Study of Sacituzumab Govitecan Versus Standard of Care in Participants With Previously Treated Extensive Stage Small Cell Lung Cancer

Key Inclusion Criteria: * Histologically confirmed diagnosis of SCLC. * Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1. * Measurable disease by computed tomography (CT) or magnetic resonance imaging (MRI) as assessed by investigator per RECIST v1.1 criteria. * Documentation of radiological disease progression after 1 prior line of platinum-containing chemotherapy (defined as at least 2 cycles of treatment) with or without therapy directed against programmed cell death protein 1 (PD-1) or programmed cell death ligand 1 (PD-L1; PD-1 and PD-L1 are hereafter referred to as PD-(L)1) for ES-SCLC. * Individuals treated with a platinum-based therapy for prior limited stage small cell lung cancer will be counted as 1 prior line of platinum-containing chemotherapy if the disease has progressed within 30 to 180 days from last dose of platinum treatment. * If the investigator believes a participant may benefit from platinum rechallenge it can be considered per investigator discretion and local SOC; however, participants with platinum rechallenge may not participate in the study. * If the investigator believes a participant may benefit from tarlatamab treatment, it can be considered per investigator discretion and local SOC and such participants may participate in the study following tarlatamab treatment. Note: at least 85% of participants included in the study must be pretreated with anti-PD-\[L\]1 therapy. Refer to protocol for country-specific requirements for participants in China. Key Exclusion Criteria: * Chemotherapy-free interval (CTFI) time from the last dose of first-line platinum-containing chemotherapy to the occurrence of progressive disease) \< 30 days (independent of the immunotherapy maintenance). * Received any prior treatment with irinotecan, topotecan, SG, SN-38, exatecan derivatives, and similar agents targeting topoisomerase I. Received lurbinectedin after progression on or after platinum-based chemotherapy. * Have carcinomatous meningitis and/or non-carcinomatous meningitis central nervous system (CNS) metastasis apart from the following noted exceptions. Participants with previously treated brain metastases may participate provided they have stable CNS disease (ie, without evidence of progression) for at least 4 weeks (independent from completion of definitive treatment) prior to randomization and all neurologic symptoms have returned to baseline, have no evidence of new or enlarging brain metastases, and are taking ≤ 10 mg/day of prednisone or its equivalent. Participants with untreated, clinically stable brain metastases will be allowed if they are asymptomatic and the investigator determines there is no immediate CNS-specific treatment required, there is no surrounding edema, and the brain metastases are of 5 mm or less in size and 3 or fewer lesions. Note: Other protocol defined Inclusion/Exclusion criteria may apply.