Design, synthesis, and anti-inflammatory evaluation of a series of novel amino acid-binding 1,5-diarylpvrazole derivatives

Aim: To design and synthesize a series of novel amino acid-binding 1,5-diarylpyrazole derivatives, which are intended to act as prodrugs with better aqueous solubility than celecoxib, and which will exert potent anti-inflammatory activities after being converted to their parent compounds in vivo. Methods: To introduce an amino acid, celecoxib analogs containing amino or methylamino group were synthesized first through multi-step chemical reactions. All the synthesized compounds were screened in an intact cell-based assay in vitro and in carrageenan-induced mouse paw edema in vivo. Some active compounds were selected for further evaluation in a carrageenan-induced rat paw edema model. The preliminary pharmacokinetics, experiments were conducted using high performance liquid chromatography/mass spectrometry (HPLC/MS). Results: Celecoxib, 6 of the 1,5-diarylpyrazole class of celecoxib analogs, and their amino acid derivatives (hydrochloride salts) were synthesized. In vitro screening, the hydrochloride salts showed decreased inhibitory effects on cyclooxygenase (COX)-1 and COX-2 compared with their parent compounds, but some exhibited potent anti-inflammatory activity in vivo. Compound 4a was selected for further evaluation, and its anti-inflammatory effect was equivalent to that of celecoxib after oral administration in the carrageenan-induced rat paw edema model. At three doses (25 mg/kg, 50 mg/kg, and 100 mg/kg) the percentage inhibition on edema was 20.7%, 52.6%, and 62.6% (for compound 4a) and 27.8%, 38.4%, and 40.1% (for celecoxib), respectively. Preliminary pharmacokinetic evaluations support the hypothesis that compound 4a was actually converted to its parent compound, compound 4. Conclusion: The compound bound with amino acid acts like prodrug, which can exert anti-inflammatory effect similar to celecoxib after being converted to its parent compound. This finding will be of great benefit in carrying out structural modifications of prodrug-like selective COX-2 inhibitors.