Study of SIM0500 Alone in Participants With Relapsed or Refractory Multiple Myeloma

Inclusion Criteria:

1. Voluntary participation and signature of informed consent form.

2. ≥18 years of age.

3. Have documented diagnosis of relapsed or refractory multiple myeloma according toCriteria for Response to Multiple Myeloma Treatment(IMWG)diagnostic criteria whohave failed all established standard of care.

4. Life expectancy ≥12 weeks.

5. Eastern Cooperative Oncology Group (ECOG) score of 0 or 1.

6. Adequate hematologic, hepatic, and renal function.

Exclusion Criteria:

1. Toxicities from previous anticancer therapies should have resolved to baselinelevels or to Grade 1 or less except for alopecia or peripheral neuropathy.

2. Active hepatitis B (HBsAg positive and HBV DNA ≥ 1×104 copies/mL or ≥ 2,000international unit [IU]/mL) or hepatitis C (HCV antibody positive and HCV RNA ≥ ULN)infection; participant with HBsAg positive or detective HBV-DNA at screening shouldreceive antiviral treatment as per local practice during the trial.

3. Known human immunodeficiency virus (HIV) infection or acquired immunodeficiencysyndrome (AIDS).

4. Participant is pregnant or breastfeeding, or expecting to conceive or fatherchildren within the projected duration of the trial.

5. Active known or suspected autoimmune disease. Participants with vitiligo, residualhypothyroidism only requiring hormone replacement, psoriasis not requiring systemictreatment or conditions not expected to recur in the absence of an external trigger,type 1 diabetes mellitus (blood glucose can be controlled by insulin therapy) can beincluded.

6. Current or previous other malignancy within 3 years of study entry, except basal orsquamous cell skin cancer, superficial bladder cancer, or carcinoma in situ of theprostate, cervix or breast.

7. Known active central nervous system (CNS) involvement or exhibits clinical signs ofmeningeal involvement of multiple myeloma.

8. Participants with known active infection within 14 days prior to the first SIM0500.