The European Commission granted a marketing authorisation valid throughout the European Union for Daklinza (Daclatasvir) on 22 August 2014. Daclatasvir is an antiviral medicine used in combination with other medicines to treat chronic hepatitis C in adults. Daklinza must be used in combination with other medicines for chronic hepatitis C, such as sofosbuvir, peginterferon alfa and ribavirin. Daclatasvir blocks the action of a protein in the hepatitis C virus called ‘NS5A’, which is essential for the virus to multiply. By blocking this protein, the medicine stops the hepatitis C virus from multiplying. It is effective against genotypes 1 to 4. Daklinza used in combination with sofosbuvir (with or without ribavirin) was shown to be effective at clearing the hepatitis C virus from the blood in a main study involving 211 adults. The patients in the study were infected with genotypes 1, 2 or 3 and all received treatment for 12 or 24 weeks. Most patients had not previously been treated for hepatitis C, though some had genotype 1 infection that was resistant to standard medicines (consisting of either telaprevir or boceprevir – the so-called NS3/4A inhibitors – in combination with peginterferon alfa and ribavirin). Around 99% of patients with genotype 1 infection (125 out of 126), 96% of patients with genotype 2 infection (25 out of 26) and 89% of patients with genotype 3 infection (16 out of 18) did not show any sign of the virus in their blood 12 weeks after the end of their planned treatment. Additional studies involving patients with genotypes 4 indicate that Daklinza is also as effective against genotype 4 as it is against genotype 1. Fatigue (tiredness), nausea and headache the most common side effect.