A study of long-term safety and tolerability of Sage-718 in participants with Huntington's disease (H-54042)

Sage Therapeutics, Inc. is sponsoring this study of an investigational drug called SAGE-718.  SAGE-718 is being evaluated for possible development in several brain disorders, including for the potential treatment of mild cognitive impairment (involving mental activities like thinking, learning, decision-making, and remembering) and dementia. Dementia is a condition in the brain that affects memory, thinking, decision-making, and social abilities, and can disrupt normal daily activities.  

SAGE-718 is a unique modulator (regulator of activity) of N-methyl-D-aspartate (NMDA) receptors. NMDA receptors are a type of protein with an important role in the ability of nerve cells to communicate with each other. Preliminary data suggest that lowered NMDA receptor tone may contribute to cognitive dysfunction in HD. SAGE-718 is a novel, first-in-class modulator (regulator of activity) of NMDA receptors. 

The main purpose of this study is to:  Evaluate the safety and tolerability of SAGE-718 in subjects with HD.