Trofinetide is in clinical development for the treatment of females with Rett syndrome (RTT). RTT is a rare genetic disorder that affects brain development, resulting in severe mental and physical disability. In RTT, a protein called insulin-like growth factor 1 (IGF1) in the brain is lower than normal and it is thought that nerve function is affected as a result. It is characterised by loss of speech and regression of acquired skills between 6 and 18 months of age. The disease severity varies in affected people, and whilst many may reach adulthood, some people die at a young age as a result of several complications. There is currently no approved medicines for RTT. Trofinetide is made up of a molecule derived from IGF-1. It is an oral medicinal product expected to restore IGF-1 activity in the brain, thus restoring normal functioning of brain cells and improving the symptoms of the disease. If licensed, Trofinetide would become the first therapy approved for treatment of RTT patients.