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Midostaurin (Rydapt) capsules
The US Food and Drug Administration (FDA) has granted approval for the oral, multi-targeted kinase inhibitor midostaurin (Rydapt).
The drug is now approved for the treatment of adults with advanced systemic mastocytosis (SM), including aggressive SM (ASM), SM with associated hematologic neoplasm (SM-AHN), and mast cell leukemia (MCL).
Midostaurin is also approved for use in combination with standard cytarabine and daunorubicin induction, followed by cytarabine consolidation, in adults with newly diagnosed acute myeloid leukemia (AML) who are FLT3 mutation-positive, as detected by an FDA-approved test.
The FDA approved a companion diagnostic, the LeukoStrat CDx FLT3 Mutation Assay, for use with midostaurin to test AML patients for the FLT3 mutation.
Midostaurin is a product of Novartis. The companion diagnostic was developed by Novartis and Invivoscribe Technologies, Inc.
Midostaurin in AML
The FDA’s approval of midostaurin in AML is based on results from the phase 3 RATIFY trial, which were presented at the 2015 ASH Annual Meeting.
In RATIFY, researchers compared midostaurin plus standard chemotherapy to placebo plus standard chemotherapy in 717 adults younger than age 60 who had FLT3-mutated AML.
Patients in the midostaurin arm experienced a statistically significant improvement in overall survival, with a 23% reduction in risk of death compared to the placebo arm (hazard ratio=0.77, P=0.016).
The median event-free survival was significantly longer in the midostaurin arm than the placebo arm—8.2 months and 3.0 months, respectively (hazard ratio=0.78, P=0.004).
The most frequent adverse events (AEs) in the midostaurin arm (occurring in at least 20% of patients) were febrile neutropenia, nausea, vomiting, mucositis, headache, musculoskeletal pain, petechiae, device-related infection, epistaxis, hyperglycemia, and upper respiratory tract infections.
The most frequent grade 3/4 AEs (occurring in at least 10% of patients) were febrile neutropenia, device-related infection, and mucositis. Nine percent of patients in the midostaurin arm stopped treatment due to AEs, as did 6% in the placebo arm.
Midostaurin in advanced SM
The FDA’s approval of midostaurin in advanced SM was based on results from a pair of phase 2, single-arm studies, hereafter referred to as Study 2 and Study 3.
Data from Study 2 were published in NEJM in June 2016, and data from Study 3 were presented at the 2010 ASH Annual Meeting.
Study 2 included 116 patients, 115 of whom were evaluable for response.
The overall response rate (ORR) was 17% in the entire cohort, 31% among patients with ASM, 11% among patients with SM-AHN, and 19% among patients with MCL. The complete response rates were 2%, 6%, 0%, and 5%, respectively.
Study 3 included 26 patients with advanced SM. In 3 of the patients, the subtype of SM was unconfirmed.
Among the 17 patients with SM-AHN, there were 10 response (ORR=59%), including 1 partial response and 9 major responses. In the 6 patients with MCL, there were 2 responses (ORR=33%), which included 1 partial response and 1 major response.
In both studies combined, there were 142 adults with ASM, SM-AHN, or MCL.
The most frequent AEs (excluding laboratory abnormalities) that occurred in at least 20% of these patients were nausea, vomiting, diarrhea, edema, musculoskeletal pain, abdominal pain, fatigue, upper respiratory tract infection, constipation, pyrexia, headache, and dyspnea.
The most frequent grade 3 or higher AEs (excluding laboratory abnormalities) that occurred in at least 5% of patients were fatigue, sepsis, gastrointestinal hemorrhage, pneumonia, diarrhea, febrile neutropenia, edema, dyspnea, nausea, vomiting, abdominal pain, and renal insufficiency.
Serious AEs occurred in 68% of patients, most commonly infections and gastrointestinal disorders. Twenty-one percent of patients discontinued treatment due to AEs, the most frequent of which were infection, nausea or vomiting, QT prolongation, and gastrointestinal hemorrhage.
