Long-Term PIONEER Data Reinforce Avapritinib's Role in Indolent Systemic Mastocytosis

At the 2026 American Academy of Dermatology Annual Meeting (AAD 2026), Lauren Madigan, MD, assistant professor of dermatology at the University of Utah and faculty at the Mastocytosis Center of Excellence at the Huntsman Cancer Institute, presented open-label extension data from the PIONEER trial (NCT03731260) evaluating avapritinib in indolent systemic mastocytosis (ISM).¹ According to Madigan, the findings suggest the drug's benefits are both meaningful and lasting.

Avapritinib is an oral selective inhibitor of the KIT D816V mutation, which is present in approximately 95% of adults with ISM. "It's a really exciting drug," Madigan said, "because approximately 95% of adults with ISM have the D816V mutation, so it's a good opportunity to treat most of our patients with a really selective drug."^2,3

The extension data presented at AAD 2026 captured a median follow-up of approximately 4 years. Patients showed durable improvements in skin symptoms, lesion appearance, skin color, and lesional density—benefits that were sustained or continued to improve from the initial 6-month phase 2 period through year 4. The safety profile remained favorable: Of approximately 226 patients in the extension phase, only 6 discontinued due to treatment-related adverse events. "Overall, a really well-tolerated medication," Madigan said.

For dermatology clinicians, she emphasized their unique gatekeeping role in ISM. Most adult patients with ISM present with fixed skin lesions, one of the few disease-specific clinical signs, making dermatology clinicians often the first to identify these patients. "We have better therapies to offer them now," she said, "so we can get them appropriately staged and ensure they have access." She also noted that next-generation selective tyrosine kinase inhibitors are advancing through clinical trials. "It was a condition where, for a long time, we didn't have as much to offer patients outside of best supportive care, like antihistamines. Now, we have very selective drugs targeting the actual mutation that causes disease, and they're pretty powerful."

Recognition of VEXAS Syndrome

Madigan also addressed VEXAS syndrome, describing it as "a fascinating hematoinflammatory disease, also clonally driven." Caused by somatic mutations in the UBA1 gene on the X chromosome, VEXAS predominantly affects men 50 years and older and presents with a constellation of findings: noninfectious fevers, elevated inflammatory markers, cytopenias (most commonly macrocytic anemia), and skin manifestations including neutrophilic dermatitis, chondritis, and vasculopathy.⁴ "If you treat them like typical Sweet syndrome or chondritis, they tend not to respond," she said.

The disease carries high mortality and morbidity, and current therapies, including IL-6 inhibitors and ruxolitinib, offer limited response rates. Azacitidine and stem cell transplant have been explored to target the underlying clone, though patient frailty often limits eligibility. A dedicated clinical trial for VEXAS is expected to open soon. "We know the gene, we know the driver," Madigan said. "But now we've got to find the good drug."

References

1. Madigan L. Skinternal medicine: an update on cutaneous manifestations of systemic disease. Presented at: 2026 American Academy of Dermatology Annual Meeting; March 27-31, 2026; Denver, CO.
2. Blueprint Medicines, a Sanofi company, announces four-year PIONEER data showing sustained benefit and long-term safety of Ayvakit (avapritinib) in indolent systemic mastocytosis. News release. Blueprint Medicines. February 28, 2026. Accessed April 6, 2026. https://ir.blueprintmedicines.com/news-releases/news-release-details/blueprint-medicines-sanofi-company-announces-four-year-pioneer
3. Gotlib J, Castells M, Elberink HO, et al. Avapritinib versus placebo in indolent systemic mastocytosis. NEJM Evid. 2023;2(6):EVIDoa2200339. doi:10.1056/EVIDoa2200339
4. Sikora KA, Wells KV, Bolek EC, Jones AI, Grayson PC. Somatic mutations in rheumatological diseases: VEXAS syndrome and beyond. Rheumatology (Oxford). 2022;61(8):3149-3160. doi:10.1093/rheumatology/keab868