Final results of a phase 2, open-label study of indisulam, idarubicin, and cytarabine in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome

BACKGROUND: Indisulam possesses anticancer properties through down-regulation of various cell-cycle checkpoint molecules, thereby blocking the phosphorylation of retinoblastoma protein and inducing p53 and p21. Indisulam exhibits synergy with nucleoside analogs and topoisomerase inhibitors. METHODS: The authors designed a phase 2 study of indisulam in combination with idarubicin and cytarabine in patients who had relapsed/refractory acute myeloid leukemia AML and high-risk myelodysplastic syndrome. In stage 1, patients received intravenous indisulam at 400 mg/m² on days 1 and 8 of a 28-day cycle. If they had no response, then patients received same dose schedule of indisulam followed by intravenous idarubicin 8 mg/m² daily for 3 days and cytarabine 1.0 g/m² over 24 hours daily on days 9 through 12 (for those aged < 60 years) or days 9 through 11 (for those aged > 60 years) of a 28-day cycle. Primary endpoints included the overall response rate, and secondary objectives included overall survival. RESULTS: Forty patients were enrolled. Of the 37 evaluable patients, 31 received indisulam with chemotherapy. Of these, 11 (35%) responded for a median duration of 5.3 months. The estimated 1-year overall survival rate was 51% for responders compared with 8 % for nonresponders (P <.001). The most common grade ≥3 nonhematologic toxicities were electrolyte abnormalities (50%) and febrile neutropenia (28%). CONCLUSIONS: The combination of indisulam with idarubicin and cytarabine yielded a 35% response rate in heavily pretreated patients with AML. With emerging data identifying the expression of DCAF15 (DDB1 and CUL4-associated factor 15) as a potential biomarker for activity, the combination of indisulam with idarubicin and cytarabine should be studied in a biomarker-driven trial or in patients who have splicing factor mutations. Cancer 2018;124:2758-65.