BZF961 + ritonavir

**BZF961 + ritonavir** is a fixed-dose investigational combination consisting of BZF961, a novel small molecule inhibitor of the hepatitis C virus (HCV) NS3-4A protease, and ritonavir, a cytochrome P450 3A4 inhibitor that boosts plasma concentrations of BZF961 by inhibiting its metabolic degradation. BZF961 shows antiviral activity by inhibiting the NS3-4A protease, essential for HCV replication. Ritonavir, though originally developed as an HIV protease inhibitor, serves in this combination to increase and stabilize BZF961 exposure rather than acting directly on HCV. This combination was investigated for the treatment of chronic hepatitis C, genotype 1. BZF961 was no longer under development as of 2018, primarily for strategic reasons rather than efficacy or safety issues[1][2].