Although the anti-CD19 CAR-T cell therapies have gained significant results in patients with relapsed and refractory B-cell hematologic malignancies. There are few effective treatments for MM(multiple myeloma). BCMA (B cell maturation antigen) is a promising target for malignant plasma cells. Therefore, we designed a clinical trial using anti-BCMA CAR-T cell therapy for patients with relapsed and refractory multiple myeloma.

Inclusion Criteria:

Subjects must meet the following criteria for inclusion in the study： 1) Male or female subjects between the ages of 18 and 75（including critical values）； 2) Subjects histologically confirmed as relapsed and refractory multiple myeloma.

Positive expression of BCMA(>50%) in malignant plasma cells； Approved anti-tumor therapies, such as systemic chemotherapy, systemic radiotherapy, and immunotherapy, have been completed for at least 2 weeks before the precondition.

ECOG≤1； Life expectancy ≥ 3 months； Neutrophil absolute count ≥ 1×10^9/L； platelet count ≥ 50×10^9/L； Absolute lymphocyte count ≥ 1×10^8/L ；

Adequate organ function reserve :

GPT, GST ≤ 2.5× UNL（upper normal limit）； Creatinine clearance (Cockcroft Gault method）≥60mL/min； Serum total bilirubin ≤1.5× UNL； The left ventricular ejection fraction (LVEF) ≥ 50% was diagnosed by echocardiography, and there was no clinically significant pericardial effusion and ECG abnormality； Basic oxygen saturation in indoor natural air environment > 92%； It can establish the venous access needed for collection without the contraindications of leukocyte collection； For female subjects of childbearing age, results are negative in urine pregnancy test before screening and administration, and subjects agree to take effective contraceptive measures at least one year after infusion; Male subjects with partners' fertility must agree to use effective barrier contraceptive methods at least one year after infusion, and avoid sperm donation； Voluntary signing of informed consent;

Exclusion Criteria:

Any of the following points shall be deemed as no entry into this study：

Other tumors except cured non-melanoma skin cancer, cervical cancer in situ, superficial bladder cancer, breast duct cancer in situ, or other malignant tumors with complete remission of more than 5 years)； Severe mental disorders； A history of genetic diseases such as Fanconi anemia, Shudder-Dale syndrome, Costman syndrome, or any other known bone marrow failure syndrome； Heart disease with grade III-IV heart failure [NYHA classification], myocardial infarction, angioplasty or stenting, unstable angina or other heart diseases with prominent clinical symptoms within one year before admission； Subjects with any indwelling catheter or drainage tube (such as percutaneous nephrostomy tube, bile drainage tube or pleura/peritoneum/pericardium catheter), should be excluded. (Special central venous catheter is allowed)； Subjects with a history of CNS lymphoma, CSF malignant cells, or brain metastasis； Subjects with a history of CNS disease,such as epilepsy, cerebral ischemia/hemorrhage, dementia, cerebellar disease, or any autoimmune disease involving CNS； Any of the following virological ELISA results are positive: HIV antibody, HCV antibody, TPPA, HBsAg； Active infection requiring systematic treatment within 2 weeks before single collection； Subjects with known severe allergic reactions to cyclophosphamide or fludarabine, or diagnosed as the allergy； History of autoimmune diseases (e.g. Crohn disease, rheumatoid arthritis, systemic lupus erythematosus) that cause end-organ damage or require systemic immunosuppressive medications or systemic disease modifying drugs in the past 2 years； Presence of pulmonary fibrosis； Subjects who have received other clinical trial treatment within 4 weeks before participating in this trial should be excluded. Or the signing date of informed consent is within 5 half-lives of the last application of another clinical trial (whichever is longer)； Subjects with poor compliance due to physiological, family, social, geographical and other factors, or those unable to cooperate with the study plan or follow-up； At the discretion of the investigator, there are complications requiring systemic corticosteroid therapy (≥ 5mg / day of prednisone or equivalent dose of other corticosteroids) or other immunosuppressive drugs within 6 months after this clinical research treatment； The lactating woman who is reluctant to stop breastfeeding； Any other condition considered unsuitable by the investigator.