Results from the registrational PIONEER trial suggest that avapritinib (Ayvakit®) improves skin signs and symptoms in patients with indolent systemic mastocytosis (SM). The results will be presented in a late-breaking presentation at the 2023 American Academy of Allergy, Asthma and Immunology (AAAAI) Annual Meeting being held February 24-27 in San Antonio, Texas.

“Avapritinib-treated patients experienced marked reductions in skin symptoms, skin lesion area, and [mast cell] burden; an organ target that has not been addressed before,” the study’s authors wrote in the abstract published in the Journal of Allergy and Clinical Immunology.

The avapritinib arm had significantly greater changes in spot severity and skin symptom domain compared to the placebo arm. Mean change in spot severity at 24 weeks was -1.86 in patients receiving avapritinib and -0.63 in patients receiving placebo. Mean change in skin symptom domain was -5.87 in patients receiving avapritinib and -2.64 in patients receiving placebo.

Moreover, the study’s authors found a correlation between skin domain and the Mastocytosis Quality of Life Questionnaire (MC-QoL), the first disease-specific health-related quality of life questionnaire.

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The analysis of skin lesions in paired photographs showed that the mean percent reduction in lesion surface area was greater in the avapritinib arm compared to the placebo arm (-37% vs -2% in the most affected skin region).

Furthermore, avapritinib decreased mast cell burden (mean percent change, -22%). In contrast, mean percent change in mast cell burden increased by 10% in the placebo arm. CD30+ mast cell proportion in skin lesions decreased by 14% and 0.47% in avapritinib and placebo arms, respectively.

The study enrolled 212 patients who received best supportive care plus avapritinib 25 mg once daily (n=141) or placebo (n=71). The investigators evaluated change from baseline to 24 weeks in spot symptom and skin domain on the ISM-Symptom Assessment Form and skin lesions by photography. Moreover, they assessed mast cell number and immunophenotype (CD25+/CD30+) in skin biopsies using light microscopy and immunohistochemistry.


Maurer M, Siebenhaar F, Broesby-Olsen S, et al. Avapritinib improved skin findings in patients with indolent systemic mastocytosis (ISM) in the registrational, double-blind, placebo controlled PIONEER study. J Allergy Clin Immunol. 2023;151(2, Supplement):AB340. doi:10.1016/j.jaci.2022.12.795

Blueprint Medicines to present positive data from PIONEER trial of Ayvakit® (avapritinib) in indolent systemic mastocytosis at 2023 AAAAI Annual Meeting. News release. Blueprint Medicines Corporation; February 3, 2023.