Inclusion Criteria:

          -  Eastern Cooperative Oncology Group (ECOG) performance status of =< 2.

          -  IDH1-R132 mutated disease status as assessed by local laboratory. 2HG-producing IDH1
             variants outside of R132 (i.e. R100) may be eligible after discussion with the
             principal investigator (PI).

          -  Relapsed/refractory AML, or treatment-naive patients with AML who are not eligible for
             standard induction chemotherapy. Patients with high-risk myelodysplastic syndrome
             (MDS) or myeloproliferative neoplasm (MPN) (defined as >= 10% bone marrow blasts, or
             intermediate or high risk by International Prostate Symptom Score [IPSS], Revised
             [R]-IPSS or Dynamic [D]-IPSS) may also be eligible after discussion with the PI

          -  Direct bilirubin =< 2 x upper limit of normal (ULN) unless deemed to be related to
             underlying leukemia.

          -  Alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) =< 3 x ULN
             unless deemed to be related to underlying leukemia.

          -  Creatinine clearance >= 30 ml/min based on the Cockcroft-Gault equation.

          -  Willing and able to provide informed consent.

          -  In the absence of rapidly proliferative disease, the interval from prior treatment to
             time of initiation will be at least 7 days for cytotoxic or non-cytotoxic
             (immunotherapy) agents.

          -  Male subjects must agree to refrain from unprotected sex and sperm donation from
             initial study drug administration until 90 days after the last dose of study drug.

        Exclusion Criteria:

          -  Patients with known allergy or hypersensitivity to ivosidenib or venetoclax.

          -  Patients who have previously received either ivosidenib or venetoclax.

          -  Patients with any concurrent uncontrolled clinically significant medical condition
             including infection, laboratory abnormality, or psychiatric illness, which could place
             the patient at unacceptable risk of study treatment

          -  The use of other chemotherapeutic agents or anti-leukemic agents is not permitted
             during study with the following exceptions (1) intrathecal chemotherapy for
             prophylactic use or for controlled central nervous system (CNS) leukemia. (2) use of
             hydroxyurea and/or one dose of cytarabine (up to 2 g/m^2) for patients with rapidly
             proliferative disease is allowed before the start of study therapy and for the first
             four weeks on therapy.

          -  Patients receiving concomitant treatment with strong CYP3A4 inhibitors within 3 days
             of start of study therapy (including posaconazole and voriconazole).

          -  Patients receiving concomitant strong CYP3A inducers (avasimibe, carbamazepine,
             phenytoin, rifampin, rifabutin, St. John's wort) within 3 days of start of study
             therapy.

          -  Patients with active graft-versus-host-disease (GVHD) status post stem cell transplant
             (patients without active GVHD on chronic suppressive immunosuppression and/or
             phototherapy for chronic skin GVHD are permitted after discussion with the PI).

          -  Patients with any severe gastrointestinal or metabolic condition which could interfere
             with the absorption of oral study medications.

          -  Patients with a concurrent active malignancy under treatment.

          -  Corrected QT (QTc) interval using Fridericia's formula (QTcF) >= 450 msec. Bundle
             branch block and prolonged QTc interval are permitted after discussion with the PI.

          -  Known active hepatitis B (HBV) or hepatitis C (HCV) infection or known human
             immunodeficiency virus (HIV) infection.

          -  Subject has a white blood cell count > 25 x 10^9/L. (Note: Hydroxyurea is permitted to
             meet this criterion.)

          -  Nursing women, women of childbearing potential (WOCBP) with positive urine pregnancy
             test, or women of childbearing potential who are not willing to maintain adequate
             contraception.

               -  Appropriate highly effective method(s) of contraception include oral or
                  injectable hormonal birth control, intrauterine device (IUD), and double barrier
                  methods (for example a condom in combination with a spermicide).