A Study in Participants With Relapsed or Refractory Multiple Myeloma for IBI3003

Inclusion Criteria： 1. Age ≥18 years. 2. Documented initial diagnosis of multiple myeloma according to IMWG diagnostic criteria. 3. At least one of the following measurable disease indicators: * Serum M-protein ≥ 5 g/L（For IgA and IgD subtypes, it is recommended to use quantitative immunoglobulin measurements instead of M protein） * Urine M-protein ≥200 mg/24h * Serum free light chain (FLC) test: affected FLC level ≥100 mg/L and abnormal serum FLC ratio (\<0.26 or \>1.65) 4. Life expectancy ≥3 months. 5. Fertile females and sexually active fertile males must agree to use highly effective contraception (failure rate \<1% per year) during the study and for 90 days after the last dose of the investigational drug. For participants in the clinical trial, contraceptive measures must comply with local regulations regarding the use of contraceptive methods. Females and males must agree not to donate eggs (ova, oocytes) or sperm during the study and for 90 days after the last dose of the investigational drug. 6. Willing and able to comply with the prohibitions and restrictions specified in this protocol. Exclusion Criteria： 1. Previous treatment with any BCMA-targeted therapy and any GPRC5D-targeted therapy. Patients who have received either BCMA-targeted or GPRC5D-targeted therapy are allowed to participate in the study. 2. Known active CNS involvement or exhibits clinical signs of meningeal involvement of multiple myeloma. 3. Spinal cord compression that leads to limited self-care ability occurs within six months prior to informed consent or is expected to occur in the near future. 4. Have history of primary immunodeficiency. 5. Have history of organ transplantation. 6. Have received allogeneic hematopoietic stem cell transplantation within 6 months before the first administration of the study drug, or have received autologous stem cell transplantation within 3 months before the first administration of the study drug.