[3] Development of the drug was abandoned in January 2011 due to concerns over the hepatic safety of almorexant after transient increases in liver enzymes were observed in trials.

[6] Originally developed by Actelion, from 2007 almorexant was being reported as a potential blockbuster drug, as its novel mechanism of action (orexin receptor antagonism) was thought to produce better quality sleep and fewer side effects than the traditional benzodiazepines and Z-drugs which dominated the multibillion-dollar insomnia medication market.

[7] In 2008, GlaxoSmithKline bought the development and marketing rights for almorexant from Actelion for an initial payment of $147 million.

[8] The deal would have been worth an estimated $3.2 billion if the drug had successfully completed clinical development and obtained FDA approval.

[9] GSK and Actelion continued to develop the drug together, and completed a Phase III clinical trial in November 2009.