Gaboxadol also known as 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP) is an experimental sleep aid drug developed by Lundbeck and Merck. In March, 2007, Merck and H. Lundbeck cancelled work on the drug, citing safety concerns and the failure of an efficacy trial. It acts on the GABA system, but in a very different way from benzodiazepines and Z-drugs (zolpidem, zaleplon, etc).[citation needed] Lundbeck states that gaboxadol also increases deep sleep (stage 4).