GalNAc-siRNA Conjugates: Leading the Way for Delivery of RNAi Therapeutics

Cell and gene therapeutic approaches in non-alcoholic fatty liver disease

Non-Alcoholic Fatty Liver Disease (NAFLD) refers to a range of conditions marked by the buildup of triglycerides in liver cells, accompanied by inflammation, which contributes to liver damage, clinical symptoms, and histopathological alterations. Multiple molecular pathways contribute to NAFLD pathogenesis, including immune dysregulation, endoplasmic reticulum stress, and tissue injury. Both the innate and adaptive immune systems play crucial roles in disease progression, with intricate crosstalk between liver and immune cells driving NAFLD development. Among emerging therapeutic strategies, cell and gene-based therapies have shown promise. This study reviews the pathophysiological mechanisms of NAFLD and explores the therapeutic potential of cell-based interventions, highlighting their immunomodulatory effects, inhibition of hepatic stellate cells, promotion of hepatocyte regeneration, and potential for hepatocyte differentiation. Additionally, we examine gene delivery vectors designed to target NAFLD, focusing on their role in engineering hepatocytes through gene addition or editing to enhance therapeutic efficacy.

Advances in locally administered nucleic acid therapeutics

Nucleic acid drugs represent the latest generation of precision therapeutics, holding significant promise for the treatment of a wide range of intractable diseases. Delivery technology is crucial for the clinical application of nucleic acid drugs. However, extrahepatic delivery of nucleic acid drugs remains a significant challenge. Systemic administration often fails to achieve sufficient drug enrichment in target tissues. Localized administration has emerged as the predominant approach to facilitate extrahepatic delivery. While localized administration can significantly enhance drug accumulation at the injection sites, nucleic acid drugs still face biological barriers in reaching the target lesions. This review focuses on non-viral nucleic acid drug delivery techniques utilized in local administration for the treatment of extrahepatic diseases. First, the classification of nucleic acid drugs is described. Second, the current major non-viral delivery technologies for nucleic acid drugs are discussed. Third, the bio-barriers, administration approaches, and recent research advances in the local delivery of nucleic acid drugs for treating lung, brain, eye, skin, joint, and heart-related diseases are highlighted. Finally, the challenges associated with the localized therapeutic application of nucleic acid drugs are addressed.

Comprehensive evaluation of siRNA therapeutics on Lp(a): A network meta-analysis

AIMS

To evaluate the efficacy and safety of siRNA drugs that lower Lp(a) in patients with dyslipidaemia.

MATERIALS AND METHODS

A network meta-analysis and systematic review were conducted to compare siRNA drugs targeting Lp(a), based on relevant randomized controlled trials (RCTs). A comprehensive search was performed in PubMed, Embase, Web of Science and the Cochrane Library (up to October 24, 2024). RCTs with an intervention duration of at least 12 weeks were included. Eligible studies compared siRNA drugs that reduce Lp(a), including both Lp(a)-targeted and non-targeted agents, with placebo or other siRNA drugs that reduce Lp(a). The primary outcomes were the percentage reduction and absolute reduction in Lp(a), percentage reduction in low-density lipoprotein cholesterol (LDL-C), percentage reduction in apolipoprotein B (apo(B)), adverse events and serious adverse events, including injection-site reactions. The risk of bias was assessed using the Cochrane Risk of Bias Tool (ROB2), and a random-effects network meta-analysis was performed using the frequentist approach. Confidence in effect estimates was evaluated using the Confidence In Network Meta-Analysis (CINeMA) framework.

RESULTS

A total of 14 trials involving 5646 participants were included. Lp(a)-targeted siRNA agents, particularly Olpasiran, demonstrated strong efficacy in significantly reducing Lp(a) levels, with the greatest percentage reduction in Lp(a) (mean difference [MD]: -92.06%; 95% CI: -102.43% to -81.69%; P-score: 0.98). Olpasiran also showed the greatest absolute reduction in Lp(a) (MD: -250.70 nmol/L; 95% confidence interval [CI]: -279.89 to -221.50; P-score: 0.99). Certain non-Lp(a)-targeted siRNA agents, such as inclisiran and zodasiran, also showed modest reductions in Lp(a) levels, reducing Lp(a) by approximately 15%. Lp(a)-targeted siRNA agents reduced LDL-C by more than 20% and decreased apo(B) by approximately 15%. In terms of safety, most drugs exhibited favourable safety profiles with no significant differences compared to placebo. However, zerlasiran raised concerns regarding injection-site reactions and other adverse events when compared to placebo.

CONCLUSIONS

Lp(a)-targeted siRNA agents have shown robust effectiveness in substantially reducing Lp(a) levels, including both percentage and absolute reductions, with moderate improvements in LDL-C and apo(B) concentrations. Non-Lp(a)-targeted siRNA agents also demonstrate modest reductions in Lp(a) levels. The safety profile is generally favourable, but zerlasiran and inclisiran may increase the incidence of injection-site reactions.

RNA research for drug discovery: Recent advances and critical insight

The field of RNA research has experienced significant changes and is now at the forefront of contemporary drug development. This narrative overview explores the scientific developments and historical turning points in RNA research, emphasising the field's critical significance in the development of novel therapeutics. Important discoveries like antisense oligonucleotides (ASOs), mRNA therapies, and RNA interference (RNAi) have created novel treatment options that can be targeted, such as the ground-breaking mRNA vaccinations against COVID-19. Advances in high-throughput sequencing, single-cell RNA sequencing, and epitranscriptomics have further unravelled the complexity of RNA biology, shedding light on the intricacies of gene regulation and cellular diversity. The integration of computational tools and bioinformatics has propelled the identification of RNA-based biomarkers and the development of RNA therapeutics. Despite significant progress, challenges such as RNA stability, delivery, and off-target effects persist, necessitating continuous innovation and ethical considerations. This review provides a critical insight into the current state and prospects of RNA research, emphasising its transformative potential in drug discovery. By examining the interplay between technological advancements and therapeutic applications, we underscore the promising horizon for RNA-based interventions in treating a myriad of diseases, marking a new era in precision medicine.

Prediction of Interspecies Translation for Targeting Delivery Coefficients of GalNAc-siRNA Silencing Apolipoprotein C-III Using a Mechanistic Minimal Physiologically Based Pharmacokinetic/Pharmacodynamic Model

BACKGROUND AND OBJECTIVE

The emerging N-acetylgalactosamine-small interfering RNA (GalNAc-siRNA) conjugates lead the way for liver-targeting delivery to exert gene-silencing therapeutic effects. To facilitate the drug development of GalNAc-siRNA, further detailed understanding of the key modality-specific mechanisms underlying the temporal discordance between pharmacokinetics and pharmacodynamics and how these processes can be extrapolated from animals to humans is needed.

METHODS

A mechanistic minimal physiologically based pharmacokinetic/pharmacodynamic (mPBPK-PD) model for an investigational new apolipoprotein C-III (APOC3)-silencing GalNAc-siRNA (RBD5044) was developed using available pharmacokinetic/pharmacodynamic (PK/PD) data. The aim was to explore hepatic-targeting delivery processes, the PK/PD relationship, and interspecies translation.

RESULTS

First, multiple PK/PD datasets from mice were satisfactorily fitted using the mPBPK-PD model. Second, we translated the mice model to the monkey model, validated it, and then extrapolated from mice and monkeys to humans to simulate the PK/PD characteristics. We then mechanistically summarized and proposed the essential in vivo delivery processes of GalNAc-siRNA after subcutaneous administration (termed "ADUEB": Absorption [into system circulation], Disposition [distribution to liver target and elimination], Uptake [into hepatocytes], Escape [from endosome and lysosome compartments], and Binding [with argonaute2 to form RNA-induced silencing complex]). The targeting delivery coefficients of these processes achieved with the model using RBD5044 and the published data of another GalNAc-siRNA (fitusiran) quantitatively reflected the delivery efficiency and rate-limiting factors in targeted hepatocytes.

CONCLUSION

This study successfully constructed the mPBPK-PD model and conducted interspecies extrapolation for a GalNAc-siRNA targeting APOC3. Promising quantitative insights into a hepatic-targeted GalNAc-siRNA delivery system are provided to characterize the unique temporal disconnection of PK/PD properties and evaluate the key in vivo delivery processes. It will promote model-informed strategies and quantitative mechanistic understanding to support efficient drug development, evaluation, and clinical application of this modality in the future.

Preclinical and Clinical Pharmacokinetics of JNJ-75220795, an siRNA Therapeutic Targeting PNPLA3, for Metabolic Dysfunction-Associated Steatohepatitis

JNJ-75220795 or ARO-PNPLA3 is an investigational small interfering ribonucleic acid agent conjugated with N-acetyl-d-galactosamine that targets the PNPLA3 gene, currently being developed for metabolic dysfunction-associated steatohepatitis (MASH). This study evaluated the pharmacokinetics (PK) profile of single subcutaneous doses of JNJ-75220795 in preclinical species as well as in human subjects with homozygous or heterozygous PNPLA3 I148M mutation in two phase 1 studies-a first-in-human study in the United States and a first-in-Japanese study in Japan. Preclinical PK in rats and non-human primates (NHP) showed a rapid systemic absorption and elimination following single subcutaneous doses. JNJ-75220795 was predominantly distributed to the liver with peak liver concentrations reached at 4 h and still detectable at 672 and 336 h in rats and NHPs, respectively, with an apparent liver-to-plasma area under the curve (AUC) ratio of 2800 in rats. Consistent with the preclinical findings, clinical PK showed rapid systemic absorption and clearance in humans with median peak concentrations at 3.0-9.0 h and mean short half-life of 3.4-6.2 h. Plasma PK exposure parameters including Cmax and AUC increased approximately dose proportionally. Kidney had the second highest tissue exposure following the liver in rats. Renal excretion was a significant but minor elimination pathway as approximately 15%-25% of the administered dose was recovered in urine. Based on the overall data, JNJ-75220795 was primarily localized to the liver and exhibited sustained hepatic exposures, which confer prolonged pharmacodynamic effects in the target organ. The favorable PK profiles of single subcutaneous doses observed in the phase 1 studies support continued clinical development of JNJ-75220795 for the treatment of MASH.

Targeted degradation of extracellular proteins: state of the art and diversity of degrader designs

Selective elimination of proteins associated with the pathogenesis of diseases is an emerging therapeutic modality with distinct advantages over traditional inhibitor-based approaches. This strategy, called targeted protein degradation (TPD), is based on hijacking the cellular proteolytic machinery using chimeric degrader molecules that physically link the target protein of interest with the degradation effectors. The TPD era began with the development of PROteolysis TAtrgeting Chimeras (PROTACs) in 2001, with various methods and applications currently available. Classical PROTAC molecules are heterobifunctional chimeras linking target proteins with E3 ubiquitin ligases. This induced interaction leads to the ubiquitylation of the target protein, which is needed for its recognition and subsequent degradation by the cellular proteasomes. However, this technology is limited to intracellular proteins since the effectors involved (E3 ubiquitin ligases and proteasomes) are located in the cytosol. The related methods for selective destruction of proteins present in the extracellular space have only emerged recently and are collectively termed extracellular TPD (eTPD). The prototypic eTPD technology utilizes LYsosomal TArgeting Chimeras (LYTACs) that link extracellular target proteins (secreted or membrane-associated) to lysosome-targeting receptors (LTRs) on the cell surface. The resulting complex is then internalized by endocytosis and trafficked to lysosomes, where the target protein is degraded. The successful elimination of various extracellular proteins via LYTACs and related approaches has been reported, including several important targets in oncology that drive tumor growth and dissemination. This review summarizes current progress in the eTPD field and focuses primarily on the respective technological developments. It discusses the design principles and diversity of degrader molecules and the landscape of available targets and effectors that can be employed for eTPD. Finally, it emphasizes current open questions, challenges, and perspectives of this technological platform to promote the expansion of the eTPD toolkit and further development of its therapeutic applications.

The Fomivirsen, Patisiran, and Givosiran Odyssey: How the Success Stories May Pave the Way for Future Clinical Translation of Nucleic Acid Drugs

Over the past 25 years, the approval of several nucleic acid-based drugs by the US Food and Drug Administration (FDA) has marked a significant milestone, establishing nucleic acid drugs as a viable therapeutic modality. These groundbreaking discoveries are the result of some crucial points in the timeline of nucleic acid drug development. The inventions used in fomivirsen (Vitravene; Isis Pharmaceuticals) development paved the road for structural backbone modifications as well as nucleobase and sugar modifications. The approval of patisiran (Onpattro; Alnylam) demonstrated an effective and safe delivery system for small interfering RNA (siRNA), extending potential applications to other nucleic acids such as messenger RNA (mRNA). Givosiran (Givlaari; Alnylam) further revolutionized the field with a carrier-free, targeted platform, utilizing N-Acetylgalactosamine (GalNAc)-siRNA conjugates to enable efficient delivery, expanding therapeutic applications beyond rare genetic disorders to more common conditions such as hyperlipidemia and hypertension. In this review paper, we highlight the evolution of nucleic acid-based drug development, focusing on the pioneering agents fomivirsen, patisiran, and givosiran, and discuss the ongoing challenges in advancing these therapeutics and vaccines.

GSH-Responsive GalNAc-Conjugated Glycopolymer for Targeted Survivin siRNA Delivery in Hepatocellular Carcinoma Therapy

Gene interference therapy has made significant progress in the treatment of various diseases by targeting specific pathogenic genes and down-regulating the production of harmful proteins. This approach enables the precise modulation of gene expression, offering potential therapeutic benefits for conditions driven by genetic mutations or abnormal protein accumulation. Survivin, an apoptosis-inhibiting protein, plays a critical role in regulating tumor cell proliferation and preventing programmed cell death. Its overexpression in liver cancer cells is strongly associated with poor prognosis and accelerated tumor progression. RNA interference (RNAi) therapy can effectively suppress the expression of Survivin in liver cancer, inhibiting tumor cell proliferation and promoting apoptosis. In this study, four distinct GalNAc-conjugated glycopolymer siRNA delivery systems were developed. By leveraging the efficient liver-targeting capability of the GalNAc moiety, Survivin-siRNA was specifically delivered to liver cancer cells through either covalent coupling or electrostatic adsorption. In vitro experiments demonstrated the excellent gene silencing effect of these siRNA complexes, highlighting their potential as a promising therapeutic strategy for liver cancer.

Cutting-edge biotherapeutics and advanced delivery strategies for the treatment of metabolic dysfunction-associated steatotic liver disease spectrum

Metabolic dysfunction-associated steatotic liver disease (MASLD), a condition with the potential to progress into liver cirrhosis or hepatocellular carcinoma, has become a significant global health concern due to its increasing prevalence alongside obesity and metabolic syndrome. Despite the promise of existing therapies such as thyroid hormone receptor-β (THR-β) agonists, PPAR agonists, FXR agonists, and GLP-1 receptor agonists, their effectiveness is limited by the complexity of the metabolic, inflammatory, and fibrotic pathways that drive MASLD progression, encompassing steatosis, metabolic dysfunction-associated steatohepatitis (MASH), and reversible liver fibrosis. Recent advances in targeted therapeutics, including RNA interference (RNAi), mRNA-based gene therapies, monoclonal antibodies, proteolysis-targeting chimeras (PROTAC), peptide-based strategies, cell-based therapies such as CAR-modified immune cells and stem cells, and extracellular vesicle-based approaches, have emerged as promising interventions. Alongside these developments, innovative drug delivery systems are being actively researched to enhance the stability, precision, and therapeutic efficacy of these biotherapeutics. These delivery strategies aim to optimize biodistribution, improve target-specific action, and reduce systemic exposure, thus addressing critical limitations of existing treatment modalities. This review provides a comprehensive exploration of the underlying biological mechanisms of MASLD and evaluates the potential of these cutting-edge biotherapeutics in synergy with advanced delivery approaches to address unmet clinical needs. By integrating fundamental disease biology with translational advancements, it aims to highlight future directions for the development of effective, targeted treatments for MASLD and its associated complications.

Pharmacokinetics and protein binding of cholesterol-conjugated heteroduplex oligonucleotide

Heteroduplex oligonucleotide (HDO) is a novel oligonucleotide therapeutic consisting of an antisense oligonucleotide (ASO) and its complementary RNA. A recent report showed that cholesterol-conjugated HDO (Chol-HDO) exhibited antisense activity in various tissues, including the brain; however, little information is available on the pharmacokinetic and plasma protein-binding properties of HDO and Chol-HDO. In the present study, we investigated the tissue distributions of an ASO, HDO, and Chol-HDO in mice and rats after intravenous injection. Tissue distribution was evaluated by measuring the concentration of ASO in tissue samples using liquid chromatography and tandem mass spectroscopy. ASO and HDO disappeared rapidly from the plasma, whereas Chol-HDO showed prolonged retention in the systemic circulation. The amount of ASO in the brain tissue was highest after injection of Chol-HDO, confirming its efficient delivery to the brain. The tissue distribution of oligonucleotides differed less in rats than in mice. Hepatic uptake of ASO and HDO, but not of Chol-HDO, was significantly inhibited by co-administration with the scavenger receptor inhibitor dextran sulfate sodium. The binding to plasma proteins was evaluated. Compared to ASO, HDO showed lower protein binding, but Chol-HDO showed much higher binding, with remarkable differences in binding to high-density and low-density lipoproteins. The binding of Chol-HDO to these proteins was also confirmed in mouse plasma after injection. These results indicate that the binding of Chol-HDO to plasma proteins, especially lipoproteins, is critical for determining tissue distribution and brain delivery after intravenous injection.

Receptor-ligand interactions for optimized endocytosis in targeted therapies

Receptor-mediated endocytosis plays a crucial role in the success of numerous therapies and remains central to advancing drug development. This process begins with ligand binding to specific receptors, triggering the internalization and intracellular trafficking of receptor-ligand complexes. These complexes are subsequently directed into distinct routes, either toward lysosomal degradation or recycling to the cell surface, with implications for therapeutic outcomes. This review examines receptor-ligand interactions as key modulators of endocytosis, emphasizing their role in shaping therapeutic design and efficacy. Advances in selecting receptor-ligand pairs and engineering ligands with optimized properties have enabled precise control over internalization, endosomal sorting, and trafficking, providing tailored solutions for diverse therapeutic applications. Leveraging these insights, strategies such as RNA-based therapies, antibody-drug conjugates (ADCs), and targeted protein degradation (TPD) platforms have been refined to selectively avoid or promote lysosomal degradation, thereby enhancing therapeutic efficacy. By bridging fundamental mechanisms of receptor-mediated endocytosis with innovative therapeutic approaches, this review offers a framework for advancing precision medicine.

Recent Update on siRNA Therapeutics

Small interfering RNA (siRNA) has been deemed a promising therapeutic method for treating diverse diseases. siRNA-based therapeutics provide a distinct mechanism of action by selectively targeting and silencing disease-causing genes at the post-transcriptional level. This paper provides an overview of the present state of siRNA-based therapeutics, highlighting their potential in different therapeutic areas. The first section of this review introduces the basic principles of siRNA technology, including its mechanism of action and delivery methods. Subsequently, we discuss the impediments associated with siRNA delivery and manufacturing development and the strategies for overcoming these obstacles. The clinical advancement of siRNA therapeutics in various disease areas, including cancer, genetic disorders, viral infections, and inflammatory diseases, is summarized. Lastly, we summarize the successes, failures, and lessons learned from the development of siRNAs. With advancements in delivery systems and improvements in target selection, the field of medicine can be revolutionized, and siRNA therapeutics can offer new treatment options for patients.

Using aptamers for targeted delivery of RNA therapies

RNA-based treatments that can silence, introduce, or restore gene expression to target human diseases are emerging as a new class of therapeutics. Despite their potential for use in broad applications, their clinical translation has been hampered by a need for delivery to specific cells and tissues. Cell targeting based on the use of aptamers provides an approach for improving their delivery to the desired sites of action. Aptamers are nucleic acid oligonucleotides with structural conformations that provide a robust capacity for the recognition of cell surface molecules and that can be used for directed targeting. Aptamers can be directly conjugated to therapeutic RNA molecules, in the form of aptamer-oligonucleotide chimeras, or incorporated into nanoparticles used as vehicles for the delivery of these therapeutics. Herein, we discuss the use of aptamers for cell-directed RNA therapies, provide an overview of different types of aptamer-targeting RNA therapeutics, and review examples of their therapeutic applications. Challenges associated with manufacturing and scaling up production, and key considerations for their clinical implementation, are also outlined.

Familial chylomicronemia syndrome and treatments to target hepatic APOC3 mRNA

Familial chylomicronemia syndrome (FCS) is a rare, recessive monogenic disorder characterized by severely elevated plasma triglyceride (TG) levels due to absent or markedly impaired lipoprotein lipase activity, leading to a greatly increased risk of acute pancreatitis. Naturally occurring very low levels of apoC-III are associated with low TG levels; thus, apoC-III is a target for TG lowering, and therapies have been developed to reduce apoC-III. Strategies to inhibit hepatic apoC-III synthesis include antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs). In the last decade, technologies have been developed to enhance hepatic delivery of these potential therapeutic agents by conjugation of the ligand triantennary N-acetyl galactosamine to ASO and siRNA for receptor-mediated uptake by hepatocytes, where apoC-III is predominantly expressed. Enhanced delivery of these pharmacological agents to the target tissue has been found to support lower and/or less frequent dosing with consequent lower total systemic exposure. One antisense agent, the ASO olezarsen, is now approved by the US Food and Drug Administration (FDA) as an adjunct to diet to lower triglycerides in adults with FCS, and the other, the siRNA plozasiran, is in late-stage clinical development. Both agents have shown effectiveness in reducing both apoC-III and TG levels across several study populations. Reduced TG, lower rates of acute pancreatitis events, and similar proportions of adverse events in placebo and treated patients were recently demonstrated in placebo-controlled phase 3 trials of patients with FCS treated with olezarsen in Balance and with plozasiran in PALISADE. This review discusses causes and consequences of FCS and the rationale and progress made in developing APOC3 RNA-targeted therapeutics for the treatment of FCS.

RNA-Based Therapies for Neurodegenerative Diseases Targeting Pathogenic Proteins

Neurodegeneration is featured by the gradual stagnation of neuronal function and structure, leading to significant motor and cognitive impairments. The primary histopathological features underlying these conditions include the cumulation of pathological protein aggregates, chronic inflammation, and neuronal cell death. Alzheimer's disease (AD) and Parkinson's disease (PD) are prominent examples of neurodegenerative diseases (NDDs). As of 2023, over 65 million people worldwide are affected by AD and PD, with the prevalence of these conditions steadily increasing over time. Interestingly, there are no effective therapies available to halt or slow NDD progression. Most approved treatments are focused on symptom management and are often associated with substantial side effects. Given these limitations, the development of novel therapeutic approaches targeting the molecular mechanisms underlying these disorders is essential. Notably, RNA-based therapeutics have recently emerged as a potential therapeutic approach for managing various neurological diseases, offering the potential for innovative molecular interventions in NDD. In this review, we have discussed the pathogenic role of various protein aggregates in NDD and highlighted emerging RNA-based strategies aimed at targeting these pathological proteins.

GalNac-siRNA conjugate delivery technology promotes the treatment of typical chronic liver diseases

INTRODUCTION

Nucleic acid-based therapeutics have become a key pillar of the 'third wave' of modern medicine, following the eras of small molecule inhibitors and antibody drugs. Their rapid progress is heavily dependent on delivery technologies, with the development of N-acetylgalactosamine (GalNAc) conjugates marking a breakthrough in targeting liver diseases. This technology has gained significant attention for its role in addressing chronic conditions like chronic hepatitis B (CHB) and nonalcoholic steatohepatitis (NASH), which are challenging to treat with conventional methods.

AREAS COVERED

This review explores the origins, mechanisms, and advantages of GalNAc-siRNA delivery systems, highlighting their ability to target hepatocytes via the asialoglycoprotein receptor (ASGPR). The literature reviewed covers preclinical and clinical advancements, particularly in CHB and NASH. Key developments in stabilization chemistry and conjugation technologies are examined, emphasizing their impact on enhancing therapeutic efficacy and patient compliance.

EXPERT OPINION

GalNAc-siRNA technology represents a transformative advancement in RNA interference (RNAi) therapies, addressing unmet needs in liver-targeted diseases. While significant progress has been made, challenges remain, including restricted targeting scope and scalability concerns. Continued innovation is expected to expand applications, improve delivery efficiency, and overcome limitations, establishing GalNAc-siRNA as a cornerstone for future nucleic acid-based treatments.

The efficacy and safety of RNA interference for the treatment of primary hyperoxaluria: a systematic review and meta-analysis

Primary hyperoxaluria (PH) are rare inherited disorders of liver glyoxylate metabolism. The main symptoms are related to the precipitation of calcium oxalate crystals in the urinary tract with progressive renal damage. The severity of disease can result in kidney failure and systemic oxalosis. Until recently, RNA interference (RNAi) has been demonstrated as a therapeutic avenue for PH. We conducted a systematic review and meta-analysis to assessed the efficacy and safety of RNAi in the treatment of PH patients. The present systemic review systematically and comprehensively summarizes the pathophysiological mechanisms by which hyperoxalemia leads to kidney failure. Furthermore, we provide a detailed summary of the mechanisms of RNAi drug action in the pharmacological treatment of PH. The enrolled studies indicated that early RNAi intervention is beneficial for patients, especially in maintaining stable kidney function and reversing the effects of hyperoxaluria. Furthermore, high-dose and long time-duration RNAi therapy may have a better clinical effect. The efficacy of RNAi combined with hemodialysis seems to be promising, and it deserves more well-designed trials with large sample sizes in the future. RNAi therapy plays an important role in the treatment of PH. Early RNAi intervention is beneficial for patients, especially in maintaining stable kidney function and reversing the effects of hyperoxaluria. Furthermore, high-dose and long time-duration RNAi therapy may have a better clinical effect, and acceptable safety. The efficacy of RNAi combined with hemodialysis seems to be promising in PH treatment.

Enhancing hemostasis potency in hemophilia with a small interfering ribonucleic acid targeting protein S

BACKGROUND

One hemophilia treatment concept focuses on rebalancing coagulation and anticoagulation to restore normal blood clotting. Targeting the coagulation regulator, protein S (PS), in hemophilia shows promise to increase the generation of thrombin, a critical enzyme in the clotting process.

OBJECTIVES

This study aimed to: (1) assess whether inhibiting PS increases thrombin generation (TG) in plasma from individuals with hemophilia A (HA) and B (HB); and (2) develop a hepatocyte-targeted PS small interfering RNA (siRNA) therapy using N-acetylgalactosamine conjugation to restore hemostasis in hemophilia without increasing thromboembolic risks.

METHODS

We assessed TG in plasma from patients with HA and HB. To target the liver specifically, we developed a PS-siRNA conjugated with N-acetylgalactosamine. This approach ensures that PS levels remain adequate in other cells, thereby minimizing the risk of thrombosis. Additionally, we evaluated the therapeutic potential of PS-siRNA in preclinical models.

RESULTS

Inhibiting PS with a polyclonal antibody in plasma resulted in a 3- to 5-fold increase in TG in HA and a 4- to 9-fold increase in HB plasma, with a 70% reduction in plasma PS. In preclinical models, subcutaneous PS-siRNA therapy in HA mice and nonhuman primates successfully lowered PS levels and improved clot formation. It also prevented bleeding in both saphenous vein puncture and knee injury models in HA mice. Notably, it enhanced clotting without triggering widespread clot formation.

CONCLUSION

Reducing PS levels enhances TG in hemophilia models, and PS-siRNA therapy shows promise in improving hemostasis. This approach warrants further clinical investigation as a potential treatment for hemophilia.

Direct Cytosolic Delivery of siRNA Conjugates: A Paradigm in Antiangiogenic Therapy for Choroidal Neovascularization

Small interfering RNA (siRNA) has garnered tremendous interest as a potential therapeutic tool because of its intriguing gene-silencing ability. Toward the success in the manufacture of siRNA therapeutics for the potential treatment of choroidal neovascularization (CNV), siRNA conjugated with dual functional units of membrane-penetrating heptafluoropropyl and age-related macular degeneration-targeting cyclic Arg-Gly-Asp (RGD) peptide was attempted for transcellular transportation into the cell interiors. Of note, cyclic RGD allowed selective affinities toward the angiogenic endothelial cells in the pathological CNV. Noteworthy is the functional heptafluoropropyl group, due to its tempting lipophobic and hydrophobic properties, stimulating energy-independent transcellular trafficking behaviors to the cytoplasm directly from the extracellular compartments, namely, the nonendocytotic pathway. The behaviors manage to avoid the well-acknowledged drawback of endolysosomal entrapment, which is deemed to be the critical threat to the biovulnerable genomic therapeutics, thereby contributing to potent gene knockdown at the affected cells. Aiming for treatment of CNV, the siRNA duo was schemed with appropriate chemistry-based modifications for the targeted knockdown of both angiogenic VEGF-A and VEGF-R2. Subsequent investigations verified the potent reduction of vascular leakage, and our proposed siRNA duo accomplished a significant reduction of 67.3% in the mean area of the CNV lesion. Bioinformatic analysis has unveiled a multitude of therapeutic benefits conferred by anti-VEGF therapy, extending beyond the mere inhibition of angiogenesis, including the regulated leukocyte transendothelial migration, retinol metabolism, and estrogen signaling pathways. Hence, our proposed chemistry represents an interesting siRNA conjugate strategy accomplishing direct intracellular transportation of macromolecular biological payloads to the cytosol. Hence, this proposed fluorination strategy should be highlighted to encourage the development of appropriate prodrug chemistry in pursuit of transcellular trafficking of membrane-impermissible and biovulnerable biotherapeutics.

The Interplay of Endosomal Escape and RNA Release from Polymeric Nanoparticles

Ribonucleic acid (RNA) nanocarriers, specifically lipid nanoparticles and polymeric nanoparticles, enable RNA transfection both in vitro and in vivo; however, only a small percentage of RNA endocytosed by a cell is delivered to the cytosolic machinery, minimizing its effect. RNA nanocarriers face two major obstacles after endocytosis: endosomal escape and RNA release. Overcoming both obstacles simultaneously is challenging because endosomal escape is usually achieved by using high positive charge to disrupt the endosomal membrane. However, this high positive charge typically also inhibits RNA release because anionic RNA is strongly bound to the nanocarrier by electrostatic interactions. Many nanocarriers address one over the other despite a growing body of evidence demonstrating that both are crucial for RNA transfection. In this review, we survey the various strategies that have been employed to accomplish both endosomal escape and RNA release with a focus on polymeric nanomaterials. We first consider the various requirements a nanocarrier must achieve for RNA delivery including protection from degradation, cellular internalization, endosomal escape, and RNA release. We then discuss current polymers used for RNA delivery and examine the strategies for achieving both endosomal escape and RNA release. Finally, we review various stimuli-responsive strategies for RNA release. While RNA release continues to be a challenge in achieving efficient RNA transfection, many new innovations in polymeric materials have elucidated promising strategies.

Modulation of TTR Gene Expression in the Eye using Modified Duplex RNAs

Small interfering RNAs (siRNAs) are a proven therapeutic approach for controlling gene expression in the liver. Expanding the clinical potential of RNA interference (RNAi) requires developing strategies to enhance delivery to extra-hepatic tissues. In this study we examine inhibiting transthyretin (TRR) gene expression by short interfering RNAs (siRNAs) in the eye. Anti-TTR siRNAs have been developed as successful drugs to treat TTR amyloidosis. When administered systemically, anti-TTR siRNAs alleviate symptoms by blocking TTR expression in the liver. However, TTR amyloidosis also affects the eye, suggesting a need for reducing ocular TTR gene expression. Here, we demonstrate that C5 and 2'-O-linked lipid-modified siRNAs formulated in saline can inhibit TTR expression in the eye when administered locally by intravitreal (IVT) injection. Modeling suggests that length and accessibility of the lipid chains contributes to in vivo silencing. GalNAc modified anti-dsRNAs also inhibit TTR expression, albeit less potently. These data support lipid modified siRNAs as an approach to treating the ocular consequences of TTR amyloidosis. Inhibition of TTR expression throughout the eye demonstrates that lipid-siRNA conjugates have the potential to be a versatile platform for ocular drug discovery.

RNA Therapies in Cardio-Kidney-Metabolic Syndrome: Advancing Disease Management

Cardio-Kidney-Metabolic (CKM) Syndrome involves metabolic, kidney, and cardiovascular dysfunction, disproportionately affecting disadvantaged groups. Its staging (0-4) highlights the importance of early intervention. While current management targets hypertension, heart failure, dyslipidemia, and diabetes, RNA-based therapies offer innovative solutions by addressing molecular mechanisms of CKM Syndrome. Emerging RNA treatments, including antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs), show promise in slowing disease progression across CKM stages. For example, ASOs and siRNAs targeting ApoC-III and ANGPTL3 reduce triglycerides and LDL cholesterol, while siRNAs improve blood pressure control by targeting the renin-angiotensin-aldosterone system. Obesity treatments leveraging miRNAs and circRNAs tackle a key CKM risk factor. In heart failure and diabetes, RNA-based therapies improve cardiac function and glucose control, while early kidney disease trials show potential for RNAi in acute injury. Further research is essential to refine these therapies and ensure equitable access.

Development of novel nucleic acid therapy aimed at directly controlling liver fibrosis

Currently, no drugs directly treat liver fibrosis. Previously, we have shown that treatment with miR-29a-3p improved liver fibrosis in a mouse model. To investigate the effectiveness of nucleic acid therapy at a lower dose, a modified nucleic acid was prepared based on miR-29a-3p. The original microRNA was changed to an RNA-DNA hybrid structure: the 2' position of the RNA was modified with a fluorine base, and locked nucleic acid and phosphorothioate were crosslinked (hereafter called modified nucleic acid). In a mouse model of chronic liver disease treated with carbon tetrachloride (CCl4), the inhibitory effect on liver fibrosis was evaluated with oral administration of the modified nucleic acid. The modified nucleic acid was detected in the liver and gastrointestinal tract within 15 min of oral administration. After 5 weeks of stimulation with CCl4, oral administration of the modified nucleic acid for 2 weeks improved liver fibrosis; CCl4 stimulation was continued during this period as well. This treatment also suppressed the worsening of liver fibrosis. We developed a method to improve liver fibrosis orally using nuclease-resistant nucleic acids without using a drug delivery system. This method may be used as a new treatment for inhibiting the progression of liver fibrosis.

Nucleic acid therapeutics: Past, present, and future

Nucleic acid therapeutics have become increasingly recognized in recent years for their capability to target both coding and non-coding sequences. Several types of nucleic acid modalities, including siRNA, mRNA, aptamer, along with antisense oligo, have been approved by regulatory bodies for therapeutic use. The field of nucleic acid therapeutics has been brought to the forefront by the rapid development of vaccines against COVID-19, followed by a number of approvals for clinical use including much anticipated CRISPR-Cas9. However, obstacles such as the difficulty of achieving efficient and targeted delivery to diseased sites remain. This review provides an overview of nucleic acid therapeutics and highlights substantial advancements, including critical engineering, conjugation, and delivery strategies, that are paving the way for their growing role in modern medicine.

Emerging, novel gene-modulating therapies for transthyretin amyloid cardiomyopathy

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive, life-threatening disease caused by the pathological deposition of misfolded transthyretin (TTR) protein in the myocardium, leading to restrictive cardiomyopathy and heart failure. While TTR stabilizers such as tafamidis and acoramidis are the only FDA-approved treatments, novel gene-modulating therapies are emerging as transformative approaches. Small interfering RNA (siRNA) and antisense oligonucleotide (ASO) therapies effectively reduce TTR production and have demonstrated promising clinical outcomes, though their use in cardiac amyloidosis remains investigational. CRISPR-Cas9 therapies represent a paradigm shift, offering a potential one-time treatment by permanently silencing the TTR gene. Recent clinical trials have shown significant TTR reduction and stabilization of disease biomarkers, although long-term safety and efficacy require further evaluation. Despite the lack of direct comparisons among these modalities, their emergence highlights a promising future for ATTR-CM management. This review discusses the pathogenesis of ATTR-CM, mechanisms of novel gene-modulating therapies, clinical evidence, challenges, and the future outlook for advancing treatment options.

Engineering Lipid Nanoparticles for mRNA Immunotherapy

Over the last decades, messenger RNA (mRNA) has emerged as a promising therapeutic modality, enabling the delivery of genetic instructions to cells for producing therapeutic proteins or antigens. As such, mRNA-based therapies can be developed for a wide range of conditions, including infections, cancer, metabolic disorders, and genetic diseases. Nevertheless, using mRNA therapeutically requires chemical modifications to reduce immunostimulatory effects and nanotechnology to prevent degradation and ensure intracellular delivery. Lipid nanoparticles (LNPs) have become the most effective delivery platform for mRNA therapeutics, which are primarily employed for vaccine purposes following local administration and hepatic applications following systemic administration. Here, we review the state-of-the-art LNP-mRNA technology and discuss its potential for immunotherapy. We first outline the requirements for mRNA to be used therapeutically, including the role of LNP-mediated delivery. Next, we highlight LNP-mRNA immunotherapy approaches for vaccination, immuno-oncology, and autoimmune disorders. In addition, we discuss challenges that are limiting LNP-mRNA's widespread use, including tunable biodistribution and immunostimulatory effects. Finally, we provide an outlook on how implementing approaches such as library screening and machine learning will guide the development of next-generation mRNA therapeutics.

Haemophilia

Haemophilia A and B are congenital X-linked bleeding disorders resulting from deficiencies in clotting factors VIII (haemophilia A) and IX (haemophilia B). Patients with severe deficiency, defined as having less than 1% of normal plasma factor activivity, often have spontaneous bleeding within the first few years of life. Those with moderate and mild deficiencies typically present with post-traumatic or post-surgical bleeding later in life. A high index of suspicion and measurement of factor activity in plasma facilitates early diagnosis. In the 21st century, therapeutic advances and comprehensive care have substantially improved both mortality and morbidity associated with these conditions. Management strategies for haemophilia include on-demand treatment for bleeding episodes and all surgeries and regular treatment (ie, prophylaxis) aimed at reducing bleeds, morbidity, and mortality, thereby enhancing quality of life. Treatment options include factor replacement therapy, non-replacement therapies that increase thrombin generation, and gene therapies that facilitate in vivo clotting factor synthesis. The therapies differ in their use for prophylaxis and on-demand treatment, the mode and frequency of administration, duration of treatment effect, degree of haemostatic protection, and side-effects. Monitoring the effectiveness of these prophylactic therapies involves assessing annual bleeding rates and joint damage. Personalised management strategies, which align treatment with individual goals (eg, playing competitive sports), initiated at diagnosis and maintained throughout the lifespan, are crucial for optimal outcomes. These strategies are facilitated by a multidisciplinary team and supported by clinician-led education for both clinicians and patients.

Expanding Conjugate Space of RNAi Therapeutics: Ligand at the 3' End of the Antisense Strand Achieves Uncompromised In Vivo Potency and Efficacy and Reveals Interactions with the Argonaute-2 PAZ Domain

The conjugation of the sense strands of small interfering RNA (siRNA) to tri-N-acetylgalactosamine (GalNAc), the ligand for a hepatocyte-specific receptor, enables the delivery of multiple clinically approved therapeutic agents that act through the RNA interference pathway. Here, we report the systematic evaluation of siRNAs with the 3' termini of antisense strands conjugated to GalNAc for the first time. These designs retained the same receptor affinity, in vitro and in vivo activities, as well as the same level of loading into the RNA-induced silencing complex as siRNAs with a GalNAc-conjugated sense strand. A siRNA with a GalNAc-conjugated antisense strand of 22 nucleotides had better activity than a siRNA with a 23-nucleotide antisense strand. Computational modeling of a complex of a GalNAc-conjugated antisense strand with the PAZ domain of Ago2 rationalizes the importance of the interaction of phosphate at the 3' terminus with the PAZ domain to explain the observed activity of these siRNAs.

Preclinical testing of antiviral siRNA therapeutics delivered in lipid nanoparticles in animal models - a comprehensive review

The advent of RNA interference (RNAi) technology through the use of short-interfering RNAs (siRNAs) represents a paradigm shift in the fight against viral infections. siRNAs, with their ability to directly target and silence specific posttranscriptional genes, offer a novel mechanism of action distinct from that of traditional pharmacotherapeutics. This review delves into the growing field of siRNA therapeutics against viral infections, highlighting their critical role in contemporary antiviral strategies. Importantly, this review will solely focus on the use of lipid nanoparticles (LNPs) as the ideal antiviral siRNA delivery agent for use in vivo. We discuss the challenges of siRNA delivery and how LNPs have emerged as a pivotal solution to enhance antiviral efficacy. Specifically, this review focuses on work that have preclinically tested LNP formulated siRNA on virus infection animal models. Since the COVID-19 pandemic, we have witnessed a resurgence in the field of RNA-based therapies, including siRNAs against viruses including, SARS-CoV-2. Notably, the critical importance of LNPs as the ideal carrier for precious 'RNA cargo' can no longer be ignored with the advent of mRNA-LNP based COVID-19 vaccines. siRNA-based therapeutics represents an emerging class of anti-infective drugs with a foreseeable future as suitable antiviral agents.

Effect of pH-Responsive Ligands on mRNA Knockdown in EGFR-Targeting Ligand-Conjugated siRNAs

Ligand-conjugated small interfering RNAs (siRNAs) have emerged as a powerful approach to developing nucleic acid-based medicines. To achieve efficient mRNA knockdown, it is important to select targeting receptors with high expression and ligands that exhibit rapid internalization. However, the key characteristics of ligand-receptor sets involved in the postinternalization process remain largely unclear. In this study, we investigated the effect of ligand-receptor binding dissociation under low pH conditions, known as a postendocytic environment. Specifically, we chemically synthesized several modified epidermal growth factor (EGF) ligands that showed a variety of binding activities to the EGF receptor (EGFR) at low pH. Among these modified ligands, the siRNA conjugate with chemically synthesized EGF H10Y/H16Y, which is a less pH-responsive variant, exhibited reduced internalization and mRNA knockdown activity at high concentrations in EGFR-expressing cells. Additionally, we explored the use of antibody-related molecules (anti-EGFR IgG and Fab) as targeting moieties for siRNA conjugates. The anti-EGFR Fab-siRNA, which showed dissociation of EGF under low pH conditions, demonstrated stronger internalization and mRNA knockdown activity compared to the anti-EGFR IgG-siRNA, which strongly binds EGF at low pH. These data emphasize the importance of intracellular ligand-receptor dissociation and provide insights for future advancements in the field.

Lipid-siRNA Conjugates Targeting High PD-L1 Expression as Potential Novel Immune Checkpoint Inhibitors

Programmed death 1 ligand (PD-L1), an important immune checkpoint molecule, is mainly expressed on cancer cells and has been shown to exert an immunosuppressive effect on T-cell function by binding to programmed cell death 1 (PD-1) expressed on T-cells. Recently, immune checkpoint inhibitors using antibody drugs such as nivolumab and atezolizumab have attracted attention. However, clinical challenges, including limitations to the scope of their application, are yet to be addressed. In this study, we developed a novel immune checkpoint inhibitor that targets PD-L1 using lipid-siRNA conjugates (lipid-siPDL1s). The inhibitory effect of lipid-siPDL1s on PD-L1 expression was evaluated and found to strongly suppress mRNA expression. Notably, lipid-siPDL1s exerted a significantly stronger effect than unmodified siPDL1. Interestingly, lipid-siPDL1s strongly inhibited PD-L1 expression despite cancer cell stimulation by interferon-gamma, which induced the overexpression of PD-L1 genes. These results strongly suggest that lipid-siPDL1s could be used as novel immune checkpoint inhibitors.

Self-Assembly and Biological Properties of Highly Fluorinated Oligonucleotide Amphiphiles

Nucleic acids, used as therapeutics to silence disease-related genes, offer significant advantages over small molecule drugs: they provide high specificity, the ability to target "undruggable" molecules, and adaptability to a wide range of disease phenotypes. However, their instability in biological media, as well their rapid clearance from the organism limit their applicability, necessitating the use of nanocarriers to overcome these challenges. Among these strategies, spherical nucleic acids (SNA)-composed of a densely packed corona of oligonucleotides around a nanoparticle-have emerged as a powerful tool, in particular when self-assembled from DNA amphiphiles. This non-covalent strategy however has caveats, especially when it comes to stability in complex biological media, where these SNAs disassemble in contact to serum proteins. Here, we developed highly fluorinated DNA amphiphiles that readily self-assemble into SNAs and have tunable stability profiles in biological media. They are made of branched fluorinated moieties with potentially improved biodegradability as compared to their linear counterparts. Depending on the number of fluorophilic interactions, the self-assembled SNAs can have excellent serum stabilities-up to days-and readily deliver nucleic acid therapeutics for gene silencing applications. These systems show great potential as promising candidates for nucleic acid-based therapies.

Advancing hypertension management: the role of zilebesiran as an siRNA therapeutic agent

Elevated blood pressure poses a significant global health challenge, affecting over 1.28 billion adults worldwide, with a staggering 46% unaware of their condition. Despite its pervasive impact and association with cardiovascular disease, hypertension remains inadequately controlled, highlighting the urgent need for innovative treatment approaches. This review explores the potential of small interfering RNA (siRNA) therapeutics, focusing on zilebesiran, as a promising strategy for hypertension management. SiRNA therapy represents a groundbreaking approach to selectively modulate protein production, offering targeted intervention in the pathophysiological mechanisms underlying hypertension. Zilebesiran, a siRNA, targets hepatic angiotensinogen (AGT) synthesis through interaction with the asialoglycoprotein receptor, ultimately reducing angiotensin II levels and reducing blood pressure. Zilebesiran demonstrates remarkable pharmacokinetic properties, with sustained efficacy observed after single-dose administration. Clinical trials evaluating zilebesiran have shown significant reductions in blood pressure, with effects lasting up to 24 weeks post-administration. Moreover, combination therapy with angiotensin receptor blockers has demonstrated enhanced efficacy, highlighting the potential for synergistic effects in hypertension management. Importantly, zilebesiran exhibits a favorable safety profile, with manageable adverse events, primarily injection site reactions. Zilebesiran represents a transformative therapy in hypertension management, offering targeted and potent blood pressure reduction with favorable safety and dosing characteristics. Its emergence highlights the ongoing evolution of cardiovascular pharmacology and underscores the importance of innovative approaches to address the global burden of hypertension. Moving forward, concerted efforts in research and clinical practice are necessary to realize the benefits of zilebesiran into hypertension management protocols, ultimately advancing cardiovascular health worldwide.

Photochemical Stabilization of Self-Assembled Spherical Nucleic Acids

Oligonucleotide therapeutics, including antisense oligonucleotides and small interfering RNA, offer promising avenues for modulating the expression of disease-associated proteins. However, challenges such as nuclease degradation, poor cellular uptake, and unspecific targeting hinder their application. To overcome these obstacles, spherical nucleic acids have emerged as versatile tools for nucleic acid delivery in biomedical applications. Our laboratory has introduced sequence-defined DNA amphiphiles which self-assemble in aqueous solutions. Despite their advantages, self-assembled SNAs can be inherently fragile due to their reliance on non-covalent interactions and fall apart in biologically relevant conditions, specifically by interaction with serum proteins. Herein, this challenge is addressed by introducing two methods of covalent crosslinking of SNAs via UV irradiation. Thymine photodimerization or disulfide crosslinking at the micellar interface enhance SNA stability against human serum albumin binding. This enhanced stability, particularly for disulfide crosslinked SNAs, leads to increased cellular uptake. Furthermore, this crosslinking results in sustained activity and accessibility for release of the therapeutic nucleic acid, along with improvement in unaided gene silencing. The findings demonstrate the efficient stabilization of SNAs through UV crosslinking, influencing their cellular uptake, therapeutic release, and ultimately, gene silencing activity. These studies offer promising avenues for further optimization and exploration of pre-clinical, in vivo studies.

Roadmap to discovery and early development of an mRNA loaded LNP formulation for liver therapeutic genome editing

INTRODUCTION

mRNA therapeutics were a niche area in drug development before COVID vaccines. They are now used in vaccine development, for non-viral therapeutic genome editing, in vivo chimeric antigen receptor T (CAR T) cell therapies and protein replacement.  mRNA is large, charged, and easily degraded by nucleases. It cannot get into cells, escape the endosome, and be translated to a disease-modifying protein without a delivery system such as lipid nanoparticles (LNPs).

AREAS COVERED

This article covers how to design, select, and develop an LNP for therapeutic genome editing in the liver. The roadmap is divided into selecting the right LNP for discovery via a design, make, test, and analyze cycle (DMTA). The design elements are focused on ionizable lipids in a 4-component LNP, and insights are provided for how to set an in vitro and in vivo testing strategy. The second section focuses on transforming the LNP into a clinical drug product and covers formulation, analytical development, and process optimization, with brief notes on supply and regulator strategies.

EXPERT OPINION

The perspective discusses the impact that academic-industry collaborations can have on developing new medicines for therapeutic genome editing in the liver. From the cited collaborations an enhanced understanding of intracellular trafficking, notably endosomal escape, and the internal structure of LNPs were attained and are deemed key to designing effective and safe LNPs. The knowledge gained will also enable additional assays and structural activity relationships, which would lead to the design of the next-generation delivery systems for nucleic acid therapies.

A journey into siRNA therapeutics development: A focus on Pharmacokinetics and Pharmacodynamics

siRNA therapeutics are emerging novel modalities targeting highly specific mRNA via RNA interference mechanism. Its unique pharmacokinetics (PKs) and pharmacodynamics (PDs) are significant challenges for clinical use. Furthermore, naked siRNA is a highly soluble macromolecule with a negative charge, making plasma membrane penetration a significant hurdle. It is also vulnerable to nuclease degradation. Therefore, advanced formulation technologies, such as lipid nanoparticles and N-acetylgalactosamine conjugation, have been developed and are now used in clinical practice to enhance target organ delivery and stability. The innate complex biological mechanisms of siRNA, along with its formulation, are major determinants of the PK/PD characteristics of siRNA products. To systematically and quantitatively understand these characteristics, it is essential to develop and utilize quantitative PK/PD models for siRNA therapeutics. In this review, the effects of formulation on the PKs and PK/PD models of approved siRNA products were presented, highlighting the importance of selecting appropriate biomarkers and understanding formulation, PKs, and PDs for quantitative interpreting the relationship between plasma concentration, organ concentration, biomarkers, and efficacy.

Four-component protein nanocages designed by programmed symmetry breaking

Four, eight or twenty C3 symmetric protein trimers can be arranged with tetrahedral, octahedral or icosahedral point group symmetry to generate closed cage-like structures1,2. Viruses access more complex higher triangulation number icosahedral architectures by breaking perfect point group symmetry3-9, but nature appears not to have explored similar symmetry breaking for tetrahedral or octahedral symmetries. Here we describe a general design strategy for building higher triangulation number architectures starting from regular polyhedra through pseudosymmetrization of trimeric building blocks. Electron microscopy confirms the structures of T = 4 cages with 48 (tetrahedral), 96 (octahedral) and 240 (icosahedral) subunits, each with 4 distinct chains and 6 different protein-protein interfaces, and diameters of 33 nm, 43 nm and 75 nm, respectively. Higher triangulation number viruses possess very sophisticated functionalities; our general route to higher triangulation number nanocages should similarly enable a next generation of multiple antigen-displaying vaccine candidates10,11 and targeted delivery vehicles12,13.

PCSK9 in metabolism and diseases

PCSK9 is a serine protease that regulates plasma levels of low-density lipoprotein (LDL) and cholesterol by mediating the endolysosomal degradation of LDL receptor (LDLR) in the liver. When PCSK9 functions unchecked, it leads to increased degradation of LDLR, resulting in elevated circulatory levels of LDL and cholesterol. This dysregulation contributes to lipid and cholesterol metabolism abnormalities, foam cell formation, and the development of various diseases, including cardiovascular disease (CVD), viral infections, cancer, and sepsis. Emerging clinical and experimental evidence highlights an imperative role for PCSK9 in metabolic anomalies such as hypercholesterolemia and hyperlipidemia, as well as inflammation, and disturbances in mitochondrial homeostasis. Moreover, metabolic hormones - including insulin, glucagon, adipokines, natriuretic peptides, and sex steroids - regulate the expression and circulatory levels of PCSK9, thus influencing cardiovascular and metabolic functions. In this comprehensive review, we aim to elucidate the regulatory role of PCSK9 in lipid and cholesterol metabolism, pathophysiology of diseases such as CVD, infections, cancer, and sepsis, as well as its pharmaceutical and non-pharmaceutical targeting for therapeutic management of these conditions.

Protein Arginine Methyltransferase 1: A Multi-Purpose Player in the Development of Cancer and Metabolic Disease

Protein arginine methyltransferase 1 (PRMT1) is the main PRMT family member involved in the formation of monomethylarginine and asymmetric dimethylarginine on its protein substrates. Many protein substrates of PRMT1 are key mediators of cell proliferation and oncogenesis. As such, the function of PRMT1 has been most prominently investigated in the context of cancer development. However, recent in vitro and in vivo studies have highlighted that PRMT1 may also promote metabolic disorders. With the current review, we aim to present an in-depth overview of how PRMT1 influences epigenetic modulation, transcriptional regulation, DNA damage repair, and signal transduction in cancer. Furthermore, we summarize the current knowledge regarding the role of PRMT1 in metabolic reprogramming, lipid metabolism, and glucose metabolism and describe the association of PRMT1 with numerous metabolic pathologies such as obesity, liver disease, and type 2 diabetes. It has become apparent that inhibiting the function of PRMT1 will likely serve as the most beneficial therapeutic approach, since several PRMT1 inhibitors have already been shown to exert positive effects on both cancer and metabolic disease in preclinical settings. However, pharmacological PRMT1 inhibition has not yet been shown to be therapeutically effective in clinical studies.

Lipid nanoparticle delivery of siRNA to dorsal root ganglion neurons to treat pain

Sensory neurons within the dorsal root ganglion (DRG) are the primary trigger of pain, relaying activity about noxious stimuli from the periphery to the central nervous system; however, targeting DRG neurons for pain management has remained a clinical challenge. Here, we demonstrate the use of lipid nanoparticles (LNPs) for effective intrathecal delivery of small interfering RNA (siRNA) to DRG neurons, achieving potent silencing of the transient receptor potential vanilloid 1 (TRPV1) ion channel that is predominantly expressed in nociceptor sensory neurons. This leads to a reversible interruption of heat-, capsaicin-, and inflammation-induced nociceptive conduction, as observed by behavioral outputs. Our work provides a proof-of-concept for intrathecal siRNA therapy as a novel and selective analgesic modality.

State of the art and perspectives of gene therapy in heart failure. A scientific statement of the Heart Failure Association of the ESC, the ESC Council on Cardiovascular Genomics and the ESC Working Group on Myocardial & Pericardial Diseases

Gene therapy has recently become a reality in the treatment of cardiovascular diseases. Strategies to modulate gene expression using antisense oligonucleotides or small interfering RNA are proving to be safe and effective in the clinic. Adeno-associated viral vector-based gene delivery and CRISPR-Cas9-based genome editing have emerged as efficient strategies for gene delivery and repair in humans. Overall, gene therapy holds the promise not only of expanding current treatment options, but also of intervening in previously untackled causal disease mechanisms with little side effects. This scientific statement provides a comprehensive overview of the various modalities of gene therapy used to treat heart failure and some of its risk factors, and their application in the clinical setting. It discusses specifically the possibilities of gene therapy for hereditary heart diseases and (non)-genetic heart failure. Furthermore, it addresses safety and clinical trial design issues and challenges for future regulatory strategies.

Investigational RNA Interference Agents for Hepatitis B

Functional cure of chronic hepatitis B (CHB)-defined as sustained seroclearance of hepatitis B surface antigen (HBsAg) with unquantifiable hepatitis B virus (HBV) DNA at 24 weeks off treatment, is an optimal treatment endpoint. Nonetheless, it cannot be consistently attained by current treatment modalities. RNA interference (RNAi) is a novel treatment strategy using small-interfering RNA (siRNA) or antisense oligonucleotide (ASO) to target HBV post-transcriptional RNA, in turn suppressing viral protein production and replication. Hence, RNAi has indirect effects in promoting host immune reconstitution against HBV. Multiple RNAi therapeutics have entered phase II/III clinical trials, demonstrating potent, dose-dependent, and sustainable effects in suppressing HBsAg. Incidences of HBsAg seroclearance, particularly with the use of ASO, have also been documented. The combination of RNAi with other antivirals/immunomodulators (e.g. pegylated interferon), have shown promising results in potentiating RNAi effects and enhancing treatment durability. Further research will be required to establish predictors of response, optimal treatment protocols, and long-term outcomes in patients on RNAi. RNAi therapeutics have shown promising results and will likely be the keystone of future HBV treatment.

RNA Structure: Past, Future, and Gene Therapy Applications

First believed to be a simple intermediary between the information encoded in deoxyribonucleic acid and that functionally displayed in proteins, ribonucleic acid (RNA) is now known to have many functions through its abundance and intricate, ubiquitous, diverse, and dynamic structure. About 70-90% of the human genome is transcribed into protein-coding and noncoding RNAs as main determinants along with regulatory sequences of cellular to populational biological diversity. From the nucleotide sequence or primary structure, through Watson-Crick pairing self-folding or secondary structure, to compaction via longer distance Watson-Crick and non-Watson-Crick interactions or tertiary structure, and interactions with RNA or other biopolymers or quaternary structure, or with metabolites and biomolecules or quinary structure, RNA structure plays a critical role in RNA's lifecycle from transcription to decay and many cellular processes. In contrast to the success of 3-dimensional protein structure prediction using AlphaFold, RNA tertiary and beyond structures prediction remains challenging. However, approaches involving machine learning and artificial intelligence, sequencing of RNA and its modifications, and structural analyses at the single-cell and intact tissue levels, among others, provide an optimistic outlook for the continued development and refinement of RNA-based applications. Here, we highlight those in gene therapy.

Exploratory Studies on RNAi-Based Therapies Targeting Angiotensinogen in Hypertension: Scoping Review

Background: Systemic arterial hypertension contributes to cardiovascular morbidity and mortality worldwide. Many patients cannot achieve optimal blood pressure (BP) control with traditional therapies, which often results in poor patient adherence and limited long-term efficacy. We investigated the potential of RNA interference (RNAi) therapies targeting hepatic angiotensinogen (AGT) for hypertension management. Methods: This scoping review was conducted by the Joanna Briggs Institute, following a six-stage methodological framework and adhering to PRISMA recommendations. A comprehensive search was conducted across seven databases to identify relevant studies published until May 2024. Data extraction was performed separately, and both quantitative and qualitative analyses were conducted. A population, concept, and context model-based search was performed, selecting controlled MeSH terms and uncontrolled descriptors and cross-referencing them using Booleans. Results: Fifteen articles met our inclusion criteria. Focusing on the efficacy and safety of RNAi-based therapies, this review discusses several key approaches, including antisense oligonucleotides (IONIS-AGT-LRx), small interfering RNA (siRNAs; zilebesiran), and adeno-associated viruses carrying short hairpin RNAs. Notably, zilebesiran conjugated with N-acetylgalactosamine significantly reduced systolic BP by 20 mmHg, sustained for up to six months post-administration, with minimal adverse effects. Conclusions: RNAi-based therapies, particularly those using siRNAs, such as zilebesiran, are promising for the treatment of hypertension. They offer long-term BP control with fewer doses, potentially improving patient adherence and outcome. Although these therapies address several limitations of current antihypertensive treatments, further studies are required to confirm their long-term safety and efficacy.

Advances in conjugate drug delivery System: Opportunities and challenges

Ideal drug delivery system is designed to accurately deliver the drug to its intended site. The development of conjugate drug delivery system introduces a novel pathway to precise drug delivery with advantages over traditional methods. The core of a conjugate drug delivery system comprises a molecule with two functional components, bounded by a linker structure. One component is responsible for delivering or stabilizing the conjugate, while the other is used to provide the therapeutic or diagnostic effects of the bioactivity. Conjugate drug delivery system improves patient health by maintaining the structural stability of drugs in molecular form, delivering therapeutics or diagnostic material to the target site, minimising off-target accumulation and promoting patient compliance. This system includes various types of drug conjugates that modulate drug pharmacokinetics, stability, absorption, and exposure in lesions and healthy tissues. In this review, we focus on the key characteristics and recent advances of various conjugate drug delivery systems and explore their mechanisms. We also point out the current challenges faced by conjugate drug delivery system and look forward to the future prospects.

Protocol to generate, purify, and analyze antibody-oligonucleotide conjugates from off-the-shelf antibodies

Antibody-oligonucleotide conjugates (AOCs) are a fast-expanding modality for targeted delivery of therapeutic oligonucleotides to tissues. Here, we present a protocol to generate, purify, and analyze AOCs from off-the-shelf antibodies. We describe steps to conjugate single/double-stranded oligonucleotides bearing amine handles to linkers and, then, to antibodies using well-established chemistry. In addition, we provide details regarding the purification techniques and analytical methods suitable for AOC. This protocol can be applied for several purposes where AOC is a modality of interest. For complete details on the use and execution of this protocol, please refer to Rady et al.1.

Polysaccharide-Based Coacervate Microgel Bearing Cationic Peptides That Achieve Dynamic Cell-Membrane Structure Alteration and Facile Cytosolic Infusion of IgGs

Conjugates of the biocompatible polysaccharide pullulan with a cell membrane permeabilizing peptide L17E (PL-L17Es) were prepared with the aim of producing complex coacervates with pronounced intracellular antibody (IgG) delivery activity and stable structures. Coacervates with diameters of a few μm were formed simply by mixing PL-L17Es with IgG labeled with negatively charged fluorescent moieties of Alexa Fluor 488 [IgG(AF488)]. The coacervate resulted in a pronounced cytosolic infusion of IgG(AF488) and IgG binding to the target proteins inside the cell. The droplet structures were maintained even under high salt conditions, and the fluorescence in the droplet was not recovered after photobleaching, suggesting the formation of complex coacervate microgels. Dynamic changes in cell membrane structure to entrap the coacervate microgels were captured by confocal and electron microscopy, resulting in cytosolic IgG infusion. The use of M-lycotoxin instead of L17E resulted in a coacervate microgel with marked IgG delivery activity even in the presence of serum. Successful IgG delivery to primary hepatocytes, undifferentiated induced pluripotent stem (iPS) cells, and iPS cell-derived intestinal epithelial cells was also achieved. The construction of complex coacervate microgels with design flexibility and the validity of intracellular IgG delivery with high salt stability were thus demonstrated.

Zerlasiran-A Small-Interfering RNA Targeting Lipoprotein(a): A Phase 2 Randomized Clinical Trial

Importance

Elevated lipoprotein(a) increases the risk of atherosclerotic cardiovascular disease (ASCVD) and aortic stenosis.

Objective

To evaluate the effects of zerlasiran, a small-interfering RNA targeting hepatic synthesis of apolipoprotein(a), on lipoprotein(a) serum concentration.

Design, Setting, and Participants

A multicenter trial in patients with stable ASCVD with serum lipoprotein(a) concentrations greater than or equal to 125 nmol/L at 26 sites in Europe and South Africa between January 3, 2023, and April 27, 2023, with last follow-up on July 1, 2024.

Interventions

Participants randomized to receive a subcutaneous dose of placebo every 16 weeks for 3 doses (n = 23) or every 24 weeks for 2 doses (n = 24) or zerlasiran 450 mg every 24 weeks for 2 doses (n = 45), 300 mg every 16 weeks for 3 doses (n = 42), or 300 mg every 24 weeks for 2 doses (n = 44).

Main Outcome and Measures

The primary outcome was the time-averaged percent change in lipoprotein(a) concentration from baseline to 36 weeks, with follow-up to 60 weeks.

Results

Among 178 patients, mean (SD) age was 63.7 (9.4) years, 46 (25.8%) were female, with a median (IQR) baseline lipoprotein(a) concentration of 213 (177-282) nmol/L; 172 patients completed the trial. Compared with the pooled placebo group, the least-squares mean time-averaged percent change in lipoprotein(a) concentration from baseline to week 36 was -85.6% (95% CI, -90.9% to -80.3%), -82.8% (95% CI, -88.2% to -77.4%), and -81.3% (95% CI, -86.7% to -76.0%) for the 450 mg every 24 weeks, 300 mg every 16 weeks, and 300 mg every 24 weeks groups, respectively. Median (IQR) percent change in lipoprotein(a) concentration at week 36 was -94.5% (-97.3% to -84.2%) for the 450 mg every 24 weeks group, -96.4% (-97.7% to -92.3%) for the 300 mg every 16 weeks group, and -90.0% (-93.7% to -81.3%) for the 300 mg every 24 weeks group. The most common treatment-related adverse effects were injection site reactions, with mild pain occurring in 2.3% to 7.1% of participants in the first day following drug administration. There were 20 serious adverse events in 17 patients, none considered related to the study drug.

Conclusions

Zerlasiran was well-tolerated and reduced time-averaged lipoprotein(a) concentration by more than 80% during 36 weeks of treatment in patients with ASCVD.

Trial Registration

ClinicalTrials.gov Identifier: NCT05537571.