• Subjects must satisfy all the following criteria to be enrolled in the study:

‣ age 18 to 75 years old, male or female.

⁃ Subjects have had at least 3 prior lines of therapy including chemotherapy based on proteasome inhibitors (PIs) and immunomodulatory agents (IMiDs).

‣ According to the International Myeloma Working Group (IMWG) consensus (2016) standard on multiple myeloma, the disease has recurred, progressed or is refractory, or according to the IMWG consensus (2013) standard on plasma cell leukemia (Appendix 4), the disease appears relapse, progress or refractory;

⁃ Evidence of cell membrane GPRC5D expression, as determined by a validated immunohistochemistry (IHC) or flow cytometry of tumor tissue (e.g., bone marrow biopsies, or plasmacytoma).

⁃ The subjects should have measurable disease based on at least one of the following parameters:

‣ The proportion of primitive immature or monoclonal plasma cells detected by bone marrow cytology, bone marrow biopsy, or flow cytometry is ≥ 10%.

‣ Serum M-protein ≥ 0.5 g/dL. Urine M-protein ≥ 200 mg/24 hrs. For those whose Serum or Urine M-protein does not meet the measurable criteria but the light chain type, serum free light chain (sFLC) : involved sFLC level ≥ 10mg/dL (100 mg/L) provided serum FLC ratio is abnormal.

‣ In subjects with extramedullary myeloma, if there are no other evaluable lesions, require extramedullary lesions with a maximum diameter of ≥2cm

⁃ ECOG performance score 0-2.

⁃ Estimated life expectancy ≥ 12 weeks.

⁃ Subjects should have adequate organ function:

• Hematology: Absolute neutrophil count (ANC) ≥1×10\^9 /L (prior use of growth factor support is permitted, but subjects must not have received supportive treatment within 7 days prior to laboratory examination); absolute lymphocyte count (ALC) ≥0.3×10\^9 /L; platelets ≥40×10\^9 /L (subjects must not have received blood transfusion support within 7 days prior to laboratory examination); hemoglobin ≥60 g/L (subjects must not have received transfusion of red blood cells \[RBC\] within 7 days prior to laboratory examination; the use of recombinant human erythropoietin is permitted).

∙ Liver function: Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5×upper limit of normal (ULN); total serum bilirubin ≤ 1.5×ULN.

∙ Renal function: Creatinine clearance rate (CrCl) calculated according to Cockcroft-Gault formula ≥ 40 ml/min.

∙ Coagulation function: Fibrinogen ≥ 1.0 g/L; activated partial thromboplastin time (APTT) ≤ 1.5×ULN, prothrombin time (PT) ≤1.5×ULN.

∙ SpO2 \> 91%.

∙ Left ventricular ejection fraction (LVEF) ≥ 50%.

⁃ The subject and his/her spouse agree to use an effective contraceptive tool or medication (excluding safety period contraception) for one year from the date of the subject's informed consent to the date of CAR T cell infusion.

⁃ Subject must sign the informed consent form approved by ethics board in person before starting any screening procedure.