MK8742 is a potent and selective inhibitor of hepatitis C virus (HCV) NS5A protein, which plays a critical role in viral replication and assembly. It is primarily used as an antiviral agent in the treatment of chronic HCV infection. Due to its high potency, MK8742 has been developed as part of combination therapies, often paired with other direct-acting antivirals such as NS3/4A protease inhibitors or NS5B polymerase inhibitors, to enhance treatment efficacy and reduce the risk of drug resistance. Its use contributes to high rates of sustained virologic response (SVR), effectively curing many patients of HCV with shorter treatment durations and fewer side effects compared to older interferon-based regimens. MK8742 has been a key component in modern all-oral, interferon-free treatment regimens for multiple HCV genotypes.