The European Commission granted a marketing authorisation valid throughout the European Union for Cosentyx on 15 January 2015. Cosentyx is a medicine used to treat moderate to severe plaque psoriasis (a disease causing red, scaly patches on the skin) in adults who require systemic (affecting the whole body) treatment. It contains the active substance secukinumab. The active substance in Cosentyx, secukinumab, is a monoclonal antibody. A monoclonal antibody is an antibodY that has been designed to recognize and attach to a specific structure (called an antigen) in the body. Secukinumab has been designed to attach to a cytokine (messenger molecule) in the immune system called interleukin 17A. This cytokine is involved in the inflammation and other immune system processes that cause psoriasis. By attaching to and blocking the action of interleukin 17A, secukinumab reduces the activity of the immune system and the symptoms of the disease. Cosentyx has been compared with placebo (a dummy treatment) in 4 main studies involving 2,403 patients with psoriasis, some of whom had had previous systemic treatments for the condition. The main measure of effectiveness of Cosentyx was improvement in the severity and extent of psoriasis after 12 weeks using two separate scoring systems (a 75% or more reduction in Psoriasis Area Severity Index [PASI] score, and a decrease of Investigator’s Global Assessment [IGA] score to 0 or 1 which indicates clear or nearly clear skin); in addition, in one study Cosentyx was compared with another authorised treatment for psoriasis, etanercept. The studies showed that Cosentyx is effective at improving the symptoms of psoriasis: taking the results of the 4 studies together, the percentage of patients achieving a 75% reduction in their PASI scores was 79% with Cosentyx, 44% with etanercept and 4% with placebo; with regard to IGA scores, 65% of patients given Cosentyx achieved a score of 0 or 1, compared with 27% of patients given etanercept and 2% of those given placebo. Benefits continued to be shown when treatment with Cosentyx was continued for up to 52 weeks. The most common side effects with Cosentyx (which may affect more than 1 in 10 people) are upper respiratory tract infections (colds) with inflammation of the nose and throat (nasopharyngitis) and blocked or runny nose (rhinitis). Because Cosentyx may increase the risk of infection, it must not be given to patients with serious active infections such as tuberculosis.