Fazamorexant (; developmental code name YZJ-1139) is an orexin receptor antagonist which is under development for the treatment of insomnia. It is taken by mouth.
The drug acts as a dual orexin receptor antagonist (DORA), or as an antagonist of both the orexin OX<sub>1</sub> and OX<sub>2</sub> receptors. Its time to peak levels is 0.6 to 1.3hours and its elimination half-life is 1.9 to 3.7hours.
Fazamorexant is under development by Jiangsu Yangtze River Pharmaceutical Group and/or Shanghai Haiyan Pharmaceutical Technology in China. As of September 2022, it is in phase 3 clinical trials for insomnia. Relatively little public information is available on fazamorexant. This was such that it had to be excluded from a 2020 literature review of orexin receptor antagonists for insomnia.