In this study, we evaluated the efficacy of a new, selective, allosteric pan-AKT inhibitor, MK-4440 (formerly ARQ 751), in both IM-sensitive and IM-resistant GIST in vitro and in vivo models, including a GIST patient-derived xenograft (PDX) possessing an exon 9 KIT mutation. Here, KIT is linked to gastrointestinal stromal tumor.