Development of Small Molecule Replication Inhibitors Against Western Equine Encephalitis Virus.

Abstract

Arborviruses such as western equine encephalitis virus (WEEV) are capable of causing a wide range of diseases in humans. The CDC and NIAID consider WEEV as a potential bioterrorism weapon due to several factors: potential for aerosol transmission, lack of effective countermeasures, and ease of genetic manipulation to increase virulence and high levels of death. A series of thieno[3,2-b]pyrrole-based inhibitors were discovered to be active against WEEV following a high-throughput screen (HTS). This dissertation discusses the development of novel indole-2-carboxamide RNA replication inhibitors with improved in vitro and in vivo activity and the development of tag-free photoaffinity probes for target identification. A first-generation indole, CCG 203926 (12), with modestly improved potency and metabolic stability over the original screening lead CCG 32091, achieved efficacy in a preliminary in vivo study against neuroadapted Sindbis virus. Second-generation inhibitor, CCG 205432 (50), was the first inhibitor with submicromolar activity and further improved half-life compared to CCG-203926. In a WEEV-infected mouse model, in which CCG 203926 was inactive, it increased survival and decreased disease severity. Even though a related third generation inhibitor, CCG 209023 (110), was less potent than 50, it had a significantly improved half-life, lower recognition by Pgp and equal efficacy to CCG-205432 at improving survival. It was determined that 50 and related indole-2-carboxamide inhibitors have a wide range of activity against other RNA viruses and elicit their antiviral activity by targeting host factors instead of viral enzymatic proteins. One of the two photoaffinity probes, 126, is equipotent to lead indole 50 and is currently being used for preliminary target identification studies. Compound 110 is also being studied as a combination therapy with neuroprotective agents. The lack of clinical therapeutics against alphaviruses emphasizes the significance of this work, as there is a critical need to develop potent antivirals against these pathogens.