Simeprevir is primarily used in the treatment of chronic hepatitis C virus (HCV) infection. It is often prescribed in combination with other antiviral medications, such as sofosbuvir or ribavirin, to enhance its effectiveness. This drug works by inhibiting the HCV NS3/4A protease enzyme, which is essential for viral replication. By blocking this enzyme, simeprevir helps reduce the viral load in the body, improving liver function and decreasing the risk of liver damage, cirrhosis, or liver cancer. It is particularly effective against HCV genotype 1 and, in some cases, genotype 4. Treatment regimens involving simeprevir are tailored to the patient’s specific condition, including prior treatment history and the presence of liver cirrhosis. Its use has significantly improved cure rates for hepatitis C, offering a shorter treatment duration and fewer side effects compared to older therapies. However, it is important to monitor for potential drug interactions and adverse effects during treatment.