Vol. 53, Issue 2, 322-329, February 1998

-Lactams SB 212047 and SB 216754 Are Irreversible, Time-Dependent Inhibitors of Coenzyme A-Independent Transacylase

James D. Winkler, Chiu-Mei Sung, Marie Chabot-Flecher, Don E. Griswold, Lisa A. Marshall, Floyd H. Chilton, William Bondinell, and Ruth J. Mayer

Departments of Immunopharmacology (J.D.W., C.-M.S., M.C.-F., D.E.G., L.A.M., R.J.M.) and Medicinal Chemistry (W.B.), SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, and Section on Pulmonary and Critical Care Medicine and Department of Biochemistry (F.H.C.), Bowman Gray School of Medicine, Winston-Salem, North Carolina 27103

The enzyme coenzyme A-independent transacylase (CoA-IT) has been demonstrated to be the key mediator of arachidonate remodeling, a process that moves arachidonate into 1-ether-containing phospholipids. Blockade of CoA-IT by reversible inhibitors has been shown to block the release of arachidonate in stimulated neutrophils and inhibit the production of eicosanoids and platelet-activating factor. We describe novel inhibitors of CoA-IT activity that contain a -lactam nucleus. -Lactams were investigated as potential mechanism-based inhibitors of CoA-IT on the basis of the expected formation of an acyl-enzyme intermediate complex. Two -lactams, SB 212047 and SB 216754, were shown to be specific, time-dependent inhibitors of CoA-IT activity (IC₅₀ = 6 and 20 µM, respectively, with a 10-min pretreatment time). Extensive washing and dilution could not remove the inhibition, suggesting it was irreversible. In stimulated human monocytes, SB 216754 decreased the production of eicosanoids in a time-dependent manner. In an in vivo model of phorbol ester-induced ear inflammation, SB 216754 was able to inhibit indices of both edema and cell infiltration. Taken together, the results support two hypotheses: 1) CoA-IT activity is important for the production of inflammatory lipid mediators in stimulated cells and in vivo and 2) the mechanism by which CoA-IT acts to transfer arachidonate is through an acyl-enzyme intermediate.