Characterization of Anacetrapib Distribution into the Lipid Droplet of Adipose Tissue in Mice and Human Cultured Adipocytes

Abstract

Anacetrapib is an inhibitor of cholesteryl ester transfer protein (CETP), associated with reduction in LDL cholesterol and increase in HDL cholesterol in hypercholesterolemic patients. Anacetrapib was not taken forward into filing/registration as a new drug for coronary artery diease, despite the observation of a ∼9% reduction in cardiovascular risk in a large phase III cardiovascular outcomes trial (REVEAL). Anacetrapib displayed no adverse effects throughout extensive preclinical safety evaluation, and no major safety signals were observed in clinical trials studying anacetrapib, including REVEAL. However, anacetrapib demonstrated a long terminal half-life in all species, thought to be due, in part, to distribution into adipose tissue. We sought to understand the dependence of anacetrapib's long half-life on adipose tissue and to explore potential mechanisms that might contribute to the phenomenon. In mice, anacetrapib localized primarily to the lipid droplet of adipocytes in white adipose tissue; in vitro, anacetrapib entry into cultured human adipocytes depended on the presence of a mature adipocyte and lipid droplet but did not require active transport. In vivo, the entry of anacetrapib into adipose tissue did not require lipase activity, as the distribution of anacetrapib into adipose was-not affected by systemic lipase inhibition using poloaxamer-407, a systemic lipase inhibitor. The data from these studies support the notion that the entry of anacetrapib into adipose tissue/lipid droplets does not require active transport, nor does it require mobilization or entry of fat into adipose via lipolysis.

HDL therapy today: from atherosclerosis, to stent compatibility to heart failure

“…Among cholesteryl ester transfer protein (CETP) inhibitors, markedly raising HDL-C, only anacetrapib in the large REVEAL study did reduce CV risk by approximately 10%, but certain safety concerns associated to the drug [38]. in particular a very long half-life and prolonged permanence in tissues, consequent to a direct uptake by the adipocytes [39], led to drug discontinuation. Trials with this drug class well support the notion of quality vs quantity of HDL particle levels [40].…”

Impact of drug distribution into adipose on tissue function: The cholesteryl ester transfer protein (CETP) inhibitor anacetrapib as a test case

“…The 30% reduction in food/calorie intake was associated with a ~18% reduction in body weight and a ~7% lower total fat mass in food restricted mice vs ad lib‐fed DIO mice. The epididymal fat pads were selected since previous studies examining anacetrapib deposition into adipose tissue utilized this fat pad to assess anacetrapib concentrations in white adipose tissue, however, this fat pad weight did not change in response to food restriction. The retroperitoneal fat pad was studied, since previous studies examining various mechanisms of weight loss, including caloric restriction, elicited a reduction in retroperitoneal fat pad weight.…”

“…For studies to determine the effect of anacetrapib treatment on adipose functionality, mice were treated with 100 mg/kg anacetrapib, dosed in feed, or control DIO diet for 20 weeks. Epididymal and retroperitoneal white adipose tissue (eWAT and rWAT, respectively) and blood were collected from N = 4 animals at weeks 1,4,8,12,14,18, and 20, following overnight fasting. The tissues were inspected visually for the presence of any adherent connective tissue, which was carefully removed, and briefly washed in PBS before tissues were snap-frozen.…”

“…We previously reported that anacetrapib levels accumulate in adipose tissue of mice and remain relatively unchanged throughout a 35‐week washout period . Recently, we reported that anacetrapib distributes into the lipid droplet of adipose tissue, via mechanisms independent of active transport or lipase activity . Given the prolonged presence of anacetrapib in the lipid droplet of adipocytes, and long elimination phase of anacetrapib from adipose, adipose tissue may represent a depot for anacetrapib.…”

The role of the adipose tissue microenvironment in kidney cancer

“…For example, a promising anti-cardiovascular disease agent, anacetrapib, was retained in the adipose tissue, inducing a prolonged and unwanted half-life. The drug was, therefore, banned from entering the market [163]. In the case of cancer chemotherapy, adipocytes were able to quickly absorb and catabolise daunorubicin into daunorubicinol which had less cytotoxicity [164].…”