• Have histologically or cytologically confirmed ES-SCLC (using the AJCC \[American Joint Committee on Cancer\] tumor node metastasis staging system combined with Veterans Administration Lung Study Group \[VALG\]'s two stage classification scheme). For AJCC tumor node metastasis staging system: AJCC 8th edition stage IV (T any, N any, M1a/b/c), or T3\

⁃ 4 for multiple lung nodules or tumor/nodule volume that cannot be encompassed in a tolerable radiotherapy plan.

• Have not had prior systemic therapy for ES-SCLC. However, participants with prior chemoradiotherapy for limited-stage-SCLC must have been treated with curative intent and had a treatment-free interval of at least 6 months after the last chemotherapy, radiotherapy, or chemoradiotherapy before diagnosis of ES-SCLC to be eligible.

• Have at least one measurable lesion as the targeted lesion based on RECIST v1.1. Lesions treated after prior local treatment (radiotherapy, ablation, interventional procedures, etc.) are generally not considered as target lesions. If the lesion with prior local treatment is the only targeted lesion, evidence-based radiology must be provided to demonstrate disease progression (the single bone metastasis or the single central nervous system metastasis should not be considered as a measurable lesion).

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

• Adequate hematologic and organ function as defined in the protocol.