Evaluation of ITX 5061, a scavenger receptor B1 antagonist: resistance selection and activity in combination with other hepatitis C virus antivirals.

ITX 5061 is a scavenger receptor B1 antagonist that has entered phase 1 clinical trials in hepatitis C virus (HCV)-infected humans. We evaluated ITX 5061 in combination with interferon-α, ribavirin, and HCV protease and polymerase inhibitors in a genotype 2a infectious virus system. ITX 5061 is a potent inhibitor of HCV replication and is additive to synergistic with interferon-α, ribavirin, BILN2061, VX950, VX1, and 2'-C-methyladenosine. Resistance selection experiments were performed using a Jc1-FEO virus co-culture system and intermittent ITX 5061 exposure under neomycin selection. We identified a mutant virus with a substitution of aspartic acid for asparagine at the highly conserved position 415 in E2 (N415D). Introduction of this mutation into wild-type virus conferred high-level resistance to ITX 5061. There was no cross-resistance between ITX 5061 and HCV protease inhibitors or interferon-α. These results suggest that ITX 5061 is a promising compound for study in combination with other HCV inhibitors.