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FDA Approves Blueprint Medicines' Ayvakit for Advanced Systemic Mastocytosis

NEW YORK – The US Food and Drug Administration on Wednesday approved Blueprint Medicines' avapritinib (Ayvakit) to treat advanced systemic mastocytosis, a disorder that produces too many mast cells in the body and that can become cancer.

Avapritinib targets and inhibits the KIT D816V mutation, which drives SM. The agency specifically approved the drug for advanced SM, including patients with aggressive systemic mastocytosis (ASM), systemic mastocytosis with an associated hematological neoplasm (SM-AHN), and mast cell leukemia (MCL). In these advanced SM subtypes, the median overall survival is approximately 3.5 years in ASM, approximately two years in SM-AHN, and less than six months in MCL, Blueprint said in a statement.

The FDA approved avapritinib's advanced SM indication after reviewing data from the Phase I EXPLORER and Phase II PATHFINDER trials. In 53 evaluable patients in these two studies, the overall response rate was 57 percent, with 28 percent of these patients achieving complete remission with full or partial hematologic recovery and 28 percent achieving partial remission. The median duration of response was 38.3 months.

"As shown in two clinical trials, Ayvakit provides remarkable clinical efficacy to patients with advanced systemic mastocytosis, and this approval solidifies the therapy's strong value proposition in this population," Blueprint CEO Jeff Albers said in a statement. The company will initially focus on making avapritinib available in 70 cancer centers that treat about half of the advanced SM patients in the US, with plans to expand into community oncology settings later, Christina Rossi, chief commercial officer at Blueprint, said on an investor call on Wednesday.

"With a deep commitment to driving continued research innovation in collaboration with the mast cell disease community, we are now building on this progress with the goal of bringing the benefits of precision therapy to a broader range of patients through our ongoing and planned clinical trials for non-advanced systemic mastocytosis," Albers added. The company is currently studying the drug versus a placebo in the Phase II PIONEER study in indolent SM.

Avapritinib was approved last year in the US and Europe to treat unresectable or metastatic gastrointestinal stromal tumors harboring a PDGFRA exon 18 mutation.