Safety and Efficacy Study of An Anti-CD38 Antibody Drug Conjugate in Relapsed or Refractory Multiple Myeloma

Inclusion Criteria:

1. Age ≥18 years old, regardless of gender.
2. Previously treated with at least three drugs (including PI, IMiD, and anti-CD38antibody), and relapsed/refractory after the most recent anti-MM therapy.
3. Diagnosis of MM according to IMWG criteria with measurable lesions, meeting at least 1of 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 levelis ≥10mg/dL (≥100 mg/L) (the normal FLC ratio is 0.26 to 1.65).

4. ECOG performance status score is 0, 1, or 2.
5. Willing and able to comply with the study schedule and all other study protocolrequirements.
6. Women of childbearing potential (WOCBP) (infertile women are defined as sexuallymature females who had undergone a hysterectomy or bilateral oophorectomy or bilateralsalpingectomy or bilateral tubal ligation/closure, or who are infertile due to acongenital or acquired condition or spontaneously menopausal for ≥ 12 months) musthave a negative blood pregnancy test during the screening. Female subjects ofchildbearing potential and male subjects with fertility must use a highly effectivemethod of contraception from screening to 6 months after the last treatment.

Exclusion Criteria:

1. Known hypersensitivity to any of the ingredients of this product.
2. Diagnosis of active plasma cell leukemia.
3. Diagnosis of systemic light chain amyloidosis.
4. MM involving the central nervous system.
5. Has POEMS syndrome.
6. There is spinal cord compression associated with MM.
7. Needs to take concomitant drugs with a strong inhibitory effect or a strong inductioneffect on CYP3A4.
8. Had received plasma exchange therapy within 28 days before the first administration ofthe study drug.
9. Had received the following anti-tumor treatments before the first administration ofthe study drug: monoclonal antibody or cytotoxic drug or radiotherapy within 28 days;immunoregulator, targeted therapy or epigenetic therapy or investigational medicalproduct or invasive investigational medical device or other anti-myeloma therapywithin 28 days or 5 half-lives (whichever is shorter); proteasome inhibitor oranti-tumor traditional Chinese medicine treatment or corticosteroids with a cumulativedose of more than 140 mg prednisone (or equivalent) or a single dose of more than 40mg/day dexamethasone (or equivalent) within 14 days.
10. Had received CAR-T therapy or allogeneic hematopoietic stem cell transplantationtherapy within 6 months before the first administration of the study drug, or have aconcomitant disease of active graft-versus-host disease (GvHD) at screening.
11. Had received autologous hematopoietic stem cell transplantation within 12 weeks beforethe first administration of the study drug.
12. Had undergone major surgery or eye surgery within 28 days before the firstadministration of the study drug.
13. Other malignant diseases within 3 years before the first administration of the studydrug.
14. History of grade ≥3 (muscle paralysis, eyelid disease, glaucoma requiring drugcontrol, tearing eyes), or grade ≥2 any other ocular disease (as judged by NCI-CTCAEversion 5.0) at screening.
15. Has ≥ Grade 3 neuropathy or Grade 2 neuropathy with associated pain.
16. The toxicity caused by the previous anti-tumor treatment did not subside to ≤ grade 1.
17. Has the following hematological test results within 7 days before the firstadministration of the study drug:
18. Hemoglobin <80g/L
19. Platelet count <50×10^9/L
20. Absolute neutrophil count <1.0×10^9/L
21. Has the following blood chemistry test results within 7 days before the firstadministration of the study drug:
22. Estimated creatinine clearance <30mL/min.
23. AST or ALT>3×upper limit of normal (ULN) or serum total bilirubin> 1.5×ULN.
24. Severe or uncontrolled cardiovascular and cerebrovascular diseases requiringtreatment, including:
25. New York Heart Association class>2;
26. Unstable angina pectoris that cannot be controlled by drugs;
27. Myocardial infarction occurred within 6 months before the first administration ofthe study drug;
28. Poorly controlled arrhythmias;
29. 12-lead ECG QTcF>470msec;
30. Left ventricular ejection fraction <40%;
31. Poorly controlled hypertension ;
32. Stroke, cerebrovascular accident, or transient ischemic attack occurred within 6months before the first administration of the study drug.
33. Meets any of the following criteria:
34. Known chronic obstructive pulmonary disease (COPD) and forced expiratory volumein 1 second (FEV1) <50% of predicted normal;
35. Known moderate or severe persistent asthma, or a history of asthma within thepast 2 years, or current uncontrolled asthma of any classification;
36. with interstitial lung disease requiring corticosteroid therapy, drug-inducedinterstitial lung disease, a history of radiation pneumonitis, orclinicallyactive interstitial lung disease suggested by any current evidence before thefirst administration of the study drug.
37. Has an active bacterial, viral, or fungal infection or needs for intravenousantibiotic administration (IV) within 72 hours before the first administration of thestudy drug.
38. Active or uncontrolled HBV , HCV , HIV positive.
39. Is currently pregnant or breast feeding.
40. Has any active severe mental illness, medical illness, or other symptoms/conditionsthat may affect treatment, compliance, or the ability to provide informed consent, asdetermined by the investigator.