New-generation therapies for hepatitis C virus (HCV) have been wildly successful – so much so that they've caused a conundrum at market leader Gilead Sciences Inc., whose drugs Harvoni (ledipasvir 90 mg/sofosbuvir 400 mg), Sovaldi (sofosbuvir 400 mg) and Epclusa (sofosbuvir 400 mg/velpatasvir 100 mg) have produced high cure rates in patients with chronic HCV, leading to slumping sales. (See BioWorld Today, May 3, 2017.)