FDA Approves Avapritinib for the Treatment of Indolent Systemic Mastocytosis

The FDA has approved avapritinib (Ayvakit; Blueprint Medicines Corporation) for the treatment of individuals with indolent systemic mastocytosis (ISM). This is the first and only FDA-approved medication designed to treat ISM.

"[Avapritinib] is the first and only medicine approved by the FDA to treat [ISM], marking a shift in the treatment paradigm from supportive care to disease modifying therapy.” Becker Hewes, MD, chief medical officer at Blueprint Medicines, said in a press release. “In addition, [avapritinib] is the only treatment approved across the spectrum of indolent and advanced systemic mastocytosis. With a broad indication and a strong label, we are now engaging health care providers to redefine what it means for their patients to be well-controlled as well as activating the patient community to seek out optimal care and treatment.”

FDA Approval | Image credit: Argus- stock.adobe.com

Systemic mastocytosis is a rare hematologic disorder that can lead to debilitating symptoms across multiple organ systems, with ISM representing the vast majority of all cases.

Avapritinib is recommended at the 25 mg dosage strength, taken once a daily. It was designed to potently and selectively inhibit KIT D816V, which is known to be the primary driver of ISM. The drug has been FDA approved for the treatment of advanced systemic mastocytosis since June 2021.

The new approval is based on data from a double-blind, placebo-controlled trial, PIONEER (NCT03731260), which was the largest study to date for the disease. In the trial, patients received avapritinib 25 mg once daily plus the best supportive care, or the placebo and the best supportive care.

Investigators found that treatment with avapritinib showed significant improvements in the primary and key secondary endpoints, including overall symptoms and measures of mast cell burden, when compared to the placebo.

"Despite the use of multiple supportive care treatments, a considerable number of patients with [ISM] continue to experience a substantial disease burden. [Avapritinib] advances the treatment of [ISM] by targeting KIT D816V, the primary underlying cause of the disease, and establishes a new standard of care for a broad population of patients with this disorder,” Cem Akin, MD, PhD, professor of Medicine at the University of Michigan, said in the press release. “[Avapritinib] delivered statistically significant and consistent clinical improvements in the PIONEER trial, and based on these practice-changing data, I feel a tremendous sense of hope for the future for all those affected by the disease."

Avapritinib was generally well tolerated and had a favorable safety profile compared to the placebo. Most adverse effects (AEs) were mild to moderate in severity, with the most common being eye edema, dizziness, peripheral edema, and flushing. Serious AEs and discontinuations due to AEs occurred in less than 1% of individuals in the study.

The detailed results from the PIONEER trial, which included the open-label extension study that demonstrated clinical benefits through 48 weeks, were presented in February 2023 at the American Academy of Allergy, Asthma, & Immunology Annual Meeting.

Reference

FDA approves Ayvakit (avapritinib) as the first and only treatment for indolent systemic mastocytosis. News release. May 22, 2023. Accessed May 22, 2023. https://ir.blueprintmedicines.com/news-releases/news-release-details/fda-approves-ayvakitr-avapritinib-first-and-only-treatment