Biopharmaceutical prodrug platform based on protein structural changes

Abstract

The present invention relates to proteinaceous prodrug constructs, such as proteinaceous fusion constructs comprising complement 3 and pregnancy associated protein-like, alpha-2-macroglobulin domain-containing (CPAMD) proteins (e.g., A2M) and one or more drugs, which function as protease-activatable prodrugs.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to European Patent Application Publication No. 22154258.2, filed January 31, 2022, the contents of which are incorporated herein in their entirety.

[0002] The present invention relates to proteinaceous prodrug constructs, such as proteinaceous fusion constructs comprising complement 3 and pregnancy associated protein-like, alpha-2-macroglobulin domain-containing (CPAMD) proteins (e.g., A2M) and one or more drugs, which function as protease-activatable prodrugs. [Background technology]

[0003] When biopharmaceuticals are administered to patients in their initially active form, they may exert their biological effects in both diseased and healthy tissues. Drug effects in healthy tissues may be detrimental to the patient's health, quality of life, and / or therapeutic efficacy. One strategy to minimize these side effects is to derivatize drugs into prodrug forms that are initially inactive and only become active in the disease environment.

[0004] Proteases are enzymes that catalyze the hydrolysis of peptide bonds in other proteins. Over 600 human proteases are known, the majority of which are tightly regulated under normal circumstances. However, in many diseases, certain proteases are dysregulated and have increased activity compared to the healthy state. Many protease-activated prodrug technologies for biopharmaceuticals have been developed, the majority of which are based on antibodies. Some technologies use a masking moiety that blocks the antigen-binding region (paratope) of the antibody, preventing it from binding to its cognate epitope on the target antigen, thus rendering the antibody inactive. The masking moiety is attached to the antibody by a linker that incorporates a protease-cleavable site. Cleavage of the linker by the protease separates the antibody from the masking moiety, liberating the paratope and restoring the activity of the antibody. The masking moiety may be designed to specifically bind to the antibody paratope (e.g., using phage display derived peptides as in CytomX's Probody technology) or may sterically surround the paratope sufficiently to isolate it without specific interaction (e.g., using long, bulky peptides as in Amunix's XPAT technology). Another approach incorporates inactive VH and VL domains attached to the antibody by a protease-sensitive linker, thereby preventing functional VH / VL domains from pairing in the prodrug (e.g., Maverick's COBRA technology). Cleavage of the linker removes the inactive domains, allowing correct VH / VL pairing in the activated prodrug.

[0005] These various prodrug technologies all have advantages and disadvantages. For example, CytomX's Probody minimizes the use of non-human and potentially immunogenic sequences, but is not modular and requires the identification of affine masking moieties for every antibody incorporated into the platform. Amunix's XPAT platform does not require specific mask / antibody interactions and also has differential circulation half-lives before and after activation of the prodrug, which is achieved by using long non-human peptides. Thus, new prodrug technologies that combine the key advantages of multiple technologies are needed and would be a meaningful advance in the field. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is directed to the provision of proteinaceous prodrug constructs (eg, proteinaceous fusion constructs) that address one or more of the above-mentioned problems associated with existing proteinaceous prodrug platforms. [Means for solving the problem]

[0007] In particular, the proteinaceous prodrug constructs (e.g., proteinaceous fusion constructs) described herein allow for specific drug delivery and controllable activity. This is achieved by the proteinaceous prodrug constructs undergoing conformational changes that allow them to control the activity of the drug or drugs contained therein. In the native (uncleaved) state of the proteinaceous prodrug construct, the drug or drugs are not exposed and are therefore inactive. In the active (cleaved) state of the proteinaceous prodrug construct, the drug is exposed and can interact with its target.

[0008] The structural change is triggered by cleavage of a protease cleavage site contained in the proteinaceous prodrug construct of the present invention. The cleavage site contained within the proteinaceous prodrug construct can be modified to control where the drug is exposed. Depending on the cleavage site, the drug is only exposed where a protease that recognizes that cleavage site is present. When a particular protease is present and cleaves the cleavage site, the structure of the proteinaceous prodrug construct changes from "native" to "active". Thus, the present invention provides proteinaceous prodrug constructs (e.g., proteinaceous fusion constructs) whose activity and specificity can be controlled and targeted to specific regions (e.g., specific tissues) of a subject requiring treatment with such constructs.

[0009] Specifically, the present invention relates to a proteinaceous prodrug construct comprising (a) a complement 3 and pregnancy associated protein-like, alpha-2-macroglobulin domain-containing (CPAMD) protein or fragment thereof, and (b) one or more drugs, wherein (i) the CPAMD protein or fragment thereof comprises (1) a bite region having at least one protease cleavage site, and (2) a receptor binding domain (RBD), (ii) the one or more drugs are located within or in proximity to the RBD, and (iii) the CPAMD protein or fragment thereof is capable of shielding the one or more drugs and altering structure upon proteolytic cleavage of the at least one protease cleavage site to render the one or more drugs accessible.

[0010] In some embodiments, the one or more drugs are located within or near any one of loops 1-4 of the RBD. In some embodiments, the proteinaceous prodrug construct is a fusion protein. In some embodiments, the one or more drugs are located within any one of loops 1-4 of the RBD. In some embodiments, the loop is loop 1. In some embodiments, the loop is loop 2. In some embodiments, the loop is loop 3. In some embodiments, the loop is loop 4. In some embodiments, the loop is modified relative to the wild-type loop sequence by addition, substitution or deletion of one or more amino acids to accommodate the one or more drugs. In some embodiments, the one or more drugs replace one or more amino acids of the loop.

[0011] In some embodiments, the one or more drugs are located near any one of loops 1-4 of the RBD. In some embodiments, the loop is loop 1. In some embodiments, the loop is loop 2. In some embodiments, the loop is loop 3. In some embodiments, the loop is loop 4. In some embodiments, the proteinaceous prodrug construct comprises a first interaction domain and the one or more drugs comprise a second interaction domain, and the first and second interaction domains form a complex that positions the one or more drugs near the loop. In some embodiments, the first interaction domain and the second interaction domain form a coiled-coil structure. In some embodiments, the first interaction domain is a tag or epitope sequence in the loop and the second interaction domain is a functional fragment of a receptor or antibody that can specifically bind to the tag or epitope sequence.

[0012] In some embodiments, the proteinaceous prodrug construct can form a multimer (e.g., a dimer or a tetramer). In some embodiments, the multimerization occurs through the LNK region of the CPAMD protein. In some embodiments, the multimer is a tetramer formed by two disulfide-bridged dimers.

[0013] In some embodiments, the CPAMD protein is a human CPAMD protein, or a functional variant, fragment, or homolog thereof, such as a mammalian CPAMD protein. In some embodiments, the CPAMD protein, or a functional variant, fragment, or homolog thereof, has an amino acid sequence that is at least about 70%, at least about 80%, or at least about 90% identical to any one of the full-length CPAMD protein sequences shown in Table 1.

[0014] In some embodiments, the CPAMD protein, or a functional variant, fragment, or homolog thereof, has an amino acid sequence that is at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of the full-length CPAMD protein sequences shown in Table 1.

[0015] In some embodiments, the CPAMD protein is selected from A2M, PZP, ovostatin 1, ovostatin 2, CPAMD1, CPAMD2, CPAMD3, CPAMD4, CPAMD7, CPAMD8, CPAMD9, and functional homologs thereof. In certain embodiments, the CPAMD protein is selected from A2M, PZP, ovostatin 1, and ovostatin 2, and functional homologs thereof.

[0016] In some embodiments, the CPAMD protein is human A2M, or a functional homolog thereof, such as a mammalian A2M. In some embodiments, a functional homolog of human A2M has an amino acid sequence that is at least about 70%, at least about 80%, or at least about 90% identical to the amino acid sequence set forth in SEQ ID NO:1.

[0017] In some embodiments, human A2M has an amino acid sequence that is at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identical to, or identical to, the amino acid sequence set forth in SEQ ID NO:1.

[0018] In some embodiments, the one or more drugs are located within a region including amino acids 1368-1379, 1392-1404, 1420-1426, or 1450-1457 of human A2M. In some embodiments, the one or more drugs are located between amino acids 1402 and 1403 of human A2M. In some embodiments, the one or more drugs replace amino acids 1392-1403, 1393-1395, or 1393-1402 of human A2M.

[0019] In some embodiments, the one or more drugs are selected from the group consisting of antigen targeting moieties (e.g., single chain or domain antibodies), receptor ligands (e.g., cytokines), extracellular regions of cell surface receptors, extracellular regions of cell surface ligands, and receptor agonists.

[0020] In some embodiments, the bait region is modified to be selectively cleaved by one or more proteases. In some embodiments, the one or more proteases are selected from one or more serine-, cysteine-, aspartic acid- and / or metalloproteinases. In some embodiments, the bait region is modified to not contain protease cleavage sites recognized by human proteases, except for a single cleavage site.

[0021] In some embodiments, the modified bait region comprises an engineered amino acid sequence that is flexible and / or hydrophilic. In some embodiments, the engineered amino acid sequence comprises a sequence of glycine, serine, alanine, threonine, and / or proline residues. In some embodiments, the engineered amino acid sequence comprises a combination of glycine, serine, and / or alanine residues. In some embodiments, the engineered amino acid sequence replaces all or part of the wild-type bait region. In some embodiments, the engineered amino acid sequence replaces all of the wild-type bait region and has a length equal to the wild-type bait region.

[0022] In some embodiments, the one or more drugs are antibodies, or antigen-binding fragments thereof, that specifically bind to the antigen as an antagonist. In some embodiments, the one or more drugs are antibodies, or antigen-binding fragments thereof, that specifically bind to the antigen as an agonist.

[0023] In some embodiments, the one or more drugs is an antibody, or an antigen-binding fragment thereof, that specifically binds to an antigen selected from the group consisting of IL-2, EGFR, PDL-1, PD-1, CTLA-4, CD3γε, 4-1BB, IL-2Rα, and TNFα.

[0024] In some embodiments, the one or more drugs are selected from the group consisting of BTLA, OX40, LAG3, NRP1, VEGF, HER2, CEA, CD19, CD20, amyloid beta, HER3, IGF-1R, MUC1, EpCAM, CD22, VEGFR-2, PSMA, GM-CSF, CXCR4, CD30, CD70, FGFR2, BCMA, CD44, ICAM-1, Notch1, MHC, CD28, IL-1R1, TCR, Notch3, FG The antibody or antigen-binding fragment thereof specifically binds to an antigen selected from the group consisting of FR3, TGF-β, TGFBR1, TGFBR2, CD109, GITR, CD47, alpha-synuclein, CD26, LRP1, CD52, IL-4Rα, VAP-1, EPO receptor, integrin αv, TIM-3, Grp78, LIGHT, TLR2, TLR3, PAR-2, NRP2, GLP-1 receptor, hedgehog, and syndecan-1.

[0025] In some embodiments, the one or more drugs are selected from the group consisting of Atezolizumab, EgA1, Ipilimumab, Nivolumab, KN035, Urelumab, Foralumab, Muromonab, Adalimumab, and therapeutically active antigen-binding fragments or variants thereof. In some embodiments, the one or more drugs are selected from the group consisting of ANB032, Rosnilimab, LY3361237, Encelimab, Covolimab, Imsidolimab, Dostallimab, and therapeutically active antigen-binding fragments or variants thereof.

[0026] In some embodiments, the one or more drugs are a cytokine selected from the group consisting of IL1, IL1 alpha, IL1 beta, IL2, IL3, IL4, IL6, IL7, IL8, IL9, IL10, IL11, IL12, IL13, IL14, IL15, IL16, IL17, IL18, IL19, IL20, IL21, IL22, IL23, IL24, IL25, IL26, IL27, IL28, IL29, IL30, IL31, IL32, IL33, IL34, IL35, IL36, GM-CSF, TGF-β, CSF-1, insulin, GLP-1, HGH, VEGF, PDGF, BMP, EPO, G-CSF, IL-11, IFN-α, IFN-β, and IFN-γ, or a therapeutically active fragment or variant thereof.

[0027] In some embodiments, the proteinaceous prodrug construct is encoded by an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, and SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, or SEQ ID NO:25.

[0028] The present invention also provides nucleic acids encoding the proteinaceous prodrug constructs according to the present invention. Vectors comprising these nucleic acids are also provided. In such vectors, the nucleic acids encoding the proteinaceous prodrug constructs may be operably linked to a promoter and, optionally, to additional regulatory sequences that regulate the expression of the nucleic acid. Host cells comprising such vectors are also provided. In some embodiments, the host cells are bacteria or eukaryotic, e.g., mammalian cells.

[0029] The present invention also relates to therapeutic applications of the proteinaceous prodrug constructs of the present invention and their use in the manufacture of a medicament for treating a disease or disorder in a subject in need of such treatment.

[0030] In some embodiments, the proteinaceous prodrug constructs of the present invention find use in methods of treating or preventing a disease or disorder in a subject in need of such treatment or prevention, the methods comprising administering to the subject a therapeutically effective amount of a proteinaceous prodrug construct, nucleic acid, vector, or host cell of the present invention.

[0031] In some embodiments, the disease or disorder is a disease or disorder of the nervous system, eyes, circulatory system, respiratory system, digestive system, or skin. In some embodiments, the disease or disorder is a neoplasm, a blood disorder, a metabolic disorder, an autoimmune disease, an immunodeficiency, or an infectious disease. In some embodiments, the neoplasm is a cancer selected from brain cancer, glioblastoma, lung cancer, colorectal cancer, skin cancer, malignant melanoma, pancreatic cancer, bladder cancer, liver cancer, breast cancer, eye cancer, and prostate cancer, and the cancer is a blood cancer such as selected from the group consisting of multiple myeloma, acute myeloblastic leukemia, chronic myelogenous leukemia, acute lymphocytic leukemia, and chronic lymphocytic leukemia, or the cancer is malignant melanoma, breast cancer, non-small cell lung cancer, pancreatic cancer, head and neck cancer, liver cancer, sarcoma, and B-cell lymphoma. In some embodiments, the autoimmune disease is selected from arthritis (eg, rheumatoid arthritis or psoriatic arthritis), multiple sclerosis, systemic lupus erythematosus, and inflammatory bowel disease.

[0032] The present invention also provides a method for making the proteinaceous prodrug construct of the present invention. Such a method comprises (i) introducing into a host cell an expression vector comprising a nucleic acid encoding the proteinaceous prodrug construct, (ii) growing the host cell under conditions that allow expression of the proteinaceous prodrug construct from the vector, and (iii) purifying the proteinaceous prodrug construct. The nucleic acid is typically operably linked to a promoter and, optionally, to one or more additional regulatory sequences that regulate expression of the nucleic acid.

[0033] The following figures illustrate the invention using proteinaceous prodrug constructs that include alpha-2-macroglobulin (A2M) as the CPAMD protein. Those skilled in the art of proteinaceous prodrug design will recognize that other CPAMD proteins can replace A2M. [Brief description of the drawings]

[0034] [Figure 1A] FIG. 1A shows a schematic overview of a proteinaceous prodrug construct (1), e.g., a fusion protein, comprising a CPAMD protein (2), e.g., A2M, fused to one or more drugs (e.g., one or more nanobodies) (3) that are located within or near the RBD domain of the CPAMD protein. The one or more drugs (3) are inaccessible when the bite region of the CPAMD protein is not proteolytically cleaved (inactive or "native" structure I). The one or more drugs (3) are accessible when the bite region is cleaved by a protease (4) (active structure II). When the protease (4) cleaves the "bait region", the protease (4) becomes trapped inside the proteinaceous prodrug construct (1). [Figure 1B] FIG. 1B shows a schematic overview of different fusion strategies of CPAMD proteins (e.g., A2M) and drugs. [Diagram 2] Figure 2A-C shows native PAGE (A) and SDS-PAGE (B) analysis of wild-type A2M and fusion constructs of A2M with antibody scFvs derived from atezolizumab, ipilimumab, and nivolumab, as indicated. Prior to analysis, samples were treated with methylamine (MA) or thermolysin, as indicated. (C) is a schematic of the domain organization of A2M-antibody constructs, showing the sizes of products generated by thiol ester autolysis and bite region cleavage. [Diagram 3]Figure 3A-I shows the structure dependence of antigen binding by A2M-antibody as measured by biolayer interferometry. (A) shows the interaction between A2M-atezolizumab (purified by one round of depletion using PD-L1 resin, see Example 4) and immobilized PD-L1-hFc. Control and methylalanine-treated A2M-atezolizumab show an approximately 149-fold difference in their effective concentrations calculated from the fitted kobs values ​​for their association. (B) shows the interaction between A2M-EgA1 (purified by two rounds of depletion using LRP1 resin, see Example 4) and immobilized EGFR-hFc. Control and methylalanine-treated or thermolysin-treated samples show an approximately 63-fold difference in their effective concentrations. (C) shows the interaction between A2M-ipilimumab (purified by three rounds of depletion using LRP1 resin) and immobilized CTLA-4-hFc. (D) shows the interaction between A2M-Nivolumab (purified by three rounds of depletion using LRP1 resin) and immobilized PD-1-hFc. (E) shows the interaction between A2M-KN035 (not enriched for native A2M) and immobilized PD-L1-hFc. (F) shows the interaction between A2M-Urelumab (purified by three rounds of depletion using LRP1 resin) and immobilized 4-1BB-hFc. (G) shows the interaction between A2M-Foralumab (not enriched for native A2M) and immobilized CD3γε-hFc. (H) shows the interaction between A2M-Muromonab (not enriched) and immobilized CD3γε-hFc. In panels G and H, the +thermolysin sensorgrams have the signal from the biosensor associated with thermolysin only subtracted due to the low intensity response. (I) shows the interaction between A2M-adalimumab (not concentrated) and immobilized TNFα. [Figure 4]Figure 4A-E shows the enrichment of native A2M-antibodies using affinity depletion. (A) A2M-atezolizumab was depleted using a resin coated with its cognate antigen, PD-L1. One round of depletion was performed. Antigen binding of untreated samples before and after depletion was then compared using biolayer interferometry. (B-D) A2M-nivolumab, A2M-ipilimumab, and A2M-urelumab were depleted using LRP1-coated resin. Three rounds of depletion were performed for each A2M-antibody, and then its antigen binding before and after depletion was compared using biolayer interferometry. (E) A2M-ipilimumab was depleted by three rounds with Protein L resin, and its antigen binding before and after was compared using biolayer interferometry. [Diagram 5] Figure 5 shows immune checkpoint blockade by A2M-atezolizumab in a cell bioassay of PD-1 / PD-L1 blockade. PD-1+ Jurkat T cells carrying an NFAT-driven luciferase gene to report NFκB signaling were co-cultured with PD-L1+ CHO-K1 cells expressing a TCR agonist in the presence of a dilution series of A2M-atezolizumab in its native and methylamine-treated conformations, or a dilution series of atezolizumab scFv fused to a human Fc region. Luminescence responses are shown after subtracting background from control cells followed by normalizing responses to the maximum response. EC50 curves were fitted using linear regression and the maximum response and EC50 values ​​from the fitting are shown for each antibody. [Figure 6]Figure 6A-C shows the structure and functionality of tabular rasa A2M containing a bait region that cannot be cleaved by proteases. (A) shows the wild-type, tabular rasa (TR) and TR K704 bait regions. Basic residues (i.e., cleavage sites for trypsin or LysC) are highlighted. (B) shows pore-restricted native PAGE of A2M incorporating the three given bait region sequences. All constructs initially showed slow electrophoretic mobility characteristic of the native structure of A2M; upon methylamine aminolysis or bait region cleavage, A2M collapses and shows a much faster electrophoretic mobility. Both wild-type A2M and A2M TR K704 were degraded by trypsin, and only A2M TR K704 was degraded by LysC; A2M TR was not degraded by either protease. (C) shows a reducing SDS-PAGE of the same A2M samples as in panel B. The thiol ester-dependent thermal fragmentation bands (TE120 and TE60) disappeared upon methylamine treatment. Cleavage of the bait region of A2M yielded its .about.85 and .about.95 N- and C-terminal fragment bands; the C-terminal fragment further formed high MW multimeric products through thiol ester-mediated conjugation. If the bait region is not cleavable by trypsin or LysC, A2M is cleavable outside the bait region without any activation of its thiol ester. A2M TR K704 forms a strong .about.250 kDa band upon proteolytic activation due to thiol ester-mediated conjugation of the bait region lysine residues. [Figure 7]Figure 7A-D show the incorporation of MMP2 substrate sites into tabular A2M. (A) shows the bait region sequences for wild-type A2M, TR A2M, and four TR bait regions, each incorporating a different MMP2 substrate sequence (A21A, B74, C9, and S1). The MMP2 recognition sequence is highlighted in each sequence; cleavage occurs N-terminal to the bolded hydrophobic residue. (B) A2M with these six bait regions was digested with MMP2 and nine other human proteases and cleavage was assessed by SDS-PAGE. Proteases that cleave the bait region are indicated by + for complete cleavage (relative to wild-type A2M) or (+) for partial cleavage. The TR bait region was not cleaved by any of the proteases tested, and the respective MMP2 substrate was cleaved by all tested MMPs. The TR S1 bait region was not cleaved by proteases other than MMPs, indicating increased selectivity of inhibition compared to the wild-type bait region. (C-D) Pore-restricted native PAGE and reduced SDS-PAGE of six A2Ms with and without MMP2 cleavage, respectively. All constructs had similar bait regions cleaved by MMP2, resulting in structural collapse and the appearance of high MW multimeric products in SDS-PAGE, with the exception of A2M TR. [Figure 8]Figure 8A-C shows the optimization of the production and inhibitory capacity of A2M TR S1. (A) Several modifications of the MMP2 substrate bait region, tabula rasa S1, were tested for their ability to improve the formation of native A2M and its inhibitory capacity on MMP2. TR S1 QRT4 reintroduces a quarter of the wild-type bait region. Two different S1 positions (truncations at positions 710 or 703) were tested in TRΔ7, which shortens the TR bait region by 7 residues. (B) shows the pore-restricted native PAGE of A2M with the indicated bait regions. A2M TR S1 is expressed with a significant amount of non-native A2M. This non-native A2M could be removed by depletion using LRP1-conjugated resin. Instead, the native content was improved in TRΔ7 and TR QRT4. (C) The ability of the indicated A2M to inhibit MMP2 digestion of DQ gelatin was determined. The fit curve calculated from the experimental data points by linear regression is shown as a dotted line. Error bars represent standard; n=3. [Figure 9] Figures 9A-D show A2M antibodies incorporating engineered bait regions. (A) shows the bait region sequences for the wild-type A2M bait region, the truncated MMP2 substrate bait region "TRΔ7 S1 I703" described in Example 6, and the additional engineered bait region "TRΔ7 S1 I703 P704". (B) Pore-restricted native PAGE and (C) reduced SDS-PAGE of wild-type A2M, A2M-atezolizumab with the wild-type bait region, and A2M-atezolizumab with the TRΔ7 S1 I703 bait region are shown. A2M was analyzed untreated, treated with methylamine, or treated with a 0.5:1 or 4:1 molar ratio of MMP2 to A2M as indicated. (D) Biolayer interferometry was used to assess PD-L1 binding by A2M-atezolizumab with the three bait regions shown in panel A before and after MMP2 cleavage. The biosensor associated with MMP2 alone without A2M-atezolizumab is included to account for this background binding. A2M-atezolizumab with the wild-type bait region was further cleaved using thermolysin for comparison. [Figure 10] Figure 10A-B: (A) Reduced SDS-PAGE analysis of purified A2M-PD1. A2M-PD1 is expressed and purified to high purity by the same protocol as wild-type A2M or A2M-antibody. Formation of an internal thiol ester in A2M-PD1 leads to heat-induced fragmentation at the thiol ester site under denaturing conditions, resulting in N- and C-terminal product bands. (B) A2M-PD1 binding to immobilized PD-L1 assessed by biolayer interferometry. PD-L1 binding by A2M-PD1 without treatment to alter its structure or after methylamine- or thermolysin treatment to disrupt its structure is shown. A reference biosensor with added thermolysin without A2M-PD1 was included to account for nonspecific binding of thermolysin to the biosensor surface and was subtracted from the A2M-PD1+thermolysin sensorgram. A2M-PD1 after LRP1 depletion was also included without treatment and after methylamine treatment. [Figure 11] 11A-B show (A) reducing SDS-PAGE analysis of purified A2M-IL2. A2M-IL2 is expressed and purified to high purity by the same protocol as wild-type A2M or A2M-antibody. Formation of an internal thiol ester in A2M-IL2 leads to heat-induced fragmentation at the thiol ester site under denaturing conditions, resulting in N- and C-terminal product bands. (B) shows A2M-IL2 binding to immobilized IL-2Rα assessed by biolayer interferometry. IL-2Rα binding by A2M-IL2 without treatment to alter its structure or after methylamine- or thermolysin-treatment to disrupt its structure is shown. A2M-IL2 after three rounds of LRP1 depletion was assessed in the same way. [Figure 12-1]FIG. 12 shows (A) the interaction between 5 nM A2M-fusion-EgA1 measured using Biolayer Interferometry with immobilized human EGFR before and after methylalanine treatment during 1 hour association and 1 hour dissociation. (B) the interaction between 5 nM A2M-iRBD-EgA1 measured using Biolayer Interferometry with immobilized human EGFR before and after methylalanine or thermolysin treatment during 1 hour association and 1 hour dissociation. (C-E) the interaction between 5 nM A2M-miRBD-EgA1, A2M-miRBD-KN035, and A2M-miRBD-atezolizumab measured using Biolayer Interferometry with immobilized EGFR or PD-L1 before and after methylalanine treatment during 1 hour association and 1 hour dissociation (or 2 hours association and 10 minutes dissociation in the case of A2M-miRBD-atezolizumab). (F) shows the interaction between 10 nM A2M-tRBD-EgA1 measured during 1 hour association and dissociation with immobilized EGFR before and after methylalanine treatment. [Figure 12-2] Same as above. [Figure 12-3] Same as above. [Figure 13]FIG. 13 shows the RBD domain of A2M (residues 1335-1474 of SEQ ID NO:1) and highlights four proposed sites that can be used for insertion of drugs to achieve conformation-dependent binding. These sites, as demonstrated by the ciRBD, iRBD, miRBD, and tRBD fusion approaches, are residues 1392-1404 or 1391-1405 (loop 2), as well as residues 1368-1379 (loop 1), 1420-1426 (loop 3), and 1450-1457 (loop 4), all of which are flexible linkers between beta strands in spatial proximity to 1392-1404 and point in the same direction on the RBD domain. In contrast, residue 1468 defines the position for drug insertion in the A2M-fusion-EgA1 construct, and no conformation-dependent binding was obtained, indicating that this opposite side of the RBD domain is not suitable for achieving conformation-dependent binding. The RBD domain structure (from PDB accession no. 7VON) is represented as a schematic diagram, with the Cα atoms of the indicated residues shown as spheres. The RBD domain is shown from two different angles, as indicated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The invention will now be described in further detail below.

[0036] General In order that the present invention may be more readily understood, certain terms are first defined below. Additional definitions for the following terms, as well as other terms, are set forth throughout the specification.

[0037] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, "a ribonucleotide" is understood to refer to one or more ribonucleotides. Thus, the terms "a" (or "an"), "one or more," and "at least one" can be used interchangeably herein.

[0038] Unless specifically stated or clear from the context, the term "or" as used herein is understood to be inclusive and encompass both "or" and "and". Furthermore, "and / or" as used herein should be interpreted as an explicit disclosure of each of two specific features or components, together with or without the other. Thus, the term "and / or" as used herein in phrases such as "A and / or B" is intended to include "A and B", "A or B", "A" (single), and "B" (single). Similarly, the term "and / or" as used in phrases such as "A, B, and / or C" is intended to encompass each of the following aspects: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (single); B (single); and C (single).

[0039] Throughout this specification and the embodiments, the words "have" and "comprise" or variations such as "has," "having," "comprises," or "comprising" are understood to mean the inclusion of a stated element, function, or integer, or group of elements, functions, or integers, but not the exclusion of any other elements, functions, or integers, or group of elements, functions, or integers. Wherever embodiments are described herein using the language "comprising" or its grammatical equivalent "having," it is further understood that otherwise similar embodiments described with the terms "consisting of" and / or "consisting essentially of" are also provided.

[0040] As used herein, the term "about" refers to an interval of accuracy that a person skilled in the art would understand to still ensure the technical effect of the function in question. This term indicates a deviation of ±10% from the indicated numerical value. In some embodiments, the deviation is ±5% of the indicated numerical value. In certain embodiments, the deviation is ±1% of the indicated numerical value.

[0041] The terms "mutant" and "homolog" are used interchangeably and refer to a protein in which at least one function of the reference protein is preserved (e.g., undergoes a structural change upon cleavage by a protease). In some embodiments, the mutant or homolog is at least 70%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or 99% identical to a wild-type version of the reference protein (e.g., a CPAMD protein such as A2M, e.g., human A2M, comprising or consisting of the amino acid sequence set forth in SEQ ID NO:1).

[0042] As used herein, the term "fragment" refers to a protein that is truncated by one or more amino acids (e.g., at the N-terminus and / or C-terminus) or contains one or more deletions of amino acids while preserving at least one function of the reference protein (e.g., specifically binding to an antigen or receptor, e.g., in the case of an antibody or cytokine, or undergoing a structural change upon cleavage by a protease, e.g., in the case of a CPAMD protein such as A2M).

[0043] As used herein, the terms "therapeutic" or "therapeutically active" refer to any pharmaceutical agent, drug or composition that can be used to treat or prevent a disease, illness, condition, or disorder of bodily function.

[0044] As used herein, the term "substantially" refers to a qualitative state that exhibits the full or nearly full extent of a desired characteristic or property.Those skilled in the art of biology understand that biological and chemical phenomena rarely, if ever, proceed to completion and / or completeness or achieve or avoid absolute results.Therefore, the term "substantially" is used herein to express the potential lack of completeness inherent in many biological and chemical phenomena.

[0045] As used herein, the term "in vitro" refers to events that take place not inside a multicellular organism but in an artificial environment, e.g., in a test tube or reaction vessel, in cell culture, and the like.

[0046] As used herein, the term "in vivo" refers to events that occur within multicellular organisms, such as humans and non-human animals. In the context of cell-based systems, the term may be used to refer to events that occur within living cells (as opposed to, for example, in vitro systems).

[0047] definition Prior to discussing the present invention in more detail, the following terms and conventions are first defined.

[0048] Alpha-2-macroglobulin (A2M) The term "A2M" should be understood as human protein A2M (NCBI #9606, Uniprot P01023), or a variant or fragment thereof that contains (1) a bait region with at least one protease cleavage site, and (2) a receptor binding domain (RBD), and can change structure upon proteolytic cleavage of at least one protease cleavage site. A2M is also known as C3 and PZP-like alpha-2-macroglobulin domain-containing protein 5 (CPAMD5). The amino acid sequence of human A2M is given in SEQ ID NO: 1, and has naturally occurring polymorphisms I1000V and N639D. Unless otherwise indicated, the residue numbers provided herein to identify specific amino acids or regions of A2M refer to the residues shown in SEQ ID NO: 1. It will be apparent to one of skill in the art that the numbering may be different for A2M variants that contain one or more of the modifications described herein.

[0049] Antigen targeting moiety The term "antigen targeting moiety" of the present invention includes monoclonal, recombinant, chimeric, humanized, fully human, single chain, single domain and / or bispecific antibodies, including single chain variable fragments, antibody fragments. Examples of such fragments include Fab F(ab'), F(ab)', Fv, and sFv fragments. Antibodies can be produced by enzymatic cleavage of full-length antibodies or by recombinant DNA techniques, such as expression of recombinant plasmids containing nucleic acid sequences encoding antibody variable regions.

[0050] A "single-chain Fv", "sFv" or "scFv" antibody comprises a VH domain and a VL domain in a single polypeptide chain. The VH and VL are typically linked by a peptide linker. Any suitable linker may be used. In some embodiments, the linker is (GGGGS)n (SEQ ID NO: 223) or (GGS)n. In some embodiments, n=1, 2, 3, 4, 5, or 6.

[0051] The term "single domain antibody" refers to an antigen-targeting moiety in which one variable domain of an antibody specifically binds to an antigen in the absence of another variable domain. Single domain antibodies include nanobodies.

[0052] An antigen is a molecule or a portion of a molecule to which an antibody can bind, which can further induce an animal to produce an antibody capable of binding to the epitope of that antigen. An antigen can have one or more epitopes. The specific reaction referred to above is meant to indicate that an antigen reacts highly selectively with its corresponding antibody and not with the multitude of other antibodies that can be elicited by other antigens.

[0053] A monoclonal antibody (mAb) comprises a substantially homogeneous population of antibodies specific to an antigen, which population contains substantially similar epitope binding sites. Such antibodies may be of any immunoglobulin class, including IgG, IgM, IgE, IgA, IgD and any subclass thereof. Hybridomas producing the monoclonal antibodies of the invention may be cultured in vitro, in situ, or in vivo. Production of high titers in vivo or in situ is the preferred method of production.

[0054] A chimeric antibody is a molecule in which different portions are derived from different animal species, such as one having a variable region derived from a murine monoclonal antibody and a human immunoglobulin constant region.

[0055] The term "chimeric antibody" as used herein includes monovalent, divalent or polyvalent immunoglobulins. A monovalent chimeric antibody is a dimer (HL) formed by a chimeric H chain linked to a chimeric L chain through a disulfide bridge. A divalent chimeric antibody is a tetramer (H2L2) formed by two HL dimers linked through at least one disulfide bridge. Multimeric chimeric antibodies can also be produced, for example, by using aggregated CH regions (e.g., from IgM H chains, or [micron] chains).

[0056] The murine and chimeric antibodies, fragments and regions of the invention may comprise individual heavy (H) and / or light (L) immunoglobulin chains.

[0057] Selective binding agents such as antibodies, fragments, or derivatives having chimeric heavy and light chains of the same or different variable region binding specificities can also be prepared by appropriate combination of the individual polypeptide chains.

[0058] In some embodiments, the term "antibody" as used herein refers to a single chain or single domain antibody.

[0059] CPAMD The term "CPAMD" should be understood as the C3 and PZP-like alpha-2-macroglobulin domain-containing protein (CPAMD) family, to which A2M belongs, or as a member of such a family. A descriptive list of CPAMD proteins is provided in Table 1. In some embodiments, the proteinaceous prodrug constructs of the present invention may comprise variants or fragments of naturally occurring CPAMD proteins. Such variants or fragments retain the ability to shield one or more drugs and to alter their structure upon proteolytic cleavage of at least one protease cleavage site contained therein, making accessible one or more drugs contained in the proteinaceous prodrug construct.

[0060] RBD domain The term "RBD" or "RBD domain" should be understood as the receptor binding domain of a CPAMD protein (e.g., A2M). In the native human A2M protein, the RBD is located at its C-terminus and spans amino acids 1335-1474 of A2M. Y1452 and Y1453 are involved in the formation of a thiol ester group. The thiol ester group stabilizes the molecule in its "native" structure. The amino acid sequence of the RBD domain of native human A2M is given in SEQ ID NO: 3. The RBD domain is also known as the macroglobulin 8 (MG8) domain.

[0061] In the proteinaceous prodrug constructs described herein, one or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are positioned within or near the RBD such that the CPAMD protein (e.g., A2M) is still able to change structure upon proteolytic cleavage of at least one protease cleavage site contained in the bait region of the CPAMD protein.

[0062] Unreachable The term "inaccessible" should be understood to mean that the drug of the proteinaceous prodrug construct has a reduced ability to interact with its binding partner when the construct is in the "closed" conformation (not proteolytically cleaved). Thus, the drug is "inaccessible" to its binding partner (e.g., when the drug is an antibody such as an scFv or nanobody).

[0063] Thus, the term "inaccessible" can also be understood as the drug being "inactive", "deactivated" or "shielded".

[0064] Thus, in an embodiment, a. One or more drugs are inaccessible unless the bait region in the CPAMD protein (e.g., A2M) is proteolytically cleaved; b. When the bait region in the CPAMD protein (eg, A2M) is proteolytically cleaved, one or more drugs are accessible.

[0065] Byte Area The term "bait region" should be understood as a region of a CPAMD protein (e.g., A2M) that contains at least one protease cleavage site. In the native human A2M protein, the bait region spans amino acids 690-728 of A2M. The sequence of the bait region of native human A2M is given in SEQ ID NO: 4. The bait region of native human A2M is preferentially cleaved by most proteases, and bait region cleavage triggers a conformational change in A2M. The bait region sequence can be modified to alter the selection of proteases that can cleave the bait region and trigger a conformational change in the CPAMD protein.

[0066] Biopharmaceuticals The term "biopharmaceutical moiety" should be understood as a protein or protein fragment (e.g., peptide or polypeptide) with therapeutic properties that can be incorporated into a proteinaceous prodrug construct together with a CPAMD protein (e.g., A2M) to create a proteolytically activatable prodrug. This term is used interchangeably with the term "drug" herein. Examples of biopharmaceutical moieties include antibody fragments such as single domain antibodies (e.g., nanobodies) or single chain variable fragments (scFv), cytokines, or fragments of cell surface receptors or ligands. Exemplary sequences are given for the EGFR-binding nanobody EgA1 (SEQ ID NO: 27), the PDL1-binding atezolizumab-derived scFv (SEQ ID NO: 28), the PDL1-binding nanobody KN035 (SEQ ID NO: 29), the PD1-binding nivolumab-derived scFv (SEQ ID NO: 30), the CTLA-4-binding ipilimumab-derived scFv (SEQ ID NO: 31), the CD3-binding foralumab-derived scFv (SEQ ID NO: 32), the CD3-binding muromonab-derived scFv (SEQ ID NO: 33), the 4-1BB-binding urelumab-derived scFv (SEQ ID NO: 34), the TNFα-binding nivolumab-derived scFv (SEQ ID NO: 35), the IL2 cytokine (SEQ ID NO: 36), or the extracellular domain of the PD1 receptor (SEQ ID NO: 39).

[0067] Terms such as "biopharmaceutical moiety," "drug," "therapeutic peptide," "therapeutic polypeptide" or "therapeutic protein," "active agent" are used herein to refer to proteinaceous compounds that can be used to treat or prevent a disease, illness, condition, or disorder of a bodily function.

[0068] ciRBD The term "ciRBD" should be understood as a proteinaceous fusion construct between a CPAMD protein (e.g., A2M) and a biopharmaceutical moiety (e.g., a therapeutic peptide, polypeptide or protein), where the biopharmaceutical moiety is placed in the RBD domain at a position between residues corresponding to residues 1402 and 1403 of native human A2M, without removing any residues of the CPAMD protein. Linker sequences can be used to connect the N-terminus of the biopharmaceutical moiety to the carboxyl terminus of residue 1402 (SEQ ID NO: 78) or the C-terminus of the biopharmaceutical moiety to the amino terminus of residue 1405 (SEQ ID NO: 79). Examples of ciRBD fusion constructs incorporating EgA1 nanobody (SEQ ID NO: 27) into A2M are given in SEQ ID NOs: 5-6.

[0069] iRBD The term "iRBD" should be understood as a proteinaceous fusion construct between a CPAMD protein (e.g., A2M) and a biopharmaceutical moiety (e.g., a therapeutic peptide, polypeptide or protein), where the biopharmaceutical moiety replaces residues of the RBD domain that correspond to residues spanning from position 1392, inclusive, to position 1403, inclusive, in native human AM. The biopharmaceutical moiety is connected to residue 1391 by an N-terminal linker (SEQ ID NO: 80) and to residue 1404 by a C-terminal linker (SEQ ID NO: 81). An example of an iRBD fusion construct incorporating an EgA1 nanobody (SEQ ID NO: 27) into A2M is given in SEQ ID NOs: 84-85.

[0070] miRBD The term "miRBD" should be understood as a proteinaceous fusion construct between a CPAMD protein (e.g., A2M) and a biopharmaceutical moiety (e.g., a therapeutic peptide, polypeptide or protein), where the biopharmaceutical moiety replaces residues of the RBD domain corresponding to residues spanning from position 1393, inclusive, to position 1395, inclusive, of native human AM. The biopharmaceutical moiety is connected to residue 1392 by an N-terminal linker (SEQ ID NO: 82) and to residue 1396 by a C-terminal linker (SEQ ID NO: 83). An example of a miRBD fusion construct incorporating EgA1 nanobody (SEQ ID NO: 27) into A2M is given in SEQ ID NOs: 86-87.

[0071] tRBD The term "tRBD" should be understood as a proteinaceous fusion construct between a CPAMD protein (e.g., A2M) and a biopharmaceutical moiety (e.g., a therapeutic peptide, polypeptide or protein), where the biopharmaceutical moiety is incorporated into the RBD domain in position C-terminus. Furthermore, residues 1393 to 1402 of the RBD domain, or the corresponding residues of the RBD domain of another CPAMD protein, are modified to allow the formation of an α-helix having a sequence that is complementary to the sequence of another α-helix that is placed at the N-terminus of the biopharmaceutical moiety. The RBD domain α-helix and the α-helix at the N-terminus of the biopharmaceutical moiety are designed to interact with each other in a coiled-coil interaction. These coiled-coil interactions bring the biopharmaceutical moiety into a position relative to the RBD domain that promotes shielding of the biopharmaceutical moiety by the CPAMD protein (e.g., A2M). The biopharmaceutical moiety is linked at its N-terminus to the C-terminus of its adjacent α-helix by a 2-residue linker, and the α-helix itself is linked at its N-terminus to the C-terminus of the RBD domain by a 15-residue linker. Examples of tRBD fusion constructs incorporating EgA1 nanobody (SEQ ID NO:27) into A2M are provided in SEQ ID NOs:92-93.

[0072] Epitope In the present context, the term "epitope" refers to that part of an antigen that is recognised by the immune system.

[0073] Eukaryotic Expression Vectors In the present context, a "eukaryotic expression vector" refers to a tool that is used to introduce a specific coding polynucleotide sequence into a target cell and contains expression control sequences (e.g., a suitable promoter sequence) operably linked to the nucleotide sequence to be expressed.

[0074] Sequence identity In the present context, the term "sequence identity" is defined herein as sequence identity at the nucleotide, base or amino acid level between genes or proteins, respectively. Specifically, DNA and RNA sequences are considered to be identical if a transcript of the DNA sequence can be transcribed into the corresponding RNA sequence.

[0075] Thus, in the present context, "sequence identity" is a measure of identity between proteins at the amino acid level and between nucleic acids at the nucleotide level. Protein sequence identity may be determined by comparing the amino acid sequence at a given position in each sequence when the sequences are aligned. Similarly, nucleic acid sequence identity may be determined by comparing the nucleotide sequence at a given position in each sequence when the sequences are aligned.

[0076] To determine the percent identity of two amino acid sequences or two nucleic acids, the sequences are aligned for optimal comparison purposes (e.g., gaps may be introduced into the sequence of a first amino acid or nucleic acid sequence for optimal alignment with a second amino acid or nucleic acid sequence). The amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared. If a position in the first sequence is occupied by the same amino acid residue or nucleotide as the corresponding position in the second sequence, then the molecules are identical at that position. The percent identity between the two sequences is a function of the number of identical positions shared by the sequences (i.e., % identity = number of identical positions / total number of positions (e.g., overlapping positions) x 100). In one embodiment, the two sequences are the same length.

[0077] In another embodiment, the two sequences are of different lengths and gaps are found at different positions. The sequences may be manually aligned and the number of identical amino acids counted. Alternatively, alignment of two sequences for determining percent identity may be accomplished using a mathematical algorithm. Such an algorithm is incorporated in the BLASTN and BLASTX programs of (Altschul et al., 1990). BLAST nucleotide searches may be performed using the NBLAST program to obtain nucleotide sequences that are homologous to the nucleic acid molecules of the present invention. BLAST protein searches may be performed using the BLASTX program to obtain amino acid sequences that are homologous to the protein molecules of the present invention.

[0078] To obtain gapped alignment for comparison purposes, gapped BLAST may be used. Alternatively, PSI-Blast may be used to perform iterative searches to detect distant relationships between molecules. When using BLASTN, BLASTX, and gapped BLAST programs, the default parameters of the respective programs may be used. See http: / / www.ncbi.nlm.nih.gov. Alternatively, sequence identity may be calculated after aligning sequences with, for example, the BLAST program in the EMBL database (www.ncbi.nlm.gov / cgi-bin / BLAST). In general, the default settings, for example, for "score matrix" and "gap penalty", may be used for alignment. In the context of the present invention, the BLASTN and PSI BLAST default settings may be advantageous.

[0079] Percent identity between two sequences may be determined using techniques similar to those described above, with or without gaps.Only exact matches are counted when calculating percent identity.Therefore, embodiments of the present invention relate to sequences of the present invention that have a certain degree of sequence diversity.

[0080] subject The term "subject" includes humans of all ages, other primates (e.g., cynomolgus monkeys, rhesus monkeys), mammals in general, including commercially relevant mammals such as cows, pigs, horses, sheep, goats, mink, ferrets, hamsters, cats and dogs, and birds. A preferred subject is a human.

[0081] The term "subject" also includes healthy subjects of the population, particularly healthy subjects who are exposed to pathogens and in need of protection against infection, such as health care workers.

[0082] It should be noted that embodiments and features described in the context of one of the aspects of the invention also apply to the other aspects of the invention.

[0083] All patent and non-patent references cited in this application are hereby incorporated by reference in their entirety.

[0084] Detailed Description of the Invention CPAMD protein The proteinaceous prodrug constructs described herein include complement 3 and pregnancy associated protein-like, alpha-2-macroglobulin domain-containing (CPAMD) proteins, or variants or fragments thereof. The CPAMD proteins, or variants or fragments thereof, contain a bite region with at least one protease cleavage site and a receptor binding domain (RBD).

[0085] In some embodiments, the one or more drugs are disposed inside or near any one of loops 1-4 (e.g., loop 1, loop 2, loop 3, or loop 4) of the RBD. In one particular embodiment, the one or more drugs are disposed inside loop 2. In another particular embodiment, the one or more drugs are disposed inside loop 4. In even more particular embodiments, the one or more drugs are disposed near loop 2 of the RBD.

[0086] In the proteinaceous prodrug constructs of the invention, the CPAMD protein, or a variant or fragment thereof, shields one or more drugs. The CPAMD protein, or a variant or fragment thereof, can change structure upon proteolytic cleavage of at least one protease cleavage site, rendering one or more drugs accessible.

[0087] Although the present invention has been described in further detail with respect to proteinaceous prodrug constructs in which the CPAMD protein is alpha-2-macroglobulin (A2M), or a variant or functional homologue thereof, those skilled in the art of proteinaceous prodrug design will recognize that other CPAMD proteins can replace A2M.

[0088] In some embodiments, the proteinaceous prodrug construct is a fusion protein. In one embodiment, the proteinaceous fusion construct comprises a CPAMD family member fused to one or more drugs; or a modified CPAMD family member (2) fused to one or more drugs, and the one or more drugs are located inside or near the RBD domain of A2M. Proteinaceous fusion construct and proteinaceous prodrug are used interchangeably herein.

[0089] In some embodiments, the one or more drugs are inserted into any one of loops 1-4 of the RBD. In some embodiments, the loop is modified by addition, substitution, or deletion of one or more amino acids to accommodate the one or more drugs. In some embodiments, the one or more drugs replace one or more amino acids of the loop. In some embodiments, the loop is loop 2 of the RBD. In some embodiments, the loop is loop 4 of the RBD.

[0090] As discussed herein, placing one or more drugs near loop 2 of the RBD can be achieved by inserting (e.g., by replacing one or more residues or by direct insertion) within or within the 5 amino acid residues of loop 2. Similarly, this can be achieved by inserting (e.g., by replacing one or more residues or by direct insertion) within or within the 5 amino acid residues of loop 1, loop 3, or loop 4. Loops 1, 3, and 4 have distances of 27 Å, 21 Å, and 25 Å, respectively, to loop 2, calculated from their centers of mass. In the ciRBD fusion approach described herein, the shortest constraint between a drug and loop 2 is a 15 residue C-terminal linker. From an average length of 3.5 Å per amino acid residue, it can be calculated that one or more drugs can be positioned about 52 Å (e.g., about 50 Å, about 40 Å, about 30 Å, or about 20 Å) away from loop 2, occupying a position whose accessibility depends on the structure of the CPAMD protein (e.g., A2M).

[0091] As an alternative to direct fusion, a drug can be designed through other means to be placed an equal distance internal to loop 2 and in a similar orientation relative to the RBD domain as achieved by a direct fusion approach. For example, as described herein, a coiled-coil interaction or a high affinity interaction can be used to tether a drug to loop 2 (e.g., as in the tRBD approach described herein).

[0092] Table 1 provides a descriptive list of CPAMD proteins that may be used to practice the present invention, along with the location and sequence of their respective loops.

[0093] [Table 1-1] [Table 1-2]

[0094] In some embodiments, the CPAMD protein is selected from the group consisting of C3, C4A, C4B, C5, PZP, A2ML1, CD109, CPAMD8, ovostatin homolog 1, ovostatin homolog 2, and A2M. In some embodiments, the CPAMD protein is selected from A2M, PZP, ovostatin 1, and ovostatin 2, and functional homologs thereof. In some embodiments, the CPAMD protein is human A2M, or a functional homolog thereof, such as mammalian A2M. In certain embodiments, the CPAMD protein is A2M.

[0095] In one embodiment, the CPAMD protein is a human CPAMD protein, such as one of the proteins listed in Table 1, or variants thereof. In some embodiments, the human CPAMD protein is a variant that has been modified as described herein, e.g., the variant may include a modified byte region.

[0096] In some embodiments, the CPAMD protein has at least about 70% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In some embodiments, the CPAMD protein has at least about 75% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 80% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 85% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 90% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1.

[0097] In one embodiment, the CPAMD protein has at least about 91% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 92% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 93% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 94% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 95% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 96% sequence identity with at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 97% sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 98% sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1. In one embodiment, the CPAMD protein has at least about 99% sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1.

[0098] In a further embodiment, the CPAMD protein is a human CPAMD protein, such as a protein listed in Table 1, with the proviso that: a. the byte region has been modified as described herein; and / or b. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0099] In another embodiment, the CPAMD protein has at least about 70% sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1, provided that: a. the byte region has been modified as described herein; and / or b. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0100] In one embodiment, the CPAMD protein has at least about 80% sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1, with the proviso that: a. the byte region has been modified as described herein; and / or b. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0101] In one embodiment, the CPAMD protein has at least about 85% sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1, provided that: a. the byte region has been modified as described herein; and / or b. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0102] In one embodiment, the CPAMD protein has at least about 90% (e.g., at least about 91%, at least about 92%, at least about 93%, or at least about 95%) sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1, provided that: a. the byte region has been modified as described herein; and / or b. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0103] In one embodiment, the CPAMD protein has at least about 95% (e.g., at least about 96%, at least about 97%, at least about 98%, or at least about 99%) sequence identity to at least one of the full-length CPAMD protein sequences listed in Table 1, provided that: a. the byte region has been modified as described herein; and / or b. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0104] The RBD domains and bait regions of the CPAMD proteins listed in Table 1 are described in Table 2. The RBD domains (also called "MG8 domains") and bait regions (also called "anaphylaxis domains" in some CPAMD proteins) were identified based on their functional equivalence to the corresponding domains / regions of human A2M.

[0105] [Table 2-1] [Table 2-2] [Table 2-3]

[0106] When one or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are introduced into the RBD, they are sterically hindered from interacting with other proteins, such as their therapeutic targets. The RBD domain is a small domain (about 16 kDa) by itself. Without wishing to be bound by any particular theory, the inventors believe that the RBD domain alone cannot sterically hinder one or more drugs (e.g., therapeutic peptides, polypeptides or proteins), especially considering that there is typically a linker between one or more drugs and the RBD domain. Without wishing to be bound by any particular theory, the inventors therefore believe that other parts or multiple copies of the CPAMD protein contribute to surrounding and sequestering one or more drugs. For example, naturally occurring CPAMD proteins (e.g., A2M) form homotetramers.

[0107] In some embodiments, the CPAMD protein (e.g., A2M) forms a multimer (e.g., a dimer or tetramer). In some embodiments, the multimer comprises identical subunits (e.g., a homodimer or homotetramer). Without wishing to be bound by any particular theory, the inventors believe that contributions from one or more adjacent subunits may contribute to the sequestration of one or more drugs.

[0108] Two human CPAMD proteins are known to form dimers (typically stabilized by one or more disulfide bridges), namely A2M and pregnancy-associated protein (PZP, aka CPAMD6). In A2M, the disulfide-bridged dimer engages in additional non-covalent interactions with another disulfide-bridged dimer, mainly through its LNK domain, to form a tetramer. This tetramerization is also seen in ovostatins, such as ovostatin, which is characteristic of ducks, chickens, and frogs. Two human ovostatins, ovostatin 1 and ovostatin 2, are also predicted to be tetramers.

[0109] Thus, in some embodiments, the proteinaceous prodrug construct according to the present invention can form a multimer, for example, a dimer or a tetramer. In some embodiments, the multimer is a heteromultimer (e.g., a heterodimer or a heterotetramer). More typically, the multimer is a homodimer or homotetramer.

[0110] In some embodiments, multimer (e.g., dimer or tetramer) formation occurs through the LNK region of the CPAMD protein. In some embodiments, the tetramer is formed by two disulfide-bridged dimers (e.g., two homodimers).

[0111] The cysteines that form the intersubunit disulfide bonds responsible for the disulfide bridged dimer are found in two loops, one of which is located on the MG3 domain of the CPAMD protein and one of which is located on the MG4 domain of the CPAMD protein. These loops are defined in Table 3. The LNK regions that have been shown to be involved in the interaction between the two disulfide bridged dimers in the tetramer-forming CPAMD protein are also defined in Table 3.

[0112] [Table 3]

[0113] The iRBD, miRBD, ciRBD, and tRBD described herein create proteinaceous prodrug constructs by "locking" the position of a drug (e.g., a peptide, polypeptide, or protein) near loop 2 (residues 1392-1405) on the RBD of a CPAMD protein (e.g., A2M) by direct fusion in an iRBD / miRBD / ciRBD approach, or by tethering the drug to this position using coiled-coil interactions in a tRBD approach. Other approaches by which a drug can be tethered to this general position relative to the RBD domain will be apparent to one of skill in the art.

[0114] In some embodiments, the proteinaceous prodrug construct comprises a first interaction domain and the one or more drugs comprise a second interaction domain, and the first and second interaction domains form a complex that positions the one or more drugs near any one of loops 1-4 (e.g., loop 1, loop 2, loop 3, or loop 4) of the RBD. In one particular embodiment, the first and second interaction domains form a complex that positions the one or more drugs near loop 2. In another particular embodiment, the first and second interaction domains form a complex that positions the one or more drugs near loop 4. In some embodiments, the first interaction domain and the second interaction domain form a coiled-coil structure.

[0115] Without wishing to be bound by any particular theory, the inventors believe that using the first and second interaction domains to position one or more drugs in proximity to loop 2 of the RBD allows the CPAMD protein to adopt its "native" structure, thereby sequestering one or more drugs within its interior (thus shielding the CPAMD protein from interacting with one or more targets). Spatial proximity may be achieved, for example, by inserting the first interaction domain into loop 2 of the RBD or into one of loops 1-3 (e.g., loop 4) of the RBD.

[0116] One approach is to "dock" a drug into a CPAMD protein (e.g., A2M). This can be done using a molecule with inherent affinity for loop 2 of the RBD, such as a functional fragment of the LRP1 receptor or an antibody (e.g., a nanobody) that recognizes the loop 2 epitope.

[0117] Alternatively, the RBD of a CPAMD protein (e.g., A2M) could be modified to facilitate such docking. For example, a tag sequence could be introduced into the RBD (e.g., at the "ciRBD" position) and the drug could be fused to an antibody (e.g., a nanobody or similar small binding domain) that recognizes the tag.

[0118] Thus, in some embodiments, the first interacting domain is a tag or epitope sequence within loop 2 of the RBD, and the second interacting domain is a functional fragment of a receptor or antibody capable of specifically binding to the tag or epitope sequence.

[0119] A2M Alpha-2-macroglobulin (A2M) is a protein found in high concentrations (usually 1-5 g / L) in human plasma. A2M is a protease inhibitor with a well-characterized mechanism of action. First, the protease cleaves an exposed and vulnerable stretch of sequence called the bite region, which is permissive for cleavage by most human proteases. Bite region cleavage triggers a conformational change in A2M that causes it to collapse around the protease, trapping it within A2M and preventing the protease from accessing additional large protein substrates (Figure 1). If cleavage is rapid and sequential, up to two proteases can be inhibited by a single A2M protein. In addition to the entrapment of the instigating protease(s), two additional consequences of the triggered structural changes are: (i) a cryptic binding site on A2M for the LRP1 receptor is exposed, resulting in binding of A2M-protease complexes by cell surface LRP1 and rapid clearance of these complexes from the circulation, for example, by LRP1-expressing hepatocytes, and (ii) a reactive thiol ester moiety is exposed on A2M, allowing the formation of a covalent bond to the entrapped protease.

[0120] The present invention describes the incorporation of a biopharmaceutical moiety into A2M such that the binding ability of the biopharmaceutical moiety is modulated by the structure of A2M. Biopharmaceutical moieties suitable for use with the present invention include therapeutic peptides, polypeptides or proteins such as antibodies (e.g., single chain or single domain antibodies such as scFvs and nanobodies). In the native structure of A2M, the incorporated biopharmaceutical moiety occupies a shielded position, where the biopharmaceutical moiety has a reduced ability to interact with its therapeutic target. After the structure of A2M is altered by proteolytic cleavage of the bait region (or alternatively, by aminolysis of the thiol ester of A2M using methylamine, which triggers a similar conformational change), the biopharmaceutical moiety shows an increased ability to interact with its target. By modifying the bait region sequence of A2M, specific proteases can be designated as those that can cleave the bait region and trigger this conformational change. Taken together, this can be used to generate proteinaceous fusion constructs of A2M and biopharmaceutical moieties (e.g., therapeutic peptides, polypeptides or proteins) that function as protease-activated prodrug versions of the biopharmaceutical moieties.

[0121] In one embodiment, the invention provides a proteinaceous prodrug construct comprising: (a) an alpha-2-macroglobulin (A2M) protein, or a variant or fragment thereof; and (b) one or more drugs, wherein (i) the A2M protein, or a variant or fragment thereof, comprises (1) a bait region having at least one protease cleavage site, and (2) a receptor binding domain (RBD), (ii) the one or more drugs are positioned within or adjacent to the RBD, and (iii) the A2M protein, or a variant or fragment thereof, is capable of shielding the one or more drugs and altering structure upon proteolytic cleavage of the at least one protease cleavage site to render the one or more drugs accessible.

[0122] In some embodiments, the present invention relates to proteinaceous fusion constructs comprising alpha-2-macroglobulin (A2M) fused to one or more drugs; or modified A2M fused to one or more drugs, wherein the one or more drugs are positioned within or near the RBD domain of A2M.

[0123] In some embodiments, the one or more drugs are located within or near any one of loops 1-4 of the RBD. In some embodiments, the proteinaceous prodrug construct is a fusion protein. In some embodiments, the one or more drugs are located within any one of loops 1-4 of the RBD. In some embodiments, the loop is loop 1. In some embodiments, the loop is loop 2. In some embodiments, the loop is loop 3. In some embodiments, the loop is loop 4. In some embodiments, the loop is modified relative to the wild-type loop sequence by addition, substitution or deletion of one or more amino acids to accommodate the one or more drugs. In some embodiments, the one or more drugs replace one or more amino acids of the loop.

[0124] In one embodiment, the one or more drugs are inaccessible when the bite region in alpha-2-macroglobulin (A2M) is not proteolytically cleaved, and the one or more drugs are accessible when the bite region in alpha-2-macroglobulin (A2M) is proteolytically cleaved.

[0125] In one embodiment, cleavage of the bait region is achieved by serine-, cysteine-, aspartic acid- and / or metalloproteinases.

[0126] The drug can be located at different positions within the sequence of the proteinaceous fusion construct.

[0127] Those skilled in the art can recognize the part of the proteinaceous fusion construct that is derived from A2M. Thus, in the embodiment where a drug is inserted into the sequence of A2M, the resulting fusion construct can be considered as a first part of A2M, a drug, and a second part of A2M. In such a case, those skilled in the art can recognize the first and second parts of A2M as a complete molecule. Thus, in certain embodiments, the sequence identity of A2M should be calculated from two separate parts based on the sequence derived from A2M, and therefore without including one or more drugs.

[0128] In one embodiment, the A2M molecule is a mammalian A2M molecule, such as a human A2M molecule, or a variant thereof.

[0129] In one embodiment, the A2M molecule is a human A2M molecule, such as a sequence according to SEQ ID NO: 1, or a variant thereof. In some embodiments, the human A2M molecule is a variant that has been modified as described herein, e.g., a variant that may include a modified byte region.

[0130] In some embodiments, the A2M molecule has at least about 70% sequence identity to the sequence according to SEQ ID NO: 1. In some embodiments, the A2M molecule has at least about 75% sequence identity to the sequence according to SEQ ID NO: 1. In one embodiment, the A2M molecule has at least about 80% sequence identity to the sequence according to SEQ ID NO: 1. In one embodiment, the A2M molecule has at least about 85% sequence identity to the sequence according to SEQ ID NO: 1. In one embodiment, the A2M molecule has at least about 90% sequence identity to the sequence according to SEQ ID NO: 1.

[0131] In one embodiment, the A2M molecule has at least about 91% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 92% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 93% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 94% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 95% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 96% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 97% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 98% sequence identity to the sequence according to SEQ ID NO:1. In one embodiment, the A2M molecule has at least about 99% sequence identity to the sequence according to SEQ ID NO:1.

[0132] In a further embodiment, the A2M molecule is a human A2M molecule, such as a sequence according to SEQ ID NO: 1, with the proviso that: c. the byte region has been modified as described above; and / or d. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0133] In another embodiment, the A2M molecule has at least about 70% sequence identity to a sequence according to SEQ ID NO:1, with the proviso that: c. the byte region has been modified as described above; and / or d. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0134] In one embodiment, the A2M molecule has at least about 80% sequence identity to a sequence according to SEQ ID NO:1, with the proviso that: c. the byte region has been modified as described above; and / or d. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0135] In one embodiment, the A2M molecule has at least about 85% sequence identity to a sequence according to SEQ ID NO:1, with the proviso that: c. the byte region has been modified as described above; and / or d. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0136] In one embodiment, the A2M molecule has at least about 90% (e.g., at least 91%, at least 92%, at least 93%, or at least 95%) sequence identity to a sequence according to SEQ ID NO:1, with the proviso that: c. the byte region has been modified as described above; and / or d. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0137] In one embodiment, the A2M molecule has at least about 95% (e.g., at least 96%, at least 97%, at least 98%, or about 99%) sequence identity to a sequence according to SEQ ID NO:1, with the proviso that: c. the byte region has been modified as described above; and / or d. One or more drugs (e.g., therapeutic peptides, polypeptides or proteins) are inserted into the RBD region, e.g., in loop 2, e.g., by removing one or more of the residues in loop 2 as described above.

[0138] In one embodiment, the one or more drugs are positioned between 1391 and 1405 in SEQ ID NO:1.

[0139] In another embodiment, the one or more drugs are positioned after position 1335 in SEQ ID NO:1.

[0140] In another embodiment, the one or more drugs are positioned before position 1474 in SEQ ID NO:1.

[0141] In another embodiment, the one or more drugs are positioned between 1391 and 1405 in SEQ ID NO:1 or after position 1335 but before position 1474 in A2M.

[0142] In another embodiment, the A2M molecule contains one or more of the mutations K1393A, K1397A, T654C, and / or T661C.

[0143] K1393A and K1397A ablate A2M interactions with the receptors LRP1 and Grp78, respectively. LRP1 mediates the clearance of cleaved A2M, and Grp78 induces mitogenic signaling in cells upon binding. Both of these receptor interactions are potentially problematic for the drug, and therefore it would be beneficial to remove these amino acids.

[0144] The T654C and T661C mutations introduce a disulfide that bridges the two disulfide dimers of A2M, so that the entire A2M tetramer is stabilized by a disulfide bond. This prevents A2M from splitting into its two halves, which can occur during physiological conditions such as inflammation (due to oxidative damage to A2M).

[0145] In an embodiment of the invention, the invention relates to a proteinaceous fusion construct comprising alpha-2-macroglobulin (A2M) comprising a bait region having at least one protease cleavage site, said A2M fused to a peptide drug located within residues 1392-1404, 1368-1379, or 1420-1426 of the receptor binding domain (RBD) of A2M. In particular, in such an embodiment, it may occur that if the bait region in A2M is not proteolytically cleaved, then the peptide drug is inaccessible; if the bait region in A2M is proteolytically cleaved, then the peptide drug is accessible.

[0146] Although the preceding paragraphs describe placing one or more drugs within the RBD domain and introducing disulfide bridges in relation to A2M, those skilled in the art of proteinaceous prodrug design will recognize that other CPAMD proteins can be substituted for A2M and the corresponding residues in these CPAMD proteins can be identified (e.g., using the residue numbers provided in Tables 1 and 2 as a guide) to practice the present invention.

[0147] Drugs Proteinaceous prodrug constructs can contain one or more drugs or biopharmaceutical moieties (eg, therapeutic peptides, polypeptides or proteins).

[0148] In one embodiment, the one or more drugs are selected from the group consisting of an antigen targeting moiety (e.g., an antibody or antibody mimetic), a cytokine, an extracellular domain of a cell surface receptor, an extracellular domain of a cell surface ligand, and a receptor agonist.

[0149] In another embodiment, the one or more drugs are selected from the group consisting of toxins, enzymes, and protein conjugates with small molecule drugs similar to ADCs. For example, the one or more drugs may contain sites suitable for small molecule conjugation, such as cysteine ​​residues.

[0150] In a further embodiment, the toxin(s) is selected from anthrax and diphtheria toxins derived from bacteria.

[0151] In yet another embodiment, the one or more drugs are antigen-targeting moieties, such as single-chain variable fragments of an antibody.

[0152] In one embodiment, the antigen targeting moiety is selected from the group consisting of an antibody, a nanobody, a diabody, and a single chain variable fragment. In some embodiments, the antigen targeting moiety is a single chain or single domain antibody. In certain embodiments, the antigen targeting moiety is a single chain variable fragment.

[0153] In another embodiment, the antigen targeting moiety is selected from the group consisting of a monoclonal antibody, a recombinant antibody, a single chain antibody, a bispecific antibody, a nanobody, an antibody in which the heavy and light chains are connected by a flexible linker, an Fv molecule, an antigen-binding fragment, a Fab fragment, a Fab' fragment, an F(ab')2 molecule, a fully human antibody, a humanized antibody, and a chimeric antibody or a fragment or derivative thereof.

[0154] In some embodiments, the antigen targeting moiety specifically binds to an antigen as an antagonist (e.g., the antigen targeting moiety can inhibit binding of a ligand to its receptor), while in some embodiments, the antigen targeting moiety specifically binds to an antigen as an agonist (e.g., the antigen targeting moiety can induce signal transduction upon binding to a receptor).

[0155] In some embodiments, the antigen targeting moiety is selected from the group consisting of BTLA, OX40, LAG3, NRP1, VEGF, HER2, CEA, CD19, CD20, amyloid beta, HER3, IGF-1R, MUC1, EpCAM, CD22, VEGFR-2, PSMA, GM-CSF, CXCR4, CD30, CD70, FGFR2, BCMA, CD44, ICAM-1, Notch1, MHC, CD28, IL-1R1, TCR, N Specifically binds to an antigen selected from the group consisting of otch3, FGFR3, TGF-β, TGFBR1, TGFBR2, CD109, GITR, CD47, alpha-synuclein, CD26, LRP1, CD52, IL-4Rα, VAP-1, EPO receptor, integrin αv, TIM-3, Grp78, LIGHT, TLR2, TLR3, PAR-2, NRP2, GLP-1 receptor, hedgehog, and syndecan-1.

[0156] In one embodiment, the one or more drugs have a size of at most 100 kDa, such as at most 85 kDa, for example at most 75 kDa, such as at most 65 kDa, for example at most 55 kDa, such as at most 50 kDa, for example at most 40 kDa, such as at most 30 kDa, for example at least 10 kDa.

[0157] In one embodiment, the one or more drugs comprise at most 900 amino acids, such as at most 770 amino acids, for example at most 680 amino acids, such as at most 590 amino acids, for example at most 500 amino acids, such as at most 450 amino acids, for example at most 360 amino acids, such as at most 270 amino acids, for example at least 90 amino acids.

[0158] In one embodiment, the antigen targeting moiety is selected from the group consisting of anti-PD1, anti-PD-L1, anti-EGFR, anti-CTLA4, anti-CD137, anti-CD3, and anti-TNFα.

[0159] In one embodiment, the antigen targeting moiety is selected from the group consisting of atezolizumab, EgA1, ipilimumab, nivolumab, KN035, urelumab, foralumab, muromonab, and adalimumab, or a therapeutically active scFv, fragment or variant thereof comprising one or more CDRs, all three heavy chain CDRs, all three light chain CDRs, all three heavy chain CDRs and all three light chain CDRs, a heavy chain variable region, and / or a light chain variable region of any of the foregoing antigen targeting moieties.

[0160] In some embodiments, the one or more drugs are selected from the group consisting of ANB032, rosunilimab, LY3361237, enselimab, covolimab, imsidolimab, dostallimab, or a therapeutically active scFv, fragment or variant thereof comprising one or more CDRs, all three heavy chain CDRs, all three light chain CDRs, all three heavy chain CDRs and all three light chain CDRs, a heavy chain variable region, and / or a light chain variable region of any of the foregoing antigen targeting moieties.

[0161] As outlined above, cytokines may be used as drugs in the present invention. Cytokines are described as a category of small proteins that induce cell signaling.

[0162] In one embodiment, the one or more drugs are cytokines selected from the group consisting of chemokines, interferons, interleukins, lymphokines, and tumor necrosis factors.

[0163] In another embodiment, the one or more drugs are cytokines selected from the group consisting of IL1, IL1 alpha, IL1 beta, IL2, IL3, IL4, IL6, IL7, IL8, IL9, IL10, IL11, IL12, IL13, IL14, IL15, IL16, IL17, IL18, IL19, IL20, IL21, IL22, IL23, IL24, IL25, IL26, IL27, IL28, IL29, IL30, IL31, IL32, IL33, IL34, IL35, and IL36.

[0164] In a further embodiment, the one or more drugs are cytokines selected from the group consisting of IL2, IFN-α, IL-15, IL-21, IL-10, IL-12, IL-17, GM-CSF, TGF-β, CSF-1, insulin, GLP-1, HGH, VEGF, PDGF, BMP, EPO, G-CSF, IL-11, IFN-γ, and IFN-β.

[0165] In a preferred embodiment, the one or more drugs is IL2. IL2 is tested in Example 9.

[0166] In one embodiment, the antigen targeting moiety is encoded by an amino acid sequence selected from the group consisting of SEQ ID NOs: 27-43. In another embodiment, the antigen targeting moiety has or comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 27-43. In a further embodiment, the antigen targeting moiety has an amino acid sequence having at least about 80% sequence identity, such as at least about 85%, 90%, or even about 95% sequence identity, to a sequence selected from the group consisting of SEQ ID NOs: 27-43. When variations are introduced into the antigen targeting moiety, it is preferred that the CDR sequences are not altered.

[0167] In another embodiment, the nucleic acid sequence encoding the antigen targeting moiety is selected from the group consisting of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26, or fragments thereof having at least about 90% sequence identity to any of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26; in particular, about 95% identity to SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26. In another embodiment, the amino acid sequence is encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26 or a fragment thereof having at least about 90% sequence identity to any of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26; in particular, a fragment thereof having about 95% identity to SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26.

[0168] In further embodiments, the proteinaceous prodrug construct in accordance with the invention comprises 1 to 5, such as 1 to 4, such as 1 to 3, such as 1 to 2 drugs. In certain embodiments, the proteinaceous prodrug construct in accordance with the invention comprises one drug.

[0169] Byte Area As previously described, the unique protease trap inhibition mechanism of the proteinaceous prodrug construct (Figure 1) is initiated upon protease cleavage within the exposed and highly susceptible bait region.

[0170] In some embodiments, a proteinaceous prodrug construct according to the present invention comprises a CPAMD protein (e.g., A2M) with a modified bait region. In some embodiments, the bait region is modified to alter the selection of proteases that can cleave the bait region and trigger a conformational change in the CPAMD protein (e.g., A2M). For example, the bait region may be modified to be cleaved by a particular protease or class of proteases (e.g., MMPs such as MMP2).

[0171] The modification allows the construction of CPAMD proteins (e.g., A2M) that contain a bait region that does not have a protease cleavage site. The modification does not affect the structure and function of the CPAMD protein (e.g., A2M), but facilitates the inability of proteases to stimulate the structural changes of the CPAMD protein as seen in wild-type CPAMD proteins (e.g., A2M). A bait region that cannot be cleaved by a protease is referred to herein as a "tabular rassa bait region." A CPAMD protein (e.g., A2M) that contains a bait region that cannot be cleaved by a protease is referred to herein as a "tabular rassa" bait region.

[0172] In certain embodiments, at least one protease cleavage site is introduced into the tabular subunit region. The use of such a modified bait region allows control of which proteases can cleave and thereby introduce structural changes into the proteinaceous prodrug construct.

[0173] For example, to prevent the tabular subunit region from being cleaved by a protease, the tabular subunit region may comprise an engineered amino acid sequence that is flexible and / or hydrophilic. In some embodiments, the engineered amino acid sequence comprises a sequence of glycine, serine, alanine, threonine, and / or proline residues. In some embodiments, the engineered amino acid sequence replaces all or part of the wild-type bait region. In some embodiments, the engineered amino acid sequence is about 15-51 amino acids, such as about 30-40, such as about 31-39, such as about 32-35. In certain embodiments, the length of the engineered amino acid sequence is about 32-33 amino acids. In some embodiments, the engineered amino acid sequence replaces all of the wild-type bait region and has a length equal to the wild-type bait region.

[0174] In another embodiment, the tabular subite region is composed of a series of amino acid repeats to prevent the tabular subite region from being cleaved by proteases. The series of amino acid repeats may replace part or all of the native byte region. Thus, in one embodiment, the tabular subite region comprises a series of amino acid repeats. Examples of a series of triple amino acid repeats are Gly-Gly-Ser, Gly-Gly-Gly, Gly-Ser-Gly, Gly-Ser-Ser, Ser-Gly-Gly, Ser-Gly-Ser, Ser-Ser-Gly, and Ser-Ser-Ser.

[0175] Each series of three amino acids is repeated or combined with each other.

[0176] Thus, in one embodiment the tabular subunit region is composed of one or more amino acid repeats, the repeats being selected from the list consisting of Gly-Gly-Ser, Gly-Gly-Gly, Gly-Ser-Gly, Gly-Ser-Ser, Ser-Gly-Gly, Ser-Gly-Ser, Ser-Ser-Gly and Ser-Ser-Ser.

[0177] In another embodiment, the proteinaceous prodrug construct comprises a tabular subunit region composed of one or more amino acid repeats, the repeat being an amino acid triplet composed of Ser, Gly, and Ala residues.

[0178] In a further embodiment the tabular subunit region is composed of one or more amino acid repeats, the repeats being selected from the list consisting of Gly-Gly-Ser, Gly-Gly-Gly, Gly-Ser-Gly, Gly-Ser-Ser, Ser-Gly-Gly, Ser-Gly-Ser, Ser-Ser-Gly, Ser-Ser-Ser and Ala.

[0179] In another embodiment, the proteinaceous prodrug construct comprises a tabular subunit region composed of one or more amino acid repeats, the repeats being Gly-Gly-Ser, Gly-Gly-Gly, Gly-Gly-Ala, Gly-Ser-Gly, Gly-Ser-Ser, Gly-Ser-Ala, Gly-Ala-Ser, Gly-Ala-Gly, Gly-Ala-Ala, Ser-Gly-Gly, Ser-Gly-Ser, Ser- The amino acid sequence is selected from the list consisting of Gly-Ala, Ser-Ser-Gly, Ser-Ser-Ser, Ser-Ser-Ala, Ser-Ala-Gly, Ser-Ala-Ser, Ser-Ala-Ala, Ala-Gly-Ser, Ala-Gly-Gly, Ala-Gly-Ala, Ala-Ser-Gly, Ala-Ser-Ser, Ala-Ser-Ala, Ala-Ala-Ser, Ala-Ala-Gly and Ala-Ala-Ala.

[0180] In one embodiment, the byte region comprises 5, such as 7, such as 9, such as 11, such as 13, such as 15, such as 17 repeats. In one particular embodiment, the byte region comprises 13 repeats.

[0181] In another embodiment, the byte region comprises about 5-17, such as about 7-15, such as about 9-13 repeats.

[0182] The total length of the byte region can vary from 15 to 51 amino acids.

[0183] Thus, in one embodiment, the length of the tabular subunit region is about 15 to 51, such as about 30 to 40, such as about 31 to 39, such as about 32 to 35 amino acids. In a specific embodiment, the length of the tabular subunit region is about 32 to 33 amino acids.

[0184] A particular embodiment of the tabular subite region consists of 13 Gly-Gly-Ser-repeats and is found in SEQ ID NO: 124. Thus, in one embodiment, the tabular subite region is SEQ ID NO: 124.

[0185] Cutting site In order for the proteinaceous prodrug construct to be effective as a drug and to control the activity of the proteinaceous prodrug construct, individual protease cleavage sites can be introduced into the tabular subite region, thus allowing the skilled artisan to control which proteases can cleave and thereby introduce structural changes into the proteinaceous prodrug construct.

[0186] The present invention is not limited to introducing a single protease cleavage site. In some embodiments, the bait region can have several cleavage sites, which are cleaved by different proteases.

[0187] Thus, in one embodiment, the bait region comprises one or more protease cleavage sites (eg, two, three or four protease cleavage sites).

[0188] In another embodiment, the bait region contains only one protease cleavage site.

[0189] In some embodiments, the bait domain is activated protein C, ADAM10, ADAM12, ADAM15, ADAM17 / TACE, ADAM9, ADAMDEC1, ADAMTS1, ADAMTS4, ADAMTS5, BACE, BMP-1, caspase 1, caspase 10, caspase 14, caspase 2, caspase 3, caspase 4, caspase 5, caspase 6, caspase 7, caspase 8, caspase 9, cathepsin A , cathepsin B, cathepsin C, cathepsin D, cathepsin E, cathepsin G, cathepsin K, cathepsin L, cathepsin S, cathepsin V / L2, cathepsin X / Z / P, chymase, cruzipain, DESC1, DPP-4, elastase, FAP, granzyme B, guanidinobenzoatase, hepsin, HtrA1, neutrophil elastase, KLK10, KLK11, KLK13, KLK1 4, KLK4, KLK5, KLK6, KLK7, KLK8, lactoferrin, legumain, marapsin, matriptase-2, meprin, MMP1, MMP8, MMP10, MMP11, MMP12, MMP13, MMP14, MMP15, MMP16, MMP17, MMP19, MMP2, MMP20, MMP23, MMP24, MMP26, MMP27, MMP3, MMP7, MMP8, MMP9, MT-SP1 / It contains only one protease cleavage site that can be cleaved by a protease selected from the group consisting of matriptase, neprilysin, NS3 / 4A, Otubain-2, PACE4, plasmin, PSA, PSMA, renin, thrombin, TMPRSS2, TMPRSS3, TMPRSS4, tPA, tryptase, uPA, ADAM8, FVIIa, FIXa, Furin, Fxa, FXIa, FXIIa, and TAFI.

[0190] In a further embodiment, the byte region contains a single cleavable site selected from the group of SEQ ID NOs: 96-123.

[0191] In some embodiments, the bait region contains only one single protease cleavage site that can be cleaved by a matrix metalloprotease (MMP). In certain embodiments, the bait region contains only one single protease cleavage site that can be cleaved by a protease selected from the group consisting of MMP2, MMP9, MMP14, MMP1, MMP3, MMP13, MMP17, MMP11, MMP8, MMP10, and MMP19.

[0192] The bait region may also comprise two cleavage sites. Thus, in one embodiment, the bait region comprises two protease cleavage sites.

[0193] In another embodiment, the bait region contains exactly two cleavable sites, one of which is cleavable by the group of proteases consisting of MMP2, MMP9, MMP14, MMP1, MMP3, MMP13, MMP17, MMP11, MMP8, MMP10, and MMP19, and the other is cleavable by the group of proteases consisting of activated protein C, ADAM10, ADAM12, ADAM15, ADAM17 / TACE, ADAM16, ADAM17 / TACE, ADAM18, ADAM19, ADAM20, ADAM21, ADAM22, ADAM23, ADAM24, ADAM25, ADAM26, ADAM27, ADAM28, ADAM29, ADAM30, ADAM31, ADAM32, ADAM33, ADAM34, ADAM35, ADAM36, ADAM37, ADAM38, ADAM39, ADAM M9, ADAMDEC1, ADAMTS1, ADAMTS4, ADAMTS5, BACE, BMP-1, caspase 1, caspase 10, caspase 14, caspase 2, caspase 3, caspase 4, caspase 5, caspase 6, caspase 7, caspase 8, caspase 9, cathepsin A, cathepsin B, cathepsin C, cathepsin D, cathepsin E, cathepsin G, cathepsin K, cathepsin L, Cathepsin S, cathepsin V / L2, cathepsin X / Z / P, chymase, cruzipain, DESC1, DPP-4, elastase, FAP, granzyme B, guanidinobenzoatase, hepsin, HtrA1, neutrophil elastase, KLK10, KLK11, KLK13, KLK14, KLK4, KLK5, KLK6, KLK7, KLK8, lactoferrin, legumain, marapsin, matriptase- 2, it can be cleaved by a group of proteases consisting of meprin, MT-SP1 / matriptase, neprilysin, NS3 / 4A, otubein-2, PACE4, plasmin, PSA, PSMA, renin, thrombin, TMPRSS2, TMPRSS3, TMPRSS4, tPA, tryptase, uPA, ADAM8, FVIIa, FIXa, furin, Fxa, FXIa, FXIIa, and TAFI.

[0194] In another embodiment, the byte region comprises exactly two cleavable sites selected from the group of SEQ ID NOs: 96-123.

[0195] In further embodiments, the bait region is free of protease cleavage sites recognized by human proteases other than MMPs. In some embodiments, the bait region contains one or more (e.g., at least two or three) protease cleavage sites that can be cleaved by one or more (e.g., at least two or three) MMPs.

[0196] In yet a further embodiment, the bait region is free of protease cleavage sites recognized by human proteases except for a single cleavage site.

[0197] As can be seen by the examples, the bait region can be highly modified and the skilled artisan can select any suitable cleavage site into the bait region depending on the specificity required. Thus, in certain embodiments, the proteinaceous prodrug construct according to the invention comprises a CPAMD protein (e.g., A2M) that comprises a modified bait region that can be selectively cleaved by one or more proteases.

[0198] A protease site is "selectively cleavable" if cleavage occurs only or primarily in the presence of one particular protease. The modified bait region may be engineered to contain one or more (e.g., at least two or three) cleavage sites, each of which is "selectively cleavable" by a different protease. For example, the modified bait region may be engineered to contain one or two or three unique recognition sites, each of which is specific for a different protease.

[0199] Exemplary MMP cleavage sites include A21A, B74, C9 and S1. In certain embodiments, the bait region includes one or more (e.g., at least two or three) of the A21A, B74, C9 and / or S1 cleavage sites. Exemplary modified bait regions that include such cleavage sites can be found in SEQ ID NOs: 126-133. In another specific embodiment, the bait region includes a lysine, such as in SEQ ID NO: 125.

[0200] In some embodiments, the modified bait region comprises an engineered amino acid sequence that is flexible and / or hydrophilic. In some embodiments, the engineered amino acid sequence comprises a sequence of glycine, serine, alanine, threonine, and / or proline residues. In some embodiments, the engineered amino acid sequence comprises a combination of glycine, serine, and / or alanine residues. In some embodiments, the engineered amino acid sequence replaces the wild-type bait region and has a length equal to the wild-type bait region.

[0201] In one embodiment, the wild-type bait region is replaced by a combination of glycine, serine, and / or alanine residues having a length equivalent to the wild-type bait region.

[0202] Exemplary sequences in which a cleavage site is inserted into the tabular rasa region can be found in any of the sequences identified by SEQ ID NOs: 125-133.

[0203] In another embodiment, only a portion of the wild-type byte region is replaced by the described tabular rasa region, such as in SEQ ID NO: 130, in which the C-terminal quarter of the wild-type byte region is retained.

[0204] In another embodiment, one or more of the cleavage sites in the bait region are replaced with a combination of glycine, serine, and / or alanine residues.

[0205] In one embodiment, the byte region comprises one or more repeats, such as at least 5, such as at least 6, such as at least 7, such as at least 8. In a particular embodiment, the length of the tabular subabyte region is at least about 10 repeats.

[0206] In one embodiment, the byte region has a size of about 8 kDa, e.g., up to about 5 kDa, e.g., up to about 4 kDa, e.g., up to about 3 kDa, e.g., up to about 2 kDa. In a particular embodiment, the byte region has a size of up to about 2.5 kDa.

[0207] In one embodiment, the length of the bait region is about 15-51 amino acids. In one embodiment, the length of the bait region is about 30-40 amino acids, for example, about 31-39 amino acids or 32-35 amino acids. In a specific embodiment, the total length of the bait region is about 32-33 amino acids.

[0208] In one embodiment, the bait region comprises an engineered amino acid sequence that is generally flexible and / or hydrophilic, e.g., a random sequence of glycine, serine, alanine, threonine, and / or proline residues, and optionally one or more protease cleavage sites (e.g., MMP cleavage sites) such that the total length of the bioregion, including the repeats and cleavage site(s), is about 15-51 amino acids, e.g., about 32-33 amino acids.

[0209] In one embodiment, once the protease cleaves the "bait region", the protease becomes trapped inside the proteinaceous prodrug construct.

[0210] RBD domain As explained above, prodrugs are created by contacting a drug (e.g., a therapeutic peptide, polypeptide, or protein) with the RBD domain such that the RBD domain folds and masks the drug, rendering it inaccessible. A therapeutic protein may be contacted with the RBD domain by inserting it into the RBD domain or by replacing a portion of the RBD domain with the therapeutic protein.

[0211] Thus, in an exemplary embodiment of a proteinaceous prodrug construct of the invention, a drug (e.g., a therapeutic peptide, polypeptide or protein) is positioned within the interior of the RBD such that the CPAMD protein (e.g., A2M) can alter its structure upon proteolytic cleavage of a protease cleavage site contained within the bait region, thereby making the drug accessible.

[0212] Considering the size of the RBD domain, there are numerous suitable sites for insertion into the RBD domain. As visualized in FIG. 13, the RBD domain is largely composed of beta sheets, and as shown in the examples of the present invention, the loops in the middle of each beta strand are suitable for drug insertion. For example, in the native human A2M protein, loop 1 is formed by amino acid residues 1368-1379, loop 2 by amino acid residues 1392-1404, loop 3 by amino acid residues 1420-1426, and loop 4 by amino acid residues 1450-1457.

[0213] In one embodiment, the drug is positioned within loop 2 in the RBD domain of A2M (between residues 1391 and 1405, e.g., between residues 1392 and 1404 of native human A2M). In one embodiment, the drug is positioned in the RBD domain of A2M by replacing one or more amino acids corresponding to region-forming residues 1391-1405, or residues 1392-1404, of the native human protein. In one embodiment, the drug is positioned in the RBD domain of A2M between amino acids corresponding to residues 1391-1405 (e.g., residues 1392-1404) of the native human protein. In another embodiment, one or more of the amino acids corresponding to residues 1391, 1392, 1393, 1394, 1395, 1396, 1397, 1398, 1399, 1400, 1401, 1402, 1403, 1404, and / or 1405 of the native human protein are replaced with a drug. In another embodiment, a drug is positioned after one or more of the amino acids corresponding to residues 1391, 1392, 1393, 1394, 1395, 1396, 1397, 1398, 1399, 1400, 1401, 1402, 1403, or 1404 of the native human protein.

[0214] In one embodiment, the drug is positioned within loop 1 in the RBD domain of A2M (at a position between residues 1368-1379 of native human A2M). In one embodiment, one or more of the amino acids corresponding to residues 1368, 1369, 1370, 1371, 1372, 1373, 1374, 1375, 1376, 1377, and / or 1378 of native human A2M are replaced with the drug. In another embodiment, the drug is positioned after one or more of the amino acids corresponding to residues 1368, 1369, 1370, 1371, 1372, 1373, 1374, 1375, 1376, 1377, or 1378 of native human A2M.

[0215] In one embodiment, the drug is positioned within loop 3 in the RBD domain of A2M (at a position between residues 1420-1426 of native human A2M). In another embodiment, one or more of the amino acids corresponding to residues 1420, 1421, 1422, 1423, and / or 1424 of native human A2M are replaced with the drug. In another embodiment, the drug is positioned after one or more of the amino acids corresponding to residues 1420, 1421, 1422, 1423, or 1424 of native human A2M.

[0216] In another embodiment, the drug is positioned in the vicinity of the RBD domain of A2M, hi one embodiment, the drug is tethered to the C-terminus of the RBD domain of A2M and brought into close proximity of residues 1391-1405 of the RBD domain through specific interactions, such as coiled-coil interactions between alpha helices.

[0217] Although the placement of one or more drugs within the RBD domain is described in the preceding paragraphs with respect to A2M, one of skill in the art of proteinaceous prodrug constructs will recognize that other CPAMD proteins can be substituted for A2M and the corresponding residues in these CPAMD proteins can be identified for the purposes of practicing the present invention (e.g., using the residue numbers provided in Table 1 as a guide).

[0218] The inventors have found that proteinaceous prodrug constructs in which a drug (e.g., a therapeutic peptide, polypeptide or protein) is placed within loops 2 or 4 of the RBD domain of the CPAMD protein (e.g., by replacing one or more residues or by direct insertion) can be successfully expressed at high levels (see, e.g., proteinaceous fusion constructs referred to herein as "ciRBD" and "miRBD"). For example, insertion of the drug between amino acids corresponding to residues 1402 and 1403 of native human A2M has been found to be particularly advantageous. Replacement of amino acids corresponding to residues 1393-1395 of native human A2M with the drug may be similarly advantageous.

[0219] Linker A linker can be used to insert the drug into the proteinaceous prodrug construct. Any suitable linker can be used. In some embodiments, the linker is (GGGGS)n (SEQ ID NO: 223) or (GGS)n. In some embodiments, n=1, 2, 3, 4, 5, or 6.

[0220] Exemplary Proteinaceous Fusion Constructs In one embodiment, an exemplary proteinaceous fusion construct according to the invention is encoded by an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, or SEQ ID NO:25. In one embodiment, the proteinaceous fusion construct is composed of an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, and SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, and SEQ ID NO:25.

[0221] In another embodiment, the proteinaceous fusion construct has at least about 80% sequence identity, such as at least about 85% sequence identity, about 90% sequence identity, or even about 95% sequence identity, to a sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, and SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, and SEQ ID NO:25.

[0222] In one embodiment, the amino acid sequence is encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26; or a fragment thereof having at least about 90% sequence identity to any one of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26, in particular about 95% identity to any one of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26. In one embodiment, the amino acid sequence is encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26; or a fragment thereof having at least about 90% sequence identity to any one of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26, in particular about 95% identity to any one of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26.

[0223] Exemplary Nucleic Acids In one aspect, the present invention relates to a nucleic acid encoding a proteinaceous fusion construct according to the invention.

[0224] In one embodiment, the nucleic acid according to the invention encodes a proteinaceous fusion construct according to any one of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, or SEQ ID NO:25.

[0225] In another embodiment, the nucleic acid sequence is selected from the group consisting of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26: or a fragment thereof having at least about 90% sequence identity to any one of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26, in particular about 95% identity to any one of SEQ ID NOs: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, and 26. In another embodiment, the nucleic acid sequence is selected from the group consisting of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26; or a fragment thereof having at least about 90% sequence identity to any one of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26, in particular about 95% identity to any one of SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, and SEQ ID NO:26.

[0226] vector In order for the proteinaceous fusion construct to be expressed, the nucleic acid according to the invention is or can be inserted into an expression vector, which is usually a plasmid or virus designed to control gene expression in cells. The vector is engineered to contain regulatory sequences that act as enhancers or promoters for efficient expression of the desired coding sequence carried by the vector. A non-limiting example provides the use of a naked circular plasmid that contains the essential functions required for expression, including a promoter, a coding sequence of interest, and a polyadenylation signal.

[0227] Additionally, to allow for easy production that may be performed using E. coli, the plasmid contains a selection marker, allowing bacterial production with or without traditional bacterial resistance selection.

[0228] In another embodiment, the present invention relates to a vector comprising a nucleic acid according to the present invention.

[0229] In one embodiment, the nucleic acid encoding the proteinaceous fusion construct is operably linked to a promoter and, optionally, further to regulatory sequences that regulate the expression of said nucleic acid.

[0230] In one embodiment, the vector is a eukaryotic expression vector, in particular a mammalian, e.g., human, expression vector.

[0231] In one embodiment, the vector is selected from the group consisting of a plasmid, a cosmid, a phage, a bacterial artificial chromosome (BAC), a phagemid, and a P1-derived artificial chromosome.

[0232] In one embodiment, the vector is a plasmid.

[0233] In one embodiment, said plasmid is selected from the group consisting of a TA cloning vector, a Gateway cloning vector, a restriction cloning vector, a Topo cloning vector, a pET vector system, and a pBAD vector system.

[0234] host cell The vector according to the invention is or can be inserted into a host cell for the expression of the proteinaceous fusion construct according to the invention.

[0235] In one aspect, the present invention relates to a host cell comprising a vector according to the invention.

[0236] The cell can be a prokaryotic cell, such as a bacterium, or a eukaryotic cell.

[0237] In one embodiment, the host cell is selected from the group consisting of bacteria and eukaryotes; typically, the host cell is eukaryotic.

[0238] In another embodiment, the host cell is yeast.

[0239] In typical embodiments, the host cell is a mammalian cell, such as a CHO (Chinese Hamster) cell.

[0240] In one embodiment, the host cell is human.

[0241] In another embodiment, the host cell is or is derived from a HEK293 cell line.

[0242] composition A further aspect of the present disclosure relates to a composition comprising a proteinaceous prodrug construct as described herein. The composition may also comprise a nucleic acid, vector or host cell as described herein.

[0243] In one embodiment of the present disclosure, the composition comprises a pharma- ceutically acceptable carrier. Such a composition may also be referred to as a pharmaceutical composition.

[0244] therapeutic use The proteinaceous fusion constructs according to the invention can be used in the treatment of disease. In a further aspect, the compositions, nucleic acids, vectors or host cells described herein can be used in the treatment of disease. In one aspect, the invention relates to a proteinaceous prodrug construct, for example, for use in therapy as a drug. In a further aspect, the invention relates to a composition, nucleic acid, vector or host cell described herein, for use in therapy as a drug.

[0245] In some embodiments, the proteinaceous prodrug constructs according to the present invention are intended for use in treating diseases or disorders of the nervous system, eyes, circulatory system, respiratory system, digestive system, or skin. In some embodiments, the disease or disorder is a neoplasm, a blood disorder, a metabolic disorder, an autoimmune disease, an immunodeficiency, or an infectious disease. In some embodiments, the neoplasm is a cancer selected from brain cancer, glioblastoma, lung cancer, colorectal cancer, skin cancer, malignant melanoma, pancreatic cancer, bladder cancer, liver cancer, breast cancer, eye cancer, and prostate cancer, the cancer is a hematological cancer such as selected from the group consisting of multiple myeloma, acute myeloblastic leukemia, chronic myelogenous leukemia, acute lymphocytic leukemia, and chronic lymphocytic leukemia, or the cancer is malignant melanoma, breast cancer, non-small cell lung cancer, pancreatic cancer, head and neck cancer, liver cancer, sarcoma, and B-cell lymphoma. In some embodiments, the autoimmune disease is selected from arthritis (eg, rheumatoid arthritis or psoriatic arthritis), multiple sclerosis, systemic lupus erythematosus, and inflammatory bowel disease.

[0246] In one embodiment, the proteinaceous prodrug construct according to the invention is intended for use in the treatment of cancer. In another embodiment, the proteinaceous prodrug construct according to the invention is intended for use in the treatment of arthritis. In a further embodiment, the composition, nucleic acid, vector or host cell according to the invention is intended for use in the treatment of cancer. In yet a further embodiment, the composition, nucleic acid, vector or host cell according to the invention is intended for use in the treatment of arthritis.

[0247] The proteinaceous prodrug constructs, compositions, nucleic acids, vectors or host cells described herein can also be used in a method of treatment.Accordingly, in another aspect, the present disclosure relates to a method of treatment, comprising administering a therapeutic amount of the proteinaceous prodrug constructs, compositions, nucleic acids, vectors or host cells described herein to a subject in need thereof.The subject in need thereof may be a subject suffering from cancer or arthritis.

[0248] In one embodiment, the cancer is a solid tumor. In some embodiments, the cancer is selected from the list consisting of brain cancer, glioblastoma, lung cancer, colorectal cancer, skin cancer, malignant melanoma, pancreatic cancer, bladder cancer, liver cancer, breast cancer, eye cancer, and prostate cancer.

[0249] In another embodiment, the cancer is a hematological cancer such as selected from the group consisting of multiple myeloma, acute myeloblastic leukemia, chronic myelogenous leukemia, acute lymphocytic leukemia, and chronic lymphocytic leukemia.

[0250] In further embodiments, the cancer is malignant melanoma, breast cancer, non-small cell lung cancer, pancreatic cancer, head and neck cancer, liver cancer, sarcoma, or B-cell lymphoma.

[0251] In some embodiments, the proteinaceous prodrug construct according to the present invention comprises a CPAMD protein (e.g., A2M) with a modified bait region. In some embodiments, the bait region is modified to alter the selection of proteases that can cleave the bait region and trigger a conformational change in the CPAMD protein (e.g., A2M). For example, the bait region is modified to be cleaved by a particular protease or class of proteases (e.g., MMPs such as MMP2).

[0252] In one embodiment, the cancer expresses one or more proteases that are specific for cleavage sites in the bait region of the CPAMD protein (e.g., A2M). In certain embodiments, the proteinaceous prodrug constructs according to the invention comprise a CPAMD protein (e.g., A2M) that contains a modified bait region that can be selectively cleaved by one or more proteases expressed by the cancer.

[0253] In one embodiment, the cancer is a cancer of the type 1 or type 2 that is a result of activation of protein C, ADAM10, ADAM12, ADAM15, ADAM17 / TACE, ADAM9, ADAMDEC1, ADAMTS1, ADAMTS4, ADAMTS5, BACE, BMP-1, caspase 1, caspase 10, caspase 14, caspase 2, caspase 3, caspase 4, caspase 5, caspase 6, caspase 7, caspase 8, caspase 9, Cathepsin A, cathepsin B, cathepsin C, cathepsin D, cathepsin E, cathepsin G, cathepsin K, cathepsin L, cathepsin S, cathepsin V / L2, cathepsin X / Z / P, chymase, cruzipain, DESC1, DPP-4, elastase, FAP, granzyme B, guanidinobenzoatase, hepsin, HtrA1, neutrophil elastase, KLK10, KLK11, KLK13, KLK14 , KLK4, KLK5, KLK6, KLK7, KLK8, lactoferrin, legumain, marapsin, matriptase-2, meprin, MMP1, MMP8, MMP10, MMP11, MMP12, MMP13, MMP14, MMP15, MMP16, MMP17, MMP19, MMP2, MMP20, MMP23, MMP24, MMP26, MMP27, MMP3, MMP7, MMP8, MMP9, MT-S The cells express one or more proteases selected from the list consisting of P1 / matriptase, neprilysin, NS3 / 4A, otubein-2, PACE4, plasmin, PSA, PSMA, renin, thrombin, TMPRSS2, TMPRSS3, TMPRSS4, tPA, tryptase, uPA, ADAM8, FVIIa, FIXa, furin, Fxa, FXIa, FXIIa, and TAFI.

[0254] Subjects and Administration A "subject" as used herein includes humans of any age, other primates (e.g., cynomolgus monkeys, rhesus monkeys); mammals in general, including commercially relevant mammals such as cows, pigs, horses, sheep, goats, mink, ferrets, hamsters, cats, dogs; and / or birds. In typical embodiments, the subject is a human.

[0255] The term "subject" also includes healthy subjects of the population, particularly healthy subjects who are exposed to pathogens and in need of protection against infection, such as health care workers.

[0256] Furthermore, pathogenic infections caused by respiratory viruses can be particularly severe in elderly and frail patients and in patients with chronic or congenital dysfunction of the respiratory system, such as asthma, cystic fibrosis, or chronic obstructive pulmonary disease (COPD).

[0257] Thus, in an embodiment of the invention, the subject is selected from the group consisting of humans of all ages, other primates (e.g., cynomolgus monkeys, rhesus monkeys); mammals in general, including commercially relevant mammals such as cows, pigs, horses, sheep, goats, mink, ferrets, hamsters, cats and dogs, and birds.

[0258] In certain embodiments, the subject is a human.

[0259] Methods for generating proteinaceous fusion constructs In one aspect, the present invention provides a method for producing a proteinaceous fusion construct according to the present invention, comprising the steps of: Inserting an expression vector according to the invention into a host cell growing the host cell under conditions that permit expression of the proteinaceous fusion construct from the vector; and Purifying proteinaceous fusion construct expression The present invention relates to a method comprising the steps of:

[0260] Numbered embodiments The present invention will now be further described with reference to the following numbered embodiments: 1. A proteinaceous fusion construct comprising alpha-2-macroglobulin (A2M) fused to one or more drugs; or a modified A2M fused to one or more drugs; wherein the one or more drugs are positioned within or near the RBD domain of A2M. 2. A proteinaceous fusion construct comprising alpha-2-macroglobulin (A2M) containing a bait region having at least one protease cleavage site, said A2M fused to a peptide drug, such as one or more drugs located within residues 1392-1404, 1368-1379, or 1420-1426 of the receptor binding domain (RBD) of A2M. 3.a. One or more drugs are inaccessible if the bite region in alpha-2-macroglobulin (A2M) is not proteolytically cleaved; b. One or more drugs are accessible when the bite region in alpha-2-macroglobulin (A2M) is proteolytically cleaved; 3. A proteinaceous fusion construct according to embodiment 1 or 2. 4. The proteinaceous fusion construct of any one of embodiments 1 to 3, wherein the one or more drugs are selected from the group consisting of antigen targeting moieties, cytokines, extracellular domains of cell surface receptors, extracellular domains of cell surface ligands, and / or receptor agonists. 5. A proteinaceous fusion construct according to any one of embodiments 1 or 3-4, wherein the bait region comprises one or more protease cleavage sites. 6. A proteinaceous fusion construct according to any of embodiments 1 to 5, wherein the bait region is free of protease cleavage sites recognized by human proteases except for a single cleavage site. 7. A proteinaceous fusion construct according to any of the preceding embodiments, wherein one or more cleavage sites in the bait region are replaced by a combination of glycine, serine, and / or alanine residues. 8. The proteinaceous fusion construct of any of embodiments 1 or 3-7, wherein the drug is positioned within the RBD domain of A2M at a position between residues 1335 and 1474, or the drug is positioned in spatial proximity to the RBD domain of A2M. 9. The proteinaceous fusion construct according to any of the preceding embodiments, wherein the proteinaceous fusion construct is encoded by or is an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, and SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, or SEQ ID NO:25. 10. A proteinaceous fusion construct according to any one of embodiments 1 to 9, wherein the A2M molecule is a mammalian A2M molecule or a mutant thereof, such as a human A2M molecule. 11. A nucleic acid encoding a proteinaceous fusion construct according to any of embodiments 1 to 10. 12. A vector comprising the nucleic acid of embodiment 10. 13. The vector according to embodiment 12, wherein the nucleic acid encoding the proteinaceous fusion construct is operably linked to a promoter and, optionally, further to a regulatory sequence that regulates the expression of said nucleic acid. 14. A host cell comprising a vector according to any of embodiments 12-13, preferably wherein the host cell is selected from the group consisting of bacteria and eukaryotes. 15. A proteinaceous fusion construct according to any of embodiments 1 to 10 for use as a medicament. 16. introducing into a host cell according to embodiment 14 or into any suitable host cell an expression vector according to any one of embodiments 12 to 13; growing the host cell under conditions that allow expression of the proteinaceous fusion construct from the vector; and purifying the proteinaceous fusion construct; 16. A method for producing a proteinaceous fusion construct according to any one of embodiments 1 to 15, comprising:

[0261] Equivalent Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. References cited herein are not admitted to be prior art to the claimed invention. Furthermore, the materials, methods, and examples are illustrative only and are not intended to be limiting.

[0262] Working Example The invention will now be described in further detail in the following non-limiting examples. EXAMPLES

[0263] SUMMARY OF THE PRESENT APPLICATION This paper presents the overall design and mechanism of the present invention, which relates to a technique for generating protease-activated prodrug versions of biopharmaceuticals. With reference to FIG. 1A, a proteinaceous prodrug construct (1) comprises a CPAMD protein, e.g., human alpha-2-macroglobulin (A2M) (2), fused to one or more drugs (3), such that the accessibility of the drug is dependent on the conformational state of the CPAMD protein (e.g., A2M) (2). The CPAMD protein (e.g., A2M) (2) is converted from an initial "native" conformation to an "activated" conformation by one or more proteases (4). The drug (3) can be genetically fused to the CPAMD protein (e.g., A2M) (2) at a position where the drug is inaccessible to its therapeutic target in the "native" conformation (I) of the CPAMD protein (e.g., A2M) (2), but is accessible in the "activated" conformation (II) of the CPAMD protein (e.g., A2M) (2). In this manner, the activity of one or more drugs (3) is spatially restricted to tissues that are proteolytically competent and in which one or more proteases (4) capable of activating the CPAMD protein (e.g., A2M) (2) are present. Because the CPAMD protein (e.g., A2M) (2) can be engineered to be activated by one or more designated proteases (4), this technology allows for the targeting of drugs to tissues expressing disease-associated proteases, e.g., diseased tissues, thereby potentially improving drug efficacy while minimizing side effects resulting from targeted binding to healthy tissues. EXAMPLES

[0264] Generation of A2M and antibody proteinaceous fusion constructs the goal This data demonstrates the expression and purification of the A2M-antibody construct as a correctly folded tetrameric protein, with A2M adopting a functional native conformation with a thiol ester.

[0265] material and method Expression and purification of A2M-antibody fusion constructs The nucleotide sequences encoding the A2M-antibody fusion constructs and the corresponding amino acid sequences are provided (SEQ ID NOs:5-22). Proteinaceous fusion constructs were expressed in HEK293 FreeStyle cells using standard transient transfection protocols. Briefly, 25 kDa linear polyethylenimine (Polysciences) and plasmid DNA were incubated in antibiotic-free FreeStyle medium (Thermo Fisher Scientific) at a 4:1 w / w PEI to DNA ratio for 10 min and then slowly dripped into cell cultures at a density of 1 million cells per mL to a final DNA concentration of 1 μg per mL culture. After 4 days, cells were spun down at 1500×g and the supernatant was harvested by adding pH 7.4 HEPES to a final concentration of 50 mM.

[0266] Purification of the construct was performed using an established protocol for purifying A2M. The supernatant was first purified using Zn 2+ The A2M was run through a supported chelating HiTrap column (GE Healthcare) and eluted with 50 mM EDTA, 150 mM NaCl, 100 mM sodium acetate, pH 7.4. The EDTA eluent was dialyzed against 20 mM HEPES, pH 7.4, then loaded onto a HiTrap Q column (GE Healthcare) and eluted with a gradient of 0-400 mM NaCl (at pH 7.4 with a constant 20 mM HEPES). Fractions containing A2M were pooled, concentrated by ultrafiltration, and purified by size-exclusion chromatography on a Sephacryl S-300 HR (GE Healthcare) using a running buffer of 20 mM HEPES, 150 mM NaCl, pH 7.4 (HEPES-buffered saline, HBS).

[0267] SDS-PAGE and pore-restricted native PAGE Native pore-restricted PAGE was performed as previously described ( 36 ) using homemade gels in TBE buffer (89 mM Tris, 89 mM boric acid, 2 mM EDTA) with an acrylamide gradient of 5–10% for A2M analysis and 10–15% for C3 analysis. Pore-restricted electrophoresis gels were run overnight at 100 V in TBE buffer. Denaturing SDS-PAGE was performed on homemade 5–15% acrylamide gradient gels using a discontinuous 2-amino-2-methyl-1,3-propanediol and glycine buffer system. Samples were reduced with 25 mM DTT for 5 min at 95°C.

[0268] Reaction of A2M with methylamines and proteases To aminolyze the thiol ester of A2M, methylamine (pH 8) was added to 250 mM and incubated for 16 h at 37° C. To assess cleavage of A2M by thermolysin, thermolysin was added to a 2.2 to 1 mole / mol ratio of protease to A2M and incubated for 5 min at 37° C. The digestion was then inhibited using EDTA (10 mM, 15 min, room temperature).

[0269] result Proteinaceous fusion constructs were produced in transient HEK293F transfections at yields of several mg / L. After purification, the constructs migrated as native homotetramers in native PAGE (Figure 2A) and as approximately 190 kDa monomeric subunits in reducing, denaturing SDS-PAGE (Figure 2B). The presence of thiol esters in the constructs was confirmed by the presence of characteristic heat-induced fragmentation at the site of the thiol ester, yielding visible Nt and Ct autolysis fragments in SDS-PAGE (Figure 2B-C). These Nt and Ct autolysis fragments disappeared when the thiol esters were aminolyzed with methylamine prior to SDS-PAGE analysis. Proteolytic processing of the bait region was assessed by treatment with thermolysin. The bait region of the constructs was preferentially cleaved by thermolysin, resulting in the formation of Nt and Ct cleavage fragments (Figure 2B-C). Bite region cleavage induced a conformational change in the construct that increased its migration in native PAGE, but not to the same extent as wild-type A2M (Figure 2A); this is because the exposed antibody fragment increases the electrophoretic resistance experienced by the activated A2M-antibody construct.

[0270] conclusion Proteinaceous fusion constructs of A2M and antibody scFv are produced as homotetramers, in which the A2M component adopts a native conformation, forms a thiol ester, and is preferentially cleaved by proteases at its bait region, making it functionally intact. EXAMPLES

[0271] Structural dependence of binding in biolayer interferometry This example shows how conformational changes in proteinaceous fusion constructs can control the activity of drugs. In the native state, the drug is not exposed and is therefore inactive. In the active state, the drug is exposed and can interact with its target.

[0272] the purpose To determine the antigen-binding capacity of A2M-antibody fusion constructs in binding experiments using purified antigen immobilized on a biosensor, and to determine the extent to which this antigen-binding capacity is affected by the structure of A2M.

[0273] material and method Proteins used in binding studies Antigens for the antibodies under investigation were recombinantly expressed in HEK293F cells using standard transient transfection protocols (see Example 1). Antigens were expressed together with the leader peptide of A2M, an N-terminal StrepII tag, and a C-terminal Fc region from human IgG1 (uniprot ID P01857, residues 100-330, SEQ ID NO:40). The residues included for each antigen, using numbering before removal of the signal peptide, were as follows: EGFR (uniprot ID P00533, residues 25-645, SEQ ID NO: 37) PD-L1 (uniprot ID Q9NZQ7, residues 19-239, SEQ ID NO: 38) PD-1 (uniprot ID Q15116, residues 26-150 with Cys93Ser mutation, SEQ ID NO: 39) CTLA-4 (uniprot ID P16410, residues 36-161, SEQ ID NO: 40) CD3γε (uniprot ID P09693, residues 23-103 of the γ chain followed by a 26 residue glycine-serine linker and uniprot ID P07766, residues 23-118 of the ε chain, SEQ ID NO: 41) 4-1BB (uniprot ID Q07011, residues 24-186, SEQ ID NO:42)

[0274] The final sequences of these expressed fused antigens are given as both amino acid and nucleotide sequences (SEQ ID NOs: 45-58). An additional antigen, TNFα (uniprot P01375, residues 77-233), was expressed as a StrepII-tagged protein but without the C-terminal Fc region (SEQ ID NOs: 59, 60). This antigen was also purified by StrepTactin affinity chromatography and size-exclusion chromatography on Superdex 200 Increase to isolate TNFα trimers.

[0275] Supernatants containing the expressed antigens were purified using StrepTactin affinity chromatography (Iba Life Sciences) followed by size-exclusion chromatography on a Superdex 200 Increase (GE Healthcare). A2M-antibody fusion constructs were made as described in Example 1. Where stated, native A2M-antibodies were purified by affinity depletion of preactivated A2M; for further details see Example 5. The amino acid and nucleotide sequences of the A2M-antibodies are provided (SEQ ID NOs: 5-22).

[0276] Reaction of A2M-antibody with methylamine and proteases When A2M-antibody was treated with methylamine, 200 mM methylamine (pH 8) was added to A2M-antibody and incubated for 16 h at 37° C. When A2M-antibody was treated with thermolysin, thermolysin from Geobacillus stearothermophilus (Sigma-Aldrich) was added to A2M-antibody at a 2.2:1 molar ratio of protease to A2M and incubated for 5 min at 37° C. after which time thermolysin was inhibited by the addition of 25 mM EDTA.

[0277] Biolayer Interferometry HEPES-buffered saline (HBS; 20 mM HEPES, 150 mM NaCl, pH 7.4) was used as the buffer in all biolayer interferometry experiments. Antigen was immobilized on an anti-human Fc capture biosensor (AHC biosensor; Fortebio) at 30 nM in HBS for 20 min. A2M-antibody fusion constructs were then incubated with the antigen-coated biosensor at various concentrations to measure association, followed by dissociation in HBS. Where stated, A2M-antibody fusion constructs were activated by methylamine or protease treatment using the same methods as in Example 1.

[0278] result The conformational dependence of antigen binding by eight different A2M-antibodies was evaluated by biolayer interferometry. Antigens were expressed as fusion proteins with human IgG1 Fc regions, and the antigens were immobilized on the biosensor surface using an anti-human Fc capture biosensor in a standardized manner. The A2M-antibodies were then allowed to associate with their immobilized antigens, either without any treatment of the A2M-antibodies or by induction of conformational changes in A2M using methylamine aminolysis and / or proteolysis with thermolysin. In some cases, the A2M-antibodies were enriched for the native conformation of A2M by affinity depletion using antigen (PD-L1) or LRP1 resins, as described in the figure legends and detailed in Example 4.

[0279] For all examined antibodies, antigen binding was strongly dependent on the structure of A2M (Figure 3A-I), with thermolysin proteolysis of A2M consistently giving the highest binding response. Methylamine treatment produced variable binding responses; in some cases, methylamine induced binding responses similar to proteolysis (Figure 3B, 3I), and in other cases, methylamine produced intermediate responses (Figure 3C, 3F-H) or negligible responses (Figure 3D). When the native structure of A2M-antibody was enriched by affinity depletion, there was little or no antigen binding detected in the native samples without methylamine / proteolysis (Figure 3A-D, 3F).

[0280] conclusion Antibodies incorporated into A2M fusion constructs retain the ability to bind their cognate antigen. This antigen binding is determined by the structure of A2M, which has little or no antigen binding in its native conformation. Activation of A2M by proteolytic cleavage greatly increased antigen binding, and activation by methylamine treatment varied depending on the A2M-antibody in question. EXAMPLES

[0281] Enrichment of native A2M-antibody constructs by affinity depletion This example shows how modification of the proteinaceous fusion construct can be used to control where the drug is exposed. Depending on the cleavage site, the drug will only be exposed where a protease that recognizes that cleavage site is present. When a particular protease is present and cleaves the cleavage site, the structure of the proteinaceous fusion construct changes from "native" to "active."

[0282] the purpose Recombinantly expressed A2M-antibody fusion constructs are not only produced in their native conformation; a minor component is produced in a pre-activated state. Here, we investigate whether this pre-activated component can be removed by affinity depletion using the antibody's cognate antigen, the activating A2M receptor LRP1, or kappa light chain binding protein L.

[0283] material and method Proteins used The A2M-antibody was produced as described in Example 1. Recombinant LRP1 (residues 20-974, SEQ ID NOs: 63-64) was produced as a StrepII-tagged fusion protein with the human IgG1 Fc region as described for the antigen in Example 2.

[0284] resin preparation LRP1-coated resin was prepared using amine-reactive chemistry. A total of 200 mg of NHS-activated agarose (Pierce) and 600 μg of recombinant LRP1 in 0.15 M triethylammonium bicarbonate, 0.15 M HEPES, pH 8.3 were mixed on a rotating plate for 2 h at room temperature. Following incubation, the resin was washed twice in HBS and the reaction was quenched with 50 mM Tris-HCl, pH 8 for 20 min followed by a final wash step with HBS. PD-L1-coated resin was prepared as described for LRP1. Protein L-coated agarose was purchased from Pierce (Thermo Scientific).

[0285] Affinity depletion To deplete pre-activated A2M, A2M-antibody fusion constructs at up to 2 mg / mL in HBS were incubated with the resin overnight at room temperature with shaking using a helicopter rotor. For LRP1-based depletion, 10 mM CaCl2 was added to HBS. After overnight incubation, the supernatant was collected and the resin was regenerated using acidic elution with HBS with 25 mM EDTA for LRP1 or with pH 2.7, 10 mM KH2PO4 buffer for PD-L1 and Protein L. The collected supernatants were tested using Biolayer Interferometry as described in Example 2.

[0286] result A2M-atezolizumab was incubated with resin coated with its cognate antigen, PD-L1. A single round of depletion was performed. The binding of A2M-atezolizumab to PD-L1 before and after this depletion was then assessed using biolayer interferometry. A2M-atezolizumab from pre- and post-depletion bound similarly to PD-L1 upon methylamine treatment, whereas antigen binding by untreated samples after depletion was significantly reduced compared to untreated samples before depletion, indicating that PD-L1 depletion enriched the content of A2M-Ab with inaccessible antibodies (Figure 4A). A2M-ipilimumab, A2M-nivolumab, and A2M-urelumab were incubated with resin coated with LRP1, a receptor that specifically binds activated A2M but not native A2M. Three rounds of depletion were performed for each A2M-antibody, after which its binding to CTLA-4, PD-1, or 4-1BB, respectively, was assessed using Biolayer Interferometry (Figure 4B-D). Antigen binding by untreated A2M-antibodies before LRP1 depletion was approximately 25% of the maximum binding defined by thermolysin activation for all three antibodies. After LRP1 depletion, there was no detectable antigen binding in untreated A2M-ipilimumab and A2M-nivolumab samples, negligible detectable antigen binding in untreated A2M-urelumab samples, and equal binding was observed for thermolysin-activated A2M-antibodies before and after LRP1 depletion. These data indicate that LRP1 depletion was able to deplete A2M-antibodies where the antibodies were capable of antigen binding earlier than normal, further demonstrating that the structure of A2M correlates with antibody accessibility. A2M-ipilimumab was also depleted using Protein L-coated resin, which specifically binds the kappa light chain of human antibodies. Three rounds of depletion were performed. Biolayer interferometry showed that Protein L-based depletion was able to remove antigen binding in untreated A2M-ipilimumab samples (Figure 4E).

[0287] conclusion A2M-antibodies in their native and activated conformations can be distinguished by affinity depletion based on binding to their antigen, to LRP1 or to protein L. This binding can be used to remove activated A2M-antibodies and prepare native A2M-antibodies to a higher purity. Binding experiments comparing antigen binding before and after depletion show that enrichment of native A2M-antibodies results in minimal or no detectable antigen binding by native proteins, demonstrating that antigen binding by untreated A2M-antibodies is caused by contamination with non-native A2M-antibodies. EXAMPLES

[0288] Examining immune checkpoint blockade in cellular assays the purpose To determine whether A2M-antibodies exhibit conformation-dependent target binding in a cellular context and retain the biological activity of their parent antibodies, A2M-atezolizumab was tested in a PD-1 / PD-L1 blockade bioassay.

[0289] material and method Proteins used A2M-atezolizumab was expressed and purified as described for the A2M-antibody fusion constructs in Example 2. Native A2M-atezolizumab was enriched using PD-L1-based affinity depletion as described in Example 4. Methylamine-treated A2M-atezolizumab was prepared by incubation with 200 mM methylamine at 37° C. for 16 hours, followed by desalting back into HBS on a PD-10 column. Atezolizumab scFv was also expressed with an N-terminal StrepII tag in fusion with a human IgG1 Fc region, and this atezolizumab-hFc was purified using the same protocol as for the antigen-hFc fusion constructs described in Example 3, i.e., StrepTactin affinity chromatography followed by size exclusion chromatography.

[0290] Cell-based evaluation of immune checkpoint blockade The ability of A2M-atezolizumab and atezolizumab-hFc to block the PD-1 / PD-L1 pathway on human T cells was tested using a PD-1 / PD-L1 blockade bioassay developed by Promega. Jurkat cells were cultured in RPMI 1640 medium supplemented with penicillin / streptomycin and 10% fetal bovine serum, and CHO-K1 cells were cultured in DMEM medium supplemented with penicillin / streptomycin and 10% fetal bovine serum. 40 mL of 100% PBS was added per well the day before the assay was performed. * 10 3CHO-K1 cells were seeded onto a 96-well plate. On the day of the assay, the medium was removed from the wells and 40 μL of antibody solution diluted in assay buffer (RPMI 1640 medium with 1% fetal bovine serum) and 50 μL of antibody solution diluted in assay buffer were added. * 10 3 The luminescence signal was given as the averaged normalized luminescence in triplicate wells, background (measured from wells that did not receive any antibody) was subtracted, and responses were normalized to the highest measured luminescence from the assay (background subtracted).

[0291] result A PD-1 / PD-L1 blockade bioassay developed by Promega was used to investigate conformation-dependent PD-L1 blockade by A2M-atezolizumab. This bioassay uses a human Jurkat T cell line expressing human PD-1 and a luciferase reporter gene driven by an NFAT response element to represent human T cells. PD-L1 was detected using CHO-K1 expressing human PD-L1 and an engineered surface protein that activates the cognate TCR in an antigen-independent manner. + represents a target cell. TCR-activated CHO-K1 is believed to activate Jurkat cells and induce an NFAT-driven luciferase response, except that this response is inhibited by PD-1-mediated signaling due to engagement of PD-L1 on CHO-K1 cells with PD-1 on Jurkat cells. When PD-1 or PD-L1 is blocked by antibodies, the luciferase response is restored. A titration series (20 pM to 200 nM) of A2M-atezolizumab in its native and methylamine-treated collapsed conformations was used to block PD-L1 on CHO-K1 cells. An IgG-like construct made by fusing the atezolizumab scFv to a human Fc region was included for comparison. A2M-atezolizumab and atezolizumab-hFc in both conformations all produced concentration-dependent luminescence responses (Figure 5). The maximum responses of methylamine-treated A2M-atezolizumab and atezolizumab-hFc were similar, and no saturation response for native A2M-atezolizumab was achieved at the highest concentration measured, 200 nM (and the maximum response was therefore assumed to be the same for methylamine-treated A2M-atezolizumab). Both methylamine-treated A2M-atezolizumab and atezolizumab-hFc had subnanomolar EC of 400 and 80 pM, respectively. 50 values, whereas native A2M-atezolizumab showed an EC 50 Thus, there was an approximately 500-fold difference in activity of A2M-atezolizumab between its native and activated conformations.

[0292] conclusion A2M-atezolizumab inhibited PD-1 in a cellular assay of immune checkpoint blockade. + We demonstrated a conformation-dependent ability to block PD-L1 and restore NFκB signaling in T cells, demonstrating that A2M-atezolizumab exhibits conformation-dependent binding to cell surface PD-L1 and that A2M-atezolizumab retains the PD-L1-blocking functionality of the parental atezolizumab antibody. EXAMPLES

[0293] Modification of the A2MBay region to target specific proteases the purpose The sequence of the bait region of A2M determines whether the bait region can be cleaved by a given protease, and therefore which proteases can activate (and be captured by) A2M. The bait region of wild-type A2M can be cleaved by almost all human proteases, and it would be advantageous to restrict the cleavage of the bait region to a specified protease, and more specifically to the target disease tissue. We first investigated whether the bait region could be replaced with a minimal sequence that does not contain cleavage sites for the majority of human proteases. We then investigated whether protease cleavage sites could be reintroduced into this minimal sequence in order to generate a bait region sequence with improved specificity for a single protease or a family of proteases, in this example, matrix metalloproteases (MMPs).

[0294] material and method Proteins used A2M proteins with modified bait region sequences were expressed in HEK292F cells and purified as described for the A2M-antibody in Example 2. The amino acid sequences of these A2M proteins are given in SEQ ID NOs: 65-73. N-terminally StrepII-tagged proMMP2 (uniprot ID P08253, SEQ ID NOs: 61-62) was expressed and purified using StrepTactin affinity and size-exclusion chromatography as described for the StrepII-tagged hFc fusion protein in Example 3. ProMMP2 was activated using 1 mM APMA by incubation at 37°C for 15 min followed by desalting into HBS with 10 mM CaCl2 using a PD-10 column (GE Healthcare).

[0295] SDS-PAGE and pore-restricted native PAGE Native pore-restricted PAGE was performed as previously described (36) using homemade gels in TBE buffer (89 mM Tris, 89 mM boric acid, 2 mM EDTA) with acrylamide gradients of 5–10% for A2M analysis and 10–15% for C3 analysis. Pore-restricted electrophoresis gels were run overnight at 100 V in TBE buffer. Denaturing SDS-PAGE was performed using a discontinuous 2-amino-2-methyl-1,3-propanediol and glycine buffer system on homemade 5–15% acrylamide gradient gels (37). Samples were reduced with 25 mM DTT for 5 min at 95 °C.

[0296] Reaction of A2M with methylamines and proteases To aminolyze the thiol esters of A2M, methylamine (pH 8) was added to 250 mM and incubated at 37° C. for at least 45 min. To assess cleavage of A2M by trypsin and LysC, protease was added to a 2.2 to 1 mole / mol ratio of protease to A2M and incubated at 37° C. for 5 min. Digestion was then inhibited using the serine protease inhibitor PMSF (2 mM, 15 min, room temperature). To assess cleavage of A2M by MMP2, MMP2 was added to A2M in HBS with 10 mM CaCl2 to a 6 to 1 mole / mol ratio of MMP2 to A2M and incubated at 37° C. for 15 min and then inhibited using 20 mM EDTA. When other human proteases were used to cleave A2M, incubation lasted for 1 h at 37° C. in HBS with 10 mM CaCl 2 , and PMSF or EDTA was used to inhibit serine and metalloproteases, respectively.

[0297] Determine A2M inhibition of protein substrate cleavage by MMP2 Inhibition of MMPs by A2M was examined using a fluorescently labeled gelatin substrate. 1.4 pmoles (7.5 nM) of MMPs were reacted with 0–2.7 pmoles (0–15 nM) of A2M in 50 mM HEPES, 100 mM NaCl, 5 mM CaCl2 pH 8 for 15 min at 37°C. DQ gelatin from pig skin (Invitrogen) was added to a final concentration of 0.1 mg / ml. The fluorescence (excitation at 485 nm, emission at 520 nm) of the unquenched digestion products of DQ gelatin after 10 min at 37°C was measured on a FLUOstar Omega plate reader (BMG LABTECH). All reactions were performed in triplicate.

[0298] result Substitution of the bait domain with 13 Gly-Gly-Ser triplets generates tetrameric, native, and inducible A2M To remove essentially all protease cleavage sites from the bait region and determine the extent to which the bait region tolerates modification, we replaced the 39-residue wild-type A2M bait region sequence with 13 Gly-Gly-Ser repeats selected for their solubility and low susceptibility to proteolysis (Figure 6A). The resulting "tabula rasa" (TR) bait region was then incorporated into recombinant A2M, yielding A2M that was predominantly tetrameric and in its native conformation as assessed by native PAGE, with intact thiol esters evident from the formation of characteristic heat-induced autolysis products in SDS-PAGE (Figure 6B-C). Upon aminolysis of its thiol esters with methylamine, TR A2M underwent a conformational collapse indistinguishable from that of wild-type A2M, as determined by pore-restricted native PAGE; however, TR A2M was not cleaved in its bait region by either trypsin or LysC and remained in its native conformation when proteolyzed by these proteases outside of its bait region (Figure 6B-C). When a lysine residue was introduced at position 704 of the TR bait region, the resulting bait region could be cleaved by both trypsin and LysC, resulting in protease conjugation and a characteristic structural change in A2M (Figure 6A-C).

[0299] Identification of MMP2 cleavable byte region sequences with improved selectivity Four TR bait regions were designed incorporating the substrate sequence of human MMP2 (Figure 7A). All four TR-based MMP2 substrate bait regions and the wild-type bait region were cleaved by MMP2, but the first TR A2M was not (Figure 7B-D). Incomplete bait region cleavage and intermediate electrophoretic mobility of the A2M:MMP2 complex was observed for both wild-type A2M and for the four MMP2 substrate TR A2Ms.1. Next, we tested whether the four MMP2 substrate bait regions could be cleaved by nine additional human proteases (plasmin, cathepsin G, MMP1, MMP3, MMP8, MMP13, ADAMTS4, ADAMTS5, and ADAMTS13) using reducing SDS-PAGE to assess bait region cleavage and the formation of high MW conjugation products. With the exception of ADAMTS13 (which is highly specific for von Willebrand factor), all evaluated proteases were able to cleave wild-type A2M, but none were able to cleave TR A2M (Figure 7B). Incorporation of any of the four MMP2 substrate sequences into the TR bait region resulted in cleavage by all tested MMPs, and the individual sequences were differentially cleaved by non-MMP proteases; for example, the C9 substrate was the only substrate containing an arginine residue and the only A2M cleaved by plasmin (Figure 7A-B). The S1 substrate was only cleaved by MMPs (Figures 7A-B), and therefore the A2M TR S1 protein was selected for further optimization as an A2M with improved MMP specificity compared to wild-type A2M.

[0300] The native content of tabula rasa-based A2M is improved by shortening the bait region by 7 residues or by restoring 10 C-terminal wild-type residues The first TR A2M protein was expressed with increased amounts of non-native A2M compared to wild-type A2M (Figures 6A, 7C). To address this issue, we tested two modified tabular subunit regions, the first TRΔ7, shortened by seven residues to the full length of 32 residues, and the second TR QRT4, reintroduced the C-terminal quarter of the wild-type subunit region (Figure 8A). Both TRΔ7 and TR QRT4 improved the native content of the resulting A2M to that of wild-type A2M (Figure 8B). The location of the S1 substrate sequence in the TRΔ7 subunit region that resulted in an efficiency of MMP2 inhibition indistinguishable from that of wild-type A2M was identified (Figure 8C), indicating that this truncated subunit region can generate a fully functional A2M.

[0301] conclusion The bait region of A2M could be completely replaced by glycine and serine residues without compromising A2M structure and function, but a glycine-serine bait region shortened to 32 residues was found to improve the yield of native A2M. The glycine-serine bait region was not cleavable by 10 tested human proteases. When the S1 substrate for MMP2 was incorporated into the bait region, five human MMPs were able to cleave the bait region, but five non-MMPs remained unable to cleave it. This demonstrates that the glycine-serine bait region can be used as a platform to create bait regions with improved specificity for proteases or families of proteases (such as MMPs). EXAMPLES

[0302] Modification of the bait region of A2M antibody Research Objective In Example 6, it was found that bait region sequences based on the "tabular rasa" (TR) bait region, which replaces the wild-type bait region with glycine and serine residues, produce A2M proteins that are more specifically cleaved and activated by target proteases. Furthermore, a TR bait region shortened by 7 residues to a length of 32 residues (TRΔ7) was found to result in increased yields of native A2M, and placing an S1 substrate for MMP2 at a specific position in TRΔ7 (TRΔ7 S1 I703) resulted in inhibition of MMP2 equivalent to that of the wild-type A2M bait region. Here, we investigated whether A2M-antibodies incorporating a TR bait region with an MMP2 substrate site could be activated by MMP2 in the same way as A2M-antibodies with a wild-type bait region.

[0303] material and method Proteins used A2M-atezolizumab with the wild-type bait region (SEQ ID NOs: 7-8), the TRΔ7 S1 I703 bait region (SEQ ID NOs: 74-75), or the TRΔ7 S1 I703 P704 bait region (SEQ ID NOs: 76-77) was expressed in HEK293F cells and purified as described for the A2M-antibody in Example 2. ProMMP2 was expressed, purified and activated as described in Example 6.

[0304] Cleavage of A2M by proteases For cleavage of the A2M-antibody with MMP2, MMP2 was added to HBS with 10 mM CaCl2 to a 4:1 molar ratio of MMP2 to A2M, incubated for 15 min at 37° C., and then inhibited using 20 mM EDTA. For cleavage of the A2M-antibody with thermolysin, thermolysin was added to HBS with 10 mM CaCl2 to a 2.2:1 molar ratio of thermolysin to A2M, incubated for 2 min at 37° C., and then inhibited using 20 mM EDTA.

[0305] Biolayer Interferometry Biolayer interferometry was used to investigate the interactions between A2M-atezolizumab with different bite regions using the method described in Example 3.

[0306] SDS-PAGE and pore-restricted native PAGE Native pore-restricted PAGE was performed as previously described (36) using homemade gels in TBE buffer (89 mM Tris, 89 mM boric acid, 2 mM EDTA) with acrylamide gradients of 5–10% for A2M analysis and 10–15% for C3 analysis. Pore-restricted electrophoresis gels were run overnight at 100 V in TBE buffer. Denaturing SDS-PAGE was performed using a discontinuous 2-amino-2-methyl-1,3-propanediol and glycine buffer system on homemade 5–15% acrylamide gradient gels (37). Samples were reduced with 25 mM DTT for 5 min at 95 °C.

[0307] result To evaluate the functionality of A2M-antibody with engineered bait regions, A2M-atezolizumab was expressed with the wild-type bait region, the TRΔ7 S1 I703 bait region (optimized MMP2 substrate bait region described in Example 6), or the TRΔ7 S1 I703 P704 bait region, which minimizes the MMP2 cleavage site and prevents cleavage of residue I703 by serine proteases by adding a proline residue at P'1 position (Figure 9A). All three A2M-atezolizumab proteins were bait regions that were cleaved when treated with MMP2, as assessed by their conformational changes on native PAGE (Figure 9B) and cleavage of A2M subunits on reduced SDS-PAGE (Figure 9C). These results indicate that A2M-antibody with engineered MMP2 substrate bait regions are cleaved by MMP2 at their bait regions. Biolayer interferometry was used to examine the effect of MMP2 cleavage on A2M-atezolizumab protein binding to immobilized PD-L1. MMP2 cleavage was found to result in antigen binding similar to that induced by thermolysin cleavage for A2M-atezolizumab with a wild-type bite region (Figure 9D). Both A2M-atezolizumab proteins with engineered bite regions showed similar antigen binding when cleaved with MMP2 (Figure 9D). These results indicate that bite region cleavage by MMP2 induces antigen binding in A2M-antibody with both the wild-type bite region and the engineered MMP2 substrate bite region.

[0308] conclusion An engineered bait region can be incorporated into an A2M-antibody without disrupting its structurally dependent antigen binding, yet is preferentially cleaved by a target protease such as MMP2, as described in Example 5. MMP2 cleavage can induce antigen binding in A2M-antibodies with wild-type or engineered bait regions. EXAMPLES

[0309] Incorporation of the extracellular domain of the PD1 receptor into A2M Research Objective Here, we investigated whether the extracellular domain of the human PD1 receptor could be incorporated into A2M (in the same manner as an antibody, as shown in the previous example) and whether the resulting A2M-PD1 fusion protein would bind to PD-L1, the ligand for the PD1 receptor, in a manner that depended on the structure of A2M.

[0310] material and method Proteins used The A2M-PD1 fusion construct was expressed and purified as described for the A2M-antibody in Example 1. The extracellular domain of PD1 incorporated into A2M was the same sequence used to test A2M-nivolumab in Example 2, i.e., uniprot ID Q15116, residues 26-150 with a Cys93Ser mutation. The amino acid and nucleotide sequences of A2M-PD1 are given in SEQ ID NOs: 25-26. PD-L1 fused to a human Fc domain was prepared as described in Example 2.

[0311] SDS-PAGE and pore-restricted native PAGE A2M-PD1 was analyzed by reducing SDS-PAGE using the protocol described in Example 2.

[0312] Reaction of A2M-antibody with methylamine and proteases A2M-PD1 was treated with methylamine or the metalloprotease thermolysin to alter its structure, as described in Example 3.

[0313] Biolayer Interferometry Biolayer interferometry was used to examine the binding of A2M-PD1 in untreated, methylamine-, or thermolysin-treated conformations to PD-L1 immobilized on the surface of a biosensor, as described in Example 3.

[0314] result Using the same fusion strategy used to incorporate antibody scFvs and nanobodies into A2M, the extracellular domain of human PD1 was incorporated into A2M, and the resulting A2M-PD1 was expressed and purified using standard A2M protocols (Figure 10A). Next, the conformational dependence of PD-L1 binding by A2M-PD1 was assessed by biolayer interferometry. PD-L1 binding by A2M-PD1 was strongly dependent on the conformation of A2M (Figure 10B). Control samples with untreated A2M-PD1 showed only a small degree of binding because native A2M-PD1 was not purified from non-native A2M-PD1 prior to this experiment, for example, using LRP1-based depletion as described in Example 3. In contrast, both methylamine- and thermolysin-treated A2M showed greatly enhanced binding responses, and these responses were very similar to each other. When A2M-PD1 in its native conformation was enriched by three rounds of LRP1-based depletion of non-native A2M-PD1, binding by untreated A2M-PD1 was undetectable.

[0315] conclusion PD1 could be incorporated into A2M, resulting in functional A2M capable of undergoing its typical methylamine- and thermolysin-induced conformational changes and PD1 capable of binding to its ligand, PD-L1. Furthermore, binding of PD1 to PD-L1 was dependent on the conformation of A2M, and binding of A2M-PD1 in its native conformation to PD-L1 was undetectable. EXAMPLES

[0316] Incorporation of IL2 cytokine into A2M the purpose Here, we investigated whether the IL2 cytokine could be incorporated into A2M (in the same manner as antibodies, as shown in the previous examples) and whether the resulting A2M-IL2 fusion protein would bind to the IL2 receptor, IL-2Rα, in a manner that was dependent on the structure of A2M.

[0317] material and method Proteins used The A2M-IL2 fusion construct was expressed and purified as described for the A2M-antibody in Example 1. The IL2 cytokine incorporated into A2M used the wild-type human sequence (uniprot P60568, residues 21-153). The amino acid and nucleotide sequences of A2M-IL2 are given in SEQ ID NOs: 23-24. The extracellular domain of the IL2 receptor, IL-2Rα (uniprot P01589, residues 22-238, with a Cys213Ala mutation, SEQ ID NO: 43) was expressed as a Strep-tagged human Fc fusion protein (SEQ ID NO: 57-58) as described for the other antigens in Example 2 and purified in the same manner.

[0318] SDS-PAGE and pore-restricted native PAGE A2M-IL2 was analyzed by reducing SDS-PAGE using the protocol described in Example 2.

[0319] Reaction of A2M-antibody with methylamine and proteases A2M-IL2 was treated with methylamine or the metalloprotease thermolysin to alter its structure, as described in Example 3.

[0320] Biolayer Interferometry Biolayer interferometry was used to examine the binding of A2M-IL2 in untreated, methylamine-, or thermolysin-treated conformations to IL-2Rα immobilized on the surface of a biosensor, as described in Example 3.

[0321] result Using the same fusion strategy used to incorporate antibody scFvs and nanobodies into A2M, the human cytokine IL2 was incorporated into A2M, and the resulting A2M-IL2 was expressed and purified using standard A2M protocols (Figure 11A). Next, the structural dependence of IL-2Rα binding by A2M-IL2 was assessed by biolayer interferometry. IL-2Rα binding by A2M-IL2 was dependent on the structure of A2M (Figure 11B). Control samples with untreated A2M-IL2 showed moderate binding, even after using LRP1-based depletion of non-native A2M-IL2. Cleavage of the A2M bait region with thermolysin resulted in an immediate increase in association rate and saturation of binding, whereas amino acid degradation of the A2M thiol ester with methylamine resulted in a much larger increase in both association rate and binding saturation. The extent of binding (k obs The IL-1 binding protein (as determined by the IL-1 binding protein value) is increased approximately 10-fold by methylamine treatment compared to A2M-IL2 in its native conformation.

[0322] conclusion IL2 could be incorporated into A2M, resulting in functional A2M-IL2 that underwent its typical methylamine- and thermolysin-induced conformational changes and IL2 that could bind to the receptor IL-2Rα. Furthermore, this receptor binding by A2M-IL2 was dependent on the structure of A2M, and increased receptor binding was observed when the A2M structure was disrupted by bait region cleavage or thiol ester amino acid degradation. EXAMPLES

[0323] Exploring other fusion strategies for the incorporation of biopharmaceutical moieties into A2M the purpose Previous examples examining proteinaceous fusion constructs of A2M and a biopharmaceutical moiety used the ciRBD approach, where the biopharmaceutical moiety is inserted between residues 1402 and 1403 of A2M. Here, we investigated whether target binding that is dependent on the structure of A2M could be achieved by four other approaches: fusion, iRBD, miRBD, and tRBD.

[0324] material and method Proteins used All fusion constructs of A2M and biopharmaceutical moieties were expressed and purified as described for the A2M-antibody fusion constructs in Example 2. Depletion of non-native A2M was not performed. The amino acid and nucleotide sequences of A2M-fusion-EgA1 (SEQ ID NOs: 94-95), A2M-iRBD-EgA1 (SEQ ID NOs: 84-85), A2M-miRBD-EgA1 (SEQ ID NOs: 86-87), A2M-miRBD-atezolizumab (SEQ ID NOs: 88-89), A2M-miRBD-KN035 (SEQ ID NOs: 90-91), and A2M-tRBD-EgA1 (SEQ ID NOs: 92-93) are given. EGFR and PD-L1 fused to human Fc regions (SEQ ID NOs: 45-48) were generated as described in Example 3.

[0325] Reaction of A2M-antibody with methylamine and proteases The A2M-antibody was reacted with methylamine or protease as described in Example 3.

[0326] Biolayer Interferometry Biolayer interferometry was performed as described in Example 3.

[0327] result To determine whether shielding of the biopharmaceutical moiety in A2M could be achieved by incorporating the biopharmaceutical moiety in A2M in a manner other than the previously used ciRBD approach, four new fusion approaches were tested. First, the EgA1 nanobody was expressed immediately C-terminal to the RBD domain of A2M to generate the A2M-fused-EgA1 protein. A2M-fused-EgA1 did not show conformational dependence of FgA1 binding to EGFR (FIG. 12A), indicating that not all positions adjacent to the RBD domain are shielded in the native structure of A2M.

[0328] In the second approach, an iRBD, EgA1 nanobody, was inserted into the RBD domain replacing A2M residues 1392-1403. The resulting A2M-iRBD-EgA1 protein showed a high degree of conformational dependency comparable to that of the ciRBD approach (Figure 12B) (see Example 3). This indicates that the region of the RBD domain of A2M adjacent to residues 1393-1403 is a suitable site for incorporation of a biopharmaceutical moiety to achieve conformational dependency. Thus, the third approach, miRBD, also achieved conformational dependency by incorporation of EgA1 nanobody, KN035 nanobody, or atezolizumab scFv at the position replacing A2M residues 1393-1395 (Figure 12B-E).

[0329] In the fourth approach, tRBD, coiled-coil interactions were used to bring the incorporated biopharmaceutical moiety (EgA1) into close proximity with RBD residues 1393-1403. The EgA1 nanobody was incorporated at position C-terminal to the RBD domain with an alpha-helical sequence designed to be complementary to A2M residues 1393-1403 at its N-terminus. The alpha-helical sequence is attached to the RBD domain with a 15-residue linker to allow the alpha-helix to interact with residues 1393-1403. Additionally, modifications were made to A2M residues 1393-1403 to enhance the designed complementary coiled-coil interaction. The resulting A2M-tRBD-EgA1 protein demonstrated the structure-dependence of the EgA1 / EGFR interaction (Figure S1F), showing that coiled-coil interactions could bring the EgA1 nanobody into close proximity with residues 1393-1403 and that this proximity resulted in at least partial shielding of the EgA1 nanobody in the native structure of A2M.

[0330] conclusion Examination of fusion, iRBD, miRBD, and tRBD approaches to generating fusion constructs of A2M and biotherapeutic moieties revealed that a position proximal to A2M RBD residues 1393-1403, either by direct fusion at this site (as seen with the ciRBD, iRBD, and ciRBD approaches) or by localization of the moiety to this location through other means (e.g., through coiled-coil interactions as shown by A2M-tRBD-EgA1), confers structure-dependent target binding for many of the different biotherapeutic moieties tested (16 in total, considering all ciRBD, iRBD, miRBD, and tRBD fusion constructs). EXAMPLES

[0331] Study of insertion sites in the RBD region the purpose To identify sites for drug insertion in the RBD of A2M that provide structure-dependent accessibility.

[0332] material and method Figures were prepared using PyMol Molecular Graphics System software (version 2.3.0).

[0333] result In the iRBD, miRBD, and ciRBD approaches to the creation of A2M-based prodrugs, residues 1392-1403 of the RBD domain of A2M are replaced with a drug sequence (as well as N- and C-terminal linkers) or the drug is inserted between residues 1402-1403 without altering any residues in A2M. Residues 1391-405 or 1392-1404 contain loops or linker regions between the strands of the beta sheet structure, and such loops are well suited for modification, in contrast to the beta sheet sequence, where modifications are more likely to affect the folding of the domain.

[0334] Furthermore, the orientation of the loop is also crucial to achieve structure-dependent drug location, since fusion of the drug at position 1474 opposite the RBD (in the A2M-fusion-EgA1 construct) always yields an accessible drug.

[0335] After structural evaluation of the RBD domain, three additional loop regions suitable for drug insertion were identified, namely, regions containing residues 1368–1379 (loop 1), 1420–1426 (loop 3), and 1450–1457 (loop 4), in addition to the empirically tested region containing residues 1392–1404 (loop 2) (Figure 13). All three loops extend between the beta strands and are oriented in a similar direction to loop 2 (1392–1404), with these loops pointing inwards toward the interior of the A2M tetramer.

[0336] conclusion In addition to the region containing residues 1392–1404 (loop 2), three additional loops were identified containing residues 1368–1379 (loop 1), 1420–1426 (loop 3), and 1450–1457 (loop 4) of A2M that are deemed available for replacement or direct insertion with one or more drugs to provide structure-dependent binding of its therapeutic target.

[0337] Sequence Listing This specification references a Sequence Listing, which was submitted electronically as an XML file entitled "SEQUENCE LIST 77582PC01 26 01 23" on January 31, 2023. The XML file was created on January 26, 2023 and is 426KB in size. The entire contents of the Sequence Listing are incorporated herein by reference.

[0338] The sequence listing contains the following sequences: SEQ ID NO:1 - Recombinant wild-type A2M-protein sequence SEQ ID NO:2 - Recombinant wild-type A2M-DNA sequence SEQ ID NO:3 - RBD domain (aa 1335 to 1474 of wild type A2M) - Protein sequence SEQ ID NO:4 - byte region (aa 690 to 728 of wild type A2M) - protein sequence SEQ ID NO:5 - A2M ciRBD EgA1-protein sequence SEQ ID NO:6-A2M ciRBD EgA1-DNA sequence SEQ ID NO:7-A2M ciRBD Atezolizumab K1393A K1397A-protein sequence SEQ ID NO:8-A2M ciRBD Atezolizumab K1393A K1397A-DNA sequence SEQ ID NO:9-A2M ciRBD KN035 K1393A K1397A-protein sequence SEQ ID NO:10-A2M ciRBD KN035 K1393A K1397A-DNA sequence SEQ ID NO:11 - A2M ciRBD Nivolumab-protein sequence SEQ ID NO:12-A2M ciRBD Nivolumab-DNA sequence SEQ ID NO:13 - A2M ciRBD ipilimumab-protein sequence SEQ ID NO:14-A2M ciRBD ipilimumab-DNA sequence SEQ ID NO:15 - A2M ciRBD foralumab-protein sequence SEQ ID NO:16-A2M ciRBD foralumab-DNA sequence SEQ ID NO:17-A2M ciRBD muromonab-protein sequence SEQ ID NO:18-A2M ciRBD muromonab-DNA sequence SEQ ID NO:19-A2M ciRBD Urelumab-protein sequence SEQ ID NO:20-A2M ciRBD Urelumab-DNA sequence SEQ ID NO:21 - A2M ciRBD Adalimumab-protein sequence SEQ ID NO:22-A2M ciRBD Adalimumab-DNA sequence SEQ ID NO:23 - A2M ciRBD IL2-protein sequence SEQ ID NO:24-A2M ciRBD IL2-DNA sequence SEQ ID NO:25 - A2M ciRBD PD1 - protein sequence SEQ ID NO:26-A2M ciRBD PD1-DNA sequence SEQ ID NO:27 - EgA1 Nanobody-protein sequence SEQ ID NO:28 - Atezolizumab scFv(VH_VL)-protein sequence SEQ ID NO:29-KN035 Nanobody-protein sequence SEQ ID NO:30 - Nivolumab scFv(VH_VL)-protein sequence SEQ ID NO:31 - Ipilimumab scFv(VH_VL)-protein sequence SEQ ID NO:32 - Foralumab scFv(VH_VL)-protein sequence SEQ ID NO:33 - Muromonab scFv(VH_VL)-protein sequence SEQ ID NO:34 - Urelumab scFv(VH_VL)-protein sequence SEQ ID NO:35 - Adalimumab scFv(VH_VL)-protein sequence SEQ ID NO:36 - IL2 cytokine-protein sequence SEQ ID NO:37 - EGFR extracellular domain - protein sequence SEQ ID NO:38 - PDL-1 extracellular domain - protein sequence SEQ ID NO:39 - PD-1 extracellular domain, C93S mutation - protein sequence SEQ ID NO:40 - CTLA-4 extracellular domain - protein sequence SEQ ID NO:41 - CD3γε extracellular domain - protein sequence SEQ ID NO: 42-4-1BB Extracellular domain - protein sequence SEQ ID NO:43 - IL-2Rα extracellular domain, C213A mutation - protein sequence SEQ ID NO:44 - Human IgG1 Fc region - protein sequence SEQ ID NO:45 - EGFR extracellular domain - protein sequence SEQ ID NO: 46 - EGFR extracellular domain - DNA sequence SEQ ID NO: 47 - PDL-1 extracellular domain - protein sequence SEQ ID NO: 48 - PDL-1 extracellular domain - DNA sequence SEQ ID NO: 49 - PD-1 extracellular domain, C93S mutation - protein sequence SEQ ID NO:50 - PD-1 extracellular domain, C93S mutation - DNA sequence SEQ ID NO:51 - CTLA-4 extracellular domain - protein sequence SEQ ID NO:52 - CTLA-4 extracellular domain - DNA sequence SEQ ID NO:53 - CD3γε extracellular domain - protein sequence SEQ ID NO:54 - CD3γε extracellular domain - DNA sequence SEQ ID NO: 55-4-1BB Extracellular domain - protein sequence SEQ ID NO: 56-4-1BB Extracellular domain-DNA sequence SEQ ID NO:57 - IL-2Rα extracellular domain, C213A mutation - protein sequence SEQ ID NO:58 - IL-2Rα extracellular domain, C213A mutation - DNA sequence SEQ ID NO:59 - TNFα cytokine, StrepII tag and A2M leader peptide - protein sequence SEQ ID NO:60 - TNFα cytokine, StrepII tag and A2M leader peptide - DNA sequence SEQ ID NO:61 - pro MMP2 with N-terminal Strep tag - protein sequence SEQ ID NO:62-pro MMP2 with N-terminal Strep tag-DNA sequence SEQ ID NO:63 - LRP1 cluster 1B with Nt Strep tag and Ct hFc-protein sequence SEQ ID NO:64 - LRP1 cluster 1B with Nt Strep tag and Ct hFc - DNA sequence SEQ ID NO:65 - A2M, TR-protein sequence with modified byte region SEQ ID NO:66 - A2M, TR K704-protein sequence with modified byte region SEQ ID NO:67 - A2M, TR A21A-protein sequence with modified byte region SEQ ID NO:68 - A2M, TR B74-protein sequence with modified byte region SEQ ID NO:69 - A2M, TR C9-protein sequence with modified byte region SEQ ID NO:70 - A2M, TR S1-protein sequence with modified byte region SEQ ID NO:71 - A2M, TRΔ7 S1 I710 with modified byte region - protein sequence SEQ ID NO:72 - A2M, TR S1 QRT4-protein sequence with modified byte region SEQ ID NO:73 - A2M, TRΔ7 S1 I703 with modified byte region - protein sequence SEQ ID NO:74-A2M ciRBD Atez, K1393A K1397A T654C T661C, byte region TRΔ7 S1 I703-protein sequence SEQ ID NO: 75-A2M ciRBD Atez, K1393A K1397A T654C T661C, byte region TRΔ7 S1 I703-DNA sequence SEQ ID NO:76-A2M ciRBD Atez, K1393A K1397A T654C T661C, byte region TRΔ7 S1 I703 P704-protein sequence SEQ ID NO: 77-A2M ciRBD Atez, K1393A K1397A T654C T661C, byte region TRΔ7 S1 I703 P704-DNA sequence SEQ ID NO:78 - N-terminal linker-protein sequence in ciRBD format SEQ ID NO:79 - C-terminal linker-protein sequence in ciRBD format SEQ ID NO:80 - N-terminal linker-protein sequence in iRBD format SEQ ID NO:81 - C-terminal linker-protein sequence in iRBD format SEQ ID NO:82 - One tested N-terminal linker-protein sequence of miRBD format SEQ ID NO:83 - One tested C-terminal linker-protein sequence of miRBD format SEQ ID NO:84 - A2M iRBD N15 / C12 EgA1 - Protein sequence SEQ ID NO: 85-A2M iRBD N15 / C12 EgA1-DNA sequence SEQ ID NO:86-A2M miRBD N18 / C15 EgA1-protein sequence SEQ ID NO: 87-A2M miRBD N18 / C15 EgA1-DNA sequence SEQ ID NO:88-A2M miRBD N18 / C15 Atezolizumab-protein sequence SEQ ID NO:89-A2M miRBD N18 / C15 Atezolizumab-DNA sequence SEQ ID NO:90 - A2M miRBD N18 / C15 KN035 - protein sequence SEQ ID NO: 91-A2M miRBD N18 / C15 KN035-DNA sequence SEQ ID NO:92-A2M tRBD15b EgA1-protein sequence SEQ ID NO: 93-A2M tRBD15b EgA1-DNA sequence SEQ ID NO:94 - A2M-protein sequence with EgA1 nanobody immediately following the RBD C-terminus SEQ ID NO:95 - A2M-DNA sequence with EgA1 nanobody immediately after the RBD C-terminus SEQ ID NO:96 - Cleavage site for MMP (A21A) - Protein sequence SEQ ID NO:97 - Cleavage site for MMP (B74) - Protein sequence SEQ ID NO:98 - Cleavage site (C9) for MMP - Protein sequence SEQ ID NO:99 - Cleavage site (S1) for MMP - Protein sequence SEQ ID NO:100 - Cleavage site for MMP (S1P) - Protein sequence SEQ ID NO:101 - MMP cleavage site and R-protein sequence from wild type bait region SEQ ID NO:102 - Cleavage site - Protein sequence SEQ ID NO:103 - Cleavage site - Protein sequence SEQ ID NO:104 - Cleavage site - Protein sequence SEQ ID NO:105 - Cleavage site - Protein sequence SEQ ID NO:106 - Cleavage site - Protein sequence SEQ ID NO:107 - Cleavage site - Protein sequence SEQ ID NO:108 - Cleavage site - Protein sequence SEQ ID NO:109 - Cleavage site - Protein sequence SEQ ID NO:110 - Cleavage site - Protein sequence SEQ ID NO:111 - cleavage site - protein sequence SEQ ID NO:112 - cleavage site - protein sequence SEQ ID NO:113 - Cleavage site - Protein sequence SEQ ID NO:114 - Cleavage site - Protein sequence SEQ ID NO:115 - Cleavage site - Protein sequence SEQ ID NO:116 - Cleavage site - Protein sequence SEQ ID NO:117 - Cleavage site - Protein sequence SEQ ID NO:118 - Cleavage site - Protein sequence SEQ ID NO:119 - Cleavage site - Protein sequence SEQ ID NO:120 - Cleavage site - Protein sequence SEQ ID NO:121 - Cleavage site - Protein sequence SEQ ID NO:122 - Cleavage site - Protein sequence SEQ ID NO:123 - Cleavage site - Protein sequence SEQ ID NO:124 - Tabular region (TR) - Protein sequence SEQ ID NO: 125 - TR K704 - Protein sequence SEQ ID NO: 126 - TR A21A - protein sequence SEQ ID NO: 127 - TR B74-protein sequence SEQ ID NO: 128 - TR C9-protein sequence SEQ ID NO:129 - TRS1 - Protein sequence SEQ ID NO: 130 - TR S1 QRT4 - protein sequence SEQ ID NO:131 - TRΔ7 S1 I710 - Protein sequence SEQ ID NO:132 - TRΔ7 S1 I703 - Protein sequence SEQ ID NO: 133 - TRΔ7 S1 I703 P704 - protein sequence SEQ ID NO: 134 - CPAMD1 (akaC3) - NP_000055.2 - Protein sequence SEQ ID NO: 135 - CPAMD2 (aka C4A) - NP_009224.2 - Protein sequence SEQ ID NO:136 - CPAMD3 (aka C4B) - NP_001002029.3 - Protein sequence SEQ ID NO: 137 - CPAMD4 (aka C5) - NP_001726.2 - Protein sequence SEQ ID NO:138 - CPAMD5 (akaA2M) - NP_000005.3 - Protein sequence SEQ ID NO: 139 - CPAMD6 (aka PZP) - NP_002855.2 - Protein sequence SEQ ID NO:140 - CPAMD7 (akaCD109) - NP_598000.2 - Protein sequence SEQ ID NO: 141 - CPAMD8 - NP_056507.3 - Protein sequence SEQ ID NO:142 - CPAMD9 (akaA2ML1) - NP_653271.3 - Protein sequence SEQ ID NO:143 - Ovostatin1-Q6IE37.2 - Protein sequence SEQ ID NO:144 - Ovostatin2-Q6IE36.2 - Protein sequence SEQ ID NOs: 145-188 - see Table 1 SEQ ID NOs: 189-210 - see Table 2 SEQ ID NOs: 211-222 - see Table 3 SEQ ID NO:223-GS linker

Claims

1. 1. A proteinaceous prodrug construct, comprising: (a) a complement 3 and pregnancy-associated protein-like, alpha-2-macroglobulin domain-containing (CPAMD) protein or a fragment thereof; and (b) one or more drugs Including, (i) the CPAMD protein or fragment thereof comprises (1) a bait region having at least one protease cleavage site, and (2) a receptor binding domain (RBD); (ii) the one or more drugs are located within or adjacent to the RBD; (iii) the CPAMD protein or fragment thereof can shield one or more drugs and change structure upon proteolytic cleavage of at least one protease cleavage site to make the one or more drugs accessible; Proteinaceous prodrug constructs.

2. 2. The proteinaceous prodrug construct of claim 1, wherein the one or more drugs are located within or near any one of loops 1 to 4 of the RBD.

3. 3. The proteinaceous prodrug construct of claim 1 or 2, wherein the proteinaceous prodrug construct is a fusion protein, and optionally, one or more drugs are positioned within any one of loops 1 to 4 of the RBD, and optionally, the loop is modified relative to the wild-type loop sequence by addition, substitution, or deletion of one or more amino acids to accommodate the one or more drugs, and optionally, the one or more drugs replace one or more amino acids of the loop.

4. The one or more drugs are positioned near any one of loops 1-4 of the RBD, and optionally the proteinaceous prodrug construct comprises a first interaction domain and the one or more drugs comprise a second interaction domain, the first and second interaction domains forming a complex that positions the one or more drugs near the loops, and optionally (i) the first interaction domain and the second interaction domain form a coiled-coil structure; or (ii) the first interacting domain is a tag or epitope sequence within the loop, and the second interacting domain is a functional fragment of a receptor or antibody that can specifically bind to the tag or epitope sequence; The proteinaceous prodrug construct of claim 2.

5. 2. The proteinaceous prodrug construct of claim 1, wherein the proteinaceous prodrug construct is capable of forming multimers, and optionally the multimerization occurs via the LNK region of the CPAMD protein, and / or the multimer is a tetramer formed by two disulfide-bridged dimers.

6. 2. The proteinaceous prodrug construct of claim 1, wherein the CPAMD protein is selected from A2M, PZP, ovostatin 1, ovostatin 2, CPAMD1, CPAMD2, CPAMD3, CPAMD4, CPAMD7, CPAMD8, CPAMD9, and functional homologs thereof; optionally, the CPAMD protein is selected from A2M, PZP, ovostatin 1, and ovostatin 2, and functional homologs thereof.

7. The CPAMD protein is human A2M, or a functional homolog thereof, e.g., a mammalian A2M, and optionally (i) a functional homologue of human A2M has an amino acid sequence that is at least about 80% identical to the amino acid sequence set forth in SEQ ID NO: 1; or (ii) human A2M has an amino acid sequence that is at least about 95% identical to, or identical to, the amino acid sequence set forth in SEQ ID NO:1; optionally, the one or more drugs are located within a region including amino acids 1368-1379, 1392-1404, 1420-1426, or 1450-1457 of human A2M; Optionally, the one or more drugs are: (a) located between amino acids 1402 and 1403 of human A2M; and / or (b) replacing amino acids 1392-1403, 1393-1395, or 1393-1402 of human A2M; The proteinaceous prodrug construct of claim 6.

8. 2. The proteinaceous prodrug construct of claim 1, wherein the one or more drugs are selected from the group consisting of antigen targeting moieties (e.g., single chain or domain antibodies), receptor ligands (e.g., cytokines), extracellular regions of cell surface receptors, extracellular regions of cell surface ligands, and receptor agonists.

9. The byte area is (i) modified to be selectively cleaved by one or more proteases, optionally the one or more proteases selected from one or more serine-, cysteine-, aspartic- and / or metalloproteinases; and / or (ii) modified to contain no protease cleavage sites recognized by human proteases except for a single cleavage site, optionally the modified bait region comprises an engineered amino acid sequence that is flexible and / or hydrophilic, optionally the engineered amino acid sequence is (a) a sequence of glycine, serine, alanine, threonine, and / or proline residues, or (b) combinations of glycine, serine, and / or alanine residues Including, Optionally, the engineered amino acid sequence replaces all or part of the wild-type bite region, and optionally, the engineered amino acid sequence replaces all of the wild-type bite region and has a length equal to that of the wild-type bite region. The proteinaceous prodrug construct of claim 1 .

10. The one or more drugs (i) an antibody, or antigen-binding fragment thereof, that specifically binds to an antigen selected from the group consisting of IL-2, EGFR, PDL-1, PD-1, CTLA-4, CD3γε, 4-1BB, IL-2Rα, and TNFα, optionally selected from the group consisting of atezolizumab, EgA1, ipilimumab, nivolumab, KN035, urelumab, foralumab, muromonab, adalimumab, and a therapeutically active antigen-binding fragment or variant thereof; or (ii) a cytokine selected from the group consisting of IL1, IL1 alpha, IL1 beta, IL2, IL3, IL4, IL6, IL7, IL8, IL9, IL10, IL11, IL12, IL13, IL14, IL15, IL16, IL17, IL18, IL19, IL20, IL21, IL22, IL23, IL24, IL25, IL26, IL27, IL28, IL29, IL30, IL31, IL32, IL33, IL34, IL35, IL36, GM-CSF, TGF-β, CSF-1, insulin, GLP-1, HGH, VEGF, PDGF, BMP, EPO, G-CSF, IL-11, IFN-α, IFN-β, and IFN-γ, or a therapeutically active fragment or variant thereof; The proteinaceous prodrug construct of claim 1.

11. 10. A nucleic acid encoding the proteinaceous prodrug construct of claim 1, optionally contained within a vector, wherein optionally the nucleic acid encoding the proteinaceous prodrug construct is operably linked to a promoter and, optionally, to one or more additional regulatory sequences that regulate expression of the nucleic acid.

12. 12. A host cell comprising the vector of claim 11, optionally a bacterial or eukaryotic host cell, such as a mammalian cell.

13. 13. A proteinaceous prodrug construct according to claim 1, a nucleic acid or vector according to claim 11, or a host cell according to claim 12, for use in a method for treating or preventing a disease or disorder in a subject in need thereof.

14. the disease or disorder is a disease or disorder of the nervous system, eye, circulatory system, respiratory system, digestive system, or skin; optionally, the disease or disorder is a neoplasm, a blood disorder, a metabolic disorder, an autoimmune disease, an immunodeficiency, or an infectious disease; Optionally, the neoplasm is a cancer selected from brain cancer, glioblastoma, lung cancer, colorectal cancer, skin cancer, malignant melanoma, pancreatic cancer, bladder cancer, liver cancer, breast cancer, eye cancer, and prostate cancer; the cancer is a hematological cancer such as selected from the group consisting of multiple myeloma, acute myeloblastic leukemia, chronic myelogenous leukemia, acute lymphocytic leukemia, and chronic lymphocytic leukemia; or the cancer is malignant melanoma, breast cancer, non-small cell lung cancer, pancreatic cancer, head and neck cancer, liver cancer, sarcoma, and B-cell lymphoma; or 14. The proteinaceous prodrug construct, nucleic acid, vector, or host cell for use according to claim 13, wherein the autoimmune disease is selected from arthritis (e.g., rheumatoid arthritis or psoriatic arthritis), multiple sclerosis, systemic lupus erythematosus, and inflammatory bowel disease.

15. (i) introducing the expression vector of claim 11 into a host cell; (ii) growing the host cells under conditions that allow expression of the proteinaceous prodrug construct from the vector; and (iii) Purifying the proteinaceous prodrug construct 2. A method for making the proteinaceous prodrug construct of claim 1, comprising:

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