A Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Efficacy Study of MBS303 in B-Cell NHL

Inclusion Criteria:

1. Able and willing to provide written informed consent and to comply with the studyprotocol.

2. Adult patients, ≥18 years of age;

3. CD20+ B-cell Non-Hodgkin Lymphoma who have relapsed after or failed to respond to atleast one prior treatment regimen with an anti-CD20 monoclonal antibody and for whomthere is no available therapy expected to improve survival;

4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1;

5. Life expectancy ≥3 months;

6. Measurable disease, defined as at lease one bi-dimensionally measurable nodallesion, defined as >1.5 cm in its longest dimension, or at least onebi-dimensionally measureable extranodal lesion, defined as >1.0 cm in its longestdimension

7. Adequate hematologic, hepatic, and renal function.

Exclusion Criteria:

1. Chronic lymphoblastic leukemia, Burkitt lymphoma or lymphoplasmacytic lymphom;

2. History of central nervous system (CNS) lymphoma or other CNS disease;

3. Participants with known active infection, including bacterial, viral, parasite,mycobacterial, or other infections (excluding nail bed fungal infections);

4. Surgery, chemotherapy, targeted therapy, immunotherapy, radiation therapy, tumorembolization, or other antitumor therapy within 28 days prior to the first MBS303;

5. Active or suspected autoimmune diseases;

6. Known severe allergic reaction or/and infusion reaction to monoclonal antibody;

7. Evidence of significant, uncontrolled concomitant disease;

8. Major surgery within 28 days prior to the first MBS303 administration or expected toundergo major surgery during the study treatment;

9. History of another invasive malignant tumors in past 3 years;

10. Participant with history of confirmed progressive multifocal leukoencephalopathy (PML);

11. Severe hemorrhagic diseases such as hemophilia A, hemophilia B, vascular hemophilia,or spontaneous bleeding requiring blood transfusion or other medical intervention;

12. Infection with human immunodeficiency virus (HIV), hepatitis B or hepatitis C (including HBsAg, HBcAb positive with abnormal HBV DNA or HCV RNA);

13. Pregnant or lactating women; Females of childbearing potential (FCBP) must agree touse two reliable forms of contraception simultaneously or to practice completeabstinence from heterosexual contact during the following time periods related tothis study: 1) while participating in the study; 2) for at least 12 months afterdiscontinuation of all study treatments.