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

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.

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.

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.

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.

Base Editing and Prime Editing: Potential Therapeutic Options for Rare and Common Diseases

Collectively, genetic disorders affect approximately 350 million individuals worldwide and are a major global health burden. Despite substantial progress in identification of new disease-causing genes, variants, and molecular etiologies, nearly all rare diseases have no targeted therapeutics that can address their underlying molecular causes. Base editing (BE) and prime editing (PE), two newly described iterations of CRISPR-Cas9 genome editing, represent potential therapeutic strategies that could be used to precisely, efficiently, permanently, and safely correct patients' pathogenic variants and ameliorate disease sequelae. Unlike "standard" CRISPR-Cas9 genome editing, these technologies do not rely on double-strand break (DSB) formation, thus improving safety by decreasing the likelihood of undesired insertions and deletions (indels) at the target site. Here, we provide an overview of BE and PE, including their structures, mechanisms, and differences from standard CRISPR-Cas9 genome editing. We describe several examples of the use of BE and PE to improve rare and common disease phenotypes in preclinical models and human patients, with an emphasis on in vivo editing efficacy, safety, and delivery method. We also discuss recently developed delivery methods for these technologies that may be used in future clinical settings.

Rapid and definitive treatment of phenylketonuria in variant-humanized mice with corrective editing

Phenylketonuria (PKU), an autosomal recessive disorder caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene, results in the accumulation of blood phenylalanine (Phe) to neurotoxic levels. Current dietary and medical treatments are chronic and reduce, rather than normalize, blood Phe levels. Among the most frequently occurring PAH variants in PKU patients is the P281L (c.842C>T) variant. Using a CRISPR prime-edited hepatocyte cell line and a humanized PKU mouse model, we demonstrate efficient in vitro and in vivo correction of the P281L variant with adenine base editing. With the delivery of ABE8.8 mRNA and either of two guide RNAs in vivo using lipid nanoparticles (LNPs) in humanized PKU mice, we observe complete and durable normalization of blood Phe levels within 48 h of treatment, resulting from corrective PAH editing in the liver. These studies nominate a drug candidate for further development as a definitive treatment for a subset of PKU patients.

Base editors: development and applications in biomedicine

Base editor (BE) is a gene-editing tool developed by combining the CRISPR/Cas system with an individual deaminase, enabling precise single-base substitution in DNA or RNA without generating a DNA double-strand break (DSB) or requiring donor DNA templates in living cells. Base editors offer more precise and secure genome-editing effects than other conventional artificial nuclease systems, such as CRISPR/Cas9, as the DSB induced by Cas9 will cause severe damage to the genome. Thus, base editors have important applications in the field of biomedicine, including gene function investigation, directed protein evolution, genetic lineage tracing, disease modeling, and gene therapy. Since the development of the two main base editors, cytosine base editors (CBEs) and adenine base editors (ABEs), scientists have developed more than 100 optimized base editors with improved editing efficiency, precision, specificity, targeting scope, and capacity to be delivered in vivo, greatly enhancing their application potential in biomedicine. Here, we review the recent development of base editors, summarize their applications in the biomedical field, and discuss future perspectives and challenges for therapeutic applications.

Epigenome Editing Durability Varies Widely Across Cardiovascular Disease Target Genes

Background

Hepatic knockdown of the proprotein convertase subtilisin/kexin type 9 ( PCSK9 ) gene or the angiopoietin-like 3 ( ANGPTL3 ) gene has been demonstrated to reduce blood low-density lipoprotein cholesterol (LDL-C) levels, and hepatic knockdown of the angiotensinogen ( AGT ) gene has been demonstrated to reduce blood pressure. Genome editing can productively target each of these three genes in hepatocytes in the liver, offering the possibility of durable "one-and-done" therapies for hypercholesterolemia and hypertension. However, concerns around making permanent gene sequence changes via DNA strand breaks might hinder acceptance of these therapies. Epigenome editing offers an alternative approach to gene inactivation, via silencing of gene expression by methylation of the promoter region, but the long-term durability of epigenome editing remains to be established.

Methods

We assessed the ability of epigenome editing to durably reduce the expression of the human PCSK9, ANGPTL3 , and AGT genes in HuH-7 hepatoma cells. Using the CRISPRoff epigenome editor, we identified guide RNAs that produced efficient gene knockdown immediately after transfection. We assessed the durability of gene expression and methylation changes through serial cell passages.

Results

Cells treated with CRISPRoff and PCSK9 guide RNAs were maintained for up to 124 cell doublings and demonstrated durable knockdown of gene expression and increased CpG dinucleotide methylation in the promoter, exon 1, and intron 1 regions. In contrast, cells treated with CRISPRoff and ANGPTL3 guide RNAs experienced only transient knockdown of gene expression. Cells treated with CRISPRoff and AGT guide RNAs also experienced transient knockdown of gene expression; although initially there was increased CpG methylation throughout the early part of the gene, this methylation was geographically heterogeneous-transient in the promoter, and stable in intron 1.

Conclusions

This work demonstrates precise and durable gene regulation via methylation, supporting a new therapeutic approach for protection against cardiovascular disease via knockdown of genes such as PCSK9 . However, the durability of knockdown with methylation changes is not generalizable across target genes, likely limiting the therapeutic potential of epigenome editing compared to other modalities.

Human disease models in drug development

Biomedical research is undergoing a paradigm shift towards approaches centred on human disease models owing to the notoriously high failure rates of the current drug development process. Major drivers for this transition are the limitations of animal models, which, despite remaining the gold standard in basic and preclinical research, suffer from interspecies differences and poor prediction of human physiological and pathological conditions. To bridge this translational gap, bioengineered human disease models with high clinical mimicry are being developed. In this Review, we discuss preclinical and clinical studies that benefited from these models, focusing on organoids, bioengineered tissue models and organs-on-chips. Furthermore, we provide a high-level design framework to facilitate clinical translation and accelerate drug development using bioengineered human disease models.

Genome editing, a superior therapy for inherited retinal diseases

Gene augmentation and genome editing are promising strategies for the treatment of monogenic inherited retinal diseases. Although gene augmentation treatments are commercially available for inherited retinal diseases, there are many shortcomings that need to be addressed, like progressive retinal degeneration and diminishing efficacy over time. Innovative CRISPR-Cas9-based genome editing technologies have broadened the proportion of treatable genetic disorders and can greatly improve or complement treatment outcomes from gene augmentation. Progress in this relatively new field involves the development of therapeutics including gene disruption, ablate-and-replace strategies, and precision gene correction techniques, such as base editing and prime editing. By making direct edits to endogenous DNA, genome editing theoretically guarantees permanent gene correction and long-lasting treatment effects. Improvements to delivery modalities aimed at limiting persistent gene editor activity have displayed an improved safety profile and minimal off-target editing. Continued progress to advance precise gene correction and associated delivery strategies will establish genome editing as the preferred treatment for genetic retinal disorders. This commentary describes the applications, strengths, and drawbacks of conventional gene augmentation approaches, recent advances in precise genome editing in the retina, and promising preclinical strategies to facilitate the use of robust genome editing therapies in human patients.

Base editing rescue of spinal muscular atrophy in cells and in mice

Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality, arises from survival motor neuron (SMN) protein insufficiency resulting from SMN1 loss. Approved therapies circumvent endogenous SMN regulation and require repeated dosing or may wane. We describe genome editing of SMN2, an insufficient copy of SMN1 harboring a C6>T mutation, to permanently restore SMN protein levels and rescue SMA phenotypes. We used nucleases or base editors to modify five SMN2 regulatory regions. Base editing converted SMN2 T6>C, restoring SMN protein levels to wild type. Adeno-associated virus serotype 9-mediated base editor delivery in Δ7SMA mice yielded 87% average T6>C conversion, improved motor function, and extended average life span, which was enhanced by one-time base editor and nusinersen coadministration (111 versus 17 days untreated). These findings demonstrate the potential of a one-time base editing treatment for SMA.

CRISPR-Cas System: The Current and Emerging Translational Landscape

CRISPR-Cas technology has rapidly changed life science research and human medicine. The ability to add, remove, or edit human DNA sequences has transformative potential for treating congenital and acquired human diseases. The timely maturation of the cell and gene therapy ecosystem and its seamless integration with CRISPR-Cas technologies has enabled the development of therapies that could potentially cure not only monogenic diseases such as sickle cell anemia and muscular dystrophy, but also complex heterogenous diseases such as cancer and diabetes. Here, we review the current landscape of clinical trials involving the use of various CRISPR-Cas systems as therapeutics for human diseases, discuss challenges, and explore new CRISPR-Cas-based tools such as base editing, prime editing, CRISPR-based transcriptional regulation, CRISPR-based epigenome editing, and RNA editing, each promising new functionality and broadening therapeutic potential. Finally, we discuss how the CRISPR-Cas system is being used to understand the biology of human diseases through the generation of large animal disease models used for preclinical testing of emerging therapeutics.

Recent advances in therapeutic CRISPR-Cas9 genome editing: mechanisms and applications

Recently, clustered regularly interspaced palindromic repeats (CRISPR)-Cas9 derived editing tools had significantly improved our ability to make desired changes in the genome. Wild-type Cas9 protein recognizes the target genomic loci and induced local double strand breaks (DSBs) in the guidance of small RNA molecule. In mammalian cells, the DSBs are mainly repaired by endogenous non-homologous end joining (NHEJ) pathway, which is error prone and results in the formation of indels. The indels can be harnessed to interrupt gene coding sequences or regulation elements. The DSBs can also be fixed by homology directed repair (HDR) pathway to introduce desired changes, such as base substitution and fragment insertion, when proper donor templates are provided, albeit in a less efficient manner. Besides making DSBs, Cas9 protein can be mutated to serve as a DNA binding platform to recruit functional modulators to the target loci, performing local transcriptional regulation, epigenetic remolding, base editing or prime editing. These Cas9 derived editing tools, especially base editors and prime editors, can introduce precise changes into the target loci at a single-base resolution and in an efficient and irreversible manner. Such features make these editing tools very promising for therapeutic applications. This review focuses on the evolution and mechanisms of CRISPR-Cas9 derived editing tools and their applications in the field of gene therapy.

A luciferase reporter mouse model to optimize in vivo gene editing validated by lipid nanoparticle delivery of adenine base editors

The rapid development of CRISPR genome editing technology has provided the potential to treat genetic diseases effectively and precisely. However, efficient and safe delivery of genome editors to affected tissues remains a challenge. Here, we developed luminescent ABE (LumA), a luciferase reporter mouse model containing the R387X mutation (c.A1159T) in the luciferase gene located in the Rosa26 locus of the mouse genome. This mutation eliminates luciferase activity but can be restored upon A-to-G correction by SpCas9 adenine base editors (ABEs). The LumA mouse model was validated through intravenous injection of two FDA-approved lipid nanoparticle (LNP) formulations consisting of either MC3 or ALC-0315 ionizable cationic lipids, encapsulated with ABE mRNA and LucR387X-specific guide RNA (gRNA). Whole-body bioluminescence live imaging showed consistent restoration of luminescence lasting up to 4 months in treated mice. Compared with mice carrying the wild-type luciferase gene, the ALC-0315 and MC3 LNP groups showed 83.5% ± 17.5% and 8.4% ± 4.3% restoration of luciferase activity in the liver, respectively, as measured by tissue luciferase assays. These results demonstrated successful development of a luciferase reporter mouse model that can be used to evaluate the efficacy and safety of different genome editors, LNP formulations, and tissue-specific delivery systems for optimizing genome editing therapeutics.

Foetal genome editing

PURPOSE OF REVIEW

The development of modern gene editing tools alongside promising innovations in gene sequencing and prenatal diagnostics as well as a shifting regulatory climate around targeted therapeutics offer an opportunity to address monogenic diseases prior to the onset of pathology. In this review, we seek to highlight recent progress in preclinical studies evaluating the potential in-utero gene editing as a treatment for monogenic diseases that cause morbidity or mortality before or shortly after birth.

RECENT FINDINGS

There has been significant recent progress in clinical trials for postnatal gene editing. Corresponding advances have been made with respect to in-utero cell and enzyme replacement therapies. These precedents establish the foundation for 'one-shot' treatments by way in-utero gene editing. Compelling preclinical data in liver, pulmonary and multisystemic diseases demonstrate the potential benefits of in-utero editing approaches.

SUMMARY

Recent proof-of-concept studies have demonstrated the safety and feasibility of in-utero gene editing across multiple organ systems and in numerous diseases. Clinical translation will require continued evolution of vectors and editing approaches to maximize efficiency and minimize unwanted treatment effects.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) in the central nervous system

The gene encoding proprotein convertase subtilisin/kexin type 9 (PCSK9) and its protein product have been widely studied for their role in cholesterol and lipid metabolism. PCSK9 increases the rate of metabolic degradation of low-density lipoprotein receptors, preventing the diffusion of low-density lipoprotein (LDL) from plasma into cells and contributes to high lipoprotein-bound cholesterol levels in the plasma. While most research has focused on the regulation and disease relevance of PCSK9 to the cardiovascular system and lipid metabolism, there is a growing body of evidence that PCSK9 plays a crucial role in pathogenic processes in other organ systems, including the central nervous system. PCSK9's impact on the brain is not yet fully understood, though several recent studies have sought to illuminate its impact on various neurodegenerative and psychiatric disorders, as well as its connection with ischemic stroke. Cerebral PCSK9 expression is low but is highly upregulated during disease states. Among others, PCSK9 is known to play a role in neurogenesis, neural cell differentiation, central LDL receptor metabolism, neural cell apoptosis, neuroinflammation, Alzheimer's Disease, Alcohol Use Disorder, and stroke. The PCSK9 gene contains several polymorphisms, including both gain-of-function and loss-of-function mutations which profoundly impact normal PCSK9 signaling and cholesterol metabolism. Gain-of-function mutations lead to persistent hypercholesterolemia and poor health outcomes, while loss-of-function mutations generally lead to hypocholesterolemia and may serve as a protective factor against diseases of the liver, cardiovascular system, and central nervous system. Recent genomic studies have sought to identify the end-organ effects of such mutations and continue to identify evidence of a much broader role for PCSK9 in extrahepatic organ systems. Despite this, there remain large gaps in our understanding of PCSK9, its regulation, and its effects on disease risk outside the liver. This review, which incorporates data from a wide range of scientific disciplines and experimental paradigms, is intended to describe PCSK9's role in the central nervous system as it relates to cerebral disease and neuropsychiatric disorders, and to examine the clinical potential of PCSK9 inhibitors and genetic variation in the PCSK9 gene on disease outcomes, including neurological and neuropsychiatric disease.

Shaping the future from the small scale: dry powder inhalation of CRISPR-Cas9 lipid nanoparticles for the treatment of lung diseases

INTRODUCTION

Most lung diseases are serious conditions resulting from genetic and environmental causes associated with high mortality and severe symptoms. Currently, treatments available have a palliative effect and many targets are still considered undruggable. Gene therapy stands as an attractive approach to offering innovative therapeutic solutions. CRISPRCas9 has established a remarkable potential for genome editing with high selectivity to targeted mutations. To ensure high efficacy with minimum systemic exposure, the delivery and administration route are key components that must be investigated.

AREAS COVERED

This review is focused on the delivery of CRISPRCas9 to the lungs, taking advantage of lipid nanoparticles (LNPs), the most clinically advanced nucleic acid carriers. We also aim to highlight the benefits of pulmonary administration as a local delivery route and the use of spray drying to prepare stable nucleic-acid-based dry powder formulations that can overcome multiple lung barriers.

EXPERT OPINION

Exploring the pulmonary administration to deliver CRISPRCas9 loaded in LNPs as a dry powder increases the chances to achieve high efficacy and reduced adverse effects. CRISPRCas9 loaded in LNP-embedded microparticles has not yet been reported in the literature but has the potential to reach and accumulate in target cells in the lung, thus, enhancing overall efficacy and safety.

Pharmacotherapy in familial hypercholesterolemia - Current state and emerging paradigms

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

CRISPR and cardiovascular diseases

CRISPR technologies have progressed by leaps and bounds over the past decade, not only having a transformative effect on biomedical research but also yielding new therapies that are poised to enter the clinic. In this review, I give an overview of (i) the various CRISPR DNA-editing technologies, including standard nuclease gene editing, base editing, prime editing, and epigenome editing, (ii) their impact on cardiovascular basic science research, including animal models, human pluripotent stem cell models, and functional screens, and (iii) emerging therapeutic applications for patients with cardiovascular diseases, focusing on the examples of hypercholesterolaemia, transthyretin amyloidosis, and Duchenne muscular dystrophy.

New CRISPR Technology for Creating Cell Models of Lipoprotein Assembly and Secretion

PURPOSE OF REVIEW

This review is aimed at providing an overview of new developments in gene editing technology, including examples of how this technology has been used to develop cell models for studying the effects of gene ablation or missense mutations on lipoprotein assembly and secretion.

RECENT FINDINGS

CRISPR/Cas9-mediated gene editing is superior to other technologies because of its ease, sensitivity, and low off-target effects. This technology has been used to study the importance of microsomal triglyceride transfer protein in the assembly and secretion of apolipoprotein B-containing lipoproteins, as well as to establish causal effects of APOB gene missense mutations on lipoprotein assembly and secretion. CRISPR/Cas9 technology is anticipated to provide unprecedented flexibility in studying protein structure and function in cells and animals and to yield mechanistic insights into variants in the human genome.

Prime editing in hematopoietic stem cells—From ex vivo to in vivo CRISPR-based treatment of blood disorders

Prime editing of human hematopoietic stem cells has the potential to become a safe and efficient way of treating diseases of the blood directly in patients. By allowing site-targeted gene intervention without homology-directed repair donor templates and DNA double-stranded breaks, the invention of prime editing fuels the exploration of alternatives to conventional recombination-based ex vivo genome editing of hematopoietic stem cells. Prime editing is as close as we get today to a true genome editing drug that does not require a separate DNA donor. However, to adapt the technology to perform in vivo gene correction, key challenges remain to be solved, such as identifying effective prime editing guide RNAs for clinical targets as well as developing efficient vehicles to deliver prime editors to stem cells in vivo. In this review, we summarize the current progress in delivery of prime editors both in vitro and in vivo and discuss future challenges that need to be adressed to allow in vivo prime editing as a cure for blood disorders.

Recent advances in CRISPR-based genome editing technology and its applications in cardiovascular research

The rapid development of genome editing technology has brought major breakthroughs in the fields of life science and medicine. In recent years, the clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing toolbox has been greatly expanded, not only with emerging CRISPR-associated protein (Cas) nucleases, but also novel applications through combination with diverse effectors. Recently, transposon-associated programmable RNA-guided genome editing systems have been uncovered, adding myriads of potential new tools to the genome editing toolbox. CRISPR-based genome editing technology has also revolutionized cardiovascular research. Here we first summarize the advances involving newly identified Cas orthologs, engineered variants and novel genome editing systems, and then discuss the applications of the CRISPR-Cas systems in precise genome editing, such as base editing and prime editing. We also highlight recent progress in cardiovascular research using CRISPR-based genome editing technologies, including the generation of genetically modified in vitro and animal models of cardiovascular diseases (CVD) as well as the applications in treating different types of CVD. Finally, the current limitations and future prospects of genome editing technologies are discussed.

Identification of exceptionally potent adenosine deaminases RNA editors from high body temperature organisms

The most abundant form of RNA editing in metazoa is the deamination of adenosines into inosines (A-to-I), catalyzed by ADAR enzymes. Inosines are read as guanosines by the translation machinery, and thus A-to-I may lead to protein recoding. The ability of ADARs to recode at the mRNA level makes them attractive therapeutic tools. Several approaches for Site-Directed RNA Editing (SDRE) are currently under development. A major challenge in this field is achieving high on-target editing efficiency, and thus it is of much interest to identify highly potent ADARs. To address this, we used the baker yeast Saccharomyces cerevisiae as an editing-naïve system. We exogenously expressed a range of heterologous ADARs and identified the hummingbird and primarily mallard-duck ADARs, which evolved at 40-42°C, as two exceptionally potent editors. ADARs bind to double-stranded RNA structures (dsRNAs), which in turn are temperature sensitive. Our results indicate that species evolved to live with higher core body temperatures have developed ADAR enzymes that target weaker dsRNA structures and would therefore be more effective than other ADARs. Further studies may use this approach to isolate additional ADARs with an editing profile of choice to meet specific requirements, thus broadening the applicability of SDRE.

Gene editing for dyslipidemias: New tools to "cut" lipids

Effective lipid lowering therapies are essential for the prevention of atherosclerosis and cardiovascular disease. Available treatments have evolved in both their efficacy and their frequency of administration, and currently include monoclonal antibodies, antisense oligonucleotides and siRNA approaches. However, an unmet need remains for more effective and long-lasting therapeutics. Gene editing permanently alters endogenous gene expression and has the potential to revolutionize disease treatment. Despite the existence of several gene editing approaches, the CRISPR/Cas9 system has emerged as the preferred technology because of its high efficiency and relative simplicity. This review provides a general overview of this promising technology and an update on the progress made towards the development of treatments of dyslipidemia. The recently started phase 1b gene editing clinical trial targeting PCSK9 in patients with heterozygous familial hypercholesterolemia and cardiovascular disease highlights how gene editing may become available to treat not only patients affected by rare disorders of lipid metabolism, but also patients that are difficult-to-treat or at high risk. Other targets like ANGPTL3, LDLR, and APOC3 are on track for further pre-clinical development. The identification of novel targets using electronic health record-linked biobanks and human sequencing studies will continue to expand the potential target pool, and clinical assessment of treated patients will provide essential efficacy and safety information on current strategies. Gene editing of genes regulating lipid metabolism holds promise as an exciting new therapeutic approach. However, since gene editing permanently alters a patient's genome, its therapeutic application in humans will require careful safety assessment and ethical considerations.

CRISPR/Cas9-mediated gene editing. A promising strategy in hematological disorders

The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system has revolutionized the gene editing field, making it possible to interrupt, insert or replace a sequence of interest with high precision in the human genome. Its easy design and wide applicability open up a variety of therapeutic alternatives for the treatment of genetic diseases. Indeed, very promising approaches for the correction of hematological disorders have been developed in the recent years, based on the self-renewal and multipotent differentiation properties of hematopoietic stem and progenitor cells, which make this cell subset the ideal target for gene therapy purposes. This technology has been applied in different congenital blood disorders, such as primary immunodeficiencies, X-linked severe combined immunodeficiency, X-linked chronic granulomatous disease or Wiskott-Aldrich syndrome, and inherited bone marrow failure syndromes, such as Fanconi anemia, congenital amegakaryocytic thrombocytopenia or severe congenital neutropenia. Furthermore, CRISPR/Cas9-based gene editing has been implemented successfully as a novel therapy for cancer immunotherapy, by the development of promising strategies such as the use of oncolytic viruses or adoptive cellular therapy to the chimeric antigen receptor-T-cell therapy. Therefore, considering the variety of genes and mutations affected, we can take advantage of the different DNA repair mechanisms by CRISPR/Cas9 in different manners, from homology-directed repair to non-homologous-end-joining to the latest emerging technologies such as base and prime editing. Although the delivery systems into hematopoietic stem and progenitor cells are still the bottleneck of this technology, some of the advances in genome editing shown in this review have already reached a clinical stage and show very promising preliminary results.

Efficient in vivo genome editing prevents hypertrophic cardiomyopathy in mice

Dominant missense pathogenic variants in cardiac myosin heavy chain cause hypertrophic cardiomyopathy (HCM), a currently incurable disorder that increases risk for stroke, heart failure and sudden cardiac death. In this study, we assessed two different genetic therapies-an adenine base editor (ABE8e) and a potent Cas9 nuclease delivered by AAV9-to prevent disease in mice carrying the heterozygous HCM pathogenic variant myosin R403Q. One dose of dual-AAV9 vectors, each carrying one half of RNA-guided ABE8e, corrected the pathogenic variant in ≥70% of ventricular cardiomyocytes and maintained durable, normal cardiac structure and function. An additional dose provided more editing in the atria but also increased bystander editing. AAV9 delivery of RNA-guided Cas9 nuclease effectively inactivated the pathogenic allele, albeit with dose-dependent toxicities, necessitating a narrow therapeutic window to maintain health. These preclinical studies demonstrate considerable potential for single-dose genetic therapies to correct or silence pathogenic variants and prevent the development of HCM.

Targeted dual base editing with Campylobacter jejuni Cas9 by single AAV-mediated delivery

Various CRISPR‒Cas9 orthologs are used in genome engineering. One of the smallest Cas9 orthologs is cjCas9 derived from Campylobacter jejuni, which is a highly specific genome editing tool. Here, we developed cjCas9-based base editors including a cytosine base editor (cjCBEmax) and an adenine base editor (cjABE8e) that can successfully induce endogenous base substitutions by up to 91.2% at the HPD gene in HEK293T cells. Analysis of the base editing efficiency of 13 endogenous target sites showed that the active windows of cjCBEmax and cjABE8e are wider than those of spCas9-based base editors and that their specificities are slightly lower than that of cjCas9. Importantly, engineered cjCas9 and gRNA scaffolds can improve the base editing efficiency of cjABE8e by up to 6.4-fold at the HIF1A gene in HEK293T cells. Due to its small size, cjABE8e can be packaged in a single adeno-associated virus vector with two tandem arrays of gRNAs, and the delivery of the resulting AAV could introduce base substitutions at endogenous ANGPT2 and HPD target sites. Overall, our findings have expanded the potential of the use of base editors for in vivo or ex vivo therapeutic approaches.

Innovations in CRISPR-Based Therapies

Gene and cell therapies have shown tremendous advancement in the last 5 years. Prominent examples include the successful use of CRISPR-edited stem cells for treating blood disorders like sickle cell anemia and beta-thalassemia, and ongoing clinical trials for treating blindness. This mini-review assesses the status of CRISPR-based therapies, both in vivo and ex vivo, and the challenges associated with clinical translation. In vivo CRISPR therapies have been used to treat eye and liver diseases due to the practicality of delivering editing components to the target tissue. In contrast, even though ex vivo CRISPR therapy involves cell isolation, expansion, and infusion, its advantages include characterizing the gene edits before infusion and restricting off-target effects in other tissues. Further, the safety, affordability, and feasibility of CRISPR therapies, especially for treating large number of patients, are discussed.

Advancing targeted protein degradation for metabolic diseases therapy

The development and application of traditional drugs represented by small molecule chemical drugs and biological agents, especially inhibitors, have become the mainstream drug development. In recent years, targeted protein degradation (TPD) technology has become one of the most promising methods to remove specific disease-related proteins using cell self-destruction mechanisms. Many different TPD strategies are emerging based on the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP), including but not limited to proteolysis-targeting chimeras (PROTAC), molecular glues (MG), lysosome targeting chimeras (LYTAC), chaperone-mediated autophagy (CMA)-targeting chimeras, autophagy-targeting chimera (AUTAC), autophagosome-tethering compound (ATTEC), and autophagy-targeting chimera (AUTOTAC). The advent of targeted degradation technology can change most protein targets in human cells from undruggable to druggable, greatly expanding the therapeutic prospect of refractory diseases such as metabolic syndrome. Here, we summarize the latest progress of major TPD technologies, especially in metabolic syndrome and look forward to providing new insights for drug discovery.

Vaccine Formulation Strategies and Challenges Involved in RNA Delivery for Modulating Biomarkers of Cardiovascular Diseases: A Race from Laboratory to Market

It has been demonstrated that noncoding RNAs have significant physiological and pathological roles. Modulation of noncoding RNAs may offer therapeutic approaches as per recent findings. Small RNAs, mostly long noncoding RNAs, siRNA, and microRNAs make up noncoding RNAs. Inhibiting or promoting protein breakdown by binding to 3' untranslated regions of target mRNA, microRNAs post-transcriptionally control the pattern of gene expression. Contrarily, long non-coding RNAs perform a wider range of tasks, including serving as molecular scaffolding, decoys, and epigenetic regulators. This article provides instances of long noncoding RNAs and microRNAs that may be a biomarker of CVD (cardiovascular disease). In this paper we highlight various RNA-based vaccine formulation strategies designed to target these biomarkers-that are either currently in the research pipeline or are in the global pharmaceutical market-along with the physiological hurdles that need to be overcome.

Efficacy and Safety of an Investigational Single-Course CRISPR Base-Editing Therapy Targeting PCSK9 in Nonhuman Primate and Mouse Models

BACKGROUND

VERVE-101 is an investigational in vivo CRISPR base-editing medicine designed to alter a single DNA base in the PCSK9 gene, permanently turn off hepatic protein production, and thereby durably lower low-density lipoprotein cholesterol. We test the efficacy, durability, tolerability, and potential for germline editing of VERVE-101 in studies of nonhuman primates and a murine F1 progeny study.

METHODS

Cynomolgus monkeys were given a single intravenous infusion of a vehicle control (n=10) or VERVE-101 at a dose of 0.75 mg/kg (n=4) or 1.5 mg/kg (n=22) with subsequent follow-up up to 476 days. Two studies assessed the potential for germline editing, including sequencing sperm samples from sexually mature male nonhuman primates treated with VERVE-101 and genotyping offspring from female mice treated with the murine surrogate of VERVE-101 (VERVE-101mu).

RESULTS

Liver biopsies 14 days after dosing noted mean PCSK9 editing of 46% and 70% in monkeys treated with VERVE-101 at 0.75 and 1.5 mg/kg, respectively. This translated into mean reductions in blood PCSK9 (proprotein convertase subtilisin/kexin type 9) of 67% and 83% and reductions of low-density lipoprotein cholesterol of 49% and 69% at the 0.75 and 1.5 mg/kg doses, respectively, assessed as time-weighted average change from baseline between day 28 and up to 476 days after dosing. Liver safety monitoring noted a transient rise in alanine aminotransferase and aspartate aminotransferase concentrations after infusion that fully resolved by day 14 with no accompanying change in total bilirubin. In a subset of monkeys necropsied 1 year after dosing, no findings related to VERVE-101 were identified on macroscopic and histopathologic assessment of the liver and other organs. In the study to assess potential germline editing of male nonhuman primates, sperm samples collected after VERVE-101 dosing showed no evidence of PCSK9 editing. Among 436 offspring of female mice treated with a saturating dose of VERVE-101mu, the PCSK9 edit was transmitted in 0 of 436 animals.

CONCLUSIONS

VERVE-101 was well tolerated in nonhuman primates and led to 83% lower blood PCSK9 protein and 69% lower low-density lipoprotein cholesterol with durable effects up to 476 days after dosing. These results have supported the initiation of a first-in-human clinical trial in patients with heterozygous familial hypercholesterolemia and atherosclerotic cardiovascular disease.

Gene therapy for liver diseases - progress and challenges

Gene therapy is poised to revolutionize modern medicine, with seemingly unlimited potential for treating and curing genetic disorders. For otherwise incurable indications, including most inherited metabolic liver disorders, gene therapy provides a realistic therapeutic option. In this Review, we discuss gene supplementation and gene editing involving the use of recombinant adeno-associated virus (rAAV) vectors for the treatment of inherited liver diseases, including updates on several ongoing clinical trials that are producing promising results. Clinical testing has been essential in highlighting many key translational challenges associated with this transformative therapy. In particular, the interaction of a patient's immune system with the vector raises issues of safety and the duration of treatment efficacy. Furthermore, several serious adverse events after the administration of high doses of rAAVs suggest greater involvement of innate immune responses and pre-existing hepatic conditions than initially anticipated. Finally, permanent modification of the host genome associated with rAAV genome integration and gene editing raises concerns about the risk of oncogenicity that require careful evaluation. We summarize the main progress, challenges and pathways forward for gene therapy for liver diseases.

Canadian Regulatory Framework and Regulatory Requirements for Cell and Gene Therapy Products

Health Canada regulates gene therapy products and many cell therapy products as biological drugs under the Canadian Food and Drugs Act and its attendant regulations. Cellular products that meet certain criteria, including minimal manipulation and homologous use, may be subjected to a standards-based approach under the Safety of Human Cells, Tissues and Organs for Transplantation Regulations. The manufacture and clinical testing of cell and gene therapy products (CGTP) presents many challenges beyond those for protein biologics. Cells cannot be subjected to pathogen removal or inactivation procedures and must frequently be administered shortly after final formulation. Viral vector design and manufacturing control are critically important to overall product quality and linked to safety and efficacy in patients through concerns such as replication competence, vector integration, and vector shedding. In addition, for many CGTP, the value of nonclinical studies is largely limited to providing proof of concept, and the first meaningful data relating to appropriate dosing, safety parameters, and validity of surrogate or true determinants of efficacy must come from carefully designed clinical trials in patients. Addressing these numerous challenges requires application of various risk mitigation strategies and meeting regulatory expectations specifically adapted to the product types. Regulatory cooperation and harmonization at an international level are essential for progress in the development and commercialization of these products. However, particularly in the area of cell therapy, new regulatory paradigms may be needed to harness the benefits of clinical progress in situations where the resources and motivation to pursue a typical drug product approval pathway may be lacking. This chapter is dedicated to provide an overview of Health Canada regulatory oversight of CGTP.

The Extent to Which Lipid Nanoparticles Require Apolipoprotein E and Low-Density Lipoprotein Receptor for Delivery Changes with Ionizable Lipid Structure

Lipid nanoparticles (LNPs) have delivered therapeutic RNA to hepatocytes in humans. Adsorption of apolipoprotein E (ApoE) onto these clinical LNP-mRNA drugs has been shown to facilitate hepatocyte entry via the low-density lipoprotein receptor (LDLR). Since ApoE-LDLR trafficking is conserved in mice, non-human primates, and humans, characterizing this mechanism eased clinical transition. Recently, LNPs have delivered mRNA to non-hepatocytes in mice and non-human primates, suggesting they can target new cell types via ApoE- and LDLR-independent pathways. To test this hypothesis, we quantified how 60 LNPs delivered mRNA with cell type resolution in wild-type mice and three knockout mouse strains related to lipid trafficking: ApoE^-/-, LDLR^-/-, and PCSK9^-/-. These data suggest that the hydrophobic tail length of diketopiperazine-based lipids can be changed to drive ApoE- and LDLR-independent delivery in vivo. More broadly, the results support the hypothesis that endogenous LNP trafficking can be tuned by modifying lipid chemistry.

PCSK9 in Liver Cancers at the Crossroads between Lipid Metabolism and Immunity

Metabolic rewiring and defective immune responses are considered to be the main driving forces sustaining cell growth and oncogenesis in many cancers. The atypical enzyme, proprotein convertase subtilisin/kexin type 9 (PCSK9), is produced by the liver in large amounts and plays a major role in lipid metabolism via the control of the low density lipoprotein receptor (LDLR) and other cell surface receptors. In this context, many clinical studies have clearly demonstrated the high efficacy of PCSK9 inhibitors in treating hyperlipidemia and cardiovascular diseases. Recent data implicated PCSK9 in the degradation of major histocompatibility complex I (MHC-I) receptors and the immune system as well as in other physiological activities. This review highlights the complex crosstalk between PCSK9, lipid metabolism and immunosuppression and underlines the latest advances in understanding the involvement of this convertase in other critical functions. We present a comprehensive assessment of the different strategies targeting PCSK9 and show how these approaches could be extended to future therapeutic options to treat cancers with a main focus on the liver.

Translating atherosclerosis research from bench to bedside: navigating the barriers for effective preclinical drug discovery

Cardiovascular disease (CVD) remains the leading cause of death worldwide. An ongoing challenge remains the development of novel pharmacotherapies to treat CVD, particularly atherosclerosis. Effective mechanism-informed development and translation of new drugs requires a deep understanding of the known and currently unknown biological mechanisms underpinning atherosclerosis, accompanied by optimization of traditional drug discovery approaches. Current animal models do not precisely recapitulate the pathobiology underpinning human CVD. Accordingly, a fundamental limitation in early-stage drug discovery has been the lack of consensus regarding an appropriate experimental in vivo model that can mimic human atherosclerosis. However, when coupled with a clear understanding of the specific advantages and limitations of the model employed, preclinical animal models remain a crucial component for evaluating pharmacological interventions. Within this perspective, we will provide an overview of the mechanisms and modalities of atherosclerotic drugs, including those in the preclinical and early clinical development stage. Additionally, we highlight recent preclinical models that have improved our understanding of atherosclerosis and associated clinical consequences and propose model adaptations to facilitate the development of new and effective treatments.

PCSK9 Base Editing Therapeutics and Ischemic Stroke

Individuals with genetic gain-of-function variation in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene are at an increased risk of cardiovascular disease, including ischemic stroke. While PCSK9 inhibitors (PCSK9i) are effective in reducing cardiovascular disease risk and ischemic stroke risk, novel genomic technologies including the use of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 complex-mediated delivery and adenine base editing (ABE) enable promising new therapeutic and preventative approaches. In this paper we discuss ongoing work into PCSK9 base editing and highlight future directions relevant to cardiovascular disease and ischemic stroke.

Immunological barriers to haematopoietic stem cell gene therapy

Cell and gene therapies using haematopoietic stem cells (HSCs) epitomize the transformative potential of regenerative medicine. Recent clinical successes for gene therapies involving autologous HSC transplantation (HSCT) demonstrate the potential of genetic engineering in this stem cell type for curing disease. With recent advances in CRISPR gene-editing technologies, methodologies for the ex vivo expansion of HSCs and non-genotoxic conditioning protocols, the range of clinical indications for HSC-based gene therapies is expected to significantly expand. However, substantial immunological challenges need to be overcome. These include pre-existing immunity to gene-therapy reagents, immune responses to neoantigens introduced into HSCs by genetic engineering, and unique challenges associated with next-generation and off-the-shelf HSC products. By synthesizing these factors in this Review, we hope to encourage more research to address the immunological issues associated with current and next-generation HSC-based gene therapies to help realize the full potential of this field.

Clinical trials and promising preclinical applications of CRISPR/Cas gene editing

Treatment of genetic disorders by genomic manipulation has been the unreachable goal of researchers for many decades. Although our understanding of the genetic basis of genetic diseases has advanced tremendously in the last few decades, the tools developed for genomic editing were not efficient and practical for their use in the clinical setting until now. The recent advancements in the research of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated protein (Cas) systems offered an easy and efficient way to edit the genome and accelerated the research on their potential use in the treatment of genetic disorders. In this review, we summarize the clinical trials that evaluate the CRISPR/Cas systems for treating different genetic diseases and highlight promising preclinical research on CRISPR/Cas mediated treatment of a great diversity of genetic disorders. Ultimately, we discuss the future of CRISPR/Cas mediated genome editing in genetic diseases.

Nanoparticles targeting hematopoietic stem and progenitor cells: Multimodal carriers for the treatment of hematological diseases

Modern-day hematopoietic stem cell (HSC) therapies, such as gene therapy, modify autologous HSCs prior to re-infusion into myelo-conditioned patients and hold great promise for treatment of hematological disorders. While this approach has been successful in numerous clinical trials, it relies on transplantation of ex vivo modified patient HSCs, which presents several limitations. It is a costly and time-consuming procedure, which includes only few patients so far, and ex vivo culturing negatively impacts on the viability and stem cell-properties of HSCs. If viral vectors are used, this carries the additional risk of insertional mutagenesis. A therapy delivered to HSCs in vivo, with minimal disturbance of the HSC niche, could offer great opportunities for novel treatments that aim to reverse disease symptoms for hematopoietic disorders and could bring safe, effective and affordable genetic therapies to all parts of the world. However, substantial unmet needs exist with respect to the in vivo delivery of therapeutics to HSCs. In the last decade, in particular with the development of gene editing technologies such as CRISPR/Cas9, nanoparticles (NPs) have become an emerging platform to facilitate the manipulation of cells and organs. By employing surface modification strategies, different types of NPs can be designed to target specific tissues and cell types in vivo. HSCs are particularly difficult to target due to the lack of unique cell surface markers that can be utilized for cell-specific delivery of therapeutics, and their shielded localization in the bone marrow (BM). Recent advances in NP technology and genetic engineering have resulted in the development of advanced nanocarriers that can deliver therapeutics and imaging agents to hematopoietic stem- and progenitor cells (HSPCs) in the BM niche. In this review we provide a comprehensive overview of NP-based approaches targeting HSPCs to control and monitor HSPC activity in vitro and in vivo, and we discuss the potential of NPs for the treatment of malignant and non-malignant hematological disorders, with a specific focus on the delivery of gene editing tools.

The landscape of mRNA nanomedicine

Messenger RNA (mRNA) is an emerging class of therapeutic agent for the prevention and treatment of a wide range of diseases. The recent success of the two highly efficacious mRNA vaccines produced by Moderna and Pfizer-BioNTech to protect against COVID-19 highlights the huge potential of mRNA technology for revolutionizing life science and medical research. Challenges related to mRNA stability and immunogenicity, as well as in vivo delivery and the ability to cross multiple biological barriers, have been largely addressed by recent progress in mRNA engineering and delivery. In this Review, we present the latest advances and innovations in the growing field of mRNA nanomedicine, in the context of ongoing clinical translation and future directions to improve clinical efficacy.

Long non-coding RNA and RNA-binding protein interactions in cancer: Experimental and machine learning approaches

Understanding the complex and specific roles played by non-coding RNAs (ncRNAs), which comprise the bulk of the genome, is important for understanding virtually every hallmark of cancer. This large group of molecules plays pivotal roles in key regulatory mechanisms in various cellular processes. Regulatory mechanisms, mediated by long non-coding RNA (lncRNA) and RNA-binding protein (RBP) interactions, are well documented in several types of cancer. Their effects are enabled through networks affecting lncRNA and RBP stability, RNA metabolism including N⁶-methyladenosine (m⁶A) and alternative splicing, subcellular localization, and numerous other mechanisms involved in cancer. In this review, we discuss the reciprocal interplay between lncRNAs and RBPs and their involvement in epigenetic regulation via histone modifications, as well as their key role in resistance to cancer therapy. Other aspects of RBPs including their structural domains, provide a deeper knowledge on how lncRNAs and RBPs interact and exert their biological functions. In addition, current state-of-the-art knowledge, facilitated by machine and deep learning approaches, unravels such interactions in better details to further enhance our understanding of the field, and the potential to harness RNA-based therapeutics as an alternative treatment modality for cancer are discussed.