Abstract
Background
Acute Myeloid Leukemia (AML) and Myelodysplastic Syndrome (MDS) affect primarily elderly pts. Their treatment with aggressive chemotherapy is frequently challenging. Moreover, pts with FLT3 mutations have very poor prognosis. We hypothesized that the combination of midostaurin, a FLT3 inhibitor, and 5-AZA, a hypomethylating agent, may be an effective and safe regimen.
Methods
Both untreated (8) and previously treated (36) pts with AML or MDS were eligible for this study, regardless of FLT3 mutation and prior exposure to FLT3 inhibitors. Pts received 5-AZA 75 mg/mq subcutaneously or intravenously on day 1-7 and midostaurin 25 mg bid (in cohort 1 of phase I) or 50 mg bid (in cohort 2 of Phase I and in Phase II) orally on day 8-21 during the first cycle and continuously thereafter, for 12 cycles of 28 days duration. Cytogenetic risk was defined according to MRC criteria. Differences between categorical variables were compared by the chi2 test. CR duration (CRD) was calculated from the time of CR achievement until relapse and estimated by the Kaplan-Meier method and compared by the log-rank test.
Results
Fourty-four pts were enrolled, 13 included in Phase I and 31 in Phase II. Baseline pts’ characteristics are shown in the Table. Thirty-eight pts (86%) received 50 mg bid of midostaurin, and 6 (14%; Phase I) received 25 mg bid. The median number of administered cycles was 2 (1-9). Grade 3-4 hematological toxicities consisted of 95% neutropenia, 64% anemia and 93% thrombocytopenia. Grade 3-4 non-hematological toxicities consisted of 45% infections, 23% hypokalemia, 16% hyponatremia, 7% reduction in ejection fraction, 7% hyperuricemia, 4% hyperglycemia, 4% nausea/vomiting, 4% QTc prolongation, 4% hyperbilirubinemia, and 4% elevated AST. Eleven pts (25%) achieved a CR, 9 with incomplete platelet recovery (20%), after a median time of 13 (10-16) weeks from treatment start. Five (11%) of these pts relapsed after achieving CR. Two pts (5%) received an allogeneic stem cell transplant while on study, one in CR and one primary refractory (after a blast count drop from 27 to 7%), and they are both still in CR and alive. Among 26 pts with FLT3 ITD and no D835 mutation, 9 (35%) achieved CR/CRp. Six of 18 (33%) pts not previously exposed to FLT3 inhibitors responded. There was no significant correlation of dose with response (24% with 50 mg bid vs 33% with 25 mg bid, p=0.63). After a median follow-up of 15 (3-72) weeks, 20 pts (64%) died, 3 (7%) while on study (2 died of sepsis, 1 of unknown causes with progressive disease). The median CRD was 16 (9-23) months. Factors significantly associated with a longer CRD were male sex (p=0.04), age older than 65 years (0.03) and use of 50 mg bid of midostaurin (p=0.02).
Conclusions
The combination of midostaurin and 5-AZA is safe and well tolerated. Its efficacy is most noticeable among pts with FLT3 mutations. A longer response duration is observed using midostaurin at 50 mg bid dose and in elderly male pts.
Disclosures:
Ravandi: CELGENE: Honoraria; NOVARTIS: Honoraria. Cortes:ARIAD: Consultancy, Research Funding; ASTELLAS: Research Funding; AMBIT: Research Funding; AROG: Research Funding; NOVARTIS: Research Funding.
Dual Mechanism Inhibitor Control and Pharmacological Utility of Drug Resistance FLT3-ITD in Acute Myeloid Leukemia Cells
