A Study to Evaluate MK-1045 (CN201) in Participants With Relapsed or Refractory B-Cell Non-Hodgkin Lymphoma (MK-1045-001/CN201-101)

Inclusion/Exclusion Criteria:

Inclusion Criteria

Inclusion Criteria include, but are not limited to:

• Has relapsed or refractory B-cell Non-Hodgkin's lymphoma (B-NHL) with disease history meeting the following World Health Organization (WHO) diagnostic subtypes of B-NHL that are CD19-positive in pathologic Immunohistochemistry test: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL) (Grade I to III), marginal zone lymphoma, lymphoplasmacytic lymphoma, mantle cell lymphoma, small lymphocytic lymphoma, and transformed large B-cell lymphoma (During the dose-escalation phase, participants other than those treated with Chimeric antigen receptor T-cell (CAR-T) who cannot provide proof of pathologic immunohistochemistry CD19 positivity but have previous proof of CD20 positivity may be considered for enrollment after discussion with the sponsor)

• Relapse is defined as the occurrence of progressive disease (PD) after complete response (CR) or partial response (PR) has been achieved after adequate treatment. Note: For DLBCL participants, relapse must occur after participants undergoing at least two lines of therapy; for other participants, they must undergo at least one line of therapy.

• Refractory is defined as a situation that there is no standard of care available or that it is not applicable to use standard of care at this stage, including: Participants who are unresponsive to standard of care (e.g., monotherapy or combination therapy containing anti-CD20 monoclonal antibody) and whose best response to standard therapy is PD or stable disease (SD); Participants who are not eligible for autologous hematopoietic stem cell transplantation (ASCT) and have relapsed PD after receiving ASCT; Participants who have failed on chimeric antigen receptor T cell (CAR-T) immunotherapy, but the first dose of the study intervention must be at least 3 months after discontinuation of CAR-T therapy, and CD19 positive expression is still present in tumor tissue.

• Has at least one evaluable tumor lesion per the Lugano 2014 criteria, i.e., a lymph node lesion > 15 mm in long diameter or an extranodal lesion > 10 mm in long diameter according to computed tomography (CT) cross-sectional imaging or magnetic resonance imaging (MRI)

• Has an Eastern Cooperative Oncology Group (ECOG) performance score of ≤ 2 and an estimated survival time of more than 3 months

• Has essentially normal: bone marrow function; coagulation function; liver function; kidney function; lung function; and heart function

Exclusion Criteria

Exclusion Criteria include, but are not limited to:

• Has any other non-Hodgkin lymphoma (NHL) not listed in inclusion criteria

• Has been treated with anti-CD3/CD19 bispecific antibody (BsAb) prior to first dose of study intervention

• Has received chemotherapy, endocrine therapy, radiotherapy (palliative radiotherapy 2 weeks prior to the first administration of the investigational drug), or biologic therapy, and small molecule targeted agents within 2 weeks prior to the first administration of the investigational drug or within 5 half-lives of the drug, whichever is shorter

• Has received anti-CD20 antibody or anti-CD19 antibody within 4 weeks prior to first use of the investigational drug

• Has received anti-tumor immunotherapy or other unlisted clinical study intervention within 4 weeks prior to the first dose of study intervention, or within 5 half-lives of the drug, whichever is shorter

• Has undergone any major organ surgery (excluding aspiration biopsy) or significant trauma within 4 weeks prior to the first dose of study intervention or those requiring elective surgeries during the study

• Has received systemic corticosteroids (prednisone >10 mg/day or equivalent) or other immunosuppressive agents within 14 days prior to the first dose of the study intervention, excluding the following agents: topical, ocular, intra-articular, intranasal, and inhaled corticosteroids, and short-term, prophylactic use of corticosteroids (e.g. to prevent radio contrast agent induced allergic reactions)

• Has used immunomodulatory agents, including but not limited to thymosin, interleukin-2 (IL-2), interferon (IFN) and anti-tumor Chinese patent drugs or Chinese herbal medicines within 14 days prior to the first dose of study intervention

• Has had a live attenuated vaccines within 4 weeks prior to the first dose of study intervention

• Has a central nervous system (CNS) infiltration

• Has previous or concomitant CNS diseases, including epilepsy, hemorrhagic/ischemic stroke, severe brain injury, dementia, Parkinson's disease, cerebellar disorder, organic cerebellar syndrome, or mental diseases

• Has prior or concomitant malignancies (except cured basal cell or squamous cell carcinoma of the skin, carcinoma in situ of the cervix, prostatic intraepithelial neoplasia, and other tumors that have been clinically cured for 5 years as assessed by the investigator)

• Has uncontrolled active infections currently requiring systemic anti-infective therapy within 3 days prior to first dose

• Has active hepatitis B and/or hepatitis C. Participants who are positive for antibodies to hepatitis C virus (HCV). Participants who are hepatitis B surface antigen (HBsAg) positive are not allowed to enroll in the dose-escalation period; however, those who were hepatitis B surface antigen (HBsAg)-positive but hepatitis B Virus deoxyribonucleic acid (HBV DNA)-negative and adherent to entecavir antiviral therapy and who agreed to regular monthly monitoring of HBV DNA are allowed to enroll in the dose-expansion period

• Has a history of immunodeficiency, including testing positive for human immunodeficiency virus (HIV) antibody

• Has a history of serious cardiovascular and cerebrovascular disease, including but not limited to: severe cardiac rhythm or conduction abnormalities; acute coronary syndrome, congestive heart failure, stroke, or other Grade 3 or higher cardiovascular and cerebrovascular events within 6 months prior to the first dose; ≥ Class II cardiac function as per New York Heart Association (NYHA) functional class or LVEF < 50%; or clinically uncontrollable hypertension

• Has previous or current interstitial lung disease

• Has acute graft-versus-host disease (GVHD) or active chronic GVHD at present

• Has active or history of autoimmune diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, autoimmune thyroid disease, vasculitis, psoriasis, etc.) that may relapse, or participants who are at risks (e.g., organ transplant requiring immunosuppressive therapy). Participants with the following diseases are allowed to be further screened for enrollment: hypothyroidism managed with hormone replacement therapy only, and skin diseases not requiring systemic treatment (such as vitiligo, psoriasis, or alopecia).

• Has received immunotherapy with known Grade 3 or higher immune-related adverse events (irAEs)

• Has non-hematologic adverse reactions from prior anti-tumor therapy have not recovered to Grade ≤ 1 as assessed by National Cancer Institute NCI Common Terminology Criteria for Adverse Events (NCI-CTCAE) Version 5.0 (excluding toxicities such as alopecia that are assessed by the investigator to have no safety risk)