This clinical trial is focused on studying the effects of a new treatment called INCB099280 on certain types of cancer known as solid tumors. These tumors are advanced or have come back after treatment, and the patients have not previously received a type of treatment called immunotherapy. The purpose of the study is to understand how safe and tolerable the treatment is, and to see how well it works in managing these tumors.

Participants in the study will take INCB099280 in the form of a film-coated tablet. The study will test different doses of the medication, specifically 400 mg, 600 mg, and 800 mg, taken twice a day. The treatment period can last up to 24 weeks. During the study, participants will be monitored for any side effects and changes in their condition. Some participants may receive a placebo, which is a tablet that looks like the treatment but does not contain the active medication.

The study aims to gather information on how the treatment affects the tumors, including whether it can shrink them or stop them from growing. It will also look at how long any positive effects last and how the treatment impacts the overall health and survival of the participants. The results will help determine if INCB099280 could be a useful treatment option for people with these types of cancer in the future.