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 oftreatment 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

• Previous treatment with a MAT2A inhibitor and / or PRMT inhibitor or sacituzumabgovitecan

• Systemic anti-cancer therapy or major surgery within 4 weeks prior to study entry

• Radiation therapy 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 CYP3A4/5inhibitors or inducers

• Currently receiving another investigational study drug.

• Known or suspected hypersensitivity to IDE397/excipients or components