Fazamorexant (INNTooltip International Nonproprietary Name; developmental code name YZJ-1139) is an orexin receptor antagonist which is under development for the treatment of insomnia.

[1] The drug acts as a dual orexin receptor antagonist (DORA), or as an antagonist of both the orexin OX1 and OX2 receptors.

[2][3] Fazamorexant is under development by Jiangsu Yangtze River Pharmaceutical Group and/or Shanghai Haiyan Pharmaceutical Technology in China.

[1][4][2] As of September 2022, it is in phase 3 clinical trials for insomnia.

[2] This was such that it had to be excluded from a 2020 literature review of orexin receptor antagonists for insomnia.