• Patient or his or her legal guardian voluntarily participates in and signs an informed consent form;

• Aged ≥ 18 years and ≤ 75 years;

• Diagnosed as Multiple Myeloma (MM) according to the international standard for multiple myeloma (IMWG);

• The presence of measurable disease at screening meets one of the following criteria:Serum M-protein ≥ 1.0 g/dL or Urine M-protein ≥ 200 mg/24h or diagnosed as Light-chain MM without measurable disease in serum and urine; Serum free light chain ≥ 10 mg/dL with an abnormal κ/λ ratio;

• Patients must relapse or be refractory after three or more lines of therapy, which at least include: one Proteasome Inhibitor (PI), one Immunomodulatory Drug (IMiD), and one anti-CD38 monoclonal antibody;

• diagnosed as relapsed/refractory disease or primary refractory disease;

• The last treatment is ineffective, or the disease progresses within 60 days after the end of the last therapy;

• Patients must recover from the toxicity of the last therapy (\< grade 2 by CTCAE criteria);

• ECOG score 1-2 points and the expected survival period ≥ 3 months;

⁃ Liver, kidney and cardiopulmonary functions meet the following requirements:

∙ Total bilirubin ≤ 1.5×ULN, alanine aminotransferase (ALT) ≤ 3 × ULN and aspartate aminotransferase (AST) ≤ 3 × ULN;

‣ Serum creatinine ≤ 1.5×ULN, or creatinine clearance ≥ 60 mL/min;

‣ Hemoglobin (Hb) ≥ 50 g/L without prior blood transfusion within 7 days;

‣ Baseline peripheral oxygen saturation \> 92%;

‣ Corrected serum calcium ≤ 12.5 mg/dL (≤ 3.1 mmol/L) or free (ionized, ionic) calcium ≤ 6.5 mg/dL (≤ 1.6 mmol/L);

‣ Left ventricular ejection fraction (LVEF) \> 45%, without confirmed pericardiac effusion and abnormal electrocardiography with clinical significance;

‣ Without clinically significant pleural effusion;

⁃ Venous access could be established; without contraindications of apheresis.