Abstract B085: Preclinical pharmacokinetic/pharmacodynamic (PK/PD) relationship demonstrated for BVD-723, a potent and selective phosphoinositide 3-kinase gamma (PI3Kγ) inhibitor (2018)

Abstract The phosphoinositide 3-kinase (PI3K) family of enzymes play a pivotal role in controlling vital cellular functions, including proliferation, motility, glucose metabolism, and survival. The PI3Kγ isoform has been shown to play an important role in immune cell migration and function in the tumor microenvironment. BVD-723 is a potent and selective small-molecule inhibitor of the PI3Kγ isoform (PI3K γ/α/β/δ Ki = 8/280/220/160 nM). AKT, a serine/threonine protein kinase, is a downstream effector of PI3K. AKT phosphorylation was therefore chosen as a PD marker to demonstrate BVD-723 activity. Here we describe the PK/PD relationship from a single-day, oral, multi-dose level, multi-timepoint study in Balb/c mice. The PD assay, utilizing phospho flow cytometry, measured the ability of BVD-723 to attenuate AKT phosphorylation at the S473 residue in response to extracellular ligands in primary cell subsets that included monocytes, T cells, and B cells. Initial work identified CCL2 and CXCL12, which are thought to signal primarily through PI3Kγ, as ligands that induced robust pAKT signal in both human and murine monocytes. LPS, which is thought to signal primarily through PI3Kδ, was used to assess isoform selectivity in this assay. BVD-723 was administered as a single oral dose (0.5, 1, 3, 5, 10, 30, or 100 mg/kg) to Balb/c female mice. Blood was collected via terminal draw from 3 animals per dose group and per timepoint (pre-dose, 0.5, 1, 2, 4, 6, 8, 12, and 24 hours) and was split into two samples. The first sample was processed to plasma and BVD-723 levels measured using LC-MS/MS assay. The second whole blood sample was analyzed for pAKT following ex vivo stimulation. PK analysis of each dose demonstrated a Tmax between 2-6 hours and a t1/2 of 4-5 hours. The Cmax levels for each dose of 0.5, 1, 3, 5, 10, 30, and 100 mg/kg were 218, 577, 2050, 3670, 9130, 23200, and 29300 ng/ml, respectively, and the AUC0-24 values were 1.8, 5, 21, 38.2, 107, 318, and 519 µg*hr/ml, respectively. The PD assay demonstrated a clear dose- and time-dependent inhibition of AKT phosphorylation in monocytes downstream of CCL2 and CXCL12 stimulation but not LPS stimulation. Consistent with the PK data, a peak inhibition of pAKT signal occurred between 2-4 hours post dose. The CXCL12-induced AKT phosphorylation in monocytes was robustly inhibited for 24 hours at 30 mg/kg and 100 mg/kg. Overall, the PD results showed clear selectivity of BVD-723 for PI3Kγ inhibition in monocytes, with no inhibition of PI3Kδ. Additional ex vivo studies in blood were conducted utilizing this PD assay comparing other PI3K isoform selective inhibitors to BVD-723. These data provide a solid PK/PD relationship, providing guidance for continued development of BVD-723 for oncology. Citation Format: Deborah Knoerzer, Martin Teresk, Peter Krutzik, Erika O’Donnell, Gary DeCrescenzo, Dean Welsch, Caroline Emery. Preclinical pharmacokinetic/pharmacodynamic (PK/PD) relationship demonstrated for BVD-723, a potent and selective phosphoinositide 3-kinase gamma (PI3Kγ) inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B085.