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Safety, Pharmacokinetics, and Pharmacodynamics of Single Doses of LXR-623, a Novel Liver X-Receptor Agonist, in Healthy Participants

From Early Development and Clinical Pharmacology (Dr Katz, Dr Udata, Ms Ott, Ms Hickey, Dr Meng), Biomarker Laboratory, Clinical Translational Medicine (Dr Burczynski, Dr Vesterqvist), and Bioanalytical R&D/Drug Metabolism (Mr Burghart), Wyeth Pharmaceuticals, Collegeville, Pennsylvania.

Liver X-receptor (LXR) agonists have been postulated to enhance reverse cholesterol transport (RCT), a process believed to shuttle cholesterol from the periphery back to the liver. Enhancing RCT via the upregulation of cholesterol transporters such as the adenosine triphosphate-binding cassettes ABCA1 and ABCG1 could therefore inhibit the progression of atherosclerosis. LXR-623 is a synthetic ligand for LXRs and β that has shown promise in animal models of atherosclerosis. The authors present results from a single ascending-dose study of the safety, pharmacokinetics, and pharmacodynamics of LXR-623 in healthy participants. LXR-623 was absorbed rapidly with peak concentrations (C_max) achieved at approximately 2 hours. The C_max and area under the concentration-time curve increased in a dose-proportional manner. The mean terminal disposition half-life was between 41 and 43 hours independently of dose. LXR activation resulted in a dose-dependent increase in ABCA1 and ABCG1 expression. The effect of LXR-623 concentration on ABCA1 and ABCG1 expression was further characterized via a population pharmacokinetic-pharmacodynamic analysis, yielding EC₅₀ estimates of 526 ng/mL and 729 ng/mL, respectively. Central nervous system-related adverse events were observed at the 2 top doses tested. The pharmacodynamic effects described here are the first demonstration of "target engagement" by an LXR agonist in humans.

Key Words: Liver X-receptor (LXR) • reverse cholesterol transport (RCT) • ATP-binding cassettes • ABCA1 • ABCG1 • population pharmacokinetics and pharmacodynamics

Address for reprints: Arie Katz, MD, 500 Arcola Road, A-3, Collegeville, PA 19426; e-mail: katza2{at}wyeth.com.

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