Background: Despite favorable effects on high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol, the cholesteryl ester transfer protein inhibitor torcetrapib failed to slow atherosclerosis progression and increased mortality. We investigated the relationship between lipid changes and progression of coronary atherosclerosis.
Methods and results: Intravascular ultrasound was performed at baseline and follow-up in 910 participants randomized to torcetrapib/atorvastatin or atorvastatin monotherapy. The relationship between changes in lipoprotein levels and the primary intravascular ultrasound end point, change in percent atheroma volume, was investigated. Compared with atorvastatin monotherapy, torcetrapib raised HDL-C by 61%, lowered low-density lipoprotein cholesterol by 20%, raised serum sodium (0.44+/-0.14 mmol/L, P=0.02), and lowered serum potassium (0.11+/-0.02 mmol/L, P<0.0001). Despite substantial increases in HDL-C, no effect was found of torcetrapib on percent atheroma volume. In torcetrapib-treated patients, an inverse relationship was observed between changes in HDL-C and percentage atheroma volume (r=-0.17, P<0.001). Participants with regression had greater increases in HDL-C (mean+/-SE, 62.9+/-37.4% versus 54.0+/-39.1%, P=0.002). Compared with the lowest quartile, torcetrapib-treated patients in the highest quartile of HDL-C change showed the least progression (-0.31+/-0.27 versus 0.88+/-0.27%, P=0.001). The highest on-treatment HDL-C quartile showed significant regression of percent atheroma volume (-0.69+/-0.27%, P=0.01). In multivariable analysis, changes in HDL-C levels independently predicted the effect on atherosclerosis progression (P=0.001).
Conclusions: The majority of torcetrapib-treated patients demonstrated no regression of coronary atherosclerosis. Regression was only observed at the highest HDL-C levels. Torcetrapib raised serum sodium and lowered potassium, consistent with an aldosterone-like effect, which may explain the lack of favorable effects in the full study cohort. Accordingly, other cholesteryl ester transfer protein inhibitors, if they lack this off-target toxicity, may successfully slow atherosclerosis progression.
Trial registration: ClinicalTrials.gov NCT00134173.