Effect of olutasidenib (FT-2102) on complete remissions in patients with relapsed/refractory (R/R) mIDH1 acute myeloid leukemia (AML): Results from a planned interim analysis of a phase 2 clinical trial.

7006 Background: Olutasidenib, a potent, selective, oral, small molecule inhibitor of mutant IDH1 (m IDH1), has exhibited favorable tolerability and clinical activity in high-risk AML patients (pts) in a phase 1 trial (Watts, Blood 2019). Here, we present interim analysis results of a phase 2 trial (NCT02719574) in R/R m IDH1 AML pts receiving olutasidenib monotherapy 150 mg twice daily. Methods: The efficacy evaluable (EE) set comprised m IDH1R132X pts whose first dose was ≥180 days before the data cut-off (18-JUN-20). The primary endpoint was CR+CRh (complete remission [CR] or CR with partial hematologic recovery [CRh] according to modified IWG 2003 criteria) rate. CRh was defined as bone marrow blasts <5%, absolute neutrophil count >0.5×109/L, and platelet count >50×109/L. Overall response rate (ORR) comprised CR+CRh+CR with incomplete recovery (CRi) + morphologic leukemia-free state (MLFS) + partial response (PR). Duration of treatment (DOT), duration of response (DOR), and overall survival (OS) were estimated using Kaplan-Meier methodology. Results: This clinical trial met its pre-specified early enrollment-stopping criteria for efficacy. A total of 153 pts with R/R AML received olutasidenib; median DOT, 5.5 mo (95% CI: 4.4, 8.7). 43 pts (28%) remain on treatment and 110 (72%) discontinued, most commonly due to: disease progression, 31%; AEs, 14%; death, 10%; and transplant, 8%. For the EE set (123 pts), the median age was 71 y (range: 32‒87) with a median number of prior therapies of 2 (1‒7). The CR+CRh rate was 33% including 30% of pts in CR (Table). Median duration of CR+CRh was not reached (NR) and 13.8 mo in a sensitivity analysis when HSCT or relapse was deemed end of response. ORR was 46% and median duration of ORR was 11.7 mo. Of responders who were transfusion-dependent at baseline, 56-day platelet transfusion independence (TI) and RBC TI were gained by 100% and 83%, respectively, of pts who achieved CR+CRh, and by 56% and 50% who did not. Median OS was 10.5 mo (EE set). In CR+CRh responders, median OS was NR and the estimated 18-mo OS was 87%. TEAEs in ≥25% of pts were nausea, 38%; constipation, 25%; leukocytosis, 25%. Grade 3/4 all-causality TEAEs in >10% of pts were febrile neutropenia, 20%; anemia, 19%; thrombocytopenia, 16%; neutropenia, 13%. Investigator-assessed IDH1 differentiation syndrome (any grade) was observed in 21 pts (14%); most cases resolved with treatment management; one case was fatal; 19 pts had concomitant leukocytosis. Conclusions: Olutasidenib was well tolerated and induced durable CR in a subset of high-risk R/R m IDH1 AML pts. TI was achieved in all response groups. Clinical benefit, per DOR and OS, extended beyond CR+CRh responders. Clinical trial information: NCT02719574. [Table: see text]