A Study Comparing JNJ-68284528, a CAR-T Therapy Directed Against B-cell Maturation Antigen (BCMA), Versus Pomalidomide, Bortezomib and Dexamethasone (PVd) or Daratumumab, Pomalidomide and Dexamethasone (DPd) in Participants With Relapsed and Lenalidomide-Refractory Multiple Myeloma

Inclusion Criteria:

   - Measurable disease at screening as defined by any of the following: (a) Serum
   monoclonal paraprotein (M-protein) level greater than or equal to (>=) 0.5 gram per
   deciliter (g/dL) or urine M-protein level >=200 milligram (mg)/24 hours; or (b) Light
   chain multiple myeloma without measurable M-protein in the serum or the urine: Serum
   free light chain >=10 mg/dL and abnormal serum free light chain ratio

   - Have received 1 to 3 prior lines of therapy including a proteasome inhibitor (PI) and
   an immunomodulatory drug (IMiD)

   - Have documented evidence of PD by International Myeloma Working Group (IMWG) criteria
   based on investigator's determination on or within 6 months of their last regimen

   - Be refractory to lenalidomide per IMWG consensus guidelines (failure to achieve
   minimal response or progression on or within 60 days of completing lenalidomide
   therapy). Progression on or within 60 days of the last dose of lenalidomide given as
   maintenance will meet this criterion. For participants with more than 1 prior line of
   therapy, there is no requirement to be lenalidomide refractory to the most recent line
   of prior therapy. However, participants must be refractory to lenalidomide in at least
   one prior line

   - Have clinical laboratory values meeting the following criteria during the Screening
   Phase (re testing is allowed but the below criteria must be met in the latest test
   prior to randomization):

      1. Hemoglobin >=8 gram per deciliter (g/dL) (without prior RBC transfusion within 7
      days before the laboratory test; recombinant human erythropoietin use is
      permitted);

      2. Absolute neutrophil count (ANC) >=1 * 10^9 per liter (L) (without recombinant
      human granulocyte colony-stimulating factor [G-CSF] within 7 days and without
      pegylated G-CSF within 14 days of the laboratory test);

      3. Platelet count >=75 * 10^9/L (without prior platelet transfusion within 7 days
      before the laboratory test) in participants in whom less than (<) 50 percent (%)
      of bone marrow nucleated cells are plasma cells; platelet count >=50 * 10^9/L
      (without prior platelet transfusion within 7 days before the laboratory test) in
      participants in whom >=50% of bone marrow nucleated cells are plasma cells;

      4. Lymphocyte count >=0.3 * 10^9/L;

      5. Aspartate aminotransferase (AST) less than or equal to (<=)3 * upper limit of
      normal (ULN);

      6. Alanine aminotransferase (ALT) <=3 * ULN;

      7. Total bilirubin <=2.0 * ULN; except in participants with congenital
      bilirubinemia, such as Gilbert syndrome (in which case direct bilirubin <=1.5 *
      ULN is required);

      8. Estimated glomerular filtration rate >=40 milliliter per minute (mL/min) per 1.73
      meter square (m^2) (to be calculated using the Modification of Diet in Renal
      Disease [MDRD] formula)

Exclusion Criteria:

   - Prior treatment with chimeric antigen receptor T-cell (CAR-T) therapy directed at any
   target

   - Any previous therapy that is targeted to B-cell maturation antigen (BCMA)

   - Ongoing toxicity from previous anticancer therapy that has not resolved to baseline
   levels or to Grade 1 or less; except for alopecia

   - Participants with Grade 1 peripheral neuropathy with pain or Grade 2 or higher
   peripheral neuropathy will not be permitted to receive pomalidomide, bortezomib, and
   dexamethasone (PVd) as standard therapy or bridging therapy; however, participants may
   receive daratumumab, pomalidomide, and dexamethasone (DPd) as standard therapy or
   bridging therapy

   - Received a cumulative dose of corticosteroids equivalent to >=70 mg of prednisone
   within the 7 days prior to randomization

   - Monoclonal antibody treatment within 21 days

   - Cytotoxic therapy within 14 days

   - Proteasome inhibitor therapy within 14 days

   - Immunomodulatory drug (IMiD) therapy within 7 days