Study of IDE397 in Participants With Solid Tumors Harboring MTAP Deletion

Inclusion Criteria: * Participant must be at least 18 years of age * Advanced or metastatic solid tumor that has progressed on at least one prior line of treatment or is intolerant to additional effective standard therapy * Have evidence of homozygous loss of MTAP or MTAP deletion * Willing to undergo paired fresh biopsy (pre- and post-treatment) procedure. Exceptions may be made for feasibility and safety concerns * Measurable disease * ECOG performance status \<= 1 * Adequate organ function * Able to swallow and retain orally administered study treatment * Recovery from acute effects of prior therapy * Able to comply with contraceptive/barrier requirements Exclusion Criteria: * Known symptomatic brain metastases * Known primary CNS malignancy * Current active liver or biliary disease * Impairment of gastrointestinal (GI) function * Active uncontrolled infection * Clinically significant cardiac abnormalities * Active second malignancy or history of another malignancy in the past 2 years * Previous treatment with a MAT2A inhibitor and / or PRMT inhibitor or sacituzumab govitecan * Systemic anti-cancer therapy, therapeutic antibody treatment, or major surgery within 4 weeks prior to study entry * Current radiation-related toxicity or radiation therapy within 2 weeks prior to study entry * Small molecule anti-cancer treatment within 2 weeks prior to study entry * Prior irradiation to \>25% of the bone marrow * Current use or anticipated need for food or drugs that are known strong CYP3A4/5 inhibitors or inducers * Require concomitant use of proton pump inhibitor * Currently receiving another investigational study drug. * Known or suspected hypersensitivity to IDE397/excipients or components