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

The goal of this clinical trial is to learn if the combination of sacituzumab govetican (SG) and atezolizumab/durvalumab is effective in controlling cancer tumor growth in adults with extensive stage small cell lung cancer. These drugs are FDA approved individually in different cancers. This combination is evaluated in breast cancer and showed promising combination. The effectiveness of this treatment combination will be measured by changes in tumor size and appearance of new tumors. Participants in the trial will: * receive treatment SG and immunotherapy every 21 days for up to 2 years or until it is no longer works for the patient. * CT scans at 6weeks for first 6 cycles and then every 9-12 weeks and MRI brain every 12 weeks. * provide tissue (optional) and blood for additional testing (learn about the cancer).