BCMA-targeted LCAR-BCDR Cells in Patients With Relapsed/Refractory Multiple Myeloma

Inclusion Criteria: 1. The subject voluntarily participates in the clinical study; Fully understand and be Informed of the study and sign the Informed consent (Informed Consent Form, ICF); Willing to follow and able to complete all test procedures; Informed consent must be obtained before initiating any tests or procedures related to the study that are not part of the standard treatment of the subject's disease; 2. Subjects ≥ 18 years of age. 3. Documented initial diagnosis of MM according to IMWG diagnostic criteria. 4. Presence of measurable disease at screening. 5. Received a PI and an IMiD (except thalidomide). 6. Received at least 3 prior lines of therapy for multiple myeloma, undergone at least 1 complete cycle of treatment for each line, unless progressive disease (PD) was documented by IMWG criteria as the best response to the regimen. Also, subjects refractory or intolerant to any PI and any IMiD in their previous treatment afterwards are eligible. 7. Expected survival ≥ 3 months. 8. Clinical laboratory values meet screening visit criteria 9. Fertile women must be negative using a highly sensitive serum pregnancy test (β human chorionic gonadotropin \[β -HCG\]) at screening time and before initial treatment with cyclophosphamide and fludarabine; Exclusion Criteria: 1. No response to prior BCMA-targeted CAR-T therapy (except in subjects who relapsed after CR to prior CAR-T treatment). 2. Prior treatment with any antibody targeting BCMA. 3. Diagnosed or pretreated for an invasive malignancy other than multiple myeloma. 4. Prior anti-tumor treatment (before pretreatment) with insufficient washout period. 5. Known active, or prior history of central nervous system (CNS) involvement, or clinical signs of membrane/spinal membrane involvement of multiple myeloma. 6. Positive of any hepatitis B surface antigen (HBsAg), hepatitis B virus deoxyribonucleic acid (HBV DNA), hepatitis C antibody (HCV-Ab), hepatitis C virus ribonucleic acid (HCV RNA), human immunodeficiency virus antibody (HIV-Ab) at the time of screening. 7. Serious underlying medical conditions 8. Male subjects who have a birth plan during the study period or within 1 year after the study treatment. 9. Female subjects who are pregnant, breast-feeding, or plan to become pregnant during the study period or within 1 year after the study treatment. 10. The investigator considered that the subjects were not suitable for any conditions of participation in the study.