Methods for treating metastatic castration-resistant prostate cancer with bispecific anti-psma x anti-CD3 antibodies alone or in combination with an anti-PD-1 antibody

Abstract

The present disclosure provides methods for treating, reducing the severity of, or inhibiting the growth of cancer (e.g., prostate cancer or metastatic castration-resistant prostate cancer). The methods of the disclosure include administering to a subject in need thereof a therapeutically effective amount of a bispecific antibody that specifically binds prostate-specific membrane antigen (PSMA) and CD3, or an antigen-binding fragment thereof, alone or in combination with an antibody that specifically binds to the Programmed death 1 (PD-1) receptor, or an antigen-binding fragment thereof.

Description

[Technical field]

[0001] Sequence Listing Reference This application incorporates by reference a computer readable sequence listing in ST.26 XLM format entitled 11050WO01_Sequence, created on May 15, 2023, and containing 38,992 bytes.

[0002] The present invention relates to a method for treating cancer comprising administering to a subject in need thereof a therapeutically effective amount of a bispecific antibody that specifically binds to prostate-specific membrane antigen (PSMA) and CD3, alone or in combination with an antibody that specifically binds to the programmed death 1 (PD-1) receptor. [Background technology]

[0003] Prostate-specific membrane antigen (PSMA), also known as FOLH1, glutamic acid carboxypeptidase II (GCPII), N-acetyl-L-aspartyl-L-glutamic acid peptidase I (NAALADase I ), or N-acetyl-aspartylglutamic acid (NAAG) peptidase, is a homodimeric enzyme type II transmembrane protein encoded by the folate hydrolase 1 (FOLH1 ) gene. PSMA is an integral, non-shaded membrane glycoprotein that is highly expressed on malignant prostate tissue and is a cell surface marker for prostate cancer, but shows limited expression on normal tissue. Its expression is maintained in castration-resistant prostate cancer, which has a poor prognosis and limited treatment options. Methods to treat prostate cancer by targeting PSMA are being investigated. For example, yttrium-90 capromab is a radiotherapeutic agent that contains a monoclonal antibody against an intracellular epitope of PSMA. In another example, J591, a monoclonal antibody against an extracellular epitope of PSMA, is part of the radiotherapy ruthenium-177 J591, and maytansinoid 1 (DM1, an anti-microtubule agent) is part of MLN2704, which combines J591. These therapies are associated with toxicity. PSMA is also expressed within the angiogenesis of other tumors, such as bladder, kidney, stomach, and colorectal cancer.

[0004] CD3 is a homodimeric or heterodimeric antigen expressed on T cells in association with the T cell receptor complex (TCR) and is required for T cell activation. Functional CD3 is formed from the dimeric association of two of four different chains: epsilon, zeta, delta, and gamma. CD3 dimeric configurations include gamma / epsilon, delta / epsilon, and zeta / zeta. Antibodies against CD3 have been shown to cluster CD3 on T cells, thereby triggering T cell activation in a manner similar to TCR engagement by peptide-loaded MHC molecules. Thus, anti-CD3 antibodies have been proposed for therapeutic purposes, including T cell activation. Furthermore, bispecific antibodies capable of binding CD3 and a target antigen have been proposed for therapeutic uses, including targeting T cell immune responses to tissues and cells expressing the target antigen.

[0005] Programmed death-1 (PD-1) receptor signaling in the tumor microenvironment plays a key role in enabling tumor cells to escape immunosurveillance by the host immune system. Blockade of the PD-1 signaling pathway has demonstrated clinical activity in patients with multiple tumor types, and antibody therapeutics that block PD-1 (e.g., nivolumab and pembrolizumab) have been approved for the treatment of, for example, metastatic melanoma and metastatic squamous non-small cell lung cancer. Recent data have demonstrated clinical activity of PD-1 blockade in patients with aggressive NHL and Hodgkin's lymphoma (Lesokhin et al., 2014, Abstract 291, 56th ASH Annual Meeting and Exposition, San Francisco, Calif.; Ansell et al., 2015, N. Engl. J. Med. 372(4):311-9).

[0006] Prostate cancer is the leading cause of new cancer diagnoses and the second leading cause of cancer-related deaths in men in the United States. In 2018, there were 1.3 million new cases of prostate cancer worldwide, with an estimated 358,989 deaths. Therapies that block androgen-related pathways have been the standard in the treatment of prostate cancer for decades. However, patients progress through androgen deprivation and / or surgical castration and develop castration-resistant prostate cancer. Prognosis is particularly poor for men with metastatic castration-resistant prostate cancer (mCRPC). Currently, metastatic prostate cancer remains incurable, and improving long-term survival remains a high unmet need. Summary of the Invention

[0007] According to certain embodiments, the present disclosure provides a method for treating, ameliorating, or inhibiting the growth of at least one symptom or sign of a PSMA-expressing cancer in a subject. The method according to this aspect of the disclosure comprises administering to a subject in need thereof a therapeutically effective amount of a bispecific antibody that specifically binds prostate-specific membrane antigen (PSMA) and CD3, alone or in combination with an antibody or antigen-binding fragment thereof that specifically binds programmed death 1 (PD-1). [Problem to be solved by the invention]

[0008] In certain embodiments of the present disclosure, methods are provided for treating, ameliorating at least one symptom or sign, or inhibiting the growth of a PSMA-expressing cancer in a subject.

[0009] In certain embodiments of the present disclosure, methods of slowing tumor growth or preventing tumor recurrence are provided. Methods according to this and other aspects of the disclosure include sequentially administering to a subject in need thereof a therapeutically effective amount of one or more doses of a bispecific anti-PSMA x anti-CD3 antibody, alone or in combination with a therapeutically effective amount of one or more doses of an anti-PD-1 antibody or antigen-binding fragment thereof.

[0010] In one aspect, the disclosure provides a method of treating a PSMA-expressing cancer in a subject in need thereof, comprising administering to the subject a bispecific antibody comprising a first antigen-binding domain that specifically binds to prostate-specific membrane antigen (PSMA) on a target tumor cell and a second antigen-binding domain that specifically binds to human CD3 on a T cell, wherein the bispecific antibody is administered to the subject at a dose of at least 0.03 mg.

[0011] In some embodiments, the PSMA-expressing cancer is prostate cancer. In some cases, the PSMA-expressing cancer is metastatic prostate cancer. In some cases, the PSMA-expressing cancer is castration-resistant prostate cancer.

[0012] In some embodiments, the subject has undergone at least two prior therapies for metastatic and / or castration-resistant prostate cancer. In some cases, the subject has undergone at least one antiandrogen therapy. In some embodiments, the antiandrogen therapy is selected from abiraterone, enzalutamide, apalutamide, or darolutamide.

[0013] In some embodiments, the subject has histologically or cytologically confirmed adenocarcinoma of the prostate that does not have pure small cell carcinoma.

[0014] In some embodiments, the subject has metastatic castration-resistant prostate cancer with a prostate-specific antigen (PSA) value of >4 ng / ml prior to treatment with the bispecific antibody. In some cases, the subject's cancer has progressed within 6 months prior to treatment with the bispecific antibody, with cancer progression determined by (a) an increase in PSA level noted at intervals of >1 week between assessments, (b) progression of soft tissue radiological disease with or without an increase in PSA, and / or (c) progression of bone radiological disease with the appearance of two or more bone lesions on a bone scan with or without an increase in PSA.

[0015] In some embodiments, the subject has undergone an orchiectomy. In some embodiments, the subject has undergone luteinizing hormone releasing hormone (LHRH) agonist or antagonist therapy and has serum testosterone levels of <50 ng / ml prior to treatment with the bispecific antibody.

[0016] In any of the various embodiments described above or discussed herein, the first antigen-binding domain of the bispecific antibody comprises (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) comprised within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:1, and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) comprised within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:2. In some cases, the first antigen-binding domain comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO:5, an HCDR2 comprising the amino acid sequence of SEQ ID NO:6, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:7. In some cases, the first antigen-binding domain comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO:8, an LCDR2 comprising the amino acid sequence of SEQ ID NO:9, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:10. In some embodiments, the first antigen-binding domain comprises an HCVR comprising the amino acid sequence of SEQ ID NO:1, and an LCVR comprising the amino acid sequence of SEQ ID NO:2.

[0017] In any of the various embodiments described above or discussed herein, the second antigen-binding domain of the bispecific antibody comprises (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) comprised within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:4, and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) comprised within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:2. In some cases, the second antigen-binding domain comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO:14, an HCDR2 comprising the amino acid sequence of SEQ ID NO:15, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:16. In some cases, the second antigen-binding domain comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO:8, an LCDR2 comprising the amino acid sequence of SEQ ID NO:9, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:10. In some embodiments, the second antigen-binding domain comprises an HCVR comprising the amino acid sequence of SEQ ID NO:4, and an LCVR comprising the amino acid sequence of SEQ ID NO:2.

[0018] In any of the various embodiments described above or discussed herein, the second antigen-binding domain of the bispecific antibody comprises (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) comprised within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:3, and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) comprised within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:2. In some cases, the second antigen-binding domain comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO:11, an HCDR2 comprising the amino acid sequence of SEQ ID NO:12, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:13. In some cases, the second antigen-binding domain comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO:8, an LCDR2 comprising the amino acid sequence of SEQ ID NO:9, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:10. In some embodiments, the second antigen-binding domain comprises an HCVR comprising the amino acid sequence of SEQ ID NO:3, and an LCVR comprising the amino acid sequence of SEQ ID NO:2.

[0019] In any of the various embodiments described above or discussed herein, the bispecific antibody may comprise a human IgG heavy chain constant region. In some cases, the human IgG heavy chain constant region is of isotype IgG1. In some cases, the human IgG heavy chain constant region is of isotype IgG4.

[0020] In any of the various embodiments described above or discussed herein, the bispecific antibody may comprise a chimeric hinge that reduces Fcγ receptor binding compared to a wild-type hinge of the same isotype.

[0021] In any of the various embodiments described above or discussed herein, the first heavy chain of the bispecific antibody or the second heavy chain of the bispecific antibody (but not both) may comprise a CH3 domain comprising the H435R (EU numbering) and Y436F (EU numbering) variants.

[0022] In any of the various embodiments described above or discussed herein, the bispecific antibody comprises a first heavy chain comprising the amino acid sequence of SEQ ID NO:17.

[0023] In any of the various embodiments described above or discussed herein (except where the sequences are mutually exclusive), the bispecific antibody comprises a second heavy chain comprising the amino acid sequence of SEQ ID NO:20.

[0024] In any of the various embodiments described above or discussed herein (except where the sequences are mutually exclusive), the bispecific antibody comprises a second heavy chain comprising the amino acid sequence of SEQ ID NO:19.

[0025] In any of the various embodiments described above or discussed herein, the bispecific antibody comprises a light chain comprising the amino acid sequence of SEQ ID NO:18.

[0026] In any of the various embodiments described above or discussed herein (except where the sequences are mutually exclusive), the bispecific antibody comprises a first heavy chain comprising the amino acid sequence of SEQ ID NO: 17, a second heavy chain comprising the amino acid sequence of SEQ ID NO: 20, and a common light chain comprising the amino acid sequence of SEQ ID NO: 18.

[0027] In any of the various embodiments described above or discussed herein (except where the sequences are mutually exclusive), the bispecific antibody comprises a first heavy chain comprising the amino acid sequence of SEQ ID NO: 17, a second heavy chain comprising the amino acid sequence of SEQ ID NO: 19, and a common light chain comprising the amino acid sequence of SEQ ID NO: 18.

[0028] In any of the various embodiments described above or discussed herein, the method may further include administering a second therapeutic agent or treatment regimen. In some embodiments, the second therapeutic agent or treatment regimen comprises an anti-PD-1 antibody or antigen-binding fragment thereof.

[0029] In some embodiments, the anti-PD-1 antibody or antigen-binding fragment comprises (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) contained within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:21, and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) contained within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:22. In some cases, the anti-PD-1 antibody or antigen-binding fragment comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO:23, an HCDR2 comprising the amino acid sequence of SEQ ID NO:24, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:25. In some cases, the anti-PD-1 antibody or antigen-binding fragment comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO:26, an LCDR2 comprising the amino acid sequence of SEQ ID NO:27, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:28. In some embodiments, the anti-PD-1 antibody or antigen-binding fragment comprises an HCVR comprising the amino acid sequence of SEQ ID NO:21, and an LCVR comprising the amino acid sequence of SEQ ID NO:22. In some embodiments, the anti-PD-1 antibodies and antigen-binding fragments are anti-PD-1 antibodies that comprise a heavy chain comprising the amino acid sequence of SEQ ID NO:29 and a light chain comprising the amino acid sequence of SEQ ID NO:30.

[0030] In any of the various embodiments described above or discussed herein, the bispecific antibody may be administered to the subject once a week at a dose between 0.01 mg and 1000 mg. In some cases, the bispecific antibody is administered to the subject once a week at a dose between 0.03 mg and 30 mg. In some cases, the bispecific antibody is administered to the subject once a week at a dose between 3 mg and 900 mg. In some cases, the bispecific antibody is administered to the subject once a week at a dose between 30 mg and 900 mg. In some cases, the bispecific antibody is administered to the subject once a week at a dose between 300 mg and 900 mg.

[0031] In any of the various embodiments described above or discussed herein, the bispecific antibody may be administered to the subject at a dose of 0.01 mg to 1000 mg once every three weeks. In some cases, the bispecific antibody is administered to the subject at a dose of 0.03 mg to 30 mg once every three weeks. In some cases, the bispecific antibody is administered to the subject at a dose of 3 mg to 900 mg once every three weeks. In some cases, the bispecific antibody is administered to the subject at a dose of 30 mg to 900 mg once every three weeks. In some cases, the bispecific antibody is administered to the subject at a dose of 300 mg to 900 mg once every three weeks.

[0032] In any of the various embodiments described above or discussed herein, the anti-PD-1 antibody may be administered to the subject at a dose of 300-400 mg once every three weeks. In some cases, the anti-PD-1 antibody is administered to the subject at a dose of 350 mg once every three weeks.

[0033] In any of the various embodiments described above or discussed herein, the subject exhibits stable disease, a partial response, or a complete response after at least one week of administration of the bispecific antibody at a dose between 0.03 mg and 900 mg.

[0034] In any of the various embodiments described above or discussed herein, the subject may undergo x-ray imaging before and / or after administration of one or more doses of the bispecific antibody. In some cases, the x-ray imaging comprises a Fluorine F18 DCFPyL PET / CT scan.

[0035] The present disclosure also encompasses the use of bispecific antibodies and / or anti-PD-1 antibodies in the manufacture of a medicament for treating a PSMA-expressing cancer as described in any of the method embodiments above or discussed herein. The present disclosure also encompasses bispecific antibodies and / or anti-PD-1 antibodies for use in any of the method embodiments above or discussed herein. The present disclosure also encompasses pharmaceutical compositions comprising bispecific antibodies and / or anti-PD-1 antibodies for use in any of the method embodiments above or discussed herein.

[0036] In various embodiments, any of the features or components of the embodiments described above or discussed herein may be combined, and such combinations are encompassed within the scope of the present disclosure. Any specific value described above or discussed herein may be combined with another associated value described above or discussed herein to recite a range having values ​​representing the upper and lower limits of the range, and such ranges are encompassed within the scope of the present disclosure.

[0037] Other embodiments of the invention will become apparent from consideration of the detailed description that follows. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 illustrates an embodiment of a patient-level testing scheme for Module 1 (QW dosing) discussed in Example 6. [Diagram 2] FIG. 2 illustrates an embodiment of a patient-level testing scheme for Module 1 (Q3W dosing) discussed in Example 6. [Diagram 3] FIG. 3 illustrates an embodiment of the module 2 patient-level testing scheme discussed in Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Before describing the present invention, it should be understood that the present invention is not limited to the specific methods and experimental conditions described, as such methods and conditions may vary. It should also be understood that the terms used herein are used for the purpose of describing only specific embodiments, and are not intended to be limiting, since the scope of the present invention is limited only by the scope of the appended claims. Any embodiment or feature of the embodiment can be combined with each other, and such combinations are expressly included within the scope of the present invention. Any specific value discussed above or herein may be combined with another related value discussed above or herein to recite a range having values ​​representing the upper and lower limits of the range, and such ranges are included within the scope of the present disclosure.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.As used herein, the term "about" when used in relation to a specific recited numerical value or range of values ​​means that the value may vary from the recited value by 1% or less.For example, as used herein, the expression "about 100" includes 99 and 101, and all values ​​therebetween (e.g., 99.1, 99.2, 99.3, 99.4, etc.).

[0041] Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, exemplary methods and materials are now described. All patents, applications, and non-patent publications mentioned herein are incorporated by reference in their entirety.

[0042] Methods for Treating Cancer or Inhibiting Cancer Growth - Patent application The present disclosure includes a method for treating, ameliorating or reducing the severity of at least one symptom or indication, or inhibiting the growth of cancer (e.g., metastatic castration-resistant prostate cancer) in a subject. The method according to this aspect of the disclosure includes administering to a subject in need thereof a therapeutically effective amount of a bispecific antibody against PSMA and CD3, alone or in combination with a therapeutically effective amount of an antibody or antigen-binding fragment thereof that specifically binds to PD-1. As used herein, the terms "treat", "treating" and the like mean to alleviate a symptom, eliminate the cause of a symptom, either temporarily or permanently, slow or inhibit tumor growth, reduce tumor cell or tumor burden, promote tumor regression, cause tumor shrinkage, necrosis and / or disappearance, prevent tumor recurrence, and / or prolong the survival of a subject. As used herein, the term "subject in need thereof" refers to a human or non-human mammal exhibiting one or more symptoms or signs of cancer, and / or a human or non-human mammal diagnosed with cancer, including prostate cancer (e.g., metastatic castration-resistant prostate cancer), and in need of treatment thereof. In many embodiments, the term "subject" may be used interchangeably with the term "patient." For example, a human subject may be diagnosed with a primary tumor or a metastatic tumor and / or with one or more symptoms or signs, including, but not limited to, enlarged lymph nodes, abdominal distension, unexplained pain, unexplained weight loss, fever, night sweats, persistent fatigue, loss of appetite, and / or enlarged spleen. This term includes a subject with a primary tumor or established prostate cancer. In specific embodiments, this term includes a human subject with prostate cancer or another tumor expressing PSMA and in need of treatment thereof. In other specific embodiments, this term includes a subject with a PSMA+ tumor (e.g., a tumor with PSMA expression as determined by flow cytometry). In certain embodiments, the term "subject in need thereof" includes patients with prostate cancer that is resistant, refractory, or poorly controlled to prior therapy (e.g., treatment with conventional anticancer agents, including antiandrogen therapy). For example, the term includes subjects treated with chemotherapy or antiandrogen therapy, such as abiraterone, enzalutamide, apalutamide, or darolutamide. The term also includes subjects with prostate cancer for whom conventional anticancer therapy is not advisable, for example, due to toxic side effects. For example, the term includes patients who have undergone one or more cycles of chemotherapy or other cancer treatments with toxic side effects. In certain embodiments, the term "subject in need thereof" includes patients with prostate cancer who have been treated but have subsequently relapsed or metastasized. For example, patients with prostate cancer who have undergone treatment with one or more anticancer agents and may have undergone tumor regression, but who subsequently relapse with cancer resistant to one or more anticancer agents (e.g., castration-resistant prostate cancer) are treated with the methods of the present disclosure.

[0043] In certain embodiments, the methods of the present disclosure may be used to treat patients with histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma. In certain embodiments, the methods of the present disclosure may be used to treat patients with metastatic castration-resistant prostate cancer with a prostate-specific antigen (PSA) level of ≧4ng / ml (e.g., ≧4ng / ml, 4.5ng / ml, 5ng / ml, 5.5ng / ml, 6ng / ml, 6.5ng / ml, 7ng / ml, 7.5ng / ml, 8ng / ml, 8.5ng / ml, 9ng / ml, 9.5ng / ml, or ≧10ng / ml) prior to treatment with the bispecific antibody. In certain embodiments, the disclosed methods may be used to treat patients with prostate cancer that has progressed within a period of time (e.g., 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 7 months, 8 months, 9 months or more) prior to treatment with a bispecific antibody, where cancer progression is determined, for example, by (a) an interval of ≧1 week (e.g., 1 week, 2 weeks, 3 weeks, 4 weeks or more) between evaluations, (b) soft tissue radiological disease progression with or without PSA elevation, and / or (c) bone radiological disease progression with the appearance of two or more bone lesions on a bone scan with or without PSA elevation. In certain embodiments, the disclosed methods may be used to treat patients who have undergone orchiectomy. In certain embodiments, the methods of the disclosure may be used to treat patients who have or are undergoing luteinizing hormone releasing hormone (LHRH) agonist or antagonist therapy and have serum testosterone levels of <50 ng / ml (e.g., 1 ng / ml to 49 ng / ml, about 45 ng / ml, about 40 ng / ml, about 35 ng / ml, about 30 ng / ml, about 25 ng / ml, about 20 ng / ml, about 15 ng / ml, about 10 ng / ml, or about 5 ng / ml) prior to treatment with the bispecific antibody.

[0044] In certain embodiments, the methods of the present disclosure are used in subjects with prostate cancer. The terms "tumor," "cancer," and "malignant tumor" are used interchangeably herein. As used herein, the term "prostate cancer" refers to tumors of the prostate, including metastatic tumors originating from the prostate.

[0045] According to certain embodiments, the disclosure includes methods of treating, slowing, or inhibiting tumor growth. In certain embodiments, the disclosure includes methods of promoting tumor regression. In certain embodiments, the disclosure includes methods of reducing tumor cell burden or reducing tumor burden. In certain embodiments, the disclosure includes methods of preventing tumor recurrence. Methods according to this aspect of the disclosure include administering to a subject in need thereof a therapeutically effective amount of a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody, where each antibody is administered to the subject in multiple doses, e.g., as part of a particular therapeutic dosing regimen. For example, a therapeutic dosing regimen may include administering one or more doses of anti-PSMAxCD3 antibody to a subject approximately once a day, once every 2 days, once every 3 days, once every 4 days, once every 5 days, once every 6 days, once a week, once every 2 weeks, once every 3 weeks, once every 4 weeks, once a month, once every 2 months, once every 3 months, once every 4 months, or less frequently. In certain embodiments, the anti-PSMAxanti-CD3 antibody is administered once a week. In certain embodiments, the anti-PSMAxanti-CD3 antibody is administered once every 3 weeks. In certain embodiments, one or more doses of an anti-PD-1 antibody are administered in combination with a therapeutically effective amount of one or more doses of a bispecific anti-PSMA / anti-CD3 antibody, and the one or more doses of an anti-PD-1 antibody are administered to a subject no more frequently than about once per day, once every two days, once every three days, once every four days, once every five days, once every six days, once every two weeks, once every three weeks, once every four weeks, once per month, once every six weeks, once every two months, once every three months, or once every four months. In certain embodiments, the anti-PD-1 antibody is administered to a subject once every three weeks.

[0046] In certain embodiments, each dose of anti-PSMA / anti-CD3 antibody is administered in two or more separate doses, e.g., two to five separate doses ("split doses"), within a given administration period. Anti-PSMA / anti-CD3 bispecific antibodies may be administered in split doses to reduce or eliminate the cytokine "spike" induced in response to administration of the antibody. Cytokine spike refers to the clinical symptoms of cytokine release syndrome ("cytokine storm") and infusion-related reactions. In certain embodiments, the disclosed method comprises administering one or more doses of an anti-PD-1 antibody in combination with one or more doses of a bispecific anti-PSMA / anti-CD3 antibody to a subject in need thereof, where the dose of the bispecific antibody is administered as a split dose or in two or more separate doses, e.g., two, three, four, or five separate doses, within a given administration period. In certain embodiments, the dose of the bispecific antibody is divided into two or more portions, each portion containing an equal amount of antibody as the other portions. In certain embodiments, a dose of a bispecific antibody is administered in two or more portions, the portions containing unequal amounts of antibody, e.g., greater or less than the first portion.

[0047] In certain embodiments, the disclosure includes a method of inhibiting, slowing, or stopping tumor metastasis or tumor invasion to peripheral organs. According to this aspect, the method comprises administering to a subject in need thereof a therapeutically effective amount of a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody.

[0048] In certain embodiments, the disclosure provides a method of increasing anti-tumor efficacy or increasing tumor inhibition. According to this aspect of the disclosure, the method comprises administering to a subject having prostate cancer a therapeutically effective amount of an anti-PD-1 antibody prior to administering a therapeutically effective amount of a bispecific anti-PSMA / anti-CD3 antibody, where the anti-PD-1 antibody can be administered about 1 day, more than 1 day, more than 2 days, more than 3 days, more than 4 days, more than 5 days, more than 6 days, more than 7 days, or more than 8 days prior to the bispecific antibody. In certain embodiments, the method provides an increase in tumor inhibition, e.g., about 20%, more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, or more than 80%, compared to a subject administered the bispecific antibody alone.

[0049] In certain embodiments, the methods of the present disclosure are used to treat patients with MRD-positive disease. Minimal residual disease (MRD) refers to a small number of cancer cells remaining in a patient during or after treatment, who may or may not show symptoms or signs of disease. Such residual cancer cells, if not removed, often lead to disease recurrence. The present disclosure includes methods of inhibiting and / or removing residual cancer cells in a patient upon MRD testing. MRD can be assayed according to methods known in the art (e.g., MRD flow cytometry). The method according to this aspect of the disclosure includes administering a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody, to a subject in need thereof.

[0050] According to certain embodiments, the methods of the disclosure comprise administering to a subject a therapeutically effective amount of a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody and optionally a third therapeutic agent. The third therapeutic agent may be, for example, an agent selected from the group consisting of radiation, chemotherapy, surgery, a cancer vaccine, an oncolytic virus, a PD-L1 inhibitor (e.g., an anti-PD-L1 antibody), a LAG3 inhibitor (e.g., an anti-LAG3 antibody), a CTLA-4 inhibitor (e.g., an anti-CTLA-4 antibody), a TIM3 inhibitor, a BTLA inhibitor, a TIGIT inhibitor, a CD47 inhibitor, an indoleamine-2-3-dioxygenase (IDO) inhibitor, a vascular endothelial growth factor (VEGF) antagonist, an Ang2 inhibitor, a transforming growth factor beta (TGF.beta.) inhibitor, an epidermal growth factor receptor (EGFR) inhibitor, an antibody against a tumor-specific antigen, a cytotoxin, a chemotherapeutic agent, a cytokine such as an IL-6R inhibitor, an IL-4R inhibitor, an IL-10 inhibitor, IL-2, IL-7, IL-21, IL-15, etc., an anti-inflammatory agent such as a corticosteroid, a nonsteroidal anti-inflammatory agent, etc., and a nutritional supplement such as an antioxidant. In certain embodiments, the antibody may be administered in combination with therapies including chemotherapy, radiation, and surgery. As used herein, the phrase "in combination with" means that the antibody is administered to the subject simultaneously with, immediately before, or immediately after the administration of a third therapeutic agent. In certain embodiments, the antibody and the third therapeutic agent are administered as separate formulations.

[0051] In any of the various embodiments discussed herein, the methods of the present disclosure may further include administration of a steroid (e.g., dexamethasone or an equivalent steroid), or an anti-IL-6 receptor antibody. In some cases, the anti-IL-6 receptor antibody is tocilizumab or sarilumab. In some cases, the steroid (e.g., dexamethasone) may be administered at a dose of 1 mg to 20 mg (e.g., 5 mg to 10 mg) IV or PO. In some cases, these agents may be administered as a premedication prior to administration of the bispecific antibody (e.g., REGN4336).

[0052] In certain embodiments, the methods of the disclosure comprise administering a therapeutically effective amount of a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody, to a subject in need thereof. When a bispecific antibody or combination thereof is administered, administration of the antibody increases inhibition of tumor growth. In certain embodiments, tumor growth is inhibited by at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, or about 80% compared to an untreated subject or a subject administered either antibody, respectively, as monotherapy. In certain embodiments, administration of a bispecific antibody or combination thereof enhances tumor regression, tumor shrinkage, and / or elimination. In certain embodiments, administration of the bispecific antibody or combinations thereof leads to a delay in tumor growth and progression, e.g., tumor growth may be delayed by about 3 days, more than 3 days, about 7 days, more than 7 days, more than 15 days, more than 1 month, more than 3 months, more than 6 months, more than 1 year, more than 2 years, or more than 3 years, compared to an untreated subject or a subject treated with either antibody, respectively, as monotherapy. In certain embodiments, administration of the bispecific antibody or combinations thereof prevents tumor recurrence and / or increases the survival time of the subject, e.g., increases the duration of survival by more than 15 days, more than 1 month, more than 3 months, more than 6 months, more than 12 months, more than 18 months, more than 24 months, more than 36 months, or more than 48 months, compared to an untreated subject or a subject treated with either antibody, respectively, as monotherapy. In certain embodiments, administration of the bispecific antibody or combinations thereof increases progression-free survival or overall survival. In certain embodiments, administration of a bispecific antibody or combination thereof increases the response and duration of response in a subject by, for example, more than 2%, more than 3%, more than 4%, more than 5%, more than 6%, more than 7%, more than 8%, more than 9%, more than 10%, more than 20%, more than 30%, more than 40%, or more than 50% over untreated subjects or subjects receiving either antibody, respectively, as monotherapy. In certain embodiments, administration of a bispecific antibody or combination thereof to a subject with prostate cancer results in the complete disappearance of all evidence of tumor cells (a "complete response").In certain embodiments, administration of a bispecific antibody or combination thereof to a subject with prostate cancer results in at least a 30% or greater reduction in tumor cells or tumor size ("partial response"). In certain embodiments, administration of a bispecific antibody or combination thereof to a subject with prostate cancer results in complete or partial disappearance of tumor cells / lesions, including new measurable lesions. Tumor reduction can be measured by any of the methods known in the art, for example, X-ray, positron emission tomography (PET), computed tomography (CT), magnetic resonance imaging (MRI), cytology, histology, or molecular genetic analysis. In certain embodiments, administration of a bispecific antibody and an anti-PD-1 antibody results in a synergistic anti-tumor effect that exceeds the combined effect of the two agents when administered alone.

[0053] In certain cases, a subject's response to therapy is classified as complete response (CR), partial response (PR), progressive disease (PD), or stable disease (SD). CR is defined as the disappearance of all target lesions and the reduction of the short axis of any pathological lymph nodes (target or non-target) to < 10 mm (< 1 cm). PR is defined as at least a 30% reduction in the sum of the diameters of the target lesions, based on the baseline sum of the diameters. PD is defined as at least a 20% increase in the sum of the diameters of the target lesions, based on the minimum sum on study (including the baseline sum, if it is the minimum on study). In addition to the 20% relative increase, the sum must also show an absolute increase of at least 5 mm (0.5 cm). (Note: the appearance of one or more new lesions is also considered progression). SD is defined as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD, based on the minimum sum of the diameters on study.

[0054] In certain cases, immune-based therapy response criteria may be used to assess response. Immune-based therapy response criteria differ from RECIST (version 1.1) in that progression is slightly more difficult to confirm because it must occur on the scan immediately following an unconfirmed progression scan. This difference is based on the understanding that immune therapy may cause pseudoprogression based on inflammation up to and including the development of new lesions. Thus, two scans at least 4 weeks apart must agree that the disease has progressed to confirmed progression. The criteria used to assess target and non-target lesions are discussed below.

[0055] Target Lesion Evaluation Immune complete response (iCR): Disappearance of all target lesions. Any pathological lymph nodes (target or non-target) must be reduced to < 10 mm (< 1 cm) in the short axis Immune partial response (iPR): At least a 30% reduction in the sum of the diameters of target lesions compared to the sum of the diameters at baseline Immunodeficient Progression (iUPD): The sum of the diameters of the new target lesions since the last scan has increased by at least 20% relative to the minimum sum on exam (including the baseline sum if it is the minimum sum on exam). In addition to the 20% relative increase, the sum must also show an absolute increase of at least 5 mm (0.5 cm). Immunoconfirmed disease progression (iCPD): If the next imaging assessment after iUPD (4-8 weeks later) confirms further increase in the total or measured target disease from iUPD with an increase of at least 5 mm, progression is confirmed in the target lesion category. Immune Stable Disease (iSD): No sufficient shrinkage to qualify for iPR or sufficient increase to qualify for iUPD or iCPD, including new lesion measurements, based on the smallest sum diameter on study.

[0056] Evaluation of non-target lesions Immune complete response (iCR): Disappearance of all non-target lesions and normalization of tumor marker levels. All lymph nodes must be non-pathological in size (<10 mm [<1 cm] short axis). Tumor markers, if initially above the upper limit of normal, must normalize to consider the patient as having a complete clinical response. Non-iCR / non-iUPD or -iCPD: persistence of one or more non-target lesion(s) and / or maintenance of tumor marker levels above normal limits Immunodefinite Progression (iUPD): Definite progression of pre-existing non-target lesions without iUPD on the previous scan. Definite progression should not usually be a worsening of the target lesion status. It should represent a change in the overall disease state, not an increase in a single lesion. Immunoconfirmed disease progression (iCPD): Definite progression of a pre-existing non-target lesion with iUPD on the immediately preceding scan. Disease progression in the non-target lesion category is confirmed when a subsequent scan performed 4-8 weeks after iUPD shows further increase from iUPD. Definite progression should not usually be a worsening of the target lesion status. It should represent a change in overall disease status, not an increase in a single lesion.

[0057] In certain cases, imaging may be used to assess a subject's response to treatment (either alone or in combination with the assessment of PSA levels). PSMA PET / CT has been shown to provide a sensitive measure of both PSMA expression and tumor burden in prostate cancer patients. With improved sensitivity and specificity over current conventional imaging modalities for tumor lesion detection, PSMA PET / CT has been shown to improve tumor response assessment and the efficacy of treatment strategies.

[0058] Fluorine F18 DCFPyL (18F-DCFPyL) is a radiolabeled small molecule that binds with high affinity to the extracellular domain of PSMA. Data from enzyme inhibition assays showed that DCFPyL competitively binds to PSMA-expressing LNCaP cells with a Ki of 1.1 nM. 18F-DCFPyL has been tested in multiple Phase 1-3 trials and found to be well tolerated in prostate cancer patients. 18F-DCFPyL was approved by the FDA on May 26, 2021 for PET scanning of PSMA-positive lesions in men with suspected metastatic prostate cancer who are candidates for first definitive therapy and suspected to have recurred based on rising serum prostate-specific antigen (PSA) levels.

[0059] After administration of 18F-DCFPyL injections, the biodistribution and optimal imaging time points were determined. The radiation doses used in the study were within the limits of diagnostic radiotracers for PET. The physiological accumulation of 18F-DCFPyL was found to correspond to the distribution of PSMA-expressing organs. The accumulation in primary tumors and metastatic lesions was very high, suggesting that 18F-DCFPyL injections can be used to detect residual tumors as well as local or distant metastases with high sensitivity and specificity. Taken together, these findings strongly support the use of 18F-DCFPyL PSMA PET / CT to assess the total body tumor burden and antitumor activity of REGN4336 alone and in combination with cemiplimab in patients with mCRPC.

[0060] 18F-DCFPyL at an intended dose of about 9±1 mCi per IV injection is overall feasible and safe. The radiation dose from an 18F-DCFPyL PET / CT scan is about 7.4 mSv. In comparison, a typical CT scan dose of the chest, abdomen, and pelvis is estimated to be about 25 mSv, a single bone scan is about 4.4 mSv, and the annual natural background radiation dose in the United States is about 3.1 mSv. A protocol of up to three 18F-DCFPyL PET / CT scans within one year would result in an approximate dose of about 22.2 mSv, which is about 45% of the maximum tolerated dose of 50 mSv recommended for adult study patients (21CRF361.1) in one year. For patients who may receive 4 PSMA PET scans (3 scheduled + 1 unscheduled), the total radiation dose from those scans will be approximately 29.6 mSv, which is approximately 59% of the recommended maximum tolerated annual dose for adult study patients. The risks of 18F-DCFPyL, including radiation exposure, will be disclosed to patients on the PET imaging informed consent form.

[0061] Any fluorodeoxyglucose (FDG) PET / CT may be used to assess metabolically active tumor burden in patients. PSMA expressing and non-expressing tumors have been detected by FDG PET / CT in prostate cancer patients. Complementary FDG and PSMA PET / CT data are expected to provide insight into tumor response to therapy (e.g., REGN4336).

[0062] Anti-PD-1 antibodies and antigen-binding fragments thereof According to certain exemplary embodiments of the present disclosure, the method includes administering a therapeutically effective amount of an anti-PD-1 antibody or an antigen-binding fragment thereof. As used herein, the term "antibody" includes immunoglobulin molecules comprising four polypeptide chains, two heavy (H) chains and two light (L) chains interconnected by disulfide bonds, as well as multimers thereof (e.g., IgM). In a conventional antibody, each heavy chain comprises a heavy chain variable region (abbreviated herein as HCVR or VH) and a heavy chain constant region. The heavy chain constant region comprises three domains, CH1, CH2, and CH3. Each light chain comprises a light chain variable region (abbreviated herein as LCVR or VL) and a light chain constant region. The light chain constant region comprises one domain (CL1). The VH and VL regions can be further subdivided into hypervariable regions, termed complementarity determining regions (CDRs), separated by relatively conserved regions, termed framework regions (FRs). Each VH and VL is composed of three CDRs and four FRs arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. In different embodiments of the disclosure, the FRs of the anti-PD-1 antibodies (or antigen-binding portions thereof) may be identical to human germline sequences or may be naturally or artificially modified. An amino acid consensus sequence may be defined based on a side-by-side analysis of two or more CDRs.

[0063] As used herein, the term "antibody" also includes antigen-binding fragments of complete antibody molecules. As used herein, the terms "antigen-binding portion" of an antibody, "antigen-binding fragment" of an antibody, etc., include any naturally occurring, enzymatically obtainable, synthetic, or genetically engineered polypeptide or glycoprotein that specifically binds to an antigen to form a complex. Antigen-binding fragments of antibodies may be derived from complete antibody molecules using any suitable standard method, such as, for example, proteolytic or recombinant genetic engineering techniques, involving the manipulation and expression of DNA encoding antibody variable regions and, optionally, constant domains. Such DNA is known and / or readily available, for example, from commercial sources, DNA libraries (including, for example, phage antibody libraries), or can be synthesized. The DNA can be sequenced and manipulated chemically or by using molecular biology techniques, for example, to place one or more variable and / or constant domains in a suitable configuration, or to introduce codons, create cysteine ​​residues, modify, add, or delete amino acids, etc.

[0064] Non-limiting examples of antigen-binding fragments include (i) Fab fragments, (ii) F(ab')2 fragments, (iii) Fd fragments, (iv) Fv fragments, (v) single chain Fv (scFv) molecules, (vi) dAb fragments, and (vii) minimal recognition units consisting of amino acid residues mimicking a hypervariable region of an antibody (e.g., an isolated complementarity determining region (CDR) such as a CDR3 peptide), or a constrained FR3-CDR3-FR4 peptide. Domain-specific antibodies, single domain antibodies, domain deleted antibodies, chimeric antibodies, CDR grafted antibodies, diabodies, triabodies, tetrabodies, minibodies, nanobodies (e.g., monovalent nanobodies, bivalent nanobodies, etc.), small modular immunopharmaceuticals (SMIPs), and other engineered molecules such as shark variable IgNAR domains are also encompassed by the term "antigen-binding fragment" as used herein.

[0065] Antigen-binding fragments of antibodies typically contain at least one variable domain. The variable domain may be of any size or amino acid composition and will generally contain at least one CDR adjacent to or in frame with one or more framework sequences. In antigen-binding fragments having a VH domain combined with a VL domain, the VH and VL domains may be arranged relative to each other in any suitable configuration. For example, the variable region may be dimeric and include VH-VH, VH-VL or VL-VL dimers. Alternatively, the antigen-binding fragment of an antibody may contain a monomeric VH or VL domain.

[0066] In certain embodiments, an antigen-binding fragment of an antibody may comprise at least one variable domain covalently linked to at least one constant domain. Non-limiting exemplary configurations of variable and constant domains that may be found within an antigen-binding fragment of an antibody of the present disclosure include (i) VH-CH1, (ii) VH-CH2, (iii) VH-CH3, (iv) VH-CH1-CH2, (v) VH-CH1-CH2-CH3, (vi) VH-CH2-CH3, (vii) VH-CL, (viii) VL-CH1, (ix) VL-CH2, (x) VL-CH3, (xi) VL-CH1-CH2, (xii) VL-CH1-CH2-CH3, (xiii) VL-CH2-CH3, and (xiv) VL-CL. In any configuration of variable and constant domains, including any of the exemplary configurations listed above, the variable and constant domains may be directly linked to each other or may be linked by a complete or partial hinge or linker region. The hinge region may consist of at least two (e.g., 5, 10, 15, 20, 40, 60 or more) amino acids that provide a flexible or semi-flexible link between adjacent variable and / or constant domains in a single polypeptide molecule. Furthermore, antigen-binding fragments of antibodies of the present disclosure may comprise homodimers or heterodimers (or other multimers) of any of the variable and constant domain configurations listed above in non-covalent association (e.g., via disulfide bonds) with each other and / or with one or more monomeric VH or VL domains.

[0067] The term "antibody" as used herein also includes multispecific (eg, bispecific) antibodies.

[0068] Multispecific antibodies or antigen-binding fragments of antibodies typically comprise at least two different variable domains, each capable of specifically binding to a separate antigen or a different epitope on the same antigen. Any multispecific antibody format can be adapted for use in connection with the antibodies or antigen-binding fragments of antibodies of the present disclosure using routine techniques available in the art. For example, the present disclosure includes methods involving the use of bispecific antibodies in which one arm of the immunoglobulin is specific for PD-1 or a fragment thereof and the other arm of the immunoglobulin is specific for a second therapeutic target or is conjugated to a therapeutic moiety. Exemplary bispecific formats that can be used in connection with the present disclosure include, but are not limited to, for example, scFv-based or diabody bispecific formats, IgG-scFv fusions, dual variable domain (DVD)-Ig, quadroma, knob-into-hole, common light chain (e.g., common light chain with knob-into-hole), CrossMab, CrossFab, (SEED) body, leucine zipper, duobody, IgG1 / IgG2, dual acting Fab (DAF)-IgG, and Mab.sup.2 bispecific formats (see, e.g., Klein et al., 2012, mAbs 4:6, 1-11, and references cited therein, for a discussion of the foregoing formats). Bispecific antibodies can also be constructed using peptide / nucleic acid conjugation, e.g., using unnatural amino acids with orthogonal chemical reactivity to generate site-specific antibody-oligonucleotide conjugates that then self-assemble into multimeric complexes with defined composition, valency, and geometry. (See, e.g., Kazane et al., J. Am. Chem. Soc. [Epub: Dec. 4, 2012]).

[0069] The antibody used in the method of the present disclosure may be a human antibody. The term "human antibody" as used herein is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. Nevertheless, the human antibody of the present disclosure may include amino acid residues not encoded by human germline immunoglobulin sequences, for example in the CDRs, particularly in CDR3 (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo). However, the term "human antibody" as used herein is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, are grafted onto human framework sequences.

[0070] The antibody used in the disclosed method may be a recombinant human antibody. The term "recombinant human antibody" as used herein is intended to include all human antibodies prepared, expressed, created, or isolated by recombinant means, such as antibodies expressed using a recombinant expression vector (described in more detail below) transduced into a host cell, antibodies isolated from a recombinant combinatorial human antibody library (described in more detail below), antibodies isolated from an animal (e.g., a mouse) that is transgenic for human immunoglobulin genes (see, e.g., Taylor et al., (1992) Nucl. Acids Res. 20:6287-6295), or antibodies prepared, expressed, created, or isolated by any other means involving splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences. However, in certain embodiments, such recombinant human antibodies are subjected to in vitro mutagenesis (or, when animals transgenic for human Ig sequences are used, in vivo somatic mutagenesis) such that the amino acid sequences of the VH and VL regions of the recombinant antibodies, while derived from and related to human germline VH and VL sequences, may not naturally occur within the human antibody germline repertoire in vivo. According to certain embodiments, the antibody used in the methods of the present disclosure specifically binds to PD-1. The term "specifically binds" and the like means that the antibody or antigen-binding fragment thereof forms a complex with the antigen that is relatively stable under physiological conditions. Methods for determining whether an antibody specifically binds to an antigen are well known in the art and include, for example, equilibrium dialysis, surface plasmon resonance, and the like. For example, an antibody that "specifically binds" to PD-1, as used in the context of this disclosure, includes antibodies that bind to PD-1 or a portion thereof with a KD of less than about 500 nM, less than about 300 nM, less than about 200 nM, less than about 100 nM, less than about 90 nM, less than about 80 nM, less than about 70 nM, less than about 60 nM, less than about 50 nM, less than about 40 nM, less than about 30 nM, less than about 20 nM, less than about 10 nM, less than about 5 nM, less than about 4 nM, less than about 3 nM, less than about 2 nM, less than about 1 nM, or less than about 0.5 nM, as measured by a surface plasmon resonance assay. However, an isolated antibody that specifically binds human PD-1 may exhibit cross-reactivity to other antigens, such as PD-1 molecules of other (non-human) species.

[0071] According to certain exemplary embodiments of the present disclosure, an anti-PD-1 antibody or antigen-binding fragment thereof comprises a heavy chain variable region (HCVR), a light chain variable region (LCVR), and / or a complementarity determining region (CDR) comprising any of the amino acid sequences of the anti-PD-1 antibodies described in U.S. Patent No. 9,987,500. In certain exemplary embodiments, an anti-PD-1 antibody or antigen-binding fragment thereof that may be used in the context of the methods of the present disclosure comprises a heavy chain complementarity determining region (HCDR) of the heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:21, and a light chain complementarity determining region (LCDR) of the light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:22. According to certain embodiments, the anti-PD-1 antibody, or antigen-binding fragment thereof, comprises three HCDRs (HCDR1, HCDR2, and HCDR3) and three LCDRs (LCDR1, LCDR2, and LCDR3), where HCDR1 comprises the amino acid sequence of SEQ ID NO:23, HCDR2 comprises the amino acid sequence of SEQ ID NO:24, HCDR3 comprises the amino acid sequence of SEQ ID NO:25, LCDR1 comprises the amino acid sequence of SEQ ID NO:26, LCDR2 comprises the amino acid sequence of SEQ ID NO:27, and LCDR3 comprises the amino acid sequence of SEQ ID NO:28. In yet other embodiments, the anti-PD-1 antibody, or antigen-binding fragment thereof, comprises a HCVR comprising SEQ ID NO:21 and a LCVR comprising SEQ ID NO:22. In certain embodiments, the methods of the disclosure comprise the use of an anti-PD-1 antibody, wherein the antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:29. In some embodiments, the anti-PD-1 antibody comprises a light chain comprising the amino acid sequence of SEQ ID NO:30. An exemplary antibody comprising a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:21 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:22 is a fully human anti-PD-1 antibody also known as REGN2810 (cemiplimab; LIBTAYO®). According to certain exemplary embodiments, the methods of the disclosure include the use of REGN2810, or a biological equivalent thereof. As used herein, the term "biological equivalent" refers to an anti-PD-1 antibody or PD-1 binding protein or fragment thereof that is a pharmaceutical equivalent or pharmaceutical substitute that exhibits a rate and / or extent of absorption that does not differ significantly from that of REGN2810 when administered in the same molar dose under similar experimental conditions, either in a single dose or multiple doses.In the context of this disclosure, the term refers to an antigen binding protein that binds to PD-1 that has no clinically meaningful differences in safety, purity and / or potency from REGN2810.

[0072] Other anti-PD-1 antibodies that may be used in the context of the methods of the present disclosure include antibodies referred to or known in the art as, for example, nivolumab (U.S. Pat. No. 8,008,449), pembrolizumab (U.S. Pat. No. 8,354,509), MEDI0608 (U.S. Pat. No. 8,609,089), pidilizumab (U.S. Pat. No. 8,686,119), or any of the anti-PD-1 antibodies described in U.S. Pat. Nos. 6,808,710, 7,488,802, 8,168,757, 8,354,509, 8,779,105, or 8,900,587.

[0073] Anti-PD-1 antibodies used in the context of the methods of the present disclosure may have pH-dependent binding characteristics. For example, anti-PD-1 antibodies for use in the methods of the present disclosure may exhibit reduced binding to PD-1 at acidic pH compared to neutral pH. Alternatively, anti-PD-1 antibodies of the present disclosure may exhibit enhanced binding to their antigen at acidic pH compared to neutral pH. The term "acidic pH" includes pH values ​​less than about 6.2, e.g., about 6.0, 5.95, 5.9, 5.85, 5.8, 5.75, 5.7, 5.65, 5.6, 5.55, 5.5, 5.45, 5.4, 5.35, 5.3, 5.25, 5.2, 5.15, 5.1, 5.05, 5.0 or less. As used herein, the term "neutral pH" refers to a pH of about 7.0 to about 7.4. The expression "neutral pH" includes pH values ​​of about 7.0, 7.05, 7.1, 7.15, 7.2, 7.25, 7.3, 7.35, and 7.4.

[0074] In certain instances, "reduced binding to PD-1 at acidic pH compared to neutral pH" is expressed as the ratio of the KD value of an antibody that binds to PD-1 at acidic pH to the KD value of an antibody that binds to PD-1 at neutral pH (or vice versa). For example, an antibody or antigen-binding fragment thereof may be considered to exhibit "reduced binding to PD-1 at acidic pH compared to neutral pH for the purposes of this disclosure if the antibody or antigen-binding fragment thereof exhibits an acidic / neutral KD ratio of about 3.0 or greater. In certain exemplary embodiments, the acidic / neutral KD ratio for an antibody or antigen-binding fragment of the disclosure may be about 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 20.0, 25.0, 30.0, 40.0, 50.0, 60.0, 70.0, 100.0 or greater.

[0075] Antibodies with pH-dependent binding properties can be obtained, for example, by screening a population of antibodies for reduced binding (or increased binding) to a particular antigen at acidic pH compared to neutral pH.

[0076] In addition, modifications of the antigen-binding domain in amino acid concentration can produce antibodies with pH-dependent properties. For example, by replacing one or more amino acids in the antigen-binding domain (e.g., in the CDRs) with histidine residues, an antibody can be obtained that has reduced antigen binding at acidic pH compared to neutral pH. As used herein, the term "acidic pH" refers to a pH of 6.0 or less.

[0077] Bispecific anti-PSMA x anti-CD3 antibody According to certain exemplary embodiments of the present disclosure, the methods include administering a therapeutically effective amount of a bispecific antibody that specifically binds CD3 and PSMA. Such antibodies may be referred to herein, for example, as "anti-PSMA / anti-CD3," or "anti-PSMAxCD3," or "PSMAxCD3" bispecific antibodies, or other similar terms.

[0078] As used herein, the expression "bispecific antibody" refers to an immunoglobulin protein comprising at least a first antigen-binding domain and a second antigen-binding domain. In the context of the present disclosure, the first antigen-binding domain specifically binds to a first antigen (e.g., PSMA) and the second antigen-binding domain specifically binds to a second distinct antigen (e.g., CD3). Each antigen-binding domain of a bispecific antibody comprises a heavy chain variable domain (HCVR) and a light chain variable domain (LCVR), each of which comprises three CDRs. In the context of a bispecific antibody, the CDRs of the first antigen-binding domain may be designated with the prefix "A" and the CDRs of the second antigen-binding domain may be designated with the prefix "B". Thus, the CDRs of the first antigen-binding domain may be referred to herein as A-HCDR1, A-HCDR2, and A-HCDR3, and the CDRs of the second antigen-binding domain may be referred to herein as B-HCDR1, B-HCDR2, and B-HCDR3.

[0079] The first antigen-binding domain and the second antigen-binding domain are each connected to a separate multimerizing domain. As used herein, a "multimerizing domain" is any macromolecule, protein, polypeptide, peptide, or amino acid that has the ability to associate with a second multimerizing domain of the same or similar structure or composition. In the context of the present disclosure, the multimerizing component is the Fc portion of an immunoglobulin (including the CH2-CH3 domain), for example, the Fc portion of an IgG selected from the isotypes IgG1, IgG2, IgG3, and IgG4, as well as any allotype within each isotype group.

[0080] A bispecific antibody of the present disclosure typically comprises two multimerization domains, e.g., two Fc domains, each part of an individually distinct antibody heavy chain. The first and second multimerization domains may be of the same IgG isotype, e.g., IgG1 / IgG1, IgG2 / IgG2, IgG4 / IgG4, etc. Alternatively, the first and second multimerization domains may be of different IgG isotypes, e.g., IgG1 / IgG2, IgG1 / IgG4, IgG2 / IgG4, etc.

[0081] Any bispecific antibody format or technique may be used to generate the bispecific antibodies of the present disclosure. For example, an antibody or fragment thereof having a first antigen-binding specificity can be operatively linked (e.g., by chemical conjugation, genetic fusion, or non-covalent association, or otherwise) to one or more other molecular entities, such as another antibody or antibody fragment having a second binding specificity, to generate a bispecific antibody. Specific exemplary bispecific formats that may be used in connection with the present invention include, but are not limited to, e.g., scFv-based or diabody bispecific formats, IgG-scFv fusions, dual variable domain (DVD)-Ig, quadroma, knobs-into-holes, common light chains (such as common light chains with knobs-into-holes), CrossMab, CrossFab, (SEED) bodies, leucine zipper, duobodies, IgG1 / IgG2, dual acting Fab (DAF)-IgG, and Mab2 bispecific formats (see, e.g., Klein et al., 2012, mAbs 4:6, 1-11, and references cited therein for a discussion of the foregoing formats).

[0082] In the context of the bispecific antibodies of the present disclosure, the Fc domain may contain one or more amino acid changes (e.g., insertions, deletions, or substitutions) compared to a naturally occurring version of the wild-type Fc domain. For example, the present disclosure includes bispecific antibodies containing one or more modifications in the Fc domain that result in a modified Fc domain with a modified binding interaction (e.g., enhanced or decreased) between Fc and FcRn. In one embodiment, the bispecific antibody contains a modification in the CH2 or CH3 region that increases the affinity of the Fc domain for FcRn in an acidic environment (e.g., in an endosome with a pH ranging from about 5.5 to about 6.0). Non-limiting examples of such Fc modifications are disclosed in U.S. Patent Publication No. 2015 / 0266966, which is incorporated herein in its entirety.

[0083] The present disclosure also includes bispecific antibodies comprising a first CH3 domain and a second Ig CH3 domain, the first and second Ig CH3 domains differing from each other in at least one amino acid, the at least one amino acid difference reducing binding of the bispecific antibody to Protein A compared to a bispecific antibody lacking the amino acid difference. In one embodiment, the first Ig CH3 domain binds Protein A and the second Ig CH3 domain contains a mutation that reduces or eliminates Protein A binding, e.g., a H95R modification (according to IMGT exon numbering; H435R according to EU numbering). The second CH3 may further comprise a Y96F modification (Y436F according to IMGT and EU). See, e.g., U.S. Pat. No. 8,586,713. Further modifications that may be found in the second CH3 include: D16E, L18M, N44S, K52N, V57M, and V82I for IgG1 antibodies (D356E, L358M, N384S, K392N, V397M, and V422I in EU by IMGT), N44S, K52N, and V82I for IgG2 antibodies (N384S, K392N, and V422I in IMGT, EU), and Q15R, N44S, K52N, V57M, R69K, E79Q, and V82I for IgG4 antibodies (Q355R, N384S, K392N, V397M, R409K, E419Q, and V422I in EU by IMGT).

[0084] In certain embodiments, the Fc domain may be a chimera combining Fc sequences from two or more immunoglobulin isotypes. For example, the chimeric Fc domain may comprise part or all of the CH2 sequence from a human IgG1, human IgG2, or human IgG4 CH2 region, and part or all of the CH3 sequence from a human IgG1, human IgG2, or human IgG4. The chimeric Fc domain may also contain a chimeric hinge region. For example, the chimeric hinge may comprise an "upper hinge" sequence from a human IgG1, human IgG2, or human IgG4 hinge region combined with a "lower hinge" sequence from a human IgG1, human IgG2, or human IgG4 hinge region. A specific example of a chimeric Fc domain that may be included in any of the antibodies described herein comprises, from N-terminus to C-terminus, [IgG4 CH1]-[IgG4 upper hinge]-[IgG2 lower hinge]-[IgG4 CH2]-[IgG4 CH3]. Another example of a chimeric Fc domain that may be included in any of the antibodies described herein includes, from N-terminus to C-terminus, [IgG1 CH1]-[IgG1 upper hinge]-[IgG2 lower hinge]-[IgG4 CH2]-[IgG1 CH3]. These and other examples of chimeric Fc domains or chimeric heavy chain constant regions that may be included in any of the antibodies of the present disclosure are described in U.S. Patent Application Publication No. 2014 / 0243504, which is incorporated herein in its entirety. Chimeric Fc domains and chimeric heavy chain constant regions having these general structural arrangements, and variants thereof, may have altered Fc receptor binding, thereby affecting Fc effector function.

[0085] According to certain exemplary embodiments of the present disclosure, the bispecific anti-PSMA / anti-CD3 antibody or antigen-binding fragment thereof comprises a heavy chain variable region (A-HCVR and B-HCVR), a light chain variable region (A-LCVR and B-LCVR), and / or a complementarity determining region (CDR) comprising any of the amino acid sequences of the bispecific anti-PSMA / anti-CD3 antibodies described in U.S. Patent Publication No. 2017 / 0051074. In certain exemplary embodiments, bispecific anti-PSMA / anti-CD3 antibodies or antigen-binding fragments thereof that may be used in connection with the methods of the present disclosure include (a) a first antigen-binding arm comprising heavy chain complementarity determining regions (A-HCDR1, A-HCDR2, and A-HCDR3) of a heavy chain variable region (A-HCVR) comprising the amino acid sequence of SEQ ID NO:1 and light chain complementarity determining regions (A-LCDR1, A-LCDR2, and A-LCDR3) of a light chain variable region (A-LCVR) comprising the amino acid sequence of SEQ ID NO:2, and (b) a second antigen-binding arm comprising heavy chain CDRs (B-HCDR1, B-HCDR2, and B-HCDR3) comprising the amino acid sequence of SEQ ID NO:3, or SEQ ID NO:4, and light chain CDRs (B-LCDR1, B-LCDR2, and B-LCDR3) of a LCVR (B-LCVR) comprising the amino acid sequence of SEQ ID NO:2. According to a particular embodiment, A-HCDR1 comprises the amino acid sequence of SEQ ID NO:5, A-HCDR2 comprises the amino acid sequence of SEQ ID NO:6, A-HCDR3 comprises the amino acid sequence of SEQ ID NO:7, A-LCDR1 comprises the amino acid sequence of SEQ ID NO:8, A-LCDR2 comprises the amino acid sequence of SEQ ID NO:9, A-LCDR3 comprises the amino acid sequence of SEQ ID NO:10, said B-HCDR1 comprises the amino acid sequence of SEQ ID NO:11 or SEQ ID NO:14, said B-HCDR2 comprises the amino acid sequence of SEQ ID NO:12 or SEQ ID NO:15, B-HCDR3 comprises the amino acid sequence of SEQ ID NO:13 or SEQ ID NO:16, B-LCDR1 comprises the amino acid sequence of SEQ ID NO:8, said B-LCDR2 comprises the amino acid sequence of SEQ ID NO:9, and said B-LCDR3 comprises the amino acid sequence of SEQ ID NO:10.In yet other embodiments, the bispecific anti-PSMA / anti-CD3 antibody or antigen-binding fragment thereof comprises (a) a first antigen-binding arm comprising an HCVR comprising SEQ ID NO:1 (A-HCVR) and an LCVR comprising SEQ ID NO:2 (A-LCVR), and (b) a second antigen-binding arm comprising an HCDR comprising SEQ ID NO:3, or SEQ ID NO:4 (B-HCDR) and an LCVR comprising SEQ ID NO:2 (B-LCVR). In certain exemplary embodiments, the bispecific anti-PSMAxCD3 antibody comprises a PSMA-binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO:17 and a light chain comprising the amino acid sequence of SEQ ID NO:18, and a CD3-binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO:19 and a light chain comprising the amino acid sequence of SEQ ID NO:18. In certain exemplary embodiments, the bispecific anti-PSMAxCD3 antibody comprises a PSMA-binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO:17 and a light chain comprising the amino acid sequence of SEQ ID NO:18, and a CD3-binding arm comprising a heavy chain comprising the amino acid sequence of SEQ ID NO:20 and a light chain comprising the amino acid sequence of SEQ ID NO:18. An exemplary bispecific anti-PSMA / anti-CD3 antibody for use in the methods of the disclosure comprising (a) a first antigen-binding arm comprising a HCVR comprising SEQ ID NO:1 (A-HCVR) and a LCVR comprising SEQ ID NO:2 (A-LCVR), and (b) a second antigen-binding arm comprising a HCVR comprising SEQ ID NO:4 (B-HCVR) and a LCVR comprising SEQ ID NO:2 (B-LCVR) is REGN4336 (referred to herein as "PSMA / CD3-002").

[0086] Combination therapy According to certain embodiments, the method of the disclosure comprises administering to a subject an anti-PSMA / anti-CD3 bispecific antibody in combination with an anti-PD-1 antibody. In certain embodiments, the method of the disclosure comprises administering an antibody of additive or synergistic activity to treat a PSMA-expressing cancer, preferably prostate cancer. As used herein, the term "in combination with" means that the anti-PSMA / anti-CD3 bispecific antibody is administered before, after, or simultaneously with the anti-PD-1 antibody. The term "in combination with" also includes sequential or simultaneous administration of the anti-PD-1 antibody and the bispecific anti-PSMA / anti-CD3 antibody. For example, when administered "prior to" the bispecific anti-PSMA / anti-CD3 antibody, the anti-PD-1 antibody may be administered more than 150 hours, about 150 hours, about 100 hours, about 72 hours, about 60 hours, about 48 hours, about 36 hours, about 24 hours, about 12 hours, about 10 hours, about 8 hours, about 6 hours, about 4 hours, about 2 hours, about 1 hour, about 30 minutes, about 15 minutes, or about 10 minutes before administration of the bispecific anti-PSMA / anti-CD3 antibody. When administered "after" the bispecific anti-PSMA / anti-CD3 antibody, the anti-PD-1 antibody may be administered about 10 minutes, about 15 minutes, about 30 minutes, about 1 hour, about 2 hours, about 4 hours, about 6 hours, about 8 hours, about 10 hours, about 12 hours, about 24 hours, about 36 hours, about 48 hours, about 60 hours, about 72 hours, or more than 72 hours after administration of the bispecific anti-PSMA / anti-CD3 antibody. "Concurrent administration" with the bispecific anti-PSMA / anti-CD3 antibody means that the anti-PD-1 antibody is administered to the subject in a separate dosage form within less than 5 minutes of (before, after, or simultaneously with) administration of the bispecific anti-PSMA / anti-CD3 antibody, or is administered to the subject as a single combined dosage formulation including both the anti-PD-1 antibody and the bispecific anti-PSMA / anti-CD3 antibody.

[0087] In certain embodiments, the methods of the disclosure include administration of a third therapeutic agent, where the third therapeutic agent is an anti-cancer agent. In certain embodiments, the methods of the disclosure include administration of an anti-PD-1 antibody and an anti-PSMA / anti-CD3 bispecific antibody in combination with radiation therapy, surgery, or other anti-cancer therapy to generate long-term durable anti-tumor responses and / or enhance survival in patients with PSMA-expressing cancer.

[0088] In some embodiments, the methods of the disclosure include administering radiation therapy before, simultaneously with, or after administering the anti-PD-1 antibody and the bispecific anti-PSMA / anti-CD3 antibody to the cancer patient. For example, radiation therapy may be administered in one or more doses to the neoplastic lesion after administration of one or more doses of the antibody. In some embodiments, radiation therapy may be administered locally to the neoplastic lesion after systemic administration of the anti-PD-1 antibody and / or the bispecific anti-PSMA / anti-CD3 antibody to increase the local immunogenicity of the patient's tumor (adjuvinating radiation) and / or kill tumor cells (ablative radiation).

[0089] Pharmaceutical Compositions and Administration The present disclosure includes methods comprising administering a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody, to a subject, where one or more antibodies are contained within a separate or combined (single) pharmaceutical composition. The pharmaceutical compositions of the present disclosure may be formulated with suitable carriers, excipients, and other agents that provide for suitable transport, delivery, tolerability, etc. Numerous suitable formulations can be found in a formulary known to every pharmacist: Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa. These formulations include, for example, powders, pastes, ointments, jellies, waxes, oils, lipids, lipids (cationic or anionic) containing vesicles (such as LIPOFECTIN™), DNA conjugates, anhydrous absorption pastes, oil-in-water and water-in-oil emulsions, emulsions carbowax (polyethylene glycols of various molecular weights), semi-solid gels, and semi-solid mixtures containing carbowax. See also Powell et al., "Compendium of excipients for parenteral formulations," PDA (1998) J Pharm Sci Technol 52:238-311.

[0090] Various delivery systems are known and can be used to administer the pharmaceutical compositions of the present disclosure, such as encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing mutant viruses, receptor-mediated endocytosis, and the like (see, e.g., Wu et al., 1987, J. Biol. Chem. 262:4429-4432).

[0091] Methods of administration include, but are not limited to, intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous, intranasal, epidural, and oral routes. The compositions can be administered by any convenient route, for example, by infusion or bolus injection, or by injection, and can also be administered together with other biologically active agents.

[0092] The pharmaceutical composition of the present disclosure can be delivered subcutaneously or intravenously with a standard needle and syringe. Furthermore, for subcutaneous delivery, a pen delivery device is easily adapted to deliver the pharmaceutical composition of the present disclosure. Such a pen delivery device can be reusable or disposable. A reusable pen delivery device generally utilizes a replaceable cartridge containing the pharmaceutical composition. Once all of the pharmaceutical composition inside the cartridge has been administered and the cartridge is empty, the empty cartridge can be easily discarded and replaced with a new cartridge containing the pharmaceutical composition. The pen delivery device can then be reused. In a disposable pen delivery device, there is no replaceable cartridge. Rather, the disposable pen delivery device is sold pre-filled with the pharmaceutical composition held in a reservoir inside the device. Once the reservoir is emptied of the pharmaceutical composition, the entire device is discarded.

[0093] A number of reusable pen delivery devices and / or auto-injector delivery devices can be used to subcutaneously deliver the pharmaceutical formulations of the present disclosure. Examples include, but are not limited to, AUTOPEN™ (Owen Mumford, Inc., Woodstock, UK), DISETRONIC™ pen (Disetronic Medical Systems, Bergdorf, Switzerland), HUMALOG MIX 75 / 25™ pen, HUMALOG™ pen, HUMALIN 70 / 30™ pen (Eli Lilly and Co., Indianapolis, IN), NOVOPEN™ I, II, and III (Novo Nordisk, Copenhagen, Denmark), NOVOPEN JUNIOR™ (Novo Nordisk, Copenhagen, Denmark), BD™ pen (Becton Dickinson, Franklin Lakes, NJ), OPTIPEN™, OPTIPEN PRO™, OPTIPEN ... Examples of disposable pen and / or autoinjector delivery devices having application in subcutaneous delivery of pharmaceutical compositions of the present disclosure include, but are not limited to, the SOLOSTAR Pen (sanofi-aventis), FLEXPEN (Novo Nordisk), and KWIKPEN (Eli Lilly), SURECLICK Autoinjector (Amgen, Thousand Oaks, CA), PENLET (Haselmeier, Stuttgart, Germany), EPIPEN (Dey, LP), and HUMIRA Pen (Abbott Labs, Abbott Park IL), to name a few.

[0094] In certain circumstances, pharmaceutical compositions can be delivered in a controlled release system. In one embodiment, pumps can be used. In another embodiment, polymeric materials can be used. See Medical Applications of Controlled Release, Langer and Wise (eds.), 1974, CRC Pres., Boca Raton, Fla. In yet another embodiment, the controlled release system can be placed in the vicinity of the target of the composition, thus requiring only a fraction of the systemic dose (see, for example, Goodson, 1984, in Medical Applications of Controlled Release, supra, vol. 2, pp. 115-138). Other controlled release systems are discussed in the review by Langer, 1990, Science 249: 1527-1533.

[0095] The injectable preparations may include dosage forms for intravenous, subcutaneous, intradermal, and intramuscular injections, drip infusions, and the like. These injectable preparations may be prepared by known methods. For example, the injectable preparations may be prepared by dissolving, suspending, or emulsifying the above-mentioned antibody or its salt in a sterile aqueous or oily medium conventionally used for injections. Aqueous media for injection include, for example, physiological saline, isotonic solutions containing glucose, and other auxiliary agents, which may be used in combination with suitable solubilizers. The injection solution thus prepared is preferably filled into a suitable ampoule.

[0096] Advantageously, the pharmaceutical compositions for the above-mentioned uses are prepared in dosage forms with unit doses suitable for fitting the dose of the active ingredient. Such dosage forms in unit doses include, for example, vials or pre-filled syringes.

[0097] Dosing regimen The disclosure includes methods comprising administering to a subject a bispecific anti-PSMAxCD3 antibody, alone or in combination with an anti-PD-1 antibody, at a dosing frequency of about 4 times per week, twice per week, once per week, once per 2 weeks, once per 3 weeks, once per 4 weeks, once per 5 weeks, once per 6 weeks, once per 8 weeks, once per 12 weeks, or less frequently, so long as a therapeutic response is achieved.

[0098] According to certain embodiments of the present disclosure, multiple doses of bispecific anti-PSMA / anti-CD3 antibodies alone or in combination with anti-PD-1 antibodies can be administered to a subject over a defined time course. The method according to this aspect of the disclosure includes administering one or more doses of bispecific anti-PSMA / anti-CD3 antibodies alone or in combination with one or more doses of anti-PD-1 antibodies to a subject one or more times in a sequential manner. As used herein, "sequential administration" means that each dose of antibody is administered to a subject at different times, e.g., on different days separated by a predetermined interval (e.g., hours, days, weeks, or months). The present disclosure includes methods that include sequentially administering to a patient one initial dose of antibody, followed by one or more second doses of antibody, and optionally then one or more third doses of antibody.

[0099] The terms "initial dose", "secondary dose" and "tertiary dose" refer to the temporal order of administration. Thus, an "initial dose" is a dose administered at the beginning of a treatment regimen (also referred to as a "baseline dose"), a "secondary dose" is a dose administered after the initial dose, and a "tertiary dose" is a dose administered after the secondary dose. The initial dose, secondary dose, and tertiary dose may all contain the same amount of antibody (anti-PD-1 antibody or bispecific antibody). However, in certain embodiments, the amounts contained in the initial dose, secondary dose, and / or tertiary dose differ from each other (e.g., adjusted up or down) during the course of treatment. In certain embodiments, one or more doses (e.g., 1, 2, 3, 4, or 5) are administered as a "loading dose" at the beginning of a treatment regimen, followed by subsequent doses (e.g., "maintenance doses") administered on a less frequent basis. In one exemplary embodiment of the present disclosure, each secondary dose and / or tertiary dose is administered ½ to 14 weeks after the immediately preceding dose (e.g., ½ week, 1 week, 1 1 / 2 weeks, 2 weeks, 2 1 / 2 weeks, 3 weeks, 3 1 / 2 weeks, 4 weeks, 4 1 / 2 weeks, 5 weeks, 5 1 / 2 weeks, 6 weeks, 6 1 / 2 weeks, 7 weeks, 7 1 / 2 weeks, 8 weeks, 8 1 / 2 weeks, 9 weeks, 9 1 / 2 weeks, 10 weeks, 10 1 / 2 weeks, 11 weeks, 11 1 / 2 weeks, 12 weeks, 12 1 / 2 weeks, 13 weeks, 13 1 / 2 weeks, 14 weeks, 14 1 / 2 weeks, or more).

[0100] As used herein, the phrase "the immediately preceding dose" refers to a dose of a bispecific anti-PSMA / anti-CD3 antibody (and / or anti-PD-1 antibody) in a series of multiple doses that is administered to a patient prior to administration of the immediately succeeding dose in the series, with no intervening doses.

[0101] The method according to this aspect of the disclosure may include administering any number of secondary and / or tertiary doses of the bispecific anti-PSMA / anti-CD3 antibody (and / or anti-PD-1 antibody) to the patient. For example, in certain embodiments, the patient is administered only a single secondary dose. In other embodiments, the patient is administered two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) secondary doses. Similarly, in certain embodiments, the patient is administered only a single tertiary dose. In other embodiments, the patient is administered two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) tertiary doses.

[0102] In embodiments including multiple secondary doses, each secondary dose may be administered with the same frequency as the other secondary doses. For example, each secondary dose may be administered to the patient 1, 2, or 3 weeks (e.g., 1 week or 3 weeks) after the immediately preceding dose. Similarly, in embodiments including multiple tertiary doses, each tertiary dose may be administered with the same frequency as the other tertiary doses. For example, each tertiary dose may be administered to the patient 1-4 weeks (e.g., 1 week or 3 weeks) after the immediately preceding dose. Alternatively, the frequency with which the secondary and / or tertiary doses are administered to the patient may vary over the course of the treatment regimen. The frequency of administration may also be adjusted by the physician during the course of treatment depending on the needs of the individual patient after clinical testing.

[0103] In certain embodiments, one or more doses of a bispecific anti-PSMA / anti-CD3 antibody (e.g., and anti-PD-1 antibody) are administered more frequently (twice weekly, once weekly, once every two weeks, or once every three weeks) at the start of a treatment regimen as an "induction dose" followed by subsequent doses ("consolidation doses" or "maintenance doses") administered the same or less frequently (e.g., once every 4-12 weeks).

[0104] The present disclosure includes methods comprising sequentially administering a bispecific anti-PSMA / anti-CD3 antibody, alone or in combination with an anti-PD-1 antibody, to a patient to treat prostate cancer (e.g., metastatic castration-resistant prostate cancer). In some embodiments, the methods comprise administering one or more doses of a bispecific anti-PSMA / anti-CD3 antibody, optionally prior to or following administration of one or more doses of an anti-PD-1 antibody. In certain embodiments, the methods comprise administering a single dose of an anti-PD-1 antibody, followed by administration of one or more doses of a bispecific anti-PSMA / anti-CD3 antibody. In some embodiments, one or more doses of about 0.1 mg / kg to about 20 mg / kg (e.g., 100-600 mg) of an anti-PD-1 antibody can be administered followed by one or more doses of about 0.1 mg / kg to about 20 mg / kg (e.g., 0.01-1000 mg) of a bispecific antibody to inhibit tumor growth and / or prevent tumor recurrence in a subject with prostate cancer. In some embodiments, the bispecific antibody or combinations thereof provide an increased anti-tumor effect (e.g., more tumor growth is inhibited and more tumor recurrence is prevented compared to untreated subjects or subjects administered either antibody, respectively, as monotherapy). Alternative embodiments of the present disclosure relate to the co-administration of an anti-PD-1 antibody and a bispecific antibody administered in separate dosages at similar or different frequencies compared to the anti-PD-1 antibody. In some embodiments, the bispecific antibody is administered before, after, or simultaneously with the anti-PD-1 antibody. In certain embodiments, the bispecific antibody is administered as a single dosage formulation with the anti-PD-1 antibody.

[0105] Dosage The amount of bispecific anti-PSMA / anti-CD3 antibody, and optionally anti-PD-1 antibody, administered to a subject according to the methods of the present disclosure is generally a therapeutically effective amount. As used herein, the phrase "therapeutically effective amount" refers to an amount of antibody (anti-PD-1 antibody or bispecific anti-PSMA / anti-CD3 antibody) that results in one or more of the following, compared to an untreated subject or a subject administered either antibody as a monotherapy: (a) a reduction in the severity of cancer (e.g., prostate cancer) or the duration of symptoms of cancer; (b) inhibition of tumor growth or an increase in tumor necrosis, tumor shrinkage, and / or tumor disappearance; (c) a delay in tumor growth and development; (d) inhibition or delay or cessation of tumor metastasis; (e) prevention of recurrence of tumor growth; (f) an increase in the survival of a subject with cancer (e.g., prostate cancer); and / or (g) a reduction in the use or need for conventional anti-cancer therapy (e.g., a reduction or elimination of the use of chemotherapeutic or cytotoxic agents).

[0106] In the case of bispecific anti-PSMA / anti-CD3 antibodies, a therapeutically effective amount is from about 0.01 milligrams (mg) to about 2000 mg, about 0.01 mg, about 0.03 mg, about 0.09 mg, about 0.1 mg, about 0.2 mg, about 0.3 mg, about 0.4 mg, about 0.5 mg, about 0.6 mg, about 0.7 mg, about 0.8 mg, about 0.9 mg, about 1 mg, about 3 mg, about 4 mg, about 5 mg, about 6 mg, about 7 mg, about 8 mg, about 9 mg, about 10 mg, about 20 mg, about 30 mg, about 40 mg, about 50 mg, about 75 mg, about 100 mg, about 125 mg, about 150 mg, about 200 mg, about 250 mg The amount of bispecific anti-PSMA / anti-CD3 antibody may be about 300 mg, about 350 mg, about 400 mg, about 450 mg, about 500 mg, about 550 mg, about 600 mg, about 650 mg, about 700 mg, about 750 mg, about 800 mg, about 850 mg, about 900 mg, about 950 mg, or about 1000 mg. In certain embodiments, 0.03 mg, 0.09 mg, 0.1 mg, 0.3 mg, 0.9 mg, 1 mg, 3 mg, 9 mg, 10 mg, 30 mg, 90 mg, 100 mg, 300 mg, or 900 mg of the bispecific anti-PSMA x anti-CD3 antibody is administered to a subject (e.g., once a week or once every three weeks) to treat a PSMA-expressing cancer or prostate cancer (e.g., metastatic and / or castration-resistant prostate cancer).

[0107] In the case of an anti-PD-1 antibody, the therapeutically effective amount is about 0.05 mg to about 600 mg, for example, about 0.05 mg, about 0.1 mg, about 1.0 mg, about 1.5 mg, about 2.0 mg, about 10 mg, about 20 mg, about 30 mg, about 40 mg, about 50 mg, about 60 mg, about 70 mg, about 80 mg, about 90 mg, about 100 mg, about 110 mg, about 120 mg, about 130 mg, about 140 mg, about 150 mg, about 160 mg, about 170 mg, about 180 mg, about 190 mg, about 200 mg, about 210 mg, about 220 mg, about 230 mg, about 240 mg, about 250 mg, about 260 mg, about 270 mg, about 280 mg, about 290 mg, about 300 mg, about 310 mg, about 320 mg, about 330 mg, about 340 mg, about 350 mg, about 360 mg, about 370 mg, about 380 mg, about 390 mg, about 400 mg, about 410 mg, about 420 mg, about 430 mg, about 440 mg, about 450 mg, about 460 mg, about 470 mg, about 480 mg, about 490 mg, about 500 mg, about 510 mg, about 520 mg, about 530 mg, about 540 mg, about 550 mg, about 560 mg, about 570 mg, about 580 mg, about 590 mg, about 600 mg, about 610 mg, about 620 mg, about 630 mg, about 640 mg, The dose may be about 280 mg, about 290 mg, about 300 mg, about 310 mg, about 320 mg, about 330 mg, about 340 mg, about 350 mg, about 360 mg, about 370 mg, about 380 mg, about 390 mg, about 400 mg, about 410 mg, about 420 mg, about 430 mg, about 440 mg, about 450 mg, about 460 mg, about 470 mg, about 480 mg, about 490 mg, about 500 mg, about 510 mg, about 520 mg, about 530 mg, about 540 mg, about 550 mg, about 560 mg, about 570 mg, about 580 mg, about 590 mg, or about 600 mg of an anti-PD-1 antibody. In certain embodiments, 300 mg to 400 mg of an anti-PD-1 antibody is administered to a subject (e.g., once every three weeks) in combination with a bispecific antibody to treat a PSMA-expressing cancer or prostate cancer (e.g., metastatic and / or castration-resistant prostate cancer). In certain embodiments, 350 mg of an anti-PD-1 antibody is administered to a subject (e.g., once every three weeks) in combination with a bispecific antibody to treat a PSMA-expressing cancer or prostate cancer (e.g., metastatic and / or castration-resistant prostate cancer).

[0108] The amounts of bispecific anti-PSMA / anti-CD3 antibody and anti-PD-1 antibody contained in each dose may be expressed in milligrams per kilogram (i.e., mg / kg) of the subject's body weight. In certain embodiments, the bispecific anti-PSMA / anti-CD3 antibody and optionally the anti-PD-1 antibody used in the methods of the present disclosure may be administered to a subject at a dose of about 0.0001 to about 100 mg / kg of the subject's body weight. For example, the bispecific anti-PSMA / anti-CD3 antibody may be administered at a dose of about 0.1 mg / kg to about 20 mg / kg of the patient's body weight, and the optional anti-PD-1 antibody may be administered at a dose of about 0.1 mg / kg to about 20 mg / kg of the patient's body weight.

[0109] A summary of the sequences referred to herein and their corresponding SEQ ID NOs is provided in Table 1 below. [Table 1] EXAMPLES

[0110] The following examples are provided to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the methods and compositions of the present invention, and are not intended to limit the scope of what the inventor regards as his invention. Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperatures, etc.), but some experimental error and deviation should be accounted for. Unless otherwise indicated, parts are parts by weight, molecular weight is average molecular weight, temperature is degrees Celsius, and pressure is at or near atmospheric pressure. EXAMPLES

[0111] Generation of a bispecific antibody that binds prostate-specific membrane antigen (PSMA) and CD3 The present disclosure provides bispecific antibodies that bind to CD3 and prostate-specific membrane antigen (PSMA), which are also referred to herein as anti-PSMA x anti-CD3 bispecific antibodies or anti-PSMA x CD3 bispecific antibodies. The anti-PSMA portion of the anti-PSMA x anti-CD3 bispecific antibodies is useful for targeting tumor cells expressing PSMA, and the anti-CD3 portion of the bispecific antibodies is useful for activating T cells. The simultaneous binding of PSMA on tumor cells and CD3 on T cells promotes direct killing (cytolysis) of the targeted tumor cells by the activated T cells. Bispecific antibodies were constructed using standard methodologies that contain an anti-PSMA specific binding domain and an anti-CD3 specific binding domain, where the anti-PSMA antigen binding domain and the anti-CD3 antigen binding domain each contain a distinct HCVR paired with a common LCVR. The bispecific antibodies were constructed utilizing a heavy chain derived from an anti-CD3 antibody, a heavy chain derived from an anti-PSMA antibody, and a common light chain.

[0112] An overview of the antigen-binding domain components of the various anti-PSMAxCD3 bispecific antibodies constructed is provided in Table 2. [Table 2] EXAMPLES

[0113] Binding Affinities of Exemplary Bispecific Antibodies Measured by FACS Analysis In this example, the ability of the anti-PSMA x anti-CD3 bispecific antibodies described in Example 1 to bind via FACS to human PSMA-expressing cell lines and human and cynomolgus CD3-expressing cell lines was determined.

[0114] Briefly, 2x105 cells / well of human CD3-expressing Jurkat, cynomolgus T, or human PSMA-specific expressing cells were incubated with serial dilutions of bispecific antibodies for 30 min at 4°C. After incubation, cells were washed and goat F(ab')2 anti-human Fc gamma PE-labeled secondary (Jackson Immunolabs) was added to the cells for an additional 30 min. Cells were then washed, resuspended in cold PBS + 1% BSA, and analyzed via flow cytometry on a BD FACS Canto II.

[0115] For FACS analysis, cells were gated by forward scatter height versus forward scatter area for single event selection, followed by side scatter and forward scatter. EC50 of cell binding titration was determined using Prism software. Values ​​were calculated using 4-parameter nonlinear regression analysis. [Table 3]

[0116] As shown in Table 2, the anti-PSMA x anti-CD3 bispecific antibodies tested demonstrated specificity of binding to human PSMA-expressing B16F10.9 / hPSMA and 22RV1 cell lines via FACS. The detection limit of FACS binding is 1 μM EC50.

[0117] As shown in Table 2, the CD3 binding arms of each PSMAxCD3 bispecific antibody exhibited a range of cell binding affinities (EC50 range of 15-300 nM) to human CD3 expressing Jurkat cells. Importantly, CD3 arms that showed weak or undetectable binding to human CD3 heterodimer protein via surface plasmon resonance (see Table 4 below) also correlated with weak or observable binding to Jurkat cells (i.e., CD3-VH-G5). Both tested bispecific antibodies showed similar cell binding to their respective PSMA-expressing cell lines, confirming that bispecific pairing with the individual CD3 arms does not affect or reduce PSMA-specific binding. EXAMPLES

[0118] Binding Affinities of Exemplary Antibodies Measured by Surface Plasmon Resonance Binding Assay The binding affinity and kinetic constants of the anti-PSMA x anti-CD3 bispecific antibody to the soluble heterodimeric hCD3mFc protein were determined by surface plasmon resonance at 37° C. using an antigen capture format (Table 4). Measurements were performed on a Sierra Sensors MASS-1 instrument.

[0119] In the antigen capture format, the MASS-1 high density amine sensor surface was derivatized with a goat anti-mouse IgG2a polyclonal antibody (Southern Biotech). Soluble heterodimeric CD3 protein was captured and the respective antibody was injected over the captured antigen.

[0120] The kinetic association (ka) and dissociation (kd) rate constants were determined by processing the data and fitting to a 1:1 binding model using MASS-1 Analyser R2 curve fitting software. The binding dissociation equilibrium constant (KD) and dissociation half-life (t1 / 2) were calculated from the kinetic rate constants as follows: KD (M) = kd / ka, and t1 / 2 (min) = [ln2 / (60*kd)]. [Table 4]

[0121] As shown in Table 4, the anti-PSMA x anti-CD3 bispecific antibody maintained very weak binding to soluble CD3 in surface plasmon resonance binding assays, e.g., had a KD value of 334 nM or showed no detectable binding. EXAMPLES

[0122] T cell activation and tumor-specific cytotoxicity exhibited by bispecific antibodies measured in vitro In this example, specific killing of PSMA-expressing target cells in the presence of an anti-PSMA x anti-CD3 bispecific antibody was monitored via flow cytometry. As previously reported, the bispecific antibody showed broad affinity for CD3 protein and CD3-expressing cell lines. This same pair of bispecific antibodies was tested for its ability to induce naive human T cells to redirect killing to target-expressing cells.

[0123] Briefly, PSMA-expressing (C4-2, 22Rv1, and TRAMPC2_PSMA) cell lines were labeled with 1 μM of the fluorescent tracking dye Violet Cell Tracker. After labeling, cells were cultured overnight at 37°C. Separately, human PBMCs were cultured in supplemented RPMI medium at 1×106 cells / mL and incubated overnight at 37°C to enrich for lymphocytes by depleting adherent macrophages, dendritic cells, and localized monocytes. The next day, target cells were co-cultured with naïve PBMCs (effector / target cell ratio 4:1) depleted of adherent cells and serial dilutions of relevant bispecific antibodies or isotype controls for 48 h at 37°C. Cells were removed from cell culture plates with enzyme-free cell lysis buffer and analyzed by FACS.

[0124] For FACS analysis, cells were stained with dead / live far-red cell tracker (Invitrogen). 5x105 counting beads were added to each well immediately prior to FACS analysis. 1x104 beads were collected for each sample. To assess specificity of killing, cells were gated on the live violet labeled population. The percentage of the live population was recorded and used to calculate viability.

[0125] T cell activation was assessed by incubating cells with directly conjugated antibodies against CD2 and CD69 and reporting the percentage of activated (CD69+) T cells among total T cells (CD2+).

[0126] As the results in Table 5 show, depletion of PSMA-expressing cells was observed with anti-PSMA x anti-CD3 bispecific antibodies. The bispecific antibodies tested activated human T cells and depleted target cells with EC50 in the picomolar range. Furthermore, the observed target cell lysis was associated with upregulation of CD69 cells, pM EC50.

[0127] Importantly, the results of this example demonstrate that bispecific antibodies utilizing a CD3-binding arm that showed weak to non-observable binding to CD3 protein or CD3-expressing cells (i.e., CD3-VH-G5) still retained the ability to activate T cells and exhibited potent cytotoxicity of tumor antigen-expressing cells. [Table 5] EXAMPLES

[0128] Anti-PSMA / anti-CD3 bispecific antibodies show potent anti-tumor efficacy in vivo To determine the in vivo efficacy of exemplary anti-PSMA / anti-CD3 bispecific antibodies, studies were performed in immunodeficient mice bearing human prostate cancer xenografts. Additional testing was also performed in immunocompetent mice bearing mouse prostate cancer xenografts engineered to express human PSMA.

[0129] Efficacy of anti-PSMA / anti-CD3 bispecific antibodies in human tumor xenograft models To evaluate the in vivo efficacy of the anti-PSMA / anti-CD3 bispecific in human tumor xenograft studies, NOD scid gamma (NSG) mice (Jackson Laboratories, Bar Harbor, Maine) were co-implanted with human peripheral blood mononuclear cells (PBMCs) along with C4-2 human prostate tumor cells, which endogenously express PSMA.

[0130] Briefly, 5x106 C4-2 cells (MD Anderson, TX) were implanted subcutaneously into the right flank of male NSG mice with 1x106 human PBMCs (ReachBio, LLC, WA) in a 50:50 mixture of Matrigel matrix (BD Biosciences). Mice were treated intraperitoneally with 0.1 mg / kg PSMA / CD3-002 on days 0, 4, and 7 after tumor implantation.

[0131] In an additional xenogeneic neoplasia model, anti-PSMA x anti-CD3 bispecifics were tested in mice engrafted with human hematopoietic anti-CD34+ stem cells. Briefly, newborn SIRPα BALB / c-Rag2- IL2rγ- (BRG) pups were engrafted with hCD34+ fetal liver cells. 3-6 months later, hCD34-engrafted BRG mice were then transplanted with C4-2 cells (5x106 s.c. in Matrigel). Eight days later, mice were treated with 10ug of PSMA / CD3-001 or isotype control antibody, followed by 2x / weekly doses throughout the study.

[0132] In all studies, tumor size was measured twice weekly using calipers and tumor volume was calculated as volume = (length × width2)2.

[0133] As the results in Table 6 show, both bispecific antibodies tested in the xenogeneic model described above were effective in inhibiting tumor growth compared to treatment with an isotype control.

[0134] Efficacy of anti-PSMA / anti-CD3 bispecific antibodies in immunocompetent tumor models Furthermore, the anti-PSMA × anti-CD3 bispecific was evaluated for antitumor activity in an immunocompetence model: mice humanized for the three chains of CD3 (δγε) as well as PSMA were implanted with the variant murine prostate cancer cell line TRAMP-C2 transfected with human PSMA.

[0135] Before the study began, a tumorigenic cell line variant TRAMP-C2_hPSMAv#1 was generated. Briefly, 7.5x106 TRAMP-C2_hPSMA cells were subcutaneously implanted into the right flank of male mice humanized for CD3 and PSMA. The tumors were excised, cut into 3mm fragments, and then implanted into the right flank of new male humanized mice. The tumors arising from the implanted tumor fragments were then harvested and disaggregated into single cell suspensions. These cells (TRAMP-C2_hPSMAv#1) were then cultured in vitro under G418 selection. 4.106 cells of this variant cell line were then implanted into the right flank of male PSMA / CD3 humanized mice for bispecific antibody efficacy studies.

[0136] Humanized PSMA / CD3 mice implanted with TRAMPC2_hPSMAv#1 were treated twice weekly with 100ug or 10ug of anti-PSMA x anti-CD3 bispecific antibody PSMA / CD3-001 or isotype control starting from the day of tumor implantation. Serum cytokine levels 4 hours after injection were also examined, as well as splenic T cell levels. The study was terminated on day 27.

[0137] As shown by the results in Table 7, the anti-PSMA x anti-CD3 bispecific antibody demonstrated efficacy in significantly delaying tumor growth between treatment groups. Minimal cytokine release was observed following administration of PSMA / CD3-001, likely due to weak binding of anti-CD3.

[0138] Notably, in the absence of PSMA-expressing tumor cells, no T cell activation was observed.

[0139] Furthermore, in non-tumor-bearing mice, blood samples were taken 4 hours after PSMAxCD3 bispecific antibody treatment to determine serum cytokine levels. Transient increases in the levels of cytokines interferon gamma (IFN-g), tumor necrosis factor (TNF), interleukin-2 (IL-2), and interleukin-6 (IL-6) were determined and were dose-dependent (data not shown). [Table 6] [Table 7] EXAMPLES

[0140] A Phase 1 / 2 Study of a Bispecific Anti-PSMA x Anti-CD3 Antibody, Alone or in Combination with an Anti-PD-1 Antibody, in Patients with Metastatic Castration-Resistant Prostate Cancer This is an open-label, Phase 1 / 2, first-in-human, multicenter, dose-escalation study with cohort expansion to evaluate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of PSMA / CD3-002 administered subcutaneously alone and in combination with intravenous cemiplimab in patients with metastatic castration-resistant prostate cancer (mCRPC). Patients must have received at least two prior systemic therapies approved for metastatic and / or castration-resistant disease, including second-generation antiandrogen therapy. PSMA / CD3-002 as monotherapy will be administered weekly, but may be extended to once every 3 weeks after identification of the minimum pharmacologically active dose. PSMA / CD3-002 in combination with cemiplimab (350 mg) will be administered once every 3 weeks after a 4-week PSMA / CD3-002 monotherapy lead-in cycle. Study therapy will be administered until disease progression, intolerable adverse events, withdrawal of consent, or study discontinuation criteria are met.

[0141] The primary objective in dose escalation is to evaluate the safety, tolerability, PK, and recommended phase 2 dosing regimen (RP2DR) of PSMA / CD3-002 alone and in combination with cemiplimab. Expansion cohort(s) will be enrolled once RP2DRs are determined. During the expansion phase, the primary objective is to evaluate clinical activity as measured by objective response rate (ORR) of PSMA / CD3-002 alone or in combination with cemiplimab according to modified Prostate Cancer Working Group 3 criteria. At selected sites, PSMA positron emission tomography / computed tomography scans will be performed at predefined time points on the study. Further details are provided below.

[0142] Purpose of the test The primary objectives of this study are to evaluate the safety, tolerability, and PK and to determine the RP2DR of PSMA / CD3-002 as monotherapy or in combination with cemiplimab (dose escalation), as well as to evaluate the preliminary antitumor activity of PSMA / CD3-002 as monotherapy or in combination with cemiplimab, as measured by objective response rate (ORR) per modified Prostate Cancer Working Group (PCWG3) criteria (dose expansion).

[0143] Secondary objectives of the study are: To evaluate the preliminary antitumor activity of PSMA / CD3-002 as monotherapy or in combination with cemiplimab as measured by ORR according to modified PCWG3 criteria (dose escalation), To characterize the safety profile in each expansion cohort (with expansion), To characterize the PK of PSMA / CD3-002 as monotherapy or in combination with cemiplimab (in dose expansion), To evaluate the preliminary antitumor activity of PSMA / CD3-002 as monotherapy or in combination with cemiplimab as measured by PSA decline (dose escalation and dose expansion), To evaluate the immunogenicity of PSMA / CD3-002 in module 1, and the immunogenicity of PSMA / CD3-002 and cemiplimab in module 2 (dose escalation and dose expansion).

[0144] The exploratory objectives of this study are to: To evaluate the preliminary antitumor activity of PSMA / CD3-002 as monotherapy or in combination with cemiplimab, as measured by percent change in PSA, disease control rate (DCR), duration of response (DOR), radiographic progression-free survival (rPFS), progression-free survival, overall survival (OS), time to response, and time to progression Evaluate exploratory molecular biomarkers to assess the impact of PSMA / CD3-002 alone or in combination with cemiplimab to understand the mechanism of action of PSMA / CD3-002 in patient populations, observed toxicities, disease / targets, and genomic factors underlying disease and response To characterize the relationship between serum cytokine levels and clinical tolerability of PSMA / CD3-002 monotherapy or in combination with cemiplimab To identify tumor and microenvironment features in diseased tissue that predict antitumor activity or are pharmacodynamically responsive to PSMA / CD3-002 therapy To identify characteristics of peripheral immune cell populations that predict antitumor activity or toxicity or that pharmacodynamically respond to PSMA / CD3-002 therapy To evaluate the effect of PSMA / CD3-002 alone or in combination with cemiplimab on PSMA-positive and fluorodeoxyglucose (FDG)-positive tumors as assessed by PET / CT. To assess the change from baseline in worst pain, mean pain and pain interference with daily activities scale of the Brief Pain Inventory-Short Form (BPI-SF) - Assess time to pain progression based on BPI-SF item 3, "Worst pain in the past 24 hours" To assess the effect of PSMA / CD3-002 alone or in combination with cemiplimab on patient-reported disease-specific symptoms, function and health-related quality of life measures (QLQ-C30, QLQ-PR25, PGIC, PGIS). To assess changes in opioid medication use in patient populations

[0145] Study design This is a Phase 1 / 2, first-in-human (FIH), open-label, multicenter study evaluating the safety, tolerability, efficacy, and PK of PSMA / CD3-002, an anti-PSMA x anti-CD3 bispecific antibody (bsAb), administered subcutaneously (Module 1) as monotherapy (SC) or in combination with intravenous (IV) cemiplimab (Module 2) in patients with treatment-experienced metastatic castration-resistant prostate cancer (mCRPC). Module 1 will be initiated first and Module 2 will be initiated after the lowest pharmacologically active dose level has been identified in Module 1.

[0146] The study has two parts: dose escalation and dose expansion. All patients in the study will be treated with two consecutive "step-up" doses (initial and transition doses) of PSMA / CD3-002 before reaching the target dose. The RP2DR, including the step-up dosing regimen and the target dose of PSMA / CD3-002 determined in dose escalation, will be further evaluated in dose expansion.

[0147] Dose escalation: Dose levels are defined by the target dose of PSMA / CD3-002. Five (or up to eight) potential dose levels are designed that escalate in ½-log increments around the target dose of PSMA / CD3-002. Dose escalations of <100% may be performed based on toxicity observed at any given dose level.

[0148] Module 1 - Determination of step-up dosing regimen and dose escalation of monotherapy PSMA / CD3-002: The initial dose of the step-up dosing regimen will begin at a dose of 0.03 mg SC. All three doses will be titrated in 1 / 2 log increments for each dose level until the occurrence of a specific adverse event (AE) leads to a change in dosing regimen (initial and transition doses) or the maximum tolerated dose (MTD) / RP2DR is defined (target dose). Administration of the target dose will begin on a weekly (QW) schedule and switch to once every 3 weeks (Q3W) after the lowest pharmacologically active dose is reached, as assessed by PSA or tumor response.

[0149] Module 2 - Dose Escalation of PSMA / CD3-002 in Combination with Cemiplimab: Patients enrolled in Module 2 will receive a 4-week PSMA / CD3-002 monotherapy lead-in cycle (Cycle 0, QW SC with step-up dose). During Module 2, PSMA / CD3-002 will be administered Q3W SC with Cemiplimab 350 mg IV (Cycle 1+). Dose escalation of PSMA / CD3-002 in Module 2 will begin at a dose level at least one dose level below the minimum pharmacologically active dose level of PSMA / CD3-002 determined in Module 1.

[0150] Assessment of dose-limiting toxicity during dose escalation: Dose-limiting toxicity (DLT) is any adverse event (AE) that may prevent progression to a higher dose level. DLT criteria incorporate AEs reported with other bsAbs and checkpoint inhibitors. Toxicity will be assessed according to NCI-CTCAE v5.0, with the exception of cytokine release syndrome (CRS), which will be assessed according to the current American Society for Transplantation and Cellular Therapy (ASTCT) criteria.

[0151] In both modules, dose level escalation (i.e., target dose escalation) follows BOIN (Bayesian Optimal Interval) design rules applied under the following conditions: 1) DLTs associated with previously untested doses of PSMA / CD3-002 are taken into account, 2) dose levels are escalated until an MTD with a toxicity rate of 30% is observed for the target dose of PSMA / CD3-002, and 3) the maximum number of patients treated at a dose level is 12.

[0152] In Module 1, because the step-up dosing regimen consists of doses that were tested and deemed tolerable as target doses in previous titration cohorts (after DL1 of Module 1), separate rules apply for modifying the step-up dosing regimen based on the occurrence and severity of cytokine release syndrome (CRS) and other DLTs.

[0153] DLT Observation Period: Module 1: The Module 1 DLT observation period (minimum duration of 28 days) begins upon the first dose of study drug. Monitoring for DLTs continues for at least 2 weeks after the first dose of PSMA / CD3-002 target dose at a given dose level. The maximum duration of the DLT period is 42 days, with allowance for a maximum 2-week dose delay during step-up dosing prior to the first dose of the target dose. DLTs observed during step-up dosing are considered separate from DLTs observed at the target dose and are considered modifications to the step-up dosing regimen. DLTs observed at the target dose will determine tolerability of the target dose and allow for dose level escalation. Module 2: The DLT observation period is defined as 21 days from the first dose of combination therapy (PSMA / CD3-002 and cemiplimab) starting on day 1 of cycle 1.

[0154] Dose Expansion: During dose expansion, patients will receive either monotherapy PSMA / CD3-002 (Module 1) or combination therapy with cemiplimab 350 mg IV Q3W (Module 2) in the assigned DL (e.g., RP2DR). If multiple DLs reveal pharmacodynamic activity and are well tolerated, up to two expansion cohorts in total may be open. In both dose escalation and dose expansion, safety assessments will be performed at each study drug administration visit. Radiographic response assessments will be performed every 9 weeks (Q9W) throughout the study. Investigators should continue treating patients with study drug until clinical or confirmed radiographic disease progression according to modified PCWG3, intolerable AEs, elective discontinuation for clinical response, withdrawal of consent, or other study discontinuation criteria are met. Thereafter, patients who do not withdraw consent will be asked to continue with treatment discontinuation follow-up procedures.

[0155] Test period All patients will undergo three consecutive study periods: screening, treatment, and follow-up. The screening period will be a maximum of 28 days. The treatment period will be divided into cycles to match the frequency of tumor assessments. During the treatment period, treatment cycles will generally be 9 weeks in both modules, with tumor assessments scheduled to occur at the beginning of each cycle. Module 2 will include two short cycles (cycles 0 and 1), which will be described in detail below. Treatment will continue until disease progression, intolerable AEs, elective discontinuation due to clinical response, withdrawal of consent, or any other study discontinuation criteria is met.

[0156] Module 1 - PSMA / CD3-002 Monotherapy: The treatment period for Module 1 consists of 9-week cycles. During Cycle 1, each patient receives at least two incremental "step-up" doses of PSMA / CD3-002 (i.e., an initial dose and a transition dose) before reaching the target dose. Administration of the first target dose of PSMA / CD3-002 may be delayed for up to 2 weeks to allow for resolution of CRS symptoms during the initial and / or transition doses.

[0157] The patient-level study scheme for Module 1 is shown in Figure 1 (QW) and Figure 2 (Q3W). As shown in Figures 1 and 2, during the first three doses of PSMA / CD3-002, patients will be observed in a monitored setting for at least 72 hours until systemic symptoms of CRS have resolved, or if CRS occurs. If Grade 2 or higher CRS is observed after any dose, patients should continue to be observed in a monitored setting for each subsequent dose until post-injection CRS is Grade 1 or lower, at which point subsequent treatment doses can be administered in an outpatient setting.

[0158] After the minimum pharmacologically active dose level is identified, the next dose level will be initiated on a Q3W schedule of the target dose of PSMA / CD3-002 for patients subsequently enrolled. The initial, transition, and first two consecutive target dose intervals will remain QW for all patients enrolled in the study according to Figure 2. All doses will be administered SC.

[0159] For patients enrolled after establishment of Q3W dosing and who require an extended step-up dosing period for resolution of CRS symptoms before receiving the first target dose, Cycle 1 may be extended to maintain the Q3W dosing schedule.

[0160] The dose escalation and alternative schemes for Module 1 are shown in Tables 8A and 8B below. [Table 8-1] [Table 8-2]

[0161] Module 2 - Combination Therapy with PSMA / CD3-002 and Cemiplimab: The treatment period for patients enrolled in Module 2 begins with a PSMA / CD3-002 monotherapy lead-in cycle (Cycle 0) including weekly step-up dosing. Due to the potential for augmentation of CRS with combination therapy, patients must tolerate the target dose of PSMA / CD3-002 without CRS during the monotherapy lead-in before initiating combination with cemiplimab.

[0162] Dosing is QW during cycle 0, transitioning to Q3W in cycle 1. Cycle 0 consists of weekly monotherapy dosing as the initial dose, transition dose, and two target doses of PSMA / CD3-002. The planned length of cycle 0 is 4 weeks, but may be extended up to 6 weeks to allow clearance of CRS from the initial and transition doses, or to repeat the target dose to demonstrate tolerability without CRS symptoms. Cycle 1 is 6 weeks (42 days) to accommodate timing of initial on-treatment tumor assessment when PSMA / CD3-002 and cemiplimab combination therapy is initiated. Subsequent cycles (cycles 2 and above) are 9 weeks (63 days). The patient-level study scheme for module 2 is shown in Figure 3.

[0163] In module 2, the target dose of PSMA / CD3-002 will not exceed the target dose of PSMA / CD3-002 deemed tolerable in module 1. All PSMA / CD3-002 doses will be administered SC and cemiplimab will be administered IV. If grade 2 or higher CRS is observed at the same dose in module 1, the patient will be observed in a monitored setting for the first three injections of cycle 0 (Figure 5). All patients will be observed in a monitored setting for the first combination therapy in cycle 1 for at least 72 hours or until all symptoms of CRS have resolved. Additionally, if grade 2 or higher CRS is observed at the first dose, the patient must continue to receive treatment in a monitored setting for each subsequent dose until post-injection CRS is grade 1 or lower, at which point subsequent treatments can be administered as outpatients. [Table 9-1] [Table 9-2]

[0164] Study population Approximately 199 patients will be enrolled in the study as follows: anticipated enrollment is approximately 91 patients in the dose escalation phase (43 patients in module 1 and 48 patients in module 2) and approximately 108 patients in the dose expansion phase. Sample size estimates are based on up to two expansion cohorts for each module with a maximum of 27 patients per cohort.

[0165] The study population includes men with treatment-experienced mCRPC. To be included in the study, patients must have received at least two approved therapies for metastatic and / or castration-resistant disease, including second-generation antiandrogen therapy (e.g., abiraterone, enzalutamide, apalutamide, or darolutamide).

[0166] Inclusion Criteria: Patients must meet the following criteria to be eligible for enrollment in this study: 1. Male ≥ 18 years old 2. Histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma 3. Metastatic castration-resistant prostate cancer (mCRPC) with PSA ≥ 4ng / ml at screening and progression within 6 months prior to screening: a. PSA progression defined as a confirmed increase in PSA level with an interval of ≥ 1 week between assessments. b. Soft tissue radiological disease progression based on RECIST version 1.1 criteria, with or without PSA progression Bone radiological disease progression defined as the appearance of 2 or more new bone lesions on a bone scan with or without PSA progression. Note: Measurable lesions by RECIST version 1.1 by local read at screening are not an eligibility criterion for enrollment. 4. Have progressed on or are intolerant to 2 or more lines of prior approved systemic therapy (in addition to androgen deprivation therapy [ADT]) in the metastatic and / or castration-resistant setting, including at least one second-generation antiandrogen therapy (e.g., abiraterone, enzalutamide, apalutamide, or darolutamide). NOTE: Non-taxane-based chemotherapy regimens given for metastatic prostate cancer with mixed histology are acceptable and will be included when evaluating treatment options. 5. Able and willing to provide archival or freshly obtained tumor tissue. Note: For dose escalation only, if archival or fresh tissue is not available, a pathology report confirming the diagnosis of prostate cancer may be provided. 6. Has had an orchiectomy or is receiving luteinizing hormone-releasing hormone (LHRH) agonist therapy or antagonist therapy with a serum testosterone level <50 ng / dL and agrees to continue LHRH agonist or antagonist therapy during the study. 7. ECOG performance status of 0 or 1 8. Have adequate organ and bone marrow function documented by: Hemoglobin ≥ 8.5g / dL b. Absolute neutrophil count ≥ 1.0 × 109 / L c. Platelet count ≥100×109 / L 9. Serum creatinine ≤ 1.5x ULN or estimated glomerular filtration rate. A 24-hour urinary creatinine collection may substituted calculated creatinine clearance to meet eligibility criteria. 10. Proper Liver Function: (1) Total bilirubin level must be 1.5 times the ULN or less. For patients with known Gilbert syndrome, a level of 3 times the institutional ULN or less is acceptable. (2) AST ≤ 2.5 × ULN (3) AST ≤ 2.5 × ULN (4) AST ≤ 2.5 × ULN 11. Willing and able to comply with all procedures and requirements related to clinical and study procedures. 12. Be willing and able to provide informed consent as required by health authority and medical institution guidelines. 13. Understand and complete study-related questionnaires

[0167] Exclusion Criteria: Patients who meet any of the following criteria will be excluded from the study: 1. Currently receiving treatment in another study 2. Participation in a study of an investigational drug or device within 4 weeks of first dose of study treatment 3. Have received treatment with approved systemic therapy (including Sipulcel-T) within 3 weeks of dosing or have not yet recovered from any acute toxicity (i.e., Grade 1 or lower or baseline) as described in the inclusion criteria and with the exception of laboratory changes as described below: Patients with neuropathy of grade 2 or less 4. Have undergone radiation therapy or major surgery within 14 days of first dose of study drug or have not recovered from an AE (i.e., grade ≤1 or baseline), except for the inclusion criteria and laboratory changes listed below: Patients with neuropathy of grade 2 or less 5. Have received any prior systemic biologic therapy within 5 half-lives of the first dose of study treatment. Note: Patients previously treated with cetuximab, rituximab, or other non-immunomodulatory antibodies with half-lives longer than 7 days will be allowed, after discussion with the sponsor, if at least 30 days have elapsed since their last treatment. 6. Previously received PSMA-targeted therapy 7. Dose Escalation and Module 1 Dose Expansion: Previous anti-cancer immunotherapy (other than Sipulcel-T) within 5 half-lives prior to study treatment. Examples of immunomodulatory agents include CTLA-4, 4-1BB (CD137), or OX-40 blockers, therapeutic vaccines, anti-PD-1 / PD-L1, phosphoinositide 3-kinase (PI3K) delta inhibitors, or cytokine anti-cancer therapies. Note: Patients who have previously received study cell-based therapy (e.g., CAR-T cells) will be excluded. 8. Module 2 Dose Expansion: Previous anti-cancer immunotherapy. Examples of immunomodulatory agents include blockers of CTLA-4, 4-1BB (CD137), or OX-40, therapeutic vaccines, anti-PD-1 / PD-L1, PI3Kdelta inhibitors, CAR-T cells, or cytokine anti-cancer treatments. Note: Prior treatment with Sipulcel-T is permitted. 9. Patients who have not recovered from immune-mediated AEs (i.e., Grade ≤1 or baseline) within 3 months prior to study medication, except for endocrinopathy adequately controlled with hormone replacement 10. Patients who have permanently discontinued anticancer immunomodulatory therapy due to immune-related AEs 11. Have a disease that requires or continues to require corticosteroid therapy (≥ 10 mg / day prednisone or equivalent anti-inflammatory) within 1 week prior to first dose of study drug. Physiological replacement doses are permitted even if they are > 10 mg prednisone / day or equivalent, as long as they are not administered for immunosuppressive purposes. Inhaled or topical steroids are permitted, provided they are not intended to treat an autoimmune disorder. Note: Patients who require short-term steroids (maximum 2 days in the week prior to enrollment) or physiological replacement may be enrolled in the study. 12. Current or recent (within 5 years) evidence of significant autoimmune disease requiring systemic immunosuppressive treatment. The following are not excluded: vitiligo, resolved childhood asthma, endocrine disorders requiring hormone replacement only (e.g. hypothyroidism, type 1 diabetes mellitus), or psoriasis not requiring systemic treatment. 13. Liver metastasis 14. Has another malignancy that is ongoing or requires active treatment, except: Non-melanoma skin cancer that has received potentially curative therapy b. Any tumor deemed to be effectively treated with definitive local control (with or without continuation of adjuvant hormonal therapy) 15. Dose escalation: History of CNS metastases, including previously treated metastases Dose Expansion: Untreated or active primary brain tumors, CNS metastases, leptomeningeal disease, or spinal cord compression Exception: Patients with previously treated CNS metastases or spinal cord compression may participate as long as: a. No evidence of progression for at least 6 weeks prior to first dose of study drug, and neurological symptoms have returned to baseline b. No evidence of new or spreading central nervous system metastases c. No need for systemic corticosteroids to manage central nervous system metastases or spinal cord compression within 2 weeks prior to first dose of study drug 16. Has had encephalitis, meningitis, neurodegenerative disease (excluding mild dementia not interfering with activities of daily living [ADL]), or uncontrolled seizures within 1 year prior to the first dose of study treatment. 17. Known history or any evidence of interstitial lung disease or active non-infectious pneumonia within 5 years prior to first dose of study drug. History of radiation pneumonitis in the radiation field is permitted. 18. Has uncontrolled infection with the human immunodeficiency virus, hepatitis B or hepatitis C infection, or has been diagnosed with an immunodeficiency a. Patients will be tested for Hepatitis C Virus (HCV) and Hepatitis B Virus (HBV) at screening. b. Patients with known HIV infection and whose infection is controlled (undetectable viral load (HIV RNA PCR), CD4 count ≥ 350, and self-resolved or on stable antiviral therapy) are permitted. Patients with controlled HIV infection should be monitored according to local standards. c. Patients with Hepatitis B who have a controlled infection (HBsAg+) (serum Hepatitis B virus DNA PCR below the limit of detection and receiving antiviral therapy for Hepatitis B) will be accepted. Patients with controlled infection must undergo regular monitoring for HBV DNA. Patients must continue to receive antiviral therapy for at least 6 months after the last dose of study drug. d. Patients who are hepatitis C virus antibody positive (HCV Ab+) and have controlled infection (undetectable HCV RNA by PCR, either naturally occurring or responding adequately to a course of anti-HCV therapy) can be enrolled in the study. 19. Have an infection requiring hospitalization or intravenous anti-infective therapy within 2 weeks of the first dose of study drug 20. Received a live vaccine within 28 days of starting study drug 21. Previous allogeneic stem cell transplant, or organ transplant at any time, or autologous stem cell transplant within 12 weeks prior to starting study drug 22. Known allergy or hypersensitivity to any component of the study drug. 23. Has a known psychiatric or substance abuse disorder that would prevent participation in this study. 24. Any medical condition, comorbidity, physical examination findings, or metabolic dysfunction or laboratory abnormalities that, in the opinion of the Investigator, render the patient unsuitable to participate in the clinical study because of a high safety risk and / or which may affect the interpretation of the results of the study, including, but not limited to, significant cardiovascular disease (e.g., New York Heart Association class III or IV heart disease, myocardial infarction within the past 6 months, unstable arrhythmia or unstable angina pectoris) and / or significant pulmonary disease (e.g., history of obstructive pulmonary disease and symptomatic bronchospasm). 25. Cardiac ejection fraction <40% by echocardiogram or multi-gated acquisition scan (MUGA)

[0168] Study treatment PSMA / CD3-002 will be administered at doses of 0.3 mg to 30 mg (but can be up to 900 mg) either QW or Q3W with SC dosing as the target dose levels. Cemiplimab will be administered at a dose of 350 mg Q3W as an intravenous infusion over 30 minutes.

[0169] If both agents are administered on the same day, PSMA / CD3-002 should be administered first and cemiplimab should be administered within 30 minutes of completion of PSMA / CD3-002 administration.

[0170] All enrolled patients starting on C1D1 will require routine premedication with steroids, as detailed below: · Dexamethasone 10 mg IV / PO on the day and day after administration of up to 2nd full dose (e.g., C1D22) · Begin tapering after the second full dose 10 mg IV / PO for the third total dose (e.g., C1D29) 6 mg IV / PO for the 4th total dose (e.g., C1D36)

[0171] Study Evaluation Items The primary endpoints of the study were: dose-limiting toxicities, other treatment-emergent adverse events (including TEAEs, irAEs), serious AEs (SAEs), adverse events of special interest (AESIs), and laboratory abnormalities (dose escalation); serum PSMA / CD3-002 concentrations as monotherapy or in combination with cemiplimab (dose escalation), and objective response rate (ORR) according to modified Prostate Cancer Working Group 3 (PCWG3) criteria (dose expansion), defined as the proportion of patients achieving a response based on: - A ≥ 50% decline in PSA from baseline confirmed by a second PSA test ≥ 4 weeks later, and / or - Confirmed radiographic response of complete response (CR) or partial response (PR) Key secondary endpoints include: ORR by modified PCWG3 criteria (dose escalation), defined as the proportion of patients achieving a response based on a ≥ 50% reduction in PSA from baseline, confirmed by a second PSA test after ≥ 4 weeks, and / or a confirmed radiographic response of complete response (CR) or partial response (PR); dose-limiting toxicities, other TEARs (including irAEs), SAEs, AESIs and laboratory abnormalities (expansion); serum PSMA / CD3-002 concentrations as monotherapy or in combination with cemiplimab (dose escalation); proportion of patients achieving a ≥ 50% reduction in PSA from baseline, confirmed by a second PSA test after ≥ 4 weeks (dose escalation and expansion); proportion of patients achieving a ≥ 90% reduction in PSA from baseline, confirmed by a second PSA test after ≥ 4 weeks (dose escalation and expansion); immunogenicity and Measured by anti-drug antibodies (ADA) to PSMA / CD3-002 in module 1, and ADA to PSMA / CD3-002 and cemiplimab in module 2 (dose escalation and expansion).

[0172] Exploratory endpoints were: Percent change in PSA Disease control rate (DCR) (via modified PCWG3 and iRECIST) Duration of response (DOR) based on radiographic response (rDOR) (via modified PCWG3 and iRECIST) DOR based on PSA response Radiological progression-free survival (rPFS) (via modified PCWG3 and iRECIST) PSA progression-free survival · Overall survival (OS) Time to response based on radiographic response (via modified PCWG3 and iRECIST) Time to response based on PSA response Time to progression based on x-ray progression Time to progression based on PSA progression Abundance and distribution of therapeutic targets (e.g., PD-1 / PD-L1, PSMA, and CD3+ T cells) in tumor tissue samples at baseline and over time during therapy Correlation of CTC abundance and molecular characteristics with clinical efficacy Tumor mutation profiling of baseline and on-treatment ctDNA, CTCs, and / or tumor tissue, including assessment of individual somatic variants, tumor mutation burden (TMB), alterations in DNA repair pathway genes, and the relationship between these features and drug response Baseline and treatment abundance and phenotype of circulating T-cell subsets and their association with pharmacodynamic responses and clinical efficacy or toxicity · Concentrations of systemic inflammatory markers (serum cytokines, etc.), immune activity, and clinical toxicity Change from baseline in tumor PSMA and FDG PET signals after initiation of therapy Association between baseline PSMA PET tumor positivity and clinical activity Time to pain progression (TTPP) assessed by Brief Pain Inventory-Short Form (BPI-SF) item 3 ("worst pain in 24 hours") and lactate analgesic use Change from baseline in pain severity and pain interference as measured by the BPI-SF Change from baseline in GHS / QoL as measured by the EORTC QLQ-C30 GHS / QoL scale score Change from baseline in physical function as measured by the EORTC QLQ-C30 physical function score Change from baseline in urinary symptoms as measured by the EORTC QLQ-PR25 urinary symptoms scale score

[0173] Results: Administration of PSMA / CD3-002 and cemiplimab in patients with prostate cancer is expected to result in complete or partial responses with durable disease control.

[0174] The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are intended to be within the scope of the appended claims. [Table 10] *******

Claims

1. 1. A method of treating a PSMA-expressing cancer in a subject in need thereof, comprising administering to the subject a bispecific antibody comprising a first antigen-binding domain that specifically binds to prostate-specific membrane antigen (PSMA) on a target tumor cell and a second antigen-binding domain that specifically binds to human CD3 on a T cell, wherein the bispecific antibody is administered to the subject at a dose of at least 0.03 mg.

2. The method of claim 1 , wherein the PSMA-expressing cancer is prostate cancer.

3. The method of claim 1 or 2, wherein the PSMA-expressing cancer is metastatic prostate cancer.

4. The method of any one of claims 1 to 3, wherein the PSMA-expressing cancer is castration-resistant prostate cancer.

5. The method of any one of claims 1 to 4, wherein the subject has undergone at least two prior treatments for metastatic and / or castration-resistant prostate cancer.

6. The method of claim 5, wherein the subject is receiving at least one anti-androgen therapy.

7. 7. The method of claim 6, wherein the antiandrogen therapy is selected from abiraterone, enzalutamide, apalutamide, or darolutamide.

8. The method of any one of claims 1 to 7, wherein the subject has histologically or cytologically confirmed adenocarcinoma of the prostate that does not have pure small cell carcinoma.

9. 9. The method of any one of claims 1 to 8, wherein the subject has metastatic castration-resistant prostate cancer with a prostate-specific antigen (PSA) value of > 4 ng / ml prior to treatment with the bispecific antibody.

10. 10. The method of claim 9, wherein the subject's cancer has progressed within 6 months prior to treatment with the bispecific antibody, and cancer progression is determined by (a) a rising PSA level noted with an interval of ≧1 week between assessments, (b) progression of soft tissue radiological disease with or without a rising PSA, and / or (c) progression of bone radiological disease with the appearance of two or more bone lesions on a bone scan with or without a rising PSA.

11. The method of any one of claims 1 to 10, wherein the subject has undergone an orchiectomy.

12. 11. The method of any one of claims 1 to 10, wherein the subject is undergoing luteinizing hormone releasing hormone (LHRH) agonist or antagonist therapy and has a serum testosterone level of <50 ng / ml prior to treatment with the bispecific antibody.

13. The first antigen-binding domain comprises: (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) contained within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:1; and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) contained within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:

2.

14. The method of claim 13, wherein the first antigen-binding domain comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO:5, an HCDR2 comprising the amino acid sequence of SEQ ID NO:6, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:

7.

15. The method of claim 13 or 14, wherein the first antigen-binding domain comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO: 8, an LCDR2 comprising the amino acid sequence of SEQ ID NO: 9, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:

10.

16. The method of any one of claims 13 to 15, wherein the first antigen-binding domain comprises an HCVR comprising the amino acid sequence of SEQ ID NO:1, and an LCVR comprising the amino acid sequence of SEQ ID NO:

2.

17. The second antigen-binding domain comprises: (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) contained within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:4; and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) contained within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:

2.

18. 18. The method of claim 17, wherein the second antigen-binding domain comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO: 14, an HCDR2 comprising the amino acid sequence of SEQ ID NO: 15, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:

16.

19. The method of claim 17 or 18, wherein the second antigen-binding domain comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO: 8, an LCDR2 comprising the amino acid sequence of SEQ ID NO: 9, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:

10.

20. The method of any one of claims 17 to 19, wherein the second antigen-binding domain comprises an HCVR comprising the amino acid sequence of SEQ ID NO:4 and an LCVR comprising the amino acid sequence of SEQ ID NO:

2.

21. The second antigen-binding domain comprises: (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) contained within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:3; and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) contained within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:

2.

22. 22. The method of claim 21 , wherein the second antigen-binding domain comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO: 11, an HCDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:

13.

23. The method of claim 21 or 22, wherein the second antigen-binding domain comprises an LCDR1 comprising the amino acid sequence of SEQ ID NO: 8, an LCDR2 comprising the amino acid sequence of SEQ ID NO: 9, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:

10.

24. The method of any one of claims 21 to 23, wherein the second antigen-binding domain comprises an HCVR comprising the amino acid sequence of SEQ ID NO:3, and an LCVR comprising the amino acid sequence of SEQ ID NO:

2.

25. The method of any one of claims 1 to 24, wherein the bispecific antibody comprises a human IgG heavy chain constant region.

26. 26. The method of claim 25, wherein the human IgG heavy chain constant region is of isotype IgG1.

27. 26. The method of claim 25, wherein the human IgG heavy chain constant region is of isotype IgG4.

28. 28. The method of claim 26 or 27, wherein the bispecific antibody comprises a chimeric hinge that reduces Fcγ receptor binding compared to a wild-type hinge of the same isotype.

29. 29. The method of any one of claims 25 to 28, wherein the first heavy chain or the second heavy chain, but not both, comprises a CH3 domain that comprises an H435R (EU numbering) modification and an Y436F (EU numbering) modification.

30. The method of any one of claims 1 to 24, wherein the bispecific antibody comprises a first heavy chain comprising the amino acid sequence of SEQ ID NO:

17.

31. The method of any one of claims 1 to 24, wherein the bispecific antibody comprises a second heavy chain comprising the amino acid sequence of SEQ ID NO:

20.

32. The method of any one of claims 1 to 24, wherein the bispecific antibody comprises a second heavy chain comprising the amino acid sequence of SEQ ID NO:

19.

33. 25. The method of any one of claims 1 to 24, wherein the bispecific antibody comprises a first heavy chain comprising the amino acid sequence of SEQ ID NO: 17, a second heavy chain comprising the amino acid sequence of SEQ ID NO: 20, and a common light chain comprising the amino acid sequence of SEQ ID NO:

18.

34. 25. The method of any one of claims 1 to 24, wherein the bispecific antibody comprises a first heavy chain comprising the amino acid sequence of SEQ ID NO: 17, a second heavy chain comprising the amino acid sequence of SEQ ID NO: 19, and a common light chain comprising the amino acid sequence of SEQ ID NO:

18.

35. 35. The method of any one of claims 1 to 34, further comprising administering a second therapeutic agent or treatment regimen.

36. 36. The method of claim 35, wherein the second therapeutic agent or therapeutic regimen comprises an anti-PD-1 antibody or an antigen-binding fragment thereof.

37. the anti-PD-1 antibody or antigen-binding fragment thereof (a) three heavy chain complementarity determining regions (HCDR1, HCDR2, and HCDR3) contained within a heavy chain variable region (HCVR) comprising the amino acid sequence of SEQ ID NO:21; and (b) three light chain complementarity determining regions (LCDR1, LCDR2, and LCDR3) contained within a light chain variable region (LCVR) comprising the amino acid sequence of SEQ ID NO:

22.

38. 38. The method of claim 37, wherein the anti-PD-1 antibody or antigen-binding fragment comprises an HCDR1 comprising the amino acid sequence of SEQ ID NO:23, an HCDR2 comprising the amino acid sequence of SEQ ID NO:24, and an HCDR3 comprising the amino acid sequence of SEQ ID NO:

25.

39. The method of claim 37 or 38, wherein the anti-PD-1 antibodies and antigen-binding fragments comprise an LCDR1 comprising the amino acid sequence of SEQ ID NO:26, an LCDR2 comprising the amino acid sequence of SEQ ID NO:27, and an LCDR3 comprising the amino acid sequence of SEQ ID NO:

28.

40. 40. The method of any one of claims 37-39, wherein the anti-PD-1 antibody or antigen-binding fragment comprises an HCVR comprising the amino acid sequence of SEQ ID NO:21, and an LCVR comprising the amino acid sequence of SEQ ID NO:

22.

41. 41. The method of claim 40, wherein the anti-PD-1 antibodies and antigen-binding fragments are anti-PD-1 antibodies comprising a heavy chain comprising the amino acid sequence of SEQ ID NO:29 and a light chain comprising the amino acid sequence of SEQ ID NO:

30.

42. 42. The method of any one of claims 1 to 41, wherein the bispecific antibody is administered to the subject once a week at a dose of 0.01 mg to 1000 mg.

43. 43. The method of claim 42, wherein the bispecific antibody is administered to the subject once a week at a dosage of 0.03 mg to 30 mg.

44. 43. The method of claim 42, wherein the bispecific antibody is administered to the subject once a week at a dose of 3 mg to 900 mg.

45. 42. The method of any one of claims 1 to 41, wherein the bispecific antibody is administered to the subject at a dose of 0.01 mg to 1000 mg once every three weeks.

46. 46. ​​The method of claim 45, wherein the bispecific antibody is administered to the subject at a dosage of 0.03 mg to 30 mg once every three weeks.

47. 46. ​​The method of claim 45, wherein the bispecific antibody is administered to the subject at a dose of 3 mg to 900 mg once every three weeks.

48. 48. The method of any one of claims 36-47, wherein the anti-PD-1 antibody is administered to the subject at a dose of 300 mg to 400 mg once every three weeks.

49. 49. The method of claim 48, wherein the anti-PD-1 antibody is administered to the subject at a dose of 350 mg once every three weeks.

50. 50. The method of any one of claims 1 to 49, wherein the subject has stable disease, a partial response, or a complete response after administration of the bispecific antibody for at least one week at a dose of 0.03 to 900 mg.

51. The method of any one of claims 1 to 50, wherein the subject undergoes x-ray imaging after administration of one or more doses of the bispecific antibody.

52. 52. The method of claim 51, wherein the x-ray imaging comprises a Fluorine F18 DCFPyL PET / CT scan.

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