Rosenbaum, A. I.; Huang, Y.; Mu, R.; Kovacina, K.; Jin, C. D.; Hummer, B. T.; Liang, M.; Grimsby, J. S.

Background. Endothelial lipase (EL) promotes high-density lipoproteins (HDL) phospholipid degradation, increases catabolism of HDL and is an attractive target for the potential treatment for cardiovascular disease. Inhibition of EL using a monoclonal neutralizing antibody, MEDI5884, demonstrated increased quantity and function of HDL. Determinants of anti-atherosclerotic function of HDL comprise the interplay of various components of HDL structure-activity relationship: size, shape and composition (lipid and protein). Previous studies have shown that single doses of MEDI5884 administered to healthy nonhuman primates (NHPs) and healthy subjects resulted in a dose-dependent increase in plasma phospholipids (PL) and that plasma PI levels in placebo treated healthy subjects are significantly increased relative to CAD subjects participating in clinical trials NCT03001297 and NCT03351738, respectively. Methods: Herein, we characterized using LC-MS/MS the plasma lipidome of NHPs, heathy subjects and subjects with coronary artery disease (CAD) following MEDI5884 administration. Results: MEDI5884 treated NHPs resulted in a prominent increase in phosphatidylinositols (PI) and cholesteryl esters (CE). Treatment with MEDI5884 restores near-normal levels of PI in CAD patients. PI increases in both healthy subjects and CAD patients were dose-dependent, correlated with exposure and saturated at approximately 200 mg MEDI5884 subcutaneous (SC) dose in CAD patients. Comparison of pharmacodynamic (PD) effects of repeat SC 200 mg doses of MEDI5884 in CAD patients revealed greater and more rapid increases in PI levels compared to HDL-C and HDL phospholipid (HDL-PL). The increase in PI species was inversely correlated with decreases in free EL mass levels. Conclusions: PI has previously been shown to possess anti-atherosclerotic properties and led to increases in HDL cholesterol (HDL-C) and reverse cholesterol transport (RCT). The mechanism by which CE levels increase as the result of MEDI5884 administration can be attributed to the observed increase in both substrates of the lecithin-cholesterol acyltransferase (LCAT) reaction: phosphatidylcholine/phosphatidylethanolamine (PC/PE) and cholesterol as the consequence of EL inhibition. Further characterization of the underlying biological mechanisms responsible for the decrease of the PI biomarker in CAD patient population relative to healthy subjects as well as in conjunction with pharmacological intervention by MEDI5884 may reveal more information on this clinically-relevant biomarker and potential role in CAD.