Therapeutic Management of Familial Hypercholesterolemia: Current and Emerging Drug Therapies

Development and Clinical Applications of Antisense Oligonucleotide Gapmers

DNA-like molecules called antisense oligonucleotides have opened new treatment possibilities for genetic diseases by offering a method of regulating gene expression. Antisense oligonucleotides are often used to suppress the expression of mutated genes which may interfere with essential downstream pathways. Since antisense oligonucleotides have been introduced for clinical use, different chemistries have been developed to further improve efficacy, potency, and safety. One such chemistry is a chimeric structure of a central block of deoxyribonucleotides flanked by sequences of modified nucleotides. Referred to as a gapmer, this chemistry produced promising results in the treatment of genetic diseases. Mipomersen and inotersen are examples of recent FDA-approved antisense oligonucleotide gapmers used for the treatment of familial hypercholesterolemia and hereditary transthyretin amyloidosis, respectively. In addition, volanesorsen was conditionally approved in the EU for the treatment of adult patients with familial chylomicronemia syndrome (FCS) in 2019. Many others are being tested in clinical trials or under preclinical development. This chapter will cover the development of mipomersen and inotersen in clinical trials, along with advancement in gapmer treatments for cancer, triglyceride-elevating genetic diseases, Huntington's disease, myotonic dystrophy, and prion diseases.

Therapeutic Options for Homozygous Familial Hypercholesterolemia: The Role of Lomitapide

Background:

Lomitapide (Juxtapid® in US and Lojuxta® in Europe) is the first developed inhibitor of the Microsomal Triglyceride Transfer Protein (MTP) approved as a novel drug for the management of Homozygous Familial Hypercholesterolemia (HoFH). It acts by binding directly and selectively to MTP thus decreasing the assembly and secretion of the apo-B containing lipoproteins both in the liver and in the intestine.

Aims:

The present review aims at summarizing the recent knowledge on lomitapide in the management of HoFH.

Results:

The efficacy and safety of lomitapide have been evaluated in several trials and it has been shown a reduction of the plasma levels of Low-Density Lipoprotein Cholesterol (LDL-C) by an average of more than 50%. Although the most common side effects are gastrointestinal and liver events, lomitapide presents generally with a good tolerability and satisfactory patients compliance. Recently, in Europe, to evaluate the long-term safety and efficacy of lomitapide, the LOWER registry (ClinicalTrials.gov Identifier: NCT02135705) has been established in order to acquire informations on HoFH lomitapidetreated patients from “real life” clinical practice.

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Furthermore, the observation that lomitapide decreases triglyceride levels may be considered for patients affected by severe forms of hypertriglyceridemia who undergo recurrent episodes of pancreatitis and are poor responders to conventional treatment.

Conclusion:

Lomitapide represents an innovative and efficacious drug for the treatment of HoFH. Longterm safety data, treatment of pediatric and pregnant HoFH patients and management of severe hypertriglyceridemia still require further investigations.

Familial Hypercholesterolemia: New Horizons for Diagnosis and Effective Management

Familial hypercholesterolemia (FH) is a common genetic cause of premature cardiovascular disease (CVD). The reported prevalence rates for both heterozygous FH (HeFH) and homozygous FH (HoFH) vary significantly, and this can be attributed, at least in part, to the variable diagnostic criteria used across different populations. Due to lack of consistent data, new global registries and unified guidelines are being formed, which are expected to advance current knowledge and improve the care of FH patients. This review presents a comprehensive overview of the pathophysiology, epidemiology, manifestations, and pharmacological treatment of FH, whilst summarizing the up-to-date relevant recommendations and guidelines. Ongoing research in FH seems promising and novel therapies are expected to be introduced in clinical practice in order to compliment or even substitute current treatment options, aiming for better lipid-lowering effects, fewer side effects, and improved clinical outcomes.

Preventing cardiovascular heart disease: Promising nutraceutical and non-nutraceutical treatments for cholesterol management

Hypercholesterolemia is one of the major risk factors for the development of cardiovascular disease. Atherosclerosis resulting from hypercholesterolemia causes many serious cardiovascular diseases. Statins are generally accepted as a treatment of choice for lowering low-density lipoprotein (LDL) cholesterol, which reduces coronary heart disease morbidity and mortality. Since statin use can be associated with muscle problems and other adverse symptoms, non-adherence and discontinuation of statin therapy often leads to inadequate control of plasma cholesterol levels and increased cardiovascular risk. Moreover, there is compelling evidence on the presence of still considerable residual cardiovascular risk in statin-treated patients. Ezetimibe improves cholesterol-lowering efficacy and provides mild additional cardiovascular protection when combined with statin treatment. Despite a favorable safety profile compared to statins, ezetimibe-induced cholesterol-lowering is modest when used alone. Hence, there is a critical need to identity additional effective hypolipidemic agents that can be used either in combination with statins, or alone, if statins are not tolerated. Thus, hypolipidemic agents such as proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, apolipoprotein B-100 antisense oligonucleotides, cholesteryl ester transfer protein (CETP) inhibitors, and microsomal triglyceride transfer protein (MTTP) inhibitors, as well as yeast polysaccharides (beta-glucans and mannans) and compounds derived from natural sources (nutraceuticals) such as glucomannans, plant sterols, berberine, and red yeast rice are being used. In this review, we will discuss hypercholesterolemia, its impact on the development of cardiovascular disease (CVD), and the use of yeast polysaccharides, various nutraceuticals, and several therapeutic agents not derived from 'natural' sources, to treat hypercholesterolemia.

Citrus junos Tanaka peel ameliorates hepatic lipid accumulation in HepG2 cells and in mice fed a high-cholesterol diet

Background

Citrus junos Tanaka (yuja), a yellow-coloured citrus fruit has traditionally been consumed in Korea, Japan, and China and has been found effective in preventing certain diseases. However, the inhibitory effect of yuja on hepatic lipid accumulation has not been clearly elucidated thus far.

Methods

The inhibitory effect of yuja on hepatic lipid accumulation was investigated in both cell culture and mouse models. We investigated the inhibitory effect of ethanol extract of yuja peel (YE) using HepG2 cells. We next confirmed the effect of YE in mice fed a high cholesterol diet. Animals were divided into 4 groups (n = 8): a normal diet group (ND), a high-cholesterol diet group (HC), high-cholesterol diet plus 1% YE (YL), high-cholesterol diet plus 5% YE (YH).

Result

Seventy percent ethanolic extracts of yuja peel (YE) reduced oleic acid-induced hepatic lipid accumulation in HepG2 cells. Treatment with YE at 100, 200 μg/mL up-regulated expression levels of cholesterol metabolism-related proteins such as AMPK, ACC, PPAR-α, and CPT1 and down-regulated the expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase. The hypocholesterolemic effect of YE was further confirmed in mice fed a high-cholesterol diet. Compared to ND (normal diet) mice, HC (high-cholesterol diet) mice showed increased body weight, liver fat content, liver weight, and content of total cholesterol and low-density lipoprotein (LDL) cholesterol. On the contrary, administrations of YL (HC + 1% YE) or YH (HC + 5% YE) significantly reduced body weight, liver fat content, liver weight, total cholesterol, and LDL cholesterol compared to those of only HC fed mice group. As a result of in vitro data, protein expressions of PPAR-α and CPT1 were induced in mice fed YE diet compared to HC diet but HMGCR expression was decreased.

Conclusions

Yuja peel ameliorates hepatic lipid accumulation in both cell culture and mouse models and therefore, could serve as a useful supplement for hypercholesterolemia.

Variable phenotypic expression of nonsense mutation p.Thr5* in the APOE gene

Subjects with hypercholesterolemia who do not carry a mutation in the low density lipoprotein receptor gene, in the apolipoprotein B gene or in the proprotein convertase subtilisin/kexin type 9 gene, could possible carry a mutation in the apolipoprotein E (APOE) gene. DNA from 844 unrelated hypercholesterolemic subjects who did not carry a mutation in any of the three above mentioned genes, was subjected to DNA sequencing of the APOE gene. Two subjects were found to be heterozygous for mutation p.Thr5*. This mutation which generates a stop codon in the signal peptide, is assumed to prevent the synthesis of APOE. Family studies revealed that the mutation was carried on an APOE4 allele in both families. In one of the families only those who had an APOE2 allele as the second allele, had hypercholesterolemia. These were functionally hemizygous for APOE2 and presented with a Type III hyperlipoproteinemia phenotype. However, in the second family, hypercholesterolemia was observed in the index patient who had APOE3 as the second allele, but not in four heterozygous family members who also had APOE3 as the second allele. These findings underscore that the phenotypic expression of mutations in the APOE gene is variable and that the trait exhibits reduced penetrance.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors: Present perspectives and future horizons

AIMS

Our comprehensive review highlights the drug development and pharmacogenomics leading to the recent approval of PCSK9 inhibitors. We also review the anticipated future advances into the uses of PCSK9 inhibition.

BACKGROUND

Despite the present advances in pharmacotherapy, atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of mortality worldwide. Low density lipoprotein-cholesterol (LDL-C) lowering is the primary target for ASCVD risk reduction, showing demonstrable benefits in mortality. However, 70% of events occur even in the presence of statins. This residual risk may be approached with additional LDL-C reduction. Statin intolerance is a common clinical concern affecting adherence and the benefit with statins. There is also significant variation of individual lipid-lowering. Following rapid development, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have progressed from genetic observations, to mechanistic studies, to closer realization of the goal of CVD risk reduction. This review discusses the science behind PCSK9 inhibition, evidence of trials involving efficacy and safety, and reflections of its present and future role in clinical care, especially in high-risk patients with ASCVD, persons with suboptimal responses to statins and familial hyperlipidemia. Monoclonal antibodies have demonstrated LDL-C lowering of up to 57% as monotherapy and up to 73% when added to statins. Statins have limited efficacy in reduction of LDL-C due to an increased number of LDL-receptors. Elevated lipoprotein (a) levels may also be significantly lowered by PCSK9i. The journey from discovery to PSCK9 target validation took less than five years, and development and approval of therapeutic modalities for PCSK9 inhibitors happened over the next seven. This review highlights the drug development and pharmacogenomics leading to the recent approval of two agents, alirocumab and evolocumab, with a third bococizumab, and other novel approaches to the pathway pending.

DATA SYNTHESIS

We searched MEDLINE database via Pubmed for reviews, research publications and relevant trials available on PCSK9 inhibition.

CONCLUSION

Despite decades of medical advances, ASCVD remains one of the major causes of morbidity and mortality worldwide. Statin use has multiplied since the validation of LDL hypothesis, however, it is undeniable a more effective and well-tolerated agent is needed in significant number or patients. With the arrival of the era of unprecedented CV protection with PCSK9 inhibition, this exciting new therapy holds a pivotal promise as the future of lipid management. The data available already indicate safety, tolerability and superb efficacy of these agents, which are already changing contemporary cholesterol management. The rapid translation of innovative basic science research into drug development may lead to CV outcomes reduction and confirm that this pathway will become prominently utilized.