A Study of Atezolizumab (Anti-Programmed Death-Ligand 1 [PD-L1] Antibody) Alone or in Combination With an Immunomodulatory Drug and/or Daratumumab in Participants With Multiple Myeloma (MM)

Participants will receive intravenous (IV) atezolizumab until loss of clinical benefit, withdrawal, or study end. Cohorts A to C will receive 1200 milligrams (mg) on Day 1 of each 21-day cycle. Cohorts D to F (combination with daratumumab) will receive 840 mg on Days 2 and 16 of Cycle 1 and on Days 1 and 15 of each 28-day cycle thereafter.

Participants will receive 16 milligrams per kilogram (mg/kg) IV daratumumab until loss of clinical benefit, withdrawal, or study end. Treatment will be per the U.S. Package Insert and given on Days 1, 8, 15, 22 of Cycles 1 and 2; on Days 1 and 15 of Cycles 3 to 6; and on Day 1 of each 28-day cycle thereafter.

Lenalidomide will be administered orally (PO) until loss of clinical benefit, withdrawal, or study end. Cohort B1 will receive 10, 15, or 25 mg, ascending-dose lenalidomide, on Days 1-14 of each 21-day cycle. Cohort C will receive 10 mg on Days 1-14 of each 21-day cycle, beginning in Cycle 4. Cohort E (combination with daratumumab) will receive 10, 15, or 25 mg on Days 1-21 of each 28-day cycle. Participants in Cohort E1 will receive ascending-dose lenalidomide, and those in Cohort E2 will receive lenalidomide at the MTD as determined in Cohort E1.

Pomalidomide will be administered PO until loss of clinical benefit, withdrawal, or study end. Cohort F (combination with daratumumab) will receive 2 or 4 mg on Days 1-21 of each 28-day cycle. Participants in Cohort F1 will receive ascending-dose pomalidomide, and those in Cohort F2 will receive pomalidomide at the MTD as determined in Cohort F1.

Participants will receive either 20mg or 40mg of dexamethasone PO every 7 days from Day 1 of each cycle.