Key Inclusion Criteria:

          1. Histologically confirmed diagnosis of relapsed or refractory cHL

          2. Relapsed cHL (disease progression after PR or CR to the most recent therapy) or
             refractory cHL (failure to achieve PR or CR to most recent therapy). Participants will
             be allocated to one of two cohorts based on the following criteria:

             Cohort 1: Relapsed or refractory to prior autologous hematopoietic stem cell
             transplant (HSCT) and brentuximab vedotin

               1. Has failed to achieve a response or progressed after autologous HSCT and failed
                  to achieve a response or progressed after brentuximab vedotin

               2. Is not a candidate for additional autologous or allogeneic HSCT

             Cohort 2: Relapsed or refractory to salvage chemotherapy, including brentuximab
             vedotin, and has not received prior autologous or allogeneic HSCT

               1. Is not a candidate for autologous or allogeneic HSCT due to disease refractory to
                  salvage chemotherapy

               2. Has received at least 2 prior systemic chemotherapy regimens for cHL and failed
                  to achieve a response or progressed after brentuximab vedotin

          3. Measurable disease defined as ≥ 1 2-[18F] fluoro-2-deoxy-D-glucose (FDG)-avid nodal
             lesion that is > 1.5 cm in the longest diameter, or ≥ 1 FDG-avid extra-nodal lesion
             (eg, hepatic nodules) that is > 1 cm in the longest diameter

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

        Key Exclusion Criteria:

          1. Nodular lymphocyte-predominant Hodgkin lymphoma or gray zone lymphoma

          2. Prior allogeneic hematopoietic stem cell transplantation

          3. Prior therapy targeting PD-1 , PD-L1,PD-L2, or CTLA-4 (cytotoxic
             T-lymphocyte-associated protein 4) pathways

          4. Active autoimmune disease or history of autoimmune disease that may relapse

        NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.