Niacin extended-release/simvastatin

New opportunities in the management and treatment of refractory hypercholesterolemia using in vivo CRISPR-mediated genome/base editing

AIMS

Refractory hypercholesterolemia (RH), caused primarily by the loss-of-function mutation of LDL receptor (LDLR) gene seen in HoFH and HeFH patients, remains a major risk factor for atherosclerotic cardiovascular disease (ASCVD). Statin and ezetimibe combination therapy lower circulating LDL by 30% in HoFH patients. PCSK9 mAB, being an LDLR-dependent therapy, is not effective in HoFH, but lowers LDL by 25% in HeFH patients. A maximum reduction of 50% was noted in HoFH patients treated with ANGPTL3 mAB, which was not enough to achieve therapeutic goal of LDL. Therefore, new approaches are warranted to offer hopes to individuals intolerant to higher dose statins and not able to achieve recommended LDL level.

DATA SYNTHESIS

New approaches to lower LDL include gene therapy and gene editing. AAV-based gene therapy has shown encouraging results in animal models. Using CRISPR/Cas9-mediated genome/base editing, gain of function and loss of function have been successfully done in animal models. Recent progress in the refinement of genome/base editing has overcome the issues of off-target mutagenesis with ∼1% mutagenesis in case of PCSK9 and almost no off-target mutagenesis in inactivating ANGPTL3 in animal models showing 50% reduction in cholesterol. Current approaches using CRISPR-Cas9 genome/base editing targeting LDLR-dependent and LDLR-independent pathways are underway.

CONCLUSIONS

The new information on gain of LDLR function and inactivation of ANGPTL3 together with developments in genome/base editing technology to overcome off-target insertion and deletion mutagenesis offer hope to refractory hypercholesterolemic individuals who are at a higher risk of developing ASCVD.

A Review of Progress on Targeting LDL Receptor-Dependent and -Independent Pathways for the Treatment of Hypercholesterolemia, a Major Risk Factor of ASCVD

Since the discovery of the LDL receptor in 1973 by Brown and Goldstein as a causative protein in hypercholesterolemia, tremendous amounts of effort have gone into finding ways to manage high LDL cholesterol in familial hypercholesterolemic (HoFH and HeFH) individuals with loss-of-function mutations in the LDL receptor (LDLR) gene. Statins proved to be the first blockbuster drug, helping both HoFH and HeFH individuals by inhibiting the cholesterol synthesis pathway rate-limiting enzyme HMG-CoA reductase and inducing the LDL receptor. However, statins could not achieve the therapeutic goal of LDL. Other therapies targeting LDLR include PCSK9, which lowers LDLR by promoting LDLR degradation. Inducible degrader of LDLR (IDOL) also controls the LDLR protein, but an IDOL-based therapy is yet to be developed. Among the LDLR-independent pathways, such as angiopoietin-like 3 (ANGPTL3), apolipoprotein (apo) B, apoC-III and CETP, only ANGPTL3 offers the advantage of treating both HoFH and HeFH patients and showing relatively better preclinical and clinical efficacy in animal models and hypercholesterolemic individuals, respectively. While loss-of-LDLR-function mutations have been known for decades, gain-of-LDLR-function mutations have recently been identified in some individuals. The new information on gain of LDLR function, together with CRISPR-Cas9 genome/base editing technology to target LDLR and ANGPTL3, offers promise to HoFH and HeFH individuals who are at a higher risk of developing atherosclerotic cardiovascular disease (ASCVD).

Effects of Extended-Release Niacin and Extended-Release Niacin/Laropiprant on the Pharmacokinetics of Simvastatin in Healthy Subjects

The use of multiple lipid-modifying agents with different mechanisms of action is often required to regulate lipid levels in patients with dyslipidemia. During combination therapy, alterations in the pharmacokinetics of any of the drugs used and their metabolites may occur. Three separate open-label, randomized, crossover studies evaluated the potential for pharmacokinetic interaction between extended-release niacin (with and without concomitant laropiprant) and simvastatin in healthy subjects. Study 1 used single doses of extended-release niacin and simvastatin; study 2 used multiple-dose coadministration of extended-release niacin/laropiprant and simvastatin in healthy subjects; and study 3 used single doses of both extended-release niacin and the coadministration of extended-release niacin/laropiprant and simvastatin in healthy Chinese subjects. During each treatment period, plasma samples were collected predose and at prespecified postdose time points for pharmacokinetic analyses. The safety and tolerability of simvastatin with and without coadministered extended-release niacin (or extended-release niacin/laropiprant) were assessed by clinical evaluation of adverse experiences. In 2 studies in healthy subjects, modest increases in exposure to simvastatin acid (by ∼60%) by extended-release niacin and extended-release niacin/laropiprant were observed. Based on the clinical experience with simvastatin, these effects are not believed to be clinically meaningful. In the third study on healthy Chinese subjects, no statistically meaningful increases in exposure to simvastatin by extended-release niacin and extended-release niacin/laropiprant were observed. In all populations examined in these studies, the coadministration of extended-release niacin and simvastatin was generally well tolerated.

Gender differences in pharmacokinetics of a combination tablet of niacin extended-release/simvastatin in healthy Chinese volunteers

The gender differences in pharmacokinetics of a combination tablet of niacin extended-release/simvastatin were evaluated in healthy Chinese volunteers. Thirty-six healthy male and female volunteers were enrolled in the study receiving a single oral dose of niacin extended-release/simvastatin 1,000/20 mg. The results indicated that the systemic exposure of simvastatin hydroxy acid and the total urine excretion of niacin were significantly higher for females compared with those for males, and the T max of niacin in plasma was significantly shorter for males than that for females. There were no significant differences in the systemic exposure of simvastatin, niacin, and NUA in plasma between males and females.

Niacin Reduces Atherosclerosis Development in APOE*3Leiden.CETP Mice Mainly by Reducing NonHDL-Cholesterol

Objective

Niacin potently lowers triglycerides, mildly decreases LDL-cholesterol, and largely increases HDL-cholesterol. Despite evidence for an atheroprotective effect of niacin from previous small clinical studies, the large outcome trials, AIM-HIGH and HPS2-THRIVE did not reveal additional beneficial effects of niacin (alone or in combination with laropiprant) on top of statin treatment. We aimed to address this apparent discrepancy by investigating the effects of niacin without and with simvastatin on atherosclerosis development and determine the underlying mechanisms, in APOE*3Leiden.CETP mice, a model for familial dysbetalipoproteinemia (FD).

Approach and Results

Mice were fed a western-type diet containing cholesterol without or with niacin (120 mg/kg/day), simvastatin (36 mg/kg/day) or their combination for 18 weeks. Similarly as in FD patients, niacin reduced total cholesterol by -39% and triglycerides by −50%, (both P<0.001). Simvastatin and the combination reduced total cholesterol (−30%; −55%, P<0.001) where the combination revealed a greater reduction compared to simvastatin (−36%, P<0.001). Niacin decreased total cholesterol and triglycerides primarily by increasing VLDL clearance. Niacin increased HDL-cholesterol (+28%, P<0.01) and mildly increased reverse cholesterol transport. All treatments reduced monocyte adhesion to the endothelium (−46%; −47%, P<0.01; −53%, P<0.001), atherosclerotic lesion area (−78%; −49%, P<0.01; −87%, P<0.001) and severity. Compared to simvastatin, the combination increased plaque stability index [(SMC+collagen)/macrophages] (3-fold, P<0.01). Niacin and the combination reduced T cells in the aortic root (−71%, P<0.01; −81%, P<0.001). Lesion area was strongly predicted by nonHDL-cholesterol (R² = 0.69, P<0.001) and to a much lesser extent by HDL-cholesterol (R² = 0.20, P<0.001).

Conclusion

Niacin decreases atherosclerosis development mainly by reducing nonHDL-cholesterol with modest HDL-cholesterol-raising and additional anti-inflammatory effects. The additive effect of niacin on top of simvastatin is mostly dependent on its nonHDL-cholesterol-lowering capacities. These data suggest that clinical beneficial effects of niacin are largely dependent on its ability to lower LDL-cholesterol on top of concomitant lipid-lowering therapy.

Biased Ligands for Better Cardiovascular Drugs

Drug discovery efforts targeting G-protein-coupled receptors (GPCR) have been immensely successful in creating new cardiovascular medicines. Currently marketed GPCR drugs are broadly classified as either agonists that activate receptors or antagonists that prevent receptor activation by endogenous stimuli. However, GPCR couple to a multitude of intracellular signaling pathways beyond classical G-protein signals, and these signals can be independently activated by biased ligands to vastly expand the potential for new drugs at these classic targets. By selectively engaging only a subset of a receptor's potential intracellular partners, biased ligands may deliver more precise therapeutic benefit with fewer side effects than current GPCR-targeted drugs. In this review, we discuss the history of biased ligand research, the current understanding of how biased ligands exert their unique pharmacology, and how research into GPCR signaling has uncovered previously unappreciated capabilities of receptor pharmacology. We focus on several receptors to illustrate the approaches taken and discoveries made, and how these are steadily illuminating the intricacies of GPCR pharmacology. Discoveries of biased ligands targeting the angiotensin II type 1 receptor and of separable pharmacology suggesting the potential value of biased ligands targeting the β-adrenergic receptors and nicotinic acid receptor GPR109a highlight the powerful clinical promise of this new category of potential therapeutics.

Extended-release niacin (nicotinic acid)/laropiprant

Extended-release (ER) niacin (nicotinic acid)/laropiprant is a once-daily fixed-dose combination tablet that has been evaluated (with or without an HMG-CoA reductase inhibitor [statin]) in the treatment of adults with dyslipidaemia or primary hypercholesterolaemia. Niacin (vitamin B3) is a lipid-modifying drug and laropiprant is an anti-flushing agent, which reduces flushing induced by niacin. In a randomized, double-blind, placebo-controlled, multicentre, 24-week trial, a significant (p < 0.001) reduction (18.4%) in plasma low-density lipoprotein cholesterol (LDL-C) levels (primary endpoint) was achieved with ER niacin/laropiprant 2000 mg/40 mg once daily (after an initial 4-week 1000 mg/20 mg once-daily regimen) compared with placebo (weeks 12-24) in adults with primary hypercholesterolaemia or mixed dyslipidaemia. ER niacin/laropiprant 2000 mg/40 mg plus simvastatin 20 mg or 40 mg once daily (after an initial 4-week lower-dose regimen) produced significant (p < 0.05) improvements, from baseline, in LDL-C levels (primary endpoint) compared with once-daily ER niacin/laropiprant 2000 mg/40 mg or simvastatin alone at week 12 in a randomized, double-blind, multicentre, factorial trial in adults with primary hypercholesterolaemia or mixed dyslipidaemia. The incidence and intensity of flushing (an efficacy endpoint) were significantly (p < 0.05) reduced with ER niacin/laropiprant compared with ER niacin in randomized trials. ER niacin/laropiprant, alone or in combination with a statin, was generally well tolerated for up to 24 weeks by adults with dyslipidaemia or primary hyercholesterolaemia.