A Phase I/II Trial of Combination of Midostaurin (PKC412) and 5-Azacytidine (5-AZA) for the Treatment of Patients with Refractory or Relapsed (R/R) Acute Myeloid Leukemia (AML) and Myelodysplastic Syndrome (MDS)

Midostaurin (PKC412) is a potent orally bioavailable FLT3 inhibitor with activity in acute myeloid leukemia (AML). 5-azacytidine (5-AZA) is a hypomethylating agent that plays an important role in the treatment of AML and MDS. We hypothesized that adding midostaurin to 5-AZA may improve the response rate with limited toxicity profile.

Patients ≥18 years with MDS, chronic myelomonocytic leukemia (CMML) or AML, who failed prior therapies with performance status ≤ 2, adequate liver (bilirubin ≤ 2 × ULN, ALT ≤ 2.5× ULN) and renal (creatinine ≤2× ULN) functions were eligible. Patients were included in phase I regardless of FLT3 mutation status; only FLT3 mutated patients were included in phase II. Patients received 5-AZA 75 mg/m² subcutaneously or intravenously for 7 days of each cycle (Days 1–7) and midostaurin at 25 mg (cohort 1) and 50 mg (cohort 2; target dose) orally twice daily for 14 days (Days 8–21) per cycle. Patients were planned to receive up to 12 cycles if benefit from treatment. Supportive care was standard. The study was approved by institutional IRB and conducted in accordance of the declaration of Helsinki.

20 patients have been enrolled: 13 included in phase I (6 in cohort 1 and 7 in cohort 2) and 6 patients in phase II. One patient in cohort 1 was inevaluable for DLT (withdrawal before completing cycle #1). One patient in cohort 2 received midostaurin dose as per cohort 1 dose by patient error. Patients' characteristics and responses are summarized in table 1. Overall response rate (ORR) in phase I was 3/13 (21%) (2 CRi and 1 patient decreased BM blasts from 27% to 7% after 2 cycles and went to transplant). ORR in phase II was 2/6 (33%) (1 patient with AML achieved CRi, 1 patient with CMML {received prior sorafenib} achieved CR). In addition, 1 AML patient had bone marrow blasts improved form 77% to 10% after 1 cycle, completed 3 cycles of therapy and then refused further treatment, and 1 AML patient had bone marrow blasts improve from 34% to 7 % and was continued on treatment). A total of nine patients with FLT3-ITD mutations enrolled in the trial: four patients in phase I with a median allelic ratio of 0.44 (range, 0.219–0.726); 1/4 (25%) achieved CRi, 2 of the non-responders had received prior FLT3 inhibitors (1 had developed FLT3-D835). Five patients in phase II had FLT3-ITD (median allelic ratio 0.06, range 0.014–0.279; one with concomitant D835 mutation) and one patient had FLT3-D835 mutation only (allelic ratio 0.238). 4/6 patients in phase II had failed prior FLT 3 inhibitors. In total, the ORR among patients with FLT3-ITD mutations was 3/9 (33%). All toxicities were grade 1 and 2 with no difference between the 2 dose schedules of midostaurin. No DLT or deaths were identified.

The combination of midostaurin/5-AZA is safe and well tolerated at the intended doses (midostaurin 50 mg PO twice daily). Good ORR in high risk patients with relapsed or primary refractory FLT3-ITD positive AML was observed. Schedule is being amended to allow uninterrupted midostaurin administration. Phase II study continues to enroll patients with FLT3 mutations and updated results will be presented at the meeting.

Off Label Use: 5-azacytidine in AML. Cortes:Novartis: Consultancy, Research Funding; Celgene: Research Funding; Ambit: Research Funding.