• Patients must meet all of the following inclusion criteria to be eligible to enroll in this study:

• Known and written informed consent (ICF) voluntarily.

• Age ≥ 18 years and ≤ 75 years.

• Patients with multiple myeloma who have received first-line treatment (induction, autologous transplantation and maintenance as the same first-line treatment) and achieved at least partial remission in induction.

• At or after accepting first-line regimen, subjects must have progression disease (PD) recorded which is determined by researcher according to IMWG criteria.

• Any clinically significant non-hematological toxicities (except for hair loss, peripheral neuropathy, which is otherwise stipulated in Article 13 of the exclusion criteria) that relevant to previous therapies must have resolved to ≤Grade 2 prior to first dose of study drug.

• Left ventricular ejection fraction（LVEF ）≥50% by an echocardiogram or MUGA scan in 42 days before the first administration

• Adequate hepatic function: total bilirubin \< 2× upper limit of normal (ULN) (for patients with Gilbert's syndrome, a total bilirubin of \< 3× ULN is required), AST \< 2.5× ULN, and ALT \< 2.5× ULN.

• Adequate renal function: estimated creatinine clearance ≥ 20 mL/min (calculated using the formula of Cockroft-Gault).

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1, or 2.

⁃ Measurable MM as defined by at least one of the following:

∙ Serum M-protein (SPEP) ≥ 5 g/L

‣ 24 hours-Urinary M-protein excretion ≥ 0.2 g (200 mg)

‣ Serum FLC ≥ 100 mg/L with abnormal FLC ratio

⁃ Expected survival is more than 6 months.

⁃ Adequate hematopoietic function (no platelet transfusion within 2 weeks prior to screening test):

∙ Hemoglobin level ≥ 60 g/L

‣ ANC ≥ 1,000/mm3 (1.0×109/L)

‣ Platelet count ≥ 75,000/mm3 (75×109/L)

⁃ Female patients of childbearing potential must meet below two criteria:

∙ must agree to use effective contraception methods since signature in ICF, throughout the study and for 3 months following the last dose of study treatment.

‣ must have a negative serum pregnancy test at screening. Note: A woman is considered of childbearing potential following menarche and until becoming postmenopausal (defined as no menstrual period for a minimum of 12 months) or permanently sterile (having undergone a hysterectomy, bilateral salpingectomy or bilateral oophorectomy). A woman who is taking oral contraceptive or using intrauterine device is considered of childbearing potential.

⁃ Male patients (including those who have received vasectomy) must use a condom if sexually active with a female of child-bearing potential throughout the study and for 3 months following the last dose of study treatment.