Anthranilic acid-based inhibitors of phosphodiesterase: design, synthesis, and bioactive evaluation.

Our previous studies identified two 2-benzoylaminobenzoate derivatives 1, which potently inhibited superoxide (O(2)˙(-)) generation induced by formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) in human neutrophils. In an attempt to improve their activities, a series of anthranilic acid derivatives were synthesized and their anti-inflammatory effects and underlying mechanisms were investigated in human neutrophils. Of these, compounds 17, 18, 46, 49, and 50 showed the most potent inhibitory effect on FMLP-induced release of O(2)˙(-) in human neutrophils with IC(50) values of 0.20, 0.16, 0.15, 0.06, and 0.29 µM, respectively. SAR analysis showed that the activities of most compounds were dependent on the ester chain length in the A ring. Conversely, a change in the linker between the A and B ring from amide to sulfonamide or N-methyl amide, as well as exchanges in the benzene rings (A or B rings) by isosteric replacements were unfavorable. Further studies indicated that inhibition of O(2)˙(-) production in human neutrophils by these anthranilic acids was associated with an elevation in cellular cAMP levels through the selective inhibition of phosphodiesterase 4. Compound 49 could be approved as a lead for the development of new drugs in the treatment of neutrophilic inflammatory diseases.

Pharmacokinetics, biodistribution and toxicology following intravenous and oral administration of DSM-RX78 and EFB-1, two new 2-(2-fluorobenzamido)benzoate-based PDE4 inhibitors, to rats.

OBJECTIVES: The aim of this study was to determine the pharmacokinetic profile, biodistribution and toxicity of ethyl 2-(2-fluorobenzamido)benzoate (EFB-1) and methyl 2-(2-fluorobenzamido)benzoate (DSM-RX 78), two phosphodiesterase IV inhibitors, which potently attenuate haemorrhagic shock-induced lung injury in rat. METHODS: Quantification of DSM-RX78, EFB-1 and 2-(2-fluorobenzamido)benzoate (SMP-3) in plasma was carried out by HPLC. Furthermore, the pharmacokinetics and biodistribution of intravenously (1.0 and 3.0 mg/kg) and orally (40.0 mg/kg) administered DSM-RX78, EFB-1, and SMP-3 were determined in Sprague-Dawley rats. Toxicity and histological analyses were also evaluated herein. KEY FINDINGS: A liquid chromatography method has been developed for the quanification of EFB-1, DSM-RX78 and SMP-3 in rat plasma. The method was sensitive with good linearity (r(2) = 0.9990) over a range of 1.56-0.0975 µg/ml. The mean kinetic parameters of DSM-RX 78 and EFB-1 following intravenous administration were as follows: elimination half-life (t½) 8.98 and 8.77 min; clearance (Cl) 24.57 and 22.31 ml/min/kg; AUC(0-) (∞) 41.76 and 48.03 min mg/l. CONCLUSIONS: The pharmacokinetics, toxicity and biodistribution of DSM-RX78 and EFB-1 were determined for the first time. The results showed that the pharmacokinetic profiles of DSM-RX78 and EFB-1 were similar, and that EFB-1 had a better safety profile than DSM-RX78. Therefore, EFB-1 was suitable as a lead compound for the development of new agents in the treatment of neutrophilic inflammatory diseases.