Study to Evaluate the Safety and Efficacy of a Combination of Favezelimab (MK-4280) and Pembrolizumab (MK-3475) in Participants With Hematologic Malignancies (MK-4280-003)

This study will evaluate the safety and efficacy of favezelimab (MK-4280) in combination with pembrolizumab (MK-3475) using a non-randomized study design in participants with the following hematological malignancies: * classical Hodgkin lymphoma (cHL) * diffuse large B-cell lymphoma (DLBCL) * indolent non-Hodgkin lymphoma (iNHL) This study will also evaluate the safety and efficacy of pembrolizumab or favezelimab administered as monotherapy in participants with cHL using a 1:1 randomized study design. The study will have 2 phases: a safety lead-in and an efficacy expansion phase. The recommended Phase 2 dose (RP2D) will be determined in the safety lead-in phase by evaluating dose-limiting toxicities. There is no primary hypothesis for this study.