Investigational therapies for the treatment of atherosclerosis

Regulation of liver X receptor target genes by 22-functionalized oxysterols. Synthesis, in silico and in vitro evaluations

The endogenous oxysterol 22(R)-hydroxycholesterol (22RHC, 1) is an LXR agonist which upregulates genes of critical involvement in human cholesterol- and lipid metabolism. In contrast, its synthetic epimer 22(S)-hydroxycholesterol (22SHC, 8) has shown specific antagonistic effects in recent studies, avoiding unwanted side effects provided by potent LXR agonists. In terms of LXR modulation, the aim of this study was to compare 22SHC (8), 22RHC (1) and synthesized ligands with keto- and amide functionality in the 22nd position of the cholesterol scaffold. 22SHC (8) and 22RHC (1) performed as expected while 22-ketocholesterol (22KC, 10) revealed an attractive in vitro profile for further investigation in terms of anti-atherosclerotic properties as selective upregulation of the ATP-binding cassette transporter ABCA1 was observed. A new synthesized amide derivate, Fernholtz cyclohexylamide (13) was shown to reduce lipogenesis in a dose-responsive manner and abolish the effect of the potent LXR agonist T0901317 when administered simultaneously.

Transporters for the Intestinal Absorption of Cholesterol, Vitamin E, and Vitamin K

Humans cannot synthesize fat-soluble vitamins such as vitamin E and vitamin K. For this reason, they must be obtained from the diet via intestinal absorption. As the deficiency or excess of these vitamins has been reported to cause several types of diseases and disorders in humans, the intestinal absorption of these nutrients must be properly regulated to ensure good health. However, the mechanism of their intestinal absorption remains poorly understood. Recent studies on cholesterol using genome-edited mice, genome-wide association approaches, gene mutation analyses, and the development of cholesterol absorption inhibitors have revealed that several membrane proteins play crucial roles in the intestinal absorption of cholesterol. Surprisingly, detailed analyses of these cholesterol transporters have revealed that they can also transport vitamin E and vitamin K, providing clues to uncover the molecular mechanisms underlying the intestinal absorption of these fat-soluble vitamins. In this review, we focus on the membrane proteins (Niemann-Pick C1 like 1, scavenger receptor class B type I, cluster of differentiation 36, and ATP-binding cassette transporter A1) that are (potentially) involved in the intestinal absorption of cholesterol, vitamin E, and vitamin K and discuss their physiological and pharmacological importance. We also discuss the related uncertainties that need to be explored in future studies.

Distribution of Estimated 10-Year Risk of Recurrent Vascular Events and Residual Risk in a Secondary Prevention Population

Background:

Among patients with clinically manifest vascular disease, the risk of recurrent vascular events is likely to vary. We assessed the distribution of estimated 10-year risk of recurrent vascular events in a secondary prevention population. We also estimated the potential risk reduction and residual risk that can be achieved if patients reach guideline-recommended risk factor targets.

Methods:

The SMART score (Second Manifestations of Arterial Disease) for 10-year risk of myocardial infarction, stroke, or vascular death was applied to 6904 patients with vascular disease. The risk score was externally validated in 18 436 patients with various manifestations of vascular disease from the TNT (Treating to New Targets), IDEAL (Incremental Decrease in End Points Through Aggressive Lipid Lowering), SPARCL (Stroke Prevention by Aggressive Reduction in Cholesterol Levels), and CAPRIE (Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events) trials. The residual risk at guideline-recommended targets was estimated by applying relative risk reductions from meta-analyses to the estimated risk for targets for systolic blood pressure, low-density lipoprotein cholesterol, smoking, physical activity, and use of antithrombotic agents.

Results:

The external performance of the SMART risk score was reasonable, apart from overestimation of risk in patients with 10-year risk >40%. In patients with various manifestations of vascular disease, median 10-year risk of a recurrent major vascular event was 17% (interquartile range, 11%–28%), varying from <10% in 18% to >30% in 22% of the patients. If risk factors were at guideline-recommended targets, the residual 10-year risk would be <10% in 47% and >30% in 9% of the patients (median, 11%; interquartile range, 7%–17%).

Conclusions:

Among patients with vascular disease, there is very substantial variation in estimated 10-year risk of recurrent vascular events. If all modifiable risk factors were at guideline-recommended targets, half of the patients would have a 10-year risk <10%. These data suggest that even with optimal treatment, many patients with vascular disease will remain at >20% and even >30% 10-year risk, clearly delineating an area of substantial unmet medical need.

Targeting PCSK9 as a promising new mechanism for lowering low-density lipoprotein cholesterol

Statins and other lipid-lowering drugs have dominated the market for many years for achievement of recommended levels of low-density lipoprotein cholesterol (LDL-C). However, a substantial number of high-risk patients are unable to achieve the LDL-C goal. Proprotein convertase subtilisin/kexin 9 (PCSK9) has recently emerged as a new, promising key therapeutic target for hypercholesterolemia. PCSK9 is a protease involved in chaperoning the low-density lipoprotein receptor to the process of degradation. PCSK9 inhibitors and statins effectively lower LDL-C. The PCSK9 inhibitors decrease the degradation of the LDL receptors, whereas statins mainly interfere with the synthetic machinery of cholesterol by inhibiting the key rate limiting enzyme, the HMG CoA reductase. PCSK9 inhibitors are currently being developed as monoclonal antibodies for their primary use in lowering LDL-C. They may be especially useful for patients with homozygous familial hypercholesterolemia, who at present receive minimal benefit from traditional statin therapy. The monoclonal antibody PCSK9 inhibitors, recently granted FDA approval, show the most promising safety and efficacy profile compared to other, newer LDL-C lowering therapies. This review will primarily focus on the safety and efficacy of monoclonal antibody PCSK9 inhibitors in comparison to statins. The review will also address new, alternative PCSK9 targeting drug classes such as small molecules, gene silencing agents, apolipoprotein B antisense oligonucleotides, and microsomal triglyceride transfer protein inhibitors.