IgG antibodies contain dozens of lysine residues, and thus, chemical crosslinking based upon a strategy that modifies primarily epsilon-amino groups of lysines will generally result in a heterogenous mixture of various different homodimers that display various different efficacies. Precise quaternary structure may be enforced, for example, by cloning thiols into specific positions within an antibody. Such strategies are known and described, for example, in Shopes, B., “A genetically engineered human IgG mutant with enhanced cytolytic activity,” J. IMMUNOL. 1992 148 (9): 2918-22. A novel crosslinking strategy is depicted in FIG. 1 and described further below.

FIG. 1 depicts an exemplary strategy to crosslink two IgG antibodies with a disulfide bond, which is further described in Example 4 below; this strategy nevertheless shall not limit this disclosure or any patent claim that matures from this disclosure. A first IgG 1 is provided, which comprises two half molecules 2 that each comprise a heavy chain and a light chain. The amino acid sequence of the heavy chain is the same for each half molecule 2, and the amino acid sequence of the light chain is the same for each half molecule 2. The two half molecules 2 are crosslinked with disulfide bonds 3, which occur at the hinge regions of the first IgG 1. Each half molecule 2 comprises a mutation of a native amino acid to cysteine 4, which may occur in either the heavy chains or the light chains. The first IgG 1 comprises two such cysteine mutations 4, which are depicted as present on the heavy chains.

A second IgG 5 is also provided, which comprises two half molecules 6 that each comprise a heavy chain and a light chain. The amino acid sequence of the heavy chain is the same for each half molecule 6, and the amino acid sequence of the light chain is the same for each half molecule 6. The two half molecules 6 are crosslinked with disulfide bonds 3, which occur at the hinge regions of the second IgG 5. Each half molecule 6 lacks the mutation of the native amino acid to cysteine.

The first IgG 1 and the second IgG 5 are combined under mild reducing conditions, such as in the presence of cysteamine, to reduce the disulfide bonds 3 without reducing other disulfide bonds of the first IgG 1 and the second IgG 5. Other disulfide bonds include disulfide bonds that covalently attach the light chains to the heavy chains and disulfide bonds that enforce tertiary structure. Non-limiting examples of suitable reducing agents include cysteamine.

Following reduction of the disulfide bonds 3, the half molecules 2 of the first IgG 1 may dissociate, the half molecules 6 of the second IgG 5 may dissociate, and a half molecule 2 of the first IgG 1 may then pair with a half molecule 6 of the second IgG 5. Various mutations such as F405L and K409R (as described herein when the first IgG 1 and the second IgG 5 are IgG1s) may favor one or both of dissociation of two half molecules 2, 6 of the first IgG 1 and/or the second IgG 5 and the pairing of a half molecule 2 of the first IgG 1 with a half molecule 6 of the second IgG 5.

After incubating the first IgG 1 and the second IgG 5 under reducing conditions that allow for the two half molecules 2, 6 of the first IgG 1 and the second IgG 5 to dissociate and then pair, the paired half molecules 2,6 of the first IgG 1 and the second IgG 5 are oxidized to form disulfide bonds 8 that crosslink the half molecule 2 of the first IgG 1 to the half molecule 6 of the second IgG 5 and result in a chimeric immunotherapeutic 7. The chimeric immunotherapeutic 7 contains a single half molecule 2 of the first IgG 1 such that the chimeric immunotherapeutic 7 comprises a single mutation of a native amino acid to cysteine 4.

After incubating the first IgG 1 and the second IgG 5 under reducing conditions that allow for the two half molecules 2, 6 of the first IgG 1 and the second IgG 5 to dissociate and then pair, the cysteines 4 of two different chimeric immunotherapeutics 7 are oxidized to form a disulfide bond 10 that crosslinks the two different chimeric immunotherapeutics 7 to form a homodimeric antibody 9.

FIG. 1 depicts the disulfide bonds 8 of the chimeric immunotherapeutic 7 forming prior to the disulfide bond 10 that crosslinks the two different chimeric immunotherapeutics 7 to form the homodimeric antibody 9, and these disulfide bonds 8 likely form prior to the disulfide bond 10 that crosslinks the two different chimeric immunotherapeutics 7, for example, due to proximity enforced by noncovalent interactions between the half molecules 2, 6 of the first IgG 1 and the second IgG 5. The order depicted in FIG. 1 nevertheless shall not limit this disclosure or any patent claim that matures from this disclosure, for example, as the disulfide bond 10 that crosslinks the two different chimeric immunotherapeutics 7 may form either contemporaneously with the disulfide bonds 8 that crosslink the half molecules 2,6 of the first IgG 1 and the second IgG 5 or even prior to formation of these disulfide bonds 8.

Two IgG antibodies of a homodimeric antibody are not necessarily identical and may vary, for example, in post-translational modifications that generally result in heterogeneous glycosylation patterns. In some embodiments, the two IgG antibodies of a homodimeric antibody are encoded by the same nucleotide sequence(s), and such IgG antibodies generally have the same amino acid sequences. In some embodiments, the two IgG antibodies of a homodimeric antibody are encoded by different nucleotide sequences and encode different amino acid sequences, which different amino acid sequences may, for example, enforce a specific quaternary structure such as with one or more of inter-IgG disulfide bond(s), complementary sterics, and complementary electrostatic charges to facilitate favorable orientations between the two IgG antibodies that allow for improved avidity relative to random or otherwise un-optimized orientations. In all embodiments, the primary amino acid sequences of the variable domains of the two IgG antibodies of a homodimeric antibody are the same.

The term “cancer” refers to carcinomas, sarcomas, lymphomas, leukemias, germ cell tumors, and blastomas of any type. In some embodiments, the cancer is brain cancer, ovarian cancer, breast cancer, vaginal cancer, vulvar cancer, uterine cancer, cervical cancer, endometrial cancer, prostate cancer, testicular cancer, penile cancer, liver cancer, intrahepatic bile duct cancer, lung cancer, small cell lung cancer, non-small cell lung cancer, bronchial cancer, mesothelioma, pancreatic cancer, gall bladder cancer, non-melanoma skin cancer, melanoma, Kaposi sarcoma, thyroid cancer, head and neck cancer, nasopharyngeal cancer, oropharyngeal cancer, hypopharyngeal cancer, laryngeal cancer, oral cavity cancer, tongue cancer, mouth cancer, salivary gland cancer, esophageal cancer, gastric cancer, colorectal cancer, colon cancer, rectal cancer, anal cancer, kidney cancer, renal cell cancer, renal pelvis cancer, bladder cancer, urethral cancer, Hodgkin lymphoma, non-Hodgkin's lymphoma, myeloma, multiple myeloma, acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, chronic myeloid leukemia, osteosarcoma, or soft tissue cancer. In some specific embodiments, the cancer is multiple myeloma, ovarian cancer, or non-small cell lung cancer.

The term “treat” refers to at least one of: to cure a cancer; to increase the probability that a cancer will be cured; to shorten the time over which a cancer is cured; to increase the probability that the time necessary to cure a cancer will be shortened; to decrease the severity of a cancer; to increase the probability that the severity of a cancer will decrease; to shorten the time over which the severity of a cancer is decreased; to increase the probability that the time necessary to decrease the severity of a cancer will be shortened; to inhibit a cancer from worsening; to increase the probability that a cancer will not worsen; to delay the worsening of a cancer; to increase the probability that the worsening of a cancer will be delayed; to inhibit the occurrence or recurrence of a cancer; to decrease the probability that a cancer will occur or reoccur; to delay the onset of a cancer; to increase the probability that the onset of a cancer will be delayed; to alleviate at least one symptom of a cancer; to increase the probability that at least one symptom of a cancer will be alleviated; to shorten the time over which at least one symptom of a cancer is alleviated; to increase the probability that the time necessary to alleviate at least one symptom of a cancer will be shortened; to decrease the severity of at least one symptom of a cancer; to increase the probability that the severity of at least one symptom of a cancer will be decreased; to shorten the time over which the severity of at least one symptom of a cancer is decreased; to increase the probability that the time necessary to decrease the severity of at least one symptom of a cancer will be shortened; to inhibit at least one symptom of a cancer from worsening; to increase the probability that at least one symptom of a cancer will not worsen; to delay the worsening of at least one symptom of a cancer; to increase the probability that the worsening of at least one symptom of a cancer will be delayed; to inhibit at least one symptom of a cancer from occurring or reoccurring; to decrease the probability that at least one symptom of a cancer will occur or reoccur; to delay the onset of at least one symptom of a cancer; and to increase the probability that the onset of at least one symptom of a cancer will be delayed.

In some embodiments, the administering is performed by injection. In some specific embodiments, the injection is an intravenous injection, intradermal injection, subcutaneous injection, intramuscular injection, intraperitoneal injection, or intratumoral injection. In some very specific embodiments, the injection is an intravenous injection.

The term “therapeutically effective amount” is an amount that is effective to treat cancer, which amount is generally first-determined empirically based upon pre-clinical data and then confirmed by performing pilot and/or phase I-II clinical trials.

In some embodiments, the immunotherapeutic comprises a homodimeric antibody and either a radioisotope or a labile pharmaceutical agent.

In some embodiments, the homodimeric antibody comprises two IgG antibodies that are covalently crosslinked, and each IgG antibody comprises two antigen-binding sites that each specifically bind a cancer-associated antigen such that the homodimeric antibody comprises exactly four antigen-binding sites that each specifically bind the cancer-associated antigen.

In some embodiments, each of the two IgG antibodies has at least 95 percent amino acid sequence identity with a therapeutic antibody selected from 3F8, abagovomab, abituzumab, adecatumumab, amatuximab, andecaliximab, anrukinzumab, apolizumab, ascrinvacumab, atezolizumab, avelumab, basiliximab, bavituximab, belimumab, bemarituzumab, bermekimab, bevacizumab, bivatuzumab, bleselumab, blontuvetmab, brontictuzumab, cabiralizumab, camrelizumab, capromab, carotuximab, cemiplimab, cetrelimab, cetuximab, cibisatamab, cirmtuzumab, cixutumumab, clazakizumab, codrituzumab, conatumumab, cusatuzumab, dacetuzumab, daclizumab, dalotuzumab, daratumumab, dectrekumab, demcizumab, detumomab, dinutuximab, dinutuximab beta, dostarlimab, drozitumab, duligotuzumab, durvalumab, dusigitumab, ecromeximab, edrecolomab, eldelumab, elgemtumab, elotuzumab, elsilimomab, emactuzumab, emibetuzumab, enavatuzumab, enoblituzumab, enoticumab, ensituximab, epratuzumab, etaracizumab, etigilimab, faricimab, farletuzumab, fibatuzumab, ficlatuzumab, figitumumab, flanvotumab, fresolimumab, futuximab, galiximab, ganitumab, gatipotuzumab, gevokizumab, gilvetmab, gimsilumab, girentuximab, gomiliximab, icrucumab, ifabotuzumab, imalumab, imaprelimab, imgatuzumab, inebilizumab, inolimomab, intetumumab, ipilimumab, iratumumab, isatuximab, iscalimab, istiratumab, labetuzumab, lacnotuzumab, lebrikizumab, lenzilumab, leronlimab, lexatumumab, lintuzumab, lirilumab, lucatumumab, lulizumab pegol, lumiliximab, lumretuzumab, lutikizumab, mapatumumab, margetuximab, matuzumab, milatuzumab, mitumomab, modotuximab, mogamulizumab, monalizumab, namilumab, narnatumab, navicixizumab, naxitamab, necitumumab, nesvacumab, nimotuzumab, nivolumab, obinutuzumab, ocaratuzumab, ocrelizumab, ofatumumab, olaratumab, oleclumab, olokizumab, omburtamab, ontuxizumab, oregovomab, otlertuzumab, panitumumab, pankomab, parsatuzumab, pasotuxizumab, patritumab, pembrolizumab, pemtumomab, pertuzumab, pidilizumab, pritumumab, prolgolimab, racotumomab, radretumab, ramucirumab, ravagalimab, relatlimab, retifanlimab, rilotumumab, rinucumab, rituximab, robatumumab, romilkimab, rosmantuzumab, samalizumab, sarilumab, selicrelumab, seribantumab, sibrotuzumab, siltuximab, sintilimab, sirukumab, spartalizumab, tabalumab, tafasitamab, talacotuzumab, tarextumab, tavolimab, telisotuzumab, tenatumomab, teneliximab, tepoditamab, teprotumumab, theralizumab, tigatuzumab, timigutuzumab, tiragotumab, tislelizumab, tomuzotuximab, tositumomab, tovetumab, tralokinumab, trastuzumab, tremelimumab, ublituximab, ulocuplumab, urelumab, utomilumab, vanalimab, vantictumab, vanucizumab, varisacumab, varlilumab, veltuzumab, volociximab, vonlerolizumab, votumumab, xentuzumab, zalutumumab, zatuximab, zenocutuzumab, and zolbetuximab. In some specific embodiments, a first IgG of the two IgG antibodies has at least 98 percent amino acid sequence identity with the therapeutic antibody. In some very specific embodiments, the first IgG has at least 99 percent amino acid sequence identity with the therapeutic antibody. The first IgG may lack 100 percent amino acid sequence identity with the therapeutic antibody because the first IgG comprises a mutation of a native amino acid to a cysteine (such as either S444C or S119C) to allow for a disulfide bond that crosslinks chimeric IgGs of a dimeric immunotherapeutic. The first IgG may also lack 100 percent amino acid sequence identity with the therapeutic antibody, for example, to introduce one or more mutations that favor dissociation of half molecules of the first IgG (such as either F405L or K409R). The first IgG may also lack 100 percent amino acid sequence identity with the therapeutic antibody, for example, to remove or alter glycosylation sites, to modulate effector function, to modulate half-life in vivo, to improve stability, to reduce antigenicity in vivo, as an artifact of cloning, and/or for any number of other reasons.

In some embodiments, the first IgG has at least 95 percent amino acid sequence with a therapeutic antibody set forth in the preceding paragraph, and the second IgG has at least 95 percent amino acid sequence identity with the same therapeutic antibody. In some specific embodiments, the first IgG has at least 98 percent amino acid sequence with a therapeutic antibody set forth in the preceding paragraph, and the second IgG has at least 98 percent amino acid sequence identity with the same therapeutic antibody. In some very specific embodiments, the first IgG has at least 99 percent amino acid sequence with a therapeutic antibody set forth in the preceding paragraph, and the second IgG has at least 99 percent amino acid sequence identity with the same therapeutic antibody.

In some embodiments, the homodimeric antibody is a homodimer of 3F8, abagovomab, abituzumab, adecatumumab, amatuximab, andecaliximab, anrukinzumab, apolizumab, ascrinvacumab, atezolizumab, avelumab, basiliximab, bavituximab, belimumab, bemarituzumab, bermekimab, bevacizumab, bivatuzumab, bleselumab, blontuvetmab, brontictuzumab, cabiralizumab, camrelizumab, capromab, carotuximab, cemiplimab, cetrelimab, cetuximab, cibisatamab, cirmtuzumab, cixutumumab, clazakizumab, codrituzumab, conatumumab, cusatuzumab, dacetuzumab, daclizumab, dalotuzumab, daratumumab, dectrekumab, demcizumab, detumomab, dinutuximab, dinutuximab beta, dostarlimab, drozitumab, duligotuzumab, durvalumab, dusigitumab, ecromeximab, edrecolomab, eldelumab, elgemtumab, elotuzumab, elsilimomab, emactuzumab, emibetuzumab, enavatuzumab, enoblituzumab, enoticumab, ensituximab, epratuzumab, etaracizumab, etigilimab, faricimab, farletuzumab, fibatuzumab, ficlatuzumab, figitumumab, flanvotumab, fresolimumab, futuximab, galiximab, ganitumab, gatipotuzumab, gevokizumab, gilvetmab, gimsilumab, girentuximab, gomiliximab, icrucumab, ifabotuzumab, imalumab, imaprelimab, imgatuzumab, inebilizumab, inolimomab, intetumumab, ipilimumab, iratumumab, isatuximab, iscalimab, istiratumab, labetuzumab, lacnotuzumab, lebrikizumab, lenzilumab, leronlimab, lexatumumab, lintuzumab, lirilumab, lucatumumab, lulizumab pegol, lumiliximab, lumretuzumab, lutikizumab, mapatumumab, margetuximab, matuzumab, milatuzumab, mitumomab, modotuximab, mogamulizumab, monalizumab, namilumab, narnatumab, navicixizumab, naxitamab, necitumumab, nesvacumab, nimotuzumab, nivolumab, 20acituzumab20, ocaratuzumab, ocrelizumab, ofatumumab, olaratumab, oleclumab, olokizumab, omburtamab, ontuxizumab, oregovomab, otlertuzumab, panitumumab, pankomab, parsatuzumab, pasotuxizumab, patritumab, pembrolizumab, pemtumomab, pertuzumab, pidilizumab, pritumumab, prolgolimab, racotumomab, radretumab, ramucirumab, ravagalimab, relatlimab, retifanlimab, rilotumumab, rinucumab, rituximab, robatumumab, romilkimab, rosmantuzumab, samalizumab, sarilumab, selicrelumab, seribantumab, sibrotuzumab, siltuximab, sintilimab, sirukumab, spartalizumab, tabalumab, tafasitamab, talacotuzumab, tarextumab, tavolimab, telisotuzumab, tenatumomab, teneliximab, tepoditamab, teprotumumab, theralizumab, tigatuzumab, timigutuzumab, tiragotumab, tislelizumab, tomuzotuximab, tositumomab, tovetumab, tralokinumab, trastuzumab, tremelimumab, ublituximab, ulocuplumab, urelumab, utomilumab, vanalimab, vantictumab, vanucizumab, varisacumab, varlilumab, veltuzumab, volociximab, vonlerolizumab, votumumab, xentuzumab, zalutumumab, zatuximab, zenocutuzumab, or zolbetuximab. Homodimeric versions of the foregoing antibodies may be manufactured, for example, with the SATP/SATA and sulfo-SMCC/SMCC cross-linking strategy as described herein.

In some embodiments, the homodimeric antibody comprises two bispecific IgG antibodies that are covalently crosslinked, and each IgG antibody comprises two antigen-binding sites that each specifically bind a different cancer-associated antigen such that the homodimeric antibody comprises exactly four antigen-binding sites that each specifically bind one of two different cancer-associated antigen. In some specific embodiments, the homodimeric antibody is a homodimer of amivantamab, glofitamab, talquetamab, or teclistamab, which are each bispecific antibodies.

In some embodiments, the cancer-associated antigen is 4-1BB, 5′-nucleotidase, 5T4, activin receptor-like kinase 1, alpha-fetoprotein, angiopoietin 2, AXL, B7-H3, B-cell activating factor (BAFF), B-cell maturation antigen (BCMA), B-cell receptor (BCR), c-Met, C242, CA-125, CanAg, carbonic anhydrase 9 (CA-IX), carcinoembryonic antigen, CCR4, CCR5, CD3, CD4, CD19, CD20, CD22, CD23, CD25, CD27, CD28, CD30, CD33, CD37, CD38, CD40, CD44, CD51, CD56, CD70, CD74, CD79B, CD80, CD123, CD134, CD152, CD200, CD276, CD319, CEACAM5, claudin 18, coagulation factor III, connective tissue growth factor (CTGF), colony stimulating factor 1 (CSF1), colony stimulating factor 1 receptor (CSF1R), colony stimulating factor 2 (CSF2), CTLA-4, CXCR4, dendritic cell-associated lectin 2, DLL3, DLL4, DR5, EGFL7, EGFR, endoglin, EpCAM, ephrin receptor A3 (EPHA3), epidermal growth factor receptor (EGFR), ERBB3 (HER3), ERB4, fibroblast activation protein alpha (FAP), FGFR2, fibronectin extra domain-B, folate hydrolase, folate receptor 1, Frizzled receptor, GD2 ganglioside, GD3 ganglioside, gelatinase B, glycoprotein 100 (gp100), glypican 3, GPNMB, G protein-coupled receptor 5D (GPRC5D), GUCY2C, hepatocyte growth factor (HGF), HER1, HER2, HGFR, histone complex, HLA-DR, human scatter factor receptor kinase, IGF-1 receptor (IGF-1R; CD221), IGF-2, interleukin 1alpha, interleukin-2, interleukin-6, interleukin-13, integrin alph5beta1, integrin alpha Vbeta3, KIR2D, LAG3, Lewis-Y antigen, LIV-1, LRRC15, macrophage migration inhibitory factor (MIF), MCP-1, melanoma cell adhesion molecule (MCAM), mesothelin, MUC1, MUC5AC, nectin-4, NGNA ganglioside, Notch 1, Notch receptor, NRP1, PCDC1, PD-1, PD-L1, PDGFRA, phosphate-sodium co-transporter, phosphatidylserine, PTK7, root plate-specific spondin 3, ROR1, SDC1, SLAMF7, SLITRK6, Sp17, STEAP1, syndecan 1, TEM1, tenascin C, TGF-beta, TIGIT, TRAIL-R1, TRAIL-R2, tumor-associated calcium signal transducer 2 (TROP-2), tumor antigen CTAA16.88, tumor-specific glycosylated MUC1, tumor-associated glycoprotein 72 (TAG-72), TWEAK receptor, TYRP1, VEGF-A, VEGFR-1, VEGFR-2, or vimentin. In some specific embodiments, the cancer-associated antigen is Sp17.

In some embodiments, the method comprises administering a therapeutically effective amount of an immunotherapeutic to the subject, wherein: (1) the immunotherapeutic comprises a homodimeric antibody and either a radioisotope or a labile pharmaceutical agent; (2) the homodimeric antibody comprises two IgG antibodies that are covalently crosslinked; and (3) each IgG antibody comprises two antigen-binding sites that each specifically bind a cancer-associated antigen such that the homodimeric antibody comprises exactly four antigen-binding sites that each specifically bind the cancer-associated antigen.

Various aspects of this disclosure relate to a method to treat cancer in a human subject, comprising administering to the subject a therapeutically effective amount of an immunotherapeutic, wherein (1) the cancer comprises cells that express Sp17; (2) the immunotherapeutic comprises a homodimeric antibody that comprises two IgG antibodies that are covalently crosslinked; and (3) each IgG antibody comprises two antigen-binding sites that each specifically bind Sp17 such that the homodimeric antibody comprises exactly four antigen-binding sites that each specifically bind Sp17.

In some embodiments, the immunotherapeutic is an immunoconjugate, and the homodimeric antibody is conjugated to a radioactive isotope. In some specific embodiments, the radioactive isotope is actinium-225, astatine-211, bismuth-212, bismuth-213, copper-67, gallium-68, holmium-166, indium-111, iodine-124, iodine-131, lutetium-177, samarium-153, technetium-99, terbium-149, or yttrium-90. In some very specific embodiments, the radioactive isotope is indium-111, iodine-124, iodine-131, lutetium-177, or yttrium-90.

In some embodiments, the homodimeric antibody is a homodimer of 3F8, clivatuzumab tetraxetan, derlotuximab biotin, ibritumomab tiuxetan, lilotomab satetraxetan, tacatuzumab tetraxetan, or tositumomab, each of which are immunoconjugates. Homodimeric versions of the foregoing antibodies may be manufactured, for example, with the SATP/SATA and sulfo-SMCC/SMCC cross-linking strategy as described herein.

Examples of antibodies conjugated to radioactive isotopes include tositumomab (also known as BEXXAR®) and ibritumomab tiuxetan (also known as ZEVALIN®). Those of ordinary skill are capable of designing antibodies that are conjugated to radioactive isotopes using known strategies such as those used to conjugate iodine-131 in tositumomab and to conjugate yttrium-90 or indium-111 to ibritumomab (see, for example, U.S. Pat. No. 6,565,827 & 7,422,739, which are incorporated by reference in their entirety).

In some embodiments, the immunotherapeutic is an immunoconjugate, and the homodimeric antibody is conjugated to a pharmaceutical agent. In some specific embodiments, the homodimeric antibody is conjugated to a moiety selected from a calicheamicin, camptothecin, deruxtecan, doxorubicin, emtansine, exatecan, irinotecan, maleimidocaproyl monomethyl auristatin F, mertansine (DM1), monomethyl auristatin F, paclitaxel, PE38, pyrrolobenzodiazepine, SN-38, and vedotin.

In some embodiments, the homodimeric antibody is a homodimer of anetumab ravtansine, aprutumab ixadotin, azintuxizumab vedotin, belantamab mafodotin, brentuximab vedotin, camidanlumab tesirine, cantuzumab mertansine, cantuzumab ravtansine, cbr96-doxorubicin immunoconjugate, cofetuzumab pelidotin, coltuximab ravtansine, denintuzumab mafodotin, depatuxizumab mafodotin, enapotamab vedotin, enfortumab vedotin, gemtuzumab ozogamicin, glembatumumab vedotin, iladatuzumab vedotin, indatuximab ravtansine, indusatumab vedotin, inotuzumab ozogamicin, ladiratuzumab vedotin, laprituximab emtansine, lifastuzumab vedotin, loncastuximab tesirine, lorvotuzumab mertansine, losatuxizumab vedotin, mirvetuximab soravtansine, moxetumomab pasudotox, naratuximab emtansine, pinatuzumab vedotin, polatuzumab vedotin, rovalpituzumab tesirine, sacituzumab govitecan, samrotamab vedotin, sirtratumab vedotin, sofituzumab vedotin, taplitumomab paptox, telisotuzumab vedotin, tisotumab vedotin, trastuzumab duocarmazine, trastuzumab emtansine, vadastuximab talirine, vandortuzumab vedotin, vorsetuzumab mafodotin, or trastuzumab deruxtecan, each of which are antibody-drug conjugates. Homodimeric versions of the foregoing antibodies may be manufactured, for example, with the SATP/SATA and sulfo-SMCC/SMCC cross-linking strategy as described herein.

Examples of antibodies conjugated to pharmaceutical agents include gemtuzumab ozogamicin (also known as MYLOTARG®) and trastuzumab emtansine (also known as KADCYLA®). Those of ordinary skill are capable of designing antibodies that are conjugated to pharmaceutical agents using known strategies such as those used to conjugate calicheamicin to gemtuzumab and emtansine to trastuzumab (see, for example, U.S. Pat. No. 5,877,296 & 8,088,387, which are incorporated by reference in their entirety).

In some embodiments, a monomeric antibody that consists of the IgG antibody has a reference efficacy against the cancer; the immunotherapeutic has an improved efficacy against the cancer; the reference efficacy and the improved efficacy are determined by an in vitro cytotoxicity assay on cells that express the cancer-associated antigen; and the improved efficacy is more than 100 percent more effective per mole than the reference efficacy. The in vitro cytotoxicity assay may measure cytotoxicity against cancer cells such as an immortalized cell line of the cancer cells, which cytotoxicity is optionally mediated by leukocytes of the in vitro cytotoxicity assay. The leukocytes may be, for example, NK-92 cells that are modified to express the Fc receptor.

In some embodiments, the homodimeric antibody is conjugated to a radioactive isotope or pharmaceutical agent; a monomeric antibody has a reference efficacy against the cancer; the immunotherapeutic has an improved efficacy against the cancer; the monomeric antibody consists of (1) the IgG antibody, (2) the radioactive isotope or pharmaceutical agent, and (3) a linker that links the radioactive isotope or pharmaceutical agent to the IgG antibody; the reference efficacy and the improved efficacy are determined by an in vitro cytotoxicity assay on cells that express the cancer-associated antigen; and the improved efficacy is more than 100 percent more effective per mole than the reference efficacy. The in vitro cytotoxicity assay may measure cytotoxicity against cancer cells such as an immortalized cell line of the cancer cells.

In some embodiments, a monomeric antibody that consists of the IgG antibody has a reference efficacy against the cancer; the immunotherapeutic has an improved efficacy against the cancer; the reference efficacy and the improved efficacy are determined by one or more clinical trials; and the improved efficacy is more than 100 percent more effective per mole than the reference efficacy. In some specific embodiments, efficacy is determined by overall survival. In some specific embodiments, efficacy is determined by progression-free survival.

In some embodiments, the homodimeric antibody is conjugated to a radioactive isotope or pharmaceutical agent; a monomeric antibody has a reference efficacy against the cancer; the monomeric antibody consists of (1) the IgG antibody, (2) the radioactive isotope or pharmaceutical agent, and (3) a linker that links the radioactive isotope or pharmaceutical agent to the IgG antibody; the immunotherapeutic has an improved efficacy against the cancer; the reference efficacy and the improved efficacy are determined by one or more clinical trials; and the improved efficacy is more than 100 percent more effective per mole than the reference efficacy. In some specific embodiments, efficacy is determined by overall survival. In some specific embodiments, efficacy is determined by progression-free survival.

In some embodiments, the improved efficacy is more than 150 percent more effective per mole than the reference efficacy. In some specific embodiments, the improved efficacy is more than 200 percent more effective per mole than the reference efficacy.

In some embodiments, a monomeric antibody that consists of the IgG antibody has a reference infusion time, which is an amount of time necessary to infuse an effective amount of the monomeric antibody to treat the cancer; the immunotherapeutic has a shorter infusion time, which is an amount of time necessary to infuse the effective amount of the immunotherapeutic to treat the cancer; and the shorter infusion time is at least 30 minutes shorter than the reference infusion time (such as at least one hour shorter). In some specific embodiments, the shorter infusion time is shorter than the reference infusion time because the immunotherapeutic has a superior efficacy relative to the monomeric antibody. In some very specific embodiments, the shorter infusion time is shorter than the reference infusion time because the immunotherapeutic has a superior efficacy per mole relative to the monomeric antibody. In some specific embodiments, the shorter infusion time is shorter than the reference infusion time because formulations comprising the immunotherapeutic have a greater mass/volume concentration relative to formulations comprising the monomeric antibody. Immunotherapeutics of this disclosure such as homodimeric IgG antibodies may allow for increased mass/volume concentrations relative to monomeric IgG antibodies, for example, because homodimeric IgG antibodies have molecular weights that are approximately double that of monomeric IgG antibodies.

In some embodiments, the homodimeric antibody is conjugated to a radioactive isotope or pharmaceutical agent; a monomeric antibody has a reference infusion time, which is an amount of time necessary to infuse an effective amount of the monomeric antibody to treat the cancer; the monomeric antibody consists of (1) the IgG antibody, (2) the radioactive isotope or pharmaceutical agent, and (3) a linker that links the radioactive isotope or pharmaceutical agent to the IgG antibody; the immunotherapeutic has a shorter infusion time, which is an amount of time necessary to infuse the effective amount of the immunotherapeutic to treat the cancer; and the shorter infusion time is at least 30 minutes shorter than the reference infusion time (such as at least one hour shorter). In some specific embodiments, the shorter infusion time is shorter than the reference infusion time because the immunotherapeutic has a superior efficacy relative to the monomeric antibody. In some very specific embodiments, the shorter infusion time is shorter than the reference infusion time because the immunotherapeutic has a superior efficacy per mole relative to the monomeric antibody. In some specific embodiments, the shorter infusion time is shorter than the reference infusion time because formulations comprising the immunotherapeutic have a greater mass/volume concentration relative to formulations comprising the monomeric antibody.

In some embodiments, the immunotherapeutic has an infusion time of no greater than 4 hours. In some specific embodiments, the immunotherapeutic has an infusion time of no greater than 3 hours. In some even more specific embodiments, the immunotherapeutic has an infusion time of no greater than 2 hours. In some very specific embodiments, the immunotherapeutic has an infusion time of no greater than 1 hour.

In some embodiments, each antigen-binding site of the IgG antibody comprises (1) a first variable domain that comprises a VH CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 5, a VH CDR2 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 consecutive amino acids set forth in SEQ ID NO: 6, and a VH CDR3 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 7; and (2) a second variable domain that comprises a VL CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 8, a VL CDR2 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, or 7 consecutive amino acids set forth in SEQ ID NO: 9, and a VL CDR3 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 10. Homodimeric antibodies in which each antigen-binding site comprises the first variable domain and second variable domain as set forth in this paragraph are generally capable of specifically binding Sp17 with high affinity.

In some embodiments, each IgG antibody comprises a heavy chain that has at least 90 percent sequence homology with SEQ ID NO: 11 and a light chain that has at least 90 percent sequence homology with SEQ ID NO: 12. Homodimeric antibodies comprising two IgG antibodies that each comprise a heavy chain and a light chain as set forth in this paragraph are generally capable of specifically binding Sp17 with high affinity.

As used in this disclosure, the term “sequence homology” refers to percent “positives” as determined by Standard Protein BLAST® over the full length of a sequence set forth in a SEQ ID NO. Standard Protein BLAST® is available at https://blast.ncbi.nlm.nih.gov/Blast.cgi?PROGRAM=blastp. BLAST® is generally described in Altschul, et al. (1997), “Gapped BLAST and PSI-BLAST: a new generation of protein database search programs”, Nucleic Acids Res. 25:3389-3402, and in Altschul, et al. (2005) “Protein database searches using compositionally adjusted substitution matrices”, FEBS J. 272:5101-5109. As used in this disclosure, the term “sequence identity” refers to the percent of exact matches over the full length of a sequence set forth in a SEQ ID NO.

In some embodiments, the immunotherapeutic comprises a dissociation constant (KD) with the cancer-associated antigen of no greater than 25 nanomolar. In some specific embodiments, the homodimeric antibody has a KD with the cancer-associated antigen of no greater than 10 nanomolar. In some very specific embodiments, the homodimeric antibody has a KD with the cancer-associated antigen of no greater than 2.5 nanomolar. In some embodiments, KD is determined by surface plasmon resonance (such as with a Biacore™ instrument).

In some embodiments, each IgG antibody comprises a human IgG1, IgG2, IgG3, or IgG4 heavy chain constant region and a human kappa or lambda light chain constant region. In some specific embodiments, each IgG antibody comprises a human IgG1 or IgG4 heavy chain constant region and a human kappa or lambda light chain constant region. In some very specific embodiments, each IgG antibody comprises a human IgG1 or IgG4 heavy chain constant region and a human kappa light chain constant region.

In some embodiments, the two IgG antibodies are covalently crosslinked in the homodimeric antibody with an engineered disulfide bond. S119C and S444C are representative mutations to native amino acids that are known to crosslink IgG1 antibodies with high efficiency. The positions of S119C and S444C are defined according to EU numbering as set forth in Kabat. Other suitable native amino acids may be identified by analyzing crystal structures for IgGs, for example, to identify native amino acids that display solvent-accessible surface areas that are greater than the solvent-accessible surface areas of buried native amino acids. Other suitable native amino acids may include, for example, asparagine amino acids that might otherwise be glycosylated. Other suitable native amino acids may include, for example, (1) alanine amino acids that have a greater solvent-accessible surface area than other alanine amino acids of an IgG, (2) serine amino acids, (3) threonine amino acids, (4) aspartate amino acids, (5) glutamate amino acids, (6) asparagine amino acids, (7) glutamine amino acids, (8) histidine amino acids, (8) arginine amino acids, (9) lysine amino acids, (10) methionine amino acids, and (11) tyrosine amino acids; the scope of suitable native amino acids is nevertheless not limiting and even hydrophobic amino acids may be suitable native amino acids if a hydrophobic amino acid displays a significant solvent-accessible surface area.

In some embodiments, the two IgG antibodies are covalently crosslinked in the homodimeric antibody with a synthetic linker. In the case of sulfo-SMCC- and SATP-mediated cross-linking, for example, the synthetic linker would be 1-oxo-S—{N-[4-formyl-cyclohexyl(methyl)]-3,4-dihydro-2,5-dioxo-1H-pyrrol-3-yl}-3-thiopropyl, wherein the carbon atom of the formyl is covalently bound to a primary amine of a first of the two IgG antibodies and the 1-carbon atom of the propyl is bound to a primary amine of a second of the two IgG antibodies.

Various aspects of this disclosure relate to an immunotherapeutic comprising a homodimeric antibody that comprises two IgG antibodies that are covalently crosslinked, wherein each IgG antibody comprises two antigen-binding sites that each specifically bind Sp17 such that the homodimeric antibody comprises exactly four antigen-binding sites that each specifically bind Sp17.

Various aspects of this disclosure relate to an immunotherapeutic comprising a homodimeric antibody and either a radioisotope or a labile pharmaceutical agent, wherein (1) the homodimeric antibody comprises two IgG antibodies that are covalently crosslinked, and (2) each IgG antibody comprises two antigen-binding sites that each specifically bind a cancer-associated antigen such that the homodimeric immunoconjugate comprises exactly four antigen-binding sites that each specifically bind the cancer-associated antigen.

In some embodiments, the immunotherapeutic is an immunoconjugate, and the homodimeric antibody is conjugated to a radioactive isotope. In some specific embodiments, the radioactive isotope is actinium-225, astatine-211, bismuth-212, bismuth-213, copper-67, gallium-68, holmium-166, indium-111, iodine-124, iodine-131, lutetium-177, samarium-153, technetium-99, terbium-149, or yttrium-90. In some very specific embodiments, the radioactive isotope is indium-111, iodine-124, iodine-131, lutetium-177, or yttrium-90.

In some embodiments, the immunotherapeutic is an immunotherapeutic is an immunoconjugate, and the homodimeric antibody is conjugated to a pharmaceutical agent. In some specific embodiments, the homodimeric antibody is conjugated to a moiety selected from a calicheamicin, camptothecin, deruxtecan, doxorubicin, emtansine, exatecan, irinotecan, maleimidocaproyl monomethyl auristatin F, mertansine, monomethyl auristatin F, paclitaxel, PE38, pyrrolobenzodiazepine, SN-38, and vedotin.

In some embodiments, each antigen-binding site comprises: (1) a first variable domain that comprises a VH CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 5, a VH CDR2 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 consecutive amino acids set forth in SEQ ID NO: 6, and a VH CDR3 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 7; and (2) a second variable domain that comprises a VL CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 8, a VL CDR2 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, or 7 consecutive amino acids set forth in SEQ ID NO: 9, and a VL CDR3 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 10.

Various aspects of this disclosure relate to homodimeric antibodies that display high-affinity for Sp17. These antibodies were developed using a Fab phage-display bio-panning strategy on a library generated from the peripheral blood of 120 healthy donors as set forth in Example 1 below. The library included about a trillion different combinations. The best-performing Fab in the library had an immunoglobulin heavy chain variable region (VH) with the nucleotide sequence set forth in SEQ ID NO: 1 and an immunoglobulin light chain variable region (VL) with the nucleotide sequence set forth in SEQ ID NO: 2, which nucleotide sequences are depicted in Table 1 below. The VH amino acid sequence is set forth in SEQ ID NO: 3, and the VL amino acid sequence is set forth in SEQ ID NO: 4. The VH and VL amino acid sequences are depicted in Table 2 below. CDR sequences are set forth in SEQ ID NO: 5-10 and are independently depicted in Table 3 below. One of ordinary skill will recognize that the precise demarcation between CDR and framework regions is blurred at least for some of the CDRs, and the CDRs as set forth in Table 3 and in SEQ ID NO: 5-10 may therefore include one or more amino acids that might be more-appropriately classified as framework rather than CDR.

Nucleotide sequences encoding the variable regions of the best-performing Fab (SEQ ID NO: 1 & 2) were initially cloned into a mouse IgG2a heavy chain gene and a mouse kappa light chain gene to express a chimeric monoclonal antibody (chAB2). The affinity of the chimeric antibody was determined to be about 2 nanomolar by surface plasmon resonance. Immunohistochemical analysis of the chimeric antibody against 33 normal human tissues indicated that the variable regions lack detectable cross-reactivity.

The human variable regions were then cloned into a human IgG4 heavy chain gene and a human kappa light chain gene to produce a human monoclonal antibody (SP17-AB2) suitable for use as a therapeutic antibody. The heavy chain constant region was mutated to include a S228P mutation to reduce non-specific interactions with Fc receptor gamma (FcγR). The full heavy chain has the amino acid sequence set forth in SEQ ID NO: 10, and the full light chain has the amino acid sequence set forth in SEQ ID NO: 11, which are depicted in Table 4 below.

The human variable regions were then cloned into a human IgG1 heavy chain to produce a human monoclonal antibody suitable for use as a therapeutic antibody. The heavy chain constant region of one clone was mutated to include a S444C mutation to crosslink the IgG1 to form a homodimeric antibody, and an additional mutation F405L was introduced to produce a chimeric antibody as described herein. The heavy chain constant region of a second clone was mutated to include a K409R mutation to produce the chimeric antibody by reducing the hinge regions of the first and second clones to allow half molecules of the first and second clones to recombine as described herein (see, for example, FIG. 1).

Various aspects of this disclosure relate to a homodimeric anti-Sp17 antibody, which comprises the CDRs described above or which comprises sequence homology (or sequence identity) with the VH and VL variable regions that comprise the CDRs as described above.

In all embodiments, each IgG antibody comprises two variable domains. The two variable domains include a heavy chain variable region and a light chain variable region. In some specific embodiments, the heavy chain variable region has a percent sequence homology (or sequence identity) with SEQ ID NO: 5, 6, and 7, and the light chain variable region has a percent sequence homology (or sequence identity) with SEQ ID NO: 8, 9, and 10. In some very specific embodiments, the heavy chain variable region has a percent sequence homology (or sequence identity) with SEQ ID NO: 3, and the light chain variable region has a percent sequence homology (or sequence identity) with SEQ ID NO: 4.

In some embodiments, each IgG antibody comprises (1) a first variable domain that comprises a VH CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 5, a VH CDR2 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 consecutive amino acids set forth in SEQ ID NO: 6, and a VH CDR3 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 7; and (2) a second variable domain that comprises a VL CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 8, a VL CDR2 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, or 7 consecutive amino acids set forth in SEQ ID NO: 9, and a VL CDR3 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 10.

In some embodiments, each IgG antibody comprises four variable domains, wherein the antibody comprises (1) a third variable domain that comprises a VH CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 5, a VH CDR2 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 consecutive amino acids set forth in SEQ ID NO: 6, and a VH CDR3 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 7; and (2) a fourth variable domain that comprises a VL CDR1 region comprising an amino acid sequence that is identical to at least 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 consecutive amino acids set forth in SEQ ID NO: 8, a VL CDR2 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, or 7 consecutive amino acids set forth in SEQ ID NO: 9, and a VL CDR3 region comprising an amino acid sequence that is identical to at least 3, 4, 5, 6, 7, 8, 9, or 10 consecutive amino acids set forth in SEQ ID NO: 10. Such antibodies include, for example, IgG antibodies that bind Sp17.

In some embodiments, one or more of VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3 comprise one or more conservative mutations. Conservative mutations are known in the art and include, for example, threonine to serine, isoleucine to valine or leucine, tyrosine to phenylalanine, aspartate to glutamate, asparagine to glutamine, arginine to lysine, and like substitutions. In this disclosure, a conservative mutation is a “positive” match in Standard Protein BLAST® that is not an identity.

In some embodiments, each IgG antibody comprises two variable domains, wherein: each IgG antibody comprises a first variable domain that comprises an amino acid sequence that has at least 90 percent sequence homology with SEQ ID NO: 3; each IgG antibody comprises a second variable domain that comprises an amino acid sequence that has at least 90 percent sequence homology with SEQ ID NO: 4; and each IgG antibody binds human Sp17. In some specific embodiments, the first variable domain comprises an amino acid sequence that has at least 90 percent sequence identity with SEQ ID NO: 3; the second variable domain comprises an amino acid sequence that has at least 90 percent sequence identity with SEQ ID NO: 4; and the antibody binds human Sp17.

SEQ ID NO: 3 is the VH amino acid sequence, which includes VH CDR1, VH CDR2, VH CDR3, and framework regions. In some embodiments, the VH amino acid sequence comprises mutations relative to SEQ ID NO: 3 such that the VH amino acid sequence has at least 90 percent sequence homology with SEQ ID NO: 3 but less than 100 percent sequence homology. In some specific embodiments, the VH amino acid sequence comprises mutations relative to SEQ ID NO: 3 such that the VH amino acid sequence has at least 90 percent sequence identity with SEQ ID NO: 3 but less than 100 percent sequence identity.

SEQ ID NO: 4 is the VL amino acid sequence, which includes VL CDR1, VL CDR2, VL CDR3, and framework regions. In some embodiments, the VL amino acid sequence comprises mutations relative to SEQ ID NO: 4 such that the VL amino acid sequence has at least 90 percent sequence homology with SEQ ID NO: 4 but less than 100 percent sequence homology. In some specific embodiments, the VL amino acid sequence comprises mutations relative to SEQ ID NO: 4 such that the VL amino acid sequence has at least 90 percent sequence identity with SEQ ID NO: 4 but less than 100 percent sequence identity.

Mutations to the VH and/or VL amino acid sequences may be engineered, for example, to tune the avidity of an antibody to the Sp17 antigen, to modulate expression or glycosylation, and/or for other purposes.

In some embodiments, the first variable domain comprises an amino acid sequence that has at least 95 percent sequence homology with SEQ ID NO: 3. In some specific embodiments, the first variable domain comprises an amino acid sequence that has at least 97 percent sequence homology with SEQ ID NO: 3. In some even more specific embodiments, the first variable domain comprises an amino acid sequence that has at least 98 percent sequence homology with SEQ ID NO: 3. In some very specific embodiments, the first variable domain comprises an amino acid sequence that has at least 99 percent sequence homology with SEQ ID NO: 3.

In some embodiments, the first variable domain comprises an amino acid sequence that has at least 95 percent sequence identity with SEQ ID NO: 3. In some specific embodiments, the first variable domain comprises an amino acid sequence that has at least 97 percent sequence identity with SEQ ID NO: 3. In some even more specific embodiments, the first variable domain comprises an amino acid sequence that has at least 98 percent sequence identity with SEQ ID NO: 3. In some very specific embodiments, the first variable domain comprises an amino acid sequence that has at least 99 percent sequence identity with SEQ ID NO: 3.

In some embodiments, the second variable domain comprises an amino acid sequence that has at least 95 percent sequence homology with SEQ ID NO: 4. In some specific embodiments, the second variable domain comprises an amino acid sequence that has at least 97 percent sequence homology with SEQ ID NO: 4. In some even more specific embodiments, the second variable domain comprises an amino acid sequence that has at least 98 percent sequence homology with SEQ ID NO: 4. In some very specific embodiments, the second variable domain comprises an amino acid sequence that has at least 99 percent sequence homology with SEQ ID NO: 4.

In some embodiments, the second variable domain comprises an amino acid sequence that has at least 95 percent sequence identity with SEQ ID NO: 4. In some specific embodiments, the second variable domain comprises an amino acid sequence that has at least 97 percent sequence identity with SEQ ID NO: 4. In some even more specific embodiments, the second variable domain comprises an amino acid sequence that has at least 98 percent sequence identity with SEQ ID NO: 4. In some very specific embodiments, the second variable domain comprises an amino acid sequence that has at least 99 percent sequence identity with SEQ ID NO: 4.

In some embodiments, each IgG antibody comprises four variable domains, wherein the antibody comprises (1) a third variable domain that comprises an amino acid sequence that has at least 90 percent sequence homology with SEQ ID NO: 3 (such as at least 95, 97, 98, or 99 percent sequence homology); and (2) a fourth variable domain that comprises an amino acid sequence that has at least 90 percent sequence homology with SEQ ID NO: 4 (such as at least 95, 97, 98, or 99 percent sequence homology). In some specific embodiments, the third variable domain comprises an amino acid sequence that has at least 90 percent sequence identity with SEQ ID NO: 3 (such as at least 95, 97, 98, or 99 percent sequence homology), and the fourth variable domain comprises an amino acid sequence that has at least 90 percent sequence identity with SEQ ID NO: 4 (such as at least 95, 97, 98, or 99 percent sequence identity).

In some embodiments, the homodimeric antibody has a KD with human Sp17 of no greater than 25 nanomolar. In some specific embodiments, the homodimeric antibody has a KD with human Sp17 of no greater than 10 nanomolar. In some very specific embodiments, the homodimeric antibody has a KD with human Sp17 of no greater than 2.5 nanomolar.

In some embodiments, each IgG antibody has a heavy chain that has at least 90 percent sequence homology with SEQ ID NO: 11. In some specific embodiments, each IgG antibody has a heavy chain that has at least 95 percent sequence homology with SEQ ID NO: 11. In some even more specific embodiments, each IgG antibody has a heavy chain that has at least 98 percent sequence homology with SEQ ID NO: 11. In some very specific embodiments, each IgG antibody has a heavy chain that has at least 99 percent sequence homology with SEQ ID NO: 11.

In some embodiments, each IgG antibody has a heavy chain that has at least 90 percent sequence identity with SEQ ID NO: 11. In some specific embodiments, each IgG antibody has a heavy chain that has at least 95 percent sequence identity with SEQ ID NO: 11. In some even more specific embodiments, each IgG antibody has a heavy chain that has at least 98 percent sequence identity with SEQ ID NO: 11. In some very specific embodiments, each IgG antibody has a heavy chain that has at least 99 percent sequence identity with SEQ ID NO: 11.

In some embodiments, each IgG antibody has a light chain that has at least 90 percent sequence homology with SEQ ID NO: 12. In some specific embodiments, each IgG antibody has a light chain that has at least 95 percent sequence homology with SEQ ID NO: 12. In some even more specific embodiments, each IgG antibody has a light chain that has at least 98 percent sequence homology with SEQ ID NO: 12. In some very specific embodiments, each IgG antibody has a light chain that has at least 99 percent sequence homology with SEQ ID NO: 12.

In some embodiments, each IgG antibody has a light chain that has at least 90 percent sequence identity with SEQ ID NO: 12. In some specific embodiments, each IgG antibody has a light chain that has at least 95 percent sequence identity with SEQ ID NO: 12. In some even more specific embodiments, each IgG antibody has a light chain that has at least 98 percent sequence identity with SEQ ID NO: 12. In some very specific embodiments, each IgG antibody has a light chain that has at least 99 percent sequence identity with SEQ ID NO: 12.

In some embodiments, each IgG antibody has (1) a heavy chain that has at least 90 percent sequence homology with SEQ ID NO: 11, and (2) a light chain that has at least 90 percent sequence homology with SEQ ID NO: 12. In some specific embodiments, each IgG antibody has (1) a heavy chain that has at least 95 percent sequence homology with SEQ ID NO: 11, and (2) a light chain that has at least 95 percent sequence homology with SEQ ID NO: 12. In some even more specific embodiments, each IgG antibody has (1) a heavy chain that has at least 98 percent sequence homology with SEQ ID NO: 11, and (2) a light chain that has at least 98 percent sequence homology with SEQ ID NO: 12. In some very specific embodiments, each IgG antibody has (1) a heavy chain that has at least 99 percent sequence homology with SEQ ID NO: 11, and (2) a light chain that has at least 99 percent sequence homology with SEQ ID NO: 12.

In some embodiments, each IgG antibody has (1) a heavy chain that has at least 90 percent sequence identity with SEQ ID NO: 11, and (2) a light chain that has at least 90 percent sequence identity with SEQ ID NO: 12. In some specific embodiments, each IgG antibody has (1) a heavy chain that has at least 95 percent sequence identity with SEQ ID NO: 11, and (2) a light chain that has at least 95 percent sequence identity with SEQ ID NO: 12. In some even more specific embodiments, each IgG antibody has (1) a heavy chain that has at least 98 percent sequence identity with SEQ ID NO: 11, and (2) a light chain that has at least 98 percent sequence identity with SEQ ID NO: 12. In some very specific embodiments, each IgG antibody has (1) a heavy chain that has at least 99 percent sequence identity with SEQ ID NO: 11, and (2) a light chain that has at least 99 percent sequence identity with SEQ ID NO: 12.

In some embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 90 percent sequence homology with SEQ ID NO: 11, and each of the two light chains has at least 90 percent sequence homology with SEQ ID NO: 12. In some specific embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 95 percent sequence homology with SEQ ID NO: 11, and each of the two light chains has at least 95 percent sequence homology with SEQ ID NO: 12. In some even more specific embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 98 percent sequence homology with SEQ ID NO: 11, and each of the two light chains has at least 98 percent sequence homology with SEQ ID NO: 12. In some very specific embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 99 percent sequence homology with SEQ ID NO: 11, and each of the two light chains has at least 99 percent sequence homology with SEQ ID NO: 12.

In some embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 90 percent sequence identity with SEQ ID NO: 11, and each of the two light chains has at least 90 percent sequence identity with SEQ ID NO: 12. In some specific embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 95 percent sequence identity with SEQ ID NO: 11, and each of the two light chains has at least 95 percent sequence identity with SEQ ID NO: 12. In some even more specific embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 98 percent sequence identity with SEQ ID NO: 11, and each of the two light chains has at least 98 percent sequence identity with SEQ ID NO: 12. In some very specific embodiments, each IgG antibody comprises two heavy chains and two light chains, wherein each of the two heavy chains has at least 99 percent sequence identity with SEQ ID NO: 11, and each of the two light chains has at least 99 percent sequence identity with SEQ ID NO: 12.

In some embodiments, each IgG antibody comprises at least four variable domains, wherein: the first and second variable domains are paired in the antibody such that the first and second variable domains bind a first cancer-associated antigen, and the antibody comprises a third variable domain and a fourth variable domain that are paired in the antibody such that the third and fourth variable domains bind a second cancer-associated antigen. Such antibodies include, for example, IgG-like bispecific antibodies. Examples of bispecific antibodies include amivantamab, glofitamab, talquetamab, and teclistamab. Those of ordinary skill in the art are capable of manufacturing homodimeric antibodies that comprise bispecific antibodies, for example, by crosslinking known bispecific antibodies.

In this disclosure, the term “paired” refers a spatial proximity and orientation between VH and VL regions that allow the VH and VL regions to simultaneously bind an epitope. VH and VL regions may be paired, for example, in a Fab by quaternary structure that includes one or more disulfide bonds and non-covalent interactions between the heavy chain constant domain CH1 and the light chain constant domain CL.

In some embodiments, each IgG antibody is a bispecific antibody that comprises CDRs that have sequence homology with the amino acid sequences set forth in SEQ ID NO: 3-6. A bispecific antibody may comprise amino acid sequences that have, for example, at least 90, 95, 97, 98, or 99 percent sequence homology with the sequences set forth in SEQ ID NO: 3-6 or at least 90, 95, 97, 98, or 99 percent sequence identity with the sequences set forth in SEQ ID NO: 3-6.

Various aspects of this disclosure relate to a pharmaceutical composition comprising an immunotherapeutic as described anywhere in this disclosure and a pharmaceutically acceptable carrier. Suitable pharmaceutically acceptable carriers generally include water with dissolved solutes that buffer pH and provide metal cations and an ionic strength that stabilize an immunotherapeutic of this disclosure. Such formulations are generally sterile, and the selection and preparation of such pharmaceutically acceptable carriers are well known. Solid formats including lyophilized therapeutics generally include, for example, metal cations, anions, and optionally polyols such as sugars (for example, trehalose or glucose) that stabilize the therapeutic in the solid phase and during its reconstitution into an aqueous format. General guidance on selecting pharmaceutically acceptable carriers is available, for example, in REMINGTON: THE SCIENCE AND PRACTICE OF PHARMACY, 22nd edition (Allen Jr, Loyd V., editor) Pharmaceutical Press, 2012, and the skilled practitioner will also look to the formulations of IgG antibodies described in this disclosure as well as other existing therapeutics in selecting a pharmaceutically acceptable carrier. Such guidance is generally available in the scientific literature and on existing product labels.

In some embodiments, the pharmaceutical composition is suitable for administration to a subject. In some specific embodiments, the pharmaceutical composition is suitable for administration to a human patient. In some very specific embodiments, the pharmaceutical composition is suitable for intravenous administration to a human patient.

Various aspects of this disclosure relate to a kit, comprising (1) a hermetically-sealed container that contains the pharmaceutical composition as described anywhere in this specification and (2) instructions for use of the pharmaceutical composition.

Various aspects of this disclosure relate to a medical device, comprising the pharmaceutical composition as described anywhere in this specification. In some embodiments, the medical device is a syringe, a venous cannula, or a drug-eluting implant.

Various aspects of this disclosure relate to a method of treating or preventing cancer in a subject, comprising identifying that the subject comprises cells that ectopically express the cancer-associated antigen and administering a pharmaceutical composition as described anywhere in this disclosure. Determining that the subject comprises cells that ectopically express the cancer-associated antigen include, for example, identifying mRNA that encodes the cancer-associated antigen by RT-PCR and identifying expression of the cancer-associated antigen by flow cytometry and/or immunohistochemistry. Such methods may advantageously allow determination that a cancer cell expresses the cancer-associated antigen, for example, based upon the prior selection of one or more cancer cells for analysis or based upon the co-identification of expression of the cancer-associated antigen and a cancer phenotype such as the co-expression of the cancer-associated antigen and another cancer antigen.

Various aspects of this disclosure relate to a method to modulate cells that express the cancer-associated antigen in a human subject, comprising administering the immunotherapeutic to the human subject, wherein the immunotherapeutic is a homodimeric antibody that comprises two IgG antibodies as described anywhere in this disclosure. In some embodiments, the method is a method of treating or preventing cancer in a human subject. In some specific embodiments, the method is a method of treating or preventing cancer in a human subject, the human subject presents with cancer, and at least a portion of the cells that express the cancer-associated antigen are cancer cells.

In some embodiments the immunotherapeutic is administered at an effective amount that is effective to induce cell death in at least a portion of the cells that express the cancer-associated antigen. In some specific embodiments, the immunotherapeutic comprises an Fc region, and the method induces cell death by Fc-receptor-mediated binding and activation of one or more leukocytes to the cells that express the cancer-associated antigen. In some specific embodiments, the immunotherapeutic is conjugated to a radioactive isotope, and the method induces cell death by emitting radiation within or in proximity to the cells that the cancer-associated antigen. In some specific embodiments, the immunotherapeutic is conjugated to a pharmaceutical agent, the pharmaceutical agent is cytotoxic, and the method induces cell death by releasing the pharmaceutical agent within or in proximity to the cells that express the cancer-associated antigen. In some very specific embodiments, the immunotherapeutic is conjugated to a pharmaceutical agent by a labile linker, the pharmaceutical agent is cytotoxic, and the method induces cell death by releasing the pharmaceutical agent within or in proximity to the cells that express the cancer-associated antigen.

In some embodiments, the subject is a mammal. In some specific embodiments, the subject is a rodent, lagomorph, feline, canine, porcine, ovine, caprine, lama, bovine, equine, or primate. In some very specific embodiments, the subject is a human patient.

In some embodiments, the subject is male or female. In some specific embodiments, the subject is female. In some specific embodiments, the subject is male.

In some embodiments, the subject presents with ectopic expression of the cancer-associated antigen. In some specific embodiments, the subject presents with cancer, and cells of the cancer express the cancer-associated antigen.

In some embodiments, the method comprises identifying that the subject comprises cells that express the cancer-associated antigen.

In some embodiments, the method comprises identifying that the subject comprises cells that express the cancer-associated antigen, wherein the cells that express the cancer-associated antigen comprise leukocytes, and the cancer is a lymphoma, leukemia, or myeloma. In some specific embodiments, the method comprises identifying that the subject comprises cells that express the cancer-associated antigen, wherein the cells that express the cancer-associated antigen comprise plasma cells, and the cancer is multiple myeloma. In some specific embodiments, the method comprises identifying that the subject comprises cells that express the cancer-associated antigen, wherein the cells that express the cancer-associated antigen comprise lymphocytes, and the cancer is lymphoma. In some specific embodiments, the method comprises identifying that the subject comprises cells that express the cancer-associated antigen, wherein the cells that express the cancer-associated antigen comprise ovarian cells, and the cancer is ovarian cancer. In some specific embodiments, the method comprises identifying that the subject comprises cells that express the cancer-associated antigen, wherein the cells that express the cancer-associated antigen comprise lung epithelial cells, and the cancer is non-small cell lung cancer.

In some embodiments, the method comprises identifying that a tissue sample of the human subject comprises either RNA encoding the cancer-associated antigen or a protein that includes the cancer-associated antigen prior to the administering.

In some embodiments, the tissue sample is a blood sample.

In some embodiments, the tissue sample is a biopsy. In some specific embodiments, the tissue sample is a tumor biopsy. In some very specific embodiments, the tissue sample is a bone marrow biopsy. In some very specific embodiments, the tissue sample is an ovarian biopsy. In some very specific embodiments, the tissue sample is a lung biopsy.

In some embodiments, the method comprises identifying that the tissue sample comprises a cancer biomarker, wherein the cancer biomarker is neither RNA encoding the cancer-associated antigen nor the cancer-associated antigen.

In some embodiments, the cells that express the cancer-associated antigen comprise leukocytes, and the cancer is a lymphoma, leukemia, or myeloma. In some specific embodiments, the cells that express the cancer-associated antigen comprise leukocytes, and the cancer is multiple myeloma or lymphoma. In some very specific embodiments, the cells that express the cancer-associated antigen comprise plasma cells, and the cancer is multiple myeloma. In some very specific embodiments, the cells that express the cancer-associated antigen comprise lymphocytes, and the cancer is lymphoma.

In some embodiments, the cells that express the cancer-associated antigen comprise ovarian cells, and the cancer is ovarian cancer.

In some embodiments, the cells that express the cancer-associated antigen comprise lung epithelial cells, and the cancer is non-small cell lung cancer.

In some embodiments, the administering is selected from intravenous, intramuscular, subcutaneous, intradermal, intraocular, parenteral, intraperitoneal, intrathecal, intralesional, and intratumoral administration. In some specific embodiments, the administering is intravenous administration.

Having described various features of this disclosure both generally and specifically in the preceding detailed description, the following exemplification provides specific examples of the preparation of the subject matter described herein. By way of these examples, and in the context of the preceding detailed description, the skilled person will immediately recognize variations to the methods set forth in the examples. The following exemplification is illustrative only and shall not limit this disclosure or any patent claim that matures from this disclosure. Any patent claim that matures from this disclosure shall instead be limited by the explicit features recited in the claim in the context of its claim dependency and according to conventional principles of claim construction as applied in view of this disclosure.

EXEMPLIFICATION
Example 1. Identification of Human Variable Regions for an Anti-Sp17 Antibody Based on Human Diversity

A Fab phage display library was constructed from peripheral blood obtained from 120 healthy human donors. Briefly, this library was constructed by randomly combining nucleotide sequences encoding immunoglobulin heavy chain variable regions with nucleotide sequences encoding immunoglobulin light chain variable regions. The library had a diversity of approximately 1 trillion combinations. Bio-panning of the library identified twelve positive colonies, and nucleotide sequencing of the colonies identified two distinct clones. A single clone was identified as binding Sp17 by ELISA. The nucleotide sequences of the human VH and VL regions of the antibody are set forth in Table 1 below. The variable regions have the amino acid sequences set forth in Table 2 below and the CDRs set forth in Table 3 below.

TABLE 1

Nucleotide sequences of anti-Sp17 VH and VL regions identified by bio-panning

a Fab phage-display library of ~1 trillion human Fabs

developed from peripheral blood samples of 120 human subjects

SEQ ID

Sequence 10 20 30 40

NO.
Region
12345678901234567890123456789012345678901234567890

1
VH
CAGGTACAGCTGCAGCAGTCAGGGGCTGAGGTGAAGAAGCCTGGGTCCTC

GGTGAAGGTCTCCTGCAAGGCTTCTGGAGGCACCTTCAGCAGCTATGCTA

TCAGCTGGGTGCGACAGGCCCCTGGACAAGGGCTTGAGTGGATGGGAAGG

ATCATCCCTATCCTTGGTATAGCAAACTACGCACAGAAGTTCCAGGGCAG

AGTCACGATTACCGCGGACAAATCCACGAGCACAGCCTACATGGAGCTGA

GCAGCCTGAGATCTGAGGACACGGCCGTGTATTACTGTGCGAGACCCTCC

GAAGAGGTGGTAGCTGCTTACGGTGCTTTTGATATCTGGGGCCAAGGGAC

CACGGTCACCGTCTCAAGC

2
VL
GAAATTGTGCTGACTCAGTCTCCACTCTCCCTGCCCGTCAGACCTGGGGA

GCCGGCCTCCATCTCCTGCAGGGCTAGTCAGAGCCTCCTGCGTAGTGACG

GATTCAACTACTTGGATTGGTACCTGCAGAAGCCAGGGCAGTCTCCACAG

CTCCTGGTCTATTTGGGTTCTAATCGGGCCTCCGGGGTCCCTGACAGGTT

CAGTGGCAGTGGATCAGGCACAGATTTTACACTGAAAATCAGCAGAGTGG

AGGCTGAGGATGTTGGGGTTTATTACTGCATGCAAGCTGTACAAACTCCG

TACATTTTTGGCCAGGGGACCAAGCTGGAGATCAAA

TABLE 2

Amino acid sequences of anti-Sp17 VH and VL regions identified by bio-panning

a Fab phage-display library of ~1 trillion human Fabs

developed from peripheral blood samples of 120 human subjects

SEQ ID

Sequence 10 20 30 40

NO.
Region
12345678901234567890123456789012345678901234567890

3
VH
QVQLQQSGAEVKKPGSSVKVSCKASGGTFSSYAISWVRQAPGQGLEWMGR

IIPILGIANYAQKFQGRVTITADKSTSTAYMELSSLRSEDTAVYYCARPS

EEVVAAYGAFDIWGQGTTVTVSS

4
VL
EIVLTQSPLSLPVRPGEPASISCRASQSLLRSDGFNYLDWYLQKPGQSPQ

LLVYLGSNRASGVPDRFSGSGSGTDFTLKISRVEAEDVGVYYCMQAVQTP

YIFGQGTKLEIK

TABLE 3

Amino acid sequences of CDRs of the VH and VL regions

identified by bio-panning a Fab phage-display library of ~1

trillion human Fabs developed from peripheral blood samples

of 120 human subject

Sequence 10

SEQ ID NO.
Region
12345678901234567

5
VH CDR1
GGTFSSYAIS

6
VH CDR2
RIIPILGIANYAQKFQG

7
VH CDR3
ARPSEEVVAAYGAFDI

8
VL CDR1
RASQSLLRSDGFNYLD

9
VL CDR2
LGSNRAS

10
VL CDR3
MQAVQTPYIF

Example 2. Engineering a Mouse-Human Chimeric Anti-Sp17 IgG2a/KAPPA Monoclonal Antibody

The nucleotide sequences encoding the VH and VL regions of Example 1 were cloned into a mouse IgG2a heavy chain gene and a mouse kappa light chain gene, respectively, and expressed in CHO—S cells to produce a mouse-human chimeric antibody, which was named chAB2. Successful generation of the antibody was confirmed by SDS-PAGE and western blotting using anti-mouse heavy and light chain antibodies and recombinant Sp17 protein (FIGS. 2 & 3). The chAB2 antibody was reactive to mouse surface Sp17 protein expressed on the mouse ovarian cancer cell line ID8 (FIG. 4). HPLC of the chAB2 antibody preparation showed 93 percent purity (FIG. 5). Surface plasmon resonance with a Biacore™ T200 was used to determine a KD for chAB2 and Sp17 of 2.073 nanomolar (FIG. 6).

The specificity of the chAB2 antibody for Sp17 was determined with immunohistochemistry on a normal tissue microarray, which consisted of 33 normal tissues obtained from 2-3 human donors per tissue. The normal tissues included brain, eye, adrenal gland, hypophysial, thyroid, parathyroid, tonsil, thymus, spleen, heart, lung, larynx, esophagus, stomach, small intestine, colon, liver, pancreas, salivary gland, kidney, bone, skeletal, skin, peripheral nerve, mesothelial, breast, ovary, endometrium, cervix, testis, and prostate. The chAB2 antibody bound to testis and did not bind to normal tissues.

Example 3. Engineering a Human Anti-Sp17 IgG4/KAPPA Monoclonal Antibody

The VH and VL nucleotide sequences of Example 1 were cloned into a human IgG4 heavy chain gene and a human kappa light chain gene, respectively. A S228P mutation was introduced in the heavy chain to reduce non-specific Fc receptor gamma binding. The resultant antibody was named SP17-AB2. Successful cloning was confirmed by sequence analysis. The amino acid sequences of the heavy chain and light chain are shown in Table 4, and the S228P mutation is underlined in SEQ ID NO: 11. Successful expression of the SP17-AB2 antibody was confirmed by SDS-PAGE (FIG. 7), and the ability of the SP17-AB2 antibody to bind Sp17 protein was confirmed by western blot (FIG. 8).

TABLE 4

Amino Acid Sequences of the human anti-Sp17 antibody SP17-AB2

SEQ ID

Sequence 10 20 30 40

NO.
Region
12345678901234567890123456789012345678901234567890

11
Full
MDMRVPAQLLGLLLLWLRGARCQVQLQQSGAEVKKPGSSVKVSCKASGGT

Heavy
FSSYAISWVRQAPGQGLEWMGRIIPILGIANYAQKFQGRVTITADKSTST

Chain
AYMELSSLRSEDTAVYYCARPSEEVVAAYGAFDIWGQGTTVTVSSASTKG

PSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPA

VLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVESKYGPP

CPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSQEDPEVQF

NWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQDWLNGKEYKCKVSN

KGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQVSLTCLVKGFYPS

DIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSRWQEGNVFSC

SVMHEALHNHYTQKSLSLSLGK

12
Full
MDMRVPAQLLGLLLLWLRGARCEIVLTQSPLSLPVRPGEPASISCRASQS

Light
LLRSDGFNYLDWYLQKPGQSPQLLVYLGSNRASGVPDRFSGSGSGTDFTL

Chain
KISRVEAEDVGVYYCMQAVQTPYIFGQGTKLEIKRTVAAPSVFIFPPSDE

QLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTY

SLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC

13
Signal
MDMRVPAQLLGLLLLWLRGARC

Peptide

Example 4. Methods to Prepare Homodimeric Antibodies that are Crosslinked with a Disulfide Bond

The VH and VL nucleotide sequences of Example 1 were cloned into a human IgG1 heavy chain gene and a human kappa light chain gene, respectively.

A first IgG1 comprising F405L and S444C mutations was cloned, expressed, and purified. The positions of F405L and S444C are defined according to EU numbering as set forth in Kabat. An SDS-PAGE analysis of the first IgG1 is shown in FIG. 9A, in which lane 1 corresponds to 1 microgram of the first IgG1 loaded under non-reducing conditions, lane 7 corresponds to 1 microgram of an IgG standard loaded under non-reducing conditions, lane 8 corresponds to a molecular weight standard, lane 9 corresponds to 2 micrograms of the first IgG1 loaded under reducing conditions, and lane 15 corresponds to 2 micrograms of an IgG standard loaded under reducing conditions. The first IgG1 displayed a purity of about 91.96 percent as determined by liquid chromatography and shown in FIG. 9B.

A second IgG1 comprising a K409R mutation was also cloned, expressed, and purified. The position of K409R is defined according to EU numbering as set forth in Kabat. An SDS-PAGE analysis of the second IgG1 is shown in FIG. 10A, in which lane 6 corresponds to 1 microgram of the second IgG1 loaded under non-reducing conditions, lane 7 corresponds to 1 microgram of an IgG standard loaded under non-reducing conditions, lane 8 corresponds to a molecular weight standard, lane 14 corresponds to 2 micrograms of the second IgG1 loaded under reducing conditions, and lane 15 corresponds to 2 micrograms of an IgG standard loaded under reducing conditions. The second IgG1 displayed a purity of about 92.39 percent as determined by liquid chromatography and shown in FIG. 10B.

The amino acid sequences of the first IgG1 and the second IgG1 were identical except for the F405L and S444C mutations of the first IgG1 and the K409R mutation of the second IgG1.

0.5 milligrams of the first IgG1 in 193.8 microliters and 0.5 milligrams of the second IgG1 in 204.9 microliters were combined, and then 44.3 microliters of 750 millimolar cysteamine was added to result in a reaction mixture with 443 microliters total volume containing 0.5 milligrams of the first IgG1 (about 7.5 millimolar), 0.5 milligrams of the second IgG1 (about 7.5 millimolar), and 75 millimolar cysteamine. The reaction mixture was incubated at 31 degrees Celsius for five hours to selectively reduce the disulfide bonds in the IgG1 hinge regions to allow for dissociation of the IgG1s into half molecules and recombination of the half molecules of the first IgG1 and the second IgG1 into chimeric IgG1s. The F405L and K409R mutations favored dissociation of the half molecules of the first IgG1 and the second IgG1, respectively, and permitted recombination of the half molecules into chimeric IgG1s to drive an equilibrium that favored formation of chimeric IgG1s from half molecules of the first IgG1 and the second IgG1 rather than recombination of the half molecules back into the original first IgG1 and second IgG1.

Following the five hours, the reaction mixture was transferred into dialysis bags with a 10 kilodalton molecular weight cut-off (10 kDa MWCO), and the dialysis bags were transferred into 5 liters of phosphate-buffered saline (PBS) adjusted to a pH of 7.4. The first round of dialysis proceeded for four hours. The dialysis bags were then transferred into a fresh 5 liters of PBS (pH 7.4) and dialyzed overnight at 4 degrees Celsius. The slightly alkaline pH of 7.4 allowed for an equilibrium in which some cysteines of the chimeric IgG1s were deprotonated to allow for spontaneous oxidation of (1) cysteines in the hinge region of the chimeric IgG1 to form disulfide bonds that crosslink half molecules of the first IgG1 and the second IgG1 in the chimeric IgG1 and (2) the S444C cysteines of different chimeric IgG1s to form homodimeric antibodies.

Following dialysis, the reaction mixture was transferred into microcentrifuge tubes, and 100 microliters of 100 millimolar cysteine was added to the reaction mixture to block remaining free cysteines. The blocked reaction mixture was then transferred back into dialysis bags with a 10 kDa MWCO, and the dialysis bags were transferred into 5 liters of 20 millimolar phosphate buffer (PB) adjusted to a pH of 6.0. The first round of dialysis proceeded for four hours, and then the dialysis bags were transferred into a fresh 5 liters of PB (pH 6.0) for a second four-hour round of dialysis.

An SDS-PAGE analysis of the reaction mixture is shown in FIG. 11A, in which lane 3 corresponds to 1 microgram of protein from the reaction mixture loaded under non-reducing conditions, lane 7 corresponds to 1 microgram of an IgG standard loaded under non-reducing conditions, lane 8 corresponds to a molecular weight standard, lane 11 corresponds to 2 micrograms of protein from the reaction mixture loaded under reducing conditions, and lane 15 corresponds to 2 micrograms of an IgG standard loaded under reducing conditions. The arrow in FIG. 11A depicts a protein band that displays a molecular weight that corresponds to the molecular weight of the homodimeric antibody. Liquid chromatography was used to determine that about 28.16 percent of the protein in the reaction mixture displayed a molecular weight consistent with the homodimeric antibody.

The homodimeric antibody was then purified from monomeric antibodies using size-exclusion chromatography. An SDS-PAGE analysis of different fractions of the eluent from size-exclusion chromatography is depicted in FIG. 12A, in which lanes 1 through 6 each correspond to 1 microgram total protein from different, consecutive fractions of the eluent under non-reducing conditions, lane 7 corresponds to 1 microgram of an IgG standard loaded under non-reducing conditions, lane 8 corresponds to a molecular weight standard, lanes 9 through 14 each correspond to 2 micrograms total protein from different, consecutive fractions of the eluent under reducing conditions, and lane 15 corresponds to 2 micrograms of an IgG standard loaded under reducing conditions. Lanes 1 and 9 correspond to the same fraction, which was about 64.98 percent pure as determined by liquid chromatography. Lanes 2 and 10 correspond to the same fraction, which was about 84.54 percent pure as determined by liquid chromatography. Lanes 3 and 11 correspond to the same fraction, which was about 92.62 percent pure as determined by liquid chromatography. Lanes 4 and 12 correspond to the same fraction, which was about 94.86 percent pure as determined by liquid chromatography. Lanes 5 and 13 correspond to the same fraction, which was about 96.17 percent pure as determined by liquid chromatography. Lanes 6 and 14 correspond to the same fraction, which was about 96.61 percent pure as determined by liquid chromatography. A liquid chromatography trace corresponding to the homodimeric antibody of lanes 5 and 13 is shown in