On 21 November 2013, after an accelerated examination of the dossier, the Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Sovaldi (sofosbuvir) 400 mg film-coated tablet intended for the treatment of Chronic Hepatitis C (CHC). The European Commission granted a marketing authorization valid throughout the European Union for Sovaldi on 16 January 2014. The drug, classified as antiviral for system use, blocks the action of an enzyme called ‘NS5B RNA-dependent RNA polymerase’ in the hepatitis C virus, which is essential for the virus to multiply. This stops the hepatitis C virus from multiplying and infecting new cells. Sofosbuvir works against all genotypes of the hepatitis C virus. The main results come from four different studies called Neutrino, Fission, Positron e Fusion involving a total of 1305 patients infected with hepatitis C. In all four studies, the main measure of effectiveness was the number of patients whose blood tests did not show any sign of hepatitis C virus 12 weeks after the end of treatment. Sovaldi is indicated in combination with other medicinal products. The most common side effects with Sofosbuvir in combination with ribavirin and peginterferon alfa were similar to those commonly reported with ribavirin or peginterferon alfa and included fatigue (tiredness), headache, nausea (feeling sick) and insomnia. Sofosbuvir did not increase the frequency or severity of these side effects.