In vitro activity: ETP-46321 is a novel, potent and orally bioavailable inhibitor of PI3Kα and PI3Kδ with Kiapp values of 2.3 nM and 14.2 nM, respectively in biochemical assays. PI3K is an important target for cancer therapeutics due to the deregulation of this signaling pathway in a wide variety of human cancers. TP-46321 PK/PD studies showed time dependent downregulation of AKT(Ser473) phosphorylation, which correlates with compound levels in tumor tissue and demonstrating to be efficacious in a GEMM mouse tumor model driven by a K-Ras(G12V) oncogenic mutation. Treatment with ETP-46321 resulted in significant tumor growth inhibition.

Kinase Assay: ETP-46321 is selected to be screened against other PI3K isoforms. ETP-46321 is more potent against isoform α (Kiapp=2.3 nM). ETP-4632, has been profiled and shown to be a potent PI3K α and δ inhibitor, highly selective versus mTOR and 288 representative kinases. ETP-46321 is also tested against three of the p110α mutant enzymes detected in human cancers (E542K, E545K and H1047R), being equipotent against these mutants when compared to the wild type protein (Kiapp=2.33, 1.77 and 1.89 nM for PI3Kα-H1047R, PI3Kα-E545K and PI3Kα-E542K, respectively). ETP-46321 inhibits the phosphorilation of AKT in U2OS cell line with an IC50 of 8.3 nM.

Cell Assay: