This study had previously demonstrated the efficacy and safety of the oral, highly selective, KIT D816V inhibitor avapritinib compared with placebo in patients with moderate-to-severe ISM.<h4>Results</h4>In total, 13/212 (6.1%) patients in PIONEER experienced anaphylaxis during screening or treatment (6 during screening, 5 during treatment, and 2 during both screening and treatment). The gene discussed is KIT; the disease is anaphylaxis.