Our results indicate that reduced potency of sofosbuvir against genotype-3 HCV may have contributed to its limited efficacy in genotype-3 HCV patients,
and that ACH-3422 has greater potency against genotype-3 HCV suggesting the potential for improved clinical efficacy. Methods: Potency of ACH-3422 and sofosbuvir was assessed in parallel against HCV replicons with NS5B from representative geno-type-1 through genotype-4 strains. Potency was also compared against a panel of chimeric HCV replicons incorporating NS5B from genotype-3 clinical isolates. Results: ACH-3422 displayed an EC50 of 50 nM and a selective index of >500 in a cell line harboring a genotype-1b replicon. High potency was retained HM781-36B in vivo against a panel of replicons carrying NS5B from representative strains of genotypes 1 through 4. As compared to sofosbuvir, ACH-3422 exhibited 1-fold (genotype-2), 2-fold to 3-fold (genotypes 1a, 1b and 4) and 7-fold (genotype-3) higher potency. To confirm the significantly higher potency of ACH-3422 than sofosbuvir against genotype-3 NS5B, additional replicons incorporating NS5B from genotype-3 clinical isolates
were constructed and examined for mTOR inhibitor susceptibility. The results showed a consistently and significantly higher potency of ACH-3422 than sofosbuvir. Conclusions: ACH-3422 demonstrates as high as 7-fold greater potency than sofosbuvir against several gen-otype-3 clinical isolates in vitro. These results suggest that the combination of ACH-3422 and ribavirin for 12 weeks has the potential for improved efficacy over sofosbuvir in genotype-3 hepatitis C patients. Disclosures: selleck inhibitor Wengang Yang – Employment: Achillion Pharmaceuticals; Stock Shareholder: Achillion Pharmaceuticals Jason Wiles – Employment: Achillion Pharmaceuticals Mingjun Huang – Employment: Achillion Pharmaceuticals The following people have nothing to disclose: Yongsen Zhao, Steven Podos, Joanne L. Fabrycki, Dharaben Patel, Guangwei Yang, Avinash Phadke Background and Aims: Hepatitis C Virus (HCV) is a leading cause of chronic liver disease with an estimated 185 million people
affected globally. NS5A inhibitors are potent direct-acting antiviral agents (DAA) for HCV infection. However, earlier compounds suffered from a low genetic barrier to resistance in the clinic. We sought to identify a potent NS5A inhibitor with activity against all genotypes and previously identified resistance associated variants (RAVs). Methods: With the aid of a panel of sub-genomic and full-length replicon cell lines, NS5A lead inhibitors were iteratively optimized by monitoring potencies in replicons by qRT-PCR. Compounds with a higher genetic barrier were optimized based on their ability to inhibit all genotypes and previously described clinically relevant RAVs as well as suppress resistant colonies formation in replicons. Results: MK-8408 is a potent NS5A inhibitor with an EC50 <10 pM against HCV genotypes 1-6.