A Phase 3 Randomized Clinical Study of MK-4280A Coformulated Favezelimab MK-4280 plus Pembrolizumab MK-3475 Versus Physician's Choice Chemotherapy in PD-(L)1-Refractory, Relapsed or Refractory Classical Hodgkin Lymphoma (KEYFORM-008).

Inclusion Criteria: - Has histologically confirmed diagnosis of classical Hodgkin lymphoma (cHL) that is 2-fluorodeoxyglucose-avid (FDG-avid). - Has relapsed (defined as disease progression after most recent therapy) or refractory (defined as failed to achieve CR or PR to most recent therapy) cHL and exhausted all available treatment options with known clinical benefit. - Has progressed on treatment with an anti-PD-(L)1 monoclonal antibody (mAb) administered either as monotherapy or in combination with other checkpoint inhibitors or other therapies. - Submits an archival (≤5 years) or newly obtained tumor tissue sample which has not been previously irradiated. Exclusion Criteria: - Diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy or any other form of immunosuppressive therapy. - History of central nervous system (CNS) metastases or active CNS involvement. - Has an active autoimmune disease that has required systemic treatment in past 2 years except replacement therapy. - History of (noninfectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease. - Has an active infection requiring systemic treatment. - History of hemophagocytic lymphohisticytosis. - Has an active seizure disorder that is not well controlled. - Has clinically significant (ie, active) cardiovascular disease. - Received prior systemic anticancer therapy including investigational agents within 4 weeks before randomization. - Received prior radiotherapy within 2 weeks of start of study intervention or radiation related toxicities requiring corticosteroids. - Has not adequately recovered from major surgical procedure. - Known additional malignancy that is progressing or has required active treatment within the past 3 years. - History of human immunodeficiency virus (HIV). - Has had an allogeneic hematopoietic stem cell or solid organ transplantation within the last 5 years.