Changes in lipoprotein subfraction concentration and composition in healthy individuals treated with the CETP inhibitor anacetrapib.

We investigated the effects of the cholesteryl ester (CE) transfer protein inhibitor anacetrapib (ANA) on plasma lipids, lipoprotein subfraction concentrations, and lipoprotein composition in 30 healthy individuals. Participants (n = 30) were randomized to ANA 20 mg/day, 150 mg/day, or placebo for 2 weeks. Changes in concentration of lipoprotein subfractions were assessed using ion mobility, and compositional analyses were performed on fractions separated by density gradient ultracentrifugation. ANA 150 mg/day versus placebo resulted in significant decreases in LDL-cholesterol (26%) and apo B (29%) and increases in HDL-cholesterol (82%). Concentrations of medium and small VLDL, large intermediate density lipoprotein (IDL), and medium and small LDL (LDL2a, 2b, and 3a) decreased whereas levels of very small and dense LDL4b were increased. There was enrichment of triglycerides and reduction of CE in VLDL, IDL, and the densest LDL fraction. Levels of large buoyant HDL particles were substantially increased, and there was enrichment of CE, apo AI, and apoCIII, but not apoAII or apoE, in the mid-HDL density range. Changes in lipoprotein subfraction concentrations and composition with ANA 20 mg/day were similar to those for ANA 150 mg/day but were generally smaller in magnitude. The impact of these changes on cardiovascular risk remains to be determined.

The effects of laropiprant, a selective prostaglandin D2 receptor 1 antagonist, on the antiplatelet activity of clopidogrel or aspirin.

Laropiprant (LRPT) is being developed in combination with Merck's extended-release niacin (ERN) formulation for the treatment of dyslipidemia. LRPT, an antagonist of the prostaglandin PGD2 receptor DP1, reduces flushing symptoms associated with ERN. LRPT also has affinity for the thromboxane A2 receptor TP (approximately 190-fold less potent at TP compared with DP1). Aspirin and clopidogrel are two frequently used anti-clotting agents with different mechanisms of action. Since LRPT may potentially be co-administered with either one of these agents, these studies were conducted to assess the effects of steady-state LRPT on the antiplatelet activity of steady-state clopidogrel or aspirin. Bleeding time at 24 h post-dose (trough) was pre-specified as the primary pharmacodynamic endpoint in both studies. Two separate, double-blind, randomized, placebo-controlled, crossover studies evaluated the effects of multiple-dose LRPT on the pharmacodynamics of multiple-dose clopidogrel or aspirin. Healthy subjects were randomized to once-daily oral doses of LRPT 40 mg or placebo to LRTP co-administered with clopidogrel 75 mg or aspirin 81 mg for 7 days with at least a 21-day washout between treatments. In both studies, bleeding time and platelet aggregation were assessed 4 and 24 hours post-dose on Day 7. Comparability was declared if the 90% confidence interval for the estimated geometric mean ratio ([LRPT+clopidogrel]/clopidogrel alone or [LRPT+aspirin]/aspirin alone) for bleeding time at 24 hours post-dose on Day 7 was contained within (0.66, 1.50). Concomitant daily administration of LRPT 40 mg with clopidogrel 75 mg or aspirin 81 mg resulted in an approximate 4-5% increase in bleeding time at 24 hours after the last dose vs. bleeding time after treatment with clopidogrel or aspirin alone, demonstrating that the treatments had comparable effects on bleeding time. Percent inhibition of platelet aggregation was not significantly different between LRPT co-administered with clopidogrel or aspirin vs. clopidogrel or aspirin alone at 24 hours post-dose at steady state. At 4 hours after the last dose, co-administration of LRPT 40 mg resulted in 3% and 41% increase in bleeding time vs. bleeding time after treatment with aspirin or clopidogrel alone, respectively. Co-administration of LPRT with clopidogrel or aspirin was generally well tolerated in healthy subjects. Co-administration of multiple doses of LRPT 40 mg and clopidogrel 75 mg or aspirin 81 mg had no clinically important effects on bleeding time or platelet aggregation.