Inclusion Criteria:
* Aged 18-75 years, gender is not limited;
* Patients diagnosed as relapsed/refractory multiple myeloma according to the International Myeloma Working Group (IMWG 2014) criteria for multiple myeloma after at least 3 lines of treatment (including at least one proteasome inhibitor and an immunomodulator based chemotherapy regimen), and at least one complete treatment cycle per line of treatment; Documented disease progression during or within 12 months after the most recent antimyeloma therapy (not limited to 12 months after CAR-T therapy as the last line of therapy);
* The presence of one or more measurable lesions at screening was defined as any of the following: 1) serum M-protein ≥0.5g/dL (≥5g/L), 2) urinary M-protein level ≥200 mg/24 hours; 3) serum free light chain (sFLC) ≥100 mg/L and serum κ/λ free light chain ratio abnormal (\<0.26 or \>1.65);
* Good organ function;
* ECOG score ≤1;
* The predicted survival time was ≥12 weeks;
* Female subjects of childbearing age or male subjects with partners of women of childbearing age agreed to use effective methods of contraception throughout the trial and for 12 months after cell infusion;
* The subjects voluntarily participated in the study, signed the informed consent form, and complied with the follow-up.
Exclusion Criteria:
* A history of allergy to any component of the cell product;
* Patients who had used CAR-T cell therapy or any other gene transduction or other therapeutic products within 3 months after signing the informed consent, except those with undetectable CAR-T cells or CAR-T cells below the lower limit of detection;
* Subjects had plasma cell leukemia, Waldenström's macroglobulinaemia, POEMS syndrome, or primary light chain amyloidosis;
* Patients with a history of any of the following cardiovascular and cerebrovascular diseases within the preceding 6 months were screened;
1. Congestive heart failure (New York Heart Association \[NYHA\]≥III), congenital long QT syndrome, left front half block (double bundle block), asymptomatic right bundle branch block allowed; Myocardial infarction, unstable angina pectoris, coronary angioplasty, stent implantation, coronary/peripheral artery bypass grafting;
2. Cerebrovascular accident (CVA) and transient ischemic attack (TIA);
3. Severe arrhythmias requiring treatment (e.g., sustained ventricular tachycardia, ventricular fibrillation, torsades de pointes, etc.); d: Subjects had uncontrolled hypertension (systolic blood pressure greater than 160 mmHg and/or diastolic blood pressure greater than 100 mmHg), a history of hypertensive crisis, or hypertensive encephalopathy;
* Pulmonary embolism, or deep venous thrombosis of the lower extremity requiring anticoagulation, or active lung disease and/or pneumonia have occurred within 6 months prior to screening;
* Hepatitis B surface antigen (HBsAg) positive; Hepatitis B core antibody (HBcAb) and HBV DNA in peripheral blood were positive. Hepatitis C virus (HCV) antibody positive and HCV RNA positive; Treponema pallidum antibody was positive;
* Patients with known systemic lupus erythematosus, co-active or uncontrolled autoimmune diseases (e.g., Crohns disease, rheumatoid arthritis, autoimmune hemolytic anemia, etc.), primary or secondary immunodeficiency (e.g., HIV infection or severe infectious diseases);
* Patients with previous or concurrent uncured malignant tumors with unstable control, affecting the long-term survival of the subjects, excluding cured cervical carcinoma in situ, non-invasive basal cell or squamous cell skin cancer, or other malignant tumors with local prostate cancer after radical treatment, ductal carcinoma in situ after radical treatment and no recurrence for at least 5 years;
* Patients with current or previous history of central nervous system disease, such as seizures, stroke, severe brain injury, aphasia, paralysis, dementia, Parkinson's disease, mental illness, etc.;
* Have central nervous system (CNS) involvement or symptoms of CNS involvement (including cranial neuropathy and extensive lesions or spinal cord compression);
* Patients had undergone previous solid-organ transplantation or allogeneic hematopoietic stem-cell transplantation (allo-HSCT) 6 months before screening or autologous stem-cell transplantation within 3 months before apheresis;
* Patients with acute or chronic graft-versus-host disease (GVHD) at screening time;
* The following anti-MM treatments were used at the indicated times prior to apheresis:
1. Use of any immunosuppressant or radiotherapy within 2 weeks prior to apheresis;
2. Received cytotoxic or proteasome inhibitors or small-molecule targeted therapy within 2 weeks of preapheresis or 3 half-lives, whichever is shorter;
3. Received any macromolecular therapy such as monoclonal antibodies within 4 weeks prior to anapheresis or within 3 half-lives, whichever is shorter;
4. Received immunomodulator within 1 week;
* The patient had a history of live vaccination within 4 weeks before signing ICF;
* Subjects had a history of mental illness, or substance abuse;
* Subjects were pregnant or lactating;
* If participating in other interventional clinical studies before apheresis, the requirements of drug washout before apheresis should be met;
* The investigator believes that there are other factors unsuitable for inclusion or affecting participants' participation in or completion of the study.
