Viral Gene Therapy Research Articles

Regulatory Trends in the Nonclinical Development of Viral Vector-Based Gene Therapies: A Benchmark Analysis of Approved Products

As it is often the case with innovative technologies, regulatory agencies are highly demanding in product safety demonstration from those pioneering breakthrough therapy products. Since the first historically approved gene therapy medicinal product (Gencidine in 2003) by the Chinese National Medicinal Products Administration, gene therapy medicinal products have slowly been emerging in other regions, as illustrated by the first European-approved gene therapy medicinal product (Glybera in 2012) and the first US-approved product (Imlygic in 2015). From then, with the rise of new molecular technologies (e.g., non-viral and viral vector systems), an exponential growth of gene therapies development could be gauged with, for example, the approval of more than thirty gene therapies between 2016-2022. Using a method based on Preferred Reporting Items for Systematic reviews and Meta-Analyses principle, throughout different literature databases, this review is restricted to the evaluation of viral vector-based gene therapy medicinal products (VV-GTMPs). It also considered relevant guidelines and public assessment reports issued by the EMA and / or the FDA on the products these agencies approved. Then, a benchmark was performed to help stakeholders to identify regulatory trends and to design appropriate nonclinical programs establishing the benefit / risk ratio for patients to be enrolled in clinical trials. The analysis was focused on the nonclinical activities (pharmacology, biodistribution / persistence / shedding, and toxicology) performed by Applicants / Sponsors. As of 30 March 2023, 18 VV-GTMPs have been authorized by the EMA and 14 by the FDA to treat either orphan diseases or limited number of oncology patients. The majority of these therapies are based on adeno-associated or retroviral viruses (often lentiviruses able to transfect hematopoietic CD34+ cells or T-cells). Based on an analysis of the ongoing clinical trials, there is now a trend for developing gene therapies for larger patient populations. In conclusion, given the VV-GTMPs diversity and targeted indications, a “one-size fits all” nonclinical development plan cannot be considered by default. Instead, individual, risk-based, tailored nonclinical development programs appear more appropriate to assess such products, taking into consideration the lessons learned from the past. In such fast-evolving environment, regulatory agencies need to adapt their evaluation process very rapidly.

Scale-Up of Protein Purification: Downstream Processing Issues.

Large-scale chromatography operations continue to occupy the central position in the overall strategy for downstream processing and purification of therapeutic protein products for human use. As the biopharmaceutical industry looks forward to embracing new therapeutic modalities such as viral vector-mediated gene therapy, it is becoming evident that chromatographic separations will be also be crucial for success in that discipline. The current industry focus on cell culture intensification strategies that can result in increased process efficiency and lower cost of goods is presenting challenges to the robustness and economics of chromatography processes. To ensure robust and reproducible commercial manufacturing strategies, there is always a mandate to increase the scale of chromatography unit operations that are typically developed and optimized in small-scale development trials. This chapter discusses the key factors in typical chromatography operations that need to be carefully considered and modeled during the process scale-up phase in order to maintain the purity, yield, and quality of a product purified at smaller scales.

Visualizing advances in the future of primate neuroscience research.

Future neuroscience and biomedical projects involving non-human primates (NHPs) remain essential in our endeavors to understand the complexities and functioning of the mammalian central nervous system. In so doing, the NHP neuroscience researcher must be allowed to incorporate state-of-the-art technologies, including the use of novel viral vectors, gene therapy and transgenic approaches to answer continuing and emerging research questions that can only be addressed in NHP research models. This perspective piece captures these emerging technologies and some specific research questions they can address. At the same time, we highlight some current caveats to global NHP research and collaborations including the lack of common ethical and regulatory frameworks for NHP research, the limitations involving animal transportation and exports, and the ongoing influence of activist groups opposed to NHP research.

Viral vector manufacturing process: addressing bottlenecks with innovative solutions

With increasing approvals of viral vector-based gene therapies, the industry is shifting its focus to the expansion of viral vector manufacturing to meet the demands of the growing number of therapies on the market. Continuous improvements in the efficiency of viral vector production, as well as optimization of complex bioproduction processes, are essential to meet demand and get lifesaving therapies to patients quickly. This must be carefully balanced with consistency and quality of the final product. In this article, multiple applications and technologies to address current manufacturing challenges and solutions to increase overall viral vector yield throughout development will be explored. Case studies will be presented to demonstrate the progress associated with process intensification and optimization from benchtop development to large-scale commercial manufacturing.

Generation of Human iPSC-Derived Retinal Organoids for Assessment of AAV-Mediated Gene Delivery.

Human retinal organoids derived from induced pluripotent stem cells (iPSCs) serve as a promising preclinical model for testing the safety and efficacy of viral gene therapy. Retinal organoids recapitulate the stratified multilayered epithelium structure of the developing and maturating human retina. As such, retinal organoids are unique tools to model retinal disease and to test therapeutic interventions toward their amelioration. Here, we describe a method for the generation of human iPSC-derived retinal organoids and how they can be utilized for the assessment of recombinant adeno-associated viral (rAAV)-mediated gene delivery.

Overcoming Barriers to Preventing and Treating P. aeruginosa Infections Using AAV Vectored Immunoprophylaxis.

Pseudomonas aeruginosa is a bacterial pathogen of global concern and is responsible for 10-15% of nosocomial infections worldwide. This opportunistic bacterial pathogen is known to cause serious complications in immunocompromised patients and is notably the leading cause of morbidity and mortality in patients suffering from cystic fibrosis. Currently, the only line of defense against P. aeruginosa infections is antibiotic treatment. Due to the acquired and adaptive resistance mechanisms of this pathogen, the prevalence of multidrug resistant P. aeruginosa strains has increased, presenting a major problem in healthcare settings. To date, there are no approved licensed vaccines to protect against P. aeruginosa infections, prompting the urgent need alternative treatment options. An alternative to traditional vaccines is vectored immunoprophylaxis (VIP), which utilizes a safe and effective adeno-associated virus (AAV) gene therapy vector to produce sustained levels of therapeutic monoclonal antibodies (mAbs) in vivo from a single intramuscular injection. In this review, we will provide an overview of P. aeruginosa biology and key mechanisms of pathogenesis, discuss current and emerging treatment strategies for P. aeruginosa infections and highlight AAV-VIP as a promising novel therapeutic platform.

New strategies that can be neuroprotective

AbstractGlaucoma is considered a neurodegenerative disease and shares some common mechanisms with other neurodegenerative diseases. Therefore, research into the triggers and drivers of neurodegeneration can identify novel areas of therapeutic intervention to preserve and restore vision. Neuroprotection in glaucoma is focused on preserving the neuronal structure and/or function. Currently, lowering of intraocular pressure (IOP) is the only clinically proven neuroprotective strategy. Alternatives to IOP‐lowering approach can be grouped into targets that interfere with excitotoxicity, oxidative stress and mitochondrial dysfunction, inflammation‐abnormal immune response, glial cell modulation, and stem cell therapy. However, any division is arbitrary as most targets are involved in several pathways and/or mechanism of action are incompletely understood. Many agents have shown neuroprotective effect in glaucoma research models but translation into well‐designed human trials and clinical practice represents a major challenge. Several compounds with antioxidant function including vitamin E, C, flavonoids, coenzyme Q10, and citicoline have shown neuroprotective effect in neurodegenerative diseases. Recently, oral nicotinamide supplementation has led to a short‐term improvement of inner retinal function in glaucoma patients. Immune system modulation such as blocking selectively excessive TNF‐alpha and targeting antibodies against ϒ‐Synuclein may prove beneficial. Recently, the receptor agonists of the incretin hormone glucagon‐like‐peptide‐1 (GLP‐1), used for the treatment of diabetes, have shown neuroprotective effects in preclinical and clinical studies on neurodegenerative diseases in both the brain and the retina. Platelet‐derived growth factor and ciliary neurotrophic factor (CNTF) protect cells from neurodegeneration and phase I studies using intraocular implants with slow CNTF release are ongoing. Intravitreal administration of mesenchymal stromal stem cells has shown neuroprotective effect. Gene therapy in glaucoma is still in preclinical phase. A novel adeno‐associated viral vector gene therapy increased production of brain‐derived neurotrophic factor and its receptor and had neuroprotective effect over several months. Altered levels of microRNAs, small non‐coding RNAs involved in post transcriptional regulation of gene expression, were found to be implicated in retinal ganglion cell apoptosis in glaucoma. MicroRNAs may become a novel neuroprotective strategy.

Emerging Perspectives on Gene Therapy Delivery for Neurodegenerative and Neuromuscular Disorders.

Neurodegenerative disorders (NDDs), such as Alzheimer's disease (AD) and Parkinson's Disease (PD), are a group of heterogeneous diseases that mainly affect central nervous system (CNS) functions. A subset of NDDs exhibit CNS dysfunction and muscle degeneration, as observed in Gangliosidosis 1 (GM1) and late stages of PD. Neuromuscular disorders (NMDs) are a group of diseases in which patients show primary progressive muscle weaknesses, including Duchenne Muscular Dystrophy (DMD), Pompe disease, and Spinal Muscular Atrophy (SMA). NDDs and NMDs typically have a genetic component, which affects the physiological functioning of critical cellular processes, leading to pathogenesis. Currently, there is no cure or efficient treatment for most of these diseases. More than 200 clinical trials have been completed or are currently underway in order to establish safety, tolerability, and efficacy of promising gene therapy approaches. Thus, gene therapy-based therapeutics, including viral or non-viral delivery, are very appealing for the treatment of NDDs and NMDs. In particular, adeno-associated viral vectors (AAV) are an attractive option for gene therapy for NDDs and NMDs. However, limitations have been identified after systemic delivery, including the suboptimal capacity of these therapies to traverse the blood-brain barrier (BBB), degradation of the particles during the delivery, high reactivity of the patient's immune system during the treatment, and the potential need for redosing. To circumvent these limitations, several preclinical and clinical studies have suggested intrathecal (IT) delivery to target the CNS and peripheral organs via cerebrospinal fluid (CSF). CSF administration can vastly improve the delivery of small molecules and drugs to the brain and spinal cord as compared to systemic delivery. Here, we review AAV biology and vector design elements, different therapeutic routes of administration, and highlight CSF delivery as an attractive route of administration. We discuss the different aspects of neuromuscular and neurodegenerative diseases, such as pathogenesis, the landscape of mutations, and the biological processes associated with the disease. We also describe the hallmarks of NDDs and NMDs as well as discuss current therapeutic approaches and clinical progress in viral and non-viral gene therapy and enzyme replacement strategies for those diseases.

MiRNA Pathway Alteration in Response to Non-Coding RNA Delivery in Viral Vector-Based Gene Therapy

Gene therapy is widely used to treat incurable disorders and has become a routine procedure in clinical practice. Since viruses can exhibit specific tropisms, effectively penetrate the cell, and are easy to use, most gene therapy approaches are based on viral delivery of genetic material. However, viral vectors have some disadvantages, such as immune response and cytotoxicity induced by a disturbance of cell metabolism, including miRNA pathways that are an important part of transcription regulation. Therefore, any viral-based gene therapy approach involves the evaluation of side effects and safety. It is possible for such effects to be caused either by the viral vectors themselves or by the delivered genetic material. Many gene therapy techniques use non-coding RNA delivery as an effective agent for gene expression regulation, with the risk of cellular miRNA pathways being affected due to the nature of the non-coding RNAs. This review describes the effect of viral vector entry and non-coding RNA delivery by these vectors on miRNA signaling pathways.

The Effects of Immunomodulation with Corticosteroids to Manage an AAV Capsid Immune response in the Phase I/II Study of SPK-8011

Background: Hemophilia A (HA) is an inherited blood disorder caused by deficiency or dysfunction of coagulation factor VIII (FVIII). SPK-8011 is an adeno-associated viral (AAV) vector gene therapy targeting hepatocyte expression of FVIII, aiming to provide durable FVIII expression and long-term bleed prevention. A Phase I/II trial of SPK-8011 (NCT03003533/NCT03432520) has demonstrated multiyear sustained FVIII expression and notably reduced bleeding in people with HA, with no major safety concerns. There are challenges around preventing and managing cellular immune responses to transduced hepatocytes. Here, we present the outcomes of participants who received corticosteroids following vector administration to prevent and/or treat a presumed AAV capsid immune response. Methods: In this open-label, multicenter, non-randomized, dose-escalation trial, people with HA were infused with SPK-8011 at one of four doses ranging from 5×1011 to 2×1012 vg/kg (full methods published in George et al. New Engl J Med 2021). Participants had baseline FVIII activity of ≤2% of normal levels and were negative for neutralizing antibodies to SPK200. Participants were monitored for 52 weeks after vector administration and enrolled in a 4-year long-term follow-up trial. Corticosteroids were used reactively at the investigators’ discretion upon a presumed capsid immune response, i.e., decrease in FVIII expression, increase in alanine aminotransferase (ALT) level, and/or positive peripheral blood mononuclear cells using interferon-γ enzyme-linked immunospot (ELISpot) to SPK200 peptides. Following loss of FVIII expression in two participants, a prophylactic regimen was explored. Assessments included duration of corticosteroid use and associated adverse events (AEs). Results: Twenty-three males with HA were dosed with SPK-8011 and 17 received corticosteroids (12 reactively, 5 prophylactically); five did not have evidence of a capsid immune response, and one remains in the window of a capsid immune response in the follow-up period (data cut-off: 30 Jun 2022). The median (range) time to initiation of reactive corticosteroids was 9.3 (4.3-12.1) weeks post vector infusion in the 12 participants, with a median (range) duration of treatment of 8.5 (2-18) weeks. Two of these 12 participants completely lost FVIII expression following a presumed capsid immune response (one initiated emicizumab; one resumed FVIII prophylaxis); FVIII expression was maintained in the remaining 10 participants. Corticosteroids were administered prophylactically (2-4 weeks post vector) in five participants, with transgene expression maintained in all five. In four of these five participants, length of exposure was prolonged (31-49 weeks), with attempted corticosteroid tapering resulting in decreased FVIII expression, increased ALT and/or positive ELISpot assays outside the typical window of capsid immune responses. Four participants had AEs related to corticosteroid therapy (Table), with weight gain (8.7%; n=2) and insomnia (8.7%; n=2) being the most common. The occurrence of AEs attributed to corticosteroids increased with duration of use, particularly in those with exposure of >30 weeks. Prophylactic corticosteroids did not consistently prevent a presumed capsid immune response in these five participants and four experienced prolonged courses of corticosteroids necessitating steroid-sparing agents (Figure). All five participants who received prophylactic corticosteroids and four participants who received reactive corticosteroids experienced a recurrence of one or more laboratory trigger(s) potentially linked to a presumed capsid immune response during their corticosteroid taper. Subsequent increased corticosteroid use did not consistently resolve these laboratory changes. Conclusions: Overcoming the challenge of capsid immune responses to achieve long-term stable and predictable FVIII expression remains a goal of AAV gene transfer for HA. Reactive oral corticosteroids were well tolerated but did not prevent loss of FVIII expression in all participants. Early prophylactic corticosteroids did not consistently prevent presumed capsid immune responses and resulted in prolonged immunomodulatory courses with associated AEs. Data so far have permitted refinement of laboratory triggers and investigation is ongoing to identify an alternative, safe and optimal immunomodulatory regimen. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Vector Analysis of Multicentric Lymphoma in a Severe Hemophilia Α Dog after AAV Gene Therapy

Background Adeno-associated viral (AAV) vector gene therapy for severe hemophilia A (HA) is approaching a clinical reality with multiple successful clinical trials. Despite this success, questions remain about the long-term safety of AAV vectors, especially regarding genomic integration and resulting oncogenesis. Studies of neonatal mice have demonstrated AAV integrations that drive hepatocellular carcinoma formation (Donsante et al. Science, 2007). Studies in HA canine models have also demonstrated AAV integrations and clonal expansion of hepatocytes with integrated vector genomes, but no evidence of tumor formation (Nguyen et al. Nat Biotechnol, 2021). Additionally, three tumors have been reported in AAV gene therapy recipients with HA or hemophilia B in clinical trials, without evidence of vector integrations driving oncogenesis. Though overall reassuring, these data highlight that the field needs to remain vigilant about the possibility of AAV integrations driving cancer development. Thus, the assessment of tumors in gene therapy recipients remains important for the AAV field. Aims To determine the role of AAV vector in the development of multicentric lymphoma in a severe HA dog that received liver-directed gene therapy. Methods Vector genome copy numbers in relevant tissues were determined by real-time PCR with primers situated in the 3'-end of the promoter and the 5'- end of the transgene. The vector copy number was calculated by comparing the analyte amplification signal against a standard curve of the plasmid DNA. Results A privately owned mixed-breed dog (PC9) with a history of recurrent spontaneous bleeding events presented with canine factor VIII (cFVIII) levels <1% normal, consistent with severe HA. At 9-months of age, he received liver-directed AAV8 gene therapy with a high-expressing canine factor FVIII (cFVIII-ΔF/V3) variant transgene at a dose of 6 x 1012 vg/kg via intravenous administration. Following gene therapy, his cFVIII levels increased to 2-3% normal and remained stable through duration of follow-up. His annualized bleeding rate decreased from 8 pre-gene therapy to 0 post-gene therapy. At 3.5 years after vector administration, PC9 was diagnosed with a widely disseminated cancer and euthanized due to complications of the disease. At autopsy, he was diagnosed with multicentric lymphoma involving peripheral and visceral lymph nodes, spleen, liver, and lungs. The average age of lymphoma diagnosis in dogs is between 6-9 years of age (Edwards et al. Vet Comp Oncol, 2003), so the development of cancer at an early age in a gene therapy recipient warranted additional study. Vector copy number analysis showed that the liver had the highest levels of AAV vector genomes, as expected. Liver samples showed a heterogenous distribution of vector genomes, consistent with previous studies of AAV8 transduction (Bell et al. Hum Gene Ther, 2011). Splenic samples also had a high level of AAV vector genomes, which again is consistent with known targeting of AAV8. Importantly, the lymph nodes had no detectable AAV vector genomes present, suggesting that vector integration could not contribute to lymphoma development. cFVIII levels remained stable before and after diagnosis of lymphoma, supporting lack of vector integration in the malignant cells. Conclusions AAV gene therapy resulted in a 100% reduction in the annualized bleeding rate in this pet dog with severe HA. Furthermore, the multicentric lymphoma that developed 3.5 years after liver-directed gene therapy is unlikely related to the AAV vector. We are unable to rule out other factors that may have contributed, including environmental influences or genetic predispositions for lymphoma. These results support the ongoing efforts to treat HA with AAV-based gene therapy and reinforce the safety profile of AAV vectors outside of a laboratory environment.

Abstract 13927: AAV Gene Therapy to Treat Underlying Cardiac Biomechanical Defects in Lmna Dilated Cardiomyopathy Improves Lifespan and Preserves Ejection Fraction in Lmna DCM Mouse Model

Mutations in the LMNA gene are the second most common cause of genetic dilated cardiomyopathies (DCMs) with a prevalence of ~1/12500. Adeno-associated virus (AAV) gene therapies are a promising treatment modality for genetic disease. However, the autosomal dominant, gain-of-function mutations underlying LMNA DCM preclude standard gene replacement approaches. To understand LMNA DCM, we previously generated a mouse model that exhibits reduced ejection fraction, dilation of ventricular inner dimensions and increased cardiac fibrosis, surviving for only ~40 days after cardiac-specific deletion of the Lmna gene. We propose that the mutant LMNA gene weakens the structural integrity of the nucleus, making it vulnerable to biomechanical forces generated by contracting cardiomyocytes, which ultimately results in nuclear damage and a decline in cardiac function. Our gene therapy, AAV9-cTnT-GSLA01, prevents nuclear damage and disease in our Lmna DCM model by reducing biomechanical forces transmitted to the nucleus. To determine if we can treat, rather than prevent, Lmna DCM, we injected animals with AAV9-cTnT-GSLA01 at 1x10 14 vg/kg at different timepoints (21, 17, 14 and 1 day(s)) after induction of Lmna deletion. Treatment with AAV9-cTnT-GSLA01 17 days post Lmna deletion resulted in lifespan extension to 108 days (P= 0.0002), while earlier intervention at day 14 or day 1, improved lifespan to 122 and 208 days respectively (P = 0.0002, P= 0.0035). To address dose dependency of AAV9-cTnT-GSLA01, we delivered the vector at 5x10 13 vg/kg, 1x10 14 vg/kg, and 2x10 14 vg/kg at 17 days after Lmna deletion. Lifespan was extended from 40 days in untreated mice to 51.5 (P = 0.0135), 67.5 (P &lt; 0.0001), and 103.5 days (P &lt; 0.0001) respectively. The progressive decline of ejection fraction in these mice was attenuated in a dose-dependent manner. Thus, the positive effect of AAV9-cTnT-GSLA01 on lifespan and cardiac function in Lmna DCM mice is enhanced with increasing dose and transgene expression. Initial optimisation of the therapeutic expression cassette appears to improve lifespan extension significantly. AAV9-cTnT-GSLA01 is a novel gene therapy approach that promises to address the underlying cause of LMNA DCM.

Prostaglandin-based rAAV-mediated glaucoma gene therapy in Brown Norway rats

Prostaglandin analogs are first-line treatments for open angle glaucoma and while effective at lowering intraocular pressure, they are undermined by patient non-compliance, causing atrophy of the optic nerve and severe visual impairment. Herein, we evaluate the safety and efficacy of a recombinant adeno-associated viral vector-mediated gene therapy aimed at permanently lowering intraocular pressure through de novo biosynthesis of prostaglandin F2α within the anterior chamber. This study demonstrated a dose dependent reduction in intraocular pressure in normotensive Brown Norway rats maintained over 12-months. Crucially, therapy could be temporarily halted through off-type riboswitch activation, reverting intraocular pressure to normal. Longitudinal multimodal imaging, electrophysiology, and post-mortem histology revealed the therapy was well tolerated at low and medium doses, with no major adverse effects to anterior chamber health, offering a promising alternative to current treatment strategies leading to clinically relevant reductions in intraocular pressure without the need for adherence to a daily treatment regimen.

LBSUN178 Teniposide Improves Adeno-associated Virus-mediated Insulin Gene Therapy In Diabetic Mice.

Abstract Type 1 Diabetes Mellitus (T1DM) results from the autoimmune destruction of insulin-producing pancreatic β cells. Despite advances in our understanding of the pathogenesis and management of diabetes, as well as treatment options, which primarily include injectable insulin and whole pancreas transplant, these advancements remain unsatisfactory, with only a small percentage of patients achieving their glycemic goals. Insulin gene therapy refers to the development of β cell substitutes by introducing an insulin producing gene into endogenous cell populations that do not normally produce insulin. This strategy has the promise to overcome the limitations of current treatments. Adeno-associated viral (AAV) vector-based gene therapy holds great promise for the treatment of inherited and many complex acquired disorders. The success of AAV vectors is determined by two major factors: 1) cell transduction efficiency, and 2) persistence of the introduced gene with minimal or no host immune response following vector administration. Previous research has suggested that certain small molecules can improve AAV vector transduction efficiency and lower the vector dose below the immunological response threshold. We explore the use of teniposide, a chemotherapeutic agent, in improving the efficacy of gene therapy using AAV. We co-administered teniposide at a final dosage of 20 mg/kg with an AAV vector encoding an insulin gene controlled by a liver-specific promotor into streptozotocin (STZ) induced diabetic Hsd: ICR mice. Teniposide co-treatment produced up to a 3-fold decrease in AAV dose compared to vector alone while reducing diabetic hyperglycemia to comparable degrees as AAV delivery alone. There was no additional systemic toxicity. While the mechanism of action of teniposide-enhanced viral delivery of gene therapy is unknown, our data suggest that teniposide co-administration could significantly enhance AAV transduction in vivo and provide a novel, useful strategy to improve the clinical efficacy of gene therapy. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Intravenous immunoglobulin prevents peripheral liver transduction of intrathecally delivered AAV vectors

Gene therapy using neurotropic adeno-associated virus vectors represents an emerging solution for genetic disorders affecting the central nervous system. The first approved central nervous system-targeting adeno-associated virus gene therapy, Zolgensma®, for treating spinal muscular atrophy is administered intravenously at high doses that cause liver-associated adverse events in 20%-30% of patients. Intrathecal routes of vector administration, such as the intra-cisterna magna route, provide efficient gene transduction to central nervous system cells while reducing off-target liver transduction. However, significant levels of liver transduction often occur upon intra-cisterna magna vector delivery in preclinical studies. Using vectors expressing monoclonal antibody transgenes, we examined whether passive transfer of adeno-associated virus-neutralizing antibodies as intravenous immunoglobulin before intrathecal adeno-associated virus delivery improved the safety of viral gene therapy targeting the central nervous system in mice and nonhuman primates. We used intracerebroventricular and intra-cisterna magna routes for vector administration to mice and nonhuman primates, respectively, and evaluated transgene expression and vector genome distribution. Our data indicate that pretreatment with intravenous immunoglobulin significantly reduced gene transduction to the liver and other peripheral organs but not to the central nervous system in both species. With further refinement, this method may improve the safety of adeno-associated virus-based, central nervous system-targeting gene therapies in clinical settings.

Gene therapy restores adipose tissue and metabolic health in a pre-clinical mouse model of lipodystrophy

Congenital generalized lipodystrophy type 2 is a serious multisystem disorder with limited treatment options. It is caused by mutations affecting the BSCL2 gene, which encodes the protein seipin. Patients with congenital generalized lipodystrophy type 2 lack both metabolic and mechanical adipose tissue and develop severe metabolic complications including hepatic steatosis, lipoatrophic diabetes, and cardiovascular disease. Gene therapies are becoming viable treatments, helping to alleviate inherited and acquired human disorders. We aimed to determine whether gene therapy could offer an effective form of medical intervention for lipodystrophy. We examined whether systemic adeno-associated virus delivery of human BSCL2 could reverse metabolic disease in seipin knockout mice, where white adipose tissue is absent. We reveal that adeno-associated virus gene therapy targets adipose progenitor cells invivo and substantially restores white adipose tissue development in adult seipin knockout mice. This resulted in both rapid and prolonged beneficial effects to metabolic health in this pre-clinicalmouse model of congenital generalized lipodystrophy type 2. Hyperglycemia was normalized within 2weeks post-treatment together with normalization of severe insulin resistance. We propose that gene therapy offers great potential as a therapeutic strategy to correct multiple metabolic complications in patients with congenital lipodystrophy.

Localized Nano-mediated Interleukin-12 Gene Therapy: Promising Candidate for Cancer Immunotherapeutics.

Interleukin-12 (IL-12) has a pleiotropic nature that allows it to induce immune responses while reversing tumour-induced immunosuppression. Therefore, this paper discusses the application and potential of IL-12 as an antitumor immunotherapeutic agent, emphasizing its advantages and limitations and the need for and the development of localized IL-12 nano-delivery strategies in cancer immunotherapy. Several databases from the National Centre for Biotechnology Information, WorldCat.org and the National Library of Medicine were searched for peer-reviewed studies to assess the potential of localized nano-mediated interleukin-12 gene therapy for cancer treatment. The literature search showed that IL-12 is a promising cancer immunotherapeutic agent. However, the systemic delivery of IL-12 was compromised by severe dose-limiting side effects, prompting the need for localized gene therapy to express the interleukin within the tumour microenvironment while minimizing systematic exposure. Although viral and non-viral gene therapy have demonstrated some efficacy in preclinical trials, the era of nanomedicine has opened novel avenues to improve therapeutic indices with minimal side effects. IL-12 activity can be further potentiated with other anticancer molecules that display immunostimulatory, autoantigenic and cytotoxic properties. Combination therapy has gained significant interest in the last decade as it increases gene therapy's therapeutic properties by decreasing the threshold for IL-12 efficacy and preventing systematic toxicity. The findings of this article will provide researchers with the knowledge to create immunotherapeutic nanovectors which work synergistically with their therapeutic payload to enhance the therapeutic effect of the IL-12 gene to eliminate cancer cells.

Characterization of a novel Pde6b-deficient rat model of retinal degeneration and treatment with adeno-associated virus (AAV) gene therapy.

In humans, mutations in the beta subunit of cGMP-phosphodiesterase type 6 (PDE6B) cause autosomal recessive retinitis pigmentosa (RP), which typically has an aggressive clinical course of early-onset severe vision loss due to rapid photoreceptor degeneration. In this study, we describe the generation of a novel Pde6b-deficient rat model using CRISPR-Cas9 genome editing. We characterize the model at multiple time points using clinical imaging modalities as well as histology with immunohistochemistry to show rapid photoreceptor degeneration compared to wild-type and heterozygous animals. We describe the manufacture of two different adeno-associated viral (AAV) vectors (AAV2/1, AAV2/5) under current Good Manufacturing Practices (cGMP) and demonstrate their ability to drive human PDE6B expression in vivo. We further demonstrate the ability of AAV-mediated subretinal gene therapy to delay photoreceptor loss in Pde6b-deficient rats compared to untreated controls. However, severe progressive photoreceptor loss was noted even in treated eyes, likely due to the aggressive nature of the disease. These data provide useful preclinical data to guide the development of potential human gene therapy for PDE6B-associated RP. In addition, the rapid photoreceptor degeneration of the Pde6b-deficient rat with intact inner retina may provide a useful model for the study of cell replacement strategies.

The inherited cerebellar ataxias: an update.

This narrative review aims at providing an update on the management of inherited cerebellar ataxias (ICAs), describing main clinical entities, genetic analysis strategies and recent therapeutic developments. Initial approach facing a patient with cerebellar ataxia requires family medical history, physical examination, exclusions of acquired causes and genetic analysis, including Next-Generation Sequencing (NGS). To guide diagnosis, several algorithms and a new genetic nomenclature for recessive cerebellar ataxias have been proposed. The challenge of NGS analysis is the identification of causative variant, trio analysis being usually the most appropriate option. Public genomic databases as well as pathogenicity prediction software facilitate the interpretation of NGS results. We also report on key clinical points for the diagnosis of the main ICAs, including Friedreich ataxia, CANVAS, polyglutamine spinocerebellar ataxias, Fragile X-associated tremor/ataxia syndrome. Rarer forms should not be neglected because of diagnostic biomarkers availability, disease-modifying treatments, or associated susceptibility to malignancy. Diagnostic difficulties arise from allelic and phenotypic heterogeneity as well as from the possibility for one gene to be associated with both dominant and recessive inheritance. To complicate the phenotype, cerebellar cognitive affective syndrome can be associated with some subtypes of cerebellar ataxia. Lastly, we describe new therapeutic leads: antisense oligonucleotides approach in polyglutamine SCAs and viral gene therapy in Friedreich ataxia. This review provides support for diagnosis, genetic counseling and therapeutic management of ICAs in clinical practice.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00415-022-11383-6.

Comprehensive assessment of miniature CRISPR-Cas12f nucleases for gene disruption

Because of their small size, the recently developed CRISPR-Cas12f nucleases can be effectively packaged into adeno-associated viruses for gene therapy. However, a systematic evaluation of the editing outcomes of CRISPR-Cas12f is lacking. In this study, we apply a high-throughput sequencing method to comprehensively assess the editing efficiency, specificity, and safety of four Cas12f proteins in parallel with that of Cas9 and two Cas12a proteins at multiple genomic sites. Cas12f nucleases achieve robust cleavage at most of the tested sites and mainly produce deletional fragments. In contrast, Cas9 and Cas12a show relatively higher editing efficiency at the vast majority of the tested sites. However, the off-target hotspots identified in the Cas9- and Cas12a-edited cells are negligibly detected in the Cas12f-edited cells. Moreover, compared to Cas9 and Cas12a nucleases, Cas12f nucleases reduce the levels of chromosomal translocations, large deletions, and integrated vectors by 2- to 3-fold. Therefore, our findings confirm the editing capacity of Cas12f and reveal the ability of this nuclease family to preserve genome integrity during genome editing.