A Clinical Study of MK-1045 in People With Non-Hodgkin Lymphoma (MK-1045-008)

Inclusion Criteria:

The main inclusion criteria include but are not limited to the following:

* Has disease that has relapsed (disease progression after remission) or is refractory (failure to achieve complete or partial response) to at least 2 prior systemic lines of therapy.
* Has a histologically confirmed diagnosis of follicular lymphoma (FL) or diffuse large B-cell lymphoma (DLBCL).
* DLBCL participants only: has progressed after or is ineligible for transplant and chimeric antigen receptor T (cell) (CAR-T) therapy.
* Has provided tumor tissue sample (archival or newly obtained, if performed per standard of care).
* Has documented retained expression of cluster of differentiation 19 (CD19) in tumor tissue obtained by biopsy after disease progression on CD19-targeting therapy, if experienced disease progression after prior CD19-targeting therapy.
* Has well-controlled human immunodeficiency virus (HIV) on antiretroviral therapy if has a history of HIV infection.
* Has undetectable hepatitis B virus (HBV) viral load and received and will continue to receive HBV antiviral therapy if hepatitis B surface antigen (HBsAg)-positive.
* Has undetectable hepatitis C virus (HCV) viral load and received HCV antiviral therapy if has a history of HCV infection.
* Has radiographically measurable disease per Lugano Response Criteria.

Exclusion Criteria:

The main exclusion criteria include but are not limited to the following:

* Has received a solid organ transplant.
* Had or has clinically relevant central nervous system (CNS) diseases.
* Has a history of serious cardiovascular or cerebrovascular diseases.
* Had prior allogenic stem cell transplantation with acute graft-versus-host-disease (GVHD); has ongoing evidence of chronic GVHD manifesting as skin involvement, diarrhea, or increased serum bilirubin; or requires systemic immunosuppression for GVHD.
* Is HIV-infected with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease.
* Has received a live or live-attenuated vaccine within 30 days of randomization.
* Has received prior CAR-T therapy within 3 months before the first dose of the study intervention.
* Has a known additional malignancy that is progressing or required active treatment within the past 2 years.
* Has known active CNS lymphoma or involvement.
* Has active autoimmune disease that required systemic treatment in the past 2 years.
* Has active infection requiring systemic therapy.
* Has a history of severe bleeding disorders.
* Has not recovered from major surgery or has ongoing surgical complications.
* Has diagnosis of primary mediastinal B-cell lymphoma.