Viral Vectors For Gene Therapy Research Articles

Tackling scalability challenges in AAV manufacture

Kyle Grant is a trained PhD chemical engineer with a concentration in molecular virology. Kyle has extensive experience in the molecular analysis of virus host cell interactions, as well as innovation around commercial grade unit operations to support CMC activities for the application of viral vectors in gene therapy. This multi-scale approach allows for comprehensive insight into the development of methods for provision and release of novel drug candidates to address the unmet need for patients where there is no available cure.

Design and Validation of a Multi-Point Injection Technology for MR-Guided Convection Enhanced Delivery in the Brain.

Convection enhanced delivery (CED) allows direct intracranial administration of neuro-therapeutics. Success of CED relies on specific targeting and broad volume distributions (VD). However, to prevent off-target delivery and tissue damage, CED is typically conducted with small cannulas and at low flow rates, which critically limit the maximum achievable VD. Furthermore, in applications such as gene therapy requiring injections of large fluid volumes into broad subcortical regions, low flow rates translate into long infusion times and multiple surgical trajectories. The cannula design is a major limiting factor in achieving broad VD, while minimizing infusion time and backflow. Here we present and validate a novel multi-point cannula specifically designed to optimize distribution and delivery time in MR-guided intracranial CED of gene-based therapeutics. First, we evaluated the compatibility of our cannula with MRI and common viral vectors for gene therapy. Then, we conducted CED tests in agarose brain phantoms and benchmarked the results against single-needle delivery. 3T MRI in brain phantoms revealed minimal susceptibility-induced artifacts, comparable to the device dimensions. Benchtop CED of adeno-associated virus demonstrated no viral loss or inactivation. CED in agarose brain phantoms at 3, 6, and 9 μL/min showed >3x increase in volume distribution and 60% time reduction compared to single-needle delivery. This study confirms the validity of a multi-point delivery approach for improving infusate distribution at clinically-compatible timescales and supports the feasibility of our novel cannula design for advancing safety and efficacy of MR-guided CED to the central nervous system.

GABAergic Gene Regulatory Elements Used in Adeno-Associated Viral Vectors.

Several neurological and psychiatric disorders have been associated with impairments in GABAergic inhibitory neurons in the brain. Thus, in the current era of accelerated development of molecular medicine and biologically-based drugs, there is a need to identify gene regulatory sequences that can be utilized for selectively manipulating the expression of nucleic acids and proteins in GABAergic neurons. This is particularly important for the use of viral vectors in gene therapy. In this Mini Review, we discuss the use of various gene regulatory elements for targeting GABAergic neurons, with an emphasis on adeno-associated viral vectors, the most widely used class of viral vectors for treating brain diseases.

Advances in the Development and the Applications of Nonviral, Episomal Vectors for Gene Therapy.

Nonviral and nonintegrating episomal vectors are reemerging as a valid, alternative technology to integrating viral vectors for gene therapy, due to their more favorable safety profile, significantly lower risk for insertional mutagenesis, and a lesser potential for innate immune reactions, in addition to their low production cost. Over the past few years, attempts have been made to generate highly functional nonviral vectors that display long-term maintenance within cells and promote more sustained gene expression relative to conventional plasmids. Extensive research into the parameters that stabilize the episomal DNA within dividing and nondividing cells has shed light into the genetic and epigenetic mechanisms that govern replication and transcription of episomal DNA within a mammalian nucleus in long-term cell culture. Episomal vectors based on scaffold/matrix attachment regions (S/MARs) do not integrate into the genomic DNA and address the serious problem of plasmid loss during mitosis by providing mitotic stability to established plasmids, which results in long-term transfection and transgene expression. The inclusion, in such vectors, of an origin of replication—initiation region—from the human genome has greatly enhanced their performance in primary cell culture. A number of vectors that function as episomes have arisen, which are either devoid or depleted of harmful CpG sequences and bacterial genes, and their effectiveness, as well as that of nonintegrating viral episomes, is enhanced when combined with S/MAR elements. As a result of these advances, an “S/MAR technology” has emerged for the production of efficient episomal vectors. Significant research continues in this field and innovations, in combination with promising systems based on nanoparticles and potentially combined with physical delivery methods, will enable the generation of optimized systems with scale-up and clinical application suitability utilizing episomal vectors.

SMA - TREATMENT: EP.283 Nusinersen in children with spinal muscular atrophy (SMA) who received onasemnogene abeparvovec: Design of the phase 4, open-label respond study

Nusinersen is an antisense oligonucleotide that has shown significant and clinically meaningful efficacy on motor function and survival endpoints across a broad spectrum of SMA phenotypes. Onasemnogene abeparvovec is an intravenous adeno-associated viral (AAV) vector gene therapy for SMA. Preclinical studies demonstrate incomplete transduction of neurons by the AAV9 vector. There have been reports of SMA patients receiving nusinersen after onasemnogene abeparvovec treatment; however, no systematic evaluation of clinical outcomes or treatment safety with nusinersen following onasemnogene abeparvovec has occurred.

Reversibly Modulating the Blood-Brain Barrier by Laser Stimulation of Molecular-Targeted Nanoparticles.

The blood-brain barrier (BBB) is highly selective and acts as the interface between the central nervous system and circulation. While the BBB is critical for maintaining brain homeostasis, it represents a formidable challenge for drug delivery. Here we synthesized gold nanoparticles (AuNPs) for targeting the tight junction specifically and demonstrated that transcranial picosecond laser stimulation of these AuNPs post intravenous injection increases the BBB permeability. The BBB permeability change can be graded by laser intensity, is entirely reversible, and involves increased paracellular diffusion. BBB modulation does not lead to significant disruption in the spontaneous vasomotion or the structure of the neurovascular unit. This strategy allows the entry of immunoglobulins and viral gene therapy vectors, as well as cargo-laden liposomes. We anticipate this nanotechnology to be useful for tissue regions that are accessible to light or fiberoptic application and to open new avenues for drug screening and therapeutic interventions in the central nervous system.

Quantitation of Trace Levels of DNA Released from Disrupted Adeno-Associated Virus Gene Therapy Vectors.

Adeno-associated virus (AAV) vectors for gene therapy have potential to provide a durable treatment response for a number of diseases with unmet need. DNA is released from AAV capsids at high temperatures. Less is known about DNA release that may occur under conditions relevant to clinical and commercial manufacturing, storage, and distribution. In this work we developed and applied a sensitive fluorescent dye-based method to quantitate trace levels of DNA released from AAV capsids. The method was used to characterize the impact of manufacturing process steps on the increase (up to 1.5%) and removal (down to 0.2%) of free DNA. Free DNA increased by 0.3% per day at 37°C and by 0.4% per freeze/thaw cycle in a phosphate-buffered saline formulation. When stored for 2 years at different temperatures, free DNA remained low (<0.6%) at both ≤ -60°C and at 2-8°C but was higher (2.6%) when the same sample was stored at -20°C. The dye-based method may be used to further characterize release of free DNA for different processes, formulations, and stress conditions. Overall, release of free DNA was a relatively minor degradation pathway under the conditions studied in this work.

Non-invasive gene delivery across the blood-brain barrier: present and future perspectives.

Non-invasive gene delivery across the blood-brain barrier: present and future perspectives.

Virotherapy in Germany-Recent Activities in Virus Engineering, Preclinical Development, and Clinical Studies.

Virotherapy research involves the development, exploration, and application of oncolytic viruses that combine direct killing of cancer cells by viral infection, replication, and spread (oncolysis) with indirect killing by induction of anti-tumor immune responses. Oncolytic viruses can also be engineered to genetically deliver therapeutic proteins for direct or indirect cancer cell killing. In this review—as part of the special edition on “State-of-the-Art Viral Vector Gene Therapy in Germany”—the German community of virotherapists provides an overview of their recent research activities that cover endeavors from screening and engineering viruses as oncolytic cancer therapeutics to their clinical translation in investigator-initiated and sponsored multi-center trials. Preclinical research explores multiple viral platforms, including new isolates, serotypes, or fitness mutants, and pursues unique approaches to engineer them towards increased safety, shielded or targeted delivery, selective or enhanced replication, improved immune activation, delivery of therapeutic proteins or RNA, and redirecting antiviral immunity for cancer cell killing. Moreover, several oncolytic virus-based combination therapies are under investigation. Clinical trials in Germany explore the safety and potency of virotherapeutics based on parvo-, vaccinia, herpes, measles, reo-, adeno-, vesicular stomatitis, and coxsackie viruses, including viruses encoding therapeutic proteins or combinations with immune checkpoint inhibitors. These research advances represent exciting vantage points for future endeavors of the German virotherapy community collectively aimed at the implementation of effective virotherapeutics in clinical oncology.

Improved functionality and potency of next generation BinMLV viral vectors toward safer gene therapy

To develop safer retroviral murine leukemia virus (MLV)-based vectors, we previously mutated and re-engineered the MLV integrase: the W390A mutation abolished the interaction with its cellular tethering factors, BET proteins, and a retargeting peptide (the chromodomain of the CBX1 protein) was fused C-terminally. The resulting BET-independent MLVW390A-CBX was shown to integrate efficiently and more randomly, away from typical retroviral markers. In this study, we assessed the functionality and stability of expression of the redistributed MLVW390A-CBX vector in more depth, and evaluated safety using a clinically more relevant vector design encompassing a self-inactivated (SIN) LTR and a weak internal elongation factor 1α short (EFS) promoter. MLVW390A-CBX-EFS produced like MLVWT and efficiently transduced laboratory cells and primary human CD34+ hematopoetic stem cells (HSC) without transgene silencing over time, while displaying a more preferred, redistributed, and safer integration pattern. In a human mesoangioblast (MAB) stem cell model, the myogenic fusion capacity was hindered following MLVWT transduction, while this remained unaffected when applying MLVW390A-CBX. Likewise, smooth muscle cell differentiation of MABs was unaltered by MLVW390A-CBX-EFS. Taken together, our results underscore the potential of MLVW390A-CBX-EFS as a clinically relevant viral vector for ex-vivo gene therapy, combining efficient production with a preferable integration site distribution profile and stable expression over time.

Predicting genotoxicity of viral vectors for stem cell gene therapy using gene expression-based machine learning

Hematopoietic stem cell gene therapy is emerging as a promising therapeutic strategy for many diseases of the blood and immune system. However, several individuals who underwent gene therapy in different trials developed hematological malignancies caused by insertional mutagenesis. Preclinical assessment of vector safety remains challenging because there are few reliable assays to screen for potential insertional mutagenesis effects invitro. Here we demonstrate that genotoxic vectors induce a unique gene expression signature linked to stemness and oncogenesis in transduced murine hematopoietic stem and progenitor cells. Based on this finding, we developed the surrogate assay for genotoxicity assessment (SAGA). SAGA classifies integrating retroviral vectors using machine learning to detect this gene expression signature during the course of invitro immortalization. On a set of benchmark vectors with known genotoxic potential, SAGA achieved an accuracy of 90.9%. SAGA is more robust and sensitive and faster than previous assays and reliably predicts a mutagenic risk for vectors that led to leukemic severe adverse events in clinical trials. Our work provides a fast and robust tool for preclinical risk assessment of gene therapy vectors, potentially paving the way for safer gene therapy trials.

Current status and future perspectives of rare disease research.

Rare diseases refer to diseases with low incidence. Currently, there are over 8000 rare diseases in the world. Effective prevention and treatment of rare diseases is an important part of 'healthy China'. In this paper, status and drug development of rare diseases were reported. These results indicate that research on rare diseases is growing rapidly driven by technology and policy. The hotspots include the identification of gene mutations, the development of therapies, and the key points of technology include the development of drugs for rare diseases, the development of viral vectors for gene therapy, and the diagnosis and management system for rare diseases. In terms of drug development, 880 drugs have been launched by December 28, 2020, and a large number of drugs are in the pre-clinical stage. Generally, a new technology or drug is applicable to various diseases. In the future, with policy support and the development of emerging technologies such as gene editing, more and more rare diseases will be diagnosed and intervened early, even be cured, and the quality of life of patients is expected to be improved.

Adeno-associated viral (AAV) vector-mediated therapeutics for diabetic cardiomyopathy - current and future perspectives.

Diabetes increases the prevalence of heart failure by 6–8-fold, independent of other comorbidities such as hypertension and coronary artery disease, a phenomenon termed diabetic cardiomyopathy. Several key signalling pathways have been identified that drive the pathological changes associated with diabetes-induced heart failure. This has led to the development of multiple pharmacological agents that are currently available for clinical use. While fairly effective at delaying disease progression, these treatments do not reverse the cardiac damage associated with diabetes. One potential alternative avenue for targeting diabetes-induced heart failure is the use of adeno-associated viral vector (AAV) gene therapy, which has shown great versatility in a multitude of disease settings. AAV gene therapy has the potential to target specific cells or tissues, has a low host immune response and has the possibility to represent a lifelong cure, not possible with current conventional pharmacotherapies. In this review, we will assess the therapeutic potential of AAV gene therapy as a treatment for diabetic cardiomyopathy.

Emerging Immunogenicity and Genotoxicity Considerations of Adeno-Associated Virus Vector Gene Therapy for Hemophilia.

Adeno-associated viral (AAV) vector gene therapy has shown promise as a possible cure for hemophilia. However, immune responses directed against AAV vectors remain a hurdle to the broader use of this gene transfer platform. Both innate and adaptive immune responses can affect the safety and efficacy of AAV vector–mediated gene transfer in humans. These immune responses may be triggered by the viral capsid, the vector’s nucleic acid payload, or other vector contaminants or excipients, or by the transgene product encoded by the vector itself. Various preclinical and clinical strategies have been explored to overcome the issues of AAV vector immunogenicity and transgene-related immune responses. Although results of these strategies are encouraging, more efficient approaches are needed to deliver safe, predictable, and durable outcomes for people with hemophilia. In addition to durability, long-term follow-up of gene therapy trial participants will allow us to address potential safety concerns related to vector integration. Herein, we describe the challenges with current methodologies to deliver optimal outcomes for people with hemophilia who choose to undergo AAV vector gene therapy and the potential opportunities to improve on the results.

Treating of focal epilepsy: a patent review.

Focal epilepsy is one of the most frequent specific type of epilepsies, with 30% treatment-resistant patients. There are several directions researchers can follow to improve existing treatment of focal epilepsy: synthesis of new compounds with anticonvulsant activity, repurposing drugs approved for other indications, finding drugs targeted to specific genetic and biochemical defects that underlie focal epilepsy syndromes, development of viral vectors for specific gene therapy, creation of devices and methods for suppression of seizures by electrostimulation and development of methods to increase safety of epilepsy surgery. Improvement of efficacy and safety of current therapies is necessary, as well as developing targeted treatment of genetic epilepsy syndromes that will not only suppress seizures, but stop further epileptogenesis.

Use of Gene Therapy in Retinal Ganglion Cell Neuroprotection: Current Concepts and Future Directions.

We systematically reviewed published translational research on gene-based therapy for retinal ganglion cell (RGC) neuroprotection. A search was conducted on Entrez PubMed on 23 December 2020 using the keywords “gene therapy”, “retinal ganglion cell” and “neuroprotection”. The initial search yielded 82 relevant articles. After restricting publications to those with full text available and in the English language, and then curating for only original articles on gene-based therapy, the final yield was 18 relevant articles. From the 18 papers, 17 of the papers utilized an adeno-associated viral (AAV) vector for gene therapy encoding specific genes of interest. Specifically, six of the studies utilized an AAV vector encoding brain-derived neurotrophic factor (BDNF), two of the studies utilized an AAV vector encoding erythropoietin (EPO), the remaining 10 papers utilized AAV vectors encoding different genes and one microRNA study. Although the literature shows promising results in both in vivo and in vitro models, there is still a significant way to go before gene-based therapy for RGC neuroprotection can proceed to clinical trials. Namely, the models of injury in many of the studies were more acute in nature, unlike the more progressive and neurodegenerative pathophysiology of diseases, such as glaucoma. The regulation of gene expression is also highly unexplored despite the use of AAV vectors in the majority of the studies reviewed. It is also expected that with the successful launch of messenger ribonucleic acid (mRNA)-based vaccinations in 2020, we will see a shift towards this technology for gene-based therapy in glaucoma neuroprotection.

Adenovirus Core Proteins: Structure and Function.

Adenoviruses have served as a model for investigating viral-cell interactions and discovering different cellular processes, such as RNA splicing and DNA replication. In addition, the development and evaluation of adenoviruses as the viral vectors for vaccination and gene therapy has led to detailed investigations about adenovirus biology, including the structure and function of the adenovirus encoded proteins. While the determination of the structure and function of the viral capsid proteins in adenovirus biology has been the subject of numerous reports, the last few years have seen increased interest in elucidating the structure and function of the adenovirus core proteins. Here, we provide a review of research about the structure and function of the adenovirus core proteins in adenovirus biology.

Synthetic Biology: Emerging Concepts to Design and Advance Adeno-Associated Viral Vectors for Gene Therapy.

Three recent approvals and over 100 ongoing clinical trials make adeno‐associated virus (AAV)‐based vectors the leading gene delivery vehicles in gene therapy. Pharmaceutical companies are investing in this small and nonpathogenic gene shuttle to increase the therapeutic portfolios within the coming years. This prospect of marking a new era in gene therapy has fostered both investigations of the fundamental AAV biology as well as engineering studies to enhance delivery vehicles. Driven by the high clinical potential, a new generation of synthetic‐biologically engineered AAV vectors is on the rise. Concepts from synthetic biology enable the control and fine‐tuning of vector function at different stages of cellular transduction and gene expression. It is anticipated that the emerging field of synthetic‐biologically engineered AAV vectors can shape future gene therapeutic approaches and thus the design of tomorrow's gene delivery vectors. This review describes and discusses the recent trends in capsid and vector genome engineering, with particular emphasis on synthetic‐biological approaches.

Biosecurity risks associated with vaccine platform technologies

Vaccine platforms have been critical for accelerating the timeline of COVID-19 vaccine development. Faster vaccine timelines demand further development of these technologies. Currently investigated platform approaches include virally vectored and RNA-based vaccines, as well as DNA vaccines and recombinant protein expression system platforms, each featuring different advantages and challenges. Viral vector-based and DNA vaccines in particular have received a large share of research funding to date. Platform vaccine technologies may feature dual-use potential through informing or enabling pathogen engineering, which may raise the risk for the occurrence of deliberate, anthropogenic biological events. Research on virally vectored vaccines exhibits relatively high dual-use potential for two reasons. First, development of virally vectored vaccines may generate insights of particular dual-use concern such as techniques for circumventing pre-existing anti-vector immunity. Second, while the amount of work on viral vectors for gene therapy exceeds that for vaccine research, work on virally vectored vaccines may increase the number of individuals capable of engineering viruses of particular concern, such as ones closely related to smallpox. Other platform vaccine approaches, such as RNA vaccines, feature relatively little dual-use potential. The biosecurity risk associated with platform advancement may be minimised by focusing preferentially on circumventing anti-vector immunity with non-genetic rather than genetic modifications, using vectors that are not based on viruses pathogenic to humans, or preferential investment into promising RNA-based vaccine approaches. To reduce the risk of anthropogenic pandemics, structures for the governance of biotechnology and life science research with dual-use potential need to be reworked. Scientists outside of the pathogen research community, for instance those who work on viral vectors or oncolytic viruses, need to become more aware of the dual-use risks associated with their research. Both public and private research-funding bodies need to prioritise the evaluation and reduction of biosecurity risks.

Viral vector production process intensification: analytics, automation, in-line testing and more

<div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://cdn.insights.bio/uploads/888145b9bcb9494d9523fe80a135ed5f.jpg" data-image="1"></div><div class="author-det"><h3 class="author-name">Susan D’Costa</h3><h5 class="author-title">Senior Director, Technical Program Design, Viral Vector Services, Thermo Fisher Scientific</h5> In her current role, Susan functions as SME for VVS’ viral vector manufacturing platforms and systems providing scientific and technical input for customer programs. Prior to this role, she served as the Head of Process and Analytical Development at Viral Vector Services, Thermo Fisher Scientific, formerly Brammer Bio for over three years. In her role as head of PD/ADA, she provided critical scientific input for projects developed and manufactured at VVS. She has built a robust team for the development, customization, optimization, scale-up and tech transfer of gene therapy vector process and analytics. Susan was also integral to developing robust QC analytics for incoming starting and raw materials and for the release of the clinical vector products in her role as Director of Quality Control at Brammer Bio/Florida Biologix. </div></div></div><div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://cdn.insights.bio/uploads/1b65fe190645414eb14a9f6b56f12cbf.jpg" data-image="1"></div><div class="author-det"><h3 class="author-name">Mike Delahaye</h3><h5 class="author-title">Head of Viral Vector Industrialisation, Cell and Gene Therapy Catapult</h5> Michael has almost 15 years of industrial experience within the cell and gene therapy sector. He leads a team of experienced scientists within the Viral Gene Delivery programme, responsible for managing the developmental output of the group within collaborative, commercial and supporting R&amp;D operations. The team’s key focus is the development and delivery of robust manufacturing processes, supported by rapid, high resolution characterisation tools to facilitate the production of AAV based gene therapies. His team is also supporting the development of new adaptive manufacturing approaches by integrating technologies to allow real-time product monitoring and enable feedback control during product manufacture. </div></div></div><div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://cdn.insights.bio/uploads/f89a9bee7b7f422f90e20f14ed51c093.jpg" data-image="1"></div><div class="author-det"><h3 class="author-name">Michael White</h3><h5 class="author-title">Senior Scientist, ‎Affinia Therapeutics</h5> Michael is the Head of Viral Vector Industrialisation at the Cell and Gene Therapy Catapult and has almost 15 years of industrial experience within the cell and gene therapy sector. He leads a team of experienced scientists within the Viral Gene Delivery programme, responsible for managing the developmental output of the group within collaborative, commercial and supporting R&amp;D operations. The team’s key focus is the development and delivery of robust manufacturing processes, supported by rapid, high resolution characterisation tools to facilitate the production of AAV based gene therapies. His team is also supporting the development of new adaptive manufacturing approaches by integrating technologies to allow real-time product monitoring and enable feedback control during product manufacture. </div></div></div><div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://cdn.insights.bio/uploads/776b16a7bc2e4fbfbe681c777fe42fcd.jpg" data-image="1"></div><div class="author-det"><h3 class="author-name">Franz Gerner</h3><h5 class="author-title">Vice President, Technical Operations, Sio Gene Therapies</h5> Franz Gerner is responsible for process development, manufacturing and analytical activities, including overseeing outsourced activities at CDMOs and CTOs. Prior to joining Sio Gene Therapies, Franz worked at Regenxbio, joining the company at an early stage and building up the Process Development team over the course of 5 years. He started to work in the AAV gene therapy field about 25 years ago. </div></div></div><div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://cdn.insights.bio/uploads/c0e2ab70fb724206bfe9ddbb85d6b59f.jpg" data-image="1"></div><div class="author-det"><h3 class="author-name">Jessica Tate</h3><h5 class="author-title">Head of Science &amp; Technology Development, Viral Vector Services, Thermo Fisher Scientific</h5> Jessica Tate has spent the last 15 years producing, purifying, and characterizing various virus modalities, in a combination of industry and academic environments. Currently she leads Thermo Fisher Scientific’s Viral Vector Science and Technology team, who’s mission is to develop and/or employ novel state-of-the-art technologies in the manufacturing of viral vector gene therapies. </div></div></div><div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://cdn.insights.bio/uploads/23d387b3f3674a78b57c369bcbcdf517.jpg" data-image="1"></div><div class="author-det"><h3 class="author-name">Jim Warren</h3><h5 class="author-title">Vice President, Pharmaceutical Development, Ultragenyx Pharmaceutical Inc.</h5> Dr. Warren has 27 years of experience in the pharmaceutical and biotechnology industry. At Ultragenyx, he leads a team of over 60 scientists and engineers, responsible for all early and late stage Process and Analytical Development of viral vector gene therapy products as well as Pilot Scale Manufacturing in the Woburn, MA Pilot Plant. Before coming to Ultragenyx Jim held senior CMC leadership positions at Homology Medicines, bluebird bio, and Shire. Earlier in his career, Jim spent 16 years at Merck &amp; Co., Inc., where he led process development, technology transfer, and manufacturing sciences teams responsible for development of several clinical vector and vaccine candidates and the licensure of multiple commercial vaccines (RotaTeq®, Varivax®, ProQuad®, and Zostavax®). </div></div></div>