Effects of ezetimibe/simvastatin on lipoprotein subfractions in patients with primary hypercholesterolemia: an exploratory analysis of archived samples using two commercially available techniques.
BACKGROUND
Cholesterol-rich lipoproteins, including low-density lipoprotein cholesterol (LDL-C), intermediate-density lipoprotein cholesterol (IDL-C), and very-low-density lipoprotein cholesterol (VLDL-C), are known to promote atherosclerosis. Ezetimibe/simvastatin (E/S) is an efficacious lipid-lowering treatment that inhibits both the intestinal absorption and biosynthesis of cholesterol.


OBJECTIVE
The aim of the current analysis was to compare the effects of ezetimibe and simvastatin monotherapy and E/S treatment on lipoprotein subfractions and LDL particle size in patients with primary hypercholesterolemia.


METHODS
This was an exploratory (hypothesis generating) analysis of archived plasma samples drawn from patients in a multicenter, randomized, double-blind, placebo-controlled, parallel-arm study. After a washout and diet/placebo run-in, patients with hypercholesterolemia (LDL-C, > or =145- < or =250 mg/dL; triglycerides, < or =350 mg/dL) were randomized equally to 1 of 10 daily treatments for 12 weeks: E/S (10/10, 10/20, 10/40, or 10/80 mg), simvastatin monotherapy (10, 20, 40, or 80 mg), ezetimibe monotherapy (10 mg), or placebo. A subset of patients had lipid subfraction measurements taken at baseline (week 0) and postrandomization (week 12). Plasma samples were used to quantify cholesterol associated with VLDL subfractions (VLDLI+2 and VLDL3), IDL, and 4 LDL subfractions (LDL1-4) via the Vertical Auto Profile II method. LDL-C particle size was determined using segmented gradient gel electrophoresis. The primary end point was median percent change in subfraction cholesterol for E/S versus ezetimibe or simvastatin monotherapy, pooled across doses.


RESULTS
Of the 1528 patients randomized in the original study, 1397 (91%) had lipid subfraction measurements taken. E/S was associated with significant reductions in VLDL-CI+2, VLDL-C3, IDL-C, LDL-C1, LDL-C2, and LDL-C3 versus ezetimibe, simvastatin, and placebo. E/S resulted in near-additive reductions in VLDL-CI+2, VLDL-C3, IDL-C, LDL-C1, LDL-C2, and LDL-C3 versus ezetimibe and simvastatin monotherapy. Of the subfractions examined, with regard to E/S, the greatest reductions were observed in IDL-C and LDL-C1, LDL-C2, and LDL-C3. When compared with placebo, ezetimibe, simvastatin, and E/S did not shift the distribution of LDL particles toward a larger, more buoyant LDL subclass pattern.


CONCLUSIONS
E/S was more effective than ezetimibe and simvastatin monotherapy in reducing atherogenic lipoprotein subfractions in these patients with primary hypercholesterolemia.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000924:Anticholesteremic Agents / Q000627:therapeutic use*; D001384:Azetidines / Q000627:therapeutic use*; D002784:Cholesterol / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D015243:Cholesterol, VLDL / Q000097:blood; D004311:Double-Blind Method; D004338:Drug Combinations; D023381:Endpoint Determination; D000069438:Ezetimibe; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use*; D006937:Hypercholesterolemia / Q000097:blood* / Q000188:drug therapy*; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010316:Particle Size; D019821:Simvastatin / Q000627:therapeutic use*
D000924:Anticholesteremic Agents; D001384:Azetidines; D008078:Cholesterol, LDL; D015243:Cholesterol, VLDL; D004338:Drug Combinations; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008074:Lipoproteins; D002784:Cholesterol; D019821:Simvastatin; D000069438:Ezetimibe