Clinical Study to Evaluate the Safety and Feasibility of spCART-269 Injection in the Treatment of MM

Inclusion Criteria: 1. The patient was diagnosed as active MM according to the diagnostic criteria of the International Myeloma Working Group (IMWG) 2. The patient meets any of the following: 1. Have received at least 3 treatment options in the past and include alkylating agents, proteasome inhibitors and immunomodulators; 2. If the patient has received a regimen containing proteasome inhibitor and immunomodulator for at least 2 courses, and the effect is not good (such as disease progression within 60 days of treatment) 3. Voluntary participation in clinical research and signing informed consent 4. Age 18-65, regardless of gender 5. Expected survival time is greater than 12 weeks 6. If the patient has received autologous hematopoietic stem cell transplantation in the past, a 90-day interval is required 7. Normal bone marrow hematopoietic function, blood routine: hemoglobin ≥ 100 g/L; absolute neutrophil ≥ 1.5×10\^9/L; platelet count ≥ 100×10\^9/L 8. Liver function: serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 (ULN) times the upper limit of normal value (if abnormal liver function is mainly caused by tumor infiltration, it can be ≤ 5 times the upper limit of normal value (ULN) )), bilirubin \<2.0 mg/dL 9. Renal function: BUN is 9-20 mg/dL, serum creatinine ≤ 1.5 times the upper limit of normal (ULN), endogenous creatinine clearance rate ≥50 ml/min 10. Serum virus EBV, CMV, HBV, HCV, HIV and syphilis antibodies are negative 11. Heart function: good hemodynamic stability, left ventricular ejection fraction (LVEF) ≥ 45% 12. ECOG physical status score 0-2 13. Possess apheresis or sufficient venous access for venous blood, and no other contraindications for leukocyte separation 14. T cells can be successfully expanded in vitro 15. Women of childbearing age who provide negative reports of pregnancy tests with serum or urine before reinfusion 16. Adults with fertility requirements, regardless of sex, contraception within one year after treatment Exclusion Criteria: 1. ECOG score ≥ 3 points 2. Female patients during pregnancy or lactation 3. Pathological examination revealed malignant tumor cells with T cell origin 4. Organ failure: Heart failure grade Ⅲ and Ⅳ; liver reaches Child-Turcotte liver function grade C; renal failure and uremia; respiratory failure; consciousness disorder 5. Patients with acute or chronic GVHD after allogeneic hematopoietic transplantation, or using hormones or immunosuppressants within 30 days 6. Patients with HIV infection or active hepatitis 7. There are other uncontrolled active infections 8. Those who may be allergic to cytokines 9. Those who have used any gene therapy products 10. Those who participated in other clinical studies 4 weeks before enrollment (except those who did not receive treatment in clinical studies) 11. Patients with systemic autoimmune diseases or immunodeficiency diseases 12. Definite neuropathy or psychosis, including authors of dementia or epilepsy 13. Those with lung or intestinal tumor infiltration 14. Patients that other researchers think are not suitable for enrollment