Clinicians who weigh symptom control and biomarker response more heavily than quality of life risk overlooking the emotional and social toll of indolent systemic mastocytosis (ISM). Even when symptoms and biomarkers appear controlled, patients may still experience daily fear, activity avoidance, and social withdrawal.

In this Q&A, Thanai Pongdee, MD, of Mayo Clinic, discussed 4-year data from the PIONEER trial showing that avapritinib continues to improve emotional well-being and social functioning in patients with ISM, extending beyond symptom and biomarker control alone.^1,2,3 The analysis, presented at the European Academy of Allergy & Clinical Immunology (EAACI) 2026 Annual Meeting in Istanbul, followed 226 patients treated with avapritinib 25 mg once daily, with a median treatment duration of 46.5 months.

Mean total symptom score on the ISM-Symptom Assessment Form and mean percentage change in the Mastocytosis Quality of Life Questionnaire total score both showed continued improvement from baseline through 1 and 4 years. Nearly half of patients reported less fear of an allergic reaction after long-term treatment, and by 3 years, 52% of patients had reduced or discontinued use of ≥ 1 class of best supportive care medication. The safety profile remained consistent through 4 years, with treatment-related discontinuations occurring in just 3% of patients and no new safety signals identified.

Avapritinib's 4-Year PIONEER Data Show Durable QoL Benefits in ISM

HCPLive: What does it mean to see clinically meaningful improvements in emotional well-being and social functioning, not just symptom or biomarker control, in this PIONEER analysis?

Pongdee: It's very meaningful because not only do we want to see symptom improvement, but importantly we want patients to be able to function in their daily activities, whether it be work or social situations, because disease, being chronic in nature, can significantly impact those kinds of activities and emotional well-being, and create social isolation and negative feelings. Anything that can improve those aspects of a disease is as equally important as symptom control.

HCPLive: How do these emotional well-being findings, including reduced fear, loneliness, and sadness, compare with what you've observed in this patient population before treatment?

Pongdee: The trial findings and report have certainly mirrored what we observe and hear from patients in the clinic, which is good to see. Many patients report being able to go out to eat with friends or family and not have to worry like they used to. They used to avoid going out to social functions because they were very worried about something happening or some symptom flare occurring.

After being on treatment, they've seen those symptoms improve or go away in many respects. They're able to engage in many activities that they otherwise would have avoided. In a similar way, on the work front, various work activities that may have been avoided or not even attempted may have limited their progress in the workplace. Having those restrictions or fears lessened or removed has certainly helped in that aspect as well.

HCPLive: How should this data change the way clinicians evaluate treatments and assess ISM beyond mast cell burden or serum tryptase?

Pongdee: We always have to keep the patient at the center. It's nice to see biomarkers of disease improve, and that's obviously very important…but at the end of the day, the patients have to feel better, be able to function in an unrestricted manner. That's really the whole point of taking medicine, especially from a patient point of view.

HCPLive: Nearly half of patients reported less fear of an allergic reaction. How significant is anaphylaxis-related anxiety as a driver of quality of life in ISM, and how does avapritinib appear to address it?

Pongdee: The fear of anaphylaxis or other allergic reactions significantly impacts the majority of patients with SM. There's this constant worry that this could happen at any time, and many of the medicines we have hopefully can reduce that risk of occurrence. It makes rational sense to think that if you're decreasing mast cell burden, the likelihood of such events would decrease.

Now, that wasn't a primary endpoint in the study. There was some retrospective evidence that avapritinib may help reduce risk of anaphylactic events. We published a short report to that effect, but that's still an open question, and it's being more thoroughly investigated in a current trial.

All I have to say is decreasing that risk and consequently the fear of that happening really frees patients to do activities that we would consider pretty typical that would have otherwise been avoided. Someone who never went out to eat, never went to a school reunion, never went to an employee picnic, things a lot of us take for granted, can [now] enjoy [these] activities.

Key Takeaway from This 4-Year Pioneer Analysis

HCPLive: What's the key takeaway for clinicians who currently weigh symptom control or biomarker response more heavily than quality of life measures?

Pongdee: It's something you can't forget. All those aspects of treatment are very important, but we can't lose sight of quality of life.

HCPLive: How might these findings shape conversations with patients about what to expect when starting avapritinib?

Pongdee: Patients want to know how they're going to feel. They want to understand what the drug is doing, and its mechanism of action.

At the end of the day, they want to know how it's going to make them feel better: “Is there a certain way it's going to help me feel better? Is it going to help my skin symptoms or my gastrointestinal symptoms, or should everything be better? Am I going to keep taking all the medicines I take now?”

Most patients have polypharmacy, and these things are all connected. If the disease burden is less, then I would expect symptoms to get better. Hopefully that means I don't have to [prescribe] as many medicines, and then all that equals greater quality of life.

HCPLive: What remains unknown about the durability of these emotional and social functioning benefits, and what follow-up data are you hoping to see?

Pongdee: What was very encouraging in the data is that, at least at the 4-year cutoff, all aspects of improvement, whether it be symptoms, disease burden, or quality of life, are all durable improvements. Certainly, longer-term data is more encouraging and more reassuring, so keeping track of those features over time would be good to see.

Safety looked very good over the long term, with low incidence of any safety issues over 4 years. Patients always ask, "Well, how about in 5 years, 10 years, 15 years, if I keep taking this drug?" Seeing that long-term data will be very reassuring for everyone involved.

Watch parts 1 and 2 of the interview with Pongdee here: Avapritinib 4-Year PIONEER Data: Sustained QoL Gains in ISM and Avapritinib 4-Year Data Show Durable Quality of Life Gains in ISM, respectively.

References

1. Pongdee T. Avapritinib 4-Year PIONEER Data: Sustained QoL Gains in ISM. HCPLive. Published July 13, 2026. Accessed July 27, 2026. https://www.hcplive.com/view/avapritinib-4-year-pioneer-data-ism-quality-of-life

2. Pongdee T. Avapritinib 4-Year Data Show Durable Quality of Life Gains in ISM. HCPLive. Published July 16, 2026. Accessed July 27, 2026. https://www.hcplive.com/view/avapritinib-4-year-pioneer-data-ism-pongdee

3. Broesby-Olsen S, Siebenhaar F, Oude Elberink H, et al. Mastocytosis Treated With Avapritinib: Updated 4-Year Results From The PIONEER Trial. Presented at European Academy of Allergy & Clinical Immunology (EAACI) 2026 Annual Meeting from June 12-15, 2026 in Istanbul, Türkiye.