AN OPEN-LABEL, 3-ARM, MULTICENTER, RANDOMIZED PHASE 3 STUDY TO EVALUATE THE EFFICACY AND SAFETY OF PF-06863135 MONOTHERAPY AND PF-06863135 + POMALIDOMIDE VERSUS CONTROL (ISATUXIMAB + POMALIDOMIDE + DEXAMETHASONE) IN PARTICIPANTS WITH MULTIPLE MYELOMA WHO HAVE RECEIVED AT LEAST 1 PRIOR LINE OF THERAPY INCLUDING LENALIDOMIDE AND A PI.

1. Participants age ≥18 years (or the minimum country-specific age of consent if > 18). 2. Prior diagnosis of MM as defined according to IMWG criteria.1 3. Measurable disease based on IMWG criteria as defined by at least 1 of the following: a. Serum M-protein ≥0.5 g/dL by SPEP; b. Urinary M-protein excretion ≥200 mg/24 hours by UPEP; c. Serum immunoglobulin FLC ≥10 mg/dL (≥100 mg/L) AND abnormal serum immunoglobulin kappa to lambda FLC ratio (< 0.26 or > 1.65). 4. Prior anti-MM therapy: a. Part 1: At least 3 prior lines of anti-MM therapy including treatment with lenalidomide and a PI. b. Part 2: At least 2 prior lines of anti-MM therapy including treatment with lenalidomide and a PI. (NOTE - The protocol will be amended prior to start of Part 2. The inclusion criteria for prior therapy will be changed to ‘At least 1 prior line of anti-MM therapy including treatment with lenalidomide and a PI.') 5. ECOG performance status < 1. 6. LVEF ≥40% as determined by a MUGA scan or ECHO. 7. Adequate hepatic function characterised by the following: a. Total bilirubin ≤1.5 x ULN; b. AST ≤2.5 x ULN and ALT ≤2.5 x ULN.8. Estimated creatinine clearance ≥30 mL/min (according to the Cockcroft Gault formula, by 24-hour urine collection for creatinine clearance, or per the local institutional standard method). 9. Adequate BM function characterised by the following: a. ANC ≥1.0 × 109^9/L (use of granulocyte-colony stimulating factors is permitted if completed at least 28 days prior to planned start of dosing); b. Platelet count ≥75,000/µL if < 50% of BM nucleated cells are plasma cells, or ≥ 50,000/µL if ≥50% of BM nucleated cells are plasma cells (transfusion support is permitted if completed at least 28 days prior to planned start of dosing); and c. Hemoglobin ≥8 g/dL (transfusion support is permitted if completed at least 28 days prior to planned start of dosing) 10. Corrected serum calcium ≤14 mg/dL (≤3.5 mmol/L), or free ionized calcium ≤6.5 mg/dL (≤1.6 mmol/L). 11. Resolved acute effects of any prior therapy to baseline severity or CTCAE Grade ≤1

1. Smoldering MM. 2. Plasma cell leukemia 3. Systemic amyloid light chain amyloidosis. 4. POEMS Syndrome 5. Stem cell transplant within 12 weeks prior to enrollment, or active GVHD. 6. Impaired cardiovascular function or clinically significant cardiovascular diseases, defined as any of the following within 6 months prior to enrolment: a. Acute myocardial infarction or acute coronary syndromes (eg, unstable angina, coronary artery bypass graft, coronary angioplasty or stenting, symptomatic pericardial effusion); b. Clinically significant cardiac arrhythmias (eg, uncontrolled atrial fibrillation or uncontrolled paroxysmal supraventricular tachycardia); c. Thromboembolic or cerebrovascular events (eg, transient ischemic attack, cerebrovascular accident, deep vein thrombosis or pulmonary embolism); d. Prolonged QT syndrome (or QTcF > 470 msec at screening). 7. Ongoing Grade 2 or higher peripheral sensory or motor neuropathy. 8. History of Guillain-Barre syndrome or GBS variants, or history of any Grade > 3 peripheral motor polyneuropathy.9. Active HBV, HCV, SARS-CoV2, HIV, or any active, uncontrolled bacterial, fungal, or viral infection. Active infections must be resolved at least 14 days prior to enrollment. a. COVID-19/SARS-CoV2: While SARS-CoV2 testing is not mandated for entry into this study, testing should follow local clinical practice standards. If a participant has a positive test result for SARS-CoV2 infection, is known to have asymptomatic infection or is suspected of having SARS-CoV2, he/she is excluded. 10. Any other active malignancy within 3 years prior to enrolment, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ. 11. Participants with known or suspected hypersensitivity to the study interventions or any of their excipients. 12. Other surgical (including major surgery within 14 days prior to enrolment), medical or psychiatric conditions including recent (within the past year) or active suicidal ideation/behaviour or laboratory abnormality that may increase the risk of study participation or, in the investigator’s judgment, make the participant inappropriate for the study. 13. Previous treatment with a BCMA-directed therapy. 14. Anti-CD38-directed therapy within 6 months preceding the first dose of treatment in this study. 15. Part 2 only: Refractory to prior anti-CD38-directed therapy (disease progression while on or within 60 days of the end of the last dose). 16. Part 2 only: Previous pomalidomide therapy. 17. Concurrent or anticipated use of a non-topical medication known to be a strong CYP1A2 inhibitor within 7 days prior to first dose of study intervention and throughout study duration. Refer to Section 6.8 Concomitant Therapy. 18. Live attenuated vaccine must not be administered within 4 weeks of the first dose of study intervention.19. Administration with an investigational product (e.g. drug or vaccine) concurrent with study intervention or within 30 days (or as determined by the local requirement) or 5 half-lives preceding the first dose of study intervention used in this study (whichever is longer). A participant may be eligible if they are in the follow-up phase of an investigational study if they meet the criteria for time elapsed from previous administration of investigational product. Cases must be discussed with sponsor’s medical monitor to judge eligibility. 20. For females of childbearing potential: Serum pregnancy test positive at screening. 21. Active inflammatory gastrointestinal disease, chronic diarrhea, known diverticular disease or previous gastric resection or lap band surgery. Gastroesophageal reflux disease under treatment with proton pump inhibitors is allowed (assuming no drug interaction potential).