Rolipram

Rolipram is a selective phosphodiesterase-4 inhibitor discovered and developed by Schering AG as a potential antidepressant drug in the early 1990s. It served as a prototype molecule for several companies' drug discovery and development efforts. Rolipram was discontinued after clinical trials showed that its therapeutic window was too narrow; it could not be dosed at high enough levels to be effective without causing significant gastrointestinal side effects.