The purpose of this clinical research study to find out if the experimental drug, IDE397, is safe and helpful in those who have any type of cancer that is considered a “solid tumor” (not a blood cancer) that is caused by an error in the tumor DNA associated with the gene, methylthioadenosine phosphorylase (MTAP). The loss of the MTAP gene is an error seen in many different types of cancers. Participants must have loss of the MTAP gene in order to participate in the study.
   
IDE397 is an investigational drug that has not yet been approved by the U.S. Food and Drug Administration (FDA) , for the treatment of people with these tumors. It is currently not “on the market”, or available for patients to receive a prescription for and/or to buy in any country. 
   
In this study, different dose levels of IDE397 will be tested. There will be about 10 dose levels tested (starting at 5 mg). Every time a dose level is found to be safe, a new dose level will be tested in a new group of participants until the most appropriate dose is determined. Participants in the lower dose level may receive IDE397 at the next dose level that is determined to be safe. 
   
The main goals of the study are to determine:
   - To what extent IDE397 is safe and tolerated
   - The highest dose of IDE397 that is safe
   - The effects, good and/or bad, IDE397 has on participants and on their disease
   - How quickly the study drugs are removed from participants bloodstream
   - How the drug works in the body and on the cancer

Study treatment will take places in 21-day cycles. Participants will be asked to come to the doctor’s office/clinic/study site approximately 5 times during the first cycle (including 2 long visits lasting up to 8 hours), and then 1 to 3 times per cycle for the subsequent cycles until they are no longer receiving the study drugs. Participants may receive IDE397 for up to 2 years and may receive IDE397 beyond 2 years if the doctor determines it to be safe and it is approved by the sponsor.