Cipralisant

Cipralisant (GT-2331, tentative trade name Perceptin) is an extremely potent Histamine H₃ receptor ligand originally developed by Gliatech. Cipralisant was initially classified as a selective H₃ antagonist, but newer research (2005) suggests also agonist properties, i. e. functional selectivity. Cipralisant seemed to be well tolerated during early testing, entering Phase II trials for ADHD in 2000.

The relatively recent cloning of human H₃ receptor, as well as the discovery of its constitutive activity provided the ability to better assess the activity of H₃ receptor ligands. Consequently, cipralisant was reassessed as an H₃ receptor agonist in human and rat recombinant systems, showing functional selectivity and stimulating one type of G-protein coupled pathway while failing to activate other intracellular pathways.

Gliatech filed for bankruptcy in 2002, and its intellectual property was inherited by Merck. The development of cipralisant seems to have been suspended since 2003 but research is ongoing, and recently it has been shown that it is the (1S,2S)-enantiomer which is the biologically active one.