To investigate the efficacy and safety of SC‐58635 (celecoxib), an antiinflammatory and analgesic agent that acts by selective cyclooxygenase 2 (COX‐2) inhibition and is not expected to cause the typical gastrointestinal (GI), renal, and platelet‐related side effects associated with inhibition of the COX‐1 enzyme.

Four phase II trials were performed: a 2‐week osteoarthritis efficacy trial, a 4‐week rheumatoid arthritis efficacy trial, a 1‐week endoscopic study of GI mucosal effects, and a 1‐week study of effects on platelet function.

The 2 arthritis trials identified SC‐58635 dosage levels that were consistently effective in treating the signs and symptoms of arthritis and were distinguished from placebo on standard arthritis scales. In the upper GI endoscopy study, 19% of subjects receiving naproxen (6 of 32) developed gastric ulcers, whereas no ulcers occurred in subjects receiving SC‐58635 or placebo. The study of platelet effects revealed no meaningful effect of SC‐58635 on platelet aggregation or thromboxane B₂ levels, whereas aspirin caused significant decreases in 2 of 3 platelet aggregation measures and thromboxane B₂ levels. In all 4 trials, SC‐58635 was well tolerated, with a safety profile similar to that of placebo.

SC‐58635 achieves analgesic and antiinflammatory efficacy in arthritis through selective COX‐2 inhibition, without showing any evidence of 2 of the toxic effects of COX‐1 inhibition associated with nonsteroidal antiinflammatory drugs.