Colesevelam hydrochloride: a specifically engineered bile acid sequestrant

Advances in the pharmacological management of hyperlipidemia through the use of combination therapies

INTRODUCTION

Lipid-lowering therapies are well established for the treatment of cardiovascular disease (CVD). Historically monotherapy studies have been performed, but the introduction of statins has led to these drugs being recognized as baseline therapies and to the investigation of combination therapy of both older and newer medications with them.

AREAS COVERED

Surrogate marker studies have shown additive effects on LDL-C, triglycerides and HDL-C of combination therapies with statins and these have extended to lipoprotein (a). Imaging studies have often shown benefits paralleling lipid studies. However, outcome studies have failed to show added benefits with niacin or fibrates while confirming the benefits of ezetimibe, bempedoic acid and proprotein convertase subtilisin kexin-9 (PCSK-9) inhibitors and icosapent ethyl.

EXPERT OPINION

Combination therapy for LDL-C in dual combinations is well validated. Data for intervention on triglycerides is limited to icosapent ethyl, but this may exert effects independent of lipids. New drugs targeting triglycerides through apolipoprotein C3 and angiopoietin-like peptides are in development. Studies on combination therapy raising HDL-C have generally disappointed, though cholesterol ester transfer protein (CETP) inhibition remains a target. Lipoprotein (a) is recognized as a CVD risk factor and effective therapies are in development but results on CVD events are lacking.

Colesevelam - a bile acid sequestrant for treating hypercholesterolemia and improving hyperglycemia

INTRODUCTION

Low density Lipoprotein cholesterol)LDL-C) levels show a clear relationship with cardiovascular disease (CVD). Statins are first line agents to reduce LDL-C and CVD risk. However, combination lipid-lowering therapy is often required to achieve large reductions in LDL-C.

AREA COVERED

Colesevelam HCl is a bile acid sequestrant (BAS), which reduces LDL-C by 16-22% in monotherapy and adds a further 12-14% reduction in LDL-C when combined with other lipid-lowering drugs. Like statins, colesevelam reduces C-reactive protein levels by 16% in monotherapy and additional 6% when added to statins. Colesevelam also reduced HbA_1c by 4mmol/mol (0.5%) when used alone and added to other hypoglycaemic drugs in studies of patients with diabetes .

EXPERT OPINION

Bile acid sequestrants reduce LDL-C and HbA_1c and have some CVD outcome evidence. The uses of these agents are limited in patients with gastrointestinal disease or high triglycerides due to adverse effects on gut function and raising triglycerides and they interfere with the absorption of lipid-soluble drugs. Colesevelam has a higher bile acid binding capacity, and fewer adverse effects than other BAS. Colesevelam may be useful as a third line agent for treatment of hypercholesterolemia with some additional specific benefits on glycemic control.

New therapies to reduce low-density lipoprotein cholesterol

PURPOSE OF REVIEW

Lipid-lowering is an intervention that reduces atherosclerosis and its complications. Statins currently form the standard of care but are not able to reduce low-density lipoprotein cholesterol (LDL-C) adequately in all patients - particularly those with familial hypercholesterolaemia and those with statin intolerance.

RECENT FINDINGS

Combination therapy with statins is well established and ezetimibe is often used as an additional LDL-C-lowering agent reducing LDL-C by 20%. However, its clinical efficacy still remains controversial. Newer, more potent methods of LDL-C reduction are in development. Both lomitapide, a microsomal transfer protein inhibitor (MTPI), and mipomersen, an antisense oligonucleotide (ASO), have been shown to improve LDL-C levels by 25-50% in patients with homozygous familial hypercholesterolaemia. In patients with heterozygous familial hypercholesterolaemia or statin intolerance antibody-based inhibitors of preprotein convertase subtilisin/kexin 9 (PCSK9) produce reductions in LDL-C of 30-65%. Cholesterol ester transfer protein inhibitors (CETPIs) reduce LDL-C by 30-40% as well as raising levels of high-density lipoprotein cholesterol (HDL-C) and may also have a role as additional LDL-C-reducing drugs.

SUMMARY

Surrogate outcome trials will be required with lomitapide or mipomersen to confirm their effects in homozygous familial hypercholesterolaemia and clinical endpoint trials will be needed for PCSK9 and CETPIs if these are to be used widely.

Lipid-lowering agents

The role of lipid lowering in reducing the risk of mortality and morbidity from cardiovascular disease (CVD) is well established. Treatment particularly aimed at decreasing low-density lipoprotein cholesterol (LDL-C) is effective in reducing the risk of death from coronary heart disease and stroke. Statins form the cornerstone of treatment. However, in some individuals with a high risk of CVD who are unable to achieve their target LDL-C due to either intolerance or lack of efficacy, there is the need for alternative therapies. This review provides an overview of the different classes of currently available lipid-lowering medications including statins, fibrates, bile acid sequestrants (resins), and omega-3 fatty acids. Data are presented on their indications, pharmacology, and the relevant end point clinical trial data with these drugs. It also discusses the human trial data on some novel therapeutic agents that are being developed including those for homozygous familial hypercholesterolemia--the antisense oligonucleotide mipomersen and the microsomal transfer protein inhibitor lomitapide. Data are presented on phase II and III trials on agents with potentially wider applications, cholesterol ester transfer protein inhibitors and proprotein convertase subtilisin kexin 9 inhibitors. The data on a licensed gene therapy for lipoprotein lipase deficiency are also presented.

Cholesterol, an essential molecule: diverse roles involving cytochrome P450 enzymes

Cholesterol is an essential molecule for eukaryotic life and is an important precursor for a wide range of physiological processes. Biosynthesis and homoeostasis of cholesterol are complex mechanisms that are tightly regulated and interlinked with activities of a number of cytochrome P450 enzymes. These P450s play central critical roles in cholesterol metabolism. Key roles include a rate-limiting reaction in the synthesis of cholesterol itself, and in the oxidative transformations of cholesterol into steroid hormones and bile acids. However, microbial P450s also have important roles that impinge directly on human cholesterol synthesis and oxidation. Recent data reveal that Mycobacterium tuberculosis (which infects more than one-third of the world's human population) uses P450s to initiate breakdown of host cholesterol as an energy source. Microbial P450s also catalyse industrially important transformations in the synthesis of cholesterol-lowering statin drugs, with clear benefits to humans. The present article reviews the various roles of P450s in human cholesterol metabolism, from endogenous P450s through to microbial oxidases that enable catabolism of human cholesterol, or facilitate production of statins that regulate cholesterol production with positive outcomes in cardiovascular disease.

New lipid-lowering drugs: an update

Lipid lowering is established as a proven intervention to reduce atherosclerosis and its complications. Statins form the basis of care but are not able to treat all aspects of dyslipidaemia. Many novel therapeutic compounds are being developed. These include additional therapeutics for low-density lipoprotein cholesterol, for example, thyroid mimetics (thyroid receptor beta-agonists), antisense oligonucleotides or microsomal transfer protein inhibitors (MTPI); triglycerides, for example, novel peroxosimal proliferator activating receptors agonists, MTPIs, diacylglycerol acyl transferase-1 inhibitors and high-density lipoprotein cholesterol (HDL-C), for example, mimetic peptides; HDL delipidation strategies and cholesterol ester transfer protein inhibitors and modulators of inflammation, for example, phospholipase inhibitors. Gene therapy for specific rare disorders, for example, lipoprotein lipase deficiency using alipogene tiparvovec is also in clinical trials. Lipid-lowering drugs are likely to prove a fast-developing area for novel treatments as possible synergies exist between new and established compounds for the treatment of atherosclerosis.

Colesevelam: in pediatric patients with heterozygous familial hypercholesterolemia

Colesevelam hydrochloride (colesevelam), a non-absorbed, synthetic, lipid-lowering polymer, is a bile acid sequestrant. Colesevelam binds with high affinity to bile acids within the gastrointestinal tract, thereby inhibiting the reabsorption of bile acids, resulting in decreases in serum low-density lipoprotein cholesterol (LDL-C) levels. Colesevelam is available as tablets and as powder for oral suspension. At dosages of 3.75 g once daily or 1.875 g twice daily, colesevelam is approved in the US for the treatment of pediatric patients aged 10-17 years with heterozygous familial hypercholesterolemia. Colesevelam may be administered as monotherapy or in combination with an HMG-CoA reductase inhibitor (statin). A 32-week trial was conducted and consisted of a stablilization period ( approximately 4 weeks), a randomized period (8 weeks), an open-label period (18 weeks), and a 2-week follow-up period. In the 8-week, randomized, double-blind, placebo-controlled period of the trial, colesevelam (tablets), as monotherapy or with a statin, was an effective treatment for pediatric patients with heterozygous familial hypercholesterolemia. At week 8, recipients of colesevelam 3.75 g/day had significant percentage reductions from baseline in mean LDL-C levels (primary endpoint) compared with placebo recipients. Significant beneficial treatment effects for colesevelam 3.75 g/day versus placebo were also reported for several other lipid/lipoprotein parameters at week 8 of the study. The reported treatment effects on lipid/lipoprotein parameters were maintained over a subsequent 18-week, open-label, noncomparative period, when all patients received colesevelam 3.75 g/day. Colesevelam 3.75 g/day was generally well tolerated for up to 26 weeks by pediatric patients with heterozygous familial hypercholesterolemia.