This is a randomized, double-blind, multicenter trial，parallel control designed to evaluate treatment with pomalidomide + QL2109 + dexamethasone compared with pomalidomide + DARZALEX FASPRO® + dexamethasone in the participants with relapsed or refractory Multiple Myeloma.

Inclusion Criteria:

• Males and females at least 18 years of age.

• Subject must have measurable disease of MM as defined by the criteria below:Serum M-protein level ≥0.5 g/dL or urine M-protein level ≥200 mg/24 hours; or Light chain multiple myeloma, for subjects without measurable disease in the serum or urine: Serum immunoglobulin free light chain (FLC) ≥10 mg/dL and abnormal serum immunoglobulin kappa lambda FLC ratio.

• Subjects must have received prior antimyeloma treatment. The prior treatment must have included both a PI- and lenalidomide-containing regimens. Subjects who received only 1 line of prior treatment must have demonstrated PD on or within 60 days of completion of the lenalidomide containing regimen (ie, lenalidomide refractory).

• Subjects must have documented evidence of PD based on the investigator's determination of response as defined by the modified IMWG criteria on or after the last regimen.

• Eastern Cooperative Oncology Group (ECOG) performance status score of ≤ 2.

• For subjects experiencing toxicities resulting from previous therapy, the toxicities must be resolved or stabilized to ≤Grade 1.

• Any of the following laboratory test results during Screening:

  1. Absolute neutrophil count ≥1.0 × 109/L;
  2. Hemoglobin level ≥75 g/L (≥4.65 mmol/L); (transfusions are not permitted to reach this level);
  3. Platelet count ≥75 × 109/L in subjects in whom <50% of bone marrow nucleated cells are plasma cells and platelet count ≥50 x 109/L in subjects in whom ≥50% of bone marrow nucleated cells are plasma cells;
  4. Alanine aminotransferase (ALT) level ≤2.5 times the upper limit of normal (ULN);Aspartate aminotransferase (AST) level ≤2.5 x ULN;
  5. Total bilirubin level ≤1.5 x ULN, (except for Gilbert Syndrome: direct bilirubin ≤1.5 × ULN);
  6. Creatinine clearance ≥30 mL/min
  7. Serum calcium corrected for albumin ≤14.0 mg/dL (≤3.5 mmol/L), or free ionized calcium ≤ 6.5 mg/dL (≤1.6 mmol/L).

Exclusion Criteria:

• Subject has plasma cell leukemia (>2.0 × 109/L circulating plasma cells by standard differential) or Waldenström's macroglobulinemia or POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes) or amyloidosis.
• History of malignancy (other than MM) within 3 years before the date of randomization (exceptions are squamous and basal cell carcinomas of the skin, carcinoma in situ of the cervix or breast, or other non-invasive lesion that in the opinion of the investigator, with concurrence with the sponsor's medical monitor, is considered cured with minimal risk of recurrence within 3 years).
• Clinical signs of meningeal involvement of MM.
• Previous therapy with any anti-CD38 monoclonal antibody.
• Previous exposure to pomalidomide.
• Subject has received antimyeloma treatment within 2 weeks or 5 pharmacokinetic half-lives of the treatment, whichever is longer, before the date of randomization. The only exception is emergency use of a short course of corticosteroids (equivalent of dexamethasone 40 mg/day for a maximum of 4 days) for palliative treatment before Cycle 1, Day 1 (C1D1).
• Previous allogenic stem cell transplant; or autologous stem cell transplantation (ASCT) within 12 weeks before C1D1.
• Subject has had major surgery within 2 weeks before randomization, or has not fully recovered from an earlier surgery, or has surgery planned during the time the subject is expected to participate in the study or within 2 weeks after the last dose of study drug administration.
• Ongoing ≥ Grade 2 peripheral neuropathy.
• Subject had ≥Grade 3 rash during prior therapy.
• Pregnant or nursing women.