87562761MMY1001

Adult RRMM with measurable disease; prior PI + IMiD + anti-CD38; ECOG 0–1; adequate renal/hepatic/hematologic function;

5.1. Inclusion Criteria Each potential participant must satisfy all of the following criteria to be enrolled in the study: Age 1. Be ≥18 years of age (or the legal age of majority in the jurisdiction in which the study is taking place, whichever is greater) at the time of informed consent. Disease Characteristics 2. Relapsed, refractory multiple myeloma with measurable disease defined as: Serum monoclonal paraprotein (M-protein) level >0.5g/dL; or Urine M-protein level >200mg/24 hours; or Light chain multiple myeloma: serum immunoglobulin free light chain (FLC) >10 mg/dL and abnormal serum immunoglobulin kappa-lambda FLC ratio. Prior Therapy Requirements 3. Must have had prior therapy including a proteasome inhibitor, immunomodulatory agent and anti-CD38 therapy. Performance Status 4. Have an ECOG performance status of 0 to 1 (Section8.3.5 and Appendix10). Renal Function 5. Have an eGFR, of >30mL/min/1.73m2 computed with the online calculator on the CKD-EPI website (http://ckdepi.org/equations/gfr-calculator/) by use of the CKD-EPIcr result. Hepatic Function 6. AST ≤3 x ULN ALT ≤3 x ULN Total bilirubin ≤1.5 x ULN For bilirubin in cases of known congenital nonhemolytic hyperbilirubinemias such as Gilbert’s Syndrome: Isolated total bilirubin ≥1.5 x ULN with conjugated [direct] bilirubin≤1.5 x ULN Hematologic Values 7. Participants should have: Hemoglobin ≥8g/dL (≥5 mmol/L) (without prior red blood cell [RBC] transfusion within 7 days before the laboratory test; recombinant human erythropoietin use is permitted) Absolute neutrophil count ≥1×109/L (without use of granulocyte colony stimulating factor (G-CSF) within 7 days prior to the date of the test) Platelets ≥50×109/L (without transfusion support in the 7 days prior to the laboratory test) Sex and Contraceptive/Barrier Requirements 8. While on study treatment and for 6months after the last dose of study treatment, a participant must: Not breastfeed or be pregnant. Not donate gametes (ie, eggs or sperm) or freeze for future use for the purposes of assisted reproduction. Wear an external condom. If of childbearing potential, o have a negative highly sensitive (eg, β-hCG) pregnancy test at screening and within 24 hours before the first dose of study treatment, and agree to further pregnancy tests, o practice at least 1 highly effective method of contraception; if oral contraceptives are used, a barrier method of contraception must also be used. If a participant’s partner is of childbearing potential, o the partner must practice a highly effective method of contraception unless the participant is vasectomized. See Appendix4: Contraceptive and Barrier Guidance for details. Informed Consent 9. Must sign an ICF indicating that the participant understands the purpose of, and procedures required for, the study and is willing to participate in the study. 10. Be willing and able to adhere to the lifestyle restrictions specified in this protocol.

Exclude PCL/WM/POEMS/AL amyloid; unresolved prior toxicity; known GPRC5D loss; uncontrolled infection/autoimmune/psychiatric/CV disease; CNS MM; recent SCT or prohibited prior therapy windows; uncontrolled HIV/HBV/HCV; live vaccine within 4 weeks.

5.2. Exclusion Criteria Any potential participant who meets any of the following criteria will be excluded from participating in the study: Medical Conditions 1. Active plasma cell leukemia (>2×109/L plasma cells by standard differential), Waldenström’s macroglobulinemia, POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes), or immunoglobulin light chain amyloidosis. 2. Non-hematologic toxicity from prior anticancer therapy that has not resolved to baseline level or to ≤Grade 1 (except alopecia, tissue post-RT fibrosis, or Grade <3 peripheral neuropathy). Participants must have resolution of AEs related to prior GPRC5D therapies (if applicable). 3. Known loss of expression of GPRC5D antigen. 4. Known allergies, hypersensitivity, or intolerance to excipients of JNJ-87562761 (refer to the IB). 5. Pulmonary compromise requiring supplemental oxygen used to maintain adequate oxygenation. 6. Had major surgery or had significant traumatic injury within 2 weeks. Note: Participants with planned surgical procedures to be conducted under local anesthesia may participate. 7. Evidence of serious, uncontrolled, ongoing viral, bacterial, or systemic fungal infection requiring antiviral, antibacterial, or antifungal treatment. 8. Active autoimmune disease requiring systemic immunosuppressive therapy within 6 months before start of study treatment. Note: Exception for participants with vitiligo, type 1 diabetes, and prior autoimmune thyroiditis that are currently euthyroid based on clinical symptoms and laboratory testing are eligible regardless of when these conditions were diagnosed. 9. Current disabling psychiatric conditions, active substance abuse (eg, alcohol or drug abuse), severe dementia, or altered mental status. Cardiovascular Dysfunction 10. Any of the following within 6 months prior to first dose of study treatment: severe or unstable angina, myocardial infarction, major thromboembolic events (eg, pulmonary embolism, cerebrovascular accident), clinically significant ventricular arrhythmias or heart failure New York Heart Association functional classification Class III to IV. Uncomplicated deep vein thrombosis is not considered exclusionary. Disease Characteristics 11. Stem cell transplantation: a) Allogeneic stem cell transplant within 6 months. Participants who received an allogeneic transplant must be off all immunosuppressive medications for ≥42days without signs of graft-versus-host disease. b) Received an autologous stem cell transplant ≤12weeks. Prior Malignancies 12. Can have a prior or concurrent second malignancy (other than the disease under study) whose natural history or treatment is unlikely to interfere with any study endpoints of safety or the efficacy of the study treatment(s) (see Appendix9 on Allowed Recent Second or Prior Malignancies for details). Brain and Central Nervous System Metastases 13. Central nervous system involvement or clinical signs of meningeal involvement of multiple myeloma. If either is suspected, whole brain MRI and lumbar cytology are required during screening. HIV Status 14. Human immunodeficiency virus-positive participants are not eligible if they meet any of the following: a. Detectable viral load (ie, ≥50 copies/mL) at screening b. CD4+ count ≤300cells/mm3 at screening c. Acquired immunodeficiency syndrome (AIDS)-defining opportunistic infection within 6 months of screening d. Not receiving highly active antiretroviral therapy (HAART). Any changes in HAART due to resistance/progression should occur at least 3 months prior to screening. A change in HAART due to toxicity is allowed up to 4 weeks prior to screening. Note: HAART that could interfere with study treatment is excluded (consult the sponsor for a review of medications prior to enrollment). Viral Hepatitis Assessments 15. Active hepatitis of infectious origin. a) Seropositive for hepatitis B: defined by a positive test for hepatitis B surface antigen [HBsAg]. Participants with resolved infection (ie, participants who are HBsAg negative with positive antibodies to total hepatitis B core antigen [anti-HBc]) must be screened using real-time polymerase chain reaction (RT-PCR) measurement of hepatitis B virus (HBV) DNA levels. Those who are RT-PCR positive will be excluded. Participants with serologic findings suggestive of HBV vaccination (anti-HBs positivity as the only serologic marker) AND a known history of prior HBV vaccination, do not need to be tested for HBV DNA by RT-PCR. (see Appendix11, Hepatitis B Virus Screening) b) Known hepatitis C infection or positive serologic testing for hepatitis C virus (anti-HCV) antibody. Participants with positive hepatitis C antibody due to prior resolved disease can be enrolled only if a confirmatory negative hepatitis C RNA test is obtained at screening or within 3 months prior to first dose of study treatment. c) Other clinically active liver disease of infectious origin. Prior/Concomitant Therapy 16. Prior antitumor therapy as follows, in the specified time frame prior to the first dose of study treatment: a) Targeted therapy, epigenetic therapy, monoclonal antibody treatment, or treatment with an investigational drug or an invasive investigational medical device within 21 days or at least 5 half-lives, whichever is less. b) Gene-modified adoptive cell therapy (eg, CAR-modified T cells, CAR-modified natural killer cells, iNK cells) within 3 months. c) Treatment with anti-CD38 directed therapies within 3 months. d) Prior exposure to GPRC5D targeting agents, if not within 3 months, may be allowed after discussion with the sponsor. e) Conventional chemotherapy within 21 days. f) Proteasome inhibitor therapy within 14 days. g) Immunomodulatory agent therapy within 7 days. h) Radiotherapy within 14 days. However, if palliative focal radiation was used, the participant is eligible irrespective of the end date of radiotherapy. 17. A cumulative dose of corticosteroids equivalent to ≥140mg of prednisone within the 14-day period before the first dose of study treatment. 18. Receiving any disallowed therapies as noted in Section6.9, Concomitant Therapy before the planned first dose of study treatment. 19. Has received or plans to receive any live, attenuated vaccine within 4weeks before the first dose of study treatment. Other Exclusions 20. Any condition for which, in the opinion of the investigator or sponsor, participation would not be in the best interest of the participant (eg, compromise the well-being) or that could prevent, limit, or confound the protocol-specified assessments.