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 at the DNA or protein level
             in the participant's tumor tissue

          -  Measurable disease

          -  ECOG performance status <= 1 or 2

          -  Adequate organ function

          -  Able to swallow and retain orally administered study treatment

          -  Able to comply with contraceptive/barrier requirements

        Exclusion Criteria:

          -  Known symptomatic brain metastases that are not neurologically stable for 3 months

          -  Known primary CNS malignancy

          -  Current active liver or biliary disease

          -  Active inflammatory gastrointestinal disease, chronic diarrhea, known diverticular
             disease or previous gastric resection or lap band surgery

          -  Impairment of gastrointestinal (GI) function or GI disease that may significantly
             alter the absorption of IDE397

          -  Active, uncontrolled infection including hepatitis B virus, hepatitis C virus, human
             immunodeficiency virus, or acquired immunodeficiency syndrome related illness

          -  Baseline 12 lead ECG that demonstrates clinically relevant abnormalities

          -  Clinically significant cardiac events 6 months before study entry

          -  Uncontrolled hypertension despite optimal medical therapy

          -  Previous treatment with a MAT2A inhibitor and / or PRMT inhibitor

          -  Major surgery within 4 weeks prior to C1D1

          -  Radiation therapy within 4 weeks prior to C1D1

          -  Systemic anti-cancer therapy (non-monoclonal antibody) within 4 weeks prior to study
             entry or within 28 days prior to study entry for an antibody based agent(s) or 5
             half-lives (whichever is shorter)

          -  Have received radioimmunotherapy less than 6 weeks before the first dose of IDE397

          -  Have received treatment with a therapeutic antibody less than 4 weeks before the first
             dose of IDE397

          -  Have received treatment with an investigational small molecule less than 2 weeks
             before the first dose of IDE397

          -  Prior irradiation to >25% of the bone marrow

          -  Current use or anticipated need for food or drugs that are known strong CYP3A4/5
             inhibitors

          -  Current use or anticipated need for food or drugs that are known strong CYP3A4/5
             inducers

          -  Received an investigational product within 28 days prior to first dose of IDE-397 or 5
             half-lives (whichever is shorter)

          -  Exposure to more than 4 investigational medicinal products within 12 months prior to
             C1D1

          -  Known or suspected hypersensitivity to IDE397/excipients or components