A Study of DeepTag-GPRC5D Targeted CAR-T Cells Therapy for Refractory/Relapsed Multiple Myeloma

Inclusion Criteria: 1. Those who voluntarily participated in this trial and provided informed consent; 2. Gender unlimited，18<Age≤75; 3. Estimated life expectancy of minimum of 12 weeks; 4. ECOG 0-2; 5. Diagnosed as multiple myeloma according to the IMWG criteria; 6. Subjects failed treatment with at least 3 prior lines of therapy (including chemotherapy based on proteasome inhibitors (PIs) ，immunomodulatory agents (IMiDs) and CD38 antibody）, or recived the above three treatment methods experienced disease progression or recurrence during the most recent treatment process or within 6 months after the end of treatment, Difficulty in treatment includes primary difficulty in treatment ( patient has not achieved minimal remission or disease progression during treatment) or secondary difficulty in treatment (patient develops disease progression within 60 days after completion of treatment); 7. Women have a negative urine pregnancy test before the start of medication administration and agree to take effective contraceptive measures during the trial period until the last follow-up; 8. The blood routine meets the following standards: Lymphocyte count>0.3×10e9/L; Neutrophils ≥0.5×10e9/L; Hemoglobin ≥60g/L; Platelet ≥30×10e9/L Exclusion Criteria: 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 HIV infection; 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. The proiferation rate is less than 5 times response to CD3/CD28 co-stimulation signal; 8. Creatinine>2.5mg/dl, or ALT / AST > 3 times of normal amounts, or bilirubin>2.0 mg/dl; 9. Any situations that the investigator believes may increase the risk of patients or interfere with the results of study; 10. Patients who received anti-cancer chemotherapy or other medications within 2 weeks before screening; 11. Uncontrolled malignant tumors except MM, excluding malignant tumors that received radical treatment and no active disease was found within 3 years before enrollment; 12. Patients who received autologous hematopoietic stem cell transplantation (ASCT) within 8 weeks before screening, or who plan to undergo ASCT during the study period; 13. Patients received allogeneic stem cell therapy; 14. Any unsuitable to participate in this trial judged by the investigator.