Update of HDL in atherosclerotic cardiovascular disease

Epidemiologic evidence supported an inverse association between HDL (high-density lipoprotein) cholesterol (HDL-C) levels and atherosclerotic cardiovascular disease (ASCVD), identifying HDL-C as a major cardiovascular risk factor and postulating diverse HDL vascular- and cardioprotective functions beyond their ability to drive reverse cholesterol transport. However, the failure of several clinical trials aimed at increasing HDL-C in patients with overt cardiovascular disease brought into question whether increasing the cholesterol cargo of HDL was an effective strategy to enhance their protective properties. In parallel, substantial evidence supports that HDLs are complex and heterogeneous particles whose composition is essential for maintaining their protective functions, subsequently strengthening the "HDL quality over quantity" hypothesis. The following state-of-the-art review covers the latest understanding as per the roles of HDL in ASCVD, delves into recent advances in understanding the complexity of HDL particle composition, including proteins, lipids and other HDL-transported components and discusses on the clinical outcomes after the administration of HDL-C raising drugs with particular attention to CETP (cholesteryl ester transfer protein) inhibitors.

The effect of CETP inhibitors on new-onset diabetes: a systematic review and meta-analysis

BACKGROUND

Despite the increasing prevalence of type 2 diabetes mellitus (T2DM), limited pharmacologic options are available for prevention. Cholesteryl ester transfer protein inhibitors (CETPis) have been studied primarily as a therapy to reduce cardiovascular disease, but have also been shown to reduce new-onset diabetes. As new trial data have become available, this meta-analysis examines the effect of CETP inhibitors on new-onset diabetes and related glycaemic measures.

METHODS AND RESULTS

We searched MEDLINE, EMBASE, and Cochrane databases (all articles until 4 March, 2021) for randomised controlled trials (RCT) ≥1-year duration, with at least 500 participants, comparing CETPi to placebo, and that reported data on new-onset diabetes or related glycaemic measures [haemoglobin A1C (HbA1C), fasting plasma glucose, insulin, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR)]. A fixed effects meta-analysis model was applied to all eligible studies to quantify the effect of CETPi therapy on new-onset diabetes. Four RCTs (n = 75 102) were eligible for quantitative analysis of the effect of CETPi on new-onset diabetes. CETPis were found to significantly decrease the risk of new-onset diabetes by 16% (RR: 0.84; 95% CI: 0.78, 0.91; P < 0.001), with low between-trial heterogeneity (I2 = 4.1%). Glycaemic measures were also significantly improved or trended towards improvement in those with and without diabetes across most trials.

CONCLUSION

Although RCTs have shown mixed results regarding the impact of CETPi on cardiovascular disease, they have shown a consistent reduction in the risk of new-onset diabetes with CETPi therapy. Future trials of CETPis and potentially other HDL-raising agents should therefore specify new-onset diabetes and reversal of existing T2DM as secondary endpoints.

Increasing HDL levels by inhibiting cholesteryl ester transfer protein activity in rabbits with hindlimb ischemia is associated with increased angiogenesis

BACKGROUND

High density lipoprotein (HDL) infusions increase new blood vessel formation (angiogenesis) in rodents with ischemic injury. This study asks if increasing HDL levels by inhibiting cholesteryl ester transfer protein (CETP) activity increases angiogenesis in New Zealand White (NZW) rabbits with hindlimb ischemia.

METHODS AND RESULTS

NZW rabbits were maintained for 6weeks on chow or chow supplemented with 0.07% or 0.14% (wt/wt) of the CETP inhibitor, des-fluoro-anacetrapib. The left femoral artery was ligated after 2weeks of des-fluoro-anacetrapib treatment. The animals were sacrificed 4weeks after femoral artery ligation. Treatment with 0.07% and 0.14% (wt/wt) des-fluoro-anacetrapib reduced CETP activity by 63±12% and 81±8.6%, increased plasma apoA-I levels by 1.3±0.1- and 1.4±0.1-fold, and increased plasma HDL-cholesterol levels by 1.4±0.1- and 1.7±0.2-fold, respectively. Treatment with 0.07% and 0.14% (wt/wt) des-fluoro-anacetrapib increased the number of collateral arteries by 60±16% and 84±27%, and arteriole wall area in the ischemic hindlimbs by 84±16% and 94±13%, respectively. Capillary density in the ischemic hindlimb adductor muscle increased from 1.1±0.2 (control) to 2.1±0.3 and 2.2±0.4 in the 0.07% and 0.14% (wt/wt) des-fluoro-anacetrapib-treated animals, respectively. Incubation of HDLs from des-fluoro-anacetrapib-treated animals with human coronary artery endothelial cells at apoA-I concentrations comparable with their plasma levels increased tubule network formation. These effects were abolished by knockdown of scavenger receptor-B1 (SR-B1) and PDZK1, and pharmacological inhibition of PI3K/Akt.

CONCLUSION

Increasing HDL levels by inhibiting CETP activity is associated with increased collateral blood vessel formation in NZW rabbits with hindlimb ischemia in an SR-B1- and PI3K/Akt-dependent manner.

Evaluation of lipids, drug concentration, and safety parameters following cessation of treatment with the cholesteryl ester transfer protein inhibitor anacetrapib in patients with or at high risk for coronary heart disease

The aim of this study was to assess the effects on lipids and safety during a 12-week reversal period after 18 months of treatment with anacetrapib. The cholesteryl ester transfer protein inhibitor anacetrapib was previously shown to reduce low-density lipoprotein cholesterol by 39.8% (estimated using the Friedewald equation) and increase high-density lipoprotein (HDL) cholesterol by 138.1%, with an acceptable side-effect profile, in patients with or at high risk for coronary heart disease in the Determining the Efficacy and Tolerability of CETP Inhibition With Anacetrapib (DEFINE) trial. A total of 1,398 patients entered the 12-week reversal-phase study, either after completion of the active-treatment phase or after early discontinuation of the study medication. In patients allocated to anacetrapib, placebo-adjusted mean percentage decreases from baseline were observed at 12 weeks off the study drug for Friedewald-calculated low-density lipoprotein cholesterol (18.6%), non-HDL cholesterol (17.6%), and apolipoprotein B (10.2%); placebo-adjusted mean percentage increases were observed for HDL cholesterol (73.0%) and apolipoprotein A-I (24.5%). Residual plasma anacetrapib levels (about 40% of on-treatment apparent steady-state trough levels) were also detected 12 weeks after cessation of anacetrapib. No clinically important elevations in liver enzymes, blood pressure, electrolytes, or adverse experiences were observed during the reversal phase. Preliminary data from a small cohort (n = 30) revealed the presence of low concentrations of anacetrapib in plasma 2.5 to 4 years after the last anacetrapib dose. In conclusion, after the cessation of active treatment, anacetrapib plasma lipid changes and drug levels decreased to approximately 40% of on-treatment trough levels at 12 weeks after dosing, but modest HDL cholesterol elevations and low drug concentrations were still detectable 2 to 4 years after the last dosing.

Anacetrapib, a cholesterol ester transfer protein (CETP) inhibitor for the treatment of atherosclerosis

Anacetrapib, under development by Merck & Co Inc, is an inhibitor of the cholesterol ester transfer protein (CETP) for the treatment of atherosclerosis. By reversibly increasing the affinity of CETP for lipoprotein particles, anacetrapib inhibits CETP-mediated cholesterol exchange, resulting in elevated HDL-cholesterol levels and reductions in LDL-cholesterol levels. In phase I and II clinical trials, anacetrapib was well tolerated and, unlike the now discontinued CETP inhibitor torcetrapib, did not affect blood pressure and aldosterone levels. The impact of anacetrapib on lipoprotein parameters was superior to that of the CETP inhibitors torcetrapib and dalcetrapib. However, while anacetrapib displays promising anti-arteriosclerotic properties, the long-term safety and tolerability of the agent remains to be evaluated. Moreover, the concept that inhibiting CETP is atheroprotective is yet to be proven. The future of CETP inhibitors has also been affected by the failure of torcetrapib, which increased mortality in a phase III trial. Results from an ongoing phase III trial of anacetrapib will determine the likely future development of not only anacetrapib, but of the pharmacological class of CETP inhibitors.