Tenidap ([Z]-5-chloro-2,3-dihydro-3-[hydroxy-2-thienylmethylene]-2-oxo-1H-indole-1-carboxamide) is an oxindole derivative, a COX/5-LOX inhibitor and cytokine-modulating anti-inflammatory drug candidate that was under development by Pfizer as a promising potential treatment for rheumatoid arthritis. Tenidap shows potent inhibition of cyclooxygenase in vitro, that is of several magnitudes greater than 5-lipoxygenase inhibition. Lipoxygenase inhibition, however, has been difficult to document in vivo because Tenidap is highly protein bound and free drug concentrations are below those necessary for 5-lipoxygenase inhibition. However, several in-vitro activities distinguish Tenidap from conventional cyclooxygenase inhibitors. As shown with stimulated human neutrophils, tenidap inhibits activation of collagenase, lysosomal enzyme secretion, and superoxide generation, as well as aggregation and adhesion to endothelium. Furthermore, unlike Non-steroidal anti-inflammatory drugs (NSAIDs), it lowers circulating C-reactive protein (CRP) concentrations by a magnitude equivalent to hydroxychloroquine and auranofin. This result suggests an effect on the synthesis and/or release of the cytokines known to induce the acute-phase protein response-namely, IL-1, IL-6, and TNF-alpha. Tenidap, like existing second-line drugs, lowers serum IL-6 concentrations, a property not shared by NSAIDs The cytokine inhibitory effect also includes reduced in-vitro concentrations of TNF-alpha and IL-1 from both RA synovium and peripheral blood mononuclear cells. There is no immunosuppressive effect of Tenidap in either animal or clinical studies. In clinical studies. The comparisons between tenidap and other second-line agents show that Tenidap produced a faster reduction in CRP than Auranofin. The rate of withdrawal because of inefficacy was similar (18-20%) in Auranofin and Tenidap groups. The quality of life using the arthritis impact measurement scales has also been assessed Scores were better with tenidap than with NSAID monotherapy, but equivalent to the second line plus NSAID combinations. Tenidap is registered in the United States, Netherlands, and Italy but is not marketed because marketing approval was rejected by the FDA in 1996 due to liver and kidney toxicity, which was attributed to metabolites of the drug with a thiophene moiety that caused oxidative damage.