Antibody-oligonucleotide conjugate achieves CNS delivery in animal models for spinal muscular atrophy

Drug delivery strategies to cross the blood-brain barrier in Alzheimer's disease: a comprehensive review on three promising strategies

The field of Alzheimer's disease (AD) drug development is rapidly changing, with two anti-amyloid monoclonal antibodies (mAbs) having received Food and Drug Administration (FDA) approval, additionally many compounds are in the pipeline. A major obstacle for novel AD therapeutics is the blood-brain barrier (BBB), which restricts passage of particles larger than 400-500 Da. It is estimated that only ∼1 % of mAbs, being ∼150 kDa, passes the BBB, which greatly hampers the efficacy of treatment. To enhance treatment efficacy and to lower the drug dose needed, mechanisms that effectively increase drug delivery across the BBB are urgently sought for. This narrative review describes three promising strategies to enhance drug delivery across the BBB in AD: focused ultrasound (FUS) with microbubbles, receptor-mediated transcytosis (RMT) and delivery using nanoparticle carrier systems. FUS and RMT have shown promising preclinical results and are now being tested in humans whereas nanoparticle carrier systems still need further preclinical validation before clinical application in humans. 89Zr-Immuno-PET provides a unique opportunity to noninvasively monitor and quantitatively assess novel brain delivery methods.

Unlocking the future: Precision oligonucleotide therapy for targeted treatment of neurodegenerative disorders

Neurodegenerative disorders are complex and devastating conditions of the central nervous system that profoundly impact quality of life. Given the limited treatment options available, there is a pressing need to develop novel therapeutic strategies. Oligonucleotides have emerged as key players in precision medicine for these disorders, but their potential is hindered by poor translocation across the blood-brain barrier. This review focuses on neurodegenerative disorders other than Alzheimer's and Parkinson's, which are widely reported in the literature, and aims to address the significant hurdles in oligonucleotide delivery for neurodegenerative diseases. It highlights recent advancements in CNS-targeting approaches, such as chemical conjugation, antibody-oligonucleotide conjugates, focused ultrasound, and viral and nanocarrier-based delivery systems. Each strategy's strengths and limitations are discussed, with potential solutions proposed for more effective treatments. Additionally, the review offers valuable insights into regulatory requirements and prospects for clinical translation, which are crucial for shaping the future of neurodegenerative therapies. By exploring these innovative approaches, the goal is to surmount challenges posed by the blood-brain barrier and develop more effective treatments, thereby enhancing the quality of life of the patients suffering from these debilitating conditions.

The Endo-GeneScreen Platform Identifies Drug-Like Probes that Regulate Endogenous Protein Levels within Physiological Contexts

Traditional phenotypic drug discovery platforms have suffered from poor scalability and a lack of mechanistic understanding of newly discovered phenotypic probes. To address this, we created Endo- GeneScreen (EGS), a high-throughput enabled screening platform that identifies bioactive small molecules capable of regulating endogenous protein expression encoded by any preselected target gene within a biologically appropriate context. As a proof-of-concept, EGS successfully identified drug candidates that up-regulate endogenous expression of neuronal Syngap1, a gene that causes a neurodevelopmental disorder when haploinsufficient. For example, SR-1815, a previously unknown and undescribed kinase inhibitor, alleviated major cellular consequences of Syngap1 loss-of-function by restoring normal SynGAP protein levels and dampening neuronal hyperactivity within haploinsufficient neurons. Moreover, we demonstrate that EGS assays accelerate preclinical development of identified drug candidates and facilitate mode-of-action deconvolution studies. Thus, EGS identifies first-in-class bioactive small molecule probes that promote biological discovery and precision therapeutic development.

A review of RNA nanoparticles for drug/gene/protein delivery in advanced therapies: Current state and future prospects

Nanotechnology involves the utilization of materials with exceptional properties at the nanoscale. Over the past few years, nanotechnologies have demonstrated significant potential in improving human health, particularly in medical treatments. The self-assembly characteristic of RNA is a highly effective method for designing and constructing nanostructures using a combination of biological, chemical, and physical techniques from different fields. There is great potential for the application of RNA nanotechnology in therapeutics. This review explores various nano-based drug delivery systems and their unique features through the impressive progress of the RNA field and their significant therapeutic promises due to their unique performance in the COVID-19 pandemic. However, a significant hurdle in fully harnessing the power of RNA drugs lies in effectively delivering RNA to precise organs and tissues, a critical factor for achieving therapeutic effectiveness, minimizing side effects, and optimizing treatment outcomes. There have been many efforts to pursue targeting, but the clinical translation of RNA drugs has been hindered by the lack of clear guidelines and shared understanding. A comprehensive understanding of various principles is essential to develop vaccines using nucleic acids and nanomedicine successfully. These include mechanisms of immune responses, functions of nucleic acids, nanotechnology, and vaccinations. Regarding this matter, the aim of this review is to revisit the fundamental principles of the immune system's function, vaccination, nanotechnology, and drug delivery in relation to the creation and manufacturing of vaccines utilizing nanotechnology and nucleic acids. RNA drugs have demonstrated significant potential in treating a wide range of diseases in both clinical and preclinical research. One of the reasons is their capacity to regulate gene expression and manage protein production efficiently. Different methods, like modifying chemicals, connecting ligands, and utilizing nanotechnology, have been essential in enabling the effective use of RNA-based treatments in medical environments. The article reviews stimuli-responsive nanotechnologies for RNA delivery and their potential in RNA medicines. It emphasizes the notable benefits of these technologies in improving the effectiveness of RNA and targeting specific cells and organs. This review offers a comprehensive analysis of different RNA drugs and how they work to produce therapeutic benefits. Recent progress in using RNA-based drugs, especially mRNA treatments, has shown that targeted delivery methods work well in medical treatments.

Nucleic Acid Conjugates: Unlocking Therapeutic Potential

Nucleic acids have emerged as a powerful class of therapeutics. Through simple base pair complementarity, nucleic acids allow the targeting of a variety of pathologically relevant proteins and RNA molecules. However, despite the preliminary successes of nucleic acids as drugs in the clinic, limited biodistribution, inadequate delivery mechanisms, and target engagement remain key challenges in the field. A key area of research has been the chemical optimization of nucleic acid backbones to significantly enhance their "drug-like" properties. Alternatively, this review focuses on the next generation of nucleic acid chemical modifications: covalent biochemical conjugates. These conjugates are being applied to improve the delivery, functionality, and targeting. Exploiting research on heterobifunctionals, such as PROTACs, RIBOTACs, molecular glues, etc., has the potential to dramatically expand nucleic acid drug functionality and target engagement capabilities. Such next-generation chemistry-based enhancements have the potential to unlock nucleic acids as effective and versatile therapeutic agents.

Evolution of antisense oligonucleotides: navigating nucleic acid chemistry and delivery challenges

INTRODUCTION

Antisense oligonucleotide (ASO) was established as a viable therapeutic option for genetic disorders. ASOs can target RNAs implicated in various diseases, including upregulated mRNA and pre-mRNA undergoing abnormal alternative splicing events. Therapeutic applications of ASOs have been proven with the Food and Drug Administration approval of several drugs in recent years. Earlier enzymatic stability and delivery remains a big challenge for ASOs. Introducing new chemical modifications and new formulations resolving the issues related to the nuclease stability and delivery of the ASOs. Excitingly, ASOs-based bioconjugates that target the hepatocyte have gained much attraction. Efforts are ongoing to increase the therapeutic application of the ASOs to the extrahepatic tissue as well.

AREA COVERED

We have briefly discussed the mechanism of ASOs, the development of new chemistries, and delivery strategies for ASO-based drug discovery and development. The discussion focuses more on the already approved ASOs and those in the clinical development stage.

EXPERT OPINION

To expand the clinical application of ASOs, continuous effort is required to develop precise delivery strategies for targeting extrahepatic tissue to minimize the off-target effects.

Leveraging plant-derived nanovesicles for advanced nucleic acid-based gene therapy

Gene therapy has evolved into a pivotal approach for treating genetic disorders, extending beyond traditional methods of directly repairing or replacing defective genes. Recent advancements in nucleic acid-based therapies-including mRNA, miRNA, siRNA, and DNA treatments have expanded the scope of gene therapy to include strategies that modulate protein expression and deliver functional genetic material without altering the genetic sequence itself. This review focuses on the innovative use of plant-derived nanovesicles (PDNVs) as a promising delivery system for these nucleic acids. PDNVs not only enhance the stability and bioavailability of therapeutic nucleic acids but also improve their specificity and efficacy in targeted gene therapy applications. They have shown potential in the treatment of various diseases, including cancer and inflammatory conditions. By examining the unique properties of PDNVs and their role in overcoming the limitations of conventional delivery methods, this review highlights the transformative potential of PDNV-based nucleic acid therapies in advancing the field of gene therapy.

Constructions, Purifications and Applications of DNA-Antibody Conjugates: A Review

A DNA-antibody conjugate is a synthetic molecule that combines the unique functions of both an antibody and DNA. With the increased accessibility of commercialized kits, the procedure for constructing conjugates is simplified and the requirement for chemistry background is reduced. As a result, the difficulty of preparing a DNA-antibody conjugate has been significantly lowered. Therefore, the application of DNA-antibody conjugates has attracted more interest in recent years. The most common application of DNA-antibody conjugates is based on the amplifiable property of DNA through PCR. This includes single-conjugate-based immuno-PCR, paired-conjugates-based proximity ligation assay, and proximity extension assay. These methods achieve highly sensitive or specific detection of target proteins. The conjugated single stranded DNA molecules can also specifically hybridize with another strand containing its complementary sequence. This property can be used to selectively bind fluorophore labeled DNA strands, which plays an important role in tissue imaging and spatial omics. All these factors make DNA-antibody conjugates have a broad range of applications in research, diagnosis, and potentially therapy.

Overcoming limitations and advancing the therapeutic potential of antibody-oligonucleotide conjugates (AOCs): Current status and future perspectives

As cancer incidence rises due to an aging population, the importance of precision medicine continues to grow. Antibody-drug conjugates (ADCs) exemplify targeted therapies by delivering cytotoxic agents to specific antigens. Building on this concept, researchers have developed antibody-oligonucleotide conjugates (AOCs), which combine antibodies with oligonucleotides to regulate gene expression. This review highlights the mechanism of AOCs, emphasizing their unique ability to selectively target and modulate disease-causing proteins. It also explores the components of AOCs and their application in tumor therapy while addressing key challenges such as manufacturing complexities, endosomal escape, and immune response. The article underscores the significance of AOCs in precision oncology and discusses future directions, highlighting their potential in treating cancers driven by genetic mutations and abnormal protein expression.

Peptide-Oligonucleotide Conjugation: Chemistry and Therapeutic Applications

Oligonucleotides have been identified as powerful therapeutics for treating genetic disorders and diseases related to epigenetic factors such as metabolic and immunological dysfunctions. However, they face certain obstacles in terms of limited delivery to tissues and poor cellular uptake due to their large size and often highly charged nature. Peptide-oligonucleotide conjugation is an extensively utilized approach for addressing the challenges associated with oligonucleotide-based therapeutics by improving their delivery, cellular uptake and bioavailability, consequently enhancing their overall therapeutic efficiency. In this review, we present an overview of the conjugation of oligonucleotides to peptides, covering the different strategies associated with the synthesis of peptide-oligonucleotide conjugates (POC), the commonly used peptides employed to generate POCs, with the aim to develop oligonucleotides with favourable pharmacokinetic (PK) or pharmacodynamic (PD) properties for therapeutic applications. The advantages and drawbacks of the synthetic methods and applications of POCs are also described.

Targeting the transferrin receptor to transport antisense oligonucleotides across the mammalian blood-brain barrier

Antisense oligonucleotides (ASOs) are promising therapeutics for treating various neurological disorders. However, ASOs are unable to readily cross the mammalian blood-brain barrier (BBB) and therefore need to be delivered intrathecally to the central nervous system (CNS). Here, we engineered a human transferrin receptor 1 (TfR1) binding molecule, the oligonucleotide transport vehicle (OTV), to transport a tool ASO across the BBB in human TfR knockin (TfRmu/hu KI) mice and nonhuman primates. Intravenous injection and systemic delivery of OTV to TfRmu/hu KI mice resulted in sustained knockdown of the ASO target RNA, Malat1, across multiple mouse CNS regions and cell types, including endothelial cells, neurons, astrocytes, microglia, and oligodendrocytes. In addition, systemic delivery of OTV enabled Malat1 RNA knockdown in mouse quadriceps and cardiac muscles, which are difficult to target with oligonucleotides alone. Systemically delivered OTV enabled a more uniform ASO biodistribution profile in the CNS of TfRmu/hu KI mice and greater knockdown of Malat1 RNA compared with a bivalent, high-affinity TfR antibody. In cynomolgus macaques, an OTV directed against MALAT1 displayed robust ASO delivery to the primate CNS and enabled more uniform biodistribution and RNA target knockdown compared with intrathecal dosing of the same unconjugated ASO. Our data support systemically delivered OTV as a potential platform for delivering therapeutic ASOs across the BBB.

Targeting and engineering long non-coding RNAs for cancer therapy

RNA therapeutics (RNATx) aim to treat diseases, including cancer, by targeting or employing RNA molecules for therapeutic purposes. Amongst the most promising targets are long non-coding RNAs (lncRNAs), which regulate oncogenic molecular networks in a cell type-restricted manner. lncRNAs are distinct from protein-coding genes in important ways that increase their therapeutic potential yet also present hurdles to conventional clinical development. Advances in genome editing, oligonucleotide chemistry, multi-omics and RNA engineering are paving the way for efficient and cost-effective lncRNA-focused drug discovery pipelines. In this Review, we present the emerging field of lncRNA therapeutics for oncology, with emphasis on the unique strengths and challenges of lncRNAs within the broader RNATx framework. We outline the necessary steps for lncRNA therapeutics to deliver effective, durable, tolerable and personalized treatments for cancer.

Precision targeting in oncology: The future of conjugated drugs

Coupled drugs, especially antibody-coupled drugs (ADCs), are a hot topic in oncology. As the development of ADCs has progressed, different coupling modes have emerged, inspired by their structural design have emerged. Technological advances have led to interweaving and collision of old and new concepts of coupled drugs, and have even challenged the concepts and techniques of coupled drugs at this stage. For example, antibody-oligonucleotide conjugates are a new class of chimeric biomolecules synthesized by coupling oligonucleotides with monoclonal antibodies through linkers, offering precise targeting and improved pharmacokinetic properties. This study aimed to elucidate the mechanism of action of coupled drugs and their current development status in antitumor therapy to provide better strategies for antitumor therapy.

An AAV capsid reprogrammed to bind human transferrin receptor mediates brain-wide gene delivery

Developing vehicles that efficiently deliver genes throughout the human central nervous system (CNS) will broaden the range of treatable genetic diseases. We engineered an adeno-associated virus (AAV) capsid, BI-hTFR1, that binds human transferrin receptor (TfR1), a protein expressed on the blood-brain barrier. BI-hTFR1 was actively transported across human brain endothelial cells and, relative to AAV9, provided 40 to 50 times greater reporter expression in the CNS of human TFRC knockin mice. The enhanced tropism was CNS-specific and absent in wild-type mice. When used to deliver GBA1, mutations of which cause Gaucher disease and are linked to Parkinson's disease, BI-hTFR1 substantially increased brain and cerebrospinal fluid glucocerebrosidase activity compared with AAV9. These findings establish BI-hTFR1 as a potential vector for human CNS gene therapy.

Efficient systemic CNS delivery of a therapeutic antisense oligonucleotide with a blood-brain barrier-penetrating ApoE-derived peptide

Antisense oligonucleotide (ASO) has emerged as a promising therapeutic approach for treating central nervous system (CNS) disorders by modulating gene expression with high selectivity and specificity. However, the poor permeability of ASO across the blood-brain barrier (BBB) diminishes its therapeutic success. Here, we designed and synthesized a series of BBB-penetrating peptides (BPP) derived from either the receptor-binding domain of apolipoprotein E (ApoE) or a transferrin receptor-binding peptide (THR). The BPPs were conjugated to phosphorodiamidate morpholino oligomers (PMO) that are chemically analogous to the 2'-O-(2-methoxyethyl) (MOE)-modified ASO approved by the FDA for treating spinal muscular atrophy (SMA). The BPP-PMO conjugates significantly increased the level of full-length SMN2 in the patient-derived SMA fibroblasts in a concentration-dependent manner with minimal to no toxicity. Furthermore, the systemic administration of the most potent BPP-PMO conjugates significantly increased the expression of full-length SMN2 in the brain and spinal cord of SMN2 transgenic adult mice. Notably, BPP8-PMO conjugate showed a 1.25-fold increase in the expression of full-length functional SMN2 in the brain. Fluorescence imaging studies confirmed that 78% of the fluorescently (Cy7)-labelled BPP8-PMO reached brain parenchyma, with 11% uptake in neuronal cells. Additionally, the BPP-PMO conjugates containing retro-inverso (RI) D-BPPs were found to possess extended half-lives compared to their L-counterparts, indicating increased stability against protease degradation while preserving the bioactivity. This delivery platform based on BPP enhances the CNS bioavailability of PMO targeting the SMN2 gene, paving the way for the development of systemically administered neurotherapeutics for CNS disorders.

Nucleic Acid Therapeutics: Successes, Milestones, and Upcoming Innovation

Nucleic acid-based therapies have become the third major drug class after small molecules and antibodies. The role of nucleic acid-based therapies has been strengthened by recent regulatory approvals and tremendous clinical success. In this review, we look at the major obstacles that have hindered the field, the historical milestones that have been achieved, and what is yet to be resolved and anticipated soon. This review provides a view of the key innovations that are expanding nucleic acid capabilities, setting the stage for the future of nucleic acid therapeutics.

Niche-specific control of tissue function by regulatory T cells-Current challenges and perspectives for targeting metabolic disease

Tissue regulatory T cells (Tregs) exert pivotal functions in both immune and metabolic regulation, maintaining local tissue homeostasis, integrity, and function. Accordingly, Tregs play a crucial role in controlling obesity-induced inflammation and supporting efficient muscle function and repair. Depending on the tissue context, Tregs are characterized by unique transcriptomes, growth, and survival factors and T cell receptor (TCR) repertoires. This functional specialization offers the potential to selectively target context-specific Treg populations, tailoring therapeutic strategies to specific niches, thereby minimizing potential side effects. Here, we discuss challenges and perspectives for niche-specific Treg targeting, which holds promise for highly efficient and precise medical interventions to combat metabolic disease.

An AAV capsid reprogrammed to bind human Transferrin Receptor mediates brain-wide gene delivery

Developing vehicles that efficiently deliver genes throughout the human central nervous system (CNS) will broaden the range of treatable genetic diseases. We engineered an AAV capsid, BI-hTFR1, that binds human Transferrin Receptor (TfR1), a protein expressed on the blood-brain barrier (BBB). BI-hTFR1 was actively transported across a human brain endothelial cell layer and, relative to AAV9, provided 40-50 times greater reporter expression in the CNS of human TFRC knock-in mice. The enhanced tropism was CNS-specific and absent in wild type mice. When used to deliver GBA1, mutations of which cause Gaucher disease and are linked to Parkinson's disease, BI-hTFR1 substantially increased brain and cerebrospinal fluid glucocerebrosidase activity compared to AAV9. These findings establish BI-hTFR1 as a promising vector for human CNS gene therapy.

Protein-based delivery systems for RNA delivery

RNA-based therapeutics have emerged as promising approaches to modulate gene expression and generate therapeutic proteins or antigens capable of inducing immune responses to treat a variety of diseases, such as infectious diseases, cancers, immunologic disorders, and genetic disorders. However, the efficient delivery of RNA molecules into cells poses significant challenges due to their large molecular weight, negative charge, and susceptibility to degradation by RNase enzymes. To overcome these obstacles, viral and non-viral vectors have been developed, including lipid nanoparticles, viral vectors, proteins, dendritic macromolecules, among others. Among these carriers, protein-based delivery systems have garnered considerable attention due to their potential to address specific issues associated with nanoparticle-based systems, such as liver accumulation and immunogenicity. This review provides an overview of currently marketed RNA drugs, underscores the significance of RNA delivery vector development, delineates the essential characteristics of an ideal RNA delivery vector, and introduces existing protein carriers for RNA delivery. By offering valuable insights, this review aims to serve as a reference for the future development of protein-based delivery vectors for RNA therapeutics.

Peptide Conjugates of a 2'-O-Methoxyethyl Phosphorothioate Splice-Switching Oligonucleotide Show Increased Entrapment in Endosomes

Antisense oligonucleotides (ASOs) are short, single-stranded nucleic acid molecules that alter gene expression. However, their transport into appropriate cellular compartments is a limiting factor in their potency. Here, we synthesized splice-switching oligonucleotides (SSOs) previously developed to treat the rare disease erythropoietic protoporphyria. Using chemical ligation-quantitative polymerase chain reaction (CL-qPCR), we quantified the SSOs in cells and subcellular compartments following free uptake. To drive nuclear localization, we covalently conjugated nuclear localization signal (NLS) peptides to a lead 2'-O-methoxyethyl phosphorothioate SSO using thiol-maleimide chemistry. The conjugates and parent SSO displayed similar RNA target-binding affinities. CL-qPCR quantification of the conjugates in cells and subcellular compartments following free uptake revealed one conjugate with better nuclear accumulation relative to the parent SSO. However, compared to the parent SSO, which altered the splicing of the target pre-mRNA, the conjugates were inactive at splice correction under free uptake conditions in vitro. Splice-switching activity could be conferred on the conjugates by delivering them into cells via cationic lipid-mediated transfection or by treating the cells into which the conjugates had been freely taken up with chloroquine, an endosome-disrupting agent. Our results identify the major barrier to the activity of the peptide-oligonucleotide conjugates as endosomal entrapment.

RNAi therapies: Expanding applications for extrahepatic diseases and overcoming delivery challenges

The era of RNA medicine has become a reality with the success of messenger RNA (mRNA) vaccines against COVID-19 and the approval of several RNA interference (RNAi) agents in recent years. Particularly, therapeutics based on RNAi offer the promise of targeting intractable and previously undruggable disease genes. Recent advances have focused in developing delivery systems to enhance the poor cellular uptake and insufficient pharmacokinetic properties of RNAi therapeutics and thereby improve its efficacy and safety. However, such approach has been mainly achieved via lipid nanoparticles (LNPs) or chemical conjugation with N-Acetylgalactosamine (GalNAc), thus current RNAi therapy has been limited to liver diseases, most likely to encounter liver-targeting limitations. Hence, there is a huge unmet medical need for intense evolution of RNAi therapeutics delivery systems to target extrahepatic tissues and ultimately extend their indications for treating various intractable diseases. In this review, challenges of delivering RNAi therapeutics to tumors and major organs are discussed, as well as their transition to clinical trials. This review also highlights innovative and promising preclinical RNAi-based delivery platforms for the treatment of extrahepatic diseases.

Toxicologic Neuropathology of Novel Biotherapeutics

Biotherapeutic modalities such as cell therapies, gene therapies, nucleic acids, and proteins are increasingly investigated as disease-modifying treatments for severe and life-threatening neurodegenerative disorders. Such diverse bio-derived test articles are fraught with unique and often unpredictable biological consequences, while guidance regarding nonclinical experimental design, neuropathology evaluation, and interpretation is often limited. This paper summarizes key messages offered during a half-day continuing education course on toxicologic neuropathology of neuro-targeted biotherapeutics. Topics included fundamental neurobiology concepts, pharmacology, frequent toxicological findings, and their interpretation including adversity decisions. Covered biotherapeutic classes included cell therapies, gene editing and gene therapy vectors, nucleic acids, and proteins. If agents are administered directly into the central nervous system, initial screening using hematoxylin and eosin (H&E)-stained sections of currently recommended neural organs (brain [7 levels], spinal cord [3 levels], and sciatic nerve) may need to expand to include other components (e.g., more brain levels, ganglia, and/or additional nerves) and/or special neurohistological procedures to characterize possible neural effects (e.g., cell type-specific markers for reactive glial cells). Scientists who evaluate the safety of novel biologics will find this paper to be a practical reference for preclinical safety testing and risk assessment.

Therapeutic Oligonucleotides: An Outlook on Chemical Strategies to Improve Endosomal Trafficking

The potential of oligonucleotide therapeutics is undeniable as more than 15 drugs have been approved to treat various diseases in the liver, central nervous system (CNS), and muscles. However, achieving effective delivery of oligonucleotide therapeutics to specific tissues still remains a major challenge, limiting their widespread use. Chemical modifications play a crucial role to overcome biological barriers to enable efficient oligonucleotide delivery to the tissues/cells of interest. They provide oligonucleotide metabolic stability and confer favourable pharmacokinetic/pharmacodynamic properties. This review focuses on the various chemical approaches implicated in mitigating the delivery problem of oligonucleotides and their limitations. It highlights the importance of linkers in designing oligonucleotide conjugates and discusses their potential role in escaping the endosomal barrier, a bottleneck in the development of oligonucleotide therapeutics.

Nucleic acid-based therapeutics for the treatment of central nervous system disorders

Nucleic acid-based therapeutics (NBTs) are an emerging class of drugs with potential for the treatment of a wide range of central nervous system conditions. To date, pertaining to CNS indications, there are two commercially available NBTs and a large number of ongoing clinical trials. However, these NBTs are applied directly to the brain due to very low blood brain barrier permeability. In this review, we outline recent advances in chemical modifications of NBTs and NBT delivery techniques intended to promote brain exposure, efficacy, and possible future systemic application.

Long non-coding RNA-targeting therapeutics: discovery and development update

INTRODUCTION

lncRNAs are major players in regulatory networks orchestrating multiple cellular functions, such as 3D chromosomal interactions, epigenetic modifications, gene expression and others. Due to progress in the development of nucleic acid-based therapeutics, lncRNAs potentially represent easily accessible therapeutic targets.

AREAS COVERED

Currently, significant efforts are directed at studies that can tap the enormous therapeutic potential of lncRNAs. This review describes recent developments in this field, particularly focusing on clinical applications.

EXPERT OPINION

Extensive druggable target range of lncRNA combined with high specificity and accelerated development process of nucleic acid-based therapeutics open new prospects for treatment in areas of extreme unmet medical need, such as genetic diseases, aggressive cancers, protein deficiencies, and subsets of common diseases caused by known mutations. Although currently wide acceptance of lncRNA-targeting nucleic acid-based therapeutics is impeded by the need for parenteral or direct-to-CNS administration, development of less invasive techniques and orally available/BBB-penetrant nucleic acid-based therapeutics is showing early successes. Recently, mRNA-based COVID-19 vaccines have demonstrated clinical safety of all aspects of nucleic acid-based therapeutic technology, including multiple chemical modifications of nucleic acids and nanoparticle delivery. These trends position lncRNA-targeting drugs as significant players in the future of drug development, especially in the area of personalized medicine.

Amplifying gene expression with RNA-targeted therapeutics

Many diseases are caused by insufficient expression of mutated genes and would benefit from increased expression of the corresponding protein. However, in drug development, it has been historically easier to develop drugs with inhibitory or antagonistic effects. Protein replacement and gene therapy can achieve the goal of increased protein expression but have limitations. Recent discoveries of the extensive regulatory networks formed by non-coding RNAs offer alternative targets and strategies to amplify the production of a specific protein. In addition to RNA-targeting small molecules, new nucleic acid-based therapeutic modalities that allow highly specific modulation of RNA-based regulatory networks are being developed. Such approaches can directly target the stability of mRNAs or modulate non-coding RNA-mediated regulation of transcription and translation. This Review highlights emerging RNA-targeted therapeutics for gene activation, focusing on opportunities and challenges for translation to the clinic.

Peptide-Based Nanoparticles for Systemic Extrahepatic Delivery of Therapeutic Nucleotides

Peptide-based nanoparticles (PBN) for nucleotide complexation and targeting of extrahepatic diseases are gaining recognition as potent pharmaceutical vehicles for fine-tuned control of protein production (up- and/or down-regulation) and for gene delivery. Herein, we review the principles and mechanisms underpinning self-assembled formation of PBN, cellular uptake, endosomal release, and delivery to extrahepatic disease sites after systemic administration. Selected examples of PBN that have demonstrated recent proof of concept in disease models in vivo are summarized to offer the reader a comparative view of the field and the possibilities for clinical application.

Preclinical Screening of Splice-Switching Antisense Oligonucleotides in PDAC Organoids

Aberrant alternative splicing is emerging as a cancer hallmark and a potential therapeutic target. It is the result of dysregulated splicing factors or genetic alterations in splicing-regulatory cis -elements. Targeting individual altered splicing events associated with cancer-cell dependencies is a potential therapeutic strategy, but several technical limitations need to be addressed. Patient-derived organoids (PDOs) are a promising platform to recapitulate key aspects of disease states and to facilitate drug development for precision medicine. Here, we report an efficient antisense-oligonucleotide (ASO) transfection method to systematically evaluate and screen individual splicing events as therapeutic targets in pancreatic ductal adenocarcinoma (PDAC) organoids. This optimized delivery method allows fast and efficient screening of ASOs that reverse oncogenic alternative splicing. In combination with advancements in chemical modifications and ASO-delivery strategies, this method has the potential to accelerate the discovery of anti-tumor ASO drugs that target pathological alternative splicing.