Reconstituted HDL elicits marked changes in plasma lipids following single-dose injection in C57Bl/6 mice.

High-density lipoprotein (HDL)-targeting therapies, including reconstituted HDL (rHDL), are attractive agents for treating dyslipidemia and atherosclerosis, as they may increase HDL levels and enhance therapeutic activities associated with HDL, including reverse cholesterol transport (RCT). Using CSL-111, a rHDL consisting of native human apolipoprotein AI (hApoAI) and phospholipids, we characterized the acute effects of rHDL administration in C57Bl/6 mice to (i) further our understanding of the mechanism of action of rHDL, and (ii) evaluate the usefulness of the mouse as a preclinical model for HDL-targeting therapies. After a single injection of CSL-111, there was a dose- and time-dependent increase of hApoAI, human pre-ß HDL, total cholesterol, and triglycerides in serum, consistent with the effects of CSL-111 in humans. However, unlike in humans, there was no measurable increase in cholesteryl esters. Evaluated ex vivo, the ATP binding cassette A1 (ABCA1)- and scavenger receptor type BI (SR-BI)-dependent cholesterol efflux capacity of serum from CSL-111-treated mice was increased compared with serum from vehicle-treated animals. Fractionation by size exclusion chromatography of lipoproteins in serum from treated mice revealed hApoAI in particles the size of endogenous HDL and slightly larger, cholesterol-enriched particles of all sizes, including sizes distinct from endogenous HDL or CSL-111 itself, and triglyceride-enriched particles the size of very-low-density lipoprotein (VLDL). These results suggest that in mouse blood CSL-111 is remodeled and generates enhanced cholesterol efflux capacity which increases mobilization of free cholesterol from peripheral tissues. Our findings complement the previous reports on CSL-111 in human participants and provide data with which to evaluate the potential utility of mouse models in mechanistic studies of HDL-targeting therapies.

Spiroimidazolidinone NPC1L1 inhibitors. Part 2: structure-activity studies and in vivo efficacy.

Ezetimibe (Zetia®), a cholesterol-absorption inhibitor (CAI) approved by the FDA for the treatment of hypercholesterolemia, is believed to target the intestine protein Niemann-Pick C1-Like 1 (NPC1L1) or its pathway. A spiroimidazolidinone NPC1L1 inhibitor identified by virtual screening showed moderate binding activity but was not efficacious in an in vivo rodent model of cholesterol absorption. Synthesis of analogs established the structure-activity relationships for binding activity, and resulted in compounds with in vivo efficacy, including 24, which inhibited plasma cholesterol absorption by 67% in the mouse, thereby providing proof-of-concept that non-ß-lactams can be effective CAIs.

Spiroimidazolidinone NPC1L1 inhibitors. 1: Discovery by 3D-similarity-based virtual screening.

A series of spiroimidazolidinone NPC1L1 inhibitors was discovered by virtual screening of the Merck corporate sample repository using 3D-similarity-based screening. Selection of 330 compounds for testing in an in vitro NPC1L1 binding assay yielded six hits in six distinct chemical series. Follow-up 2D similarity searching yielded several sub- to low-micromolar leads; among these was spiroimidazolidinone 10, with an IC(50) of 2.5 microM. Compound 10 provided a useful scaffold to initiate a medicinal chemistry campaign.