Semagacestat (LY-450139) was a gamma secretase inhibitor being developed as a treatment for Alzheimer's disease by Eli Lilly. It was hoped that the drug would help to delay the onset of severe Alzheimer's disease, and thereby help preserve cognitive and executive functioning and in turn improve patient quality of life. Semagacestat (LY-450139) is designed to inhibit gamma secretase, an enzyme that is involved in the cleavage of APP to beta-amyloid. By decreasing production of beta-amyloid, it is hoped that gamma secretase inhibitors will exert a disease-modifying effect in Alzheimer's disease and thus slow or halt the destruction of nerve cells – the final stage in the amyloid cascade hypothesis. In March 2008 semagacestat (LY-450139) advanced to Phase III development, where it was evaluated in the IDENTITY (Interrupting Alzheimer's Dementia by EvaluatiNg Treatment of AmyloId PaThologY) trial, the first Phase III trial for this new anti-dementia drug. In August 2010, Eli Lilly announced its decision to halt the development of Semagacestat. The decision was taken after analysing the preliminary results of the second Phase III clinical trial of the drug, which indicated that semagacestat failed to slow disease progression. The drug, in fact, worsened cognition and the ability to perform day-to-day activities.