The Food and Drug Administration has approved a new drug for patients with a form of blood cancer who carry a specific genetic mutation, the second drug of its kind to win regulatory approval.
The agency said Wednesday that it had approved Tokyo-based Astellas Pharma’s Xospata (gilteritinib), as a single agent for relapsed or refractory acute myeloid leukemia – or AML – that carries a mutation known as FLT3, as detected by an FDA-approved diagnostic test, Invivoscribe Technologies’ LeukoStrat CDx FLT3 Mutation Assay.
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Xospata is the second FLT3 inhibitor to receive FDA approval, the first one being Novartis’s Rydapt (midostaurin), which the agency approved for FLT3-positive AML last year. However, Rydapt is approved in newly diagnosed AML patients in combination with the chemotherapy drugs cytarabine and daunorubicin – a combination commonly known as 7+3, based on the dosing schedule – followed by cytarabine consolidation.
Xospata’s approval was based on an interim analysis of the Phase III ADMIRAL study. According to the FDA, the analysis included 138 patients from the study – whose total enrollment is 371, according to ClinicalTrials.gov – evaluated for complete remission and complete remission with partial hematological recovery, also known as CR/CRh. The CR/CRh rate was 21 percent, with remissions lasting a median 4.6 months. However, CR/CRh is a surrogate for the study’s primary endpoint, overall survival, or OS, and does not necessarily predict an OS benefit, which is regarded as the gold standard of efficacy in AML. Nevertheless, the company said full results from ADMIRAL would be submitted for presentation at “an upcoming medical meeting.”
BioCentury reported that Xospata’s wholesale acquisition cost would be $22,500 per 30-day course of treatment.
Another FLT3 inhibitor, which could present competition to Xospata, is fellow Japanese drugmaker Daiichi Sankyo’s quizartinib. Final results of the registration-directed Phase III study Quantum-R will be presented next week in an oral session at the American Society of Hematology’s annual meeting in San Diego. The FDA gave priority review to Daiichi Sankyo’s regulatory approval application for the drug on Nov. 22 and is expected to decide whether or not to approve it by May 25, 2019.
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According to an abstract of the quizartinib data, median OS was 6.2 months for those receiving the drug, compared with 4.7 months among patients in the control arm, who received salvage chemotherapy. The complete remission rate was 48 percent among patients receiving quizartinib, compared with 27 percent for those receiving chemotherapy, with respective median durations of 12.1 versus five weeks.
Like Xospata, quizartinib’s pivotal study enrolled patients who are relapsed or refractory after their first round of treatment. But whereas the ADMIRAL study is enrolling patients with multiple types of FLT3 mutations – FLT3-ITD, FLT3-TKD/D835 and FLT3-TKD/I836 – Quantum-R is only enrolling those with FLT3-ITD. As such, assuming the FDA approves the drug with a label based on Quantum-R’s design, it will enable the drug’s use in a narrower pool of patients than Xospata. However, FLT3-ITD is the most common FLT3 mutation.
Photo: Michail_Petrov-96, Getty Images
