Mipomersen: a safe and effective antisense therapy adjunct to statins in patients with hypercholesterolemia

Innovative Genoceuticals in Human Gene Therapy Solutions: Challenges and Safe Clinical Trials of Orphan Gene Therapy Products

The success of gene therapy attempts is controversial and inconclusive. Currently, it is popular among the public, the scientific community, and manufacturers of Gene Therapy Medical Products. In the absence of any remedy or treatment options available for untreatable inborn metabolic orphan or genetic diseases, cancer, or brain diseases, gene therapy treatment by genoceuticals and T-cells for gene editing and recovery remains the preferred choice as the last hope. A new concept of "Genoceutical Gene Therapy" by using orphan 'nucleic acid-based therapy' aims to introduce scientific principles of treating acquired tissue damage and rare diseases. These Orphan Genoceuticals provide new scope for the 'genodrug' development and evaluation of genoceuticals and gene products for ideal 'gene therapy' use in humans with marketing authorization application (MAA). This perspective study focuses on the quality control, safety, and efficacy requirements of using 'nucleic acid-based and human cell-based new gene therapy' genoceutical products to set scientific advice on genoceutical-based 'orphan genodrug' design for clinical trials as per Western and European guidelines. The ethical Western FDA and European EMA guidelines suggest stringent legal and technical requirements on genoceutical medical products or orphan genodrug use for other countries to frame their own guidelines. The introduction section proposes lessknown 'orphan drug-like' properties of modified RNA/DNA, human cell origin gene therapy medical products, and their transgene products. The clinical trial section explores the genoceutical sources, FDA/EMA approvals for genoceutical efficacy criteria with challenges, and ethical guidelines relating to gene therapy of specific rare metabolic, cancer and neurological diseases. The safety evaluation of approved genoceuticals or orphan drugs is highlighted with basic principles and 'genovigilance' requirements (to observe any adverse effects, side effects, developed signs/symptoms) to establish their therapeutic use. Current European Union and Food and Drug Administration guidelines continuously administer fast-track regulatory legal framework from time to time, and they monitor the success of gene therapy medical product efficacy and safety. Moreover, new ethical guidelines on 'orphan drug-like genoceuticals' are updated for biodistribution of the vector, genokinetics studies of the transgene product, requirements for efficacy studies in industries for market authorization, and clinical safety endpoints with their specific concerns in clinical trials or public use.

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).

Current Options and Future Perspectives in the Treatment of Dyslipidemia

Low-density lipoprotein cholesterol (LDL-C) plays a crucial role in the development of atherosclerosis. Statin therapy is the standard treatment for lowering LDL-C in primary and secondary prevention. However, some patients do not reach optimal LDL-C target levels or do not tolerate statins, especially when taking high doses long-term. Combining statins with different therapeutic approaches and testing other new drugs is the future key to reducing the burden of cardiovascular disease (CVD). Recently, several new cholesterol-lowering drugs have been developed and approved; others are promising results, enriching the pharmacological armamentarium beyond statins. Triglycerides also play an important role in the development of CVD; new therapeutic approaches are also very promising for their treatment. Familial hypercholesterolemia (FH) can lead to CVD early in life. These patients respond poorly to conventional therapies. Recently, however, new and promising pharmacological strategies have become available. This narrative review provides an overview of the new drugs for the treatment of dyslipidemia, their current status, ongoing clinical or preclinical trials, and their prospects. We also discuss the new alternative therapies for the treatment of dyslipidemia and their relevance to practice.

The Medicinal Chemistry of Artificial Nucleic Acids and Therapeutic Oligonucleotides

Nucleic acids play a central role in human biology, making them suitable and attractive tools for therapeutic applications. While conventional drugs generally target proteins and induce transient therapeutic effects, nucleic acid medicines can achieve long-lasting or curative effects by targeting the genetic bases of diseases. However, native oligonucleotides are characterized by low in vivo stability due to nuclease sensitivity and unfavourable physicochemical properties due to their polyanionic nature, which are obstacles to their therapeutic use. A myriad of synthetic oligonucleotides have been prepared in the last few decades and it has been shown that proper chemical modifications to either the nucleobase, the ribofuranose unit or the phosphate backbone can protect the nucleic acids from degradation, enable efficient cellular uptake and target localization ensuring the efficiency of the oligonucleotide-based therapy. In this review, we present a summary of structure and properties of artificial nucleic acids containing nucleobase, sugar or backbone modifications, and provide an overview of the structure and mechanism of action of approved oligonucleotide drugs including gene silencing agents, aptamers and mRNA vaccines.

Antisense oligonucleotide: A promising therapeutic option to beat COVID-19

The COVID-19 crisis and the development of the first approved mRNA vaccine have highlighted the power of RNA-based therapeutic strategies for the development of new medicines. Aside from RNA-vaccines, antisense oligonucleotides (ASOs) represent a new and very promising class of RNA-targeted therapy. Few drugs have already received approval from the Food and Drug Administration. Here, we underscored why and how ASOs hold the potential to change the therapeutic landscape to beat SARS-CoV-2 viral infections. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Small Molecule-RNA Interactions.

Modern therapeutic approaches to liver-related disorders

The liver is a key production and processing site that is essential for health. Liver dysfunction can result in both systemic and liver-specific diseases. To combat these diseases, genetic approaches have been developed that have high liver tropism and are based on gene addition/editing or gene silencing. The gene addition/editing approach has yielded encouraging clinical data on the use of viral vectors in patients with haemophilia, as well as neuromuscular diseases, and has led to trials for liver-related disorders. However, the immune response and the long-term stability of exogenous expression remain important challenges. Gene editing and mRNA therapy have yielded first in-human proof-of-concept therapeutics and vaccines, but the road to the treatment of liver-related disorders remains long. Gene silencing is accomplished primarily via antisense oligonucleotides and small-interfering RNAs (siRNAs). siRNA modification with N-acetyl galactosamine results in hepatocellular-specific targeting and catapulted the liver to the centre of siRNA research. Several siRNA drugs for liver-related disorders have recently been approved, and the pipeline of drugs under investigation is crowded. Loss-of-function mutations might also be treated with enzyme substitution therapy. This review summarises current genetic approaches as well as key enzyme substitution therapies, focusing on recently approved compounds, potential adverse effects, and future challenges. Collectively, these recent advances place the liver at the forefront of precision medicine for metabolic and genetic diseases and are expected to transform the care and treatment of patients with both liver-specific and systemic diseases.

A Bibliometric Analysis of Familial Hypercholesterolemia From 2011 to 2021

Familial Hypercholesterolemia (FH), an autosomal dominant genetic disease, is increasingly emerging as a global threat. To learn more about the development of FH, 1 617 papers about FH and related research were retrieved in the Web of Science Core Collection from 2011 to 2021. Then, these publications were scientometrically analyzed based on CiteSpace and VOSviewer in terms of spatiotemporal distribution, author distribution, subject categories, topic distribution, and references. The results showed that research on FH is at a stable stage. More FH research has been conducted in developed countries, implying the necessity for strengthening international cooperation and exchanges. We have obtained scholars, institutions, relevant journals, and representative literatures that play an important role in FH. The research direction of FH is on the mechanisms of FH and its complications, diagnosis, statin therapy, and new lipid-lowering drug therapy. Care is the research frontier in FH, and it is in an explosive period.

New technology in the hypolipidemic drugs development. Inclisiran (LEQVIO)

The development of lipid modifying drugs was expanding during the past 30 years. Statins stay to be the first choice drugs in dyslipidemia treatment. Inhibitors of proprotein convertase subtilisin- kexin type 9 (PCSK9) enzyme in combination with statin and/or ezetimibe represent very effective therapy and better atherosclerotic cardiovascular disease (ASCVD) prevention. Antisense therapy based on oligonucleotides belongs to the new technology drugs. This therapy inhibits translation of some proteins important for the production of atherogenic lipid particles. Inclisiran is a small interfering RNA that suppresses translation of PCSK9 in the liver cells. It is applied subcutaneously twice a year and it represents a big chance for the improvement of ASCVD treatment and prevention.

The Effect of Mipomersen in the Management of Patients with Familial Hypercholesterolemia: A Systematic Review and Meta-Analysis of Clinical Trials

Background: Familial hypercholesterolemia (FH) lead to significant adverse effects in coronary arteries. Mipomersen is a second-generation antisense oligonucleotide that inhibits the synthesis of apolipoprotein B-100, an essential component of low density lipoprotein (LDL), and thus decreases the production of LDL. We aimed to determine the effect of mipomersen in patients with FH. Methods: We searched Ovid Medline, Ovid EMBASE, WHO ICTRP search portal, ISI database, the reference lists of relevant articles, and also Google Scholar to retrieve articles. All randomized controlled trials (RCTs) comparing patients with FH receiving mipomersen as an add-on and a parallel group receiving a placebo or no intervention were selected. Results: Five studies with more than 500 patients were included. All had low risk of bias. Pooling data showed that mipomersen probably reduces LDL compared with placebo [mean difference: −24.79, 95% CI (−30.15, −19.43)] but with a moderate level of certainty. There was a high level of evidence for injection site reactions [RR = 2.56, CI (1.47–4.44)] and a low level for increased serum alanine transaminase (ALT) > 3 times upper limit of normal (ULN) [RR = 5.19, CI (1.01–26.69)]. Conclusion: A moderate level of evidence in decreasing serum LDL indicates that we are uncertain if this drug provides benefit in any outcome important to patients. Although a low level of evidence for an increase in serum ALT leaves uncertainty about this adverse effect, injection site reactions in 10% or more of patients can be an important concern.

Frameworks for targeting RNA with small molecules

Since the characterization of mRNA in 1961, our understanding of the roles of RNA molecules has significantly grown. Beyond serving as a link between DNA and proteins, RNA molecules play direct effector roles by binding to various ligands, including proteins, DNA, other RNAs, and metabolites. Through these interactions, RNAs mediate cellular processes such as the regulation of gene transcription and the enhancement or inhibition of protein activity. As a result, the misregulation of RNA molecules is often associated with disease phenotypes, and RNA molecules have been increasingly recognized as potential targets for drug development efforts, which in the past had focused primarily on proteins. Although both small molecule-based and oligonucleotide-based therapies have been pursued in efforts to target RNA, small-molecule modalities are often favored owing to several advantages including greater oral bioavailability. In this review, we discuss three general frameworks (sets of premises and hypotheses) that, in our view, have so far dominated the discovery of small-molecule ligands for RNA. We highlight the unique merits of each framework as well as the pitfalls associated with exclusive focus of ligand discovery efforts within only one framework. Finally, we propose that RNA ligand discovery can benefit from using progress made within these three frameworks to move toward a paradigm that formulates RNA-targeting questions at the level of RNA structural subclasses.

The powerful world of antisense oligonucleotides: From bench to bedside

Antisense oligonucleotides (ASOs) represent a new and highly promising class of drugs for personalized medicine. In the last decade, major chemical developments and improvements of the backbone structure of ASOs have transformed them into true approved and commercialized drugs. ASOs target both DNA and RNA, including pre‐mRNA, mRNA, and ncRDA, based on sequence complementary. They are designed to be specific for each identified molecular and genetic alteration to restore a normal, physiological situation. Thus, the characterization of the underpinning mechanisms and alterations that sustain pathology is critical for accurate ASO‐design. ASOs can be used to cure both rare and common diseases, such as orphan genetic alterations and cancer. Through pioneering examples, this review shows the versatility of the mechanisms of action that provide ASOs with the potential capacity to achieve custom treatment, revolutionizing personalized medicine.

This article is categorized under:

RNA in Disease and Development > RNA in Disease

RNA Interactions with Proteins and Other Molecules > Small Molecule–RNA Interactions

Development and Clinical Translation of Approved Gene Therapy Products for Genetic Disorders

The field of gene therapy is striving more than ever to define a path to the clinic and the market. Twenty gene therapy products have already been approved and over two thousand human gene therapy clinical trials have been reported worldwide. These advances raise great hope to treat devastating rare and inherited diseases as well as incurable illnesses. Understanding of the precise pathomechanisms of diseases as well as the development of efficient and specific gene targeting and delivery tools are revolutionizing the global market. Currently, human cancers and monogenic disorders are indications number one. The elevated prevalence of genetic disorders and cancers, clear gene manipulation guidelines and increasing financial support for gene therapy in clinical trials are major trends. Gene therapy is presently starting to become commercially profitable as a number of gene and cell-based gene therapy products have entered the market and the clinic. This article reviews the history and development of twenty approved human gene and cell-based gene therapy products that have been approved up-to-now in clinic and markets of mainly North America, Europe and Asia.

Structural insight into antisense gapmer-RNA oligomer duplexes through molecular dynamics simulations

There is an extensive research carrying out on antisense technology and the molecules entering into clinical trials are increasing rapidly. Phosphorothioate (PS) is a chemical modification in which nonbridged oxygen is replaced with a sulfur, consequently providing resistance against nuclease activity. The 2'-4' conformationally restricted nucleoside has the structural features of both 2'-O-methoxy ethyl RNA (MOE), which shows good toxicity profile, and locked nucleic acid (LNA), which shows good binding affinity towards the target RNA. These modifications have been studied and suggested that they can be a potential therapeutic agents in antisense therapy. Mipomersen (ISIS 301012), which contains the novel nucleoside modification has been used to target to apolipoprotein (Apo B), which reduces LDL cholesterol by 6-41%. In this study, classical molecular dynamics (MD) simulations were performed on six different antisense gapmer/target-RNA oligomer duplexes (LNA-PS-LNA/RNA, RcMOE-PS-RcMOE/RNA, ScMOE-PS-ScMOE/RNA, MOE-PS-MOE/RNA, PS-DNA/RNA and DNA/RNA) to investigate the structural dynamics, stability and solvation properties. The LNA, MOE nucleotides present in respective duplexes are showing the structure of A-form and the PS-DNA nucleotides resemble the structure of B-form helix with respect to some of the helical parameters. Free energy calculations suggest that the oligomer, which contains LNA binds to the RNA strongly than other modifications as shown in experimental results. The MOE modified nucleotide, which although had a lower binding affinity but higher solvent accessible surface area (SASA) compared to the other modifications, may be influencing the toxicity and hence may be used it in Mipomersen, the second antisense molecule which is approved by FDA. Communicated by Ramaswamy H. Sarma.

Dyslipidemias in clinical practice

Most dyslipidemic conditions have been linked to an increased risk of cardiovascular disease. Over the past few years major advances have been made regarding the genetic and metabolic basis of dyslipidemias. Detailed characterization of the genetic basis of familial lipid disorders and knowledge concerning the effects of environmental factors on the expression of dyslipidemias have increased substantially, contributing to a better diagnosis in individual patients. In addition to these developments, therapeutic options to lower cholesterol levels in clinical practice have expanded even further in patients with familial hypercholesterolemia and in subjects with cardiovascular disease. Finally, promising upcoming therapeutic lipid lowering strategies will be reviewed. All these advances will be discussed in relation to current clinical practice with special focus on common lipid disorders including familial dyslipidemias.

Can modulators of apolipoproteinB biogenesis serve as an alternate target for cholesterol-lowering drugs?

Understanding the molecular defects underlying cardiovascular disease is necessary for the development of therapeutics. The most common method to lower circulating lipids, which reduces the incidence of cardiovascular disease, is statins, but other drugs are now entering the clinic, some of which have been approved. Nevertheless, patients cannot tolerate some of these therapeutics, the drugs are costly, and/or the treatments are approved for only rare forms of disease. Efforts to find alternative treatments have focused on other factors, such as apolipoproteinB (apoB), which transports cholesterol in the blood stream. The levels of apoB are regulated by endoplasmic reticulum (ER) associated degradation as well as by a post ER degradation pathway in model systems, and we suggest that these events provide novel therapeutic targets. We discuss first how cardiovascular disease arises and how cholesterol is regulated, and then summarize the mechanisms of action of existing treatments for cardiovascular disease. We then review the apoB biosynthetic pathway, focusing on steps that might be amenable to therapeutic interventions.

Treatment Strategy for Dyslipidemia in Cardiovascular Disease Prevention: Focus on Old and New Drugs

Prevention and treatment of dyslipidemia should be considered as an integral part of individual cardiovascular prevention interventions, which should be addressed primarily to those at higher risk who benefit most. To date, statins remain the first-choice therapy, as they have been shown to reduce the risk of major vascular events by lowering low-density lipoprotein cholesterol (LDL-C). However, due to adherence to statin therapy or statin resistance, many patients do not reach LDL-C target levels. Ezetimibe, fibrates, and nicotinic acid represent the second-choice drugs to be used in combination with statins if lipid targets cannot be reached. In addition, anti-PCSK9 drugs (evolocumab and alirocumab) provide an effective solution for patients with familial hypercholesterolemia (FH) and statin intolerance at very high cardiovascular risk. Recently, studies demonstrated the effects of two novel lipid-lowering agents (lomitapide and mipomersen) for the management of homozygous FH by decreasing LDL-C values and reducing cardiovascular events. However, the costs for these new therapies made the cost–effectiveness debate more complicated.

Assessment of External Guide Sequences' (EGS) Efficiency as Inducers of RNase P-Mediated Cleavage of mRNA Target Molecules

RNase P is a ribozyme consisting of a catalytic RNA molecule and, depending on the organism, one or more cofactor proteins. It was initially identified as the enzyme that mediates cleavage of precursor tRNAs at the 5'-end termini to generate the mature tRNAs. An important characteristic of RNase P is that its specificity depends on the structure rather than the sequence of the RNA substrate. Any RNA species that interacts with an antisense molecule (called external guide sequence, EGS) and forms the appropriate structure can be cleaved by RNase P. This property is the basis for EGS technology, an antisense methodology for inhibiting gene expression by eliciting RNase P-mediated cleavage of a target mRNA molecule. EGS technology is being developed to design therapies against a large variety of diseases. An essential milestone in developing EGSs as therapies is the assessment of the efficiency of antisense molecules to induce cleavage of the target mRNA and evaluate their effect in vivo. Here, we describe simple protocols to test the ability of EGSs to induce cleavage of a target mRNA in vitro and to induce a phenotypic change in growing cells.

PCSK9 Inhibitors: An Innovative Approach to Treating Hyperlipidemia

Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors are novel agents indicated for the treatment of hyperlipidemia. Inhibition of PCSK9 produces an increase in surface low-density lipoprotein (LDL) receptors and increases removal of LDL from the circulation. Alirocumab (Praluent; Sanofi/Regeneron, Bridgewater, NJ) and evolocumab (Repatha; Amgen, Thousand Oaks, CA) are currently available and approved for use in patients with heterozygous familial hypercholesterolemia, homozygous familial hypercholesterolemia, and clinical atherosclerotic cardiovascular disease. Bococizumab (RN316; Pfizer, New York, NY) is currently being studied in similar indications, with an estimated approval date in late 2016. The pharmacodynamic effects of PCSK9 inhibitors have been extensively studied in various patient populations. They have been shown to produce significant reductions in LDL and are well tolerated in clinical studies, but they are very costly when compared with statins, the current mainstay of hyperlipidemia treatment. Clinical outcome studies are underway, but not yet available; however, meta-analyses have pointed to a reduction in cardiovascular death and cardiovascular events with the use of PCSK9 inhibitors. This review will discuss the novel mechanism of action of PCSK9 inhibitors, the results of clinical studies, and the clinical considerations of these agents in current therapy.

Lipoprotein(a) in postmenopausal women: assessment of cardiovascular risk and therapeutic options

INTRODUCTION

Lipoprotein(a) [Lp(a)], a low-density lipoprotein (LDL)-like particle, has been independently associated with increased cardiovascular disease (CVD) risk in various populations, such as postmenopausal women. The purpose of this narrative review is to present current data on the role of Lp(a) in augmenting CVD risk in postmenopausal women and focus on the available therapeutic strategies.

METHODS

PubMed was searched for English language publications until November 2015 under the following terms: "therapy" OR "treatment" AND ["lipoprotein (a)" OR "Lp(a)"] AND ("postmenopausal women" OR "menopausal women" OR "menopause").

RESULTS

Only hormone replacement therapy (mainly oral estrogens) and tibolone have been specifically studied in postmenopausal women and can reduce Lp(a) concentrations by up to 44%, although evidence indicating a concomitant reduction in CVD risk associated with Lp(a) is lacking. As alternative treatments for women who cannot, or will not, take hormonal therapies, niacin and the upcoming proprotein convertase subtilisin / kexin type 9 (PCSK-9) inhibitors are effective in reducing Lp(a) concentrations by up to 30%. Statins have minimal or no effect on Lp(a). However, data for these and other promising Lp(a)-lowering therapies including mipomersen, lomitapide, cholesterol-ester-transfer protein inhibitors and eprotirome are derived from studies in the general, mainly high CVD risk, population, and include only subpopulations of postmenopausal women.

CONCLUSIONS

Past, present and emerging therapies can reduce Lp(a) concentrations to a varying extent. Overall, it remains to be proven whether the aforementioned reductions in Lp(a) by these therapeutic options are translated into CVD risk reduction in postmenopausal women.

MicroRNA-30c Mimic Mitigates Hypercholesterolemia and Atherosclerosis in Mice

High plasma cholesterol levels are a major risk factor for atherosclerosis. Plasma cholesterol can be reduced by inhibiting lipoprotein production; however, this is associated with steatosis. Previously we showed that lentivirally mediated hepatic expression of microRNA-30c (miR-30c) reduced hyperlipidemia and atherosclerosis in mice without causing hepatosteatosis. Because viral therapy would be formidable, we examined whether a miR-30c mimic can be used to mitigate hyperlipidemia and atherosclerosis without inducing steatosis. Delivery of a miR-30c mimic to the liver diminished diet-induced hypercholesterolemia in C57BL/6J mice. Reductions in plasma cholesterol levels were significantly correlated with increases in hepatic miR-30c levels. Long term dose escalation studies showed that miR-30c mimic caused sustained reductions in plasma cholesterol with no obvious side effects. Furthermore, miR-30c mimic significantly reduced hypercholesterolemia and atherosclerosis in Apoe(-/-) mice. Mechanistic studies showed that miR-30c mimic had no effect on LDL clearance but reduced lipoprotein production by down-regulating microsomal triglyceride transfer protein expression. MiR-30c had no effect on fatty acid oxidation but reduced lipid synthesis. Additionally, whole transcriptome analysis revealed that miR-30c mimic significantly down-regulated hepatic lipid synthesis pathways. Therefore, miR-30c lowers plasma cholesterol and mitigates atherosclerosis by reducing microsomal triglyceride transfer protein expression and lipoprotein production and avoids steatosis by diminishing lipid syntheses. It mitigates atherosclerosis most likely by reducing lipoprotein production and plasma cholesterol. These findings establish that increasing hepatic miR-30c levels is a viable treatment option for reducing hypercholesterolemia and atherosclerosis.

MicroRNAs regulating apolipoprotein B-containing lipoprotein production

MicroRNAs (miRs) are small, non-coding RNAs that regulate gene expression and have been implicated in many pathological conditions. Significant progress has been made to unveil their role in lipid metabolism. This review aims at summarizing the role of different miRs that regulate hepatic assembly and secretion of apolipoprotein B (apoB)-containing lipoproteins. Overproduction and/or impaired clearance of these lipoproteins from circulation increase plasma concentrations of lipids enhancing risk for cardiovascular disease. So far, three miRs, miR-122, miR-34a, and miR-30c have been shown to modulate hepatic production of apoB-containing low density lipoproteins. In this review, we will first provide a brief overview of lipid metabolism and apoB-containing lipoprotein assembly to orient readers to different steps that have been shown to be regulated by miRs. Then, we will discuss the role of each miR on plasma lipids and atherosclerotic burden. Furthermore, we will summarize mechanistic studies explaining how these miRs regulate hepatic lipid synthesis, fatty acid oxidation, and lipoprotein secretion. Finally, we will briefly highlight the potential use of each miR as a therapeutic drug for treating cardiovascular diseases. This article is part of a Special Issue entitled: MicroRNAs and lipid/energy metabolism and related diseases edited by Carlos Fernández-Hernando and Yajaira Suárez.

New and Emerging LDL Cholesterol-Lowering Drugs

The role of low-density lipoprotein cholesterol (LDL-C) in the pathophysiology of atherosclerosis is well recognized, and the use of LDL-C lowering medications has led to a significant reduction of cardiovascular risk in both primary and secondary prevention. Statins are the standard of care and their use is supported by extensive evidence demonstrating their effectiveness in lowering LDL-C and in reducing the risk for cardiovascular disease. However, many individuals at risk for cardiovascular disease fail to achieve LDL-C goals. In addition, several patients are intolerant to statins due to side effects, mostly myalgia and weakness, especially at high statin doses. However, until recently, the efficacy of other non-statin LDL-C-lowering drugs was modest, not exceeding a LDL-C reduction of 20%. In view of the above, extensive research is being carried out to identify new LDL-C-lowering agents with an acceptable side effect profile, which, used alone or in combination with statins, would improve our ability to achieve LDL-C goals and reduce cardiovascular risk. This review aims to provide the current evidence regarding the newly approved LDL-C-lowering agents, as well as the clinical and scientific data pertaining to promising new and emerging LDL-C-lowering drugs on the horizon.

Therapeutic oligonucleotides with polyethylene glycol modifications

In the field of oligonucleotide drugs, the attachment of PEG is a well-established strategy to prevent enzymatic degradation and avoid renal elimination. Pegaptanib and other oligonucleotides in clinical development utilize the attachment of linear or branched high molecular weight PEG chains for increase of accumulation and duration of the effect after local or systemic application. The length of PEG chains is decisive for the pharmacokinetic and pharmacodynamic effects. Longer chains increase circulation times, but generally decrease gene-silencing efficiencies for antisense and siRNA agents and binding affinities for aptamers. Shorter chains are less efficient in preventing renal filtration, but have also less impact on the gene-silencing machinery and binding kinetics.

Concise postsynthetic preparation of oligonucleotide-oligopeptide conjugates through facile disulfide bond formation

BACKGROUND

Despite recent advances, major hurdles still need to be cleared for widespread application of therapeutic antisense technologies. In particular, pharmacokinetic properties and efficient cellular uptake need to be improved through chemical derivatization or bioconjugation.

RESULTS

The 2'-O-thioethylene nucleotide building block affords easy implementation into standard oligonucleotide synthesis protocols and was used to attach oligolysine chains to phosphodiester oligonucleotides by direct reaction with S-sulfonate protected peptides. Efficient gene silencing was induced in a cell culture model after transfection reagent-free application of the conjugates.

CONCLUSION

A facile optimized procedure for generating oligonucleotide-peptide conjugates was established. The attachment of short basic peptides via a labile linker is sufficient to enhance membrane permeability of oligonucleotides and result in successful gene silencing.

The role of antisense oligonucleotide therapy in patients with familial hypercholesterolemia: risks, benefits, and management recommendations

Antisense oligonucleotide therapy is a promising approach for the treatment of a broad variety of medical conditions. It functions at the cellular level by interfering with RNA function, often leading to degradation of specifically targeted abnormal gene products implicated in the disease process. Mipomersen is a novel antisense oligonucleotide directed at apolipoprotein (apoB)-100, the primary apolipoprotein associated with low-density lipoprotein cholesterol (LDL-C), which has recently been approved for the treatment of familial hypercholesterolemia. A number of clinical studies have demonstrated its efficacy in lowering LDL-C and apoB levels in patients with elevated LDL-C despite maximal medical therapy using conventional lipid-lowering agents. This review outlines the risks and benefits of therapy and provides recommendations on the use of mipomersen.

Going beyond the liver: progress and challenges of targeted delivery of siRNA therapeutics

Therapeutic gene silencing promises significant progress in pharmacotherapy, including considerable expansion of the druggable target space and the possibility for treating orphan diseases. Technological hurdles have complicated the efficient use of therapeutic oligonucleotides, and siRNA agents suffer particularly from insufficient pharmacokinetic properties and poor cellular uptake. Intense development and evolution of delivery systems have resulted in efficient uptake predominantly in liver tissue, in which practically all nanoparticulate and liposomal delivery systems show the highest accumulation. The most efficacious strategies include liposomes and bioconjugations with N-acetylgalactosamine. Both are in early clinical evaluation stages for treatment of liver-associated diseases. Approaches for achieving knockdown in other tissues and tumors have been proven to be more complicated. Selective targeting to tumors may be enabled through careful modulation of physical properties, such as particle size, or by taking advantage of specific targeting ligands. Significant barriers stand between sufficient accumulation in other organs, including endothelial barriers, cellular membranes, and the endosome. The brain, which is shielded by the blood-brain barrier, is of particular interest to facilitate efficient oligonucleotide therapy of neurological diseases. Transcytosis of the blood-brain barrier through receptor-specific docking is investigated to increase accumulation in the central nervous system. In this review, the current clinical status of siRNA therapeutics is summarized, as well as innovative and promising preclinical concepts employing tissue- and tumor-targeted ligands. The requirements and the respective advantages and drawbacks of bioconjugates and ligand-decorated lipid or polymeric particles are discussed.

[Dyslipidaemia and vascular risk. A new evidence based review]

Dyslipidaemia is one of the major risk factors for ischaemic heart disease, the leading cause of death worldwide. Early detection and therapeutic intervention are key elements in the adequate prevention of cardiovascular disease. It is essential to have knowledge of the therapeutic arsenal available for their appropriate use in each of the clinical situations that might be presented in our patients. In the past 3 years, there has been a proliferation of multiple guidelines for the clinical management of patients with dyslipidaemia, with apparent contradictory messages regarding the achievement of the control objectives, which are confusing clinicians. This review aims to provide an updated overview of the situation as regards dyslipidaemia, based on the positioning of both European and American guidelines, through different risk situations and ending with the concept of atherogenic dyslipidaemia as a recognized cardiovascular risk factor.

Mipomersen sodium: first global approval

Mipomersen sodium (Kynamro™) (henceforth mipomersen) is a second-generation antisense oligonucleotide inhibitor of apolipoprotein B-100, which is the main structural component of atherogenic lipid particles. Mipomersen is administered via subcutaneous injection and is indicated as adjunctive treatment for homozygous familial hypercholesterolaemia (HoFH). The drug was developed by Isis Pharmaceuticals, which now collaborates with Genzyme Corporation for on-going development and product marketing. Multinational phase III trials of mipomersen as adjunctive therapy were completed in patients with HoFH, severe FH, heterozygous FH (HeFH) with coronary artery disease (CAD), and in those with hypercholesterolaemia at high risk of CAD. Mipomersen 200 mg once weekly has been approved in the USA as an adjunct to lipid-lowering medications and diet in HoFH patients and is undergoing regulatory review in the EU for the same indication. Genzyme is also conducting a multinational phase III, open-label extension study to evaluate long-term treatment in HoFH and HeFH patients, as well as a multinational trial to evaluate a three-times-per-week mipomersen regimen in patients with severe FH. This article summarises the milestones in the development of once-weekly, subcutaneous mipomersen leading to this first approval.

Long-term efficacy and safety of mipomersen in patients with familial hypercholesterolaemia: 2-year interim results of an open-label extension

AIMS

To evaluate the efficacy and safety of extended dosing with mipomersen in patients with familial hypercholesterolaemia (HC) taking maximally tolerated lipid-lowering therapy.

METHODS AND RESULTS

A planned interim analysis of an ongoing, open-label extension trial in patients (n = 141) with familial HC receiving a subcutaneous injection of 200 mg mipomersen weekly plus maximally tolerated lipid-lowering therapy for up to 104 weeks. The mean changes in low-density lipoprotein cholesterol (LDL-C) from baseline to weeks 26 (n = 130), 52 (n = 111), 76 (n = 66), and 104 (n = 53) were -28, -27, -27, and -28%; and in apolipoprotein B -29, -28, -30, and -31%, respectively. Reductions in total cholesterol, non-high-density lipoprotein-cholesterol, and lipoprotein(a) were comparable with decreases in LDL-C and apolipoprotein B levels. Mean high-density lipoprotein cholesterol increased from baseline by 7 and 6% at weeks 26 and 52, respectively. The long-term safety profile of mipomersen was similar to that reported in the associated randomized placebo-controlled Phase 3 trials. Adverse events included injection site reactions and flu-like symptoms. There was an incremental increase in the median liver fat during the initial 6-12 months that appeared to diminish with continued mipomersen exposure beyond 1 year and returned towards baseline 24 weeks after last drug dose suggestive of adaptation. The median alanine aminotransferase level showed a similar trend over time.

CONCLUSION

Long-term treatment with mipomersen for up to 104 weeks provided sustained reductions in all atherosclerotic lipoproteins measured and a safety profile consistent with prior controlled trials in these high-risk patient populations. CLINICALTRIALS.GOV: NCT00694109.

Antisense oligonucleotides on neurobehavior, respiratory, and cardiovascular function, and hERG channel current studies

INTRODUCTION

Safety Pharmacology studies were conducted in mouse, rat, and non-human primate to determine in vivo effects of antisense oligonucleotides (ASOs) on the central nervous system, respiratory system, and cardiovascular system. Effects on the hERG potassium channel current was evaluated in vitro.

METHODS

ASOs contained terminal 2'-O-methoxyethyl nucleotides, central deoxy nucleotides, and a phosphorothioate backbone. Neurobehavior was evaluated by Functional Observatory Battery in rodents. Respiratory function was directly measured in rodents by plethysmograph; respiratory rate and blood gases were measured in monkey. Basic cardiovascular endpoints were measured in rat; cardiovascular evaluation in monkey involved implanted telemetry units. In single and repeat dose studies ASOs were administered by subcutaneous injection at up to 300 mg/kg, 250 mg/kg, and 40 mg/kg in mouse, rat, or monkey, respectively. Assays were performed in HEK293 or CHO-K1 cells, stably transfected with hERG cDNA, at ASO concentrations of up to 300 μM.

RESULTS

No apparent effects were noted for respiratory or CNS function. Continuous monitoring of the cardiovascular system in monkey demonstrated no ASO-related changes in blood pressures, heart rate, or ECG and associated parameters (i.e., QRS duration). Specific assessment of the hERG potassium channel indicated no potential for actions on ventricular repolarization or modest effects only at excessive concentrations.

DISCUSSION

The absence of direct actions on neurobehavior and respiratory function associated with the administration of ASOs in safety pharmacology core battery studies is consistent with published toxicology studies. The combination of in vitro hERG studies and in vivo studies in rat and monkey are consistent with no direct actions by ASOs on cardiac cell function or electrical conduction at relevant concentrations and dose levels. Taken as a whole, dedicated studies focused on the safety pharmacology of specific organ systems do not appear to add significant data for interpretation of potential adverse effects. The need for dedicated studies for future ASOs in the same class is questionable, as a more encompassing data set can be collected in repeat dose and longer-term toxicology studies.

Clinical pharmacological properties of mipomersen (Kynamro), a second generation antisense inhibitor of apolipoprotein B

Mipomersen is a second generation antisense oligonucleotide that targets apolipoprotein B. It has been studied thoroughly in clinical trials (more than 800 subjects), including four randomized double-blind placebo controlled phase 3 studies involving 391 patients, and is in registration for the treatment of severe hypercholesterolaemia. The pharmacokinetic and pharmacodynamic properties of mipomersen are well characterized. Mipomersen is rapidly and extensively absorbed after subcutaneous administration and has an elimination half-life of approximately 30 days across species. It is cleared by nuclease metabolism and renal excretion of the metabolites. Mipomersen reduces all apolipoprotein B containing atherogenic particles and displays dose dependent reductions between 50-400 mg week⁻¹ , both as a single agent and in the presence of maximal lipid lowering therapy. No drug-drug interactions have been identified. Mipomersen is a representative of second generation antisense drugs, all of which have similar properties, and is thus representative of the behaviour of the class of drugs.

Penicillin facilitates the entry of antisense constructs into Streptococcus mutans

Antisense oligonucleotides (AS-ODN) target genes in a sequence-specific manner inhibit gene function and have potential use as antimicrobial agents. Cell barriers, such as peptidoglycan, cell surface proteins and lipopolysaccharide membranes, prevent delivery of AS-ODN into the bacterial cell, limiting their use as an effective treatment option. The β-lactam antibiotic penicillin was examined for its ability to deliver phosphorothioate oligodeoxyribonucleotides (PS-ODNs) and γ(32) P-ODN into Streptococcus mutans OMZ175. Treatment of lag-phase S. mutans OMZ175 cells with penicillin and FBA (PS-ODN targeting the fructose-biphosphate aldolase gene), resulted in prolonged suppression of growth (> 24 h) and fba expression (656.9 ± 194.4-fold decrease at 5 h). Suppression of both cell growth and fba expression corresponded with a greater amount of γ(32) P-ODN becoming cell associated, with a maximum γ(32) P-ODN concentration per cell achieved 5 h after penicillin treatment (6.50 ± 1.39 × 10(8) molecules per CFU). This study confirms that for S. mutans OMZ175, the peptidoglycan layer acts as a major barrier preventing AS-ODN penetration and suggests that the use of agents such as penicillin that interfere with peptidoglycan integrity can significantly increase the uptake of PS-ODN by these cells.

Mipomersen, an apolipoprotein B synthesis inhibitor, reduces atherogenic lipoproteins in patients with severe hypercholesterolemia at high cardiovascular risk: a randomized, double-blind, placebo-controlled trial

OBJECTIVES

This study sought to examine the efficacy and safety of mipomersen for reducing atherogenic lipids and lipoproteins in patients with hypercholesterolemia.

BACKGROUND

Many patients on lipid-lowering therapies remain unable to achieve target low-density lipoprotein (LDL) cholesterol levels. Mipomersen, an antisense oligonucleotide inhibitor of apolipoprotein B, reduces LDL cholesterol and atherogenic lipoproteins.

METHODS

This randomized, double-blind, multicenter study enrolled 158 patients with baseline LDL cholesterol levels ≥100 mg/dl with, or at high risk for, coronary heart disease who were receiving maximally tolerated lipid-lowering therapy. Patients received weekly subcutaneous mipomersen 200 mg (n = 105) or placebo (n = 52) for 26 weeks, with a 24-week follow-up period. Randomization was stratified by type 2 diabetes status.

RESULTS

Sixty mipomersen and 44 placebo patients completed treatment. Mean baseline LDL cholesterol levels were 122.7 and 122.6 mg/dl in the placebo and mipomersen patients, respectively. Mipomersen reduced LDL cholesterol by -36.9% compared with placebo at -4.5% (p < 0.001). Target LDL cholesterol <100 mg/dl was attained in 76% of mipomersen and 38% of placebo patients. Mipomersen also significantly reduced apolipoprotein B (-38%) and lipoprotein(a) (-24%) (p < 0.001). Common adverse events included injection site reactions (78% with mipomersen, 31% with placebo) and flu-like symptoms (34% with mipomersen, 21% with placebo). Elevations in transaminases and liver fat also occurred in some patients, and these levels returned toward baseline after treatment cessation.

CONCLUSIONS

Mipomersen significantly reduced LDL cholesterol, apolipoprotein B, and lipoprotein(a) in patients with hypercholesterolemia with, or at risk for, coronary heart disease not controlled by existing therapies. (Safety and Efficacy of Mipomersen [ISIS 301012] as Add-On Therapy in High Risk Hypercholesterolemic Patients; NCT00770146).

Regulating intestinal function to reduce atherogenic lipoproteins

Significant knowledge regarding different molecules involved in the transport of dietary fat into the circulation has been garnered. Studies point to the possibility that accumulation of intestine-derived lipoproteins in the plasma could contribute to atherosclerosis. This article provides a brief overview of dietary lipid metabolism and studies in mice supporting the hypothesis that intestinal lipoproteins contribute to atherosclerosis. Deficiencies in lipoprotein lipase and Gpihbp1, and overexpression of heparanse in mice, are associated with increases in atherosclerosis, suggesting that defects in catabolism of larger lipoproteins in the plasma contribute to atherosclerosis. Furthermore, inositol-requiring enzyme 1β-deficient mice that produce more intestinal lipoproteins also develop more atherosclerosis. Thus, increases in plasma intestinal lipoproteins due to either overproduction or reduced catabolism result in augmented atherosclerosis. Intestinal lipoproteins tend to adhere strongly to subendothelial proteoglycans, elicit an inflammatory response by endothelial cells and activate macrophages, contributing to the initiation and progression of the disease. Thus, molecules that reduce intestinal lipid absorption can be useful in lowering atherosclerosis.

Novel pharmacotherapies of familial hyperlipidemia

Familial hyperlipidemia is an inherited metabolic disorder characterized by elevated lipid and/or lipoprotein levels in the blood. Despite improvements in lipid-lowering therapy during the last decades, it still remains a substantial contributor to the incidence of cardiovascular disease since patients on current conventional therapies do not achieve their target LDL-cholesterol levels. With a view to lower LDL-cholesterol levels, a number of new therapeutic strategies have been developed over recent years. In this review, we provide an overview of these treatment options that are currently in clinical development and may offer alternative or adjunctive therapies for this high-risk population.

XIAP antisense therapy with AEG 35156 in acute myeloid leukemia

INTRODUCTION

AEG 35156 is an antisense oligonucleotide to X-linked inhibitor of apoptosis protein (XIAP). Overexpression of XIAP is common in acute myeloid leukemia (AML) and other cancers and is thought to cause resistance to cancer therapy. Effective treatment options for patients with relapsed or refractory AML are limited and survival continues to be poor. Targeting resistance mechanisms is expected to improve results in relapsed as well as front-line settings.

AREAS COVERED

Role of XIAP in apoptosis pathways, structure of AEG 35156, mechanism of action, pharmacokinetics and pharmacodynamics, clinical efficacy and review of clinical trials in AML.

EXPERT OPINION

AEG 35156 in combination with standard chemotherapy was generally very well-tolerated and had shown some evidence of anti-leukemic activity in AML. The target knock down was transient and has not always correlated with response. Future studies may be done with variations in dose scheduling and with more emphasis on comprehensive pharmacodynamic studies simultaneously analyzing other inhibitor of apoptosis proteins (IAPs) and various XIAP regulators. Use of small molecule mimetics of second mitochondria derived activator of caspases (Smac) simultaneously targeting other IAPs appears to be an attractive option.

Reducing residual risk: modern pharmacochemistry meets old-fashioned lifestyle and adherence improvement

Despite remarkable advances in identifying and managing coronary heart disease, the global burden of cardiovascular (CV) risk and levels of undetected, subclinical heart disease remain enormous. Substantial numbers of patients do not reach their therapeutic goals, others are unable to tolerate the treatments, half may fail to adhere to their programs, and in those who do attain their targets, major cardiovascular events may continue. Well-known risk factors, such as obesity and diabetes, have now gained the upper hand, with no evidence-based remedy capable of reversing this trend. All told, less than 1% of American adults and adolescents qualify for ideal CV health; world-wide, the growing prevalence of CV risk factors in children is imposing. A number of novel emerging drug therapies are in development, some recently approved for use in patients with familial hypercholesterolemia.

Hopefully, they will contribute significantly to the current therapeutic armamentarium. However, for meaningful improvement in total and residual CV risk, an optimal mix of all available modalities will likely be necessary, including earlier and more effective prevention, aggressive medical care, revascularization and device implantation, judicious use of novel agents, and reengineering of the environment.