A Study to Compare the Efficacy and Safety of BMS-986489 (BMS-986012+ Nivolumab Fixed Dose Combination) in Combination With Carboplatin Plus Etoposide to That of Atezolizumab With Carboplatin Plus Etoposide as First-Line Therapy in Participants With Extensive-Stage Small Cell Lung Cancer (TIGOS).

Inclusion Criteria

• Participants must have diagnosis of Extensive-Stage Small Cell Lung Cancer (ES-SCLC).

• Participants must be Healthy enough to do their normal activities with little or no help based on the ECOG performance scale.

• Participants must have at least one tumor that can be measured using special imaging techniques like a CT scan or MRI at a site other than the brain and nervous system

Exclusion Criteria

• Participants have already received certain types of treatment for extensive stage small cell lung cancer

• Participants have certain health conditions, like spread of small cell lung cancer to the brain that are causing symptoms, certain lung diseases, heart diseases, infections, autoimmune diseases, other cancers, or a type of nerve damage called peripheral sensory neuropathy

• Other protocol-defined Inclusion/Exclusion criteria apply.