In vivo adenine base editing of PCSK9 in macaques reduces LDL cholesterol levels

mRNA-based therapeutics: looking beyond COVID-19 vaccines

Recent advances in mRNA technology and its delivery have enabled mRNA-based therapeutics to enter a new era in medicine. The rapid, potent, and transient nature of mRNA-encoded proteins, without the need to enter the nucleus or the risk of genomic integration, makes them desirable tools for treatment of a range of diseases, from infectious diseases to cancer and monogenic disorders. The rapid pace and ease of mass-scale manufacturability of mRNA-based therapeutics supported the global response to the COVID-19 pandemic. Nonetheless, challenges remain with regards to mRNA stability, duration of expression, delivery efficiency, and targetability, to broaden the applicability of mRNA therapeutics beyond COVID-19 vaccines. By learning from the rapidly expanding preclinical and clinical studies, we can optimise the mRNA platform to meet the clinical needs of each disease. Here, we will summarise the recent advances in mRNA technology; its use in vaccines, immunotherapeutics, protein replacement therapy, and genomic editing; and its delivery to desired specific cell types and organs for development of a new generation of targeted mRNA-based therapeutics.

Branched chemically modified poly(A) tails enhance the translation capacity of mRNA

Although messenger RNA (mRNA) has proved effective as a vaccine, its potential as a general therapeutic modality is limited by its instability and low translation capacity. To increase the duration and level of protein expression from mRNA, we designed and synthesized topologically and chemically modified mRNAs with multiple synthetic poly(A) tails. Here we demonstrate that the optimized multitailed mRNA yielded ~4.7-19.5-fold higher luminescence signals than the control mRNA from 24 to 72 h post transfection in cellulo and 14 days detectable signal versus <7 days signal from the control in vivo. We further achieve efficient multiplexed genome editing of the clinically relevant genes Pcsk9 and Angptl3 in mouse liver at a minimal mRNA dosage. Taken together, these results provide a generalizable approach to synthesize capped branched mRNA with markedly enhanced translation capacity.

Targeted nonviral delivery of genome editors in vivo

Cell-type-specific in vivo delivery of genome editing molecules is the next breakthrough that will drive biological discovery and transform the field of cell and gene therapy. Here, we discuss recent advances in the delivery of CRISPR-Cas genome editors either as preassembled ribonucleoproteins or encoded in mRNA. Both strategies avoid pitfalls of viral vector-mediated delivery and offer advantages including transient editor lifetime and potentially streamlined manufacturing capability that are already proving valuable for clinical use. We review current applications and future opportunities of these emerging delivery approaches that could make genome editing more efficacious and accessible in the future.

Breaking genetic shackles: The advance of base editing in genetic disorder treatment

The rapid evolution of gene editing technology has markedly improved the outlook for treating genetic diseases. Base editing, recognized as an exceptionally precise genetic modification tool, is emerging as a focus in the realm of genetic disease therapy. We provide a comprehensive overview of the fundamental principles and delivery methods of cytosine base editors (CBE), adenine base editors (ABE), and RNA base editors, with a particular focus on their applications and recent research advances in the treatment of genetic diseases. We have also explored the potential challenges faced by base editing technology in treatment, including aspects such as targeting specificity, safety, and efficacy, and have enumerated a series of possible solutions to propel the clinical translation of base editing technology. In conclusion, this article not only underscores the present state of base editing technology but also envisions its tremendous potential in the future, providing a novel perspective on the treatment of genetic diseases. It underscores the vast potential of base editing technology in the realm of genetic medicine, providing support for the progression of gene medicine and the development of innovative approaches to genetic disease therapy.

In vivo base editing rescues primary hyperoxaluria type 1 in rats

Primary hyperoxaluria type 1 (PH1) is a childhood-onset autosomal recessive disease, characterized by nephrocalcinosis, multiple recurrent urinary calcium oxalate stones, and a high risk of progressive kidney damage. PH1 is caused by inherent genetic defects of the alanine glyoxylate aminotransferase (AGXT) gene. The in vivo repair of disease-causing genes was exceedingly inefficient before the invention of base editors which can efficiently introduce precisely targeted base alterations without double-strand DNA breaks. Adenine base editor (ABE) can precisely convert A·T to G·C with the assistance of specific guide RNA. Here, we demonstrated that systemic delivery of dual adeno-associated virus encoding a split-ABE8e could artificially repair 13% of the pathogenic allele in AgxtQ84X rats, a model of PH1, alleviating the disease phenotype. Specifically, ABE treatment partially restored the expression of alanine-glyoxylate-aminotransferase (AGT), reduced endogenous oxalate synthesis and alleviated calcium oxalate crystal deposition. Western blot and immunohistochemistry confirmed that ABE8e treatment restored AGT protein expression in hepatocytes. Moreover, the precise editing efficiency in the liver remained stable six months after treatment. Thus, our findings provided a prospect of in vivo base editing as a personalized and precise medicine for PH1 by directly correcting the mutant Agxt gene.

Generation of precision preclinical cancer models using regulated in vivo base editing

Although single-nucleotide variants (SNVs) make up the majority of cancer-associated genetic changes and have been comprehensively catalogued, little is known about their impact on tumor initiation and progression. To enable the functional interrogation of cancer-associated SNVs, we developed a mouse system for temporal and regulatable in vivo base editing. The inducible base editing (iBE) mouse carries a single expression-optimized cytosine base editor transgene under the control of a tetracycline response element and enables robust, doxycycline-dependent expression across a broad range of tissues in vivo. Combined with plasmid-based or synthetic guide RNAs, iBE drives efficient engineering of individual or multiple SNVs in intestinal, lung and pancreatic organoids. Temporal regulation of base editor activity allows controlled sequential genome editing ex vivo and in vivo, and delivery of sgRNAs directly to target tissues facilitates generation of in situ preclinical cancer models.

Continuous directed evolution of a compact CjCas9 variant with broad PAM compatibility

CRISPR-Cas9 genome engineering is a powerful technology for correcting genetic diseases. However, the targeting range of Cas9 proteins is limited by their requirement for a protospacer adjacent motif (PAM), and in vivo delivery is challenging due to their large size. Here, we use phage-assisted continuous directed evolution to broaden the PAM compatibility of Campylobacter jejuni Cas9 (CjCas9), the smallest Cas9 ortholog characterized to date. The identified variant, termed evoCjCas9, primarily recognizes N4AH and N5HA PAM sequences, which occur tenfold more frequently in the genome than the canonical N3VRYAC PAM site. Moreover, evoCjCas9 exhibits higher nuclease activity than wild-type CjCas9 on canonical PAMs, with editing rates comparable to commonly used PAM-relaxed SpCas9 variants. Combined with deaminases or reverse transcriptases, evoCjCas9 enables robust base and prime editing, with the small size of evoCjCas9 base editors allowing for tissue-specific installation of A-to-G or C-to-T transition mutations from single adeno-associated virus vector systems.

Past, present, and future of CRISPR genome editing technologies

Genome editing has been a transformative force in the life sciences and human medicine, offering unprecedented opportunities to dissect complex biological processes and treat the underlying causes of many genetic diseases. CRISPR-based technologies, with their remarkable efficiency and easy programmability, stand at the forefront of this revolution. In this Review, we discuss the current state of CRISPR gene editing technologies in both research and therapy, highlighting limitations that constrain them and the technological innovations that have been developed in recent years to address them. Additionally, we examine and summarize the current landscape of gene editing applications in the context of human health and therapeutics. Finally, we outline potential future developments that could shape gene editing technologies and their applications in the coming years.

Recent Research Trends in Stem Cells Using CRISPR/Cas-Based Genome Editing Methods

The clustered regularly interspaced short palindromic repeats (CRISPR) system, a rapidly advancing genome editing technology, allows DNA alterations into the genome of organisms. Gene editing using the CRISPR system enables more precise and diverse editing, such as single nucleotide conversion, precise knock-in of target sequences or genes, chromosomal rearrangement, or gene disruption by simple cutting. Moreover, CRISPR systems comprising transcriptional activators/repressors can be used for epigenetic regulation without DNA damage. Stem cell DNA engineering based on gene editing tools has enormous potential to provide clues regarding the pathogenesis of diseases and to study the mechanisms and treatments of incurable diseases. Here, we review the latest trends in stem cell research using various CRISPR/Cas technologies and discuss their future prospects in treating various diseases.

Precise genome-editing in human diseases: mechanisms, strategies and applications

Precise genome-editing platforms are versatile tools for generating specific, site-directed DNA insertions, deletions, and substitutions. The continuous enhancement of these tools has led to a revolution in the life sciences, which promises to deliver novel therapies for genetic disease. Precise genome-editing can be traced back to the 1950s with the discovery of DNA's double-helix and, after 70 years of development, has evolved from crude in vitro applications to a wide range of sophisticated capabilities, including in vivo applications. Nonetheless, precise genome-editing faces constraints such as modest efficiency, delivery challenges, and off-target effects. In this review, we explore precise genome-editing, with a focus on introduction of the landmark events in its history, various platforms, delivery systems, and applications. First, we discuss the landmark events in the history of precise genome-editing. Second, we describe the current state of precise genome-editing strategies and explain how these techniques offer unprecedented precision and versatility for modifying the human genome. Third, we introduce the current delivery systems used to deploy precise genome-editing components through DNA, RNA, and RNPs. Finally, we summarize the current applications of precise genome-editing in labeling endogenous genes, screening genetic variants, molecular recording, generating disease models, and gene therapy, including ex vivo therapy and in vivo therapy, and discuss potential future advances.

The Italian breakthrough in CRISPR trials for rare diseases: a focus on beta-thalassemia and sickle cell disease treatment

The development of gene therapy and the current advantageous method of clustered regularly interspaced short palindromic repeats (CRISPRs) has allowed the implementation of several clinical trials aimed at studying the possible efficacy of gene therapy for rare diseases. Rare diseases pose a global challenge, in that their collective impact on health systems is considerable, whereas their individually rare occurrence hinders research and development of efficient therapies. Despite the low prevalence of individual rare diseases, there are more than 7,000 defined rare diseases affecting 3.5–5.9% of the global population. Rare diseases are mostly chronic and approximately 80% are caused by genetic mutation with an early-life onset. In Italy, in 2021 were recorded more than 400,000 people with rare disease. Because of its location and history, Italy has an unfortunate statistic regarding the presence and prevalence of two rare genetic diseases, namely beta-thalassemia, of which there are about 90 million carriers worldwide, 400,000 of whom are actually affected, and sickle cell disease, with about 300 million carriers and 6.5 million people affected worldwide. Advancements in genomic studies allowed Italy to join clinical trials to study effective and resolving gene therapies for BT and SCD. This study reports on the impact of rare diseases in Italy, ongoing studies, and recent achievements in BT and SCD trials using the CRISPR method and remaining hurdles in the application of CRISPR technology to rare diseases, also taking a glimpse at the newest challenges and future opportunities in the genetic treatment for rare diseases.

Quantifying nanoparticle delivery: challenges, tools, and advances

This review explores challenges and methods for quantifying nanoparticle delivery in therapeutic applications. We discuss three main approaches: (1) functional readouts that assess therapeutic effects post nanoparticle administration, (2) nanocarrier tracking that directly monitors the nanoparticle localization, and (3) cargo tracking that infers nanoparticle localization by measuring encapsulated agents or attached surface tags. Reanalysis of the Wilhelm et al. Cancer Nanomedicine Repository dataset found mixed quantification methodologies, which could cause misleading conclusions. We discuss potential pitfalls in each quantification approach and highlight recent advancements in novel technologies. It is important that researchers select appropriate quantification methods based on their objectives and consider integrating multiple approaches for a comprehensive understanding of in vivo nanoparticle behavior to facilitate their clinical translation.

Gene therapy for monogenic disorders: challenges, strategies, and perspectives

Monogenic disorders refer to a group of human diseases caused by mutations in single genes. While disease-modifying therapies have offered some relief from symptoms and delayed progression for some monogenic diseases, most of these diseases still lack effective treatments. In recent decades, gene therapy has emerged as a promising therapeutic strategy for genetic disorders. Researchers have developed various gene manipulation tools and gene delivery systems to treat monogenic diseases. Despite this progress, concerns about inefficient delivery, persistent expression, immunogenicity, toxicity, capacity limitation, genomic integration, and limited tissue specificity still need to be addressed. This review gives an overview of commonly used gene therapy and delivery tools, along with the challenges they face and potential strategies to counter them.

Progress and Pitfalls of Chimeric Antigen Receptor T Cell Immunotherapy against T Cell Malignancies

Chimeric antigen receptor T cell (CAR-T) immunotherapy has revolutionized the treatment of relapsed and refractory B cell-derived hematologic malignancies. Currently, there are 6 Food and Drug Administration-approved commercial CAR-T products that target antigens exclusively expressed on malignant B cells or plasma cells. However, concurrent advancement for patients with rarer and more aggressive T cell-derived hematologic malignancies have not yet been achieved. CAR-T immunotherapies are uniquely limited by challenges related to CAR-T product manufacturing and intrinsic tumor biology. In this review tailored for practicing clinician-scientists, we discuss the major barriers of CAR-T implementation against T cell-derived neoplasms and highlight specific scientific advancements poised to circumvent these obstacles. We summarize salient early-stage clinical trials implementing novel CAR-T immunotherapies specifically for patients with relapsed and/or refractory T cell neoplasms. Finally, we highlight novel manufacturing and treatment strategies that are poised to have a meaningful future clinical impact.

Ultrasound-nanovesicles interplay for theranostics

Nanovesicles (NVs) are widely used in the treatment and diagnosis of diseases due to their excellent vascular permeability, good biocompatibility, high loading capacity, and easy functionalization. However, their yield and in vivo penetration depth limitations and their complex preparation processes still constrain their application and development. Ultrasound, as a fundamental external stimulus with deep tissue penetration, concentrated energy sources, and good safety, has been proven to be a patient-friendly and highly efficient strategy to overcome the restrictions of traditional clinical medicine. Recent research has shown that ultrasound can drive the generation of NVs, increase their yield, simplify their preparation process, and provide direct therapeutic effects and intelligent control to enhance the therapeutic effect of NVs. In addition, NVs, as excellent drug carriers, can enhance the targeting efficiency of ultrasound-based sonodynamic therapy or sonogenetic regulation and improve the accuracy of ultrasound imaging. This review provides a detailed introduction to the classification, generation, and modification strategies of NVs, emphasizing the impact of ultrasound on the formation of NVs and summarizing the enhanced treatment and diagnostic effects of NVs combined with ultrasound for various diseases.

Efficient prime editing in mouse brain, liver and heart with dual AAVs

Realizing the promise of prime editing for the study and treatment of genetic disorders requires efficient methods for delivering prime editors (PEs) in vivo. Here we describe the identification of bottlenecks limiting adeno-associated virus (AAV)-mediated prime editing in vivo and the development of AAV-PE vectors with increased PE expression, prime editing guide RNA stability and modulation of DNA repair. The resulting dual-AAV systems, v1em and v3em PE-AAV, enable therapeutically relevant prime editing in mouse brain (up to 42% efficiency in cortex), liver (up to 46%) and heart (up to 11%). We apply these systems to install putative protective mutations in vivo for Alzheimer's disease in astrocytes and for coronary artery disease in hepatocytes. In vivo prime editing with v3em PE-AAV caused no detectable off-target effects or significant changes in liver enzymes or histology. Optimized PE-AAV systems support the highest unenriched levels of in vivo prime editing reported to date, facilitating the study and potential treatment of diseases with a genetic component.

Self-delivering, chemically modified CRISPR RNAs for AAV co-delivery and genome editing in vivo

Guide RNAs offer programmability for CRISPR-Cas9 genome editing but also add challenges for delivery. Chemical modification, which has been key to the success of oligonucleotide therapeutics, can enhance the stability, distribution, cellular uptake, and safety of nucleic acids. Previously, we engineered heavily and fully modified SpyCas9 crRNA and tracrRNA, which showed enhanced stability and retained activity when delivered to cultured cells in the form of the ribonucleoprotein complex. In this study, we report that a short, fully stabilized oligonucleotide (a 'protecting oligo'), which can be displaced by tracrRNA annealing, can significantly enhance the potency and stability of a heavily modified crRNA. Furthermore, protecting oligos allow various bioconjugates to be appended, thereby improving cellular uptake and biodistribution of crRNA in vivo. Finally, we achieved in vivo genome editing in adult mouse liver and central nervous system via co-delivery of unformulated, chemically modified crRNAs with protecting oligos and AAV vectors that express tracrRNA and either SpyCas9 or a base editor derivative. Our proof-of-concept establishment of AAV/crRNA co-delivery offers a route towards transient editing activity, target multiplexing, guide redosing, and vector inactivation.

In Vivo Base Editing of Scn5a Rescues Type 3 Long QT Syndrome in Mice

BACKGROUND

Pathogenic variants in SCN5A can result in long QT syndrome type 3, a life-threatening genetic disease. Adenine base editors can convert targeted A T base pairs to G C base pairs, offering a promising tool to correct pathogenic variants.

METHODS

We generated a long QT syndrome type 3 mouse model by introducing the T1307M pathogenic variant into the Scn5a gene. The adenine base editor was split into 2 smaller parts and delivered into the heart by adeno-associated virus serotype 9 (AAV9-ABEmax) to correct the T1307M pathogenic variant.

RESULTS

Both homozygous and heterozygous T1307M mice showed significant QT prolongation. Carbachol administration induced Torsades de Pointes or ventricular tachycardia for homozygous T1307M mice (20%) but not for heterozygous or wild-type mice. A single intraperitoneal injection of AAV9-ABEmax at postnatal day 14 resulted in up to 99.20% Scn5a transcripts corrected in T1307M mice. Scn5a mRNA correction rate >60% eliminated QT prolongation; Scn5a mRNA correction rate <60% alleviated QT prolongation. Partial Scn5a correction resulted in cardiomyocytes heterogeneity, which did not induce severe arrhythmias. We did not detect off-target DNA or RNA editing events in ABEmax-treated mouse hearts.

CONCLUSIONS

These findings show that in vivo AAV9-ABEmax editing can correct the variant Scn5a allele, effectively ameliorating arrhythmia phenotypes. Our results offer a proof of concept for the treatment of hereditary arrhythmias.

Secreted Particle Information Transfer (SPIT) - A Cellular Platform for In Vivo Genetic Engineering

A multitude of tools now exist that allow us to precisely manipulate the human genome in a myriad of different ways. However, successful delivery of these tools to the cells of human patients remains a major barrier to their clinical implementation. Here we introduce a new cellular approach for in vivo genetic engineering, Secreted Particle Information Transfer (SPIT) that utilizes human cells as delivery vectors for in vivo genetic engineering. We demonstrate the application of SPIT for cell-cell delivery of Cre recombinase and CRISPR-Cas9 enzymes, we show that genetic logic can be incorporated into SPIT and present the first demonstration of human cells as a delivery platform for in vivo genetic engineering in immunocompetent mice. We successfully applied SPIT to genetically modify multiple organs and tissue stem cells in vivo including the liver, spleen, intestines, peripheral blood, and bone marrow. We anticipate that by harnessing the large packaging capacity of a human cell's nucleus, the ability of human cells to engraft into patients' long term and the capacity of human cells for complex genetic programming, that SPIT will become a paradigm shifting approach for in vivo genetic engineering.

Targeting proprotein convertase subtilisin/kexin type 9 (PCSK9): from bench to bedside

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has evolved as a pivotal enzyme in lipid metabolism and a revolutionary therapeutic target for hypercholesterolemia and its related cardiovascular diseases (CVD). This comprehensive review delineates the intricate roles and wide-ranging implications of PCSK9, extending beyond CVD to emphasize its significance in diverse physiological and pathological states, including liver diseases, infectious diseases, autoimmune disorders, and notably, cancer. Our exploration offers insights into the interaction between PCSK9 and low-density lipoprotein receptors (LDLRs), elucidating its substantial impact on cholesterol homeostasis and cardiovascular health. It also details the evolution of PCSK9-targeted therapies, translating foundational bench discoveries into bedside applications for optimized patient care. The advent and clinical approval of innovative PCSK9 inhibitory therapies (PCSK9-iTs), including three monoclonal antibodies (Evolocumab, Alirocumab, and Tafolecimab) and one small interfering RNA (siRNA, Inclisiran), have marked a significant breakthrough in cardiovascular medicine. These therapies have demonstrated unparalleled efficacy in mitigating hypercholesterolemia, reducing cardiovascular risks, and have showcased profound value in clinical applications, offering novel therapeutic avenues and a promising future in personalized medicine for cardiovascular disorders. Furthermore, emerging research, inclusive of our findings, unveils PCSK9's potential role as a pivotal indicator for cancer prognosis and its prospective application as a transformative target for cancer treatment. This review also highlights PCSK9's aberrant expression in various cancer forms, its association with cancer prognosis, and its crucial roles in carcinogenesis and cancer immunity. In conclusion, this synthesized review integrates existing knowledge and novel insights on PCSK9, providing a holistic perspective on its transformative impact in reshaping therapeutic paradigms across various disorders. It emphasizes the clinical value and effect of PCSK9-iT, underscoring its potential in advancing the landscape of biomedical research and its capabilities in heralding new eras in personalized medicine.

Recent Advances in Double-Strand Break-Free Kilobase-Scale Genome Editing Technologies

Genome editing approaches have transformed the ability to make user-defined changes to genomes in both ex vivo and in vivo contexts. Despite the abundant development of technologies that permit the installation of nucleotide-level changes, until recently, larger-scale sequence edits via technologies independent of DNA double-strand breaks (DSBs) had remained less explored. Here, we review recent advances toward DSB-free technologies that enable kilobase-scale modifications including insertions, deletions, inversions, replacements, and others. These technologies provide new capabilities for users, while offering hope for the simplification of putative therapeutic strategies by moving away from small mutation-specific edits and toward more generalizable kilobase-scale approaches.

Phosphonoacetate Modifications Enhance the Stability and Editing Yields of Guide RNAs for Cas9 Editors

CRISPR gene editing and control systems continue to emerge and inspire novel research and clinical applications. Advances in CRISPR performance such as optimizing the duration of activity in cells, tissues, and organisms, as well as limiting off-target activities, have been extremely important for expanding the utility of CRISPR-based systems. By investigating the effects of various chemical modifications in guide RNAs (gRNAs) at defined positions and combinations, we find that 2'-O-methyl-3'-phosphonoacetate (MP) modifications can be substantially more effective than 2'-O-methyl-3'-phosphorothioate (MS) modifications at the 3' ends of single-guide RNAs (sgRNAs) to promote high editing yields, in some instances showing an order of magnitude higher editing yield in human cells. MP-modified 3' ends are especially effective at promoting the activity of guide RNAs cotransfected with Cas messenger RNA (mRNA), as the gRNA must persist in cells until the Cas protein is expressed. We demonstrate such an MP enhancement for sgRNAs cotransfected with a BE4 mRNA for cytidine base editing and also demonstrate that MP at the 3' ends of prime editing guide RNAs (pegRNAs) cotransfected with PE2 mRNA can promote maximal prime editing yields. In the presence of serum, sgRNAs with MP-modified 3' ends showed marked improvements in editing efficiency over sgRNAs with MS-modified 3' ends codelivered with Cas9 mRNA and showed more modest improvements at enhancing the activity of transfected ribonucleoprotein (RNP) complexes. Our results suggest that MP should be considered as a performance-enhancing modification for the 3' ends of synthetic gRNAs, especially in situations where the guide RNAs may be susceptible to exonuclease-mediated degradation.

Large-scale manufacturing of base-edited chimeric antigen receptor T cells

Base editing is a revolutionary gene-editing technique enabling the introduction of point mutations into the genome without generating detrimental DNA double-stranded breaks. Base-editing enzymes are commonly delivered in the form of modified linear messenger RNA (mRNA) that is costly to produce. Here, we address this problem by developing a simple protocol for manufacturing base-edited cells using circular RNA (circRNA), which is less expensive to synthesize. Compared with linear mRNA, higher editing efficiencies were achieved with circRNA, enabling an 8-fold reduction in the amount of RNA required. We used this protocol to manufacture a clinical dose (1 × 108 cells) of base-edited chimeric antigen receptor (CAR) T cells lacking expression of the inhibitory receptor, PD-1. Editing efficiencies of up to 86% were obtained using 0.25 μg circRNA/1 × 106 cells. Increased editing efficiencies with circRNA were attributed to more efficient translation. These results suggest that circRNA, which is less expensive to produce than linear mRNA, is a viable option for reducing the cost of manufacturing base-edited cells at scale.

New opportunities in the management and treatment of refractory hypercholesterolemia using in vivo CRISPR-mediated genome/base editing

AIMS

Refractory hypercholesterolemia (RH), caused primarily by the loss-of-function mutation of LDL receptor (LDLR) gene seen in HoFH and HeFH patients, remains a major risk factor for atherosclerotic cardiovascular disease (ASCVD). Statin and ezetimibe combination therapy lower circulating LDL by 30% in HoFH patients. PCSK9 mAB, being an LDLR-dependent therapy, is not effective in HoFH, but lowers LDL by 25% in HeFH patients. A maximum reduction of 50% was noted in HoFH patients treated with ANGPTL3 mAB, which was not enough to achieve therapeutic goal of LDL. Therefore, new approaches are warranted to offer hopes to individuals intolerant to higher dose statins and not able to achieve recommended LDL level.

DATA SYNTHESIS

New approaches to lower LDL include gene therapy and gene editing. AAV-based gene therapy has shown encouraging results in animal models. Using CRISPR/Cas9-mediated genome/base editing, gain of function and loss of function have been successfully done in animal models. Recent progress in the refinement of genome/base editing has overcome the issues of off-target mutagenesis with ∼1% mutagenesis in case of PCSK9 and almost no off-target mutagenesis in inactivating ANGPTL3 in animal models showing 50% reduction in cholesterol. Current approaches using CRISPR-Cas9 genome/base editing targeting LDLR-dependent and LDLR-independent pathways are underway.

CONCLUSIONS

The new information on gain of LDLR function and inactivation of ANGPTL3 together with developments in genome/base editing technology to overcome off-target insertion and deletion mutagenesis offer hope to refractory hypercholesterolemic individuals who are at a higher risk of developing ASCVD.

Precise base editing without unintended indels in human cells and mouse primary myoblasts

Base editors are powerful tools for making precise single-nucleotide changes in the genome. However, they can lead to unintended insertions and deletions at the target sites, which is a significant limitation for clinical applications. In this study, we aimed to eliminate unwanted indels at the target sites caused by various evolved base editors. Accordingly, we applied dead Cas9 instead of nickase Cas9 in the base editors to induce accurate substitutions without indels. Additionally, we tested the use of chromatin-modulating peptides in the base editors to improve nucleotide conversion efficiency. We found that using both dead Cas9 and chromatin-modulating peptides in base editing improved the nucleotide substitution efficiency without unintended indel mutations at the desired target sites in human cell lines and mouse primary myoblasts. Furthermore, the proposed scheme had fewer off-target effects than conventional base editors at the DNA level. These results indicate that the suggested approach is promising for the development of more accurate and safer base editing techniques for use in clinical applications.

New Biological Therapies for Low-Density Lipoprotein Cholesterol

Depressed low-density lipoprotein cholesterol concentration protects against atherosclerotic cardiovascular disease. Natural hypocholesterolemia states can have a monogenic etiology, caused by pathogenic loss of function variants in the PCSK9, ANGPTL3, MTTP, or APOB genes. In this focused review, we discuss development and clinical use of several new therapeutics that inhibit these gene products to target elevated levels of low-density lipoprotein cholesterol. In particular, inhibitors of proprotein convertase subtilisin kexin type 9 (PCSK9) have notably affected clinical practice, followed recently by inhibition of angiopoietin-like 3 (ANGPTL3). Currently used in the clinic are alirocumab and evolocumab, two anti-PCSK9 monoclonal antibodies, inclisiran, a small interfering RNA that prevents PCSK9 translation, evinacumab, an anti-ANGPTL3 monoclonal antibody, and lomitapide, a small-molecule inhibitor of microsomal triglyceride transfer protein. Additional therapies are in preclinical or clinical trial stages of development. These consist of other monoclonal antibodies, antisense oligonucleotides, small-molecule inhibitors, mimetic peptides, adnectins, vaccines, and gene-editing therapies. Vaccines and gene-editing therapies in particular hold great potential to confer active long-term attenuation or provide single-treatment life-long knock-down of PCSK9 or ANGPTL3 activity. Biologic therapies inspired by monogenic hypocholesterolemia states are becoming valuable tools to help protect against atherosclerotic cardiovascular disease.

Unlocking the potential of RNA-based therapeutics in the lung: current status and future directions

Awareness of RNA-based therapies has increased after the widespread adoption of mRNA vaccines against SARS-CoV-2 during the COVID-19 pandemic. These mRNA vaccines had a significant impact on reducing lung disease and mortality. They highlighted the potential for rapid development of RNA-based therapies and advances in nanoparticle delivery systems. Along with the rapid advancement in RNA biology, including the description of noncoding RNAs as major products of the genome, this success presents an opportunity to highlight the potential of RNA as a therapeutic modality. Here, we review the expanding compendium of RNA-based therapies, their mechanisms of action and examples of application in the lung. The airways provide a convenient conduit for drug delivery to the lungs with decreased systemic exposure. This review will also describe other delivery methods, including local delivery to the pleura and delivery vehicles that can target the lung after systemic administration, each providing access options that are advantageous for a specific application. We present clinical trials of RNA-based therapy in lung disease and potential areas for future directions. This review aims to provide an overview that will bring together researchers and clinicians to advance this burgeoning field.

Lung and liver editing by lipid nanoparticle delivery of a stable CRISPR-Cas9 RNP

Lipid nanoparticle (LNP) delivery of CRISPR ribonucleoproteins (RNPs) has the potential to enable high-efficiency in vivo genome editing with low toxicity and an easily manufactured technology, if RNP efficacy can be maintained during LNP production. In this study, we engineered a thermostable Cas9 from Geobacillus stearothermophilus (GeoCas9) using directed evolution to generate iGeoCas9 evolved variants capable of robust genome editing of cells and organs. iGeoCas9s were significantly better at editing cells than wild-type GeoCas9, with genome editing levels >100X greater than those induced by the native GeoCas9 enzyme. Furthermore, iGeoCas9 RNP:LNP complexes edited a variety of cell lines and induced homology-directed repair (HDR) in cells receiving co-delivered single-stranded DNA (ssDNA) templates. Using tissue-selective LNP formulations, we observed genome editing of 35‒56% efficiency in the liver or lungs of mice that received intravenous injections of iGeoCas9 RNP:LNPs. In particular, iGeoCas9 complexed to acid-degradable LNPs edited lung tissue in vivo with an average of 35% efficiency, a significant improvement over editing efficiencies observed previously using viral or non-viral delivery strategies. These results show that thermostable Cas9 RNP:LNP complexes are a powerful alternative to mRNA:LNP delivery vehicles, expanding the therapeutic potential of genome editing.

Lipid Nanoparticle-Mediated Hit-and-Run Approaches Yield Efficient and Safe In Situ Gene Editing in Human Skin

Despite exciting advances in gene editing, the efficient delivery of genetic tools to extrahepatic tissues remains challenging. This holds particularly true for the skin, which poses a highly restrictive delivery barrier. In this study, we ran a head-to-head comparison between Cas9 mRNA or ribonucleoprotein (RNP)-loaded lipid nanoparticles (LNPs) to deliver gene editing tools into epidermal layers of human skin, aiming for in situ gene editing. We observed distinct LNP composition and cell-specific effects such as an extended presence of RNP in slow-cycling epithelial cells for up to 72 h. While obtaining similar gene editing rates using Cas9 RNP and mRNA with MC3-based LNPs (10-16%), mRNA-loaded LNPs proved to be more cytotoxic. Interestingly, ionizable lipids with a pKa ∼ 7.1 yielded superior gene editing rates (55%-72%) in two-dimensional (2D) epithelial cells while no single guide RNA-dependent off-target effects were detectable. Unexpectedly, these high 2D editing efficacies did not translate to actual skin tissue where overall gene editing rates between 5%-12% were achieved after a single application and irrespective of the LNP composition. Finally, we successfully base-corrected a disease-causing mutation with an efficacy of ∼5% in autosomal recessive congenital ichthyosis patient cells, showcasing the potential of this strategy for the treatment of monogenic skin diseases. Taken together, this study demonstrates the feasibility of an in situ correction of disease-causing mutations in the skin that could provide effective treatment and potentially even a cure for rare, monogenic, and common skin diseases.

Engineering of cytosine base editors with DNA damage minimization and editing scope diversification

Cytosine base editors (CBEs), which enable precise C-to-T substitutions, have been restricted by potential safety risks, including DNA off-target edits, RNA off-target edits and additional genotoxicity such as DNA damages induced by double-strand breaks (DSBs). Though DNA and RNA off-target edits have been ameliorated via various strategies, evaluation and minimization of DSB-associated DNA damage risks for most CBEs remain to be resolved. Here we demonstrate that YE1, an engineered CBE variant with minimized DNA and RNA off-target edits, could induce prominent DSB-associated DNA damage risks, manifested as γH2AX accumulation in human cells. We then perform deaminase engineering for two deaminases lamprey LjCDA1 and human APOBEC3A, and generate divergent CBE variants with eliminated DSB-associated DNA damage risks, in addition to minimized DNA/RNA off-target edits. Furthermore, the editing scopes and sequence preferences of APOBEC3A-derived CBEs could be further diversified by internal fusion strategy. Taken together, this study provides updated evaluation platform for DSB-associated DNA damage risks of CBEs and further generates a series of safer toolkits with diversified editing signatures to expand their applications.

Drug delivery systems for CRISPR-based genome editors

CRISPR-based drugs can theoretically manipulate any genetic target. In practice, however, these drugs must enter the desired cell without eliciting an unwanted immune response, so a delivery system is often required. Here, we review drug delivery systems for CRISPR-based genome editors, focusing on adeno-associated viruses and lipid nanoparticles. After describing how these systems are engineered and their subsequent characterization in preclinical animal models, we highlight data from recent clinical trials. Preclinical targeting mediated by polymers, proteins, including virus-like particles, and other vehicles that may deliver CRISPR systems in the future is also discussed.

Development of New Genome Editing Tools for the Treatment of Hyperlipidemia

Hyperlipidemia is a medical condition characterized by high levels of lipids in the blood. It is often associated with an increased risk of cardiovascular diseases such as heart attacks and strokes. Traditional treatment approaches for hyperlipidemia involve lifestyle modifications, dietary changes, and the use of medications like statins. Recent advancements in genome editing technologies, including CRISPR-Cas9, have opened up new possibilities for the treatment of this condition. This review provides a general overview of the main target genes involved in lipid metabolism and highlights the progress made during recent years towards the development of new treatments for dyslipidemia.

Applications of CRISPR-Cas9 for advancing precision medicine in oncology: from target discovery to disease modeling

The clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) (CRISPR/Cas9) system is a powerful tool that enables precise and efficient gene manipulation. In a relatively short time, CRISPR has risen to become the preferred gene-editing system due to its high efficiency, simplicity, and programmability at low costs. Furthermore, in the recent years, the CRISPR toolkit has been rapidly expanding, and the emerging advancements have shown tremendous potential in uncovering molecular mechanisms and new therapeutic strategies for human diseases. In this review, we provide our perspectives on the recent advancements in CRISPR technology and its impact on precision medicine, ranging from target identification, disease modeling, and diagnostics. We also discuss the impact of novel approaches such as epigenome, base, and prime editing on preclinical cancer drug discovery.

RNA-Based Therapeutic Technology

RNA-based therapy has been an expanding area of clinical research since the COVID-19 outbreak. Often, its comparison has been made to DNA-based gene therapy, such as adeno-associated virus- and lentivirus-mediated therapy. These DNA-based therapies show persistent expression, with maximized therapeutic efficacy. However, accumulating data indicate that proper control of gene expression is occasionally required. For example, in cancer immunotherapy, cytokine response syndrome is detrimental for host animals, while excess activation of the immune system induces supraphysiological cytokines. RNA-based therapy seems to be a rather mild therapy, and it has room to fit unmet medical needs, whereas current DNA-based therapy has unclear issues. This review focused on RNA-based therapy for cancer immunotherapy, hematopoietic disorders, and inherited disorders, which have received attention for possible clinical applications.

mRNA-based vaccines and therapeutics: an in-depth survey of current and upcoming clinical applications

mRNA-based drugs have tremendous potential as clinical treatments, however, a major challenge in realizing this drug class will promise to develop methods for safely delivering the bioactive agents with high efficiency and without activating the immune system. With regard to mRNA vaccines, researchers have modified the mRNA structure to enhance its stability and promote systemic tolerance of antigenic presentation in non-inflammatory contexts. Still, delivery of naked modified mRNAs is inefficient and results in low levels of antigen protein production. As such, lipid nanoparticles have been utilized to improve delivery and protect the mRNA cargo from extracellular degradation. This advance was a major milestone in the development of mRNA vaccines and dispelled skepticism about the potential of this technology to yield clinically approved medicines. Following the resounding success of mRNA vaccines for COVID-19, many other mRNA-based drugs have been proposed for the treatment of a variety of diseases. This review begins with a discussion of mRNA modifications and delivery vehicles, as well as the factors that influence administration routes. Then, we summarize the potential applications of mRNA-based drugs and discuss further key points pertaining to preclinical and clinical development of mRNA drugs targeting a wide range of diseases. Finally, we discuss the latest market trends and future applications of mRNA-based drugs.

Differences and Similarities of the Intravenously Administered Lipid Nanoparticles in Three Clinical Trials: Potential Linkage between Lipid Nanoparticles and Extracellular Vesicles

Lipid nanoparticles (LNPs) are clinically validated drug-delivery carriers. However, clinical data on intravenously administered LNPs are limited compared with those on intramuscularly administered LNPs (mRNA vaccines against COVID-19). Here, we reviewed three clinically tested intravenously administered LNPs (patisiran, mRNA-1944, and NTLA-2001). We summarize the differences and similarities in their formulations, mechanisms of action, and pharmacokinetics profiles. In humans, patisiran and mRNA-1944 exhibited similar multiphasic pharmacokinetic profiles with a secondary peak in the RNA concentration. siRNA (patisiran) and mRNA (mRNA-1944) exhibited prolonged blood circulation and were detectable for more than 28 days after a single administration. We further summarize the basics of extracellular vesicles (EVs) and discuss the potential linkages between LNPs and EVs. This Review provides an understanding of the human clinical data of intravenous LNP formulations, which can be potentially explored to develop next-generation LNP-and EV-based drug delivery carriers.

Applications of Genome Editing Technologies in CAD Research and Therapy with a Focus on Atherosclerosis

Cardiovascular diseases, particularly coronary artery disease (CAD), remain the leading cause of death worldwide in recent years, with myocardial infarction (MI) being the most common form of CAD. Atherosclerosis has been highlighted as one of the drivers of CAD, and much research has been carried out to understand and treat this disease. However, there remains much to be better understood and developed in treating this disease. Genome editing technologies have been widely used to establish models of disease as well as to treat various genetic disorders at their root. In this review, we aim to highlight the various ways genome editing technologies can be applied to establish models of atherosclerosis, as well as their therapeutic roles in both atherosclerosis and the clinical implications of CAD.

A split and inducible adenine base editor for precise in vivo base editing

DNA base editors use deaminases fused to a programmable DNA-binding protein for targeted nucleotide conversion. However, the most widely used TadA deaminases lack post-translational control in living cells. Here, we present a split adenine base editor (sABE) that utilizes chemically induced dimerization (CID) to control the catalytic activity of the deoxyadenosine deaminase TadA-8e. sABE shows high on-target editing activity comparable to the original ABE with TadA-8e (ABE8e) upon rapamycin induction while maintaining low background activity without induction. Importantly, sABE exhibits a narrower activity window on DNA and higher precision than ABE8e, with an improved single-to-double ratio of adenine editing and reduced genomic and transcriptomic off-target effects. sABE can achieve gene knockout through multiplex splice donor disruption in human cells. Furthermore, when delivered via dual adeno-associated virus vectors, sABE can efficiently convert a single A•T base pair to a G•C base pair on the PCSK9 gene in mouse liver, demonstrating in vivo CID-controlled DNA base editing. Thus, sABE enables precise control of base editing, which will have broad implications for basic research and in vivo therapeutic applications.

Gene editing therapeutics based on mRNA delivery

The field of gene editing has received much attention in recent years due to its immense therapeutic potential. In particular, gene editing therapeutics, such as the CRISPR-Cas systems, base editors, and other emerging gene editors, offer the opportunity to address previously untreatable disorders. This review aims to summarize the therapeutic applications of gene editing based on mRNA delivery. We introduce gene editing therapeutics using mRNA and focus on engineering and improvement of gene editing technology. We subsequently examine ex vivo and in vivo gene editing techniques and conclude with an exploration of the next generation of CRISPR and base editing systems.

Lipid nanoparticles (LNPs) for in vivo RNA delivery and their breakthrough technology for future applications

RNA therapeutics show a significant breakthrough for the treatment of otherwise incurable diseases and genetic disorders by regulating disease-related gene expression. The successful development of COVID-19 mRNA vaccines further emphasizes the potential of RNA therapeutics in the prevention of infectious diseases as well as in the treatment of chronic diseases. However, the efficient delivery of RNA into cells remains a challenge, and nanoparticle delivery systems such as lipid nanoparticles (LNPs) are necessary to fully realize the potential of RNA therapeutics. While LNPs provide a highly efficient platform for the in vivo delivery of RNA by overcoming various biological barriers, several challenges remain to be resolved for further development and regulatory approval. These include a lack of targeted delivery to extrahepatic organs and a gradual loss of therapeutic potency with repeated doses. In this review, we highlight the fundamental aspects of LNPs and their uses in the development of novel RNA therapeutics. Recent advances in LNP-based therapeutics and preclinical/clinical studies are overviewed. Lastly, we discuss the current limitations of LNPs and introduce breakthrough technologies that might overcome these challenges in future applications.

Targeting PCSK9 and Beyond for the Management of Low-Density Lipoprotein Cholesterol

Reducing low-density lipoprotein cholesterol (LDL-C) levels is crucial to the prevention of atherosclerotic cardiovascular disease (ASCVD). However, many patients, especially those at very high ASCVD risk or with familial hypercholesterolemia (FH), do not achieve target LDL-C levels with statin monotherapy. The underutilization of novel lipid-lowering therapies (LLT) globally may be due to cost concerns or therapeutic inertia. Emerging approaches have the potential to lower LDL-C and reduce ASCVD risk further, in addition to offering alternatives for statin-intolerant patients. Shifting the treatment paradigm towards initial combination therapy and utilizing novel LLT strategies can complement existing treatments. This review discusses innovative approaches including combination therapies involving statins and agents like ezetimibe, bempedoic acid, cholesterol ester transfer protein (CETP) inhibitors as well as strategies targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) and angiopoietin-like protein 3 (ANGPTL3) inhibition. Advances in nucleic acid-based therapies and gene editing are innovative approaches that will improve patient compliance and adherence. These strategies demonstrate significant LDL-C reductions and improved cardiovascular outcomes, offering potential for optimal LDL-C control and reduced ASCVD risk. By addressing the limitations of statin monotherapy, these approaches provide new management options for elevated LDL-C levels.

Genome editing and cancer therapy: handling the hypoxia-responsive pathway as a promising strategy

The precise characterization of oxygen-sensing pathways and the identification of pO2-regulated gene expression are both issues of critical importance. The O2-sensing system plays crucial roles in almost all the pivotal human processes, including the stem cell specification, the growth and development of tissues (such as embryogenesis), the modulation of intermediate metabolism (including the shift of the glucose metabolism from oxidative to anaerobic ATP production and vice versa), and the control of blood pressure. The solid cancer microenvironment is characterized by low oxygen levels and by the consequent activation of the hypoxia response that, in turn, allows a complex adaptive response characterized mainly by neoangiogenesis and metabolic reprogramming. Recently, incredible advances in molecular genetic methodologies allowed the genome editing with high efficiency and, above all, the precise identification of target cells/tissues. These new possibilities and the knowledge of the mechanisms of adaptation to hypoxia suggest the effective development of new therapeutic approaches based on the manipulation, targeting, and exploitation of the oxygen-sensor system molecular mechanisms.

MK-0616: an oral PCSK9 inhibitor for hypercholesterolemia treatment

INTRODUCTION

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of morbidity and mortality worldwide. Lowering LDL-cholesterol, by lifestyle modification or therapeutically, reduces the risk of ASCVD. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a protein which binds to the LDL-receptor and induces degradation, is a clinically validated target to lower LDL-cholesterol. Injectable PCSK9 inhibitor therapies have demonstrated substantial reductions in LDL-cholesterol with associated decreased risk of ASCVD events.

AREAS COVERED

MK-0616 is an orally bioavailable, renally excreted, macrocyclic peptide inhibitor of PCSK9. The article provides an understanding of the chemistry and development, pharmacokinetic and pharmacodynamic characteristics of MK-0616 and insight into its clinical efficacy and safety. In clinical trials, MK-0616 produced dose-dependent reductions in LDL-cholesterol, non-HDL-cholesterol, and apolipoprotein (apo) B levels. Furthermore, MK-0616 modestly lowered lipoprotein (a) [Lp(a)].

EXPERT OPINION

MK-0616 is a potent, oral macrocyclic peptide inhibitor of PCSK9 that is not only able to reduce LDL-cholesterol, non-HDL-cholesterol, and apoB, but can also lower Lp(a). Safety and tolerability studies reported to date are promising. MK-0616 may offer advantages over injectable anti-PCSK9 therapies in terms of ease of dosing, patient preference and cost. The results from phase III trials of MK-0616 on cardiovascular outcomes are awaited with interest.

Gene Therapy for Paediatric Homozygous Familial Hypercholesterolaemia

The clinical outcome for children and adolescents with homozygous familial hypercholesterolaemia (HoFH) can be devastating, and treatment options are limited in the presence of a null variant. In HoFH, atherosclerotic risk accumulates from birth. Gene therapy is an appealing treatment option as restoration of low-density lipoprotein receptor (LDLR) gene function could provide a cure for HoFH. A clinical trial using a recombinant adeno-associated vector (rAAV) to deliver LDLR DNA to adult patients with HoFH was recently completed; results have not yet been reported. However, this treatment strategy may face challenges when translating to the paediatric population. The paediatric liver undergoes substantial growth which is significant as rAAV vector DNA persists primarily as episomes (extra-chromosomal DNA) and are not replicated during cell division. Therefore, rAAV-based gene addition treatment administered in childhood would likely only have a transient effect. With over 2,000 unique variants in LDLR, a goal of genomic editing-based therapy development would be to treat most (if not all) mutations with a single set of reagents. For a robust, durable effect, LDLR must be repaired in the genome of hepatocytes, which could be achieved using genomic editing technology such as clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 and a DNA repair strategy such as homology-independent targeted integration. This review discusses this issue in the context of the paediatric patient group with severe compound heterozygous or homozygous null variants which are associated with aggressive early-onset atherosclerosis and myocardial infarction, together with the important pre-clinical studies that use genomic editing strategies to treat HoFH in place of apheresis and liver transplantation.

Enrichment strategies to enhance genome editing

Genome editing technologies hold great promise for numerous applications including the understanding of cellular and disease mechanisms and the development of gene and cellular therapies. Achieving high editing frequencies is critical to these research areas and to achieve the overall goal of being able to manipulate any target with any desired genetic outcome. However, gene editing technologies sometimes suffer from low editing efficiencies due to several challenges. This is often the case for emerging gene editing technologies, which require assistance for translation into broader applications. Enrichment strategies can support this goal by selecting gene edited cells from non-edited cells. In this review, we elucidate the different enrichment strategies, their many applications in non-clinical and clinical settings, and the remaining need for novel strategies to further improve genome research and gene and cellular therapy studies.

Striated muscle-specific base editing enables correction of mutations causing dilated cardiomyopathy

Dilated cardiomyopathy is the second most common cause for heart failure with no cure except a high-risk heart transplantation. Approximately 30% of patients harbor heritable mutations which are amenable to CRISPR-based gene therapy. However, challenges related to delivery of the editing complex and off-target concerns hamper the broad applicability of CRISPR agents in the heart. We employ a combination of the viral vector AAVMYO with superior targeting specificity of heart muscle tissue and CRISPR base editors to repair patient mutations in the cardiac splice factor Rbm20, which cause aggressive dilated cardiomyopathy. Using optimized conditions, we repair >70% of cardiomyocytes in two Rbm20 knock-in mouse models that we have generated to serve as an in vivo platform of our editing strategy. Treatment of juvenile mice restores the localization defect of RBM20 in 75% of cells and splicing of RBM20 targets including TTN. Three months after injection, cardiac dilation and ejection fraction reach wild-type levels. Single-nuclei RNA sequencing uncovers restoration of the transcriptional profile across all major cardiac cell types and whole-genome sequencing reveals no evidence for aberrant off-target editing. Our study highlights the potential of base editors combined with AAVMYO to achieve gene repair for treatment of hereditary cardiac diseases.

A Review of Progress on Targeting LDL Receptor-Dependent and -Independent Pathways for the Treatment of Hypercholesterolemia, a Major Risk Factor of ASCVD

Since the discovery of the LDL receptor in 1973 by Brown and Goldstein as a causative protein in hypercholesterolemia, tremendous amounts of effort have gone into finding ways to manage high LDL cholesterol in familial hypercholesterolemic (HoFH and HeFH) individuals with loss-of-function mutations in the LDL receptor (LDLR) gene. Statins proved to be the first blockbuster drug, helping both HoFH and HeFH individuals by inhibiting the cholesterol synthesis pathway rate-limiting enzyme HMG-CoA reductase and inducing the LDL receptor. However, statins could not achieve the therapeutic goal of LDL. Other therapies targeting LDLR include PCSK9, which lowers LDLR by promoting LDLR degradation. Inducible degrader of LDLR (IDOL) also controls the LDLR protein, but an IDOL-based therapy is yet to be developed. Among the LDLR-independent pathways, such as angiopoietin-like 3 (ANGPTL3), apolipoprotein (apo) B, apoC-III and CETP, only ANGPTL3 offers the advantage of treating both HoFH and HeFH patients and showing relatively better preclinical and clinical efficacy in animal models and hypercholesterolemic individuals, respectively. While loss-of-LDLR-function mutations have been known for decades, gain-of-LDLR-function mutations have recently been identified in some individuals. The new information on gain of LDLR function, together with CRISPR-Cas9 genome/base editing technology to target LDLR and ANGPTL3, offers promise to HoFH and HeFH individuals who are at a higher risk of developing atherosclerotic cardiovascular disease (ASCVD).

Liver-specific in vivo base editing of Angptl3 via AAV delivery efficiently lowers blood lipid levels in mice

BACKGROUND

Gene editing has emerged as an exciting therapeutic development platform for numerous genetic and nongenetic diseases. Targeting lipid-modulating genes such as angiopoietin-related protein 3 (ANGPTL3) with gene editing offers hope for a permanent solution to lower cardiovascular disease risks associated with hypercholesterolemia.

RESULTS

In this study, we developed a hepatocyte-specific base editing therapeutic approach delivered by dual adeno-associated virus (AAV) to enable hepatocyte-specific targeting of Angptl3 to lower blood lipid levels. Systemic AAV9-mediated delivery of AncBE4max, a cytosine base editor (CBE), targeting mouse Angptl3 resulted in the installation of a premature stop codon in Angptl3 with an average efficiency of 63.3 ± 2.3% in the bulk liver tissue. A near-complete knockout of the ANGPTL3 protein in the circulation were observed within 2-4 weeks following AAV administration. Furthermore, the serum levels of triglyceride (TG) and total cholesterol (TC) were decreased by approximately 58% and 61%, respectively, at 4 weeks after treatment.

CONCLUSIONS

These results highlight the promise of liver-targeted Angptl3 base editing for blood lipid control.

The evolving landscape of PCSK9 inhibition in cancer

Cancer is a disease with a significant global burden in terms of premature mortality, loss of productivity, healthcare expenditures, and impact on mental health. Recent decades have seen numerous advances in cancer research and treatment options. Recently, a new role of cholesterol-lowering PCSK9 inhibitor therapy has come to light in the context of cancer. PCSK9 is an enzyme that induces the degradation of low-density lipoprotein receptors (LDLRs), which are responsible for clearing cholesterol from the serum. Thus, PCSK9 inhibition is currently used to treat hypercholesterolemia, as it can upregulate LDLRs and enable cholesterol reduction through these receptors. The cholesterol-lowering effects of PCSK9 inhibitors have been suggested as a potential mechanism to combat cancer, as cancer cells have been found to increasingly rely on cholesterol for their growth needs. Additionally, PCSK9 inhibition has demonstrated the potential to induce cancer cell apoptosis through several pathways, increase the efficacy of a class of existing anticancer therapies, and boost the host immune response to cancer. A role in managing cancer- or cancer treatment-related development of dyslipidemia and life-threatening sepsis has also been suggested. This review examines the current evidence regarding the effects of PCSK9 inhibition in the context of different cancers and cancer-associated complications.