Inclusion criteria:
1. Age 18-80 years with expected survival > 3 months.
2. Confirmed diagnosis of active multiple myeloma with detectable BCMA expression in malignant cells.
3. Relapsed or refractory disease with at least 2 prior lines of treatment, including a proteasome inhibitor and immunomodulator, without achieving significant efficacy.
4. Measurable disease at screening according to IMWG criteria, as defined by any of the following: Serum monoclonal paraprotein (M-protein) level ≥1.0 g/dL or urine M-protein level being as defined； or light chain MM without measurable disease in the serum or the urine； serum immunoglobulin free light chain disease dL and abnormal serum immunoglobulin kappa/lambda free light chain ratio.
5. ECOG performance status of 0-1.
6. Acceptable cardiac, liver, and kidney function.
7. Signed written informed consent.
Exclusion criteria:
1. Pregnant or lactating women.
2. Uncontrolled active infection, HIV infection, or positive syphilis serology reaction.
3. Active hepatitis B or hepatitis C infection.
4. Recent or current use of glucocorticoids or other immunosuppresses.
5. Severe cardiac, liver, renal insufficiency, diabetes, or other diseases.
6. Participation in other clinical research in the past three months.