New results published in the Journal of Allergy and Clinical Immunology suggest that avapritinib may offer lasting relief for people living with indolent systemic mastocytosis (SM).
Historically, treatment for indolent SM has relied on supportive care, such as antihistamines and corticosteroids, which address symptoms but do not target the underlying cause of the disease. Avapritinib, an oral tyrosine kinase inhibitor, is designed to selectively block the KIT D816V mutation, which leads to abnormal mast cell accumulation and is the primary driver of SM.
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The data is from the open-label extension of the PIONEER study, which previously found that patients who took avapritinib for 24 weeks had reduced symptoms, reduced biomarkers of disease burden and improved quality of life.
To better understand how avapritinib affects patients long-term, the extension followed 226 patients who received 25 mg of avapritinib once daily alongside supportive care. Researchers followed participants for a median of 40 months.
The researchers used a specialized tool that asked participants to rate their symptoms, including flushing, itching, abdominal pain, diarrhea, nausea, brain fog, fatigue, dizziness and bone pain. Symptoms were rated on a scale of 0 to 10, where 0 meant the symptom was absent and 10 represented the worst imaginable severity. The individual symptom scores were then combined into a total symptom score.
The average symptom score before treatment was 48. After roughly two years of treatment with avapritinib patients had an average reduction of about 17 points in total symptoms scores, and a reduction of 19 points after three years. Biomarkers of disease such as serum tryptase levels also improved.
The trial included a group of 65 patients who increased their avapritinib dose from 25 mg daily to 50 mg daily during the open-label extension phase of the study. Their symptom scores dropped by an average of eight points after the dose was increased.
The study’s authors concluded that the long-term follow-up data shows avapritinib remains effective and well tolerated over several years of treatment.
“Our results indicate that avapritinib demonstrates durable efficacy and a favorable tolerability profile in patients with ISM during a median follow-up exceeding 3 years, an important observation for managing this chronic disease,” they wrote.
The ongoing extension is designed to collect up to five years of follow-up data, helping researchers better understand long-term outcomes.
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