• The patient or his/her guardian understands and voluntarily signs the informed consent, and is expected to complete the follow-up examination and treatment of the study procedure;

• Age 18-75 years old, gender unlimited;

• Patients diagnosed with multiple myeloma according to International Myeloma Working Group(IMWG) diagnostic criteria;

• Subjects who had failed treatment with at least 3 drugs of different mechanisms (including chemotherapy, proteasome inhibitors, immunomodulators, etc.), or had progressed or relapsed during the last treatment period or within 6 months after the end of treatment;

• The presence of measurable lesions at screening was determined according to any of the following criteria, defined as: (1) serum monoclonal immunoglobulin (M-protein) level ≥1.0 g/dL; (2) urine M protein level ≥200 mg/ 24h; (3) Light chain multiple myeloma diagnosed with no measurable lesion in serum or urine: serum immunoglobulin free light chain ≥10 mg/dL and serum immunoglobulin κ/γ free light chain ratio abnormal;

• The patient has recovered from the toxicity of the prior treatment, i.e., CTCAE toxicity grade \< 2 (unless the abnormality is related to the tumor or is stable as judged by the investigator and has little impact on safety or efficacy);

• Eastern cooperative oncology group (ECOG) score is 0-2;

• Survival is expected to be greater than 3 months;

• Adequate liver , kidney and cardiopulmonary function;

⁃ Willingness to complete the informed consent process and to comply with study procedures and visit schedule.