-Disubstituted 4-Sulfamoylbenzoic Acid Derivatives as Inhibitors of Cytosolic Phospholipase A: Synthesis, Aqueous Solubility, and Activity in a Vesicle and a Whole Blood Assay.

Background: Cytosolic phospholipase A2α (cPLA) is the key enzyme that initiates the arachidonic acid cascade through which pro-inflammatory lipid mediators can be formed. Therefore, cPLA is considered an interesting target for the development of anti-inflammatory drugs. Although several effective inhibitors of the enzyme have been developed, none of them has yet reached clinical application.

Objective: Recently, we have prepared new 4-sulfamoylbenzoic acid derivatives based on a cPLA inhibitor found in a ligand-based virtual screening. The most effective of these compounds were now subjected to further variations in which the substitution pattern on the sulfamoyl nitrogen atom was changed..

Methods: The new compounds were tested in a vesicle assay for cPLA inhibition as well as for their water solubility, metabolic stability, and selectivity towards related enzymes. In addition, they were evaluated in a whole blood assay in which metabolites of the arachidonic acid cascade formed after activation of cPLA were quantified using a combined online dilution/ online solid phase extraction HPLC-MS method.

Results: Inhibitors with submicromolar inhibitory potency were found with favourable water solubility and selectivity. However, their efficacy did not match that of the highly effective, known, structurally related cPLA inhibitor giripladib, which was also tested as a reference. One advantage of some of the new compounds compared to giripladib was their significantly improved water solubility. When analyzing the substances in the whole blood assay, it was found that the obtained inhibition data correlated better with the results when the phorbol ester 12-Otetradecanoylphorbol- 13-acetate was used for activation of the enzyme in the blood cells instead of the calcium ionophore A23187.

Conclusion: New compounds with good activity towards cPLA and reasonable physicochemical properties were identified. Overall, the results obtained could be helpful in the development of clinically applicable inhibitors of this enzyme.