Inclusion Criteria - Participants must have histologically or cytologically documented relapsed/refractory small cell lung cancer (R/R-SCLC). - Participants must have received at least 1 platinum-based chemotherapy regimen as per locally approved drug labels and institutional guidelines. - In countries where standard of care first line systemic treatment includes platinum containing chemotherapy in combination with anti-PD-(L)1 therapy, it is required that participants have progressed on, are ineligible for or not have access to an anti-PD- (L)1 therapy. Exclusion Criteria - Participants must not have any untreated CNS metastases. - Participants must not have an active, known or suspected autoimmune disease. - Participants must not have had a prior organ or tissue allograft. - Other protocol-defined Inclusion/Exclusion criteria apply.