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Context: Mutations in isocitrate dehydrogenase 1 (IDH1) occur in ~3% of patients with MDS and are associated with increased transformation to acute myeloid leukemia (AML). IVO is an oral, potent, targeted inhibitor of the mutant IDH1 (mIDH1) enzyme and is FDA-approved for mIDH1 R/R AML and mIDH1 newly diagnosed AML in patients ≥75 years old or with comorbidities precluding the use of intensive induction chemotherapy. In the first-in-human, phase 1 study of IVO in patients with mIDH1 advanced hematologic malignancies (NCT02074839), 12 patients with R/R MDS, with median age 72.5 years (range 52–78), received IVO 500 mg once daily (QD). All patients received prior MDS treatment. Investigator-assessed ORR (CR + PR + marrow CR, per IWG 2006) was 75% (95% CI 43–95), with median duration of response of 21.4 months (95% CI 2.3–NE). Nine (75%) patients were transfusion-independent for ≥56 days during treatment. No dose-limiting toxicities or adverse events leading to treatment discontinuation were reported among patients with MDS. Based on these encouraging data, the FDA granted Breakthrough Therapy Designation to IVO in mIDH1 MDS; the study was amended to enroll additional patients with mIDH1 R/R MDS. Objective: To evaluate safety, tolerability, clinical activity, and pharmacokinetics/pharmacodynamics of IVO in patients with mIDH1 R/R MDS. Design: A sub-study of the single-arm, open-label, phase 1 dose escalation and expansion study of IVO in mIDH1 advanced hematologic malignancies, evaluating patients with R/R MDS. Patients must have R/R disease after prior standard therapy; high disease burden based on cytopenia and/or transfusion dependence at baseline; an Eastern Cooperative Oncology Group performance status score of 0–2; and be amenable to bone marrow aspirate and/or core biopsy at specified study timepoints. Patients with documented AML are not eligible. IVO 500 mg QD orally on days 1–28 of 28-day cycles. Results: Study is open; enrollment of ~23 patients from the US and France planned. Results not yet available. Conclusions: This sub-study will provide additional insights into safety, tolerability, clinical activity, and pharmacokinetics/pharmacodynamics of treatment with IVO in patients with mIDH1 R/R MDS. Funding: Agios; Servier.

Context: IVO is an oral, potent, targeted inhibitor of the mutant IDH1 (mIDH1) enzyme, approved in the US for the treatment of AML with a susceptible IDH1 mutation in adults with newly diagnosed AML ≥75 years of age or having comorbidities precluding intensive induction chemotherapy, and in adults with R/R AML. In a phase 1 dose escalation and expansion study of IVO in mIDH1 advanced hematologic malignancies ( NCT02074839 ), 12 patients with R/R MDS received IVO 500 mg once daily (QD). Median age was 72.5 years (range 52–78). All patients had received prior treatment for MDS, with 3 (25.0%) and 1 (8.3%) having received 2 or ≥3 prior therapies, respectively. Investigator-assessed ORR (CR + PR + marrow CR) per International Working Group 2006 criteria was 75.0% (95% CI 42.8%, 94.5%) with a median duration of 21.4 months (95% CI 2.3, not estimable). Nine patients (75.0%) were transfusion independent for ≥56 days during study treatment. Based on these data, the FDA recently granted a Breakthrough Therapy Designation status for IVO monotherapy in this indication, and the study has been amended to enroll additional mIDH1 R/R MDS patients. Objective: To assess safety, tolerability, clinical activity, pharmacokinetics, and pharmacodynamics of IVO in patients with mIDH1 R/R MDS. Design: This is a sub-study of the phase 1 study of IVO in mIDH1 advanced hematologic malignancies to evaluate patients with mIDH1 R/R MDS. Patients must have R/R disease after treatment with standard agents indicated for MDS and high disease burden based on cytopenia and/or transfusion dependence at baseline. IVO will be administered at a dose of 500 mg QD orally on Days 1–28 of 28-day cycles. Results: The study is open and will enroll ∼23 patients from the US and France; results not yet available. Conclusions: The favorable efficacy and safety of IVO in the small population of patients with mIDH1 R/R MDS in the phase 1 clinical study supports further evaluation in this MDS sub-study. This sub-study will provide additional insights into safety, tolerability, clinical activity, and pharmacokinetics/pharmacodynamics of treatment with IVO in patients with mIDH1 R/R MDS. Funding: Agios.