Study of Sacituzumab Govitecan With Atezolizumab/Durvalumab as Maintenance Therapy for Extensive-Stage Small Cell Lung Cancer

Inclusion Criteria: * Participant is willing and able to give informed consent for participation in the trial. * Male or Female aged 18 years or above. * Participants must have a histologically or cytologically confirmed diagnosis of small cell lung cancer (SCLC) and extensive stage at diagnosis or locally advanced disease and unable to receive curative intent radiation. * Participants must have received at least four cycles of platinum plus etoposide and at least 2-3 cycles of atezolizumab/ Durvalumab. * No evidence of progression on restaging CT CAP following 4-6 cycles of Chemo/IO from the last dose of the chemotherapy cycle. * ECOG performance status of 0-2 * Patients must not have active uncontrolled HIV, HBV, and HCV infections. Well-controlled infections on treatment will be allowed to participate in the trial. * Patients with stable and asymptomatic brain metastasis. * Adequate organ function - bone marrow, kidney, and liver. Exclusion Criteria: * Significant renal impairment requiring dialysis or hepatic impairment with end-stage liver disease. * Participants with leptomeningeal disease. * Participants with a recent diagnosis of heart failure and acute coronary disease within 3 months. * Participants who are unable to receive immunotherapy with chemotherapy for induction will be excluded, or those immunotherapy was discontinued to manage immune-related adverse events * Active chronic inflammatory bowel disease (ulcerative colitis, Crohn's disease) or gastrointestinal perforation within 6 months of enrolment. * Patients with prior exposure to anti-PD-1, anti-PD-L1, or anti-PD-L2 agents or with an agent directed to another stimulatory or coinhibitory T-cell receptor (eg, CTLA-4) within 12 months of the study is not allowed.