This open label long term safety and efficacy study (UX007G-CL202) will provide an opportunity for Glut 1 DS patients to be treated with UX007 for up to 3 years (or until market approval) under a single standardized protocol for maintenance therapy and consistent safety monitoring. The study is designed to obtain long-term safety information and evaluate maintenance of efficacy in a pediatric and adult Glut 1 DS population.