Blueprint Medicine Announces Published Results From 2 Registration Studies of Ayvakit


Results highlight sustained benefits of avapritinib in patients with advanced systemic mastocytosis.

Blueprint Medicine Corporations has announced 2 Nature Medicine publications on the registration-enabling EXPLORER and PATHFINDER trials of avapritinib (Ayvakit), the company said in a statement.

The publications highlight the robust efficacy and safety dataset of avapritinib, a kinase inhibitor, for treatment in advanced systemic mastocytosis (SM), by featuring the individual-reported outcomes, overall response, and survival data.

The papers are titled “Safety and efficacy of avapritinib in advanced systemic mastocytosis: the phase 1 EXPLORER trial," and "Efficacy and safety of avapritinib in advanced systemic mastocytosis: interim analysis of the phase 2 PATHFINDER trial.”

The additional new analyses underscore the treatment’s impact, regardless of an individual’s disease pathology or subgroup.

SM is a rare hematologic disorder driven by the KIT D816V mutation in nearly all cases.In advanced SM, the median of overall survival with previously available treatment options is less than 6 months to approximately 3.5 years, varying with subtype.

"The data published today in Nature Medicine comprise the largest therapeutic dataset ever reported in advanced systemic mastocytosis, encompassing 2 studies enrolling approximately 150 patients with up to 4 years of follow-up, and reflecting our deep commitment to pioneer new science and improve outcomes for patients living with this devastating disease," Becker Hewes, MD, chief medical officer at Blueprint Medicines, said in the statement.

Across the EXPLORER and PATHFINDER studies, 148 patients with advanced SM were enrolled as of the data cutoff dates. Treatment response was evaluated using modified IWG-MRT-ECNM criteria, with the overall response rate defined as complete remission with full or partial recovery of peripheral blood counts, partial remission, or clinical improvement. All responses were confirmed. The results were reported as of a data cutoff date of May 27, 2020, for the EXPLORER trial and June 23, 2020, for the PATHFINDER trial.

Statistically significant improvements were observed in both studies, measured by the Advanced SM Symptom Assessment Form Total Symptom Score. Avapritinib showed broad activity across all advanced SM subtypes.

The overall response rates for the EXPLORER and PATHFINDER trials were 75%. The median duration of response for the EXPLORER trial was 38 months but was not estimable for the PATHFINDER trial.

The overall estimated survival rates were 76%, at 24 months, and 86%, at 12 months, for the EXPLORER and PATHFINDER trials, respectively.

The substantial reductions that were observed in monocytosis in individuals with SM and chronic myelomonocytic leukemia, as well as eosinophilia in individuals with SM and chronic eosinophilic leukemia, could potentially reflect the multi-lineage involvement of the KIT D816V mutation.

Avapritinib was generally well-tolerated, and most adverse events (AEs) were grade 1 or 2, with the most common including anemia, diarrhea, edema, fatigue, nausea, thrombocytopenia, and vomiting.

Overall, 10% of individuals in the EXPLOERER trial and 5% of individuals in the PATHFINDER trial discontinued avapritinib, because of treatment related AEs. Avapritinib is not recommended for individuals with advanced SM who have low platelet counts.

Blueprint Medicines also announced plans to report 4 SM data presentations at the American Society of Hematology Annual Meeting and Exposition.

The FDA approved avapritinib for adults with advanced SM in June 2021. Avapritinib is also approved for mast cell leukemia and adults with unresectable or metastatic gastrointestinal stromal tumors with a PDGFRA exon 18 mutation.


Nature Medicine publishes results from two registration studies of AYVAKIT® (avapritinib) showing sustained benefits in patients with advanced systemic mastocytosis. PR Newswire. News release. December 6, 2021. Accessed December 7, 2021.

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