Anti-BCMA CAR-NK Therapy in Relapsed or Refractory Multiple Myeloma

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 immunosuppressors. 5. Severe cardiac, liver, renal insufficiency, diabetes, or other diseases. 6. Participation in other clinical research in the past three months.