Discovery and optimization of potent broad-spectrum arenavirus inhibitors derived from benzimidazole.

A chemically diverse library of about 400,000 small molecules was screened for antiviral activity against lentiviral pseudotypes with the Lassa virus envelope glycoprotein (LASV GP) gene incorporated. High-throughput screening resulted in discovery of a hit compound (ST-37) possessing a benzimidazole core which led to a potent compound series. Herein, we report SAR studies which involved structural modifications to the phenyl rings and methylamino linker portion attached to the benzimidazole core. Many analogs in this study possessed single digit nanomolar potency against LASV pseudotypes. Compounds in this benzimidazole series also exhibited nanomolar antiviral activity against pseudotypes generated from other arenavirus envelopes indicating the potential for development of a broad-spectrum inhibitor. Ultimately, lead compound ST-193 was identified and later found to be efficacious in a lethal LASV guinea pig model showing superior protection compared to ribavirin treatment.

Discovery and optimization of potent broad-spectrum arenavirus inhibitors derived from benzimidazole and related heterocycles.

A series of potent arenavirus inhibitors sharing a benzimidazole core were previously reported by our group. SAR studies were expanded beyond the previous analysis, which involved the attached phenyl rings and methylamino linker portion, to include modifications focused on the benzimidazole core. These changes included the introduction of various substituents to the bicyclic benzimidazole ring system along with alternate core heterocycles. Many of the analogs containing alternate nitrogen-based bicyclic ring systems were found to retain antiviral potency compared to the benzimidazole series from which we derived our lead compound, ST-193. In fact, 21 h, built on an imidazopyridine core, possessed a near tenfold increase in potency against Lassa virus pseudotypes compared to ST-193. As found with the benzimidazole series, broad-spectrum arenavirus activity was also observed for a number of the analogs discovered during this study.

SAR analysis of a series of acylthiourea derivatives possessing broad-spectrum antiviral activity.

A series of acylthiourea derivatives were designed, synthesized, and evaluated for broad-spectrum antiviral activity with selected viruses from Poxviridae (vaccinia virus) and two different genera of the family Bunyaviridae (Rift Valley fever and La Crosse viruses). A compound selected from a library screen, compound 1, displayed submicromolar antiviral activity against both vaccinia virus (EC(50)=0.25 µM) and La Crosse virus (EC(50)=0.27 µM) in cytopathic effect (CPE) assays. SAR analysis was performed to further improve antiviral potency and to optimize drug-like properties of the initial hits. During our analysis, we identified 26, which was found to be nearly fourfold more potent than 1 against both vaccinia and La Crosse viruses. Selected compounds were further tested to more fully characterize the spectrum of antiviral activity. Many of these possessed single digit micromolar and sub-micromolar antiviral activity against a diverse array of targets, including influenza virus (Orthomyxoviridae), Tacaribe virus (Arenaviridae), and dengue virus (Flaviviridae).