Recent Developments in Gene Therapy for Homozygous Familial Hypercholesterolemia

Established and Emerging Nucleic Acid Therapies for Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disease that leads to elevated low-density lipoprotein cholesterol levels and risk of coronary heart disease. Current therapeutic options for FH remain relatively limited and only partially effective in both lowering low-density lipoprotein cholesterol and modifying coronary heart disease risk. The unique characteristics of nucleic acid therapies to target the underlying cause of the disease can offer solutions unachievable with conventional medications. DNA- and RNA-based therapeutics have the potential to transform the care of patients with FH. Recent advances are overcoming obstacles to clinical translation of nucleic acid-based medications, including greater stability of the formulations as well as site-specific delivery, making gene-based therapy for FH an alternative approach for treatment of FH.

Significance of traditional herbal medicine for dyslipidemia

Dyslipidemia is a multifactorial disorder that is a causative factor and risk factor for cardiovascular disease. The incidence of dyslipidemia is expected to increase because of the presence of comorbidities. Although several lipid-lowering drugs have been developed and approved, they are not completely effective and are associated with side effects. Traditional herbal medicine (THM) represents an alternative and complementary approach for managing dyslipidemia because of its low toxicity and beneficial effects, such as anti-inflammatory and antioxidant effects. This review focuses on our current understanding of the antidyslipidemic effect of THMs and discusses the associated regulatory mechanisms. The current findings indicate that THM may lead to the development of novel therapeutic regimens for dyslipidemia.

Efficacy and Safety of Alirocumab in Children and Adolescents With Homozygous Familial Hypercholesterolemia: Phase 3, Multinational Open-Label Study

BACKGROUND

Despite progress in treating homozygous familial hypercholesterolemia, most patients do not achieve low-density lipoprotein cholesterol (LDL-C) targets. This study examined efficacy and safety of the PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitor, alirocumab, in pediatric patients (aged 8-17 years) with inadequately controlled homozygous familial hypercholesterolemia.

METHODS

In this open-label, single-arm, multinational, Phase 3 study, patients (n=18) received alirocumab 75 mg or 150 mg (bodyweight <50 kg/≥50 kg) every 2 weeks as an adjunct to background treatment. The primary endpoint was percent change in LDL-C from baseline to Week 12. Secondary endpoints included changes in LDL-C and other lipid parameters up to 48 weeks, safety/tolerability, and alirocumab pharmacokinetics.

RESULTS

The mean age of patients was 12.4 years; 16/18 (89%) had mutations in the low-density lipoprotein receptor gene (LDLR) and 2/18 (11%) had mutations in the LDLR adapter protein 1 gene (LDLRAP1). At baseline, mean LDL-C (standard deviation) was 373.0 (193.5) mg/dL, which decreased by 4.1% at Week 12 (primary endpoint) and 11.4%, 13.2%, and 0.4% at Weeks 4, 24, and 48, respectively. At Week 12, 9/18 (50%) patients achieved LDL-C reductions ≥15%. Mean absolute LDL-C decreases ranged from 25 to 52 mg/dL over follow-up. A post hoc analysis demonstrated heterogeneity of responses according to genotype. There were no unexpected safety/tolerability findings. Free PCSK9 was reduced to near zero for all patients at Weeks 12 and 24.

CONCLUSIONS

The study supports the efficacy and safety of alirocumab as a potential adjunct to treatment for some pediatric patients with homozygous familial hypercholesterolemia.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; NCT03510715.

New Trends and Therapies for Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is associated with an elevated risk of atherosclerosis. The finding of monogenic defects indicates higher atherosclerotic risk in comparison with hypercholesterolemia of other etiologies. However, in heterozygous FH, cardiovascular risk is heterogeneous and depends not only on high cholesterol levels but also on the presence of other biomarkers and genes. The development of atherosclerosis risk scores specific for heterozygous FH and the use of subclinical coronary atherosclerosis imaging help with identifying higher-risk individuals who may benefit from further cholesterol lowering with PCSK9 inhibitors. There is no question about the extreme high risk in homozygous FH, and intensive LDL-cholesterol-lowering therapy must be started as soon as possible. These patients have gained life free of events in comparison with the past, but a high atherosclerosis residual risk persists. Furthermore, there is also the issue of aortic and supra-aortic valve disease development. Newer therapies such as inhibitors of microsomal transfer protein and angiopoietin-like protein 3 have opened the possibility of LDL-cholesterol normalization in homozygous FH and may provide an alternative to lipoprotein apheresis for these patients. Gene-based therapies may provide more definite solutions for lowering high LDL cholesterol and consequent atherosclerosis risk for people with FH.

Perioperative Management and Clinical Outcomes of Liver Transplantation for Children with Homozygous Familial Hypercholesterolemia

Background and Objectives: Liver transplantation (LT) has been accepted as a life-saving option as a last resort for children with homozygous familial hypercholesterolemia (HoFH). Perioperative management of LT for HoFH poses extra challenges for clinicians largely due to premature atherosclerotic cardiovascular diseases (ASCVDs). We aimed to analyze our data of pediatric LT recipients with HoFH, with special attention paid to perioperative management and clinical outcomes. Materials and Methods: After obtaining approval from the local ethics committee, the clinical data of pediatric patients with HoFH who underwent LT at our institution between January 2014 and February 2021 were retrospectively studied. Results: Six pediatric LT recipients with HoFH were included in the analysis. Although ASCVDs were common before LT, all children with HoFH survived the perioperative period without in-hospital mortality. However, one patient experienced acute myocardial infarction two months following LT and was successfully treated with medical interventions. Post-LT metabolic improvement was shown by declines in serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels in the early post-LT period (for TC: 14.7 ± 3.2 mmol/L vs. 5.5 ± 1.8 mmol/L, p < 0.001; for LDL-C: 10.6 ± 2.2 mmol/L vs. 3.6 ± 1.2 mmol/L, p < 0.001, respectively) and at the last follow-up (for TC: 14.7 ± 3.2 mmol/L vs. 4.5 ± 0.9 mmol/L, p = 0.001; for LDL-C: 10.6 ± 2.2 mmol/L vs. 2.8 ± 0.6 mmol/L, p = 0.001, respectively). Dietary restrictions could be lifted after LT. However, three patients required restarting lipid-lowering therapy after LT due to suboptimal LDL-C levels and progression of ASCVDs. Conclusions: Our data suggest that LT can be a safe and feasible therapeutic option for well-selected patients with HoFH, offering relaxed dietary restrictions and remarkable reductions in LDL-C levels. However, concerns remain regarding progression of ASCVDs after LT.

The promising novel therapies for familial hypercholesterolemia

Background

The incidence of premature atherosclerotic cardiovascular disease in familial hypercholesterolemia (FH) is high. In recent years, novel therapeutic modalities have shown significant lipid‐lowering ability. In this paper, we summarize the recent developments in novel therapies for FH via the treatment of different targets and discuss the characteristics of each targeted therapy. Based on the process of protein synthesis, we attempt to summarize the direct‐effect targets including protein, RNA, and DNA.

Methods

For this systematic review, relevant studies are assessed by searching in several databases including PubMed, Web of Science, Scopus, and Google Scholar. The publications of original researches are considered for screening.

Results

Most drugs are protein‐targeted such as molecule‐based and monoclonal antibodies, including statins, ezetimibe, alirocumab, evolocumab, and evinacumab. Both antisense oligonucleotide (ASO) and small interfering RNA (siRNA) approaches, such as mipomersen, vupanorsen, inclisiran, and ARO‐ANG3, are designed to reduce the number of mRNA transcripts and then degrade proteins. DNA‐targeted therapies such as adeno‐associated virus or CRISPR–Cas9 modification could be used to deliver or edit genes to address a genetic deficiency and improve the related phenotype.

Conclusion

While the therapies based on different targets including protein, RNA, and DNA are on different stages of development, the mechanisms of these novel therapies may provide new ideas for precision medicine.

Cellular and Molecular Aspects of Managing Familial Hypercholesterolemia: Recent and Emerging Therapeutic Approaches

Familial hypercholesterolemia (FH) as a high-frequency genetic disorder is diagnosed based on family and/or patient's history of coronary heart disease (CHD) or some other atherosclerotic disease, LDL-C levels and/or clinical signs such as tendonous xantomata, arcus cornealis before age 45 years as well as functional mutation in the LDLR, apoB or PCSK9 gene. Its clinical features are detectable since early childhood. Early diagnosis and timely treatment increase life expectancy in most patients with FH. Current FH therapies decrease the level of low-density lipoprotein up to ≥50% from baseline with diet, pharmacotherapeutic treatment, lipid apheresis, and liver transplantation. The cornerstone of medical therapy is the use of more potent statins in higher doses, to which often ezetimibe has to be added, but some FH patients do not achieve the target LDL-C with this therapy Therefore, besides these and the most recent but already established therapeutic approaches including PCSK9 inhibitors, inclisiran, and bempedoic acid, new therapies are on the horizon such as gene therapy, CRISPR/Cas9 strategy etc. This paper focuses on cellular and molecular potential strategies for the treatment of FH.

Lessons learned from the evinacumab trials in the treatment of homozygous familial hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH) is a life-threatening disease characterized by extremely elevated LDL cholesterol (LDL-C) levels which result in premature atherosclerotic cardiovascular disease. As conventional lipid-lowering therapies, which mainly depend on LDL receptors for LDL particle clearance, remain insufficient for reaching the recommended LDL-C levels in HoFH, agents acting independently of LDL receptors, such as ANGPTL3 inhibitors, constitute a promising target. Evinacumab, a monoclonal antibody directed against ANGPTL3, was approved in the USA in 2021 for treating patients with HoFH. Evinacumab has shown an adequate safety profile with strong LDL-lowering efficacy. This review highlights the development path of evinacumab and provides insight on the lessons learned from trials as well as the hurdles facing accessibility.

Future of genetic therapies for rare genetic diseases: what to expect for the next 15 years?

Introduction

Rare genetic diseases affect millions of people worldwide. Most of them are caused by defective genes that impair quality of life and can lead to premature death. As genetic therapies aim to fix or replace defective genes, they are considered the most promising treatment for rare genetic diseases. Yet, as these therapies are still under development, it is still unclear whether they will be successful in treating these diseases. This study aims to address this gap by assessing researchers' opinions on the future of genetic therapies for the treatment of rare genetic diseases.

Methods

We conducted a global cross-sectional web-based survey of researchers who recently authored peer-reviewed articles related to rare genetic diseases.

Results

We assessed the opinions of 1430 researchers with high and good knowledge about genetic therapies for the treatment of rare genetic diseases. Overall, the respondents believed that genetic therapies would be the standard of care for rare genetic diseases before 2036, leading to cures after this period. CRISPR-Cas9 was considered the most likely approach to fixing or replacing defective genes in the next 15 years. The respondents with good knowledge believed that genetic therapies would only have long-lasting effects after 2036, while those with high knowledge were divided on this issue. The respondents with good knowledge on the subject believed that non-viral vectors are more likely to be successful in fixing or replacing defective genes in the next 15 years, while most of the respondents with high knowledge believed viral vectors would be more successful.

Conclusion

Overall, the researchers who participated in this study expect that in the future genetic therapies will greatly benefit the treatment of patients with rare genetic diseases.

Recent advances in genome editing for cardiovascular disease

PURPOSE OF REVIEW

This review highlights recent progress in applying genome editing to the study and treatment of cardiovascular disease (CVD).

RECENT FINDINGS

Recent work has shown that genome editing can be used to determine the pathogenicity of variants of unknown significance in patient-derived induced pluripotent stem cells. These cells can also be used to test therapeutic genome editing approaches in a personalized manner. Somatic genome editing holds great promise for the treatment of CVD, and important proof of concept experiments have already been performed in animal models. Here we briefly review recent progress in patient-derived cells, as well as the development of somatic genome-editing therapies for CVD, with a particular focus on liver and heart.

SUMMARY

Translating this technology into the clinic will require precise editing enzymes, efficient delivery systems, and mitigation of off-target events and immune responses. Further development of these technologies will improve diagnostics and enable permanent correction of some of the most severe forms of CVD.

Successful pharmacological management of a child with compound heterozygous familial hypercholesterolemia and review of the recent literature

Severe familial hypercholesterolemia (SFH) is characterized by markedly elevated low-density lipoprotein cholesterol (LDL-C) and severe early-onset cardiovascular disease if left untreated. We report on the decade-long therapeutic journey of a 15-year-old boy with SFH due to a severe compound heterozygous genotype. He presented at the age of 5 years with widespread xanthomas and LDL-C of 17.4 mmol/L. He was diagnosed with SFH, initially treated with colestyramine that was subsequently combined with simvastatin. At the age of 12 years, he was diagnosed to have supravalvular aortic stenosis and ezetimibe/atorvastatin was introduced in place of colestyramine/simvastatin. At the age of 14 years, he received triple therapy with evolocumab, initially at the recommended dose of 420 mg monthly and then reduced to 140 mg biweekly. Currently at the age of 15 years, he is on atorvastatin 40 mg ON, ezetimibe 10 mg OM, and evolocumab 140 mg biweekly, achieving LDL-C levels of 2.4 mmol/L. Genetic testing identified compound heterozygous mutations in the LDL receptor genes [c.(940 + 1_941-1) (1845 + 1_1846-1)dup] and exon 12, nucleotide c.1747 C > T, amino acid p.(His583Tyr). Medical management without lipoprotein apheresis can achieve target LDL-C in children with SFH. Our patient, who developed supravalvular aortic stenosis at the age of 12 years, needed early aggressive treatment when SFH guidelines and newer drugs for young children were unavailable. Our patient demonstrated that 140 mg biweekly of evolocumab has the same cholesterol-lowering effect as the recommended 420 mg monthly dose.

Homozygous familial hypercholesterolemia: what treatments are on the horizon?

PURPOSE OF REVIEW

Homozygous familial hypercholesterolemia (HoFH) is a rare disorder associated with early atherosclerotic disease due to impairment of the LDL receptor (LDLR) pathway. Because of their molecular defect, current treatment options have limited success in bringing HoFH patient to LDL-C target and morbidity and mortality remain high. We review current and upcoming therapies directed at HoFH, including gene therapy.

RECENT FINDINGS

Recent real-world studies have confirmed the strength in lomitapide as a treatment adjunct to statins and other lipid-lowering therapies in HoFH patients. The approval of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor monoclonal antibodies has also been a welcome addition to the treatment armamentarium offering an additional average reduction in LDL-C levels of 24% when added to background lipid-lowering therapies in this population. Although achieving adequate LDL-C levels in this population is difficult, there are several therapies on the horizon that may help more patients reach goal. Evinacumab, a monoclonal antibody against ANGPTL3, has been shown to substantially reduce LDL-C of an average of 49%, independently of residual LDLR activity. RNA interference targeting PCSK9 and ANGPTL3 shows promise in clinical trials. Adeno-associated virus-mediated gene transfer and gene editing techniques are in early clinical and preclinical development.

SUMMARY

LDL-C lowering in HoFH patients remains very challenging. However, novel treatment options are emerging. Upcoming therapies directed at PCSK9 and ANPTL3 may offer additional LDL-C reduction, to help patients achieve adequate LDL-C levels. Gene therapy and gene editing techniques, if proven effective, may offer a unique opportunity to treat patients with a one-time treatment.

Gene-based therapy in lipid management: the winding road from promise to practice

INTRODUCTION

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality. High plasma low-density lipoprotein cholesterol (LDL-C) levels are a key CVD-risk factor. Triglyceride-rich remnant particles and lipoprotein(a) (Lp[a]) are also causally related to CVD. Consequently, therapeutic strategies for lowering LDL-C and triglyceride levels are widely used in routine clinical practice; however, specific Lp(a) lowering agents are not available. Many patients do not achieve guideline-recommended lipid levels with currently available therapies; hence, novel targets and treatment modalities are eagerly sought.

AREAS COVERED

We discuss the milestones on the trajectory toward the full application of gene-based therapies in daily clinical practice. We describe the different methods, ranging from antisense oligonucleotides to liver-directed gene therapy and Crispr-cas9 modification to target the pivotal players in lipid metabolism: PCSK9, APOB, ANGPTL3, Lp(a), LDLR, and apoC-III.

EXPERT OPINION

While acknowledging their different stages of development, gene-based therapies are likely to invoke a paradigm shift in lipid management because they allow us to target previously undruggable targets. Moreover, their low dosing frequency, high target selectivity, and relatively predictable adverse event profile are considered major advantages over current lipid-lowering therapies.

Heart Disease and Stroke Statistics-2020 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports on the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2020 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population, metrics to assess and monitor healthy diets, an enhanced focus on social determinants of health, a focus on the global burden of cardiovascular disease, and further evidence-based approaches to changing behaviors, implementation strategies, and implications of the American Heart Association's 2020 Impact Goals.

RESULTS

Each of the 26 chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policy makers, media professionals, clinicians, healthcare administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

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).

Familial hypercholesterolemia treatments: Guidelines and new therapies

Familial hypercholesterolemia (FH) is a genetic disorder resulting from mutations in genes encoding proteins involved in the metabolism of low density lipoproteins (LDL) and characterized by premature cardiovascular disease due to the exposure to high levels of LDL-cholesterol (LDL-C) from birth. Thus, the early identification of FH subjects, followed by appropriate treatment is essential to prevent or at least delay the onset of cardiovascular events. However, FH is largely underdiagnosed; in addition, FH patients are frequently not adequately treated, despite the availability of several pharmacological therapies to significantly reduce LDL-C levels. Current guidelines recommend LDL-C targets for FH (either heterozygotes [HeFH] or homozygotes [HoFH]) <100 mg/dL (<2.6 mmol/L) for adults or <70 mg/dL (<1.8 mmol/L) for adults with CHD or diabetes, and <135 mg/dL (<3.5 mmol/L) for children. With the pharmacological options now available, which include statins as a first approach, ezetimibe, and the recently approved monoclonal antibodies targeting PCSK9, the guideline recommended LDL-C target levels can be achieved in the majority of heterozygous FH subjects, while for the most severe forms of homozygous FH, the addition of therapies such as lomitapide either with or without apheresis may be required.

New Therapeutic Approaches for Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a common genetic condition characterized by elevated plasma levels of low-density lipoprotein cholesterol (LDL-C), premature atherosclerotic cardiovascular disease, and considerable unmet medical need with conventional LDL-C-lowering therapies. Between 2012 and 2015, the US Food and Drug Administration approved four novel LDL-C-lowering agents for use in patients with FH based on the pronounced LDL-C-lowering efficacy of these medicines. We review the four novel approved agents, as well as promising LDL-C-lowering agents in clinical development, with a focus on their mechanism of action, efficacy in FH cohorts, and safety.

ATP-citrate lyase (ACLY) in lipid metabolism and atherosclerosis: An updated review

ATP citrate lyase (ACLY) is an important enzyme linking carbohydrate to lipid metabolism by generating acetyl-CoA from citrate for fatty acid and cholesterol biosynthesis. Mendelian randomization of large human cohorts has validated ACLY as a promising target for low-density-lipoprotein-cholesterol (LDL-C) lowering and cardiovascular protection. Among current ACLY inhibitors, Bempedoic acid (ETC-1002) is a first-in-class, prodrug-based direct competitive inhibitor of ACLY which regulates lipid metabolism by upregulating hepatic LDL receptor (LDLr) expression and activity. ACLY deficiency in hepatocytes protects from hepatic steatosis and dyslipidemia. In addition, pharmacological inhibition of ACLY by bempedoic acid, prevents dyslipidemia and attenuates atherosclerosis in hypercholesterolemic ApoE^-/- mice, LDLr^-/- mice, and LDLr^-/- miniature pigs. Convincing data from clinical trials have revealed that bempedoic acid significantly lowers LDL-C as monotherapy, combination therapy, and add-on with statin therapy in statin-intolerant patients. More recently, a phase 3 CLEAR Harmony clinical trial ("Safety and Efficacy of Bempedoic Acid to Reduce LDL Cholesterol") has shown that bempedoic acid reduces the level of LDL-C in hypercholesterolemic patients receiving guideline-recommended statin therapy with a good safety profile. Hereby, we provide a updated review of the expression, regulation, genetics, functions of ACLY in lipid metabolism and atherosclerosis, and highlight the therapeutic potential of ACLY inhibitors (such as bempedoic acid, SB-204990, and other naturally-occuring inhibitors) to treat atherosclerotic cardiovascular diseases. It must be pointed out that long-term large-scale clinical trials in high-risk patients, are warranted to validate whether ACLY represent a promising therapeutic target for pharmaceutic intervention of dyslipidemia and atherosclerosis; and assess the safety and efficacy profile of ACLY inhibitors in improving cardiovascular outcome of patients.

Gene Delivery in Lipid Research and Therapies

Cardiovascular disease is the leading cause of death worldwide, and elevated lipid levels is a major contributor. Gene delivery, which involves controlled transfer of nucleic acids into cells and tissues, has been widely used in research to study lipid metabolism and physiology. Several technologies have been developed to somatically overexpress, silence, or disrupt genes in animal models and have greatly advanced our knowledge of metabolism. This is particularly true with regard to the liver, which plays a central role in lipoprotein metabolism and is amenable to many delivery approaches. In addition to basic science applications, many of these delivery technologies have potential as gene therapies for both common and rare lipid disorders. This review discusses three major gene delivery technologies used in lipid research-including adeno-associated viral vector overexpression, antisense oligonucleotides and small interfering RNAs, and the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 genome editing system-and examines their potential therapeutic applications.

Efficient Gene Transfer to the Central Nervous System by Single-Stranded Anc80L65

Adeno-associated viral vectors (AAVs) have demonstrated potential in applications for neurologic disorders, and the discovery that some AAVs can cross the blood-brain barrier (BBB) after intravenous injection has further expanded these opportunities for non-invasive brain delivery. Anc80L65, a novel AAV capsid designed from in silico reconstruction of the viral evolutionary lineage, has previously demonstrated robust transduction capabilities after local delivery in various tissues such as liver, retina, or cochlea, compared with conventional AAVs. Here, we compared the transduction efficacy of Anc80L65 with conventional AAV9 in the CNS after intravenous, intracerebroventricular (i.c.v.), or intraparenchymal injections. Anc80L65 was more potent at targeting the brain and spinal cord after intravenous injection than AAV9, and mostly transduced astrocytes and a wide range of neuronal subpopulations. Although the efficacy of Anc80L65 and AAV9 is similar after direct intraparenchymal injection in the striatum, Anc80L65's diffusion throughout the CNS was more extensive than AAV9 after i.c.v. infusion, leading to widespread EGFP expression in the cerebellum. These findings demonstrate that Anc80L65 is a highly efficient gene transfer vector for the murine CNS. Systemic injection of Anc80L65 leads to notable expression in the CNS that does not rely on a self-complementary genome. These data warrant further testing in larger animal models.

Somatic Editing of Ldlr With Adeno-Associated Viral-CRISPR Is an Efficient Tool for Atherosclerosis Research

Objective- Atherosclerosis studies in Ldlr knockout mice require breeding to homozygosity and congenic status on C57BL6/J background, a process that is both time and resource intensive. We aimed to develop a new method for generating atherosclerosis through somatic deletion of Ldlr in livers of adult mice. Approach and Results- Overexpression of PCSK9 (proprotein convertase subtilisin/kexin type 9) is currently used to study atherosclerosis, which promotes degradation of LDLR (low-density lipoprotein receptor) in the liver. We sought to determine whether CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats-associated 9) could also be used to generate atherosclerosis through genetic disruption of Ldlr in adult mice. We engineered adeno-associated viral (AAV) vectors expressing Staphylococcus aureus Cas9 and a guide RNA targeting the Ldlr gene (AAV-CRISPR). Both male and female mice received either (1) saline, (2) AAV-CRISPR, or (3) AAV-hPCSK9 (human PCSK9)-D374Y. A fourth group of germline Ldlr-KO mice was included for comparison. Mice were placed on a Western diet and followed for 20 weeks to assess plasma lipids, PCSK9 protein levels, atherosclerosis, and editing efficiency. Disruption of Ldlr with AAV-CRISPR was robust, resulting in severe hypercholesterolemia and atherosclerotic lesions in the aorta. AAV-hPCSK9 also produced hypercholesterolemia and atherosclerosis as expected. Notable sexual dimorphism was observed, wherein AAV-CRISPR was superior for Ldlr removal in male mice, while AAV-hPCSK9 was more effective in female mice. Conclusions- This all-in-one AAV-CRISPR vector targeting Ldlr is an effective and versatile tool to model atherosclerosis with a single injection and provides a useful alternative to the use of germline Ldlr-KO mice.

Novel Approaches for the Treatment of Familial Hypercholesterolemia: Current Status and Future Challenges

Familial hypercholesterolemia (FH) is an autosomal-dominant disorder that is characterized by high plasma lowdensity lipoprotein cholesterol (LDL-c) levels and an increased risk of cardiovascular disease. Despite the use of high-dose statins and the recent addition of proprotein convertase subtilisin/kexin type 9 inhibitors as a treatment option, many patients with homozygous FH fail to achieve optimal reductions of LDL-c levels. Gene therapy has become one of the most promising research directions for contemporary life sciences and is a potential treatment option for FH. Recent studies have confirmed the efficacy of a recombinant adeno-associated virus 8 vector expressing the human LDL-c receptor gene in a mouse model, and this vector is currently in phase 2 clinical trials. Much progress has also been achieved in the fields of antisense oligonucleotide- and small interfering RNA-based gene therapies, which are in phase 1–2 clinical trials. In addition, novel approaches, such as the use of minicircle DNA vectors, microRNAs, long non-coding RNAs, and the CRISPR/Cas9 gene-editing system, have shown great potential for FH therapy. However, the delivery system, immunogenicity, accuracy, and specificity of gene therapies limit their clinical applications. In this article, we discuss the current status of gene therapy and recent advances that will likely affect the clinical application of gene therapy for the treatment of FH.

Novel lipid modifying drugs to lower LDL cholesterol

PURPOSE OF REVIEW

Statins have long been the cornerstone for the prevention of cardiovascular disease (CVD). However, because of perceived adverse effects and insufficient efficacy in certain groups of patients, considerable interest exists in the search for alternatives to lower LDL-cholesterol (LDL-C), and the recent approvals of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors underlines the success of this quest. Here, we give an updated overview on the most recent developments in the area of LDL-C lowering agents.

RECENT FINDINGS

The clinical effects of the PCSK9 inhibitors are promising, especially now that the FOURIER and SPIRE programmes are published. Most cholesterylester-transfer protein inhibitors, however, except anacetrapib, have been discontinued because of either toxicity or lack of efficacy in large cardiovascular outcome trials. Other agents - like mipomersen, lomitapide, ETC-1002, and gemcabene - aim to lower LDL-C in different ways than solely through the LDL receptor, opening up possibilities for treating patients not responding to conventional therapies. New discoveries are also being made at the DNA and RNA level, with mipomersen being the first approved therapy based on RNA intervention in the United States for homozygous familial hypercholesterolemia.

SUMMARY

Recent years have witnessed a new beginning for cholesterol-lowering compounds. With increased knowledge of lipid metabolism a score of new therapeutic targets has been identified. Mechanisms for modulation of those targets are also becoming more diverse while statins remain the backbone of CVD prevention, the new alternatives, such as PCSK9 monoclonals will probably play an important additional role in treatment of patients at risk for CVD.

Long-term treatment with evolocumab added to conventional drug therapy, with or without apheresis, in patients with homozygous familial hypercholesterolaemia: an interim subset analysis of the open-label TAUSSIG study

BACKGROUND

Homozygous familial hypercholesterolaemia is a genetic disorder characterised by substantially raised LDL cholesterol, reduced LDL receptor function, xanthomas, and cardiovascular disease before age 20 years. Conventional therapy is with statins, ezetimibe, and apheresis. We aimed to assess the long-term safety and efficacy of the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor evolocumab in a subset of patients with homozygous familial hypercholesterolaemia enrolled in an open-label, non-randomised phase 3 trial.

METHODS

In this interim subset analysis of the TAUSSIG study, which was undertaken at 35 sites in 17 countries, we included patients aged 12 years or older with homozygous familial hypercholesterolaemia who were on stable LDL cholesterol-lowering therapy for at least 4 weeks; all patients received evolocumab 420 mg subcutaneously monthly, or if on apheresis every 2 weeks. Dosing could be increased to every 2 weeks after 12 weeks in patients not on apheresis. The primary outcome of the TAUSSIG study was treatment-emergent adverse events; secondary outcomes were the effects of evolocumab on LDL cholesterol and other lipids. We analysed patients on an intention-to-treat basis, and all statistical comparisons were done post hoc in this interim analysis. The TAUSSIG study is registered with ClinicalTrials.gov, number NCT01624142, and is ongoing.

FINDINGS

106 patients were included in this analysis, 34 receiving apheresis at study entry and 14 younger than 18 years. The first patient was enrolled on June 28, 2012, and the cutoff date for the analysis was Aug 13, 2015; mean follow-up was 1·7 years (SD 0·63). After 12 weeks, mean LDL cholesterol decreased from baseline by 20·6% (SD 24·4; mean absolute decrease 1·50 mmol/L [SD 1·92]); these reductions were maintained at week 48. 47 of 72 patients not on apheresis at study entry increased evolocumab dosing to every 2 weeks, with an additional mean reduction in LDL cholesterol of 8·3% (SD 13·0; mean absolute decrease 0·77 mmol/L [SD 1·38]; p=0·0001). In a post-hoc analysis, mean reductions in LDL cholesterol in patients on apheresis were significant at week 12 (p=0·0012) and week 48 (p=0·0032), and did not differ from reductions achieved in patients not on apheresis (p=0·38 at week 12 and p=0·09 at week 48). We noted a small reduction (median -7·7% [IQR -21·6 to 6·8]) in lipoprotein(a) at week 12 (p=0·0015), with some additional reduction at week 48 (-11·9% [-28·0 to 0·0]; p<0·0001). HDL cholesterol was increased by a mean of 7·6% (SD 18·1) at week 12 (p<0·0001) and 7·6% (SD 20·6) at week 48 (p=0·0007). Evolocumab was well tolerated; 82 (77%) patients reported treatment-emergent adverse events, which were mostly minor. The most common were nasopharyngitis (14 patients [13%]), influenza (13 [12%]), headache (11 [10%]), and upper respiratory tract infection (11 [10%]). Serious adverse events occurred in 18 (17%) patients, with the most common being cardiovascular events (four patients [4%]). There were no deaths and four positively adjudicated cardiovascular events, one (3%) among patients on apheresis and three (4%) among patients who did not receive apheresis.

INTERPRETATION

Our interim results suggest that evolocumab is an effective additional option to reduce LDL cholesterol in patients with homozygous familial hypercholesterolaemia, with or without apheresis.

FUNDING

Amgen.

AAV9-NPC1 significantly ameliorates Purkinje cell death and behavioral abnormalities in mouse NPC disease

Niemann-Pick type C (NPC) disease is a fatal inherited neurodegenerative disorder caused by loss-of-function mutations in the NPC1 or NPC2 gene. There is no effective way to treat NPC disease. In this study, we used adeno-associated virus (AAV) serotype 9 (AAV9) to deliver a functional NPC1 gene systemically into NPC1-/- mice at postnatal day 4. One single AAV9-NPC1 injection resulted in robust NPC1 expression in various tissues, including brain, heart, and lung. Strikingly, AAV9-mediated NPC1 delivery significantly promoted Purkinje cell survival, restored locomotor activity and coordination, and increased the lifespan of NPC1-/- mice. Our work suggests that AAV-based gene therapy is a promising means to treat NPC disease.

Low-density lipoprotein receptor-negative compound heterozygous familial hypercholesterolemia: Two lifetime journeys of lipid-lowering therapy

We present the case history of 2 patients with low-density lipoprotein receptor-negative compound heterozygous familial hypercholesterolemia who did not receive lipoprotein apheresis. We describe the subsequent effect of all lipid-lowering medications during their life course including resins, statins, ezetimibe, nicotinic acid/laropiprant, mipomersen, and lomitapide. These cases tell the story of siblings affected with this rare disease, who are free of symptoms but still are at a very high cardiovascular disease risk, and their treatment from childhood.