The novel benzopyran class of selective cyclooxygenase-2 inhibitors. Part III: the three microdose candidates.

In this manuscript, we report the discovery of the substituted 2-trifluoromethyl-2H-benzopyran-3-carboxylic acids as a novel series of potent and selective cyclooxygenase-2 (COX-2) inhibitors. We provide the structure-activity relationships, optimization of design, testing criteria, and human half-life data. The challenge of a surprisingly long half-life (t(1/2)=360 h) of the first clinical candidate 1 and human t(1/2) had been difficult to predict based on allometric scaling for this class of highly ppb compounds. We used a microdose strategy which led to the discovery of clinical agents 18c-(S), 29b-(S), and 34b-(S) with human half-life of 57, 13, and 11 h.