mRNA transfection of dendritic cells: synergistic effect of ARCA mRNA capping with Poly(A) chains in cis and in trans for a high protein expression level

Recent progress in mRNA cancer vaccines

The research and development of messenger RNA (mRNA) cancer vaccines have gradually overcome numerous challenges through the application of personalized cancer antigens, structural optimization of mRNA, and the development of alternative RNA-based vectors and efficient targeted delivery vectors. Clinical trials are currently underway for various cancer vaccines that encode tumor-associated antigens (TAAs), tumor-specific antigens (TSAs), or immunomodulators. In this paper, we summarize the optimization of mRNA and the emergence of RNA-based expression vectors in cancer vaccines. We begin by reviewing the advancement and utilization of state-of-the-art targeted lipid nanoparticles (LNPs), followed by presenting the primary classifications and clinical applications of mRNA cancer vaccines. Collectively, mRNA vaccines are emerging as a central focus in cancer immunotherapy, offering the potential to address multiple challenges in cancer treatment, either as standalone therapies or in combination with current cancer treatments.

Immunoinformatic based designing of potential immunogenic novel mRNA and peptide-based prophylactic vaccines against H5N1 and H7N9 avian influenza viruses

Influenza viruses are the most common cause of serious respiratory illnesses worldwide and are responsible for a significant number of annual fatalities. Therefore, it is crucial to look for new immunogenic sites that might trigger an effective immune response. In the present study, bioinformatics tools were used to design mRNA and multiepitope-based vaccines against H5N1 and H7N9 subtypes of avian influenza viruses. Several Immunoinformatic tools were employed to extrapolate T and B lymphocyte epitopes of HA and NA proteins of both subtypes. The molecular docking approach was used to dock the selected HTL and CTL epitopes with the corresponding MHC molecules. Eight (8) CTL, four (4) HTL, and Six (6) linear B cell epitopes were chosen for the structural arrangement of mRNA and of peptide-based prophylactic vaccine designs. Different physicochemical characteristics of the selected epitopes fitted with suitable linkers were analyzed. High antigenic, non-toxic, and non-allergenic features of the designed vaccines were noted at a neutral physiological pH. Codon optimization tool was used to check the GC content and CAI value of constructed MEVC-Flu vaccine, which were recorded to be 50.42% and 0.97 respectively. the GC content and CAI value verify the stable expression of vaccine in pET28a + vector. In-silico immunological simulation the MEVC-Flu vaccine construct revealed a high level of immune responses. The molecular dynamics simulation and docking results confirmed the stable interaction of TLR-8 and MEVC-Flu vaccine. Based on these parameters, vaccine constructs can be regarded as an optimistic choice against H5N1 and H7N9 strains of the influenza virus. Further experimental testing of these prophylactic vaccine designs against pathogenic avian influenza strains may clarify their safety and efficacy.Communicated by Ramaswamy H. Sarma.

mRNA delivery systems for cancer immunotherapy: Lipid nanoparticles and beyond

mRNA-based vaccines are emerging as a promising alternative to standard cancer treatments and the conventional vaccines. Moreover, the FDA-approval of three nucleic acid based therapeutics (Onpattro, BNT162b2 and mRNA-1273) has further increased the interest and trust on this type of therapeutics. In order to achieve a significant therapeutic efficacy, the mRNA needs from a drug delivery system. In the last years, several delivery platforms have been explored, being the lipid nanoparticles (LNPs) the most well characterized and studied. A better understanding on how mRNA-based therapeutics operate (both the mRNA itself and the drug delivery system) will help to further improve their efficacy and safety. In this review, we will provide an overview of what mRNA cancer vaccines are and their mode of action and we will highlight the advantages and challenges of the different delivery platforms that are under investigation.

Poly(A) tale: From A to A; RNA polyadenylation in prokaryotes and eukaryotes

Most eukaryotic mRNAs and different non-coding RNAs undergo a form of 3' end processing known as polyadenylation. Polyadenylation machinery is present in almost all organisms except few species. In bacteria, the machinery has evolved from PNPase, which adds heteropolymeric tails, to a poly(A)-specific polymerase. Differently, a complex machinery for accurate polyadenylation and several non-canonical poly(A) polymerases are developed in eukaryotes. The role of poly(A) tail has also evolved from serving as a degradative signal to a stabilizing modification that also regulates translation. In this review, we discuss poly(A) tail emergence in prokaryotes and its development into a stable, yet dynamic feature at the 3' end of mRNAs in eukaryotes. We also describe how appearance of novel poly(A) polymerases gives cells flexibility to shape poly(A) tail. We explain how poly(A) tail dynamics help regulate cognate RNA metabolism in a context-dependent manner, such as during oocyte maturation. Finally, we describe specific mRNAs in metazoans that bear stem-loops instead of poly(A) tails. We conclude with how recent discoveries about poly(A) tail can be applied to mRNA technology. This article is categorized under: RNA Evolution and Genomics > RNA and Ribonucleoprotein Evolution RNA Processing > 3' End Processing RNA Turnover and Surveillance > Regulation of RNA Stability.

Therapeutic synthetic and natural materials for immunoengineering

Immunoengineering is a rapidly evolving field that has been driving innovations in manipulating immune system for new treatment tools and methods. The need for materials for immunoengineering applications has gained significant attention in recent years due to the growing demand for effective therapies that can target and regulate the immune system. Biologics and biomaterials are emerging as promising tools for controlling immune responses, and a wide variety of materials, including proteins, polymers, nanoparticles, and hydrogels, are being developed for this purpose. In this review article, we explore the different types of materials used in immunoengineering applications, their properties and design principles, and highlight the latest therapeutic materials advancements. Recent works in adjuvants, vaccines, immune tolerance, immunotherapy, and tissue models for immunoengineering studies are discussed.

Messenger RNA Therapy for Female Reproductive Health

Female reproductive health has traditionally been an underrepresented area of research in the drug delivery sciences. This disparity is also seen in the emerging field of mRNA therapeutics, a class of medicines that promises to treat and prevent disease by upregulating protein expression in the body. Here, we review advances in mRNA therapies through the lens of improving female reproductive health. Specifically, we begin our review by discussing the fundamental structure and biochemical modifications associated with mRNA-based drugs. Then, we discuss various packaging technologies, including lipid nanoparticles, that can be utilized to protect and transport mRNA drugs to target cells in the body. Last, we conclude our review by discussing the usage of mRNA therapy for addressing pregnancy-related health and vaccination against sexually transmitted diseases in women. Of note, we also highlight relevant clinical trials using mRNA for female reproductive health while also providing their corresponding National Clinical Trial identifiers. In undertaking this review, our aim is to provide a fundamental background understanding of mRNA therapy and its usage to specifically address female health issues with an overarching goal of providing information toward addressing gender disparity in certain aspects of health research.

Mineral coated microparticles doped with fluoride and complexed with mRNA prolong transfection in fracture healing

Introduction: Impaired fracture healing, specifically non-union, has been found to occur up to 14% in tibial shaft fractures. The current standard of care to treat non-union often requires additional surgeries which can result in long recovery times. Injectable-based therapies to accelerate fracture healing have the potential to mitigate the need for additional surgeries. Gene therapies have recently undergone significant advancements due to developments in nanotechnology, which improve mRNA stability while reducing immunogenicity. Methods: In this study, we tested the efficacy of mineral coated microparticles (MCM) and fluoride-doped MCM (FMCM) to effectively deliver firefly luciferase (FLuc) mRNA lipoplexes (LPX) to the fracture site. Here, adult mice underwent a tibia fracture and stabilization method and all treatments were locally injected into the fracture. Level of osteogenesis and amount of bone formation were assessed using gene expression and histomorphometry respectively. Localized and systemic inflammation were measured through gene expression, histopathology scoring and measuring C-reactive protein (CRP) in the serum. Lastly, daily IVIS images were taken to track and measure transfection over time. Results: MCM-LPX-FLuc and FMCM-LPX-FLuc were not found to cause any cytotoxic effects when tested in vitro. When measuring the osteogenic potential of each mineral composition, FMCM-LPX-FLuc trended higher in osteogenic markers through qRT-PCR than the other groups tested in a murine fracture and stabilization model. Despite FMCM-LPX-FLuc showing slightly elevated il-1β and il-4 levels in the fracture callus, inflammation scoring of the fracture callus did not result in any differences. Additionally, an acute systemic inflammatory response was not observed in any of the samples tested. The concentration of MCM-LPX-FLuc and FMCM-LPX-FLuc that was used in the murine fracture model did not stimulate bone when analyzed through stereological principles. Transfection efficacy and kinetics of delivery platforms revealed that FMCM-LPX-FLuc prolongs the luciferase signal both in vitro and in vivo. Discussion: These data together reveal that FMCM-LPX-FLuc could serve as a promising mRNA delivery platform for fracture healing applications.

Nucleic acid degradation as barrier to gene delivery: a guide to understand and overcome nuclease activity

Gene therapy is on its way to revolutionize the treatment of both inherited and acquired diseases, by transferring nucleic acids to correct a disease-causing gene in the target cells of patients. In the fight against infectious diseases, mRNA-based therapeutics have proven to be a viable strategy in the recent Covid-19 pandemic. Although a growing number of gene therapies have been approved, the success rate is limited when compared to the large number of preclinical and clinical trials that have been/are being performed. In this review, we highlight some of the hurdles which gene therapies encounter after administration into the human body, with a focus on nucleic acid degradation by nucleases that are extremely abundant in mammalian organs, biological fluids as well as in subcellular compartments. We overview the available strategies to reduce the biodegradation of gene therapeutics after administration, including chemical modifications of the nucleic acids, encapsulation into vectors and co-administration with nuclease inhibitors and discuss which strategies are applied for clinically approved nucleic acid therapeutics. In the final part, we discuss the currently available methods and techniques to qualify and quantify the integrity of nucleic acids, with their own strengths and limitations.

Advances in Nonviral mRNA Delivery Materials and Their Application as Vaccines for Melanoma Therapy

Messenger RNA (mRNA) vaccines are promising platforms for cancer immunotherapy because of their potential to encode for a variety of tumor antigens, high tolerability, and capacity to induce strong antitumor immune responses. However, the clinical translation of mRNA cancer vaccines can be hindered by the inefficient delivery of mRNA in vivo. In this review, we provide an overview of mRNA cancer vaccines by discussing their utility in treating melanoma. Specifically, we begin our review by describing the barriers that can impede mRNA delivery to target cells. We then review native mRNA structure and discuss various modification methods shown to enhance mRNA stability and transfection. Next, we outline the advantages and challenges of three nonviral carrier platforms (lipid nanoparticles, polymeric nanoparticles, and lipopolyplexes) frequently used for mRNA delivery. Last, we summarize preclinical and clinical studies that have investigated nonviral mRNA vaccines for the treatment of melanoma. In writing this review, we aim to highlight innovative nonviral strategies designed to address mRNA delivery challenges while emphasizing the exciting potential of mRNA vaccines as next-generation therapies for the treatment of cancers.

The mRNA Vaccine Revolution: COVID-19 Has Launched the Future of Vaccinology

During the COVID-19 pandemic, mRNA (mRNA) vaccines emerged as leading vaccine candidates in a record time. Nonreplicating mRNA (NRM) and self-amplifying mRNA (SAM) technologies have been developed into high-performing and clinically viable vaccines against a range of infectious agents, notably SARS-CoV-2. mRNA vaccines demonstrate efficient in vivo delivery, long-lasting stability, and nonexistent risk of infection. The stability and translational efficiency of in vitro transcription (IVT)-mRNA can be further increased by modulating its structural elements. In this review, we present a comprehensive overview of the recent advances, key applications, and future challenges in the field of mRNA-based vaccinology.

Advancements of in vitro transcribed mRNA (IVT mRNA) to enable translation into the clinics

The accelerated progress and approval of two mRNA-based vaccines to address the SARS-CoV-2 virus were unprecedented. This record-setting feat was made possible through the solid foundation of research on in vitro transcribed mRNA (IVT mRNA) which could be utilized as a therapeutic modality. Through decades of thorough research to overcome barriers to implementation, mRNA-based vaccines or therapeutics offer many advantages to rapidly address a broad range of applications including infectious diseases, cancers, and gene editing. Here, we describe the advances that have supported the adoption of IVT mRNA in the clinics, including optimization of the IVT mRNA structural components, synthesis, and lastly concluding with different classes of IVT RNA. Continuing interest in driving IVT mRNA technology will enable a safer and more efficacious therapeutic modality to address emerging and existing diseases.

RNA Therapeutics: A Healthcare Paradigm Shift

COVID-19 brought about the mRNA vaccine and a paradigm shift to a new mode of treating and preventing diseases. Synthetic RNA products are a low-cost solution based on a novel method of using nucleosides to act as an innate medicine factory with unlimited therapeutic possibilities. In addition to the common perception of vaccines preventing infections, the newer applications of RNA therapies include preventing autoimmune disorders, such as diabetes, Parkinson's disease, Alzheimer's disease, and Down syndrome; now, we can deliver monoclonal antibodies, hormones, cytokines, and other complex proteins, reducing the manufacturing hurdles associated with these products. Newer PCR technology removes the need for the bacterial expression of DNA, making mRNA a truly synthetic product. AI-driven product design expands the applications of mRNA technology to repurpose therapeutic proteins and test their safety and efficacy quickly. As the industry focuses on mRNA, many novel opportunities will arise, as hundreds of products under development will bring new perspectives based on this significant paradigm shift-finding newer solutions to existing challenges in healthcare.

Revolutionizing viral disease vaccination: the promising clinical advancements of non-replicating mRNA vaccines

The mRNA vaccine technology was developed rapidly during the global pandemic of COVID-19. The crucial role of the COVID-19 mRNA vaccine in preventing viral infection also have been beneficial to the exploration and application of other viral mRNA vaccines, especially for non-replication structure mRNA vaccines of viral disease with outstanding research results. Therefore, this review pays attention to the existing mRNA vaccines, which are of great value for candidates for clinical applications in viral diseases. We provide an overview of the optimization of the mRNA vaccine development process as well as the good immune efficacy and safety shown in clinical studies. In addition, we also provide a brief description of the important role of mRNA immunomodulators in the treatment of viral diseases. After that, it will provide a good reference or strategy for research on mRNA vaccines used in clinical medicine with more stable structures, higher translation efficiency, better immune efficacy and safety, shorter production time, and lower production costs than conditional vaccines to be used as preventive or therapeutic strategy for the control of viral diseases in the future.

mRNA therapeutics: new vaccination and beyond

The idea of mRNA therapy had been conceived for decades before it came into reality during the Covid-19 pandemic. The mRNA vaccine emerges as a powerful and general tool against new viral infections, largely due to its versatility and rapid development. In addition to prophylactic vaccines, mRNA technology also offers great promise for new applications as a versatile drug modality. However, realizing the conceptual potential faces considerable challenges, such as minimal immune stimulation, high and long-term expression, and efficient delivery to target cells and tissues. Here we review the applications of mRNA-based therapeutics, with emphasis on the innovative design and future challenges/solutions. In addition, we also discuss the next generation of mRNA therapy, including circular mRNA and self-amplifying RNAs. We aim to provide a conceptual overview and outlook on mRNA therapeutics beyond prophylactic vaccines.

Development and applications of mRNA treatment based on lipid nanoparticles

Nucleic acid-based therapies such as messenger RNA have the potential to revolutionize modern medicine and enhance the performance of existing pharmaceuticals. The key challenges of mRNA-based therapies are delivering the mRNA safely and effectively to the target tissues and cells and controlling its release from the delivery vehicle. Lipid nanoparticles (LNPs) have been widely studied as drug carriers and are considered to be state-of-the-art technology for nucleic acid delivery. In this review, we begin by presenting the advantages and mechanisms of action of mRNA therapeutics. Then we discuss the design of LNP platforms based on ionizable lipids and the applications of mRNA-LNP vaccines for prevention of infectious diseases and for treatment of cancer and various genetic diseases. Finally, we describe the challenges and future prospects of mRNA-LNP therapeutics.

mRNA-Based Therapeutics in Cancer Treatment

Over the past two decades, significant technological innovations have led to messenger RNA (mRNA) becoming a promising option for developing prophylactic and therapeutic vaccines, protein replacement therapies, and genome engineering. The success of the two COVID-19 mRNA vaccines has sparked new enthusiasm for other medical applications, particularly in cancer treatment. In vitro-transcribed (IVT) mRNAs are structurally designed to resemble naturally occurring mature mRNA. Delivery of IVT mRNA via delivery platforms such as lipid nanoparticles allows host cells to produce many copies of encoded proteins, which can serve as antigens to stimulate immune responses or as additional beneficial proteins for supplements. mRNA-based cancer therapeutics include mRNA cancer vaccines, mRNA encoding cytokines, chimeric antigen receptors, tumor suppressors, and other combination therapies. To better understand the current development and research status of mRNA therapies for cancer treatment, this review focused on the molecular design, delivery systems, and clinical indications of mRNA therapies in cancer.

Translation of in vitro-transcribed RNA therapeutics

In vitro transcribed, modified messenger RNAs (IVTmRNAs) have been used to vaccinate billions of individuals against the SARS-CoV-2 virus, and are currently being developed for many additional therapeutic applications. IVTmRNAs must be translated into proteins with therapeutic activity by the same cellular machinery that also translates native endogenous transcripts. However, different genesis pathways and routes of entry into target cells as well as the presence of modified nucleotides mean that the way in which IVTmRNAs engage with the translational machinery, and the efficiency with which they are being translated, differs from native mRNAs. This review summarises our current knowledge of commonalities and differences in translation between IVTmRNAs and cellular mRNAs, which is key for the development of future design strategies that can generate IVTmRNAs with improved activity in therapeutic applications.

Therapeutic approaches to activate the canonical Wnt pathway for bone regeneration

Activation of the canonical Wingless-related integration site (Wnt) pathway has been shown to increase bone formation and therefore has therapeutic potential for use in orthopedic conditions. However, attempts at developing an effective strategy to achieve Wnt activation has been met with several challenges. The inherent hydrophobicity of Wnt ligands makes isolating and purifying the protein difficult. To circumvent these challenges, many have sought to target extracellular inhibitors of the Wnt pathway, such as Wnt signaling pathway inhibitors Sclerostin and Dickkopf-1, or to use small molecules, ions and proteins to increase target Wnt genes. Here, we review systemic and localized bioactive approaches to enhance bone formation or improve bone repair through antibody-based therapeutics, synthetic Wnt surrogates and scaffold doping to target canonical Wnt. We conclude with a brief review of emerging technologies, such as mRNA therapy and Clustered Regularly Interspaced Short Palindromic Repeats technology, which serve as promising approaches for future clinical translation.

Unlocking the promise of mRNA therapeutics

The extraordinary success of mRNA vaccines against coronavirus disease 2019 (COVID-19) has renewed interest in mRNA as a means of delivering therapeutic proteins. Early clinical trials of mRNA therapeutics include studies of paracrine vascular endothelial growth factor (VEGF) mRNA for heart failure and of CRISPR-Cas9 mRNA for a congenital liver-specific storage disease. However, a series of challenges remains to be addressed before mRNA can be established as a general therapeutic modality with broad relevance to both rare and common diseases. An array of new technologies is being developed to surmount these challenges, including approaches to optimize mRNA cargos, lipid carriers with inherent tissue tropism and in vivo percutaneous delivery systems. The judicious integration of these advances may unlock the promise of biologically targeted mRNA therapeutics, beyond vaccines and other immunostimulatory agents, for the treatment of diverse clinical indications.

Current knowledge on the tissue distribution of mRNA nanocarriers for therapeutic protein expression

Exogenously delivered mRNA-based drugs are emerging as a new class of therapeutics with the potential to treat several diseases. Over the last decade, advancements in the design of non-viral delivery tools have enabled mRNA to be evaluated for several therapeutic purposes including protein replacement therapies, gene editing, and vaccines. However, in vivo delivery of mRNA to targeted organs and cells remains a critical challenge. Evaluation of the biodistribution of mRNA vehicles is of utmost importance for the development of effective pharmaceutical candidates. In this review, we discuss the recent advances in the design of nanoparticles loaded with mRNA and extrapolate the key factors influencing their biodistribution following administration. Finally, we highlight the latest developments in the preclinical and clinical translation of mRNA therapeutics for protein supplementation therapy.

Lipid nanoparticle-based mRNA vaccines in cancers: Current advances and future prospects

Messenger RNA (mRNA) vaccines constitute an emerging therapeutic method with the advantages of high safety and efficiency as well as easy synthesis; thus, they have been widely used in various human diseases, especially in malignant cancers. However, the mRNA vaccine technology has some limitations, such as instability and low transitive efficiency in vivo, which greatly restrict its application. The development of nanotechnology in the biomedical field offers new strategies and prospects for the early diagnosis and treatment of human cancers. Recent studies have demonstrated that Lipid nanoparticle (LNP)-based mRNA vaccines can address the poor preservation and targeted inaccuracy of mRNA vaccines. As an emerging cancer therapy, mRNA vaccines potentially have broad future applications. Unlike other treatments, cancer mRNA vaccines provide specific, safe, and tolerable treatments. Preclinical studies have used personalized vaccines to demonstrate the anti-tumor effect of mRNA vaccines in the treatment of various solid tumors, including colorectal and lung cancer, using these in a new era of therapeutic cancer vaccines. In this review, we have summarized the latest applications and progress of LNP-based mRNA vaccines in cancers, and discussed the prospects and limitations of these fields, thereby providing novel strategies for the targeted therapy of cancers.

Recent Advances in the Molecular Design and Delivery Technology of mRNA for Vaccination Against Infectious Diseases

Vaccines can prevent many millions of illnesses against infectious diseases and save numerous lives every year. However, traditional vaccines such as inactivated viral and live attenuated vaccines cannot adapt to emerging pandemics due to their time-consuming development. With the global outbreak of the COVID-19 epidemic, the virus continues to evolve and mutate, producing mutants with enhanced transmissibility and virulence; the rapid development of vaccines against such emerging global pandemics becomes more and more critical. In recent years, mRNA vaccines have been of significant interest in combating emerging infectious diseases due to their rapid development and large-scale production advantages. However, their development still suffers from many hurdles such as their safety, cellular delivery, uptake, and response to their manufacturing, logistics, and storage. More efforts are still required to optimize the molecular designs of mRNA molecules with increased protein expression and enhanced structural stability. In addition, a variety of delivery systems are also needed to achieve effective delivery of vaccines. In this review, we highlight the advances in mRNA vaccines against various infectious diseases and discuss the molecular design principles and delivery systems of associated mRNA vaccines. The current state of the clinical application of mRNA vaccine pipelines against various infectious diseases and the challenge, safety, and protective effect of associated vaccines are also discussed.

The legacy of mRNA engineering: A lineup of pioneers for the Nobel Prize

mRNA is like Hermes, delivering the genetic code to cellular construction sites, so it has long been of interest, but only to a small group of scientists, and only demonstrating its remarkable efficacy in coronavirus disease 2019 (COVID-19) vaccines allowed it to go out into the open. Therefore, now is the right timing to delve into the stepping stones that underpin this success and pay tribute to the underlying scientists. From this perspective, advances in mRNA engineering have proven crucial to the rapidly growing role of this molecule in healthcare. Development of consecutive generations of cap analogs, including anti-reverse cap analogs (ARCAs), has significantly boosted translation efficacy and maintained an enthusiasm for mRNA research. Nucleotide modification to protect mRNA molecules from the host's immune system, followed by finding appropriate purification and packaging methods, were other links in the chain enabling medical breakthroughs. Currently, vaccines are the central area of mRNA research, but it will reach far beyond COVID-19. Supplementation of missing or abnormal proteins is another large field of mRNA research. Ex vivo cell engineering and genome editing have been expanding recently. Thus, it is time to recognize mRNA pioneers while building upon their legacy.

mRNA delivery technologies: Toward clinical translation

Messenger RNA (mRNA)-therapies have recently taken a huge step toward clinic thanks to the first mRNA-based medicinal products marketed. mRNA features for clinical purposes are improved by chemical modifications, but the inclusion in a delivery system is a regular requirement. mRNA nanomedicines must be designed for the specific therapeutic purpose, protecting the nucleic acid and facilitating the overcoming of biological barriers. Polymers, polypeptides, and cationic lipids are the main used materials to design mRNA delivery systems. Among them, lipid nanoparticles (LNPs) are the most advanced ones, and currently they are at the forefront of preclinical and clinical evaluation in several fields, including immunotherapy (against infectious diseases and cancer), protein replacement, gene editing and regenerative medicine. This chapter includes an overview on mRNA delivery technologies, with special interest in LNPs, and the most recent advances in their clinical application. Liposomes are the mRNA delivery technology with the highest clinical translation among LNPs, whereas the first clinical trial of a therapeutic mRNA formulated in exosomes has been recently approved for protein replacement therapy. The first mRNA products approved by the regulatory agencies worldwide are LNP-based mRNA vaccines against viral infections, specifically against the 2019 coronavirus disease (COVID-19). The clinical translation of mRNA-therapies for cancer is mainly focused on three strategies: anti-cancer vaccination by means of delivering cancer antigens or acting as an adjuvant, mRNA-engineered chimeric antigen receptors (CARs) and T-cell receptors (TCRs), and expression of antibodies and immunomodulators. Cancer immunotherapy and, more recently, COVID-19 vaccines spearhead the advance of mRNA clinical use.

mRNA-based therapies: Preclinical and clinical applications

At the fundamental level, messenger RNA (mRNA)-based therapeutics involves the delivery of in vitro-transcribed (IVT) mRNA into the cytoplasm of a target cell, where it is translated into the desired protein. IVT mRNA presents various advantages compared to DNA and recombinant protein-based approaches that make it ideal for a broad range of therapeutic applications. IVT mRNA, which is translated in the cytoplasm after transfection into cells, can encode virtually any target protein. Notably, it does not enter the nucleus, which avoids its integration into the genome and the risk of insertional mutagenesis. The large-scale production of IVT mRNA is less complex than production of recombinant proteins, and Good Manufacturing Practice-compliant mRNA production is easily scalable, ideally poising mRNA for not only off-the-shelf, but more personalized treatment approaches. IVT mRNA's safety profile, pharmacokinetics, and pharmacodynamics, including its inherent immunostimulatory capacity, can be optimized for different therapeutic applications by harnessing a wide array of optimized sequence elements, chemical modifications, purification techniques, and delivery methods. The value of IVT mRNA was recently proved during the COVID-19 pandemic when mRNA-based vaccines outperformed the efficacy of established technologies, and millions of doses were rapidly deployed. In this review, we will discuss chemical modifications of IVT mRNA and highlight numerous preclinical and clinical applications including vaccines for cancer and infectious diseases, cancer immunotherapy, protein replacement, gene editing, and cell reprogramming.

mRNA-based therapeutics: powerful and versatile tools to combat diseases

The therapeutic use of messenger RNA (mRNA) has fueled great hope to combat a wide range of incurable diseases. Recent rapid advances in biotechnology and molecular medicine have enabled the production of almost any functional protein/peptide in the human body by introducing mRNA as a vaccine or therapeutic agent. This represents a rising precision medicine field with great promise for preventing and treating many intractable or genetic diseases. In addition, in vitro transcribed mRNA has achieved programmed production, which is more effective, faster in design and production, as well as more flexible and cost-effective than conventional approaches that may offer. Based on these extraordinary advantages, mRNA vaccines have the characteristics of the swiftest response to large-scale outbreaks of infectious diseases, such as the currently devastating pandemic COVID-19. It has always been the scientists’ desire to improve the stability, immunogenicity, translation efficiency, and delivery system to achieve efficient and safe delivery of mRNA. Excitingly, these scientific dreams have gradually been realized with the rapid, amazing achievements of molecular biology, RNA technology, vaccinology, and nanotechnology. In this review, we comprehensively describe mRNA-based therapeutics, including their principles, manufacture, application, effects, and shortcomings. We also highlight the importance of mRNA optimization and delivery systems in successful mRNA therapeutics and discuss the key challenges and opportunities in developing these tools into powerful and versatile tools to combat many genetic, infectious, cancer, and other refractory diseases.

Messenger RNA as a personalized therapy: The moment of truth for rare metabolic diseases

Inborn errors of metabolism (IEM) encompass a group of monogenic diseases affecting both pediatric and adult populations and currently lack effective treatments. Some IEM such as familial hypercholesterolemia or X-linked protoporphyria are caused by gain of function mutations, while others are characterized by an impaired protein function, causing a metabolic pathway blockage. Pathophysiology classification includes intoxication, storage and energy-related metabolic disorders. Factors specific to each disease trigger acute metabolic decompensations. IEM require prompt and effective care, since therapeutic delay has been associated with the development of fatal events including severe metabolic acidosis, hyperammonemia, cerebral edema, and death. Rapid expression of therapeutic proteins can be achieved hours after the administration of messenger RNAs (mRNA), representing an etiological solution for acute decompensations. mRNA-based therapy relies on modified RNAs with enhanced stability and translatability into therapeutic proteins. The proteins produced in the ribosomes can be targeted to specific intracellular compartments, the cell membrane, or be secreted. Non-immunogenic lipid nanoparticle formulations have been optimized to prevent RNA degradation and to allow safe repetitive administrations depending on the disease physiopathology and clinical status of the patients, thus, mRNA could be also an effective chronic treatment for IEM. Given that the liver plays a key role in most of metabolic pathways or can be used as bioreactor for excretable proteins, this review focuses on the preclinical and clinical evidence that supports the implementation of mRNA technology as a promising personalized strategy for liver metabolic disorders such as acute intermittent porphyria, ornithine transcarbamylase deficiency or glycogen storage disease.

Bioengineering of Novel Non-Replicating mRNA (NRM) and Self-Amplifying mRNA (SAM) Vaccine Candidates Against SARS-CoV-2 Using Immunoinformatics Approach

Presently, the world needs safe and effective vaccines to overcome the COVID-19 pandemic. Our work has focused on formulating two types of mRNA vaccines that differ in capacity to copy themselves inside the cell. These are non-amplifying mRNA (NRM) and self-amplifying mRNA (SAM) vaccines. Both the vaccine candidates encode an engineered viral replicon which can provoke an immune response. Hence we predicted and screened twelve epitopes from the spike glycoprotein of SARS-CoV-2. We used five CTL, four HTL, and three B-cell-activating epitopes to formulate each mRNA vaccine. Molecular docking revealed that these epitopes could combine with HLA molecules that are important for boosting immunogenicity. The B-cell epitopes were adjoined with GPGPG linkers, while CTL and HTL epitopes were linked with KK linkers. The entire protein chain was reverse translated to develop a specific NRM-based vaccine. We incorporate gene encoding replicase in the upstream region of CDS encoding antigen to design the SAM vaccine. Subsequently, signal sequences were added to human mRNA to formulate vaccines. Both vaccine formulations translated to produce the epitopes in host cells, initiate a protective immune cascade, and generate immunogenic memory, which can counter future SARS-CoV-2 viral exposures before the onset of infection.

mRNA vaccines: the most recent clinical applications of synthetic mRNA

Synthetic mRNA has been considered as an emerging biotherapeutic agent for the past decades. Recently, the SARS-CoV-2 pandemic has led to the first clinical use of synthetic mRNA. mRNA vaccines showed far surpassing influences on the public as compared to other vaccine platforms such as viral vector vaccines and recombinant protein vaccines. It allowed rapid development and production of vaccines that have never been achieved in history. Synthetic mRNA, called in vitro transcribed (IVT) mRNA, is the key component of mRNA vaccines. It has several advantages over conventional gene-expressing systems such as plasmid DNA and viral vectors. It can translate proteins in the cytoplasm by structurally resembling natural mRNA and exhibit various protein expression patterns depending on how it is engineered. Another advantage is that synthetic mRNA enables fast, scalable, and cost-effective production. Therefore, starting with the mRNA vaccine, synthetic mRNA is now in the spotlight as a promising new drug development agent. In this review, we will summarize the latest IVT mRNA technology such as new mRNA structures or large-scale production. In addition, the nature of the innate immunogenicity of IVT mRNA will be discussed along with its roles in the development of vaccines. Finally, the principles of the mRNA vaccine and the future direction of synthetic mRNA will be provided.

A brief review of mRNA therapeutics and delivery for bone tissue engineering

The therapeutics for bone tissue regeneration requires constant advancements owing to the steady increase in the number of patients suffering from bone-related disorders, and also to find efficient and cost-effective treatment modalities. One of the major advancements in the field of therapeutics is the development of mRNAs. mRNAs, which have been extensively tested for the vaccines, could be very well utilized as a potential inducer for bone regeneration. The ability of mRNAs to enter the cells and instruct the cellular machinery to produce the required native proteins such as BMP or VEGF is a great way to avoid the issues faced with growth factor deliveries such as the production cost, loss of biological function etc. However, there have been a few hurdles for using mRNAs as an effective therapeutic agent, such as proper dosing, tolerating the degradation by RNases, improving the half-life, controlling the spatio-temporal release and reducing the off-target effects. This brief review discusses the various developments in the field of mRNA therapeutics especially for bone tissue engineering, how nano-formulations are being developed to effectively deliver the mRNAs into the cells by evading the immune responses, how researchers have developed certain strategies to increase the half-life, to successfully deliver the mRNAs to specific bone defect area and bring about effective bone regeneration.

mRNA Lipoplexes with Cationic and Ionizable α-Amino-lipophosphonates: Membrane Fusion, Transfection, mRNA Translation and Conformation

Cationic liposomes are attractive carriers for mRNA delivery. Here, mRNA lipoplexes (LX) were prepared with the cationic lipids α-aminolipophosphonate (3b) or imidazolium lipophosphoramidate (2) associated with various α-aminolipophosphonates co-lipids comprising protonable groups (imidazole or pyridine) and DOPE. Physicochemical parameters of liposomes and their membrane fusion activity were measured. LXs comprising either 3b- or 2- allowed transfection of ~25% and 40% of dendritic cells with low cytotoxicity, respectively; the efficiency increased up to 80% when 2 was combined with the imidazole-based co-lipid 1. The transfections were high with 3b/1, 3b/DOPE, 2/1 and 2/DOPE LXs. We observed that the transfection level was not well correlated with the acid-mediated membrane fusion activity of liposomes supposed to destabilize endosomes. The mRNA release from LXs and its translation capacity after release were studied for the most efficient LXs. The results showed that the more mRNA was condensed, the poorer the translation efficiency after release was. In contrast to DNA, circular dichroism performed on mRNA complexed with 2/DOPE revealed the presence of denatured mRNA in LXs explaining this lack of translation efficiency. This is an important parameter that should be stressed for the preparation of mRNA LXs with a conserved mRNA translation activity.

RNA-Based Strategies for Cell Reprogramming toward Pluripotency

Cell therapy approaches to treat a wide range of pathologies have greatly benefited from cell reprogramming techniques that allow the conversion of a somatic cell into a pluripotent cell. Many technological developments have been made since the initial major discovery of this biological process. Recently reprogramming methods based on the use of RNA have emerged and seem very promising. Thus, in this review we will focus on presenting the interest of such methods for cell reprogramming but also how these RNA-based strategies can be extended to eventually lead to medical applications to improve healthspan and longevity.

Nanotechnologies in Delivery of DNA and mRNA Vaccines to the Nasal and Pulmonary Mucosa

Recent advancements in the field of in vitro transcribed mRNA (IVT-mRNA) vaccination have attracted considerable attention to such vaccination as a cutting-edge technique against infectious diseases including COVID-19 caused by SARS-CoV-2. While numerous pathogens infect the host through the respiratory mucosa, conventional parenterally administered vaccines are unable to induce protective immunity at mucosal surfaces. Mucosal immunization enables the induction of both mucosal and systemic immunity, efficiently removing pathogens from the mucosa before an infection occurs. Although respiratory mucosal vaccination is highly appealing, successful nasal or pulmonary delivery of nucleic acid-based vaccines is challenging because of several physical and biological barriers at the airway mucosal site, such as a variety of protective enzymes and mucociliary clearance, which remove exogenously inhaled substances. Hence, advanced nanotechnologies enabling delivery of DNA and IVT-mRNA to the nasal and pulmonary mucosa are urgently needed. Ideal nanocarriers for nucleic acid vaccines should be able to efficiently load and protect genetic payloads, overcome physical and biological barriers at the airway mucosal site, facilitate transfection in targeted epithelial or antigen-presenting cells, and incorporate adjuvants. In this review, we discuss recent developments in nucleic acid delivery systems that target airway mucosa for vaccination purposes.

Non-liver mRNA Delivery

mRNA drugs can preempt infectious disease and treat Mendelian disorders, such as sickle cell anemia, muscular dystrophy, and cystic fibrosis, as well as autoimmunity and cancer. The three major therapeutic areas for which mRNA delivery is currently being explored are antigen production, including the COVID-19 vaccine, protein replacement therapy, and genome engineering. It was demonstrated 30 years ago that introducing in vitro transcribed mRNA intramuscularly results in detectable protein expression for specific antigens protecting against the likes of influenza and cancer. Utilizing mRNA as a therapeutic modality, however, is challenging. mRNA is large and anionic and, as a result, cannot passively diffuse across the negatively charged plasma membrane. In addition, RNases present in the bloodstream and tissues rapidly degrade mRNA, and its administration induces the innate immune response. In consequence, lipid-, polymer-, dendrimer-, and natural membrane-based mRNA drug delivery systems have been developed to deliver mRNA to target cells. Significant efforts and investments have been made to translate some of these systems into the clinic. Specifically, systemically administered lipid nanoparticles (LNPs) have delivered mRNA to the liver, and intramuscularly administered LNPs have delivered mRNA to immune cells to protect against coronavirus disease of 2019. However, clinically relevant delivery in non-liver tissues such as the spleen, lungs, heart, eye, central nervous system, and lymphatics requires improved drug delivery systems.In this Account, we provide an overview of key advances that have led us to Food and Drug Administration approval for the Pfizer/BioNTech mRNA-based vaccine against SARS-CoV-2 and Emergency Use Authorization for the Moderna mRNA-based vaccine against the same disease, and we explain how these developments will contribute to the clinical translation of mRNA therapeutics targeted outside of the liver. We first focus on the chemical modifications and sequence optimization that can improve the potency of mRNA, resulting in greatly improved pharmacokinetics. After detailing what makes an ideal mRNA payload, we review drug delivery systems used to deliver the payload into target cells. We describe efforts to reduce clearance by the liver, a key obstacle to the development of non-liver therapies. We then consider recent examples of nanoparticles that have delivered mRNA to non-liver tissues. Finally, we discuss current clinical mRNA programs, focusing on the COVID vaccines and highlighting lessons that may be applied to future mRNA drugs.

mRNA-Based Vaccines and Mode of Action

In the past 20 years, the mRNA vaccine technology has evolved from the first proof of concept to the first licensed vaccine against emerging pandemics such as SARS-CoV-2. Two mRNA vaccines targeting SARS-CoV-2 have received emergency use authorization by US FDA, conditional marketing authorization by EMA, as well as multiple additional national regulatory authorities. The simple composition of an mRNA encoding the antigen formulated in a lipid nanoparticle enables a fast adaptation to new emerging pathogens. This can speed up vaccine development in pandemics from antigen and sequence selection to clinical trial to only a few months. mRNA vaccines are well tolerated and efficacious in animal models for multiple pathogens and will further contribute to the development of vaccines for other unaddressed diseases. Here, we give an overview of the mRNA vaccine design and factors for further optimization of this new promising technology and discuss current knowledge on the mode of action of mRNA vaccines interacting with the innate and adaptive immune system.

Advances in mRNA vaccines

mRNA vaccines have been increasingly recognized as a powerful vaccine platform since the FDA approval of two COVID-19 mRNA vaccines, which demonstrated outstanding prevention efficacy as well as great safety profile. Notably, nucleoside modification and lipid nanoparticle-facilitated delivery has greatly improved the immunogenicity, stability, and translation efficiency of mRNA molecule. Here we review the recent progress in mRNA vaccine development, including nucleoside modification, in vitro synthesis and product purification, and lipid nanoparticle vectors for in vivo delivery and efficient translation. We also briefly introduce the clinical application of mRNA vaccine in preventing infectious diseases and treating inflammatory diseases including cancer.

Advances in Development of mRNA-Based Therapeutics

Recently, mRNA-based therapeutics have been greatly boosted since the development of novel technologies of both mRNA synthesis and delivery system. Promising results were showed in both preclinical and clinical studies in the field of cancer vaccine, tumor immunotherapy, infectious disease prevention and protein replacement therapy. Recent advancements in clinical trials also encouraged scientists to attempt new applications of mRNA therapy such as gene editing and cell programming. These studies bring mRNA therapeutics closer to real-world application. Herein, we provide an overview of recent advances in mRNA-based therapeutics.

Modified mRNA-Based Vaccines Against Coronavirus Disease 2019

The pandemic of coronavirus disease 2019 (COVID-19) continuously causes deaths worldwide, representing a considerable challenge to health care and economic systems with a new precedent in human history. Many therapeutic medicines primarily focused on preventing severe organ damage and complications, which can be fatal in some confirmed cases. The synthesized modified mRNA (modRNA) represents a nonviral, integration-free, zero-footprint, efficient, and safe strategy for vaccine discovery. modRNA-based technology has facilitated the rapid development of the first COVID-19 vaccines due to its cost- and time-saving properties, thus initiating a new era of prophylactic vaccines against infectious diseases. Recently, COVID-19 modRNA vaccines were approved, and a large-scale vaccination campaign began worldwide. To date, results suggest that the modRNA vaccines are highly effective against virus infection, which causes COVID-19. Although short-term studies have reported that their safety is acceptable, long-term safety and protective immunity remain unclear. In this review, we describe two major approved modRNA vaccines and discuss their potential myocarditis complications.

Demystifying mRNA vaccines: an emerging platform at the forefront of cryptic diseases

Messenger RNA (mRNA) vaccines have been studied for decades, but only recently, during the COVID-19 pandemic, has the technology garnered noteworthy attention. In contrast to traditional vaccines, mRNA vaccines elicit a more balanced immune response, triggering both humoral and cellular components of the adaptive immune system. However, some inherent hurdles associated with stability, immunogenicity, in vivo delivery, along with the novelty of the technology, have generated scepticism in the adoption of mRNA vaccines. Recent developments have pushed to bypass these issues and the approval of mRNA-based vaccines to combat COVID-19 has further highlighted the feasibility, safety, efficacy, and rapid development potential of this platform, thereby pushing it to the forefront of emerging therapeutics. This review aims to demystify mRNA vaccines, delineating the evolution of the technology which has emerged as a timely solution to COVID-19 and exploring the immense potential it offers as a prophylactic option for other cryptic diseases.

Therapeutic mRNA Engineering from Head to Tail

Synthetic messenger RNA (mRNA), once delivered into cells, can be readily translated into proteins by ribosomes, which do not distinguish exogenous mRNAs from endogenous transcripts. Until recently, the intrinsic instability and immunostimulatory property of exogenous RNAs largely hindered the therapeutic application of synthetic mRNAs. Thanks to major technological innovations, such as introduction of chemically modified nucleosides, synthetic mRNAs have become programmable therapeutic reagents. Compared to DNA or protein-based therapeutic reagents, synthetic mRNAs bear several advantages: flexible design, easy optimization, low-cost preparation, and scalable synthesis. Therapeutic mRNAs are commonly designed to encode specific antigens to elicit organismal immune response to pathogens like viruses, express functional proteins to replace defective ones inside cells, or introduce novel enzymes to achieve unique functions like genome editing. Recent years have witnessed stunning progress on the development of mRNA vaccines against SARS-Cov2. This success is built upon our fundamental understanding of mRNA metabolism and translational control, a knowledge accumulated during the past several decades. Given the astronomical number of sequence combinations of four nucleotides, sequence-dependent control of mRNA translation remains incompletely understood. Rational design of synthetic mRNAs with robust translation and optimal stability remains challenging. Massively paralleled reporter assay (MPRA) has been proven to be powerful in identifying sequence elements in controlling mRNA translatability and stability. Indeed, a completely randomized sequence in 5' untranslated region (5'UTR) drives a wide range of translational outputs. In this Account, we will discuss general principles of mRNA translation in eukaryotic cells and elucidate the role of coding and noncoding regions in the translational regulation. From the therapeutic perspective, we will highlight the unique features of 5' cap, 5'UTR, coding region (CDS), stop codon, 3'UTR, and poly(A) tail. By focusing on the design strategies in mRNA engineering, we hope this Account will contribute to the rational design of synthetic mRNAs with broad therapeutic potential.

CRISPR-derived genome editing therapies: Progress from bench to bedside

The development of CRISPR-derived genome editing technologies has enabled the precise manipulation of DNA sequences within the human genome. In this review, we discuss the initial development and cellular mechanism of action of CRISPR nucleases and DNA base editors. We then describe factors that must be taken into consideration when developing these tools into therapeutic agents, including the potential for unintended and off-target edits when using these genome editing tools, and methods to characterize these types of edits. We finish by considering specific challenges associated with bringing a CRISPR-based therapy to the clinic, including manufacturing, regulatory oversight, and considerations for clinical trials that involve genome editing agents.

The Current Status of COVID-19 Vaccines

The current COVID-19 pandemic has substantially accelerated the demands for efficient vaccines. A wide spectrum of approaches includes live attenuated and inactivated viruses, protein subunits and peptides, viral vector-based delivery, DNA plasmids, and synthetic mRNA. Preclinical studies have demonstrated robust immune responses, reduced viral loads and protection against challenges with SARS-CoV-2 in rodents and primates. Vaccine candidates based on all delivery systems mentioned above have been subjected to clinical trials in healthy volunteers. Phase I clinical trials have demonstrated in preliminary findings good safety and tolerability. Evaluation of immune responses in a small number of individuals has demonstrated similar or superior levels of neutralizing antibodies in comparison to immunogenicity detected in COVID-19 patients. Both adenovirus- and mRNA-based vaccines have entered phase II and study protocols for phase III trials with 30,000 participants have been finalized.

Nucleic Acid Drugs-Current Status, Issues, and Expectations for Exosomes

Simple Summary

Nucleic acid drugs provide novel therapeutic modalities with characteristics that differ from those of small molecules and antibodies. In this review, I focus on the various mechanisms through which nucleic acid drugs act on, the status of their clinical development, and discuss several hurdles that need to be surmounted. In addition, by listing examples of how the progress in exosome biology can lead to the solution of problems in nucleic acid drug therapy, I hope that many more nucleic acid drugs including anticancer drugs will be developed in the future.

Abstract

Nucleic acid drugs are being developed as novel therapeutic modalities. They have great potential to treat human diseases such as cancers, viral infections, and genetic disorders due to unique characteristics that make it possible to approach undruggable targets using classical small molecule or protein/antibody-based biologics. In this review, I describe the advantages, classification, and clinical status of nucleic acid therapeutics. To date, more than 10 products have been launched, and many products have been tested in clinics. To promote the use of nucleic acid therapeutics such as antibodies, several hurdles need to be surmounted. The most important issue is the delivery of nucleic acids and several other challenges have been reported. Recent advanced delivery platforms are lipid nanoparticles and ligand conjugation approaches. With the progress of exosome biology, exosomes are expected to contribute to the solution of various problems associated with nucleic acid drugs.

Strategies for controlling the innate immune activity of conventional and self-amplifying mRNA therapeutics: Getting the message across

The recent approval of messenger RNA (mRNA)-based vaccines to combat the SARS-CoV-2 pandemic highlights the potential of both conventional mRNA and self-amplifying mRNA (saRNA) as a flexible immunotherapy platform to treat infectious diseases. Besides the antigen it encodes, mRNA itself has an immune-stimulating activity that can contribute to vaccine efficacy. This self-adjuvant effect, however, will interfere with mRNA translation and may influence the desired therapeutic outcome. To further exploit its potential as a versatile therapeutic platform, it will be crucial to control mRNA's innate immune-stimulating properties. In this regard, we describe the mechanisms behind the innate immune recognition of mRNA and provide an extensive overview of strategies to control its innate immune-stimulating activity. These strategies range from modifications to the mRNA backbone itself, optimization of production and purification processes to the combination with innate immune inhibitors. Furthermore, we discuss the delicate balance of the self-adjuvant effect in mRNA vaccination strategies, which can be both beneficial and detrimental to the therapeutic outcome.

Application of Modified mRNA in Somatic Reprogramming to Pluripotency and Directed Conversion of Cell Fate

Modified mRNA (modRNA)-based somatic reprogramming is an effective and safe approach that overcomes the genomic mutation risk caused by viral integrative methods. It has improved the disadvantages of conventional mRNA and has better stability and immunogenicity. The modRNA molecules encoding multiple pluripotent factors have been applied successfully in reprogramming somatic cells such as fibroblasts, mesenchymal stem cells, and amniotic fluid stem cells to generate pluripotent stem cells (iPSCs). Moreover, it also can be directly used in the terminal differentiation of stem cells and fibroblasts into functional therapeutic cells, which exhibit great promise in disease modeling, drug screening, cell transplantation therapy, and regenerative medicine. In this review, we summarized the reprogramming applications of modified mRNA in iPSC generation and therapeutic applications of functionally differentiated cells.

Dendrimer-Coated Gold Nanoparticles for Efficient Folate-Targeted mRNA Delivery In Vitro

Messenger RNA (mRNA) is not an attractive candidate for gene therapy due to its instability and has therefore received little attention. Recent studies show the advantage of mRNA over DNA, especially in cancer immunotherapy and vaccine development. This study aimed to formulate folic-acid-(FA)-modified, poly-amidoamine-generation-5 (PAMAM G5D)-grafted gold nanoparticles (AuNPs) and to evaluate their cytotoxicity and transgene expression using the luciferase reporter gene (FLuc-mRNA) in vitro. Nanocomplexes were spherical and of favorable size. Nanocomplexes at optimum nanoparticle:mRNA (w/w) binding ratios showed good protection of the bound mRNA against nucleases and were well tolerated in all cell lines. Transgene expression was significantly (p < 0.0001) higher with FA-targeted, dendrimer-grafted AuNPs (Au:G5D:FA) in FA receptors overexpressing MCF-7 and KB cells compared to the G5D and G5D:FA NPs, decreasing significantly (p < 0.01) in the presence of excess competing FA ligand, which confirmed nanocomplex uptake via receptor mediation. Overall, transgene expression of the Au:G5D and Au:G5D:FA nanocomplexes exceeded that of G5D and G5D:FA nanocomplexes, indicating the pivotal role played by the inclusion of the AuNP delivery system. The favorable properties imparted by the AuNPs potentiated an increased level of luciferase gene expression.

mRNA therapeutics in cancer immunotherapy

Synthetic mRNA provides a template for the synthesis of any given protein, protein fragment or peptide and lends itself to a broad range of pharmaceutical applications, including different modalities of cancer immunotherapy. With the ease of rapid, large scale Good Manufacturing Practice-grade mRNA production, mRNA is ideally poised not only for off-the shelf cancer vaccines but also for personalized neoantigen vaccination. The ability to stimulate pattern recognition receptors and thus an anti-viral type of innate immune response equips mRNA-based vaccines with inherent adjuvanticity. Nucleoside modification and elimination of double-stranded RNA can reduce the immunomodulatory activity of mRNA and increase and prolong protein production. In combination with nanoparticle-based formulations that increase transfection efficiency and facilitate lymphatic system targeting, nucleoside-modified mRNA enables efficient delivery of cytokines, costimulatory receptors, or therapeutic antibodies. Steady but transient production of the encoded bioactive molecule from the mRNA template can improve the pharmacokinetic, pharmacodynamic and safety properties as compared to the respective recombinant proteins. This may be harnessed for applications that benefit from a higher level of expression control, such as chimeric antigen receptor (CAR)-modified adoptive T-cell therapies. This review highlights the advancements in the field of mRNA-based cancer therapeutics, providing insights into key preclinical developments and the evolving clinical landscape.

Exosomes for mRNA delivery: a novel biotherapeutic strategy with hurdles and hope

Over the past decade, therapeutic messenger RNAs (mRNAs) have emerged as a highly promising new class of drugs for protein replacement therapies. Due to the recent developments, the incorporation of modified nucleotides in synthetic mRNAs can lead to maximizing protein expression and reducing adverse immunogenicity. Despite these stunning improvements, mRNA therapy is limited by the need for the development of safe and efficient carriers to protect the mRNA integrity for in vivo applications. Recently, leading candidates for in vivo drug delivery vehicles are cell-derived exosomes, which have fewer immunogenic responses. In the current study, the key hurdles facing mRNA-based therapeutics, with an emphasis on recent strategies to overcoming its immunogenicity and instability, were highlighted. Then the immunogenicity and toxicity of exosomes derived from various cell sources were mentioned in detail. Finally, an overview of the recent strategies in using exosomes for mRNA delivery in the treatment of multiple diseases was stated.