• 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) ≥ 10 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 blood transfusion within 2 weeks and no G-CSF/GM-CSF supportive treatment within 1 week prior to screening test):

• Hemoglobin level ≥ 80 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.