-binding oligomer, hBCMA binder-drug conjugate or pharmaceutical composition as disclosed herein 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 schematic domain organization of the hBCMA-binding polypeptides described in the present disclosure. Figure 2 shows the experimental set up (Figure 2a) and the resulting sensorgram obtained after injection of the purified hBCMA binding variant His6-Fa-G6-ABDWT[SEQ ID No 3],at 200 nM concentration, over a sensor chip surface on which hBCMA- Fc has been immobilized (Figure 2b). Figure 3 shows sensorgrams obtained after injection of purified Fa-G6-His6[SEQ ID No 4] and Fa-G6 truncations (-2, -3, -4 and -5 aa) [SEQ ID Nos 5-8], at 20 nM concentrations, over a sensor chip surface immobilized with hBCMA-Fc. Figure 4 shows sensorgrams obtained after injection of a set of purified His6-Fa-G6 [SEQ ID N 129] (“F G6 ild ”) d 14 F G6 l i b i i [SEQ ID Nos 9-22], each equipped with a N-terminal His6tag, at 200 nM concentrations, over a sensor chip surface immobilized with hBCMA-Fc. Figure 5 shows sensorgrams obtained after injection of 18 purified second - generation Fa-G6 variants [SEQ IDs 2 and 23-39] equipped with a C-terminal His6, at 100 nM, over a sensor chip surface immobilized with hBCMA-Fc. Figure 6 shows (a) thermal melting curves for Fa-G6-His6and 18 second generation variants and (b) thermal melting curves as well as determined thermal melting temperatures (Tms) for Fa-G6-His6[SEQ ID No 4] and the second generation clone 1- E6 [SEQ ID No 2], also equipped with a C-terminal His6. Figure 7 shows the receptor binding properties of 1-E6-MBP-MMAF and the non- conjugated capped 1-E6 polypeptides as observed in a BCMA-binding ELISA assay. Figure 8 shows the impact of 1-E6-MBP-MMAF on EJM cell viability in the presence of 5µM 1-E6 or its corresponding non hBCMA binding counterpart (null). Figure 9 shows the concentration-effect curves of Fa-G6- mc-MMAF on cell viability of BCMA positive myeloma cell lines. Figure 10 shows (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – CD16a-SEQ ID NO.1 of Figure 22 (SEQ ID NO 308)) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID No 2): and (b) a schematic representation of dimeric constructs of the invention comprising one CD16a binding polypeptide (e.g. A10 – CD16a-SEQ ID NO.1 of Figure 22) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID No 2 as shown in Table 1). Figures 11, 12 and 13 show (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – CD16a-SEQ ID NO.1 of Figure 22 and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID 2 as shown in Table 1); (b) a schematic representation of trimeric constructs of the invention comprising one CD16a binding polypeptide (e.g. A10 – CD16a-SEQ ID NO.1 of Figure 22) and two additional functional portions (two BCMA binding moieties, e.g.1-E6, – SEQ ID No 2 as shown in Table 1). Figure 14 shows (a) a schematic representation of one CD16a binding polypeptide functional portion (e.g. A10 – CD16a-SEQ ID NO.1 of Figure 22) and one additional functional portion (a BCMA binding moiety, e.g.1-E6, – SEQ ID NO 2 as shown in Table 1): and (b) a schematic representation of multimeric constructs of the invention comprising one or two CD16a binding polypeptide (e.g. A10 – CD16a-SEQ ID NO.1 of Figure 22) and two or four additional functional portions (BCMA binding moieties, e.g.1-E6, – SEQ ID No 2). Figure 15 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 16 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 17 shows the shows the sequence and structure of the hCD16a × hBCMA dual engager multimeric constructs synthesised in Example 12 (* indicates that a K residue side chain is modified as shown in the structure to have a linker attached to its side chain). Figure 18 shows the structures (i.e. the ([N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[ C-terminal portion] sequences) of hBCMA binding polypeptides of the present invention. Figure 19 shows the sequences of hBCMA binding motifs (i.e. the [Helix 1]- [Separating portion]-[Helix 2] sequence) of example hBCMA binding polypeptides of the present invention. Figure 20 shows the structures (i.e. the ([CD16a N-terminal portion]-[CD16a Helix 1]- [CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion] sequences) of example CD16a binding polypeptide functional portions of the invention. Figure 21 shows the sequences of binding motifs (i.e. the [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2] sequence) of example CD16a binding polypeptide functional portions of the present invention. Figure 22 shows the structures (i.e. the ([CD16a N-terminal portion]-[CD16a Helix 1]- [CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion] sequences) of example CD16a binding polypeptide functional portions of the invention. Figure 23 shows the sequences of binding motifs (i.e. the [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2] sequence) of example CD16a binding polypeptide functional portions of the present invention. Figure 24 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 12; * 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 hBCMA-binding polypeptides as disclosed herein are surprisingly effective in binding cancer cells. They therefore find particular use in the treatment and / or prophylaxis of cancer, for example as cancer cell-binding units in conjugates and fusion proteins. As discussed in more detail below, the present inventors have surprisingly found that hBCMA-binding polypeptides based on three-helix affibody scaffolds are effective at binding BCMA on myeloma cells, and trigger strong ADCC-mediated or cytotoxic drug-mediated responses against cancer cells. Such ADCC-mediated anti-cancer responses are beneficial in the treatment of multiple myeloma. Notably, the inventors have found that such anti-cancer responses compare favourably 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 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 present invention provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; and which further comprises at least one additional functional portion, wherein the hBCMA-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

[0003] The present invention also provides an hBCMA-binding oligomer, which comprises at least two hBCMA-binding polypeptides, wherein each hBCMA-binding polypeptide comprises at least one motif that binds to hBCMA, and wherein each 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]; and wherein the hBCMA-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 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 and wherein the hBCMA-binding oligomer optionally further comprises at least one additional functional portion, wherein the hBCMA-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 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 further provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; wherein the hBCMA-binding motif sequence is selected from SEQ ID The present invention further provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; wherein the sequence of the hBCMA-binding polypeptide is selected from SEQ ID NOs 1027 to 1035 of Figure 15. 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 Biotechnol., 1997:15:772, doi: 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 1. 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 may 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 hBCMA-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 hBCMA-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 hBCMA-binding polypeptide and hBCMA- bin 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 The present disclosure also includes derivatives of the sequences described herein wherein from 1 to 5 (for example 1, 2 or 3) amino acid residues may be replaced by an alternative residue that is 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. In certain embodiments, the sequences described herein (for example, hBCMA- binding polypeptide and hBCMA-binding oligomer sequences described here) do not comprise methionine. In certain embodiments, in the sequences described herein (for example, the hBCMA-binding polypeptide and hBCMA-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 a different residue, for example a different naturally occurring amino acid or unnatural amino acid. In certain embodiments, in the sequences described her the sequence with the methionine residue independently substituted for an amino acid selected from isoleucine (I), leucine (L), glutamine (Q), norleucine (nL), homoleucine (hL) and tert-butylalanine (tBuA) (for example selected from isoleucine, leucine, glutamine, and norleucine; or norleucine); for example isoleucine and norleucine. In another embodiment, when one or more methionine is present in a hBCMA- binding polypeptides or CD16a-binding oligomers as defined herein, one, some or all of the methionine residues may be replaced by an alternative amino acid, for example a different naturally occurring amino acid or unnatural amino acid, such as an amino acid selected from isoleucine (I), leucine (L), glutamine (Q), or norleucine; and especially isoleucine (I) and norleucine. 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; 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; and especially isoleucine and norleucine. For example, in embodiments wherein X9may be or is methionine, the residue at X9may 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 X10may be or is methionine, the residue at X10may 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 X14may be or is methionine, the residue at X14may 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 X18may be or is methionine, the residue at X18may 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 X31may be or is methionine, the residue at X31may 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. In particular, in embodiments wherein X31and X35may be or are methionine, the residues at X31and 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. Alternatively, or additionally, in certain embodiments, the sequences described herein (for example, hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 exa 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 hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 X9may be or is methionine, the residue at X9may be replaced by an unnatural amino acid(s) (for example norleucine). For exa may be replaced by an unnatural amino acid(s) (for example norleucine). For example, in embodiments wherein X14may be or is methionine, the residue at X14may be replaced by an unnatural amino acid(s) (for example norleucine). For example, in embodiments wherein X18may be or is methionine, the residue at X18may be replaced by an unnatural amino acid(s) (for example norleucine). For example, in embodiments wherein X31may be or is methionine, the residue at X31may 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). In particular, in embodiments wherein X31and X35may be or are methionine, the residues at X31and X35may 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 hBCMA-binding polypeptide and hBCMA-binding oligomer sequences described here) may be oxidised, i.e. 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 X9may be or is methionine, when present the methionine at X9 may be oxidised (for example Met(O)). For example, in embodiments wherein X10may be or is methionine, when present the methionine at X10may be oxidised (for example Met(O)). For example, in embodiments wherein X14may be or is methionine, when present the methionine at X14may be oxidised (for example Met(O)). For example, in embodiments wherein X18may be or is methionine, when present the methionine at X18may be oxidised (for example. Met(O)). For example, in embodiments wherein X31may be or is methionine, when present the methionine at X31may be oxidised (for example Met(O)). For example, in embodiments wherein X35may be or is methionine, when present the methionine at X35may be oxidised (for example Met(O)). In particular, in embodiments wherein X31and X35may be or are methionine, when present the me Alternatively, or additionally, in certain embodiments, the sequences described herein (for example, the hBCMA-binding polypeptide and hBCMA-binding oligomer sequences described here) comprise a peptide purification tag or moiety (for example a histidine-tag (for example a polyhistidine tag) 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 BCMA-binding polypeptide and BCMA-binding oligomer sequences described herein. In an embodiment, the BCMA-binding polypeptides and BCMA- 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 BCMA-binding polypeptide and BCMA-binding oligomer sequences described herein. Therefore, the sequences described herein (for example, the hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 his 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 hBCMA- binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA- binding oligomer sequences described herein. The sequences described herein (for example, the hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide and hBCMA-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 hBCMA-binding polypeptide is one wherein the hBCMAbinding 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: 2. When a hBCMA-binding polypeptide is described herein as having hBCMA binding efficacy that is at least X% of a specific peptide (e.g. SEQ ID NO: 2), it is understood that the IC50concentration of the polypeptide for binding to the hBCMA receptor is no more than 100 / X times the IC50concentration for the specific peptide (SEQ ID NO: 2) to the hBCMA receptor, when measured under the same conditions. For example, if the binding efficacy of a hBCMA-binding polypeptide is at least 5%, and more preferably at least 10%, 20%, 25% or 50% of the hBCMA-binding efficacy of the specific peptide (e.g. SEQ ID NO: 2), that is to say that the IC50concentration of the alternative polypeptide for binding to the hBCMA 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: 2) to the hBCMA receptor, when measured under the same conditions. In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes for binding at hBCMA with the peptide of SEQ ID NO: 2. The present invention provides an hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, wherein said 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]. Preferably, the hBCMA-binding polypeptide is one wherein: i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, 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; X25is F or Y; X31is I, M, or V; X33is K or S; X35is 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. In an embodiment, Helix 1 comprises the sequence KEX9X10X11ADX14EIX17X18and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35D, for example Helix 1 comprises the sequence NKEX9X10X11ADX14EIX17X18L and Helix 2 comprises the sequence NFX25QKWAFX31RX33LX35DD, wherein X9, X10, X11, X14, X17, X18, X25, X31, X33, and X35are as defined above. Preferably, such an hBCMA-binding polypeptide is one wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO: 2. Preferably, the binding efficacy is at least 5%, for example at least 10%, 20%, 25% or 50% of the hBCMA binding efficacy of the specific peptide (e.g. SEQ ID NO: 2). In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2 for binding of hBCMA. In an embodiment, the hBCMA-binding polypeptide is one wherein i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, 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; X25is F or Y; X31is I, M, or V; X33is K or S; X35is 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; and wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO: 2. Preferably, the binding efficacy is at least 5%, for example at least 10%, 20%, 25% or 50% of the hBCMA binding efficacy of the specific peptide (e.g. SEQ ID NO: 2). In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2 of hBCMA. 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, at least 1 and no more than 8 of the residues may be replaced with an alternative residue. The replaced residues may be all in Helix 1 or in Helix 2, or there may be 1 replaced residue in one of them and 1, 2, 3, 4, 5, 6 or 7 replaced residues in the other, or there may be 2 replaced residues in one of them and 1, 2, 3, 4, 5, or 6 replaced residues in the other, or there may be 3 replaced residues in one of them and 1, 2, 3, 4, or 5 replaced residues in the other, or there may be 4 replaced residues in one of them and 1, 2, 3 or 4 replaced residue in the other, or there may be 5 replaced residues in one of them and 1, 2 or 3 replaced residues in the other, or there may be 6 replaced residues in one of them and 1 or 2 replaced residues in the other, or there may be 7 replaced residues in one of them and 1 replaced residue in the other. For example, there may be 1, 2, 3, 4 or 5 replaced residues in the residues denoted with an Xnlabel, for example 1, 2 or 3, for example 1. As there are 10 residues with an Xn label, a peptide with 5 residues replaced has 50% sequence identity with the recited sequence. For replacement of 2 residues, it is 80% and for replacement of 1 residue it is 90% sequence identity. In another embodiment, 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. The replaced residues may be all in Helix 1 or in Helix 2, or there may be 1 replaced residue in one of them and 1, 2, 3, 4 or 5 replaced residues in the other, or there may be 2 replaced residues in one of them and 1, 2, or 3 replaced residues in the other, or there may be 3 replaced residues in one of them and 1 or 2 replaced residues in the other, or there may be 4 replaced residues in one of them and 1 replaced residue in the other. For example, there may be 1, 2, 3, 4 or 5 replaced residues in the residues not denoted with an Xnlabel, for example 1, 2 or 3, for example 1. As there are 12 residues without an Xnlabel, a peptide with 5 residues replaced has 58% sequence identity with the recited sequence. For replacement of 2 residues, it is 83% and for replacement of 1 residue it is 92% sequence identity. In another embodiment, of the residues not labelled as an Xnresidue, at least 1 and no more than 3 of the residues may be replaced with an alternative residue. The replaced residues may be all in Helix 1 or in Helix 2, or there may be 1 replaced residue in one of them and 1 or 2 replaced residues in the other, or there may be 2 replaced residues in one of them and 1 replaced residues in the other. For example, there may be 1, 2, or 3 replaced residues in the residues not denoted with an Xnlabel, for example 1 or 2, for example 1. As there are 12 residues without an Xnlabel, a peptide with 3 residues replaced has 75% sequence identity with the recited sequence. For replacement of 2 residues, it is 83% and for replacement of 1 residue it is 92% 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 13, at least 1 and no more than 12, at least 1 and no more than 11, at least 1 and no more than 10, for example at least 1 and no more than 9, 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, for example at least 1 and no more than 5, for example 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, 5, 6, 7, 8, 9, or 10 replacement residues in total in those portions. 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. Alternatively, an amino acid residue replacement for a residue denoted as Xnor a residue not denoted as Xnmay be a non-canonical (also known as unnatural) amino acid, i.e. an amino acid that is not found in natural polypeptide chains. As mentioned above, 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, or nitroarginine). These can be produced as secondary metabolites or synthesised chemically. Preferably, an unnatural amino acid according to the present invention is one that is isosteric with a naturally occurring amino acid, for example norleucine. Therefore, an amino acid residue replacement for a residue denoted as Xnor a residue not denoted as Xnmay be an unnatural amino acid according to the present invention is one that is isosteric with a naturally occurring amino acid, and preferably norleucine. In another embodiment, the hBCMA-binding polypeptide is one wherein: i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FYQKWAFIRX33LM, wherein, independently from each other, X9is D, E, H, K, N, Q, S, or V; X10is A, E, F, I, K, M, N, Q, R, S, T, Y, or V; X11is E, F, or H; X14is A, E, H, I, K, L, Q, R, T, or Y; X17is A, E S, T, or V; X18is A, F, H, K, L, M, N, T, or S; X33is K or S; 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 3 (for example 1, 2 or 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 3 (for example 1, 2 or 3) of the residues not labelled as Xnare replaced by an alternative residue. Preferably, such an hBCMA-binding polypeptide is one wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO.2. For example, the binding efficacy is at least 5%, for example at least 10%, 20%, 25% or 50% of the hBCMA binding efficacy of the specific peptide (e.g. SEQ ID NO: 2). In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2 for binding of hBCMA. 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, at least 1 and no more than 3 (for example 1, 2 or 3) of the residues may be replaced with an alternative residue. The replaced residues may be all in Helix 1 or in Helix 2, or there may be 1 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 denoted with an Xnlabel, for example 1 or 2, for example 1. As there are 7 residues with an Xnlabel, a peptide with 3 residues replaced has 57% sequence identity with the recited sequence. For replacement of 2 residues, it is 71% and for replacement of 1 residue it is 86% sequence identity. Of the residues not labelled as an Xnresidue, at least 1 and no more than 3 (for example 1, 2 or 3) of the residues may be replaced with an alternative residue. The replaced residues may be all in Helix 1 or in Helix 2, or there may be 1 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, for example 1 or 2, for example 1. As there are 15 residues without an Xnlabel, a peptide with 3 residues replaced has 80% sequence identity with the recited sequence. For replacement of 2 residues, it is 87% and for replacement of 1 residue it is 93% 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 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 at least 1 and no more than 3. Particularly, there may be 1, 2, 3, 4, 5, or 6 replacement residues in total in those portions. An amino acid residue replacement for a residue denoted as Xn or a residue not denoted as Xnmay be a conservative or a non-conservative replacement, or a non- canonical (also known as unnatural) amino acid, as described herein above. In a further embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9and X10are an unnatural amino acid (for example norleucine) or any naturally occurring amino acid excluding methionine; X11is E, F, H, Q, T or Y; X14is an unnatural amino acid (for example norleucine) or any naturally occurring amino acid excluding methionine; X17is A, E, Q, S, T or V; X18is an unnatural amino acid (for example norleucine) or any naturally occurring amino acid excluding methionine; X25is F or Y; X31is I,V, L, glutamine, or an unnatural amino acid (for example norleucine) (preferably I, L, V, glutamine, or norleucine); X33is K or S; X35is I, L, V, glutamine, or an unnatural amino acid (for example norleucine) (preferably I, L, V, glutamine, or norleucine); or In a further embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other,X9and X10are norleucine or any naturally occurring amino acid excluding methionine; X11 is E, F, H, Q, T or Y; X14is norleucine or any naturally occurring amino acid excluding methionine; X17is A, E, Q, S, T or V; X18is norleucine, or any naturally occurring amino acid excluding methionine; X25is F or Y; X31is I, V, L, glutamineor norleucine (for example I, V or norleucine; preferably I or norleucine); X33is K or S; X35is I, L, V glutamine or norleucine (for example I, V or norleucine; preferably I or norleucine); or In a further embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9and X10are any naturally occurring amino acid excluding methionine; X11is E, F, H, Q, T or Y; X14is any naturally occurring amino acid excluding methionine; X17is A, E, Q, S, T or V; X18is any naturally occurring amino acid excluding methionine; X25is F or Y; X31is I or V; X33is K or S; X35is I, L or V. In a further embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FYQKWAFIRX33LX35, wherein, independently from each other, X9is D, E, H, K, N, Q, S, or V; X10is A, E, F, I, K, N, Q, R, S, T, Y, V, L or an unnatural amino acid (for example norleucine); X11is E, F, or H; X14is A, E, H, I, K, L, Q, R, T, or Y; X17is A, E S, T, or V; X18is A, F, H, K, L, N, T, S, I, Q or an unnatural amino acid (for example norleucine); X33is K or S; X35is a naturally occurring amino acid excluding methionine (preferably a naturally occurring amino acid that is isosteric with methionine, for example isoleucine) or an unnatural amino acid (preferably a naturally occurring amino acid that is isosteric with methionine, for example norleucine); or; In a further embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FYQKWAFIRX33LX35, wherein, independently from each other, X9is D, E, H, K, N, Q, S, or V; X10is A, E, F, I, K, N, Q, R, S, T, Y, V, L or norleucine; X11is E, F, or H; X14is A, E, H, I, K, L, Q, R, T, or Y; X17is A, E S, T, or V; X18is A, F, H, K, L, N, T, S, I, Q or norleucine; X33is K or S; X35is a naturally occurring amino acid that is isosteric with methionine (for example isoleucine), or norleucine; or; In a further embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FYQKWAFIRX33L X35, wherein, independently from each other, X9is D, E, H, K, N, Q, S, or V; X10is A, E, F, I, K, N, Q, R, S, T, Y, or V; X11is E, F, or H; X14is A, E, H, I, K, L, Q, R, T, or Y; X17is A, E S, T, or V; X18is A, F, H, K, L, N, T, or S; X33is K or S; X35is isoleucine or norleucine; In one preferred embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, or X31, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9and X10are any naturally occurring amino acid excluding methionine (preferably X9is N X10is Q); X11is E, F, H, Q, T or Y (preferably F); X14is any naturally occurring amino acid excluding methionine (preferably E); X17is A, E, Q, S, T or V (preferably A); X18is any naturally occurring amino acid excluding methionine (preferably A); X25is F or Y (preferably Y); X31is I or V (preferably I); X33is K or S (preferably K); X35is a naturally occurring amino acid (for example a naturally occurring amino acid excluding methionine, and more preferably, a naturally occurring amino acid that is isosteric with methionine, for example isoleucine) or an unnatural amino acid (for example a naturally occurring amino acid that is isosteric with methionine, for example norleucine, or homoleucine or tert- Butyl alanine). In one preferred embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18or X31, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35 [SEQ ID NO.279], wherein, independently from each other, X9and X10are any naturally occurring amino acid excluding methionine (preferably X9is N X10is Q); X11is E, F, H, Q, T or Y (preferably F); X14is any naturally occurring amino acid excluding methionine (preferably E); X17is A, E, Q, S, T or V (preferably A); X18is any naturally occurring amino acid excluding methionine (preferably A); X25is F or Y (preferably Y); X31is I or V (preferably I); X33is K or S (preferably K); X35is I, L, M, V, Q, norleucine, homoleucine, or tert-Butyl alanine (for example I, L, V, Q, norleucine, homoleucine, tert-Butyl alanine). In one preferred embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18or X31, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9is N; X10is Q; X11is F; X14is E; X17is A; X18A; X25is Y; X31is I; X33is K; and X35is a naturally occurring amino acid (for example a naturally occurring amino acid excluding methionine, and more preferably, a naturally occurring amino acid that is isosteric with methionine, for example isoleucine) or an unnatural amino acid (for example a naturally occurring amino acid that is isosteric with methionine, for example norleucine, or homoleucine or tert- Butyl alanine). In one preferred embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18or X31, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9is N; X10is Q; X11is F; X14is E; X17is A; X18A; X25is Y; X31is I; X33is K; and X35is I, L, M, V, Q, norleucine, homoleucine, or tert-Butyl alanine (for example I, L, V, Q, norleucine, homoleucine, tert-Butyl alanine). In another preferred embodiment, the hBCMA-binding polypeptide is one which does not have a methionine residue at positions X9, X10, X14, X18, X31or X35, for example an hBCMA-binding polypeptide wherein Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9is N; X10is Q; X11is F; X14is E; X17is A; X18A; X25is Y; X31is I; X33is K; and X35is norleucine, homoleucine, or tert-Butyl alanine. In certain embodiments of the present invention, the hBCMA-binding polypeptide is one that does not have a methionine residue at position X35. In certain embodiments of the present invention, the hBCMA-binding polypeptide is one that has a I, L, V, Q, norleucine, homoleucine, tert-Butyl alanine at position X35. Preferably, in the embodiments described above, the hBCMA binding efficacy is at least 1% at least 5%, or at least 10% (for example at least 15%, 20% 25% or 50%) of the binding efficacy of the peptide of SEQ ID NO: 2 (i.e. binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions). Preferably, in the embodiments described above, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2. In advantageous embodiments of hBCMA-binding polypeptides of the invention, Proline (P) and Cysteine (C) are not present in Helix 1 or Helix 2 of a hBCMA-binding polypeptides of the invention. Advantageously Glycine (G) is also not present in Helix 1 or Helix 2 of a hBCMA-binding polypeptides of the invention. In certain embodiments of the invention, such as the embodiments described above, the hBCMA-binding polypeptide is one wherein: Helix 1 comprises the sequence X6X7X8X9X10X11ADX14EIX17X18X19and / or Helix 2 comprises the sequence X23FX25QKWAFX31RX33LX35X36X37, 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; X19may 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 acid 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 acid. In another preferred embodiment, X6may be D, E, N or Q or is absent; X7may be H, K or R or is absent; X8may be D, E, N or Q or is absent; X19may be G, A, V, L or I or is absent; X23may be D, E, N or Q or is absent; X36may be D, E, N or Q or is absent; and X37may be D, E, N or Q or is absent; In another preferred embodiment, X6may be D, E, N or Q; X7may be H, K or R; X8may be D, E, N or Q; X19may be G, A, V, L or I; X23may be D, E, N or Q; X36may be D, E, N or Q; and X37 may be D, E, N or Q. 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 N 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 N; X36is D; and X37is D. In such embodiments, Helix 1 comprises the sequence NKEX9X10X11ADX14EIX17X18L and / or Helix 2 comprises the sequence NFX25QKWAFX31RX33LX35DD, In advantageous embodiments of hBCMA-binding polypeptides of the invention, Proline (P) and Cysteine (C) are not present in Helix 1 or Helix 2. Advantageously Glycine (G) is also not present in Helix 1 or Helix 2. Preferably, such an hBCMA-binding polypeptide has an hBCMA binding efficacy that is at least 1% of SEQ ID NO.2. In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2 for being of hBCMA. In another preferred embodiment, the hBCMA-binding polypeptide is one wherein: i) Helix 1 comprises the sequence NKEETFADLEISNL and Helix 2 comprises the sequence NFYQKWAFIRSLMDD, 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 2 (for example 1 or 2) residues are replaced by an alternative residue, or (iii) 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). Preferably, such an hBCMA-binding polypeptide is one wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO: 1. In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 1. In another preferred embodiment, the hBCMA-engaging polypeptide is one wherein: i) Helix 1 comprises the sequence NKENQFADEEIAAL and Helix 2 comprises the sequence NFYQKWAFIRKLMDD, 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 2 (for example 1 or 2) residues are replaced by an alternative residue or (iii) 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). Preferably, such a hBCMA-binding polypeptide is one wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO: 2. In certain embodiments, alternatively, or additionally, the hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2. In one embodiment, the hBCMA-binding polypeptide is one wherein: a) Helix 1 comprises the sequence ETFADLEISN and Helix 2 comprises the sequence FYQKWAFIRSLM. For example, Helix 1 comprises the sequence NKEETFADLEISNL and Helix 2 comprises the sequence NFYQKWAFIRSLMDD. In a further embodiment, the hBCMA-binding polypeptide is one wherein b) Helix 1 comprises the sequence NQFADEEIAA and Helix 2 comprises the sequence FYQKWAFIRKLM. For example, Helix 1 comprises the sequence NKENQFADEEIAAL and Helix 2 comprises the sequence NFYQKWAFIRKLMDD. As described herein above, a number of residues may each be substituted by an alternative residue. For example, at least 1 and no more than 3, at least 1 and no more than 2, or 1 residue may be substituted by an alternative residue, for example 3, 2, or 1 residues may be substituted by an alternative residue. An amino acid residue replacement may be a conservative or a non-conservative replacement, or a non-canonical (also known as unnatural) amino acid, as described herein above. In advantageous embodiments of hBCMA-binding polypeptides of the invention, Proline (P) and Cysteine (C) are not present in Helix 1 or Helix 2. Advantageously Glycine (G) is also not present in Helix 1 or Helix 2. In one embodiment, the hBCMA binding motif, being the portion [Helix 1]- [Separating portion]-[Helix 2], is (i.e. has a sequence): X6X7X8X9X10X11ADX14EIX17X18X19X20X21X22X23FX25QKWAFX31RX33LX35X36X37wherein 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 or Q or is absent; X7may be H, K or R or is absent; X8may be D, E, N or Q or is absent; X9, X10, X11, X14, X17and X18are as defined above; X19may be G, A, V, L or I or is absent; X20may be S, T, M, P, F, Y or W (for example P); X21may be D, E, N or Q; X22may be G, A, V, L, I or is absent; X23may be D, E, N or Q or is absent; X25,X31, X33and X35are as defined above; X36may be D, E, N or Q or is absent; and X37 may be D, E, N or Q or is absent. For example, X6may be D, E, N or Q; X7may be H, K or R; X8may be D, E, N or Q; X9, X10, X11, 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); X21may be D, E, N or Q; X22may be G, A, V, L, I; X23may be D, E, N or Q; X25,X31, X33and X35are as defined above; X36may be D, E, N or Q; and X37may be D, E, N or Q. In an especially preferred embodiment, X6is N; X7is K; X8is E; X9, X10, X11, X14, X17and X18are as defined above; X19is L; X20is S, T, M, P, F, Y or W (for example P), X21is D, E, N or Q (for example N); X22is G, A, V, L or, I (for example L); X23is N; X25,X31, X33and X35are as defined above; X36is D; and X37is D. For example, the X9to X35portion of the hBCMA binding motif is selected from the group consisting of SEQ ID NO.s 1036 to 1042 of Figure 16, and:

[0004] In a polypeptide of the Figure 16 or the table 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 another preferred embodiment, the sequence is the one of SEQ ID 170 - 275. In another preferred embodiment, the hBCMA binding motif is selected from the group consisting of SEQ ID NO.s 1036 to 1042 of Figure 16 and:

[0005] In a polypeptide of the Figure 16 or the table 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 another preferred embodiment, the hBCMA binding motif is selected from the group consisting of SEQ ID NO.s 1036 to 1042 of Figure 16. In a polypeptide of Figure 16, 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 another preferred embodiment, the hBCMA binding motif is selected from the group consisting of: In a polypeptide of the table 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 another preferred embodiment, the hBCMA binding motif is selected from the group consisting of: In a polypeptide of the table 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 preferred embodiments, the hBCMA binding 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 hBCMA binding motif sequence may be selected from: NKEX9X10X11ADX14EIX17X18X19X20X21X22X23FX25QKWAFX31RX33LX35X36X37; X6X7X8X9X10X11ADX14EIX17X18X19X20X21X22X23FX25QKWAFX31RX33LX35DD; and; NKEX9X10X11ADX14EIX17X18X19X20X21X22X23FX25QKWAFX31RX33LX35DD. 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 hBCMA is maintained. For example, the hBCMA binding efficacy is at least 1% of the binding efficacy of the peptide of SEQ ID NO: 2 (i.e. binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA 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 hBCMA-binding polypeptide is one that competes with SEQ ID NO: 2 for hBCMA binding. More preferably, 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: 2 ((i.e. binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions). In advantageous embodiments of hBCMA-binding polypeptides of the invention, Proline (P) and Cysteine (C) are not present in the hBCMA binding motif. Advantageously Glycine (G) is also not present in the hBCMA binding motif. As described herein above, the hBCMA-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 1 to 5 (preferably 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, Q, and X22is G, A, V, L, I; wherein optionally one or two (for example one) of X20, X21 or X22 are absent. In one embodiment, X20is P, S, C, U, T, or M, 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 XaXbX1X2X3X4X5,wherein Xais any naturally occurring amino acid (for example M) or is absent; Xbis any naturally occurring amino acid (for example M) or is absent; 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 XaXbX1X2X3X4X5,wherein Xais M or is absent; Xbis M or is absent; X1is G, A, V, L, I or is absent, X2is D, E, N or Q or is absent, X3is D, E, N or Q or is absent, X4is H, K, R or is absent, and X5is F, Y, W or is absent. More preferably, Xais M or is absent; Xbis M or is absent; X1is 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. More preferably, Xais M or is absent; Xbis M or is absent; X1is 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 Xa, Xb, X1, X2, X3,X4and X5is absent; or Xa, and / or Xbare absent and the other residues are not absent; or Xa, Xb, and X1are absent and the other residues are not absent; or Xa, Xb, X1and X2are absent and the other residues are not absent; Xa, Xb, X1, X2and X3are absent and the other residues are not absent; Xa, Xb, X1, X2, X3and X4are absent and the other residue is not absent; or all of Xa, Xb, X1, X2, X3 ,X4 and X5 are absent. In certain embodiments, preferably none of X1, X2, X3,X4and X5is absent; X1is absent and the other residues are not absent; X1and X2are 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 such embodiments, optionally Xa, and / or Xbare absent. In certain especially preferred embodiments, the N-terminal portion has the sequence XaXbX1X2X3X4X5, wherein: Xa, and Xbare M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; or Xa, and Xbare absent, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; or Xa, and Xbare absent, X1is absent, X2is D, X3is N, X4is K, and X5is F; or Xa, and Xbare absent, X1is absent, X2is absent, X3is N, X4is K, and X5 is F; or Xa, and Xbare absent, X1is absent, X2is absent, X3is absent, X4is K, and X5is F; Xa, and Xbare absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is F; or Xa, and Xbare absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent. In certain embodiments, 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) 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; X5is any naturally occurring amino acid (preferably F, Y or W; more preferably F) or is absent. In certain embodiments, preferably none of X1, X2, X3,X4and X5is absent; or Xa, and / or Xbare absent and the other residues are not absent; or Xa, Xb, and X1are absent and the other residues are not absent; or Xa, Xb, X1and X2are absent and the other residues are not absent; Xa, Xb, X1, X2and X3are absent and the other residues are not absent; Xa, Xb, X1, X2, X3and X4are absent and the other residue is not absent; or all of Xa, Xb, X1, X2, X3,X4and X5are absent. For example, the N-terminal portion has the sequence X1X2X3X4X5, wherein: 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 X5 is F; or X1 is absent, X2 is absent, X3 is N, X4 is K, and X5 is F; or X1 is absent, X2 is absent, X3is absent, X4is K, and X5is F; or 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. In one embodiment, X1is absent, X2is absent, X3is absent, X4is absent and X5is any naturally occurring amino acid, and preferably G, F, Y or W; and more preferably G. In one embodiment, X1is absent, X2is absent, X3is absent, X4is absent and X5is G. 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 hBCMA-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, X39is any naturally occurring amino acid, X56is any naturally occurring amino acid or is absent, X57 is 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. 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, K 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, K 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 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 X58 is 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 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 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, 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 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 an alternative preferred the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X38is P, and X39is S; and: X56is K, 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 K, 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 XaXbX1X2X3X4X5wherein Xais M, Xbis M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; Xais absent, Xbis M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is D, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is absent, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is F; or Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent (for example, Xais M, Xbis M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; or Xais absent, Xbis absent, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; or Xais absent, Xbis absent, 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 XaXbX1X2X3X4X5wherein Xais M, Xbis M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is D, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is absent, X3is N, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is K, and X5is F; Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is F; or Xais absent, Xbis absent, X1 is absent, X2 is absent, X3 is absent, X4 is absent, and X5 is absent (for example, Xais M, Xbis M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F, or Xais absent, Xbis absent, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F, or Xais absent, Xbis absent, 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 embodiment, the N-terminal portion has the sequence XaXbX1X2X3X4X5wherein Xais M, Xbis M, 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, Xais M, Xbis M, X1is V or G (preferably V), X2is D, X3is N, X4is K, and X5is F); and the C-terminal portion has the 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 X58s 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 embodiment, the N-terminal portion has the sequence XaXbX1X2X3X4X5wherein Xais M, Xbis M, 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, Xais M, Xbis M, 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 X58 is H, K, or R (preferably K); X56 is G, A, V, L or I (preferably A); X57 is P, and X58 is absent; X56is G, A, V, L or I (preferably A), X57is absent, and X58is absent; or X56is absent, X57is absent, and X58s 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 another 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 Xais absent, Xbis absent, 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 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 Xais absent, Xbis absent, X1is absent, X2is absent, X3 is absent, X4 is absent, and X5 is absent (for example, X1 is V or G (preferably V), X2 is 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 another 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 X58s 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 another 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), X57 is absent, and X58 is absent; or X56 is absent, X57 is absent, and X58 s 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 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 an alternative very preferred embodiment Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is absent; 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 XaXbX1X2X3X4X5 ;and / or the C- terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58; wherein, in said separating portion, X20is P; X21is N; X22is L; wherein in said N-terminal portion, Xais M or absent; Xbis M or absent; 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. In such embodiments, preferably the separating portion has the sequence PNL. Alternatively, or additionally, in such embodiments, the N-terminal portion has the sequence MMVDNKF or VDNKF. In another embodiment, the N-terminal portion may comprise the sequence X1X2X3X4X5, wherein: X1is G, 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 sequence DNKF, the sequence NKF, the sequence KF, or the sequence F. The separating portion may comprise the sequence PNL. 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. For example, the C-terminal portion may comprise the sequence PSQSANLLAEAKKLNDAQAPK. 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 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 at least 1 and no more than 2. For example, there may be 1, 2, 3, 4 or 5 replacement residues in total in those portions. In advantageous embodiments of hBCMA-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), 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. Thus, across the entire hBCMA-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 18 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 18, at least 1 and no more than 17, at least 1 and no more than 16, at least 1 and no more than 15, at least 1 and no more than 14, at least 1 and no more than 13, at least 1 and no more than 12, at least 1 and no more than 11, at least 1 and no more than 10, at least 1 and no more than 9, at least 1 and no more than 8, at least 1 and no more than 7, or at least 1 and no more than 6. Particularly, there may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 1415, 16, 17, or 18 replacement residues in total across the entire overall structure [N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]. An amino acid residue replacement may be a conservative or a non-conservative replacement, or a non- canonical (also known as unnatural) amino acid, as described herein above. Preferably, across the entire hBCMA-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 15 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 13, at least 1 and no more than 12, at least 1 and no more than 11, at least 1 and no more than 10, at least 1 and no more than 9, at least 1 and no more than 8, at least 1 and no more than 7, or at least 1 and no more than 6. Particularly, there may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 replacement residues in total across the entire overall structure [N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]. An amino acid residue replacement may be a conservative or a non-conservative replacement, or a non-canonical (also known as unnatural) amino acid, as described herein above. In one aspect of the invention, the hBCMA-binding polypeptide comprises a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, or 121-128 (as shown in Table 1) and 1027-1035 (as shown in Figure 15). In such sequences, 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. In one embodiment, the hBCMA binding polypeptide comprises a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, 121-128 and. In one embodiment, the hBCMA binding polypeptide has a sequence selected from the group consisting of SEQ ID NOs.1, 2, 23-39, 41-119, 121-128 and 1027-1035. In one aspect of the invention, the hBCMA-binding polypeptide comprises a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, or 121-128 as shown in Table 1. In such sequences, 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. In one embodiment, the hBCMA binding polypeptide comprises a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, or 121-128. In one embodiment, the hBCMA binding polypeptide has a sequence selected from the group consisting of SEQ ID NOs.1, 2, 23-39, 41-119, or 121-128. In one aspect of the invention, the hBCMA-binding polypeptide comprises a sequence selected from and 1027-1035 (as shown in Figure 15). In such sequences, 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. In one embodiment, the hBCMA binding polypeptide comprises a sequence selected from SEQ ID NOs.1027-1035. In one embodiment, the hBCMA binding polypeptide has a sequence selected from the group consisting of SEQ ID NOs.1027-1035. In one aspect of the invention, the hBCMA-binding polypeptide comprises a sequence selected from SEQ ID NOs.2 and 23-39, as shown in Table 1. In such sequences, 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. In one embodiment, the hBCMA binding polypeptide comprises a sequence selected from SEQ ID NOs.2 and 23-39. In one embodiment, the hBCMA binding polypeptide has a sequence selected from the group consisting of SEQ ID NOs.2 and 23-39. In one aspect of the invention, the hBCMA-binding polypeptide comprises the sequence: a)VDNKFNKEETFADLEISNLPNLNFYQKWAFIRSLMDDPSQSANLLAEAKKLNDAQAP K [SEQ ID NO: 1]; In a further aspect of the invention, the hBCMA-binding polypeptide comprises the sequence: b)VDNKFNKENQFADEEIAALPNLNFYQKWAFIRKLMDDPSQSANLLAEAKKLNDAQA PK [SEQ ID NO: 2]. In a further aspect of the invention, the hBCMA-binding polypeptide comprises the sequence c)VDNKFNKEEIFADREIAFLPNLNFYQKWAFIRKLMDDPSQSANLLAE AKKLNDAQAPK [SEQ ID NO: 23]. In a further aspect of the invention, the hBCMA-binding polypeptide comprises the sequence c)VDNKFNKEHQFADYEIAMLPNLNFYQKWAFIRSLMDDPSQSANLLA EAKKLNDAQAPK [SEQ ID NO: 33]. As described herein 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), c) or d) 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 disclosed herein above, in an embodiment, Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, 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; X25is F or Y; X31is I, M, or V; X33is K or S; X35is I, L, M, or V. In this embodiment, as in other embodiments, a number of residues may each be substituted by an alternative residue, as described herein. In any such alternative polypeptide of the invention with alternative residues in place, binding to hBCMA is maintained. For example, the hBCMA binding efficacy is at least 0.1% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. With 0.1% binding efficacy, it is understood that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 1000 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. More preferably, the binding efficacy is at least 0.5%, 1%, 2%, 4%, 5%, 10%, 20%, 25%, or 50% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. That is to say that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 500 times, 100 times, 50 times, 25 times, 20 times, 10 times, 5 times, 4 times or 2 times the EC50 concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. As disclosed herein above, in another embodiment, Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FYQKWAFIRX33LM , wherein, independently from each other, X9is D, E, H, K, N, Q, S, or V; X10is A, E, F, I, K, M, N, Q, R, S, T, Y, or V; X11is E, F, or H; X14is A, E, H, I, K, L, Q, R, T, or Y; X17is A, E S, T, or V; X18is A, F, H, K, L, M, N, T, or S; X33is K or S. In this embodiment, as in other embodiments, 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 hBCMA is maintained. For example, the hBCMA binding efficacy is at least 0.1% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. With 0.1% binding efficacy, it is understood that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 1000 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. More preferably, the binding efficacy is at least 0.5%, 1%, 2%, 4%, 5%, 10%, 20%, 25%, or 50% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. That is to say that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 500 times, 100 times, 50 times, 25 times, 20 times, 10 times, 5 times, 4 times or 2 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. As disclosed herein above, in another embodiment, Helix 1 comprises the sequence ETFADLEISN and Helix 2 comprises the sequence FYQKWAFIRSLM. In this embodiment, as in other embodiments, 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 hBCMA is maintained. For example, the hBCMA binding efficacy is at least 0.1% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. With 0.1% binding efficacy, it is understood that the EC50 concentration of the alternative polypeptide for binding to hBCMA is no more than 1000 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. More preferably, the binding efficacy is at least 0.5%, 1%, 2%, 4%, 5%, 10%, 20%, 25%, or 50% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. That is to say that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 500 times, 100 times, 50 times, 25 times, 20 times, 10 times, 5 times, 4 times or 2 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. As also disclosed herein above, in another embodiment, Helix 1 comprises the sequence NQFADEEIAA and Helix 2 comprises the sequence FYQKWAFIRKLM. In this embodiment, as in other embodiments, 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 hBCMA is maintained. For example, the hBCMA binding efficacy is at least 0.1% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. With 0.1% binding efficacy, it is understood that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 1000 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. More preferably, the binding efficacy is at least 0.5%, 1%, 2%, 4%, 5%, 10%, 20%, 25%, or 50% of the binding efficacy of the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. That is to say that the EC50concentration of the alternative polypeptide for binding to hBCMA is no more than 500 times, 100 times, 50 times, 25 times, 20 times, 10 times, 5 times, 4 times or 2 times the EC50concentration for the peptide of SEQ ID NO: 2 to hBCMA, when measured under the same conditions. The invention further provides an hBCMA-binding polypeptide, wherein the hBCMA- binding polypeptide consists of one motif that binds to hBCMA, wherein said polypeptide consists of 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] wherein the hBCMA-binding motif sequence is selected from SEQ ID No.1036 to 1042 of Figure 16 (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 hBCMA-binding polypeptide, which consists of a hBCMA -binding polypeptide of the invention wherein the sequence of the hBCMA- binding polypeptide is selected from SEQ ID NOs 1027 to 1035 of Figure 15; and optionally comprising an additional binding moiety. The invention further provides a hBCMA-binding polypeptide of the invention, wherein the hBCMA-binding polypeptide consists of the hBCMA-binding polypeptide (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 embodiment the hBCMA-binding polypeptide (for example a hBCMA-binding polypeptide of the invention described above or below) consists of one motif that binds to hBCMA, wherein said polypeptide consists of 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] wherein the hBCMA -binding motif sequence is selected from SEQ ID No.1036 to 1042 of Figure 16 (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 embodiment the hBCMA-binding polypeptide consists of a hBCMA-binding polypeptide of the present invention wherein the sequence of the hBCMA-binding polypeptide is selected from SEQ ID NOs 1027 to 1035 of Figure 15; (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 an hBCMA-binding polypeptide, wherein the hBCMA- binding polypeptide consists of one motif that binds to hBCMA, wherein said polypeptide consists of 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] 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 hBCMA-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein.. The invention further provides a hBCMA-binding polypeptide, which consists of a hBCMA-binding polypeptide of the invention; and comprising an additional binding moiety; and wherein the hBCMA-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. The invention further provides a hBCMA-binding polypeptide of the invention, wherein the hBCMA-binding polypeptide consists of the hBCMA-binding polypeptide 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 hBCMA-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. In one embodiment the hBCMA-binding polypeptide (for example a hBCMA-binding polypeptide of the invention described above or below) consists of one motif that binds to hBCMA, wherein said polypeptide consists of 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] 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 hBCMA-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. In one embodiment the hBCMA-binding polypeptide consists of a hBCMA-binding polypeptide of the present 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 hBCMA- 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 the hBCMA-binding motif and / or a hBCMA-binding polypeptide consists of a hBCMA-binding motif and / or a hBCMA-binding polypeptide of the invention, the hBCMA-binding polypeptide is not connected to a further hBCMA-binding polypeptide, i.e. the hBCMA-binding polypeptide is not a portion of a hBCMA-binding oligomer of the invention. In another embodiment the hBCMA-binding polypeptide (for example a hBCMA- binding polypeptide of the invention described above or below) consists of one motif that binds to hBCMA, wherein said polypeptide consists of 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], 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) ; and wherein the hBCMA-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. In another very preferred embodiment the hBCMA-binding polypeptide consists of a hBCMA-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 hBCMA-binding polypeptide and an additional functional portion are separated by a linker of the present invention as described herein. Multimeric hBCMA-binding polypeptides: hBCMA-binding oligomers In certain aspects, the present invention provides a hBCMA-binding oligomer which comprise at least two (i.e. two, or more than two, for example 2, 3, 4, 5, 6 or more; preferably 2, 3 or 4) hBCMA-binding polypeptides of the present invention, wherein the hBCMA-binding polypeptides of a hBCMA-binding oligomers of the invention are connected via one or more linkers of the present invention as described herein. In one preferred embodiment, the hBCMA-binding oligomer of the present invention comprises two hBCMA-binding polypeptides of the present invention. In another embodiment, a hBCMA-binding oligomer of the present invention comprises at least three, at least four, at least 5 or at least 6 hBCMA-binding polypeptides of the present invention, for example 3, 4, 5 or 6 or more hBCMA-binding polypeptides of the present invention. The hBCMA-binding polypeptides of a hBCMA-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. An hBCMA-binding oligomer of the present invention is a multimeric binder, as it has multiple hBCMA binding motifs, i.e. it has a hBCMA binding motif ([Helix 1]- [Separating portion]-[Helix 2]) in each hBCMA-binding polypeptide it comprises. This aspect of the invention may also be defined such that the hBCMA-binding polypeptide constitutes two or more hBCMA-binding moieties or hBCMA-binding peptides connected via one or more linkers as described herein, for example two, three, four, five, six or more hBCMA-binding moieties or hBCMA-binding peptides optionally connected via one or more linkers as described herein, for example two, three, or four hBCMA-binding moieties or hBCMA-binding peptides optionally connected via one or more linkers as described herein, for example two hBCMA- binding moieties or hBCMA-binding peptides optionally connected via one or more linkers as described herein. This definition is used in the numbered embodiments of the invention below to refer to the hBCMA-binding oligomers aspects of the invention. An hBCMA-binding oligomer of the present invention comprises, at least, a first hBCMA-binding polypeptide which is an hBCMA-binding polypeptide of the present invention, and a second hBCMA-binding polypeptide which is a hBCMA-binding polypeptide of the present invention. The first and second hBCMA-binding polypeptides may have the same sequence. Alternatively, the first and second hBCMA-binding polypeptides may have different sequences. An hBCMA-binding oligomer of the present invention may optionally further comprise a third hBCMA- binding polypeptide which is a hBCMA-binding polypeptide of the present invention. The third hBCMA-binding polypeptides may have the same sequence as the first and / or second hBCMA-binding polypeptides sequences. Alternatively, the third hBCMA-binding polypeptide may have a different sequence to the first and second hBCMA-binding polypeptides. An hBCMA-binding oligomer of the present invention may optionally further comprise a fourth hBCMA-binding polypeptide which is a hBCMA-binding polypeptide of the present invention. The fourth hBCMA-binding polypeptides may have the same sequence as the first and / or second and / or third hBCMA-binding polypeptides sequences. Alternatively, the fourth hBCMA-binding polypeptide may have a different sequence to the first, second and third hBCMA- binding polypeptides. In one preferred embodiment, an hBCMA-binding oligomer of the present invention comprises a first hBCMA-binding polypeptide that comprises a first binding motif selected from SEQ ID NOs.170 to 275 and 1036 to 1042 (preferably from SEQ ID NOs. 170-188) (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 hBCMA-binding polypeptide that comprises a second binding motif selected from SEQ ID NOs.170 to 275 and 1036 to 1042 (preferably from SEQ ID NOs.170-188) (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 hBCMA-binding motifs may have the same sequence or a different sequence. In one preferred embodiment, an hBCMA-binding oligomer of the present invention comprises a first hBCMA-binding polypeptide that has a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, 121-128 and 1027 to 1035 (preferably SEQ ID NOs.2 and 23-39) (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 hBCMA-binding polypeptide that has a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, or 121-128 and 1027 to 1035 (preferably SEQ ID NOs.2 and 23-39) (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 hBCMA-binding polypeptide may have the same sequence or a different sequence. The hBCMA-binding polypeptides in a hBCMA-binding oligomer of the present invention may be separated by a linker. For example, each hBCMA-binding polypeptide in a hBCMA-binding oligomer of the present invention may be separated by a linker. Preferably, the linker is a linker as defined herein, for example a flexible amino acid linker, a rigid amino acid linker or cleavable amino acid linker or non- amino acid linker. Where a hBCMA-binding oligomer of the present invention comprises more than one linker, the linkers may be the same, or may be different. Preferably, a linker for a hBCMA-binding oligomer of the present invention comprises or has a sequence of 1 to 50 (for example 1 to 25, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25) naturally occurring amino acids; and preferably 1 to 20 (for example 1, 5, 10, 15, or 20; and more preferably 1 to 15) naturally occurring amino acids, for example selected from the group consisting of G, S and T (preferably G and S). For the avoidance of doubt, when used herein “[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]” means that the hBCMA 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 hBCMA 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 hBCMA binding polypeptide (as well as that the hBCMA 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 hBCMA binding polypeptide (as well as that the hBCMA binding polypeptide sequence is C-terminus to N-terminus, left to right). For the avoidance of doubt, when used herein “[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion]” means that the CD16a binding polypeptide sequence is N-terminus to C-terminus, left to right; and when used herein “[CD16a C-terminal portion]-[CD16a Helix 2]- [CD16a Separating portion]-[CD16a Helix 1]-[CD16a 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 “ -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a 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 “ -[CD16a C-terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a 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). In one embodiment, the hBCMA-binding oligomer of the present invention comprises at least 2 (for example 2) hBCMA-binding polypeptides, and the hBCMA- 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 hBCMA 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 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. In embodiments where the linker is attached to the [N-terminal portion] of a hBCMA binding polypeptide, preferably the N-terminal portion has the sequence X1X2X3X4X5 and 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 hBCMA 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, wherein y is 1 to 10 (for example

[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, preferably the linker comprises (or is) a group selected from the group consisting of

[0007] . In one embodiment, the hBCMA-binding oligomer of the present invention comprises at least 3 (for example 3) hBCMA-binding polypeptides. For example, the hBCMA-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]; and 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 hBCMA 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 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). 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 n is 1 to 30 (for example 1 to 24 or 2 to 8). In one embodiment, the hBCMA -binding oligomer of the present invention comprises at least 3 (for example 3) hBCMA-binding polypeptides, wherein the hBCMA-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 hBCMA 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 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. 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. In such embodiments the linker may optionally additionally In another embodiment, the hBCMA-binding oligomer of the present invention comprises at least 3 (for example 3) hBCMA-binding polypeptides, wherein the hBCMA-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 hBCMA 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 one embodiment, preferably the linker comprises one or more group selected from the group consisting of , ,

[0008] . In some aspects of the invention, the hBCMA-binding oligomer constitutes two or more hBCMA-binding polypeptides optionally connected via one or more linkers as described herein, for example two, three, four, five, six or more hBCMA-binding polypeptides optionally connected via one or more linkers as described herein, for example two, three, or four hBCMA-binding polypeptides optionally connected via one or more linkers as described herein, for example two hBCMA-binding polypeptides optionally connected via one or more linkers as described herein. In certain embodiments of the present invention, a hBCMA -binding oligomer of the present invention may comprise two hBCMA-binding polypeptides, each of which has a sequence in which Helix 1 comprises the sequence NKEETFADLEISNL and Helix 2 comprises the sequence NFYQKWAFIRSLMDD. As set out elsewhere, such portions may have a number of residues substituted by an alternative residue. For example, each of the two polypeptides may have the sequence: VDNKFNKEETFADLEISNLPNLNFYQKWAFIRSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. In an alternative example, such an oligomer may comprise two hBCMA-binding polypeptides, each of which has a sequence in which Helix 1 comprises the sequence NKENQFADEEIAAL and Helix 2 comprises the sequence NFYQKWAFIRKLMDD. As set out elsewhere, such portions may have a number of residues substituted by an alternative residue. For example, each of the two polypeptides may have the sequence: VDNKFNKENQFADEEIAALPNLNFYQKWAFIRKLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 2]. In an alternative example, such an oligomer may comprise two hBCMA-binding polypeptides, one of which has a sequence in which Helix 1 comprises the sequence NKEETFADLEISNL and Helix 2 comprises the sequence NFYQKWAFIRSLMDD , and the other of which has a sequence in which Helix 1 comprises the sequence NKENQFADEEIAAL and Helix 2 comprises the sequence NFYQKWAFIRKLMDD. As set out elsewhere, such portions may have a number of residues substituted by an alternative residue. For example, one of the two polypeptides may have the sequence: VDNKFNKEETFADLEISNLPNLNFYQKWAFIRSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]. and The other may have the sequence: VDNKFNKENQFADEEIAALPNLNFYQKWAFIRKLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 2]. 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 hBCMA binding polypeptides of the present invention (for example in a hBCMA-binding oligomer of the invention), or a linker may connect together a hBCMA 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 hBCMA binding polypeptides of the present invention, or connect a hBCMA binding polypeptide of the present invention and an additional functional portion (for example a CD16a 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 hBCMA binding polypeptide of the present invention or an additional functional portion (for example a CD16a binding polypeptide)). For example, a linker may connect two hBCMA binding polypeptides and one additional functional portions (for example one CD16a binding polypeptide). Alternatively, for example, a linker may connect four polypeptides, for example it may connect two hBCMA binding polypeptides and two additional functional portions; or three hBCMA binding polypeptides and one additional functional portions. For the avoidance of doubt one hBCMA binding polypeptide, or hBCMA binding oligomer, or additional functional portion (for example a CD16a 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 hBCMA binding polypeptide of the present invention, a hBCMA binding oligomer of the present invention, or an additional functional portion (for example a CD16a 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, group, wherein z is 1 to 4. 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 Examples of tricyclic rings comprising a triazole ring include, but are not limited to, Examples of tetracyclic rings comprising a triazole ring include, but are not limited to, dibenzocyclooctane and dibenzoazacyclooctane,

[0009] Examples of bicyclic rings comprising a pyridazine ring include, but are not limited to,

[0010] Examples of tricyclic rings comprising a pyridazine ring groups include, but are not . The structure of 1H-pyrrole-2,5-dione is as follows: embodiments, the linker may comprise two 1H-pyrrole-2,5-dione groups, for 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). In embodiments wherein the linker comprises group, the linker preferably comprises the following structure,

[0011] . 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 a group, wherein z is 1 to 4 (for example 1 or 2, and preferably 1) and especially a

[0012] example z is 1 and the group i or 2, for example z is 2 and the group is certain embodiments, the linker comprises (or is) a group selected from

[0013] 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 g p, g p . In one preferred embodiment, a linker of the present invention comprises (or is) a . , resent invention comprises (or is) a group, for example a linker of the present invention comprises (or is) a group selected from .In certain very preferred embodiments, the linker is In further embodiments, the linker is:

[0014] 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 group, for example 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 hBCMA binding polypeptide of the invention. For example, in embodiments where the linker is attached to the [N-terminal portion] of a hBCMA 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 hBCMA 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 herein y is 1 to 10 (for example 1 to 5),

[0015] . 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 triazole and in particular one or two groups selected from the group consisting of

[0016] . 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: 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, , , , , 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 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: , ,

[0017]

[0018] 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,or 2 to 8, and especially 2, 3 or 4); and optionally 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 to 10(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 two hBCMA binding polypeptides and one additional functional portion (e.g. one CD16a binding portion), one hBCMA binding polypeptide and two additional functional portions (e.g. one CD16a binding portion and one additional functional portion)), 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 two hBCMA binding polypeptides and one additional functional portion (e.g. one CD16a binding portion), one hBCMA binding polypeptide and two additional functional portions (e.g. one CD16a binding portion and one additional functional portion)) of the polypeptides of the invention, preferably the linker comprises (or consists of) the following group:

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

[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) , 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) and , 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: 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) 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 example, the linker comprises (or is) the following ,

[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, SGGSGG, GGSGGSG, GSGGSGG, GGSGGSGK, or KGSGGSGG. In another embodiment, for example, a linker of the present invention may additionally comprises the sequence GGGSG, GGGSGGGGSG, GGGSGGGGSGGGGSG, GGGSGGGGSGGGGSGGGGSG, GGGGS, GGGGSGGGGS, GGGGSGGGGSGGGGS, GGGGSGGGGSGGGGSGGGGS, GGSGG, GGSGGGGSGG, GGSGGGGSGGGGSGG, GGSGGGGSGGGGSGGGGSGGGGSGG, GSGGG, GSGGGGSGGG, GSGGGGSGGGGSGGG, GSGGGGSGGGGSGGGGSGGG, SGGGG, SGGGGSGGGG, SGGGGSGGGGSGGGG, or SGGGGSGGGGSGGGGSGGGG. 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; a “-“ or curved lines represent bonds (the curved line is used to explicitly show a bond between two N-termini or between two C-termini ): 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; 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; 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; 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

[0026] 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 hBCMA binding polypeptide, or a hBCMA-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 hBCMA-binding polypeptides, for example in a hBCMA-binding oligomer of the present invention, or is between, and thus separates, one or more hBCMA-binding polypeptide or one or more hBCMA-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 hBCMA-binding polypeptides (for example in a hBCMA-binding oligomer of the present invention), or is between, and thus separates, one or two or more hBCMA- 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 hBCMA- 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 hBCMA-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. 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 hBCMA-binding polypeptides (for example in a hBCMA-binding oligomer of the present invention), or is between, and thus separates, one or two or more hBCMA- 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, and especially a CD16a binding polypeptide). IN preferred embodiments, said linker is between, and thus separates, two hBCMA- binding polypeptides (i.e. in a hBCMA-binding oligomer of the present invention) and one additional binding moiety (for example as described in further detail below, and especially a CD16a binding polypeptide). 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 hBCMA- 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 hBCMA-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 An hBCMA binding polypeptide as disclosed herein may be attached via a linker as described herein to one or more additional functional portions, for example a binding partner recognising an immune cell surface molecule. An hBCMA binding oligomer as disclosed herein may be attached via a linker as described herein to one or more functional portions, for example a binding partner recognising an immune cell surface molecule. Therefore, one embodiment of the present invention provides a hBCMA binding polypeptide or a hBCMA 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 separated 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 or a derivative thereof. Examples of suitable signalling molecules include immune signalling molecules or derivatives thereof, for example cytokines or derivatives thereof, for example IL-15 and derivatives thereof. The one or more (i.e the 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 or cancer cell surface target). Cell surface tumour antigens may for example be tumour-associated antigens or tumour-specific antigens. Such additional binding moieties may for example be specific for an immune cell surface protein, for example an NK cell activating receptor, for example CD16a. In particular, such a CD16a-binding moiety may for example be an immune cell- engaging polypeptide as disclosed in International Application No. PCT / EP2023 / 064624. Such ‘dual engager’ binding polypeptides may for example comprise at least one hBCMA binding polypeptide as disclosed herein, for example one, two, three or more hBCMA binding polypeptides as disclosed herein, or at least one hBCMA binding oligomer as disclosed herein. The at least one (for example one, two, three or more) hBCMA binding polypeptide(s) as disclosed herein or at least one hBCMA binding oligomer as disclosed herein may for example be attached to at least one CD16a-binding polypeptide, for example to at least one (for example one) CD16a-binding polypeptide as described herein, for example one, two, three, or more CD16a-binding polypeptides as described herein. In such a ‘dual engager’ binding polypeptide, the additional binding moiety (for example a binding moiety specific for an immune cell surface molecule such as CD16a, for example the at least one CD16a-binding polypeptide as described herein) may be attached at the N- terminal portion (for example the N-terminus) or the C-terminal portion (for example the C-terminus) of the hBCMA binding moiety (for example, the at least one hBCMA binding polypeptide as disclosed herein or the at least one hBCMA binding oligomer as disclosed herein) separated by one or more linkers as described herein. The additional binding moiety (for example a binding moiety specific for an immune cell surface molecule such as CD16a, for example the at least one CD16a-binding polypeptide as described herein) may, alternatively, be attached between two hBCMA-binding moieties separated by one or more linkers as described herein. Non- limiting examples of such ‘dual engager’ binding polypeptides, comprising one hBCMA-binding polypeptide and one CD16a-binding polypeptide are provided in the Examples section below (for example see example compounds L1 to L16 of Synthetic Examples 10 and 11)Non-limiting examples of ‘dual engager’ polypeptides comprising two hBCMA-binding polypeptides and one CD16a-binding polypeptide are provided in the Examples section below (for example see example compounds L17 to L37 of Synthetic Examples 10 and 11) In certain embodiments, a hBCMA-binding polypeptide of the invention (for example an hBCMA-binding polypeptide incorporated into a ‘dual engager’ polypeptide, for example a dual engager polypeptide further comprising at least one moiety targeting an NK cell surface target, for example CD16a) is especially active in functional assays, e.g. a CD16 reporter assay and / or a cell killing assay. The skilled person will understand that such non-limiting examples of dual engagers (as well as other dual engagers comprising at least one hBCMA-binding polypeptide or at least one hBCMA binding oligomer disclosed herein attached to a CD16a- binding moiety, and other molecules comprising at least one hBCMA-binding polypeptide or at least one hBCMA binding oligomer attached to different functional portions (for example additional binding moieties as described below)) may optionally comprise one or more additional N-terminal, C-terminal or other modification, for example a C-terminal His6tag, depending on the intended use of the engager or requirements for expression, purification or the like. Non-limiting examples of such N-terminal, C-terminal or other modifications may include a peptide purification tag or moiety (for example a histidine-tag (for example a polyhistidine tag) 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 OmpA, DsbA, PhoA, and PelB), a fluorophore tag (for example Alexa448), 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 dual engagers comprising at least one hBCMA-binding polypeptide or at least one hBCMA binding oligomer as described herein. Further 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), and 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 of 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, 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. Alternatively or additionally, such additional binding moieties may for example be specific for a different target on multiple myeloma cells that is not hBCMA. For example, an additional binding moiety may bind to a different target on the same multiple myeloma cell. 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 an hBCMA binding polypeptide of the present invention. In embodiments of the present invention an hBCMA binding polypeptide or hBCMA- 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 hBCMA binding polypeptide or hBCMA-binding oligomer and a (for example the or each) additional functional portion are separated by a linker as described herein. For example, the hBCMA binding polypeptide or hBCMA-binding oligomer further comprises 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 hBCMA binding polypeptide or hBCMA-binding oligomer further comprises one or two additional functional portions (for example one or two additional binding moieties or signalling molecules). In certain preferred embodiments, at least one hBCMA binding polypeptide or hBCMA-binding oligomer is attached to one additional functional portion (for example one additional binding moiety or signalling molecule). In one especially preferred embodiment, a hBCMA- binding oligomer comprising two hBCMA-binding polypeptides further comprises one additional functional portion (for example one additional binding moiety or signalling molecule, for example a CD16a binding polypeptide). In another preferred embodiment, a hBCMA-binding polypeptide further comprises one additional functional portion (for example one additional binding moiety or signalling molecule, for example a CD16a binding polypeptide). An hBCMA-binding polypeptide or hBCMA-binding oligomer of the present invention comprising one or more (for example 1, 2, 3, 4, 5 or 6 or more) additional functional portions may be referred to as heteromultimeric. An hBCMA-binding polypeptide of the present invention consisting of one hBCMA-binding polypeptide and one additional functional portion only and no other functional portions (i.e. no further hBCMA-binding polypeptides functional portions or additional functional portions) may be referred to as heterodimeric. An hBCMA-binding polypeptide of the present invention consisting of one hBCMA-binding polypeptide and two additional functional portions only and no other functional portions may be referred to as heterotrimeric. An hBCMA-binding oligomer of the present invention consisting of two hBCMA-binding polypeptide functional portions and one additional functional portion only and no other functional portions may be referred to as a heterotrimeric. 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 portion or the C-terminal portion of an hBCMA-binding polypeptide or an hBCMA-binding oligomer, separated by a linker as described herein. One or more signalling molecule(s) may, alternatively, be attached between two hBCMA -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 hBCMA-binding polypeptide or a CD16a-binding oligomer via a linker as described herein. 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 protein (for example a NK cell surface protein, for example CD16a, NKp46, NKG2D, PD-1, especially CD16a). As mentioned above, an additional binding moiety, for example a binding partner recognising the NK cell surface protein CD16a, 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 hBCMA-binding polypeptide or a hBCMA-binding oligomer, separated by a linker as described herein. The one or more additional binding moiety(ies) may, alternatively, be attached between two hBCMA-binding polypeptides in a hBCMA- 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 NK cell surface protein CD16a, may be attached at the N-terminal portion (for example the N-terminus) or the C-terminal portion (for example the C-terminus) of an hBCMA-binding polypeptide or a hBCMA-binding oligomer separated by a linker as described herein. More preferably, the additional binding moiety(ies), for example a binding partner recognising the NK cell surface protein CD16a, may be attached at the C-terminal portion (for example the C- terminus) or the N-terminal portion (for example the N-terminus) of an hBCMA- binding polypeptide, separated by a linker as described herein. More preferably, one additional binding moiety, for example a binding partner recognising the NK cell surface protein CD16a, may be attached at the C-terminal terminal portion (for example the C-terminus) or the N-terminal portion (for example the N-terminus) of each hBCMA-binding polypeptide in a hBCMA-binding oligomer, separated by a linker as described herein. The present inventors have surprisingly found that a ‘dual engager’ polypeptide comprising a hBCMA binding polypeptide or a hBCMA binding oligomer as disclosed herein can retain its hBCMA binding ability when fused to an additional binding moiety targeting the NK cell surface protein CD16a. This ‘dual engager’ polypeptide comprising a hBCMA binding polypeptide as disclosed herein fused to a CD16a binding moiety is also surprisingly capable of activating NK cells in the presence of BCMA-expressing tumour cells. In one preferred embodiment, the hBCMA-binding polypeptide or hBCMA-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, the hBCMA-binding polypeptide or hBCMA-binding oligomer of the present invention further comprises 1, 2, 3, 4 or 5 additional functional portions. In especially preferred embodiments, the hBCMA-binding polypeptide or hBCMA-binding oligomer of the present invention further comprises one, two or three additional functional portions, and more preferably one or two, and most especially one. In especially preferred embodiments, the hBCMA-binding polypeptide or hBCMA-binding oligomer of the present invention further comprises one or two (preferably one) additional functional portions, wherein each additional functional portion is a CD16a binding polypeptide. In very especially preferred embodiments, the hBCMA -binding polypeptide of the present invention further comprises one or two (preferably one) additional functional portions, wherein the or each (preferably the) additional functional portion is a CD16a binding polypeptide. In embodiments wherein the hBCMA-binding polypeptide or hBCMA-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 hBCMA-binding polypeptide or hBCMA-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 hBCMA-binding polypeptide or hBCMA-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 moiety specific for a cancer cell surface target, for example a myeloma cell surface antigen, for example a myeloma cell surface antigen that is not hBCMA, or an additional binding moiety specific for an immune cell surface target, for example a NK cell surface protein, for example CD16a); 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 a myeloma cell surface antigen that is not 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 a myeloma cell surface antigen that is not BCMA; and the 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 an NK cell target, for example CD16a) 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 an NK cell target (for example CD16a); and second additional functional portion may comprise a cytokine, for example IL-15 or derivatives thereof. In another 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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a); 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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a). 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 a myeloma cell surface antigen that is not 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 a myeloma cell surface antigen that is not BCMA). In particular, a first additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not BCMA; and a second additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not 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 a myeloma cell surface antigen that is not 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, for example CD16a). In particular, a first additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not BCMA; and a second additional functional portion may comprise an additional binding moiety specific for a NK cell target (for example CD16a). Alternatively, 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 hBCMA-binding polypeptide or hBCMA-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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a), or comprises an immune signalling molecule, for example a cytokine, for example IL- 15 or derivatives thereof. When present, (for example in embodiments wherein the hBCMA-binding polypeptide or hBCMA-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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a), or comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. When present, (for example in embodiments wherein the hBCMA-binding polypeptide or hBCMA-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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a), or comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof. In one preferred embodiment, the hBCMA-binding polypeptide or hBCMA-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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a); 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 a myeloma cell surface antigen that is not BCMA, or is specific for an immune cell target, for example a NK cell target, for example CD16a). For example 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 a myeloma cell surface antigen that is not 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 a myeloma cell surface antigen that is not 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 a myeloma cell surface antigen that is not BCMA) or a immune cell target (for example a NK cell target, for example CD16a). In particular, a first additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not BCMA; and a second additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not 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 a myeloma cell surface antigen that is not BCMA). In another embodiment, a first additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not BCMA; and a second additional functional portion may comprise an additional binding moiety specific for a myeloma cell surface antigen that is not 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, for example CD16a). Alternatively, a first additional functional portion may comprise an additional binding moiety specific for a immune cell target (for example a NK cell target, for example CD16a); and a second additional functional portion may an additional binding moiety specific for immune cell target (for example a NK cell target, for example CD16a); 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 a myeloma cell surface antigen that is not BCMA) or a immune cell target (for example a NK cell target, for example CD16a). In particular, a first additional functional portion may comprise an additional binding moiety specific for a immune cell target (for example a NK cell target, for example CD16a); and a second additional functional portion may comprise an additional binding moiety specific for immune cell target (for example a NK cell target, for example CD16a); 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 immune cell target (for example a NK cell target, for example CD16a). In another embodiment, a first additional functional portion may comprise an additional binding moiety specific for immune cell target (for example a NK cell target, for example CD16a); and a second additional functional portion may comprise an additional binding moiety specific for immune cell target (for example a NK cell target, for example CD16a); and a third additional functional portion may comprise an additional binding moiety specific for myeloma cell surface antigen that is not BCMA. In embodiments of the invention, a hBCMA-binding polypeptide of the present invention or hBCMA-binding oligomer of the present invention comprising an additional functional portion has an additional functional portion separated from the hBCMA-binding polypeptide or the hBCMA-binding oligomer by a linker. The linker may be any linker described herein. In embodiments of the invention a hBCMA-binding polypeptide, or hBCMA-binding oligomer, comprising an additional functional portion of the present invention has an additional functional portion separated from the hBCMA-binding polypeptide or the hBCMA-binding oligomer by a linker. The linker may be any linker described herein. In certain embodiments, a hBCMA-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 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 hBCMA binding polypeptide. A schematic representation of hBCMA binding polypeptide according to this aspect of the invention and comprising one additional functional portion is provided in Figure 10b, wherein the linker comprises a triazole. Preferably a linker (for example the linker or each linker) is attached to the terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the 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 embodiments where the linker is attached to the [N-terminal portion] of a hBCMA 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 hBCMA 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 a linker (for example the linker or each linker)is attached to a non-terminal amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the 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 [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 hBCMA-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,

[0027] . 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 hBCMA-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]; 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 hBCMA binding polypeptide. Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the 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 is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the 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 [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 NH2 of 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 X4of 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 lysine at X50of 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 hBCMA-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]; Preferably the or at least one (for example one or both) additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably the or one additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, the or at least one (for example one or both) additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, 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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the indicated CD16a binding polypeptide. Preferably the linker, or a linker, is attached to the terminal amino acid of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of the indicated 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, or a linker, is attached to a non-terminal amino acid of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of the indicated 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 [CD16a N-terminal portion] in embodiments wherein the CD16a [N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [CD16a C-terminal portion] in embodiment wherein the [CD16a C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). In one preferred embodiment, the hBCMA-binding polypeptide comprises the following structure: [N-terminal portion]-[ Helix 1]- [Separating portion]-[ Helix 2]-[ C-terminal portion]-[linker]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[Helix 2]-[CD16a C-terminal portion]; [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a 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]-[CD16a C-terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a N-terminal portion]; [C-terminal portion]-[Helix 2]- [Separating portion]-[Helix 1]-[N-terminal portion]-[linker]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion]. For example, the hBCMA-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion]; [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion]-[linker]-[N-terminal portion]- [Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]; or [N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[CD16a C-terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a N-terminal portion]. Alternatively, for example, the hBCMA-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion]; [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-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]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion]. Most preferably the hBCMA-binding polypeptide comprises the following structure: [N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion]-[linker]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion]; or [C-terminal portion]-[Helix 2]- [Separating portion]-[Helix 1]-[N-terminal portion]-[linker]-[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a 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 hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N- terminal portion] of the CD16a 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 hBCMA binding polypeptide and attached to terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a 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 hBCMA 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 [CD16a C-terminal portion] or [CD16a 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 hBCMA 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 hBCMA binding polypeptide in embodiments wherein the [N-terminal portion] has the sequence X1X2X3X4X5, or attached to a non-terminal lysine at X50 of the [C-terminal portion] of the hBCMA 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 [CD16a C-terminal portion] or [CD16a N-terminal portion] (for example attached to a non-terminal lysine of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion], and especially attached to a non- terminal lysine at position X4of the [CD16a N-terminal portion] polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5or a non-terminal lysine at position X50of the [CD16a C-terminal portion] in embodiments wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). 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 hBCMA binding polypeptide (for example attached to a non-terminal lysine at X4of the [N-terminal portion] of the hBCMA 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 hBCMA 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 [CD16a C-terminal portion] or [CD16a N-terminal portion]. In another embodiment, the linker is attached to a non-terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide (for example attached to a non-terminal lysine at X4of the [CD16a N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5, or attached to a non-terminal lysine at X50of the [CD16a C-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a 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 [C-terminal portion] or [N-terminal portion] of the hBCMA binding polypeptide. In one preferred embodiment, the hBCMA binding polypeptide may optionally comprise a further hBCMA binding polypeptide such that the hBCMA binding polypeptide is a hBCMA binding oligomer. In another preferred embodiment the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the a hBCMA-binding polypeptide consists of a hBCMA-binding motif and / or a hBCMA-binding polypeptide). In one preferred embodiment, the hBCMA polypeptide comprises (or consists of) a compound selected from the group consisting of L1 to L16. In certain embodiments, a hBCMA-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 hBCMA binding polypeptide. 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); and the linker may optionally additionally comprises , or In such embodiment, preferably the linker 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, and especially 2, 3 or 4); and optionally a group. For example, the linker comprises (or consists of) a group selected from the following group: ,

[0028] , . Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of the 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 is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the 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 [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 hBCMA binding polypeptide may optionally comprise a further hBCMA binding polypeptide such that the hBCMA binding polypeptide is a hBCMA binding oligomer. In certain preferred embodiments the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the hBCMA-binding polypeptide consists of a hBCMA-binding motif and / or a hBCMA- binding polypeptide). In certain preferred embodiments the hBCMA binding polypeptide comprise one or two (especially one) further hBCMA polypeptide. In embodiments wherein the hBCMA-binding polypeptide comprises the following structure, preferably at least one (for example one or both) additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably one additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, at least one (for example one or both) additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the or each CD16a binding polypeptide). Therefore, in one preferred embodiment, the hBCMA-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 -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion] or -[CD16a C-terminal portion]- [CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a N-terminal portion]; and Y represents additional functional portion; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of each CD16a 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 hBCMA binding polypeptide and the attached to terminal amino acid of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a 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 hBCMA 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 the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide. In one very preferred embodiment, the linker is 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] or [N-terminal portion] of the hBCMA binding polypeptide and attached to terminal amino acid of the indicated [CD16a C-terminal portion] and / or [CD16a N-terminal portion] of each CD16a binding polypeptide. In such embodiments preferably the linker comprises (or consists of) a group selected from the following group:

[0029]

[0030] . In such embodiments, it is especially preferred that X represents -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C- terminal portion]. In certain embodiments, a hBCMA-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure:

[0031] ; ; 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 hBCMA binding polypeptide. In certain embodiments, 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 certain embodiments, 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 certain embodiments, 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 preferably each linker comprises (or consists of) a 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, the linker attached to the terminus of the terminal amino acid preferably comprises, or has, the following structure: 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] preferably 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 hBCMA binding polypeptide may optionally comprise a further hBCMA binding polypeptide such that the hBCMA binding polypeptide is a hBCMA binding oligomer. In certain preferred embodiments the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the hBCMA-binding polypeptide consists of a hBCMA-binding motif and / or a hBCMA- binding polypeptide). In certain preferred embodiments the hBCMA binding polypeptide comprise one or two (especially one) further hBCMA polypeptide. In certain embodiments, the hBCMA-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 hBCMA-binding polypeptide of the present invention comprising an additional functional portion comprises the following structure: or ; wherein preferably at least one (for example one or both) additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably one additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, at least one (for example one or both) additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments each linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the indicated CD16a binding polypeptide. More preferably, the or each linker is attached to the terminal amino acid of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of the indicated 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 a terminal lysine) of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of the indicated CD16a binding polypeptide. Therefore, in one preferred embodiment, the hBCMA-binding polypeptide comprises the following structure: ; wherein X represents -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion] or -[CD16a C- terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]- [CD16a N-terminal portion]; and Y represents additional functional portion; the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide. In certain embodiments, one linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the hBCMA binding polypeptide and attached to the terminal amino acid of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a 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 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 hBCMA binding polypeptide and attached to the terminal amino acid of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a 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 hBCMA binding polypeptide. In certain other embodiments, a hBCMA 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 hBCMA 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-traixole 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 . Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] and [N-terminal portion] of the 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 is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the 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 [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 hBCMA binding polypeptide in embodiment wherein the [C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58). One or more (for example one, two or three, and more preferably one) additional functional portions are each an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably one additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, one or more (for example one, two or three, and more preferably one) additional functional portion are each an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide). Therefore, in one preferred embodiment, the hBCMA-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 -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion] or -[CD16a C-terminal portion]- [CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a N-terminal portion]; and Y represents additional functional portion; and Z represents additional functional portion; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide. In certain preferred embodiments, a hBCMA-binding oligomer 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]; 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 X represents an additional functional portion; wherein 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; and and wherein the linker is attached to any amino acid of the indicated [C-terminal portion] or [N-terminal portion] of each hBCMA binding polypeptide. A schematic representation of hBCMA binding oligomer according to this aspect of the invention is provided in Figure 11b, 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); and the linker may optionally additionally comprises , or In such embodiment, preferably the linker 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, and especially 2, 3 or 4); and optionally a group. Preferably the linker comprises (or consists of) a group selected from the following group: ,

[0033] , . Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of each 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). Even more preferably the linker is 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] or [N-terminal portion] of each hBCMA binding polypeptide. In another embodiment the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of one 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 [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 attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the other 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 is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of each 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 [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 hBCMA binding oligomer may optionally comprise a further hBCMA binding polypeptide. In one preferred embodiment the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the hBCMA-binding oligomer consists of two hBCMA-binding polypeptides). In certain preferred embodiments, A represents -[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] and B -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or A represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion] and B represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]. In such embodiments preferably the linker is attached to the terminal amino acid of the indicated [N-terminal portion] or [C-terminal portion] of each 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 is attached to a non-terminal amino acid of the indicated [N-terminal portion] or [C-terminal portion] of each 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 [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)). Most preferably the linker is attached to the side chain of the terminal amino acid (for example attached to the side chain of a terminal lysine) acid of the indicated [N- terminal portion] or [C-terminal portion] of each hBCMA binding polypeptide. In embodiments wherein the hBCMA-binding oligomer comprises the following structure, preferably the additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably the additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, the additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide). Therefore, in one preferred embodiment, the hBCMA-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 X represents -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C- terminal portion] or -[CD16a C-terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a N-terminal portion]; and wherein 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; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a 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 each hBCMA binding polypeptide and the attached to terminal amino acid of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a 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 each hBCMA 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 the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide. In one very preferred embodiment, the linker is attached to the side chain of the terminal amino acid (for example side chain of a terminal lysine) of the indicated [C- terminal portion] or [N-terminal portion] of each hBCMA binding polypeptide and attached to the terminal amino acid of the indicated [CD16a C-terminal portion] and / or [CD16a N-terminal portion] of the CD16a binding polypeptide. In such embodiments preferably the linker comprises (or consists of) a group selected from the following group: ,

[0034] , . In such embodiments, it is especially preferred that X represents -[CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]-[CD16a C- terminal portion], i.e. that the hBCMA-binding oligomer comprises the following structure: In such embodiments the linker is attached to any amino acid of the indicated [CD16a N-terminal portion] of the CD16a binding polypeptide. In such embodiment, preferably A represents -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]- [C-terminal portion] and Y 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 Y represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]. In certain preferred embodiments, each N-terminal portion has the same sequence; each C-terminal portion has the same sequence; each separating portion has the same sequence; each Helix 1 portion may has the same sequence; and each Helix 2 portion has the same sequence. In one embodiment, the hBCMA binding oligomer may optionally comprise a further hBCMA binding polypeptide. In one preferred embodiment the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the a hBCMA-binding oligomer consists of two hBCMA-binding polypeptides). In one preferred embodiment, the hBCMA binding oligomer comprises (or consists of) a compound selected from the group consisting of L17 to L28 and L31 to L37.

[0035] In certain embodiments, a hBCMA-binding oligomer 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]; 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 X represents an additional functional portion; wherein 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; and wherein each linker 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 each hBCMA binding polypeptide. A schematic representation of hBCMA binding polypeptide according to this aspect of the invention is provided in Figure 12b, wherein each linker comprises a triazole. Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] or [N-terminal portion] of each 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). More preferably the linker is 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] or [N-terminal portion] of each hBCMA binding polypeptide. In another embodiment the linker is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of one 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 [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 attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the other 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 is attached to a non-terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of each 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 [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 embodiments wherein the linker is attached to the side chain of a terminal amino acid (for example attached to the side chain of a non-terminal lysine) of the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of one or each hBCMA binding polypeptide, preferably one or each linkers 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 embodiments wherein one or both linkers are attached to the side-chain of the terminal amino acid or attached to the side-chain of the non-terminal amino acid of the indicated [N-terminal portion] or the [C-terminal portion] of one or each hBCMA binding polypeptide, preferably one or each linkers comprises (or has) the following structure:

[0036] 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 hBCMA binding oligomer may optionally comprise a further hBCMA binding polypeptide. In one preferred embodiment the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the hBCMA-binding oligomer consists of two hBCMA-binding polypeptides). In certain preferred embodiments, A represents -[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] and B -[N-terminal portion]-[Helix 1]-[Separating portion]-[Helix 2]-[C-terminal portion]; or A represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion] and B represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]. In one preferred embodiments, A represents -[C-terminal portion]-[Helix 2]- [Separating portion]-[Helix 1]-[N-terminal portion] and B represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]. Preferably the linker is attached to the terminal amino acid of the indicated [C- terminal portion] of each 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) of the indicated [C-terminal portion] of each hBCMA binding polypeptide. More preferably the linker is 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] of each hBCMA binding polypeptide. In embodiments wherein the hBCMA-binding oligomer of the present invention comprising an additional functional portion comprises the following structure: preferably the additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably the additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, the additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments each linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide. More preferably, each linker is attached to the terminal amino acid of the [CD16a C- terminal portion] or [CD16a 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 a terminal lysine) of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the indicated CD16a binding polypeptide. In such embodiments, preferably one linker is attached to the terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide, and the other linker is attached to the side chain of a non- terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N- terminal portion]of the CD16a binding polypeptide (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 [CD16a C-terminal portion] or [CD16a N-terminal portion]of the CD16a binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion]of the CD16a binding polypeptide (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 [CD16a C-terminal portion] or [CD16a N-terminal portion]of the CD16a binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide(for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [CD16a N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5,or for example a lysine at X50of the [CD16a C-terminal portion] of the CD16a binding polypeptide in embodiment wherein the [CD16a C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [CD16a N- terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a 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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide, and the other linker is attached to the side chain of a non-terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [CD16a N-terminal portion] in embodiments wherein the [CD16a N-terminal portion] of the CD16a binding polypeptide has the sequence X1X2X3X4X5, or for example a lysine at X50of the [CCD16a -terminal portion] of the CD16a binding polypeptide in embodiment wherein the [CD16a C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [CD16a N- terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] of the CD16a binding polypeptide has the sequence X1X2X3X4X5. In another embodiment, both linkers are attached to the terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide, wherein one is attached to the terminus of the terminal amino acid of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide, and one attached to the side chain of the terminal amino acid of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide (for example attached to the side chain of a terminal lysine). In certain embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5, one linker is attached to the side-chain of a lysine at X4of the [CD16a N- terminal portion] of the CD16a binding polypeptideand the other linker is attached to the N-terminus or a side-chain of a lysine at X1of the [CD16a N-terminal portion] of the CD16a binding polypeptide. In certain embodiments wherein the [CD16a C- terminal portion] of the CD16a binding polypeptidehas the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, one linker is attached to the side-chain of a lysine at X50of the [CD16a C-terminal portion] of the CD16a binding polypeptideand the other linker is attached to the C-terminus or a side-chain of a lysine at X58of the [CD16a C-terminal portion] of the CD16a binding polypeptide. In such embodiments each linker is attached to any amino acid of the [CD16a N- terminal portion] of the CD16a binding polypeptide. Preferably, one linker is attached to the terminal amino acid of the indicated [CD16a 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) and the other linker is attached to a non-terminal amino acid of the indicated [CD16a 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 [CD16a N-terminal portion] of the CD16a binding polypeptidein embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5. In one preferred embodiment, the hBCMA-binding polypeptide comprises the following structure: ; and more preferably ; 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]; wherein 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; and wherein each linker may be the same or different; the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide. In such embodiments preferably each linker comprises (or consists of) a group selected from the following group: wherein y is 1 to 12 (for example wherein y is 1 to 12 (for , 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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [C- terminal portion] or [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 [CD16a C-terminal portion] or [CD16a 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 [C-terminal portion] or [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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [C-terminal portion] or [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 [CD16a C-terminal portion] or [CD16a 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 [C-terminal portion] or [N- terminal portion] of the bBCMA binding polypeptide. In one preferred embodiment, one linker is attached to the terminus of the terminal amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [C-terminal portion] or [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 [CD16a C-terminal portion] or [CD16a N-terminal portion] (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [CD16a N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50 of the [CD16a C-terminal portion] of the CD16a binding polypeptide in embodiment wherein the [CD16a C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [CD16a N-terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5, and attached to the terminal amino acid of the indicated [C-terminal portion] or [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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [C-terminal portion] or [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 [CD16a C-terminal portion] or [CD16a N-terminal portion] (for example attached to the side chain of a non-terminal lysine, for example a lysine at X4of the [CD16a N- terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5, or for example a lysine at X50of the [CD16a C-terminal portion] of the CD16a binding polypeptide in embodiment wherein the [CD16a C-terminal portion] has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58), and preferably a lysine at X4of the [CD16a N- terminal portion] of the CD16a binding polypeptide in embodiments wherein the [CD16a N-terminal portion] has the sequence X1X2X3X4X5, and attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the hBCMAbinding 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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [C-terminal portion] or [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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide and attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of the hBCMA binding polypeptide. In one embodiment, the hBCMA binding oligomer may optionally comprise a further hBCMA binding polypeptide. In one preferred embodiment the hBCMA binding polypeptide does not comprise a further hBCMA binding polypeptide (i.e. the hBCMA-binding polypeptide consists of two hBCMA-binding polypeptides). In one preferred embodiment, the hBCMA polypeptide comprises (or consists of) a compound selected from the group consisting of L29 and L30. In certain other preferred embodiments, a hBCMA-binding oligomer 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]; 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]; and X represents an additional functional portion; each linker is a linker as described herein and may be the same or different; and wherein each linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each hBCMA 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 hBCMA binding polypeptide). Preferably, at least one (more preferably each) linker comprises one or more group selected from the group consisting of triazole (especially 1,4-triazole, ,

[0037] . 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, preferably the additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably the additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, the additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide). Therefore, in one preferred embodiment, the hBCMA-binding oligomer comprises the following structure, , , , Ĭ or ; 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]; and X represents -[CD16a N- terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]- [CD16a C-terminal portion] or -[CD16a C-terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]-[CD16a N-terminal portion]; and wherein 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; and the linker is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of the hBCMA binding polypeptide and attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a binding polypeptide. Preferably the linker is attached to the terminal amino acid of the [CD16a C-terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide. In such embodiments preferably each linker is attached to the terminal amino acid of the indicated [C-terminal portion] or [N-terminal portion] of each hBCMA binding polypeptide and the attached to terminal amino acid of the indicated [CD16a C- terminal portion] or [CD16a N-terminal portion] of the CD16a 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 each hBCMA 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 the indicated [CD16a C-terminal portion] or [CD16a N-terminal portion] of the CD16a 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 each hBCMA 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 the indicated [CD16a C-terminal portion] and / or [CD16a N-terminal portion] of the CD16a binding polypeptide. In certain other preferred embodiments, a hBCMA-binding oligomer of the present invention comprising an additional functional portion comprises the following structure: , ,

[0038] , 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” and “linker 2” are linkers as described here, and each “linker”, “linker 1”, and / or “linker 2” may be the same or different, wherein each linker (for example, “linker”, “linker 1”, and / or “linker 2”) is attached to any amino acid of the indicated [C-terminal portion] and / or [N-terminal portion] of each hBCMA 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 hBCMA 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) 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 hBCMA-binding oligomer comprising an additional functional portion comprises the following structure: Ĩfor 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]); , 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 hBCMA 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 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)) 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, at least one (for example one or both, preferably one) additional functional portion of a hBCMA-binding oligomer comprising an additional functional portion of the present invention is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably each additional functional portion is an additional binding moiety specific for CD16a. Even more preferably, at least one (for example one or both, preferably one) additional functional portion is an additional binding moiety specific for CD16a that is a CD16a binding polypeptide and which comprises at least one motif that binds to CD16a, wherein said polypeptide comprises the following structure: [CD16a N-terminal portion]-[CD16a Helix 1]-[CD16a Separating portion]- [CD16a Helix 2]-[CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[CD16a Separating portion]-[CD16a Helix 2]. Even more preferably, such a CD16a binding polypeptide is a CD16a binding polypeptide as defined in International Application No. PCT / EP2023 / 064624, the contents of which are incorporated herein by reference. In such embodiments the linker is attached to any amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide (and preferably the linker is attached to the terminal amino acid of the [CD16a C- terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide). In such embodiments, X represents -[CD16a N-terminal portion]-[CD16a Helix 1]- [CD16a Separating portion]-[CD16a Helix 2]-[CD16a C-terminal portion] or -[CD16a C- terminal portion]-[CD16a Helix 2]-[CD16a Separating portion]-[CD16a Helix 1]- [CD16a N-terminal portion]; and Y represents additional functional portion; and the linker or a linker (for example “linker”, “linker 1”, “linker 2” or “linker 3”) is attached to any amino acid of the indicated [CD16a C-terminal portion] or [CD16a N- terminal portion] of each CD16a 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 [CD16a C-terminal portion] or [CD16a N-terminal portion] of each CD16a binding polypeptide. In certain embodiments, a hBCMA-binding oligomer of the present invention comprising an additional functional portion comprises at least three hBCMA-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 hBCMA 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 hBCMA binding polypeptide). In such embodiments, more preferably the hBCMA-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 such embodiments, more preferably each additional functional portion is an additional binding moiety specific for a NK cell target, for example CD16a. Most preferably each additional functional portion is an additional binding moiety specific for CD16a, 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 a myeloma cell surface antigen that is not BCMA, or an immune cell target, for example a NK cell target, for example CD16a); 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 a myeloma cell surface antigen that is not BCMA); an additional binding moiety specific for an immune cell target (for example a NK cell target, for example CD16a); 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 myeloma cell surface antigen that is not BCMA; an additional binding moiety specific for a NK cell target, for example CD16a; 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 myeloma cell surface antigen that is not BCMA; and an additional binding moiety specific for a NK cell target, for example CD16a; and 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 myeloma cell surface antigen that is not BCMA; and an additional binding moiety specific for a NK cell target, for example CD16a; 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 a myeloma cell surface antigen that is not BCMA; and an additional binding moiety specific for CD16a; 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 CD16a; and 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 a myeloma cell surface antigen that is not BCMA; and an additional bind...

Claims

Claims 1. An hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; and which further comprises at least one additional functional portion, wherein the hBCMA-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. An hBCMA-binding oligomer, which comprises at least two hBCMA-binding polypeptides, wherein each hBCMA-binding polypeptide comprises at least onemotif that binds to hBCMA, and wherein each 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]; and wherein the hBCMA-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 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 1and wherein the hBCMA-binding oligomer optionally further comprises at least one additional functional portion, wherein the hBCMA-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 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 13. The hBCMA-binding polypeptide as claimed in claim 1, or the hBCMA-binding oligomer as claimed in claim 2, wherein the or each 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], and wherein i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, 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;X25is F or Y; X31is I, M, or V; X33is K or S; X35is 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.

4. The hBCMA-binding polypeptide or the HBCMA-binding oligomer as claimed in claim 3, wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO:

2.

5. The hBCMA-binding polypeptide as claimed in claim 1, or the hBCMA-binding oligomer as claimed in claim 2, wherein the or each hBCMA-binding polypeptide comprises the following structure: i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FX25QKWAFX31RX33LX35[SEQ ID NO.279], wherein, independently from each other, X9 and X10 are 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; X25is F or Y; X31is I, M, or V; X33is K or S; X35is 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; and wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO:

2.

6. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 3, wherein: i) Helix 1 comprises the sequence X9X10X11ADX14EIX17X18[SEQ ID NO.278] and Helix 2 comprises the sequence FYQKWAFIRX33LM, wherein, independently from each other, X9is D, E, H, K, N, Q, S, or V; X10is A, E, F, I, K, M, N, Q, R, S, T, Y, or V; X11is E, F, or H; X14is A, E, H, I, K, L, Q, R, T, or Y; X17is A, E S, T, or V; X18 is A, F, H, K, L, M, N, T, or S; X33is K or S; 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 3 (for example 1, 2 or 3) of the Xnresidues are replaced by an alternative residue, and / or at least 1 and no more than 3 (for example 1, 2 or 3) of the residues not labelled as Xnare replaced by an alternative residue (for example replaced by an alternative residue that is a conservative replacement).

7. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 6, wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO: 2.

8. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 7 claim, wherein: Helix 1 comprises the sequence X6X7X8X9X10X11ADX14EIX17X18X19[SEQ ID NO. 278] and / or Helix 2 comprises the sequence X23FX25QKWAFX31RX33LX35X36X37, wherein, X6is any naturally occurring amino acid (preferably D, E, N or Q; more preferably N) or is absent; X7is 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; or wherein X9and X10are any naturally occurring amino acid excluding methionine (preferably X9is N X10is Q); X11 is E, F, H, Q, T or Y (preferably F); X14is any naturally occurring amino acid excluding methionine (preferably E);X17is A, E, Q, S, T or V (preferably A); X18is any naturally occurring amino acid excluding methionine (preferably A); X25is F or Y (preferably Y); X31is I or V (preferably I); X33is K or S (preferably K); X35is a naturally occurring amino acid (for example a naturally occurring amino acid excluding methionine, and more preferably, a naturally occurring amino acid that is isosteric with methionine, for example isoleucine) or an unnatural amino acid (for example a naturally occurring amino acid that is isosteric with methionine, for example norleucine, or homoleucine or tert- Butyl alanine) (for example, X9is N; X10is Q; X11is F; X14is E; X17is A; X18A; X25is Y; X31is I; X33is K; and X35is a naturally occurring amino acid (for example a naturally occurring amino acid excluding methionine, and more preferably, a naturally occurring amino acid that is isosteric with methionine, for example isoleucine) or an unnatural amino acid (for example a naturally occurring amino acid that is isosteric with methionine, for example norleucine, or homoleucine or tert- Butyl alanine)); or wherein X9 is N; X10 is Q; X11 is F; X14 is E; X17 is A; X18 A; X25 is Y; X31 is I; X33 is K; and X35is I, L, M, V, Q, norleucine, homoleucine, or tert-Butyl alanine (for example I, L, V, Q, norleucine, homoleucine, tert-Butyl alanine); or wherein X9is N; X10is Q; X11is F; X14is E; X17is A; X18A; X25is Y; X31is I; X33is K; and X35is norleucine, homoleucine, or tert-Butyl alanine.

9. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 8, wherein: i) Helix 1 comprises the sequence NKEETFADLEISNL and Helix 2 comprises the sequence NFYQKWAFIRSLMDD, 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 2 (for example 1 or 2) residues are replaced by an alternative residue, or (iii) 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).

10. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 9, wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO:

1.

11. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 8, wherein: i) Helix 1 comprises the sequence NKENQFADEEIAAL and Helix 2 comprises the sequence NFYQKWAFIRKLMDD, 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 2 (for example 1 or 2) residues are replaced by an alternative residue or (iii) 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).

12. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 11, wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO: 2.

13. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 12 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.

14. The hBCMA-binding polypeptide or the hBCMA-binding as claimed in any one of claims 3 to 13 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); 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, X21or X22are absent; and preferably wherein X20is P; X21is N; and X22is L (for example, the separating portion has the sequence PNL).

15. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 14, 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.

16. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 15 wherein the N-terminal portion has the sequence XaXbX1X2X3X4X5, wherein:Xais M or is absent; Xbis M or is absent; X1is any naturally occurring amino acid (preferably G, A, V, L or I; more preferably V or G; 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; preferably wherein Xais M or is absent, Xbis M or is absent, X1is V, G or absent (preferably V or absent), X2is D or absent, X3is N or absent, X4is K or absent, and X5is F or absent.

17. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 16, wherein the N-terminal portion is absent, or the N- terminal portion has the sequence XaXbX1X2X3X4X5 wherein: Xa is M, Xb is M, X1 is V or G (preferably V), X2 is D, X3 is N, X4 is K, and X5 is F; or Xa is absent, Xb is absent, X1 is V or G (preferably V), X2 is D, X3 is N, X4 is K, and X5is F; or Xais absent, Xbis absent, X1is absent, X2is D, X3is N, X4is K, and X5is F; or Xais absent, Xbis absent, X1is absent, X2is absent, X3is N, X4is K, and X5is F; or Xais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is K, and X5is F; orXais absent, Xbis absent, X1is absent, X2is absent, X3is absent, X4is absent, and X5is F.

18. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 17, 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 G, F, Y or W (for example F, Y or W, or, for example G); more preferably F) or is absent; and preferably wherein X1is V, G or absent, X2is D or absent, X3is N or absent, X4is K or absent, and X5is F or absent.

19. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 18, 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; or X1is absent, X2is absent, X3is N, X4is K, and X5is F; or 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 G 20. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 19, 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.

21. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 20, wherein the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, 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), X56 is any naturally occurring amino acid (preferably G, A, K, V, L or I (for example 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, 3, 4 or 5) (preferably at least 1 and no more than 3 (for example 1, 2, or 3)) of theresidues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue; and preferably optionally wherein, at least 1 and no more than 5 (for example 1, 2, 3, 4 or 5) (preferably at least 1 and no more than 3 (for example 1, 2, or 3)) of the residues in the sequence QSANLLAEAKKLNDAQ are replaced by an alternative residue that is a conservative replacement.

22. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in claim 21, wherein the C-terminal portion has the sequence X38X39QSANLLAEAKKLNDAQX56X57X58, wherein X56is A, X57is P, and X58is K; X56is A; or X57is P, and X58is absent; X56is A, X57is absent; and X58is absent; X56is absent, X57is absent, and X58is absent; or Or X56is K, 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 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 are replaced by an alternative residue that is a conservative replacement; and preferably wherein X38 is P and X39 is S.

23. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 22, wherein: (i) the separating portion has the sequence X20X21X22; and / orthe N-terminal portion has the sequence XaXbX1X2X3X4X5 ;and / or the C-terminal portion has the sequence PSQSANLLAEAKKLNDAQX56X57X58; wherein, in said separating portion, X20is P; X21is N; X22is L; wherein in said N-terminal portion, Xais M or absent; Xbis M or absent; X1is V or G (preferably V), or absent; X2is D or G, or absent; X3is G or 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.

24. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 23, wherein said separating portion has the sequence PNL.

25. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 24, wherein: (i) said separating portion has the sequence PNL and said hBCMA binding motif is flanked by an N-terminal portion X1X2X3X4X5[SEQ ID NO. X] and a C- terminal portion PSQSANLLAEAKKLNDAQAPK [SEQ ID NO. X], wherein in said N-terminal portion,X1is G, V, or deleted; X2is D or deleted; X3is N or deleted; X4is K or deleted; X5is F or deleted; or (ii) the separating portion, N-terminal portion, and C-terminal portion are as defined in (i), wherein within those portions taken together at least 1 and no more than 5 residues are replaced by an alternative residue.

26. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 25, wherein said N-terminal portion has the sequence VDNKF [SEQ ID NO. X].

27. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any of claims 13-26 wherein the hBCMA binding efficacy is at least 1% of SEQ ID NO:

2.

28. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 27, wherein the hBCMA binding motif sequence is selected from SEQ ID NOs.170 to 275 and 1036 and 1042 (for example 170 to 275); preferably from SEQ ID NOs.170-188 and 1036 and 1042 (for example 170-188); 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.

29. The hBCMA-binding polypeptide as claimed in claim 1 or claim 3 or the hBCMA-binding oligomer as claimed in claim 2 or claim 3, which comprises a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, 121-128 and 1027 to 1035 (for example 1, 2, 23-39, 41-119, 121-128) 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 hBCMA-binding polypeptide as claimed in claim 1 or claim 3 or the hBCMA- binding oligomer as claimed in claim 2 or claim 3, which comprises a sequence selected from SEQ ID NOs.2 and 23-39 and 1027 to 1035 (for example 23-39), 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.

30. The hBCMA-binding polypeptide as claimed in claim 1 or claim 3 or the hBCMA-binding oligomer as claimed in claim 2 or claim 3, wherein the sequence of the hBCMA-binding polypeptide is selected from: VDNKFNKEETFADLEISNLPNLNFYQKWAFIRSLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 1]; or VDNKFNKENQFADEEIAALPNLNFYQKWAFIRKLMDDPSQSANLLAEAKKLNDAQAP K [SEQ ID NO: 2]; or VDNKFNKEEIFADREIAFLPNLNFYQKWAFIRKLMDDPSQSANLLAEAKKLNDAQAPK [SEQ ID NO: 23]; or VDNKFNKEHQFADYEIAMLPNLNFYQKWAFIRSLMDDPSQSANLLAEAKKLNDAQAP K [SEQ ID NO: 33].

31. The hBCMA-binding polypeptide as claimed in claim 1 or claim 3 or the hBCMA-binding oligomer as claimed in claim 2 or claim 3 wherein the sequence of the hBCMA-binding polypeptide is selected from SEQ ID NOs.23-39 and 1027 to 1035 (for example 23-39).

32. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 31, wherein the or each hBCMA-binding polypeptide does not comprise methionine.

33. The hBCMA-binding polypeptide or the hBCMA-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.

34. The hBCMA-binding polypeptide or the hBCMA-binding oligomer as claimed in any one of claims 3 to 33, wherein one or more residues (for example 1 to 5 residues, for example 1, 2 ,3, 4 or 5) of the or each hBCMA-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)).

35. An hBCMA-binding oligomer as claimed in any one of claims 2 to 34, which comprises 2, 3, 4, or 5 hBCMA-binding polypeptides as defined in any one of claims 3 to 34.

36. The hBCMA-binding oligomer as claimed any one of claims 2 to 35, which comprises at least two hBCMA-binding polypeptides, wherein a first hBCMA-binding polypeptide is as defined in any of claims 3 to 34, and a second hBCMA-binding polypeptide is as defined in any of claims 3 to 34.

37. The hBCMA-binding oligomer as claimed in claim 36 which comprises at least two hBCMA-binding polypeptides, wherein the first and second hBCMA-binding polypeptide have the same sequence.

38. The hBCMA-binding oligomer as claimed in claim 36, which comprises at least two hBCMA-binding polypeptides, wherein the first and second hBCMA-binding polypeptide have a different sequence.

39. The hBCMA-binding oligomer according to claim 36, which comprises at least two hBCMA-binding polypeptides, wherein: a first hBCMA-binding polypeptide comprises a first hBCMA-binding motif selected from SEQ ID Nos.170 to 275 and 1036 and 1042, or comprises a sequence selected from SEQ ID NOs.11, 2, 23-39, 41-119, 121-128 and 1027 to 1035; and a second hBCMA-binding polypeptide comprises a second hBCMA-binding motif selected from SEQ ID NOs.170 to 275 and 1036 and 1042 , or comprises a sequence selected from SEQ ID NOs.1, 2, 23-39, 41-119, 121-128 and 1027 to 1035.

40. The hBCMA-binding oligomer according to claim 39, which comprises at least two hBCMA-binding polypeptides, wherein the first and second hBCMA-binding polypeptides have the same sequence, or the first and second hBCMA-binding motifs selected have the same sequence; or wherein the first and second binding motif selected or first and second hBCMA-binding polypeptide have a different sequence.

41. The hBCMA-binding polypeptide as claimed in any of claims 1 or 3 to 34, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 40, wherein the or each linker comprises one or more groups selected from the group consisting of, wherein m is 1 to 16,42. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 41, wherein at least one linker (for example the, one or each linker) comprises one or more groups selected from the group consisting of, , ,43. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 42, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 42, wherein at least one linker (for example the, one or each linker) additionally comprises agroup selected from the group consisting,44. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 43 or the hBCMA-binding oligomer as claimed in any one of claims 2 to 43, 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 of45. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 44 or the hBCMA-binding oligomer as claimed in any one of claims 2 to 44, 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 group consistingespecially 2, 3, 4 or 8).

46. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 45 or the hBCMA-binding oligomer as claimed in any one of claims 2 to 45, 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, 3or 4) and / or one or more (for example one).

47. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 46 or the hBCMA-binding oligomer as claimed in any one of claims 2 to 46, 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:

48. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 46 or the hBCMA-binding oligomer as claimed in any one of claims 2 to 46 comprising at least 2 (for example 2) additional functional portions, wherein at least one (for example the or one) linker comprises (or is) a group selected from the group consisting of:.

49. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 48 or the hBCMA-binding oligomer as claimed in any one of claims 2 to 48, 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)).

50. The hBCMA-binding polypeptide or hBCMA-binding polypeptide oligomer as claimed in claim 49, 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.

51. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 50, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 50, which further comprises 1, 2, 3, 4 or 5 additional functional portions, or at least two or at least three additional functional portions.

52. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 51, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 51, wherein the additional functional portion comprises an immune signalling molecule, for example a cytokine, for example IL-15 or derivatives thereof.

53. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 51, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 51, wherein the additional functional portion comprises an additional binding moiety.

54. The hBCMA-binding polypeptide or hBCMA-binding oligomer as claimed in claim 53, wherein the additional binding moiety is specific for a cancer cell surface target, for example a myeloma cell surface antigen, or is specific for a NK cell target, for example CD16a.

55. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 51, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 51, wherein the hBCMA-binding polypeptide or hBCMA-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.

56. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 51, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 51, wherein the hBCMA-binding polypeptide or hBCMA-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, or is specific for a NK cell target, for example CD16a); 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, or is specific for a NK cell target, for example CD16a); 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, or is specific for a NK cell target, for example CD16a).

57. The hBCMA-binding polypeptide or hBCMA-binding oligomer as claimed in claim 56 comprising an additional functional portion, wherein the hBCMA- binding polypeptide or hBCMA-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, or is specific for a NK cell target, for example CD16a), 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, or is specific for a NK cell target, for example CD16a).

58. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 57, wherein the hBCMA-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 41 to 50 (for example claim 47); 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 hBCMA binding polypeptide.

59. The hBCMA-binding oligomer as claimed in any of claims 2 to 57, wherein the hBCMA-binding oligomer 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]; 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 X represents an additional functional portion; wherein 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; and wherein, the linker is a linker as defined in any one of claims 41 to 50 (for example claim 48); and wherein the linker is attached to any amino acid of the indicated [C- terminal portion] or [N-terminal portion] of each hBCMA-binding polypeptide (for example, wherein the A represents -[N-terminal portion]-[Helix 1]- [Separating portion]-[Helix 2]-[C-terminal portion] and Y 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 Y represents -[C-terminal portion]-[Helix 2]-[Separating portion]-[Helix 1]-[N-terminal portion]).

60. The hBCMA-binding oligomer as claimed in any of claims 2 to 57, wherein the hBCMA-binding oligomer comprises (or has) the following structure:and 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 X represents an additional functional portion; 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; and wherein each linker is a linker as defined in any one of claims 41 to 50 (for example claim 47), and each linker 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 hBCMA-binding polypeptide.

61. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or the hBCMA-binding oligomer as claimed in any one of claims 2 to 57, 59 or 60, wherein an additional functional portion (for example, the, one, at least one, or each additional functional portion) comprises an additional binding moiety specific for CD16a which is a CD16a-binding polypeptidewhich comprises at least one motif that binds to CD16a, wherein said CD16a- binding polypeptide comprises the following structure: [CD16a N-terminal portion]-[ CD16a Helix 1]-[ CD16a Separating portion]-[ CD16a Helix 2]-[ CD16a C-terminal portion] the CD16a binding motif being the portion [CD16a Helix 1]-[ CD16a Separating portion]-[ CD16a Helix 2]; and preferably wherein the CD16a - binding polypeptide is a polypeptide comprising (or having) a sequence selected from the group consisting of SEQ ID No.1001 to 1013 and 1043 of Figure 17 and CD16a SEQ ID No.1 to 75 of Figure 18, 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); or the CD16a -binding polypeptide is a polypeptide comprising a sequence selected from the group consisting of SEQ ID No.1014 to 1026 and 1044 of Figure 19 and CD16a SEQ ID No.150 to 221 of Figure 20, 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).

62. An hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; wherein the hBCMA-binding motif sequence is selected from SEQ ID No.1036 to 1042 of Figure 16.

63. An hBCMA-binding polypeptide which comprises at least one motif that binds to hBCMA, and 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]; wherein the sequence of the hBCMA-binding polypeptide is selected from SEQ ID NOs 1027 to 1035 of Figure 15.

64. An hBCMA binder-drug conjugate comprising the hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, and an additional therapeutic agent.

65. The hBCMA binder-drug conjugate as claimed in claim 64, wherein the additional therapeutic agent is a cytotoxic drug, for example MMAF, MMAE, doxorubicin, pyrrolobenzodiazepine, amanitin, maytansinoids, duostatins, mitomycin C, desmethyltopotecan or SN-38.

66. The hBCMA binder-drug conjugate as claimed in claim 64 or claim 65, wherein the hBCMA-binding polypeptide is connected to the additional therapeutic agent via a linker.

67. A pharmaceutical composition comprising the hBCMA -binding polypeptide as defined in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA- binding oligomer as claimed in any of claims 2 to 57 or 59 to 61.

68. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, the hBCMA binder-drug conjugate as claimed in any ofclaims 64 to 66, and / or the pharmaceutical composition as claimed in claim 67, for use in medicine.

69. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, the hBCMA binder-drug conjugate as claimed in any of claims 64 to 66, and / or the pharmaceutical composition as claimed in claim 67, for use in the treatment of cancer.

70. The hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, the hBCMA binder-drug conjugate as claimed in any of claims 64 to 66, and / or the pharmaceutical composition as claimed in claim 67, for use as claimed in claim 69, wherein the cancer is multiple myeloma.

71. Use of the hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, the hBCMA binder-drug conjugate as claimed in any of claims 64 to 66, and / or the pharmaceutical composition as claimed in claim 67, for the manufacture of a medicament for the treatment of cancer.

72. A method of treating cancer, the method comprising administering to a patient in need thereof the hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, the hBCMA binder-drug conjugate as claimed in any of claims 64 to 66, and / or the pharmaceutical composition as claimed in claim 67.

73. A kit comprising the hBCMA-binding polypeptide as claimed in any of claims 1, 3 to 34 or 41 to 58, or 61 to 63, or the hBCMA-binding oligomer as claimed in any of claims 2 to 57 or 59 to 61, the hBCMA binder-drug conjugate as claimed in any of claims 64 to 66, or the pharmaceutical composition as claimed in claim 67 and, optionally, one or more further therapeutic agent(s).

74. The kit as claimed in claim 73, 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.

75. The kit as claimed in claim 73 or claim 74, for use in the treatment of cancer, for example multiple myeloma.