The development and testing of fenbufen

While looking for new and safer non-steroidal anti-inflammatory drugs (NSAID's) chemists at Lederle Laboratories isolated three compounds, on the basis of animal tests for anti-inflammatory activity, for further screening. Two of these turned out to be metabolites of the third. The parent drug, fenbufen, was found to be inactive in in vitro tests and was thought to be a pro-drug requiring metabolism to produce activity in vivo. This hypothesis has been shown to be correct and further toxicity testing and clinical trials have confirmed the low incidence of gastro-intestinal effects and clinical efficacy of fenbufen in osteo and rheumatoid arthritis.