Research Project 4

PK-enhanced PI-kinase (PI4K; PI5K) inhibitors of RNA viruses

Jeffrey Glenn, MD, PhD

Associate Professor of Medicine (Gastroenterology and Hepatology) and Microbiology and Immunology – Stanford University 
PI, Project 4 Leader, Admin Core Director


Kevan Shokat

Professor and Department Chair Cellular and Molecular Pharmacology - UCSF School of Medicine
Project 4 Co-Investigator


Project Summary:

Our goal is to develop broad spectrum, small molecule antivirals with high barriers to resistance against multiple Priority Pathogens. We discovered a novel specific phosphoinositide (PI)-4,5-bisphosphate (PI(4,5)P2, or “PIP2”) binding motif (termed a Basic Amino Acid PIP2 Pincer (or“BAAPP domain”) within the HCV NS5A protein that mediates specific interaction with PIP2, and point mutations in the BAAPP domain abrogate PIP2 binding and HCV RNA replication. Moreover, similar dependence on BAAPP domain-mediated PIP2 binding appears to be widespread among pathogens, including multiple listed Priority Pathogen viruses from HAV and enterovirus 71 to Ebola. siRNA knockdown of host cell PI4kinase or PIP5 kinase, that sequentially generate intracellular PIP2, can impair viral replication without significant cellular toxicity. We have produced and characterized a novel PI-4 kinase inhibitor (PT423) that exhibits nM in vitro activity against multiple pathogens, and we have embarked on a similar approach to generate potent inhibitors of PIP5kinase, indicating that pharmacologic inhibition of these enzymes represents an attractive approach to translate the above findings into a practical broad spectrum antiviral treatment. We now seek to: 1) Identify optimized and PK-enhanced P14K inhibitors. We will optimize our lead and identify a back-up compound by modifying PT423 to improve its ADME and PK properties. We will then determine the antiviral efficacy (against HCV, HAV, enterovirus71, and Ebola), PI4-kinase inhibitory activity, and metabolic stability of these derivatives in vitro. To enable comparison of non-selective vs. PK-enhanced analogs, we will screen and optimize selected derivatives for their rodentin vivo liver/plasma concentrations following oral administration; 2) Determine the in vivo activity, metabolism, and relative barrier to resistance of the above PI4K inhibitors; 3) Optimize our lead’s PIP5-kinase inhibitory and antiviral activities, determine its major in vitro metabolites, assess the optimized lead’s efficacy against wild type and drug resistant mutants of selected priority viruses, with or without other available antivirals, and being safety testing; 4) Maximize our lead PI4kinase inhibitor’s therapeutic index (TI) by determining its EC50 when used in combination treatment (with a PIP5K inhibitor or other proposal projects’ agents), identifying hepatically activated prodrug analogs, and determining the feasibility of 2’-5’phosphodiester prodrug analogs designed to be activated by elevated 2’phosphodiesterase in virally infected cells, for inclusion into lead optimization efforts; 5) Nominate a PI-4K inhibitor IND candidate by subjecting the optimized lead, its major metabolite, and PK-enhanced version to in vitro ADME-tox studies and initial preclinical animal safety testing