Combination Study of Guadecitabine/ASTX727 and Pembrolizumab

This study is testing a combination of two drugs — guadecitabine (or ASTX727) and pembrolizumab (an immunotherapy) — in patients with advanced solid tumors (cancers that form solid masses, like lung, bowel, or bladder cancer) that have stopped responding to standard treatments. **You may be eligible if...** - You have an advanced solid tumor that no longer responds to standard treatments, or for which no standard treatment is available or appropriate - You may be eligible for a specific part of the study if your tumor previously responded to a checkpoint inhibitor (a type of immunotherapy like pembrolizumab) but later stopped working - You are in generally good enough health to participate **You may NOT be eligible if...** - You have active autoimmune disease that requires treatment - You are on high-dose steroids or other immune-suppressing medications - You have untreated brain metastases (cancer spread to the brain) - You are pregnant or breastfeeding - You have had prior serious reactions to immunotherapy drugs Talk to your doctor to see if this trial is right for you.