In a long-running clinical story about a rare immune disorder, indolent systemic mastocytosis, where mast cells gather in the body and crowd out ordinary comfort, four years of data from the PIONEER study now suggest that avapritinib can quiet the worst of the suffering for most who take it. Presented in Phoenix by Thanai Pongdee of Mayo Clinic, the findings show severe symptoms receding and mild ones becoming the common condition, with no new safety concerns emerging along the way. The evidence is still young in the scientific sense, since it has been shared at a congress and not yet tested t
Four-Year Avapritinib Data in ISM Show Most Patients Moving From Severe to Mild Symptoms
Minimal skin disease does not rule out substantial burden elsewhere
Mark
The headline is that severe symptoms dropped from 58.5% to 24.4%. Why does that matter for someone living with ISM?
Mimi
Because the shift is about function. Pongdee talked about getting through a school day or work day without interruption, and with less mental stress.
Mark
And mild symptoms went from 14.3% to 54.7%.
Mimi
Yes, so more than half of patients now sit in the mild range after four years.
Luke
Worth saying what that comparison is. Those are baseline versus four-year proportions in people still on treatment. The source doesn't tell us how patients who stopped were counted.
Mark
Safety looked reassuring, though.
Mimi
Discontinuations tied to treatment were 3%, edema was the most common adverse event, and Pongdee described cognitive events as infrequent.
Luke
That last point is his characterization. No cognitive event rate is given in what we have.
Mark
What about the skin findings?
Mimi
Skin involvement didn't predict overall burden. Symptom scores were similar across groups, so mild skin disease can still come with heavy gut, bone, muscle or cognitive symptoms.
Luke
That was in 126 patients, from a poster. And all of this is unreviewed congress data, so it's early to treat it as settled.
O Pulso
- Severe symptoms in a rare mast cell disorder dropped from 58.5% to 24.4% of patients over four years of avapritinib treatment.
- Mild symptoms climbed from 14.3% to 54.7%, pushing many patients out of the ranks of the most debilitated.
- Only 3% of patients stopped treatment because of side effects, with edema the most frequent drug-related complaint.
- Clinicians are tracking tryptase and KIT D816V burden yearly, while a new 150-patient observational study will watch bone health and anaphylaxis for up to five years.
- The results remain unreviewed congress data, so the full picture is still settling into the medical record.
In a long-running clinical story about a rare immune disorder, indolent systemic mastocytosis, where mast cells gather in the body and crowd out ordinary comfort, four years of data from the PIONEER study now suggest that avapritinib can quiet the worst of the suffering for most who take it. Presented in Phoenix by Thanai Pongdee of Mayo Clinic, the findings show severe symptoms receding and mild ones becoming the common condition, with no new safety concerns emerging along the way. The evidence is still young in the scientific sense, since it has been shared at a congress and not yet tested through peer review, but it marks a meaningful chapter in how patients may live with a disease once measured mainly by its hazards.
At the American College of Allergy, Asthma and Immunology meeting in Phoenix, Thanai Pongdee, a Mayo Clinic allergist, presented four years of results from the PIONEER study of avapritinib, sold as Ayvakit, in indolent systemic mastocytosis. Over that span, most patients moved from severe symptoms to mild ones, and no new safety worries surfaced.
Among 226 patients who began the 25 mg daily dose, with a median treatment time of nearly four years, the share with severe symptoms fell from 58.5% to 24.4%, while those with mild symptoms rose from 14.3% to 54.7%. Pongdee emphasized what this means in ordinary life: people can get through a school or work day without interruption, think more clearly, and carry less stress.
Side effects were manageable. Treatment was stopped in 3% of patients for drug-related reasons, edema was the most common complaint, and cognitive problems stayed uncommon. Pongdee's own clinic monitors tryptase yearly and sometimes the KIT D816V variant to gauge mast cell burden. A separate poster on 126 patients found that minimal skin involvement can hide significant gastrointestinal, musculoskeletal, or neurocognitive symptoms, a reminder that the visible rash is not the whole disease.
Looking ahead, the PANORAMA-US observational study will follow about 150 adults for up to five years, tracking bone health and anaphylaxis alongside everyday dosing. These findings are congress data and have not yet been peer reviewed.
At the American College of Allergy, Asthma and Immunology annual meeting in Phoenix, Arizona, which runs November 12 to 16, 2026, Thanai Pongdee, MD, presented four-year results from the PIONEER study of avapritinib (Ayvakit) in indolent systemic mastocytosis, or ISM. The headline finding: over four years of treatment, most patients moved from severe symptoms to mild ones, and no new safety concerns emerged.
Pongdee is an associate professor of medicine and research chair of the Division of Allergic Diseases at Mayo Clinic in Rochester, Minnesota. His analysis builds on earlier four-year PIONEER data on quality of life. The randomized portion of the trial had already shown that avapritinib at 25 mg once daily lowered the ISM Symptom Assessment Form total symptom score more than placebo at week 24, with a drop of 15.6 points against 9.2 points (P = .003).
The long-term numbers rest on a large group. As of September 17, 2025, 226 patients had started avapritinib at 25 mg, and the median treatment duration was 46.5 months. Among them, the share with severe symptoms, defined as a total symptom score above 42, fell from 58.5% at baseline to 24.4% after four years. The share with mild symptoms, a score below 28, rose from 14.3% to 54.7%.
Pongdee framed the change in terms of daily life. Milder symptoms, he said, mean a person can fully take part: getting through a school day or a work day without interruption, being more productive, and carrying less mental stress.
On safety, treatment-related discontinuations occurred in 3% of patients. Edema was the most common treatment-related adverse event, and Pongdee said cognitive adverse events remained infrequent. In his own practice he checks tryptase annually and may also follow the KIT D816V variant allele fraction to track mast cell burden.
A separate PIONEER analysis, presented as a poster, looked at 126 patients and asked whether skin involvement predicts the rest of the disease. Baseline total symptom scores were similar regardless of how much skin surface was affected by lesions, and gastrointestinal and neurocognitive domain scores were comparable across groups. Skin domain scores were worse in patients with 20% or more involvement. Pongdee drew a practical conclusion: minimal skin disease does not rule out a substantial gastrointestinal, musculoskeletal, or neurocognitive burden.
In the extension study, patients with persistent symptoms could raise their dose to 50 mg daily. Pongdee said the FDA label now allows that option after six months at 25 mg.
Looking ahead, the phase 4 PANORAMA-US observational study (NCT07264959) plans to follow about 150 adults with ISM for up to five years. It will capture symptoms, quality of life, bone health, anaphylaxis, and how avapritinib is actually dosed in routine care. The data presented in Phoenix are congress findings and have not been peer reviewed. Disclosures include Blueprint Medicines.
Citações Notáveis
If your symptoms are milder, then you can fully participate in life... I can get through the school day, the work day, without being interrupted.— Thanai Pongdee, MD, Mayo Clinic
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