Assessment of the metabolic stability of avapritinib in human liver microsomes using a fast and green UPLC-MS/MS method: screening for structural alarms associated with metabolic lability and in silico toxicity

Abstract

Avapritinib (Ayvakit™) is a highly selective inhibitor of the platelet-derived growth factor receptor alpha (PDGFRA), including D842V mutations. Avapritinib (APB) is authorized in the United States for individuals with metastatic or unresectable gastrointestinal stromal tumors (GISTs). APB is considered the exclusive therapy for adults with indolent systemic mastocytosis. This study established a rapid, validated, and environmentally friendly UPLC-MS/MS method for assessing APB in human liver microsomes (HLMs), applied to assess the APB metabolic stability. The StarDrop software, with the Metabolism and DEREK modules, was utilized to screen for alerts in the APB chemical structure and assess metabolic stability. APB and encorafenib (ECB as the internal standard) were separated using an isocratic mobile phase approach on an Agilent SB-C18 (reversed-phase) column. The APB calibration curve displayed linearity from 1 ng mL⁻¹ to 3000 ng mL⁻¹. The precision and accuracy for intra- and inter-day assessments ranged from 0.53% to 5.67% and −2.18% to 10.33%, respectively. The implemented UPLC-MS/MS approach is ecologically sustainable, utilizing a diminished percentage of an organic solvent (40% acetonitrile), a short elution duration of 1 min, and a low flow rate of 0.35 mL min⁻¹. The metabolic stability characteristics including the intrinsic clearance and the in vitro half-life of APB were determined to be 22.11 mL min⁻¹ kg⁻¹ and 36.67 min, respectively. In silico analysis suggests that minor structural changes to the methyl pyrazole moiety in drug design may improve the metabolic stability and safety relative to APB.