[1][2] Emixustat was invented by the British-American chemist, Ian L. Scott, and is currently in Phase 3 trials for dry, age-related macular degeneration (AMD).

[6] In 2008, Acucela Inc. partnered with Otsuka Pharmaceutical Company for the development of emixustat (ACU-4429) in an agreement totaling $263 million in cash and milestone payments.

[7] Emixustat hydrochloride is a non-retinoid small molecule inhibitor of RPE65 (retinal pigment epithelium-specific 65 kDa protein, also known as retinoid isomerohydrolase).

These cells account for approximately 95% of human photoreceptors, and turn over cis to trans retinol constantly under normal lighting conditions.

[11] In a completed Phase 1a study, the drug was "well tolerated" by male and female human participants, and demonstrated dose-dependent modulation of electroretinogram (ERG) signals.

[12] A Phase II study, completed in 2015, produced a dose dependent, reversible effect on rod function consistent with emixustat's planned mechanism of action.