Simeprevir (Olysio™; Galexos™; Sovriad®) is an orally-administered NS3/4A protease inhibitor for use in combined drug regimens against chronic hepatitis C virus (HCV) infection. This article reviews studies relevant to the EU simeprevir label. In proof-of-concept studies, simeprevir had potent antiviral activity against all HCV genotypes, except genotype 3. In trials in patients with chronic HCV genotype 1 infection, week-12 sustained virological response (SVR12) rates in treatment-naïve patients and prior relapsers were significantly higher with simeprevir plus peginterferon-α/ribavirin (PR) [79–89 %] than with placebo plus PR (36–62 %). In prior partial/null responders, the SVR12 rate with simeprevir plus PR (54 %) was noninferior to that with telaprevir plus PR (55 %). Simeprevir plus PR was also efficacious in patients with HCV genotype 1/HIV-1 co-infection. In prior null responders without severe liver fibrosis (cohort 1) and treatment-naïve patients with severe liver fibrosis (cohort 2) treated with simeprevir plus sofosbuvir, the SVR12 rate for the two cohorts combined was 92 %. In patients with chronic HCV genotype 4 infection, the SVR12 rates with simeprevir plus PR were 83, 87 and 40 % in treatment-naïve patients, prior relapsers and prior null responders, respectively. Grade 3–4 adverse event, serious adverse event and treatment withdrawal rates with simeprevir plus PR were similar to those with placebo plus PR. Skin rashes with simeprevir were mostly mild or moderate; serious photosensitivity reactions occur, but are rare. Simeprevir is efficacious and generally well tolerated in patients with chronic HCV genotypes 1 and 4 infection. Studies of simeprevir in interferon-free regimens and in other subpopulations with HCV infections will be of interest.