Antisense oligonucleotide directed to human apolipoprotein B-100 reduces lipoprotein(a) levels and oxidized phospholipids on human apolipoprotein B-100 particles in lipoprotein(a) transgenic mice

New insights into the therapeutic options to lower lipoprotein(a)

BACKGROUND

Elevated levels of lipoprotein(a) [Lp(a)] represent a risk factor for cardiovascular disease including aortic valve stenosis, myocardial infarction and stroke. While the patho-physiological mechanisms linking Lp(a) with atherosclerosis are not fully understood, from genetic studies that lower Lp(a) levels protect from CVD independently of other risk factors including lipids and lipoproteins. Hereby, Lp(a) has been considered an appealing pharmacological target.

RESULTS

However, approved lipid lowering therapies such as statins, ezetimibe or PCSK9 inhibitors have a neutral to modest effect on Lp(a) levels, thus prompting the development of new strategies selectively targeting Lp(a). These include antisense oligonucleotides and small interfering RNAs (siRNAs) directed towards apolipoprotein(a) [Apo(a)], which are in advanced phase of clinical development. More recently, additional approaches including inhibitors of Apo(a) and gene editing approaches via CRISPR-Cas9 technology entered early clinical development.

CONCLUSION

If the results from the cardiovascular outcome trials, designed to demonstrate whether the reduction of Lp(a) of more than 80% as observed with pelacarsen, olpasiran or lepodisiran translates into the decrease of cardiovascular mortality and major adverse cardiovascular events, will be positive, lowering Lp(a) will become a new additional target in the management of patients with elevated cardiovascular risk.

Lipoprotein(a) in the Year 2024: A Look Back and a Look Ahead

In fitting with the American Heart Association’s 100th anniversary of its founding and Arteriosclerosis, Thrombosis and Vascular Biology organizing a Centennial Collection to celebrate this event, lipoprotein(a) [Lp(a)] celebrates its 61st birthday in November 2024. There has been substantial progress in understanding the biology and pathophysiology of Lp(a) in the last 6 decades, including its discovery as a unique β-lipoprotein containing the pathognomonic apolipoprotein(a) moiety covalently bound to apolipoprotein B-100, its independent monogenetic association with cardiovascular disease and calcific aortic valve disease, its increased content of pro-atherogenic and pro-inflammatory of oxidized phospholipids relative to other lipoproteins and the development of RNA therapeutics to lower plasma Lp(a) levels. The validation or refutation of the “Lp(a) hypothesis”, namely that lowering plasma Lp(a) will lead to clinical benefit, is ongoing in 3 clinical outcomes trials. This essay reviews the discovery of Lp(a), summarizes the seminal pathophysiological findings since its discovery, discusses ongoing clinical trials with novel drugs and approaches, and provides a look ahead to unanswered questions.

Unraveling the Enigma of Moderate Aortic Stenosis: Challenges and Future Prospects

According to current guidelines, only clinical surveillance is recommended for patients with moderate aortic valve stenosis (AS), while aortic valve replacement may be considered in patients undergoing surgery for other indications. Recent studies have shown that moderate AS is associated with a high risk of adverse cardiovascular events, including death, especially in patients with left ventricular dysfunction. In this context, multimodality imaging can help to improve the accuracy of moderate AS diagnosis and to assess left ventricular remodeling response. This review discusses the natural history of this valve disease and the role of multimodality imaging in the diagnostic process, summarizes current evidence on the medical and non-medical management, and highlights ongoing trials on valve replacement.

Lipoprotein(a), platelet function and cardiovascular disease

Lipoprotein(a) (Lp(a)) is associated with atherothrombosis through several mechanisms, including putative antifibrinolytic properties. However, genetic association studies have not demonstrated an association between high plasma levels of Lp(a) and the risk of venous thromboembolism, and studies in patients with highly elevated Lp(a) levels have shown that Lp(a) lowering does not modify the clotting properties of plasma ex vivo. Lp(a) can interact with several platelet receptors, providing biological plausibility for a pro-aggregatory effect. Observational clinical studies suggest that elevated plasma Lp(a) concentrations are associated with worse long-term outcomes in patients undergoing revascularization. Furthermore, in these patients, those with elevated plasma Lp(a) levels derive more benefit from prolonged dual antiplatelet therapy than those with normal Lp(a) levels. The ASPREE trial in healthy older individuals treated with aspirin showed a reduction in ischaemic events in those who had a single-nucleotide polymorphism in LPA that is associated with elevated Lp(a) levels in plasma, without an increase in bleeding events. In this Review, we re-examine the role of Lp(a) in the regulation of platelet function and suggest areas of research to define further the clinical relevance to cardiovascular disease of the observed associations between Lp(a) and platelet function.

Self-Penetrating Oligonucleotide Derivatives: Features of Self-Assembly and Interactions with Serum and Intracellular Proteins

Lipophilic oligonucleotide derivatives are a potent approach to the intracellular delivery of nucleic acids. The binding of these derivatives to serum albumin is a determinant of their fate in the body, as its structure contains several sites of high affinity for hydrophobic compounds. This study focuses on the features of self-association and non-covalent interactions with human serum albumin of novel self-penetrating oligonucleotide derivatives. The study revealed that the introduction of a triazinyl phosphoramidate modification bearing two dodecyl groups at the 3' end region of the oligonucleotide sequence has a negligible effect on its affinity for the complementary sequence. Dynamic light scattering verified that the amphiphilic oligonucleotides under study can self-assemble into micelle-like particles ranging from 8 to 15 nm in size. The oligonucleotides with dodecyl groups form stable complexes with human serum albumin with a dissociation constant of approximately 10-6 M. The oligonucleotide micelles are simultaneously destroyed upon binding to albumin. Using an electrophoretic mobility shift assay and affinity modification, we examined the ability of DNA duplexes containing triazinyl phosphoramidate oligonucleotides to interact with Ku antigen and PARP1, as well as the mutual influence of PARP1 and albumin or Ku antigen and albumin upon interaction with DNA duplexes. These findings, together with the capability of dodecyl-containing derivatives to effectively penetrate different cells, such as HEK293 and T98G, indicate that the oligonucleotides under study can be considered as a platform for the development of therapeutic preparations with a target effect.

Established and Emerging Lipid-Lowering Drugs for Primary and Secondary Cardiovascular Prevention

Despite treatment with statins, patients with elevated low-density lipoprotein cholesterol (LDL-C) and triglycerides remain at increased risk for adverse cardiovascular events. Consequently, novel pharmaceutical drugs have been developed to control and modify the composition of blood lipids to ultimately prevent fatal cardiovascular events in patients with dyslipidaemia. This article reviews established and emerging lipid-lowering drugs regarding their mechanism of action, development stage, ongoing clinical trials, side effects, effect on blood lipids and reduction in cardiovascular morbidity and mortality. We conducted a keyword search to identify studies on established and emerging lipid modifying drugs. Results were summarized in a narrative overview. Established pharmaceutical treatment options include the Niemann-Pick-C1 like-1 protein (NPC1L1) inhibitor ezetimibe, the protein convertase subtilisin-kexin type 9 (PCSK9) inhibitors alirocumab and evolocumab, fibrates as peroxisome proliferator receptor alpha (PPAR-α) activators, and the omega-3 fatty acid icosapent ethyl. Statins are recommended as the first-line therapy for primary and secondary cardiovascular prevention in patients with hypercholesterinaemia and hypertriglyceridemia. For secondary prevention in hypercholesterinaemia, second-line options such as statin add-on or statin-intolerant treatments are ezetimibe, alirocumab and evolocumab. For secondary prevention in hypertriglyceridemia, second-line options such as statin add-on or statin-intolerant treatments are icosapent ethyl and fenofibrate. Robust data for these add-on therapeutics in primary cardiovascular prevention remains scarce. Recent biotechnological advances have led to the development of innovative small molecules (bempedoic acid, lomitapide, pemafibrate, docosapentaenoic and eicosapentaenoic acid), antibodies (evinacumab), antisense oligonucleotides (mipomersen, volanesorsen, pelcarsen, olezarsen), small interfering RNA (inclisiran, olpasiran), and gene therapies for patients with dyslipidemia. These molecules specifically target new cellular pathways, such as the adenosine triphosphate-citrate lyase (bempedoic acid), PCSK9 (inclisiran), angiopoietin-like 3 (ANGPTL3: evinacumab), microsomal triglyceride transfer protein (MTP: lomitapide), apolipoprotein B-100 (ApoB-100: mipomersen), apolipoprotein C-III (ApoC-III: volanesorsen, olezarsen), and lipoprotein (a) (Lp(a): pelcarsen, olpasiran). The authors are hopeful that the development of new treatment modalities alongside new therapeutic targets will further reduce patients' risk of adverse cardiovascular events. Apart from statins, data on new drugs' use in primary cardiovascular prevention remain scarce. For their swift adoption into clinical routine, these treatments must demonstrate safety and efficacy as well as cost-effectiveness in randomized cardiovascular outcome trials.

In vivo PAR-CLIP (viP-CLIP) of liver TIAL1 unveils targets regulating cholesterol synthesis and secretion

System-wide cross-linking and immunoprecipitation (CLIP) approaches have unveiled regulatory mechanisms of RNA-binding proteins (RBPs) mainly in cultured cells due to limitations in the cross-linking efficiency of tissues. Here, we describe viP-CLIP (in vivo PAR-CLIP), a method capable of identifying RBP targets in mammalian tissues, thereby facilitating the functional analysis of RBP-regulatory networks in vivo. We applied viP-CLIP to mouse livers and identified Insig2 and ApoB as prominent TIAL1 target transcripts, indicating an important role of TIAL1 in cholesterol synthesis and secretion. The functional relevance of these targets was confirmed by showing that TIAL1 influences their translation in hepatocytes. Mutant Tial1 mice exhibit altered cholesterol synthesis, APOB secretion and plasma cholesterol levels. Our results demonstrate that viP-CLIP can identify physiologically relevant RBP targets by finding a factor implicated in the negative feedback regulation of cholesterol biosynthesis.

Effects of Lipid-Modifying and Other Drugs on Lipoprotein(a) Levels-Potent Clinical Implications

The past few years have shown an ongoing interest in lipoprotein(a) (Lp(a)), a lipid molecule that has been proven to have atherogenic, thrombogenic, and inflammatory properties. Several lines of evidence, indeed, have demonstrated an increased risk of cardiovascular disease as well as calcific aortic valve stenosis in patients with elevated Lp(a) levels. Statins, the mainstay of lipid-lowering therapy, slightly increase Lp(a) levels, while most other lipid-modifying agents do not significantly alter Lp(a) concentrations, except for proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. The latter have been shown to reduce Lp(a) levels; however, the clinical significance of this effect has not been clearly elucidated. Of note, the pharmaceutical lowering of Lp(a) may be achieved with novel treatments specifically designed for this purpose (i.e., antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs)). Large clinical trials with cardiovascular outcomes with these agents are ongoing, and their results are eagerly awaited. Furthermore, several non-lipid-modifying drugs of various classes may influence Lp(a) concentrations. We have searched MEDLINE, EMBASE, and CENTRAL databases up to 28 January 2023 and summarized the effects of established and emerging lipid-modifying drugs and other medications on Lp(a) levels. We also discuss the potent clinical implications of these alterations.

Pharmacotherapy in familial hypercholesterolemia - Current state and emerging paradigms

Familial hypercholesterolemia is a highly prevalent but underdiagnosed disease marked by increased risk of cardiovascular morbidity and mortality. Aggressive reduction of LDL-cholesterol is a hallmark of cardiovascular risk mitigation in familial hypercholesterolemia. More recently, we have witnessed an expanded repertoire of pharmacologic agents that directly target LDL-cholesterol and/or reduce heart disease burden. In this state-of-the-art review, we explore the development, clinical efficacy and limitations of existing and potential future therapeutics in familial hypercholesterolemia.

Lipoprotein(a): Its Association with Calcific Aortic Valve Stenosis, the Emerging RNA-Related Treatments and the Hope for a New Era in “Treating” Aortic Valve Calcification

The treatment of patients with aortic valve calcification (AVC) and calcific aortic valve stenosis (CAVS) remains challenging as, until today, all non-invasive interventions have proven fruitless in preventing the disease’s onset and progression. Despite the similarities in the pathogenesis of AVC and atherosclerosis, statins failed to show a favorable effect in preventing AVC progression. The recognition of lipoprotein(a) [Lp(a)] as a strong and potentially modifiable risk factor for the development and, perhaps, the progression of AVC and CAVS and the evolution of novel agents leading in a robust Lp(a) reduction, have rekindled hope for a promising future in the treatment of those patients. Lp(a) seems to promote AVC via a ‘three hit’ mechanism including lipid deposition, inflammation and autotaxin transportation. All of these lead to valve interstitial cells transition into osteoblast-like cells and, thus, to parenchymal calcification. Currently available lipid-lowering therapies have shown a neutral or mild effect on Lp(a), which was proven insufficient to contribute to clinical benefits. The short-term safety and the efficacy of the emerging agents in reducing Lp(a) have been proven; nevertheless, their effect on cardiovascular risk is currently under investigation in phase 3 clinical trials. A positive result of these trials will probably be the spark to test the hypothesis of the modification of AVC’s natural history with the novel Lp(a)-lowering agents.

Lipoprotein(a): Evidence for Role as a Causal Risk Factor in Cardiovascular Disease and Emerging Therapies

Lipoprotein(a) (Lp(a)) is an established risk factor for multiple cardiovascular diseases. Several lines of evidence including mechanistic, epidemiologic, and genetic studies support the role of Lp(a) as a causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and aortic stenosis/calcific aortic valve disease (AS/CAVD). Limited therapies currently exist for the management of risk associated with elevated Lp(a), but several targeted therapies are currently in various stages of clinical development. In this review, we detail evidence supporting Lp(a) as a causal risk factor for ASCVD and AS/CAVD, and discuss approaches to managing Lp(a)-associated risk.

Lipoprotein(a): Pathophysiology, measurement, indication and treatment in cardiovascular disease. A consensus statement from the Nouvelle Société Francophone d'Athérosclérose (NSFA)

Lipoprotein(a) is an apolipoprotein B100-containing low-density lipoprotein-like particle that is rich in cholesterol, and is associated with a second major protein, apolipoprotein(a). Apolipoprotein(a) possesses structural similarity to plasminogen but lacks fibrinolytic activity. As a consequence of its composite structure, lipoprotein(a) may: (1) elicit a prothrombotic/antifibrinolytic action favouring clot stability; and (2) enhance atherosclerosis progression via its propensity for retention in the arterial intima, with deposition of its cholesterol load at sites of plaque formation. Equally, lipoprotein(a) may induce inflammation and calcification in the aortic leaflet valve interstitium, leading to calcific aortic valve stenosis. Experimental, epidemiological and genetic evidence support the contention that elevated concentrations of lipoprotein(a) are causally related to atherothrombotic risk and equally to calcific aortic valve stenosis. The plasma concentration of lipoprotein(a) is principally determined by genetic factors, is not influenced by dietary habits, remains essentially constant over the lifetime of a given individual and is the most powerful variable for prediction of lipoprotein(a)-associated cardiovascular risk. However, major interindividual variations (up to 1000-fold) are characteristic of lipoprotein(a) concentrations. In this context, lipoprotein(a) assays, although currently insufficiently standardized, are of considerable interest, not only in stratifying cardiovascular risk, but equally in the clinical follow-up of patients treated with novel lipid-lowering therapies targeted at lipoprotein(a) (e.g. antiapolipoprotein(a) antisense oligonucleotides and small interfering ribonucleic acids) that markedly reduce circulating lipoprotein(a) concentrations. We recommend that lipoprotein(a) be measured once in subjects at high cardiovascular risk with premature coronary heart disease, in familial hypercholesterolaemia, in those with a family history of coronary heart disease and in those with recurrent coronary heart disease despite lipid-lowering treatment. Because of its clinical relevance, the cost of lipoprotein(a) testing should be covered by social security and health authorities.

Elevated Lipoprotein(a): Background, Current Insights and Future Potential Therapies

Lipoprotein(a) forms a subfraction of the lipid profile and is characterized by the addition of apolipprotein(a) (apo(a)) to apoB100 derived particles. Its levels are mostly genetically determined inversely related to the number of protein domain (kringle) repeats in apo(a). In epidemiological studies, it shows consistent association with cardiovascular disease (CVD) and most recently with extent of aortic stenosis. Issues with standardizing the measurement of Lp(a) are being resolved and consensus statements favor its measurement in patients at high risk of, or with family histories of CVD events. Major lipid-lowering therapies such as statin, fibrates, and ezetimibe have little effect on Lp(a) levels. Therapies such as niacin or cholesterol ester transfer protein (CETP) inhibitors lower Lp(a) as well as reducing other lipid-related risk factors but have failed to clearly reduce CVD events. Proprotein convertase subtilisin kexin-9 (PCSK9) inhibitors reduce cholesterol and Lp(a) as well as reducing CVD events. New antisense therapies specifically targeting apo(a) and hence Lp(a) have greater and more specific effects and will help clarify the extent to which intervention in Lp(a) levels will reduce CVD events.

The Targeting of Native Proteins to the Endoplasmic Reticulum-Associated Degradation (ERAD) Pathway: An Expanding Repertoire of Regulated Substrates

All proteins are subject to quality control processes during or soon after their synthesis, and these cellular quality control pathways play critical roles in maintaining homeostasis in the cell and in organism health. Protein quality control is particularly vital for those polypeptides that enter the endoplasmic reticulum (ER). Approximately one-quarter to one-third of all proteins synthesized in eukaryotic cells access the ER because they are destined for transport to the extracellular space, because they represent integral membrane proteins, or because they reside within one of the many compartments of the secretory pathway. However, proteins that mature inefficiently are subject to ER-associated degradation (ERAD), a multi-step pathway involving the chaperone-mediated selection, ubiquitination, and extraction (or “retrotranslocation”) of protein substrates from the ER. Ultimately, these substrates are degraded by the cytosolic proteasome. Interestingly, there is an increasing number of native enzymes and metabolite and solute transporters that are also targeted for ERAD. While some of these proteins may transiently misfold, the ERAD pathway also provides a route to rapidly and quantitatively downregulate the levels and thus the activities of a variety of proteins that mature or reside in the ER.

Emerging RNA Therapeutics to Lower Blood Levels of Lp(a): JACC Focus Seminar 2/4

Lipoprotein(a) [Lp(a)] has risen to the level of an accepted cardiovascular disease risk factor, but final proof of causality awaits a randomized trial of Lp(a) lowering. Inhibiting apolipoprotein(a) production in the hepatocyte with ribonucleic acid therapeutics has emerged as an elegant and effective solution to reduce plasma Lp(a) levels. Phase 2 clinical trials have shown that the antisense oligonucleotide pelacarsen reduced mean Lp(a) levels by 80%, allowing 98% of subjects to reach on-treatment levels of <125 nmol/l (∼50 mg/dl). The phase 3 Lp(a)HORIZON (Assessing the Impact of Lipoprotein(a) Lowering With TQJ230 on Major Cardiovascular Events in Patients With CVD) outcomes trial is currently enrolling approximately 7,680 patients with history of myocardial infarction, ischemic stroke, and symptomatic peripheral arterial disease and controlled low-density lipoprotein cholesterol to pelacarsen versus placebo. The co-primary endpoints are major adverse cardiovascular events in subjects with Lp(a) >70 mg/dl and >90 mg/dl, in which either of the two being positive will lead to a successful trial. Additional ribonucleic acid-targeted therapies to lower Lp(a) are in preclinical and clinical development. The testing of the Lp(a) hypothesis will provide proof whether Lp(a)-mediated risk can be abolished by potent Lp(a) lowering.

Lp(a) (Lipoprotein[a]) Concentrations and Incident Atherosclerotic Cardiovascular Disease: New Insights From a Large National Biobank

OBJECTIVE

Lp(a) (lipoprotein[a]) concentrations are associated with atherosclerotic cardiovascular disease (ASCVD), and new therapies that enable potent and specific reduction are in development. In the largest study conducted to date, we address 3 areas of uncertainty: (1) the magnitude and shape of ASCVD risk conferred across the distribution of lipoprotein(a) concentrations; (2) variation of risk across racial and clinical subgroups; (3) clinical importance of a high lipoprotein(a) threshold to guide therapy. Approach and Results: Relationship of lipoprotein(a) to incident ASCVD was studied in 460 506 middle-aged UK Biobank participants. Over a median follow-up of 11.2 years, incident ASCVD occurred in 22 401 (4.9%) participants. Median lipoprotein(a) concentration was 19.6 nmol/L (25th-75th percentile 7.6-74.8). The relationship between lipoprotein(a) and ASCVD appeared linear across the distribution, with a hazard ratio of 1.11 (95% CI, 1.10-1.12) per 50 nmol/L increment. Substantial differences in concentrations were noted according to race-median values for white, South Asian, black, and Chinese individuals were 19, 31, 75, and 16 nmol/L, respectively. However, risk per 50 nmol/L appeared similar-hazard ratios of 1.11, 1.10, and 1.07 for white, South Asian, and black individuals, respectively. A high lipoprotein(a) concentration defined as ≥150 nmol/L was present in 12.2% of those without and 20.3% of those with preexisting ASCVD and associated with hazard ratios of 1.50 (95% CI, 1.44-1.56) and 1.16 (95% CI, 1.05-1.27), respectively.

CONCLUSIONS

Lipoprotein(a) concentrations predict incident ASCVD among middle-aged adults within primary and secondary prevention contexts, with a linear risk gradient across the distribution. Concentrations are variable across racial subgroups, but the associated risk appears similar.

Antisense lipoprotein[a] therapy: State-of-the-art and future perspectives

Several lines of evidence now attest that lipoprotein[a] (Lp[a]) is a significant risk factor for many cardiovascular disorders. This enigmatic lipoprotein, composed of a single copy of apolipoprotein B (apoB) and apolipoprotein[a] (apo [a]), expresses peculiar metabolism, virtually independent from lifestyle interventions. Several therapeutic options have hence been proposed for lowering elevated Lp[a] values, with or without concomitant effect on low density lipoprotein (LDL) particles, mostly encompassing statins, ezetimibe, nicotinic acid, lipoprotein apheresis, and anti-PCSK9 monoclonal antibodies. Since all these medical treatments have some technical and clinical drawbacks, a novel strategy is currently being proposed, based on the use of antisense apo[a] and/or apoB inhibitors. Although the role of these agents in hypercholesterolemic patients is now nearby entering clinical practice, the collection of information on Lp[a] is still underway. Preliminary evidence would suggest that apo[a] antisense therapy seems more appropriate in patients with isolated Lp[a] elevations, while apoB antisense therapy is perhaps more advisable in patients with isolated LDL elevations. In patients with concomitant elevations of Lp[a] and LDL, either combining the two apo[a] and apoB antisense therapies (a strategy which has never been tested), or the combination of well-known and relatively inexpensive drugs such as statins with antisense apo[a] inhibitors can be theoretically suggested. The results of an upcoming phase 3 study with antisense apo[a] inhibitors will hopefully provide definitive clues as to whether this approach may become the standard of care in patients with increased Lp[a] concentrations.

Lindholm M, Koch T. Nuclear and Cytoplasmatic Quantification of Unconjugated, Label-Free Locked Nucleic Acid Oligonucleotides

Methods for the quantification of antisense oligonucleotides (AONs) provide insightful information on biodistribution and intracellular trafficking. However, the established methods have not provided information on the absolute number of molecules in subcellular compartments or about how many AONs are needed for target gene reduction for unconjugated AONs. We have developed a new method for nuclear AON quantification that enables us to determine the absolute number of AONs per nucleus without relying on AON conjugates such as fluorophores that may alter AON distribution. This study describes an alternative and label-free method using subcellular fractionation, nucleus counting, and locked nucleic acid (LNA) sandwich enzyme-linked immunosorbent assay to quantify absolute numbers of oligonucleotides in nuclei. Our findings show compound variability (diversity) by which 247,000-693,000 LNAs/nuclei results in similar target reduction for different compounds. This method can be applied to any antisense drug discovery platform providing information on specific and clinically relevant AONs. Finally, this method can directly compare nuclear entry of AON with target gene knockdown for any compound design and nucleobase sequence, gene target, and phosphorothioate stereochemistry.

Lipoprotein(a) Reduction in Persons with Cardiovascular Disease

BACKGROUND

Lipoprotein(a) levels are genetically determined and, when elevated, are a risk factor for cardiovascular disease and aortic stenosis. There are no approved pharmacologic therapies to lower lipoprotein(a) levels.

METHODS

We conducted a randomized, double-blind, placebo-controlled, dose-ranging trial involving 286 patients with established cardiovascular disease and screening lipoprotein(a) levels of at least 60 mg per deciliter (150 nmol per liter). Patients received the hepatocyte-directed antisense oligonucleotide AKCEA-APO(a)-L_Rx, referred to here as APO(a)-L_Rx (20, 40, or 60 mg every 4 weeks; 20 mg every 2 weeks; or 20 mg every week), or saline placebo subcutaneously for 6 to 12 months. The lipoprotein(a) level was measured with an isoform-independent assay. The primary end point was the percent change in lipoprotein(a) level from baseline to month 6 of exposure (week 25 in the groups that received monthly doses and week 27 in the groups that received more frequent doses).

RESULTS

The median baseline lipoprotein(a) levels in the six groups ranged from 204.5 to 246.6 nmol per liter. Administration of APO(a)-L_Rx resulted in dose-dependent decreases in lipoprotein(a) levels, with mean percent decreases of 35% at a dose of 20 mg every 4 weeks, 56% at 40 mg every 4 weeks, 58% at 20 mg every 2 weeks, 72% at 60 mg every 4 weeks, and 80% at 20 mg every week, as compared with 6% with placebo (P values for the comparison with placebo ranged from 0.003 to <0.001). There were no significant differences between any APO(a)-L_Rx dose and placebo with respect to platelet counts, liver and renal measures, or influenza-like symptoms. The most common adverse events were injection-site reactions.

CONCLUSIONS

APO(a)-L_Rx reduced lipoprotein(a) levels in a dose-dependent manner in patients who had elevated lipoprotein(a) levels and established cardiovascular disease. (Funded by Akcea Therapeutics; ClinicalTrials.gov number, NCT03070782.).

Potential Causality and Emerging Medical Therapies for Lipoprotein(a) and Its Associated Oxidized Phospholipids in Calcific Aortic Valve Stenosis

The prevalence of calcific aortic valve disease is increasing with aging of the population. Current treatment options for advanced or symptomatic aortic stenosis are limited to traditional surgical or percutaneous aortic valve replacement. Medical therapies that impact the progression of calcific aortic valve disease do not currently exist. New pathophysiological insights suggest that the processes leading to calcific aortic valve disease are metabolically active for many years before and during the clinical expression of disease. The identification of genetic and potentially causal mediators of calcific aortic valve disease allows opportunities for therapies that may slow progression to the point where aortic valve replacement can be avoided. Recent studies suggest that approximately one-third of aortic stenosis cases are associated with highly elevated lipoprotein(a) [Lp(a)] and pathways related to the metabolism of procalcifying oxidized phospholipids. Oxidized phospholipids can be carried by Lp(a) into valve leaflets but can also be formed in situ from cell membranes, lipoproteins, and apoptotic cells. This review will summarize the clinical data implicating the potential causality of Lp(a)/oxidized phospholipids, describe emerging therapeutic agents, and propose clinical trial designs to test the hypothesis that lowering Lp(a) will reduce progression aortic stenosis and the need for aortic valve replacement.

Lipid-Lowering Agents

Several new or emerging drugs for dyslipidemia owe their existence, in part, to human genetic evidence, such as observations in families with rare genetic disorders or in Mendelian randomization studies. Much effort has been directed to agents that reduce LDL (low-density lipoprotein) cholesterol, triglyceride, and Lp[a] (lipoprotein[a]), with some sustained programs on agents to raise HDL (high-density lipoprotein) cholesterol. Lomitapide, mipomersen, AAV8.TBG.hLDLR, inclisiran, bempedoic acid, and gemcabene primarily target LDL cholesterol. Alipogene tiparvovec, pradigastat, and volanesorsen primarily target elevated triglycerides, whereas evinacumab and IONIS-ANGPTL3-L_Rx target both LDL cholesterol and triglyceride. IONIS-APO(a)-L_Rx targets Lp(a).

Structural basis for the synergy of 4'- and 2'-modifications on siRNA nuclease resistance, thermal stability and RNAi activity

Chemical modification is a prerequisite of oligonucleotide therapeutics for improved metabolic stability, uptake and activity, irrespective of their mode of action, i.e. antisense, RNAi or aptamer. Phosphate moiety and ribose C2′/O2′ atoms are the most common sites for modification. Compared to 2′-O-substituents, ribose 4′-C-substituents lie in proximity of both the 3′- and 5′-adjacent phosphates. To investigate potentially beneficial effects on nuclease resistance we combined 2′-F and 2′-OMe with 4′-Cα- and 4′-Cβ-OMe, and 2′-F with 4′-Cα-methyl modification. The α- and β-epimers of 4′-C-OMe-uridine and the α-epimer of 4′-C-Me-uridine monomers were synthesized and incorporated into siRNAs. The 4′α-epimers affect thermal stability only minimally and show increased nuclease stability irrespective of the 2′-substituent (H, F, OMe). The 4′β-epimers are strongly destabilizing, but afford complete resistance against an exonuclease with the phosphate or phosphorothioate backbones. Crystal structures of RNA octamers containing 2′-F,4′-Cα-OMe-U, 2′-F,4′-Cβ-OMe-U, 2′-OMe,4′-Cα-OMe-U, 2′-OMe,4′-Cβ-OMe-U or 2′-F,4′-Cα-Me-U help rationalize these observations and point to steric and electrostatic origins of the unprecedented nuclease resistance seen with the chain-inverted 4′β-U epimer. We used structural models of human Argonaute 2 in complex with guide siRNA featuring 2′-F,4′-Cα-OMe-U or 2′-F,4′-Cβ-OMe-U at various sites in the seed region to interpret in vitro activities of siRNAs with the corresponding 2′-/4′-C-modifications.

Antisense Oligonucleotides Targeting Lipoprotein(a)

PURPOSE OF REVIEW

High lipoprotein(a) levels are observationally and causally, from human genetics, associated with increased risk of cardiovascular disease including myocardial infarction and aortic valve stenosis. The European Atherosclerosis Society recommends screening for elevated lipoprotein(a) levels in high-risk patients. Different therapies have been suggested and some are used to treat elevated lipoprotein(a) levels such as niacin, PCSK9 inhibitors, and CETP inhibitors; however, to date, no randomized controlled trial has demonstrated that lowering of lipoprotein(a) leads to lower risk of cardiovascular disease.

RECENT FINDINGS

Synthetic oligonucleotides can be used to inactivate genes involved in disease processes. To lower lipoprotein(a), two antisense oligonucleotides have been developed, one targeting apolipoprotein B and one targeting apolipoprotein(a). Mipomersen is an antisense oligonucleotide targeting apolipoprotein B and thereby reducing levels of all apolipoprotein B containing lipoproteins in the circulation. Mipomersen has been shown to lower lipoprotein(a) by 20-50% in phase 3 studies. AKCEA-APO(a)-L_Rx is the most recent antisense oligonucleotide targeting apolipoprotein(a) and thereby uniquely targeting lipoprotein(a). It has been tested in a phase 2 study and has shown to lower lipoprotein(a) levels by 50-80%. The treatment of elevated lipoprotein(a) levels with the newest antisense oligonucleotides seems promising; however, no improvement in cardiovascular disease risk has yet been shown. However, a phase 3 study of AKCEA-APO(a)-L_Rx is being planned with cardiovascular disease as outcome, and results are awaited with great anticipation.

Re-Engineering RNA Molecules into Therapeutic Agents

Efforts to chemically modify nucleic acids got underway merely a decade after the discovery of the DNA double helix and initially targeted nucleosides and nucleotides. The origins of three analogues that remain staples of modification strategies and figure prominently in FDA-approved nucleic acid therapeutics can be traced to the 1960s: 2'-deoxy-2'-fluoro-RNA (2'-F RNA), 2'- O-methyl-RNA (2'- OMe RNA), and the phosphorothioates (PS-DNA/RNA). Progress in nucleoside phosphoramidite-based solid phase oligonucleotide synthesis has gone hand in hand with the creation of second-generation (e.g., 2'- O-(2-methoxyethyl)-RNA, MOE-RNA) and third-generation (e.g., bicyclic nucleic acids, BNAs) analogues, giving rise to an expanding universe of modified nucleic acids. Thus, beyond site-specifically altered DNAs and RNAs with a modified base, sugar, and/or phosphate backbone moieties, nucleic acid chemists have created a host of conjugated oligonucleotides and artificial genetic polymers (XNAs). The search for oligonucleotides with therapeutic efficacy constitutes a significant driving force for these investigations. However, nanotechnology, diagnostics, synthetic biology and genetics, nucleic acid etiology, and basic research directed at the properties of native and artificial pairing systems have all stimulated the design of ever more diverse modifications. Modification of nucleic acids can affect pairing and chemical stability, conformation and interactions with a flurry of proteins and enzymes that play important roles in uptake, transport or processing of targets. Enhancement of metabolic stability is a central concern in the design of antisense, siRNA and aptamer oligonucleotides for therapeutic applications. In the antisense approach, uniformly modified oligonucleotides or so-called gapmers are used to target a specific RNA. The former may sterically block transcription or direct alternative splicing, whereas the latter feature a central PS window that elicits RNase H-mediated cleavage of the target. The key enzyme in RNA interference (RNAi) is Argonaute 2 (Ago2), a dynamic multidomain enzyme that binds multiple regions of the guide (antisense) and passenger (sense) siRNAs. The complexity of the individual interactions between Ago2 and the siRNA duplex provides significant challenges for chemical modification. Therefore, a uniform (the same modification throughout, e.g., antisense) or nearly uniform (e.g., aptamer) modification strategy is less useful in the pursuit of siRNA therapeutic leads. Instead, unique structural features and protein interactions of 5'-end (guide/Ago2MID domain), seed region, central region (cleavage site/Ago2 PIWI domain), and 3'-terminal nucleotides (guide/Ago2 PAZ domain) demand a more nuanced approach in the design of chemically modified siRNAs for therapeutic use. This Account summarizes current siRNA modification strategies with an emphasis on the regio-specific interactions between oligonucleotide and Ago2 and how these affect the choice of modification and optimization of siRNA efficacy. In addition to standard assays applied to measure the effects of modification on the stability of pairing and resistance against nuclease degradation, structural insights based on crystallographic data for modified RNAs alone and in complex with Ago2 from molecular modeling studies are a valuable guide in the design of siRNA therapeutics. Thus, this comprehensive approach is expected to result in accelerated generation of new siRNA-based therapies against various diseases, now that the first siRNA has obtained approval by the US FDA for treatment of hereditary hATTR amyloidosis.

Lipoprotein(a) catabolism: a case of multiple receptors

Lipoprotein(a) [Lp(a)] is an apolipoprotein B (apoB)-containing plasma lipoprotein similar in structure to low-density lipoprotein (LDL). Lp(a) is more complex than LDL due to the presence of apolipoprotein(a) [apo(a)], a large glycoprotein sharing extensive homology with plasminogen, which confers some unique properties onto Lp(a) particles. ApoB and apo(a) are essential for the assembly and catabolism of Lp(a); however, other proteins associated with the particle may modify its metabolism. Lp(a) specifically carries a cargo of oxidised phospholipids (OxPL) bound to apo(a) which stimulates many proinflammatory pathways in cells of the arterial wall, a key property underlying its pathogenicity and association with cardiovascular disease (CVD). While the liver and kidney are the major tissues implicated in Lp(a) clearance, the pathways for Lp(a) uptake appear to be complex and are still under investigation. Biochemical studies have revealed an exceptional array of receptors that associate with Lp(a) either via its apoB, apo(a), or OxPL components. These receptors fall into five main categories, namely 'classical' lipoprotein receptors, toll-like and scavenger receptors, lectins, and plasminogen receptors. The roles of these receptors have largely been dissected by genetic manipulation in cells or mice, although their relative physiological importance for removal of Lp(a) from the circulation remains unclear. The LPA gene encoding apo(a) has an overwhelming effect on Lp(a) levels which precludes any clear associations between potential Lp(a) receptor genes and Lp(a) levels in population studies. Targeted approaches and the selection of unique Lp(a) phenotypes within populations has nevertheless allowed for some associations to be made. Few of the proposed Lp(a) receptors can specifically be manipulated with current drugs and, as such, it is not currently clear whether any of these receptors could provide relevant targets for therapeutic manipulation of Lp(a) levels. This review summarises the current status of knowledge about receptor-mediated pathways for Lp(a) catabolism.

Nucleic acids delivering nucleic acids

Nucleic acid therapeutics, including siRNAs, miRNAs/antimiRs, gRNAs and ASO, represent innovative and highly promising molecules for the safe treatment of a wide range of pathologies. The efficiency of systemic treatments is impeded by 1) the need to overcome physical and functional barriers in the organism, and 2) to accumulate in the intracellular active site at therapeutic concentrations. Although oligonucleotides either as modified naked molecules or complexed with delivery carriers have revealed to be effectively delivered to the affected target cells, this is restricted to topic treatments or to a few highly vascularized tissues. Therefore, the development of effective strategies for therapeutic nucleic acid selective delivery to target tissues is of primary importance in order to reduce the occurrence of undesired effects on non-target healthy tissues and to permit their translation to clinic. Due to their high affinity for specific ligands, high tissue penetration and chemical flexibility, short single-stranded nucleic acid aptamers are emerging as very attractive carriers for various therapeutic oligonucleotides. Yet, different aptamer-based bioconjugates, able to provide accumulation into target tissues, as well as efficient processing of therapeutic oligonucleotides, have been developed. In this respect, nucleic acid aptamer-mediated delivery strategies represent a powerful approach able to increase the therapeutic efficacy also highly reducing the overall toxicity. In this review, we will summarize recent progress in the field and discuss achieved objectives and optimization of aptamers as delivery carriers of short oligonucleotides.

Advances in Biomaterials for Drug Delivery

Advances in biomaterials for drug delivery are enabling significant progress in biology and medicine. Multidisciplinary collaborations between physical scientists, engineers, biologists, and clinicians generate innovative strategies and materials to treat a range of diseases. Specifically, recent advances include major breakthroughs in materials for cancer immunotherapy, autoimmune diseases, and genome editing. Here, strategies for the design and implementation of biomaterials for drug delivery are reviewed. A brief history of the biomaterials field is first established, and then commentary on RNA delivery, responsive materials development, and immunomodulation are provided. Current challenges associated with these areas as well as opportunities to address long-standing problems in biology and medicine are discussed throughout.

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.

Enzymatic separation of epimeric 4-C-hydroxymethylated furanosugars: Synthesis of bicyclic nucleosides

Conversion of D-glucose to 4-C-hydroxymethyl-1,2-O-isopropylidene-α-D-ribofuranose, which is a key precursor for the synthesis of different types of bicyclic/spiro nucleosides, led to the formation of an inseparable 1:1 mixture of the desired product and 4-C-hydroxymethyl-1,2-O-isopropylidene-α-D-xylofuranose. A convenient environment friendly Novozyme^®-435 catalyzed selective acetylation methodology has been developed for the separation of an epimeric mixture of ribo- and xylotrihydroxyfuranosides in quantitative yields. The structure of both the monoacetylated epimers, i.e., 5-O-acetyl-4-C-hydroxymethyl-1,2-O-isopropylidene-α-D-ribo- and xylofuranose obtained by enzymatic acetylation, has been confirmed by an X-ray study on their corresponding 4-C-p-toluenesulfonyloxymethyl derivatives. Furthermore, the two separated epimers were used for the convergent synthesis of two different types of bicyclic nucleosides, which confirms their synthetic utility.

A Test in Context: Lipoprotein(a): Diagnosis, Prognosis, Controversies, and Emerging Therapies

Evidence that elevated lipoprotein(a) (Lp[a]) levels contribute to cardiovascular disease (CVD) and calcific aortic valve stenosis (CAVS) is substantial. Development of isoform-independent assays, in concert with genetic, epidemiological, translational, and pathophysiological insights, have established Lp(a) as an independent, genetic, and likely causal risk factor for CVD and CAVS. These observations are consistent across a broad spectrum of patients, risk factors, and concomitant therapies, including patients with low-density lipoprotein cholesterol <70 mg/dl. Statins tend to increase Lp(a) levels, possibly contributing to the "residual risk" noted in outcomes trials and at the bedside. Recently approved proprotein convertase subtilisin/kexin-type 9 inhibitors and mipomersen lower Lp(a) 20% to 30%, and emerging RNA-targeted therapies lower Lp(a) >80%. These approaches will allow testing of the "Lp(a) hypothesis" in clinical trials. This review summarizes the current landscape of Lp(a), discusses controversies, and reviews emerging therapies to reduce plasma Lp(a) levels to decrease risk of CVD and CAVS.

Advances in the delivery of RNA therapeutics: from concept to clinical reality

The rapid expansion of the available genomic data continues to greatly impact biomedical science and medicine. Fulfilling the clinical potential of genetic discoveries requires the development of therapeutics that can specifically modulate the expression of disease-relevant genes. RNA-based drugs, including short interfering RNAs and antisense oligonucleotides, are particularly promising examples of this newer class of biologics. For over two decades, researchers have been trying to overcome major challenges for utilizing such RNAs in a therapeutic context, including intracellular delivery, stability, and immune response activation. This research is finally beginning to bear fruit as the first RNA drugs gain FDA approval and more advance to the final phases of clinical trials. Furthermore, the recent advent of CRISPR, an RNA-guided gene-editing technology, as well as new strides in the delivery of messenger RNA transcribed in vitro, have triggered a major expansion of the RNA-therapeutics field. In this review, we discuss the challenges for clinical translation of RNA-based therapeutics, with an emphasis on recent advances in delivery technologies, and present an overview of the applications of RNA-based drugs for modulation of gene/protein expression and genome editing that are currently being investigated both in the laboratory as well as in the clinic.

Construction of DNAzyme-Encapsulated Fibermats Using the Precursor Network Polymer of Poly(γ-glutamate) and 4-Glycidyloxypropyltrimethoxysilane

Here, we developed functional nucleic acid (FNA)-encapsulated electrospun fibermats. To facilitate stable FNA encapsulation in the γ-PGA/GPTMS fibermats, we used the FNA as an FNA/streptavidin complex, and as a representative FNA, we selected a DNAzyme, the DNA/hemin complex, which is composed of G-quadraplex-forming single-stranded DNA and hemin and exhibits oxidation activity with the aid of a cocatalyst, H₂O₂. Scanning electron microscopy and Fourier-transform infrared spectroscopy measurements revealed that encapsulation of the DNA/hemin complex (∼1 wt % against the γ-PGA/GPTMS hybrid) in the nanofibers of the γ-PGA/GPTMS fibermats did not affect the structure of the original nanofibers. However, because a unique MW-dependent molecular permeability originated from the 3D network structure of the γ-PGA/GPTMS hybrid, low-MW substrates such as 4-aminoantipyrine, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3-methylaniline, and luminol were able to reach the encapsulated DNA/hemin complex by permeating to the inside of the nanofibers from an immersion buffer and then underwent catalytic oxidation. Conversely, nucleases, which are proteins featuring high MWs (>5 kDa), could not penetrate the γ-PGA/GPTMS nanofibers, and the encapsulated DNA/hemin complex was therefore effectively protected against nuclease digestion. Thus, encapsulating FNAs on the inside of the nanofibers of fibermats offers clear advantages for the practical application of FNAs in sensors and drugs, particularly for use in the in vivo circumstances.

SIDT2 mediates gymnosis, the uptake of naked single-stranded oligonucleotides into living cells

Single-stranded oligonucleotides (ssOligos) are efficiently taken up by living cells without the use of transfection reagents. This phenomenon called ‘gymnosis’ enables the sequence-specific silencing of target genes in various types of cells. Several antisense ssOligos are used for the treatment of human diseases. However, the molecular mechanism underlying the uptake of naked ssOligos into cells remains to be elucidated. Here, we show that systemic RNA interference deficient-1 (SID-1) transmembrane family 2 (SIDT2), a mammalian ortholog of the Caenorhabditis elegans double-stranded RNA channel SID-1, mediates gymnosis. We show that the uptake of naked ssOligos into cells is significantly downregulated by knockdown of SIDT2. Furthermore, knockdown of SIDT2 inhibited the effect of antisense RNA mediated by gymnosis. Overexpression of SIDT2 enhanced the uptake of naked ssOligos into cells, while a single amino acid mutation in SIDT2 abolished this effect. Our findings highlight the mechanism of extra- and intracellular RNA transport and may contribute to the further development of nucleic acid-based therapies.

A phase 1 study to evaluate the safety and LDL cholesterol-lowering effects of RG7652, a fully human monoclonal antibody against proprotein convertase subtilisin/kexin type 9

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) downregulates low-density lipoprotein (LDL) receptors, thereby leading to a rise in circulating LDL cholesterol (LDL-C). RG7652 is a fully human monoclonal antibody against PCSK9. This placebo-controlled, phase 1 ascending-dose study in healthy subjects evaluated the safety of RG7652 and its efficacy as a potential LDL-C-lowering drug.

HYPOTHESIS

Anti-PCSK9 antibody therapy safely and effectively reduces LDL-C.

METHODS

Subjects (N = 80) were randomized into 10 cohorts. Six sequential single-dose cohorts received 10, 40, 150, 300, 600, or 800 mg of RG7652 via subcutaneous injection. Four multiple-dose cohorts received 40 or 150 mg of RG7652 once weekly for 4 weeks, either with or without statin therapy (atorvastatin).

RESULTS

Adverse events (AEs) were generally mild; the most common AEs were temporary injection-site reactions. No serious AEs, severe AEs, AEs leading to study-drug discontinuation, or dose-limiting toxicities were reported. RG7652 monotherapy reduced mean LDL-C levels by up to 64% and as much as 100 mg/dL at week 2; the effect magnitude and duration increased with dose (≥57 days following a single RG7652 dose ≥300 mg). Exploratory analyses showed reduced oxidized LDL, lipoprotein(a), and lipoprotein-associated phospholipase A2 with RG7652. Antidrug antibody against RG7652 tested positive in 2 of 60 (3.3%) RG7652-treated and in 4 of 20 (20.0%) placebo-treated subjects. Simultaneous atorvastatin administration did not appear to impact the pharmacokinetic profile or lipid-lowering effects of RG7652.

CONCLUSIONS

Overall, RG7652 elicited substantial and sustained dose-related LDL-C reductions with an acceptable safety profile and minimal immunogenicity.

Pre-mRNA mis-splicing of sarcomeric genes in heart failure

Pre-mRNA splicing is an important biological process that allows production of multiple proteins from a single gene in the genome, and mainly contributes to protein diversity in eukaryotic organisms. Alternative splicing is commonly governed by RNA binding proteins to meet the ever-changing demands of the cell. However, the mis-splicing may lead to human diseases. In the heart of human, mis-regulation of alternative splicing has been associated with heart failure. In this short review, we focus on alternative splicing of sarcomeric genes and review mis-splicing related heart failure with relatively well studied Sarcomeric genes and splicing mechanisms with identified regulatory factors. The perspective of alternative splicing based therapeutic strategies in heart failure has also been discussed.

Development of Antisense Drugs for Dyslipidemia

Abnormal elevation of low-density lipoprotein (LDL) and triglyceride-rich lipoproteins in plasma as well as dysfunction of anti-atherogenic high-density lipoprotein (HDL) have both been recognized as essential components of the pathogenesis of atherosclerosis and are classified as dyslipidemia. This review describes the arc of development of antisense oligonucleotides for the treatment of dyslipidemia. Chemically-armed antisense candidates can act on various kinds of transcripts, including mRNA and miRNA, via several different endogenous antisense mechanisms, and have exhibited potent systemic anti-dyslipidemic effects. Here, we present specific cutting-edge technologies have recently been brought into antisense strategies, and describe how they have improved the potency of antisense drugs in regard to pharmacokinetics and pharmacodynamics. In addition, we discuss perspectives for the use of armed antisense oligonucleotides as new clinical options for dyslipidemia, in the light of outcomes of recent clinical trials and safety concerns indicated by several clinical and preclinical studies.

Lipoprotein(a) and risk of sudden cardiac death in middle-aged Finnish men: A new prospective cohort study

BACKGROUND

Lipoprotein(a) [Lp(a)] is an established and independent risk factor for cardiovascular outcomes. However, the relationship of Lp(a) with risk of sudden cardiac death (SCD) is unknown. We aimed to assess the association of Lp(a) with risk of SCD in the Kuopio Ischemic Heart Disease prospective cohort study of 1881 men aged 42-61years at recruitment.

METHODS AND RESULTS

Plasma Lp(a) concentration was assessed at baseline and repeat measurements made several years apart. After a median follow-up of 24.7years, 141 SCDs were recorded. Hazard ratios (HRs) (95% confidence intervals [CI]) were assessed and were corrected for within-person variability in Lp(a) levels. The regression dilution ratio of loge Lp(a) adjusted for age was 0.84 (95% CI: 0.81-0.88). Lipoprotein(a) levels were log-linearly associated with risk of SCD. In analyses adjusted for established risk factors, the HR (95% CI) for SCD per 1 standard deviation (3.56-fold) higher baseline loge Lp(a) was 1.24 (1.05-1.47; P=0.013). This remained consistent on further adjustment for alcohol consumption, resting heart rate, lipids, and C-reactive protein 1.23 (1.04-1.46; P=0.018). HRs remained unchanged after accounting for incident coronary events and did not vary importantly in several relevant clinical subgroups. Adding Lp(a) to a SCD risk prediction model did not significantly improve risk discrimination beyond established risk factors, but improved the continuous net reclassification 30.2% (1.1 to 59.2%, P=0.042).

CONCLUSIONS

Available evidence shows a continuous and independent association between Lp(a) levels and risk of SCD. Further research is needed to replicate these findings.

A cellular high-throughput screening approach for therapeutic trans-cleaving ribozymes and RNAi against arbitrary mRNA disease targets

Major bottlenecks in development of therapeutic post transcriptional gene silencing (PTGS) agents (e.g. ribozymes, RNA interference, antisense) include the challenge of mapping rare accessible regions of the mRNA target that are open for annealing and cleavage, testing and optimization of agents in human cells to identify lead agents, testing for cellular toxicity, and preclinical evaluation in appropriate animal models of disease. Methods for rapid and reliable cellular testing of PTGS agents are needed to identify potent lead candidates for optimization. Our goal was to develop a means of rapid assessment of many RNA agents to identify a lead candidate for a given mRNA associated with a disease state. We developed a rapid human cell-based screening platform to test efficacy of hammerhead ribozyme (hhRz) or RNA interference (RNAi) constructs, using a model retinal degeneration target, human rod opsin (RHO) mRNA. The focus is on RNA Drug Discovery for diverse retinal degeneration targets. To validate the approach, candidate hhRzs were tested against NUH↓ cleavage sites (N = G,C,A,U; H = C,A,U) within the target mRNA of secreted alkaline phosphatase (SEAP), a model gene expression reporter, based upon in silico predictions of mRNA accessibility. HhRzs were embedded in a larger stable adenoviral VAI RNA scaffold for high cellular expression, cytoplasmic trafficking, and stability. Most hhRz expression plasmids exerted statistically significant knockdown of extracellular SEAP enzyme activity when readily assayed by a fluorescence enzyme assay intended for high throughput screening (HTS). Kinetics of PTGS knockdown of cellular targets is measureable in live cells with the SEAP reporter. The validated SEAP HTS platform was transposed to identify lead PTGS agents against a model hereditary retinal degeneration target, RHO mRNA. Two approaches were used to physically fuse the model retinal gene target mRNA to the SEAP reporter mRNA. The most expedient way to evaluate a large set of potential VAI-hhRz expression plasmids against diverse NUH↓ cleavage sites uses cultured human HEK293S cells stably expressing a dicistronic Target-IRES-SEAP target fusion mRNA. Broad utility of this rational RNA drug discovery approach is feasible for any ophthalmological disease-relevant mRNA targets and any disease mRNA targets in general. The approach will permit rank ordering of PTGS agents based on potency to identify a lead therapeutic compound for further optimization.

Unravelling the Secrets of Mycobacterial Cidality through the Lens of Antisense

One of the major impediments in anti-tubercular drug discovery is the lack of a robust grammar that governs the in-vitro to the in-vivo translation of efficacy. Mycobacterium tuberculosis (Mtb) is capable of growing both extracellular as well as intracellular; encountering various hostile conditions like acidic milieu, free radicals, starvation, oxygen deprivation, and immune effector mechanisms. Unique survival strategies of Mtb have prompted researchers to develop in-vitro equivalents to simulate in-vivo physiologies and exploited to find efficacious inhibitors against various phenotypes. Conventionally, the inhibitors are screened on Mtb under the conditions that are unrelated to the in-vivo disease environments. The present study was aimed to (1). Investigate cidality of Mtb targets using a non-chemical inhibitor antisense-RNA (AS-RNA) under in-vivo simulated in-vitro conditions.(2). Confirm the cidality of the targets under in-vivo in experimental tuberculosis. (3). Correlate in-vitro vs. in-vivo cidality data to identify the in-vitro condition that best predicts in-vivo cidality potential of the targets. Using cidality as a metric for efficacy, and AS-RNA as a target-specific inhibitor, we delineated the cidality potential of five target genes under six different physiological conditions (replicating, hypoxia, low pH, nutrient starvation, nitrogen depletion, and nitric oxide).In-vitro cidality confirmed in experimental tuberculosis in BALB/c mice using the AS-RNA allowed us to identify cidal targets in the rank order of rpoB>aroK>ppk>rpoC>ilvB. RpoB was used as the cidality control. In-vitro and in-vivo studies feature aroK (encoding shikimate kinase) as an in-vivo mycobactericidal target suitable for anti-TB drug discovery. In-vitro to in-vivo cidality correlations suggested the low pH (R = 0.9856) in-vitro model as best predictor of in-vivo cidality; however, similar correlation studies in pathologically relevant (Kramnik) mice are warranted. In the acute infection phase for the high fidelity translation, the compound efficacy may also be evaluated in the low pH, in addition to the standard replication condition.

Lipoprotein(a): novel target and emergence of novel therapies to lower cardiovascular disease risk

PURPOSE OF REVIEW

This article summarizes recent observations on the role of lipoprotein(a) [Lp(a)] as a risk factor mediating cardiovascular disease.

RECENT FINDINGS

Lp(a) is a highly prevalent cardiovascular risk factor, with levels above 30 mg/dl affecting 20-30% of the global population. Up until now, no specific therapies have been developed to lower Lp(a) levels. Three major levels of evidence support the notion that elevated Lp(a) levels are a causal, independent, genetic risk factor for cardiovascular disease: epidemiologic studies and meta-analyses, genome-wide association studies and Mendelian randomization studies. Recent studies also have noted that individuals with low levels of Lp(a) are associated with a higher risk of incident type 2 diabetes mellitus, and conversely individuals with high levels have a lower risk, but this association does not appear to be causal. Novel therapies to lower Lp(a) include PCSK9 inhibitors and antisense oligonucleotides directly preventing translation of apolipoprotein(a) mRNA.

SUMMARY

With this robust and expanding clinical database, a reawakening of interest in Lp(a) as clinical risk factor is taking place. Trials are underway with novel drugs that substantially lower Lp(a) and may reduce its contribution to cardiovascular disease.

Lack of Interactions Between an Antisense Oligonucleotide with 2'-O-(2-Methoxyethyl) Modifications and Major Drug Transporters

ISIS 141923 is a model compound of 2'-O-(2-methoxyethyl) (2'-MOE) modified antisense oligonucleotides (ASOs). The purpose of this study is to determine whether ISIS 141923 is a substrate or an inhibitor against a panel of nine major uptake or efflux drug transporters, namely breast cancer resistance protein (BCRP), P-glycoprotein (P-gp), organic anion transporter (OAT)1, OAT3, organic cation transporter (OCT)1, OCT2, organic anion transporting polypeptide 1B (OATP1B)1, OATP1B3, and bile salt export pump (BSEP), in vitro. The uptake test system for transporters in the solute carrier (SLC) family (OAT1, OAT3, OCT1, OCT2, OATP1B1, and OATP1B3) was studied in Madin-Darby canine kidney (MDCK)-II cells transfected to express the transporters of interest. BCRP was studied using carcinoma colon-2 (Caco-2) cells with endogenously expressed BCRP. P-gp transporter was studied in MDCK-multi-drug resistance 1 (MDR1) cells, while BSEP was studied using Spodoptera frugiperda 9 (Sf9) membrane vesicles containing human BSEP. The ISIS 141293 concentrations evaluated were 10 and 100 μM for the substrate and inhibition study, respectively. Cellular uptake of ISIS 141923 was analyzed using a high performance liquid chromatography-mass spectrometry method, while concentrations of known substrates (used as positive controls) of each transporters evaluated were determined by radiometric detection. At 10 μM ISIS 141923, there was no significant transporter-mediated uptake of ISIS 141923 (P > 0.05) in the SLC family, and the efflux ratios were not above 2.0 for either BCRP or P-gp. Therefore, no transporter-mediated uptake of ISIS 141923 was observed by any of the nine transporters studied. At 100 μM ISIS 141923, the % inhibition was in the range of -16.0% to 19.0% for the nine transporters evaluated. Therefore, ISIS 141923 is not considered as an inhibitor of the nine transporters studied. Overall, the results from this study suggest that it is unlikely that ISIS 141923 or similar 2'-MOE ASOs would interact with small molecule drugs either as a victim (substrate) or perpetrator (inhibitor) of major transporters in humans. The results from available clinical drug-drug interaction studies conducted with this class of compounds to date are also supportive of this conclusion.