A Study of Valemetostat in Combination With Atezolizumab in People With Lung Cancer

This study is testing whether combining valemetostat — a drug that targets a protein that regulates gene activity in cancer cells — with atezolizumab (an immunotherapy drug) after initial chemotherapy can help keep extensive-stage small cell lung cancer from returning or progressing. **You may be eligible if...** - You are 18 or older - You have been diagnosed with extensive-stage small cell lung cancer (cancer that has spread beyond one lung) - Your cancer showed stable disease, partial response, or complete response after 4 cycles of initial chemotherapy (platinum-based) combined with atezolizumab - You are in generally good health (ECOG status 0 or 1) - Your blood counts, liver, and kidney function are adequate - You can start the study treatment within 4 weeks of completing your 4th chemotherapy cycle **You may NOT be eligible if...** - You have a life expectancy of less than 12 weeks - Your cancer progressed during initial chemotherapy - You have significant autoimmune disease, serious active infections, or uncontrolled medical problems Talk to your doctor to see if this trial is right for you.