Phase IIB trial of oral midostaurin (PKC412), the FMS-like tyrosine kinase 3 receptor (FLT3) and multi-targeted kinase inhibitor, in patients with acute myeloid leukemia and high-risk myelodysplastic syndrome with either wild-type or mutated FLT3

Purpose: Mutations leading to constitutive activation of the FMS-like tyrosine kinase 3 receptor (FLT3) occur in blasts of 30% of patients with acute myeloid leukemia (AML). Midostaurin (PKC412; N-benzoylstaurosporin) is a multitargeted tyrosine kinase inhibitor, with demonstrated activity in patients with AML/myelodysplastic syndrome (MDS) with FLT3 mutations. Patients and Methods: Ninety-five patients with AML or MDS with either wild-type (n = 60) or mutated (n = 35) FLT3 were randomly assigned to receive oral midostaurin at 50 or 100 mg twice daily. The drug was discontinued in the absence of response at 2 months, disease progression, or unacceptable toxicity. Response was defined as complete response, partial response (PR), hematologic improvement, or reduction in peripheral blood or bone marrow blasts by ≥ 50% (BR). Results: The rate of BR for the population in whom efficacy could be assessed (n = 92) was 71% in patients with FLT3-mutant and 42% in patients with FLT3 wild-type. One PR occurred in a patient with FLT3-mutant receiving the 100-mg dose regimen. Both doses were well-tolerated; there were no differences in toxicity or response rate according to the dose of midostaurin. Conclusion: These results suggest that midostaurin has hematologic activity in both patients with FLT3-mutant and wild-type. The degree of clinical activity observed supports additional studies that combine midostaurin and other agents such as chemotherapy especially in FLT3-mutant AML.