• Age ≥18 years old, regardless of gender.

• Previously treated with at least three drugs (including PI, IMiD, and anti-CD38 antibody), and relapsed/refractory after the most recent anti-MM therapy.

• Diagnosis of MM according to IMWG criteria with measurable lesions, meeting at least 1 of the following criteria:

‣ Serum M protein ≥ 0.5g/dL (≥ 5 g/L); or

⁃ Urine M protein ≥ 200mg/24 hours; or

⁃ When the serum free light chain (FLC) ratio is abnormal, the affected FLC level is ≥10mg/dL (≥100 mg/L) (the normal FLC ratio is 0.26 to 1.65).

• ECOG performance status score is 0, 1, or 2.

• Willing and able to comply with the study schedule and all other study protocol requirements.

• Women of childbearing potential (WOCBP) (infertile women are defined as sexually mature females who had undergone a hysterectomy or bilateral oophorectomy or bilateral salpingectomy or bilateral tubal ligation/closure, or who are infertile due to a congenital or acquired condition or spontaneously menopausal for ≥ 12 months) must have a negative blood pregnancy test during the screening. Female subjects of childbearing potential and male subjects with fertility must use a highly effective method of contraception from screening to 6 months after the last treatment.