Synthesis, structure - Activity relationships, and in vivo evaluations of substituted di-tert-butylphenols as a novel class of potent, selective, andorally active cyclooxygenase-2 inhibitors. 1. Thiazolone and oxazolone series

Selective cyclooxygenase-2 (COX-2) inhibitors have been shown to be potent antiinflammatory agents with fewer side effects than currently marketed non steroidal antiinflammatory drugs (NSAIDs). Initial mass screening and subse quent structure-activity relationship (SAR) studies have identified 4b (PD1 38387) as the most potent and selective COX-2 inhibitor within the thiazolo ne and oxazolone series of di-tert-butylphenols. Compound 4b has an IC50 Of 1.7 mu M against recombinant human COX-2 and inhibited COX-2 activity in t he J774A.1 cell line with an IC50 of 0.17 mu M. It was inactive against pur ified ovine COX-1 at 100 mu M and did not inhibit COX-1 activity in platele ts at 20 mu M. Compound 4b was also orally active in vivo with an ED40 of 1 6 mg/kg in the carrageenan footpad edema (CFE) assay and caused no gastroin testinal (GI) damage in rats at the dose of 100 mg/kg but inhibited gastric prostaglandin E-2 (PGE(2)) production in rats' gastric mucosa by 33% follo wing a dose of 100 mg/kg. The SAR studies of this chemical series revealed that the potency and selectivity are very sensitive to minor structural cha nges. A simple isosteric replacement led to the reversal of selectivity.