A Phase 2 Study Evaluating Olutasidenib in Combination With Hypomethylating Agents in Patients With IDH1-mutated Higher-risk Myelodysplastic Syndromes, Chronic Myelomonocytic Leukemia, or Advanced Myeloproliferative Neoplasm

To learn if olutasidenib, when combined with a drug called a hypomethylating agent (HMA) can help to control MDS, CMML, and/or MPN. The safety of the drug combination will also be studied.

Inclusion Criteria: 1. Pathologically proven higher-risk MDS/CMML or advanced MPN 1. MDS participants must have International Prognostic Scoring System (IPSS) intermediate-2- or high-risk disease or Revised IPSS (IPSS-R) score \>= 3.5 or Molecular IPSS (IPSS-M) moderate high-, high-, or very high-risk disease or bone marrow blast percentage. 2. CMML patients must have CPSS-Mol int-1, int-2, or high-ris disease (Elena C et al, Blood 2016) 3. Advanced MPN is defined as bone marrow blast percentage \>=/=10%. 4. Participants on the treatment-naive arm must not have received a prior HMA. Agents such as growth factors (e.g. erythropoietin stimulating agents, luspatercept, eltrombopag, granulocyte colony stimulating factors), cyclosporine, and/or hydroxyurea are allowed. 5. Patients on the previously-treated arm must have received a prior HMA and/or ivosidenib. Prior stem cell transplantation in allowed\> 2. Participants must have a documented IDH1 mutation 3. Patients with previously-treated MDS must be ineligible to receive treatment with ivosidenib or have progressed on treatment with ivosidenib. 4. Participants \>=/= 18 years old 5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 (Appendix A) 6. Acceptable liver function 1. Bilirubin \