A Phase 1b Study of Midostaurin (PKC412) in Combination with Daunorubicin and Cytarabine Induction and High-Dose Cytarabine Consolidation in Patients Under Age 61 with Newly Diagnosed De Novo Acute Myeloid Leukemia: Overall Survival of Patients Whose Blasts Have FLT3 Mutations Is Similar to Those with Wild-Type FLT3.
Authors: Stone Richard M , Fischer Thomas , Paquette Ronald , Schiller Gary , Schiffer Charles A. , Ehninger Gerhard , Cortes Jorge , Kantarjian Hagop M. , DeAngelo Daniel J. , Huntsman-Labed Alice , Dutreix Catherine , Rai Sumita , Giles Frank 
Published: October 2019

Abstract
Abstract 634
FLT3, a transmembrane receptor tyrosine kinase constitutively activated via mutation in blasts of patients (pts) with AML, is an important therapeutic target. Blasts from approximately 25% of pts have a length or internal tandem duplication (ITD) mutation in the juxtamembrane region or tyrosine kinase domain (TKD1) of FLT3, which is associated with reduced disease-free survival and overall survival (OS), particularly in pts with normal cytogenetics. Blasts from 5–10% of pts have a point mutation (typically D835Y) in the tyrosine kinase domain (TKD); the effect of this mutation on prognosis is uncertain. Midostaurin (PKC412) is a multi-targeted kinase inhibitor with demonstrated clinical activity in FLT3-mutant (FLT3–mut) and FLT3-wild-type (FLT3–wt) AML (peripheral blood blast reduction in 70% and 30% of pts, respectively) but rarely produces complete remissions). Preclinical studies demonstrated synergy between FLT3 inhibitors and chemotherapy. We conducted a Phase 1b trial to investigate the feasibility of administering daunorubicin (60 mg/m2 IV, days 1–3) and cytarabine (100 mg/m2 IVCI, days 1–7) induction and high-dose cytarabine post-remission therapy (3 gm/m2 over 3h every 12h, days 1, 3, and 5 for 3 cycles) plus oral midostaurin at 100 mg or 50 mg each twice daily on days 8–21 (sequentially) or days 1–7, 15–21 (concomitantly) with all chemo cycles in newly diagnosed pts under age 61 with de novo AML. Whereas 100 mg of midostaurin plus induction chemotherapy was poorly tolerated due to nausea and vomiting, the 40 pts who received 50 mg of midostaurin orally twice daily ( 20 each on the sequential and concomitant schedules; 27 FLT3–wt; 13 FLT3–mut [9 with an ITD]), tolerated the combination well. Median midostaurin exposure was 133 days (range 21–975) for the FLT3–mut pts and 90 days (range 7–1016) for FLT3–wt pts. Maintenance therapy with midostaurin was allowed with investigator discretion and was received by 5 pts (3 FLT3–mut, 2 FLT–wt). The median ages for the FLT3–wt and FLT3–mut pts were 50 years (range 25–60) and 46 years (range 20–65), respectively. 77% of the FLT3–mut pts displayed normal, 15% adverse and 8% other intermediate cytogenetics compared with 18.5%, 26%, and 26%, respectively, for FLT3-wt (also 18.5% favorable; 11% unknown). Complete response occurred in 32/40 (80%) of all pts (20/27 [74%] of FLT3–wt patients, 12/13 [92%] of FLT3–mut pts). Patients were censored at the last date they were known to be alive with a median post treatment follow-up for FLT3-mut pts of 1059 days and 1086 days for FLT3-wt. Even accounting for their differing cytogenetics and ages, the OS of the FLT3–mut subgroup was expected to be inferior to that of the FLT3–wt subgroup. However, we report that the 1 and 2 year OS for the pts with FLT3–mut AML was 85% and 62%, respectively, and was comparable to that of the FLT3–wt subgroup (81% and 59%, respectively). Although based on small numbers and not stratified for type of FLT3 mutation (TKD, ITD, ITD length, location, or allelic ratio), these long-term results suggest that combination therapy with a FLT3 inhibitor and chemotherapy might be effective enough to obviate the perceived need for allogeneic stem cell transplantation for FLT3–mut AML pts in first complete remission. Moreover, these data support the rationale for the ongoing international phase 3 study of induction, post-remission intensification, and maintenance with midostaurin (50 mg po bid) or placebo.

Disclosures:
Stone: Novartis: Research Funding, ad hoc consultancy; Cephalon: ad hoc consultancy. Off Label Use: midostaurin with chemothereapy for AML. Paquette:Novartis: Honoraria, Research Funding, Speakers Bureau. Schiller:Novartis: Research Funding, Speakers Bureau; Millenium: Research Funding, Speakers Bureau; Genzyme: Research Funding; Vion: Research Funding; Centocor: Research Funding; Eli Lilly: Research Funding; Celgene: Research Funding. Schiffer:Novartis: Consultancy, Research Funding; Genzyme: Consultancy. Ehninger:Novartis: Honoraria, Research Funding. Cortes:Novartis: Research Funding; Bristol-Myers Squibb: Research Funding; Wyeth: Research Funding. Kantarjian:Novartis: Research Funding. DeAngelo:Bristol-Myers Squibb: Speakers Bureau; Celgene: Speakers Bureau; Enzon: Speakers Bureau; Novartis: Speakers Bureau. Huntsman-Labed:Novartis: Employment, Equity Ownership. Dutreix:Novartis: Employment, Equity Ownership. Rai:Novartis: Employment, Equity Ownership. Giles:Novartis: Research Funding; Merck: Research Funding; Bristol-Myers Squibb: Research Funding; Vion: Research Funding.