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 α 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 (Cmax) achieved at approximately 2 hours. The Cmax 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.