A Study of Humanized BCMA-targeted CAR-T Cells Therapy for Refractory/Relapsed Multiple Myeloma

Inclusion Criteria: 1. Histologically confirmed diagnosis of multiple myeloma (MM): 1. Patients with BCMA positive relapsed/refractory MM; 2. Relapsed after hematopoietic stem cell transplantation; 3. Cases with recurrent positive minimal residual disease; 4. Extramedullary leision which is hard to be eradicated by chemotherapy or radiotherapy. 2. Anticipated survival time more than 12 weeks; 3. Male or female aged 30-75 years; 4. Those who voluntarily participated in this trial and provided informed consent. Exclusion Criteria: Subjects with any of the following exclusion criteria were not eligible for this trial: 1. History of craniocerebral trauma, conscious disturbance, epilepsy, cerebrovascular ischemia, and cerebrovascular hemorrhagic diseases; 2. Electrocardiogram shows prolonged QT interval, severe heart diseases such as severe arrhythmia in the past; 3. Pregnant (or lactating) women; 4. Patients with severe active infections (excluding simple urinary tract infection and bacterial pharyngitis); 5. Active infection of hepatitis B virus or hepatitis C virus; 6. Concurrent therapy with systemic steroids within 2 weeks prior to screening, except for the patients recently or currently receiving in haled steroids; 7. Previously treated with any CAR-T cell product or other genetically-modified T cell therapies; 8. Creatinine\>2.5mg/dl, or ALT / AST \> 3 times of normal amounts, or bilirubin\>2.0 mg/dl; 9. Other uncontrolled diseases that were not suitable for this trial; 10. Patients with HIV infection; 11. Any situations that the investigator believes may increase the risk of patients or interfere with the results of study.