Leber hereditary optic neuropathy gene therapy

PURPOSE OF REVIEW

To discuss relevant clinical outcomes, challenges, and future opportunities of gene therapy in Leber hereditary optic neuropathy (LHON).

RECENT FINDINGS

Results of G11778A LHON Phase 3 randomized clinical trials with unilateral intravitreal rAAV2/2-ND4 allotopic gene therapy show good safety and unexpected bilateral partial improvements of BCVA (best-corrected visual acuity) with mean logMAR BCVA improvements of up to near ∼0.3 logMAR (3 lines) in the treated eyes and ∼0.25 logMAR (2.5 lines) in the sham-treated or placebo-treated fellow eyes. Final mean BCVA levels after gene therapy were in the range of ∼1.3 logMAR (20/400) bilaterally.

SUMMARY

Bilateral partial improvement with unilateral LHON gene therapy was unanticipated and may be due to treatment efficacy, natural history, learning effect, and other mediators. The overall efficacy is limited given the final BCVA levels. The sequential progressive visual loss and varied occurrence of spontaneous partial improvement in LHON confound trial results. Future clinical trials with randomization of patients to a group not receiving gene therapy in either eye would help to assess treatment effect. Promising future LHON gene therapy strategies include mitochondrially-targeted-sequence adeno-associated virus ('MTS-AAV') for direct delivery of the wild-type mitochondrial DNA into the mitochondria and CRISPR-free, RNA-free mitochondrial base editing systems. Signs of anatomical optic nerve damage and objective retinal ganglion cell dysfunction are evident in the asymptomatic eyes of LHON patients experiencing unilateral visual loss, indicating the therapeutic window is narrowing before onset of visual symptoms. Future treatment strategies utilizing mitochondrial base editing in LHON carriers without optic neuropathy holds the promise of a more advantageous approach to achieve optimal visual outcome by reducing disease penetrance and mitigating retinal ganglion cell loss when optic neuropathy develops.

Non-viral and viral delivery systems for hemophilia A therapy: recent development and prospects

Recent advancements have focused on enhancing factor VIII half-life and refining its delivery methods, despite the well-established knowledge that factor VIII deficiency is the main clotting protein lacking in hemophilia. Consequently, both viral and non-viral delivery systems play a crucial role in enhancing the quality of life for hemophilia patients. The utilization of viral vectors and the manipulation of non-viral vectors through targeted delivery are significant advancements in the field of cellular and molecular therapies for hemophilia. These developments contribute to the progression of treatment strategies and hold great promise for improving the overall well-being of individuals with hemophilia. This review study comprehensively explores the application of viral and non-viral vectors in cellular (specifically T cell) and molecular therapy approaches, such as RNA, monoclonal antibody (mAb), and CRISPR therapeutics, with the aim of addressing the challenges in hemophilia treatment. By examining these innovative strategies, the study aims to shed light on potential solutions to enhance the efficacy and outcomes of hemophilia therapy.

Ultrasound-mediated gene delivery specifically targets liver sinusoidal endothelial cells for sustained FVIII expression in hemophilia A mice

The ability to target the native production site of factor VIII (FVIII)-liver sinusoidal endothelial cells (LSECs)-can improve the outcome of hemophilia A (HA) gene therapy. By testing a matrix of ultrasound-mediated gene delivery (UMGD) parameters for delivering a GFP plasmid into the livers of HA mice, we were able to define specific conditions for targeted gene delivery to different cell types in the liver. Subsequently, two conditions were selected for experiments to treat HA mice via UMGD of an endothelial-specific human FVIII plasmid: low energy (LE; 50 W/cm2, 150 μs pulse duration) to predominantly target endothelial cells or high energy (HE; 110 W/cm2, 150 μs pulse duration) to predominantly target hepatocytes. Both groups of UMGD-treated mice achieved persistent FVIII activity levels of ∼10% over 84 days post treatment; however, half of the HE-treated mice developed low-titer inhibitors while none of the LE mice did. Plasma transaminase levels and histological liver examinations revealed minimal transient liver damage that was lower in the LE group than in the HE group. These results indicate that UMGD can safely target LSECs with a lower-energy condition to achieve persistent FVIII gene expression, demonstrating that this novel technology is highly promising for therapeutic correction of HA.

Multidimensional Response Surface Methodology for the Development of a Gene Editing Protocol for p67phox-Deficient Chronic Granulomatous Disease

Replacing a faulty gene with a correct copy has become a viable therapeutic option as a result of recent progress in gene editing protocols. Targeted integration of therapeutic genes in hematopoietic stem cells has been achieved for multiple genes using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 system and Adeno-Associated Virus (AAV) to carry a donor template. Although this is a promising strategy to correct genetic blood disorders, it is associated with toxicity and loss of function in CD34+ hematopoietic stem and progenitor cells, which has hampered clinical application. Balancing the maximum achievable correction against deleterious effects on the cells is critical. However, multiple factors are known to contribute, and the optimization process is laborious and not always clearly defined. We have developed a flexible multidimensional Response Surface Methodology approach for optimization of gene correction. Using this approach, we could rapidly investigate and select editing conditions for CD34+ cells with the best possible balance between correction and cell/colony-forming unit (CFU) loss in a parsimonious one-shot experiment. This method revealed that using relatively low doses of AAV2/6 and CRISPR/Cas9 ribonucleoprotein complex, we can preserve the fitness of CD34+ cells and, at the same time, achieve high levels of targeted gene insertion. We then used these optimized editing conditions for the correction of p67phox-deficient chronic granulomatous disease (CGD), an autosomal recessive disorder of blood phagocytic cells resulting in severe recurrent bacterial and fungal infections and achieved rescue of p67phox expression and functional correction of CD34+-derived neutrophils from a CGD patient.

Lentiviral Gene Therapy for Mucopolysaccharidosis II with Tagged Iduronate 2-Sulfatase Prevents Life-Threatening Pathology in Peripheral Tissues But Fails to Correct Cartilage

Deficiency of iduronate 2-sulfatase (IDS) causes Mucopolysaccharidosis type II (MPS II), a lysosomal storage disorder characterized by systemic accumulation of glycosaminoglycans (GAGs), leading to a devastating cognitive decline and life-threatening respiratory and cardiac complications. We previously found that hematopoietic stem and progenitor cell-mediated lentiviral gene therapy (HSPC-LVGT) employing tagged IDS with insulin-like growth factor 2 (IGF2) or ApoE2, but not receptor-associated protein minimal peptide (RAP12x2), efficiently prevented brain pathology in a murine model of MPS II. In this study, we report on the effects of HSPC-LVGT on peripheral pathology and we analyzed IDS biodistribution. We found that HSPC-LVGT with all vectors completely corrected GAG accumulation and lysosomal pathology in liver, spleen, kidney, tracheal mucosa, and heart valves. Full correction of tunica media of the great heart vessels was achieved only with IDS.IGF2co gene therapy, while the other vectors provided near complete (IDS.ApoE2co) or no (IDSco and IDS.RAP12x2co) correction. In contrast, tracheal, epiphyseal, and articular cartilage remained largely uncorrected by all vectors tested. These efficacies were closely matched by IDS protein levels following HSPC-LVGT. Our results demonstrate the capability of HSPC-LVGT to correct pathology in tissues of high clinical relevance, including those of the heart and respiratory system, while challenges remain for the correction of cartilage pathology.

Establishment of the Effectiveness of Early Versus Late Stem Cell Gene Therapy in Mucopolysaccharidosis II for Treating Central Versus Peripheral Disease

Mucopolysaccharidosis type II (MPSII) is a rare pediatric X-linked lysosomal storage disease, caused by heterogeneous mutations in the iduronate-2-sulfatase (IDS) gene, which result in accumulation of heparan sulfate (HS) and dermatan sulfate within cells. This leads to severe skeletal abnormalities, hepatosplenomegaly, and cognitive deterioration. The progressive nature of the disease is a huge obstacle to achieve full neurological correction. Although current therapies can only treat somatic symptoms, a lentivirus-based hematopoietic stem cell gene therapy (HSCGT) approach has recently achieved improved central nervous system (CNS) neuropathology in the MPSII mouse model following transplant at 2 months of age. In this study, we evaluate neuropathology progression in 2-, 4- and 9-month-old MPSII mice, and using the same HSCGT strategy, we investigated somatic and neurological disease attenuation following treatment at 4 months of age. Our results showed gradual accumulation of HS between 2 and 4 months of age, but full manifestation of microgliosis/astrogliosis as early as 2 months. Late HSCGT fully reversed the somatic symptoms, thus achieving the same degree of peripheral correction as early therapy. However, late treatment resulted in slightly decreased efficacy in the CNS, with poorer brain enzymatic activity, together with reduced normalization of HS oversulfation. Overall, our findings confirm significant lysosomal burden and neuropathology in 2-month-old MPSII mice. Peripheral disease is readily reversible by LV.IDS-HSCGT regardless of age of transplant, suggesting a viable treatment for somatic disease. However, in the brain, higher IDS enzyme levels are achievable with early HSCGT treatment, and later transplant seems to be less effective, supporting the view that the earlier patients are diagnosed and treated, the better the therapy outcome.

Modification of the tumor microenvironment enhances immunity with plasmid gene therapy

Local intratumor delivery with electroporation of low levels of plasmids encoding molecules, induces an antitumor effect without causing systemic toxicity. However, previous studies have predominately focused on the function of the delivered molecule encoded within the plasmid, and ignored the plasmid vector. In this study, we found vectors pUMVC3 and pVax1 induced upregulation of MHC class I (MHC-I) and PD-L1 on tumor cell surface. These molecules participate in a considerable number of immunoregulatory functions through their interactions with and activating inhibitory immune cell receptors. MHC molecules are well-known for their role in antigen (cross-) presentation, thereby functioning as key players in the communication between immune cells and tumor cells. Increased PD-L1 expression on tumor cells is an important monitor of tumor growth and the effectiveness of immune inhibitor therapy. Results from flow cytometry confirmed increased expression of MHC-I and PDL-1 on B16F10, 4T1, and KPC tumor cell lines. Preliminary animal data from tumor-bearing models, B16F10 melanoma, 4T1 breast cancer and KPC pancreatic cancer mouse models showed that tumor growth was attenuated after pUMVC3 intratumoral electroporation. Our data also documented that pSTAT1 signaling pathway might not be associated with plasmid vectors' function of upregulating MHC-I, PD-L1 on tumor cells.

Hepatitis after gene therapy, what are the possible causes?

Hepatitis is a common adverse event following gene therapy for haemophilia, often associated with a loss of transgene expression. Investigating the potential causes and implications of this is crucial for the overall success of treatment. Gene therapy trials using adeno-associated virus (AAV) vectors have demonstrated promising results marked by increases in factor FVIII and FIX levels and reductions in episodes of bleeding. However, hepatocellular injury characterised by elevations in alanine aminotransferases (ALT) has been noted. This liver injury is typically transient and asymptomatic, posing challenges in determining its clinical significance. Proposed causes encompass immune-mediated responses, notably T cell cytotoxicity in response to the AAV vector, direct liver injury from the viral capsid or transcribed protein via the unfolded protein response and pre-existing liver conditions. Liver biopsy data conducted years post-gene therapy infusion has shown sinusoidal infiltration without significant inflammation. The overall safety profile of gene therapy remains favourable with no evidence drug-induced liver injury (DILI) based on Hy's Law criteria. Essential pre-therapy monitoring and identifying patients at high risk of liver injury should involve liver function tests and non-invasive fibroscans, while novel blood-based biomarkers are under exploration. Further research is required to comprehend the mechanisms underlying transaminitis, loss of transgene expression and long-term effects on the liver, providing insights for optimising gene therapy for haemophilia.

Which patients should be considered for gene therapy

Gene therapy for haemophilia, utilizing adeno-associated viral vectors (AAVs) and coagulation factor genes, have demonstrated promising results, leading to recent approvals and introduction of the first gene therapy products into clinical practice. For successful and safe use, there are predefined inclusion and exclusion criteria, and the treatment process and associated risks should be thoroughly understood and long-term safety and efficacy carefully evaluated during follow up. As gene therapy becomes more accessible outside of clinical study centers, continuous evaluation of patient eligibility for subsequent AAV-based treatments becomes essential. Thorough evaluation of factors such as liver condition, anti-AAV status, and medical history ensures that gene therapy maximizing benefits while minimizing risks. Apart from fulfilling the established inclusion and exclusion criteria, the success of gene therapy is greatly influenced by the motivation and willingness of patients to accept temporary constraints, such as regular laboratory monitoring, potential use of immunosuppressants, and thorough documentation. Furthermore, various patient-related factors play a significant role in the management and outcomes of gene therapy, making a comprehensive evaluation essential. With the accumulation of more data, there is potential for the expansion of certain inclusion criteria, which may allow for a larger number of eligible patients to benefit from gene therapy. Empowering patients through shared decision-making enables them to thoroughly consider the therapy's potential benefits and risks.

The New Frontiers of Gene Therapy and Gene Editing in Inflammatory Diseases

Inflammatory diseases are conditions characterized by abnormal and often excessive immune responses, leading to tissue and organ inflammation. The complexity of these disorders arises from the intricate interplay of genetic factors and immune responses, which challenges conventional therapeutic approaches. However, the field of genetic manipulation has sparked unprecedented optimism in addressing these complex disorders. This review aims to comprehensively explore the application of gene therapy and gene editing in the context of inflammatory diseases, offering solutions that range from correcting genetic defects to precise immune modulation. These therapies have exhibited remarkable potential in ameliorating symptoms, improving quality of life, and even achieving disease remission. As we delve into recent breakthroughs and therapeutic applications, we illustrate how these advancements offer novel and transformative solutions for conditions that have traditionally eluded conventional treatments. By examining successful case studies and preclinical research, we emphasize the favorable results and substantial transformative impacts that gene-based interventions have demonstrated in patients and animal models of inflammatory diseases such as chronic granulomatous disease, cryopyrin-associated syndromes, and adenosine deaminase 2 deficiency, as well as those of multifactorial origins such as arthropathies (osteoarthritis, rheumatoid arthritis) and inflammatory bowel disease. In conclusion, gene therapy and gene editing offer transformative opportunities to address the underlying causes of inflammatory diseases, ushering in a new era of precision medicine and providing hope for personalized, targeted treatments.

Nanotechnology strategies to address challenges in topical and cellular delivery of siRNAs in skin disease therapy

Gene therapy is one of the most advanced therapies in current medicine. In particular, interference RNA-based therapy by small interfering RNA (siRNA) has gained attention in recent years as it is a highly versatile, selective and specific therapy. In dermatological conditions, topical delivery of siRNA offers numerous therapeutic advantages, mainly by inhibiting the expression of target transcripts directly in the skin. However, crossing the stratum corneum and overcoming intracellular barriers is an inherent challenge. Substantial efforts by scientists have moved towards the use of multimodal and multifunctional nanoparticles to overcome these barriers and achieve greater bioavailability in their site of action, the cytoplasm. In this review the most innovative strategies based on nanoparticle and physical methods are presented, as well as the design principles and the main factors that contribute to the performance of these systems. This review also highlights the synergistic contributions of medicine, nanotechnology, and molecular biology to advancing translational research into siRNA-based therapeutics for skin diseases.

Intravitreal Delivery of PEGylated-ECO Plasmid DNA Nanoparticles for Gene Therapy of Stargardt Disease

OBJECTIVE

Current gene therapy of inherited retinal diseases is achieved mainly by subretinal injection, which is invasive with severe adverse effects. Intravitreal injection is a minimally invasive alternative for gene therapy of inherited retinal diseases. This work explores the efficacy of intravitreal delivery of PEGylated ECO (a multifunctional pH-sensitive amphiphilic amino lipid) plasmid DNA (pGRK1-ABCA4-S/MAR) nanoparticles (PEG-ELNP) for gene therapy of Stargardt disease.

METHODS

Pigmented Abca4-/- knockout mice received 1 µL of PEG-ELNP solution (200 ng/uL, pDNA concentration) by intravitreal injections at an interval of 1.5 months. The expression of ABCA4 in the retina was determined by RT-PCR and immunohistochemistry at 6 months after the second injection. A2E levels in the treated eyes and untreated controls were determined by HPLC. The safety of treatment was monitored by scanning laser ophthalmoscopy and electroretinogram (ERG).

RESULTS

PEG-ELNP resulted in significant ABCA4 expression at both mRNA level and protein level at]6 months after 2 intravitreal injections, and a 40% A2E accumulation reduction compared with non-treated controls. The PEG-ELNP also demonstrated excellent safety as shown by scanning laser ophthalmoscopy, and the eye function evaluation from electroretinogram.

CONCLUSIONS

Intravitreal delivery of the PEG-ELNP of pGRK1-ABCA4-S/MAR is a promising approach for gene therapy of Stargardt Disease, which can also be a delivery platform for gene therapy of other inherited retinal diseases.

Bacteriophage-based particles carrying the TNF-related apoptosis-inducing ligand (TRAIL) gene for targeted delivery in hepatocellular carcinoma

The TRAIL (Tumour Necrosis Factor-Related Apoptosis-Inducing Ligand) is a promising candidate for cancer treatment due to its unique ability to selectively induce programmed cell death, or apoptosis, in cancer cells while sparing healthy ones. This selectivity arises from the preferential binding of the TRAIL to death receptors on cancer cells, triggering a cascade of events that lead to their demise. However, significant limitations in using the TRAIL for cancer treatment are the administration of the TRAIL protein that can potentially lead to tissue toxicity (off-target) and the short half-life of the TRAIL in the body which may necessitate frequent and sustained administration; these can pose logistical challenges for long-term treatment regimens. We have devised a novel approach for surmounting these limitations by introducing the TRAIL gene directly into cancer cells, enabling them to produce the TRAIL locally and subsequently trigger apoptosis. A novel gene delivery system such as a bacteriophage-based particle TPA (transmorphic phage/AAV) was utilized to address these limitations. TPA is a hybrid M13 filamentous bacteriophage particle encapsulating a therapeutic gene cassette with inverted terminal repeats (ITRs) from adeno-associated viruses (AAVs). The particle also showed a tumour targeting ligand, CDCRGDCFC (RGD4C), on its capsid (RGD4C.TPA) to target the particle to cancer cells. RGD4C selectively binds to αvβ3 and αvβ5 integrins overexpressed on the surface of most of the cancer cells but is barely present on normal cells. Hepatocellular carcinoma (HCC) was chosen as a model because it has one of the lowest survival rates among cancers. We demonstrated that human HCC cell lines (Huh-7 and HepG2) express αvβ5 integrin receptors on their surface. These HCC cells also express death receptors and TRAIL-binding receptors. We showed that the targeted TPA particle carrying the transmembrane TRAIL gene (RGD4C.TPA-tmTRAIL) selectively and efficiently delivered the tmTRAIL gene to HCC cells resulting in the production of tmTRAIL from transduced cells and subsequently induced apoptotic death of HCC cells. This tumour-targeted particle can be an excellent candidate for the targeted gene therapy of HCC.

Intrathecal Gene Therapy for Giant Axonal Neuropathy

BACKGROUND

Giant axonal neuropathy is a rare, autosomal recessive, pediatric, polysymptomatic, neurodegenerative disorder caused by biallelic loss-of-function variants in GAN, the gene encoding gigaxonin.

METHODS

We conducted an intrathecal dose-escalation study of scAAV9/JeT-GAN (a self-complementary adeno-associated virus-based gene therapy containing the GAN transgene) in children with giant axonal neuropathy. Safety was the primary end point. The key secondary clinical end point was at least a 95% posterior probability of slowing the rate of change (i.e., slope) in the 32-item Motor Function Measure total percent score at 1 year after treatment, as compared with the pretreatment slope.

RESULTS

One of four intrathecal doses of scAAV9/JeT-GAN was administered to 14 participants - 3.5×1013 total vector genomes (vg) (in 2 participants), 1.2×1014 vg (in 4), 1.8×1014 vg (in 5), and 3.5×1014 vg (in 3). During a median observation period of 68.7 months (range, 8.6 to 90.5), of 48 serious adverse events that had occurred, 1 (fever) was possibly related to treatment; 129 of 682 adverse events were possibly related to treatment. The mean pretreatment slope in the total cohort was -7.17 percentage points per year (95% credible interval, -8.36 to -5.97). At 1 year after treatment, posterior mean changes in slope were -0.54 percentage points (95% credible interval, -7.48 to 6.28) with the 3.5×1013-vg dose, 3.23 percentage points (95% credible interval, -1.27 to 7.65) with the 1.2×1014-vg dose, 5.32 percentage points (95% credible interval, 1.07 to 9.57) with the 1.8×1014-vg dose, and 3.43 percentage points (95% credible interval, -1.89 to 8.82) with the 3.5×1014-vg dose. The corresponding posterior probabilities for slowing the slope were 44% (95% credible interval, 43 to 44); 92% (95% credible interval, 92 to 93); 99% (95% credible interval, 99 to 99), which was above the efficacy threshold; and 90% (95% credible interval, 89 to 90). Between 6 and 24 months after gene transfer, sensory-nerve action potential amplitudes increased, stopped declining, or became recordable after being absent in 6 participants but remained absent in 8.

CONCLUSIONS

Intrathecal gene transfer with scAAV9/JeT-GAN for giant axonal neuropathy was associated with adverse events and resulted in a possible benefit in motor function scores and other measures at some vector doses over a year. Further studies are warranted to determine the safety and efficacy of intrathecal AAV-mediated gene therapy in this disorder. (Funded by the National Institute of Neurological Disorders and Stroke and others; ClinicalTrials.gov number, NCT02362438.).

Taking the knife to neurodegeneration: a review of surgical gene therapy delivery to the CNS

Gene supplementation and editing for neurodegenerative disorders has emerged in recent years as the understanding of the genetic mechanisms underlying several neurodegenerative disorders increases. The most common medium to deliver genetic material to cells is via viral vectors; and with respect to the central nervous system, adeno-associated viral (AAV) vectors are a popular choice. The most successful example of AAV-based gene therapy for neurodegenerative disorders is Zolgensma© which is a transformative intravenous therapy given to babies with spinal muscular atrophy. However, the field has stalled in achieving safe drug delivery to the central nervous system in adults for which treatments for disorders such as amyotrophic lateral sclerosis are desperately needed. Surgical gene therapy delivery has been proposed as a potential solution to this problem. While the field of the so-called regenerative neurosurgery has yielded pre-clinical optimism, several challenges have emerged. This review seeks to explore the field of regenerative neurosurgery with respect to AAV-based gene therapy for neurodegenerative diseases, its progress so far and the challenges that need to be overcome.

"Treatment with curative intent": the emergence of genetic therapies for sickle cell anemia

ABSTRACT

The root cause of sickle cell anemia has been known for 7 decades, yet no curative therapies have been available other than allogeneic bone marrow transplantation, for which applicability is limited. Two potentially curative therapies based on gene therapy and gene editing strategies have recently received US Food and Drug Administration approval. This review surveys the nature of these therapies and the opportunities and issues raised by the prospect of definitive genetically based therapies being available in clinical practice.

Suprachoroidal gene transfer with nonviral nanoparticles in large animal eyes

Suprachoroidal nonviral gene therapy with biodegradable poly(β-amino ester) nanoparticles (NPs) provides widespread expression in photoreceptors and retinal pigmented epithelial (RPE) cells and therapeutic benefits in rodents. Here, we show in a human-sized minipig eye that suprachoroidal injection of 50 μl of NPs containing 19.2 μg of GFP expression plasmid caused GFP expression in photoreceptors and RPE throughout the entire eye with no toxicity. Two weeks after injection of 50, 100, or 200 μl, there was considerable within-eye and between-eye variability in expression that was reduced 3 months after injection of 200 μl and markedly reduced after three suprachoroidal injections at different locations around the eye. Reduction of bacterial CpG sequences in the expression plasmid resulted in a trend toward higher expression. These data indicate that nonviral suprachoroidal gene therapy with optimized polymer, expression plasmid, and injection approach has potential for treating photoreceptors throughout the entire retina of a human-sized eye.

Development of CNS tropic AAV1-like variants with reduced liver-targeting following systemic administration in mice

Directed evolution of natural AAV9 using peptide display libraries have been widely used in the search for an optimal recombinant AAV (rAAV) for transgene delivery across the blood-brain barrier (BBB) to the CNS following intravenous ( IV) injection. In this study, we used a different approach by creating a shuffled rAAV capsid library based on parental AAV serotypes 1 through 12. Following selection in mice, 3 novel variants closely related to AAV1, AAV-BBB6, AAV-BBB28, and AAV-BBB31, emerged as top candidates. In direct comparisons with AAV9, our novel variants demonstrated an over 270-fold improvement in CNS transduction and exhibited a clear bias toward neuronal cells. Intriguingly, our AAV-BBB variants relied on the LY6A cellular receptor for CNS entry, similar to AAV9 peptide variants AAV-PHP.eB and AAV.CAP-B10, despite the different bioengineering methods used and parental backgrounds. The variants also showed reduced transduction of both mouse liver and human primary hepatocytes in vivo. To increase clinical translatability, we enhanced the immune escape properties of our new variants by introducing additional modifications based on rational design. Overall, our study highlights the potential of AAV1-like vectors for efficient CNS transduction with reduced liver tropism, offering promising prospects for CNS gene therapies.

Exploring modified chitosan-based gene delivery technologies for therapeutic advancements

One of the critical steps in gene therapy is the successful delivery of the genes. Immunogenicity and toxicity are major issues for viral gene delivery systems. Thus, non-viral vectors are explored. A cationic polysaccharide like chitosan could be used as a nonviral gene delivery vector owing to its significant interaction with negatively charged nucleic acid and biomembrane, providing effective cellular uptake. However, the native chitosan has issues of targetability, unpacking ability, and solubility along with poor buffer capability, hence requiring modifications for effective use in gene delivery. Modified chitosan has shown that the "proton sponge effect" involved in buffering the endosomal pH results in osmotic swelling owing to the accumulation of a greater amount of proton and chloride along with water. The major challenges include limited exploration of chitosan as a gene carrier, the availability of high-purity chitosan for toxicity reduction, and its immunogenicity. The genetic drugs are in their infancy phase and require further exploration for effective delivery of nucleic acid molecules as FDA-approved marketed formulations soon.

Defining curative endpoints for transfusion-dependent β-thalassemia in the era of gene therapy and gene editing

β-thalassemia is a monogenic disease that results in varying degrees of anemia. In the most severe form, known as transfusion-dependent β-thalassemia (TDT), the clinical hallmarks are ineffective erythropoiesis and a requirement of regular, life-long red blood cell transfusions, with the development of secondary clinical complications such as iron overload, end-organ damage, and a risk of early mortality. With the exception of allogeneic hematopoietic cell transplantation, current treatments for TDT address disease symptoms and not the underlying cause of disease. Recently, a growing number of gene addition and gene editing-based treatments for patients with TDT with the potential to provide a one-time functional cure have entered clinical trials. A key challenge in the design and evaluation of these trials is selecting endpoints to evaluate if these novel genetic therapies have a curative versus an ameliorative effect. Here, we present an overview of the pathophysiology of TDT, review emerging gene addition or gene editing therapeutic approaches for TDT currently in clinical trials, and identify a series of endpoints that can quantify therapeutic effects, including a curative outcome.

Gene therapy vector-related myocarditis

Gene therapy is a technique to correct genetic abnormalities, through introduction of a functional gene or through direct genome editing. Adeno-associated virus (AAV)-mediated gene replacement shows promise for targeted therapies in treatment of inherited cardiomyopathies and is the most used approach in clinical trials. However, immune responses from the host to the virus and gene product pose delivery and safety challenges. This review explores the immunological reactions to AAV-based gene therapy, their potential toxic effects, with a focus on myocarditis, and future directions for gene therapy.

Gene therapy for adenosine deaminase severe combined immune deficiency-An unexpected journey of four decades

Severe combined immune deficiency due to adenosine deaminase deficiency (ADA SCID) is an inborn error of immunity with pan-lymphopenia, due to accumulated cytotoxic adenine metabolites. ADA SCID has been treated using gene therapy with a normal human ADA gene added to autologous hematopoietic stem cells (HSC) for over 30 years. Iterative improvements in vector design, HSC processing methods, and clinical HSC transplant procedures have led nearly all ADA SCID gene therapy patients to achieve consistently beneficial immune restoration with stable engraftment of ADA gene-corrected HSC over the duration of observation (as long as 20 years). One gene therapy for ADA SCID is approved by the European Medicines Agency (EMA) in the European Union (EU) and another is being advanced to licensure in the U.S. and U.K. Despite the clear-cut benefits and safety of this curative gene and cell therapy, it remains challenging to achieve sustained availability and access, especially for rare disorders like ADA SCID.

Distributional comparison of different AAV vectors after unilateral cochlear administration

The adeno-associated virus (AAV) gene therapy has been widely applied to mouse models for deafness. But, AAVs could transduce non-targeted organs after inner ear delivery due to their low cell-type specificity. This study compares transgene expression and biodistribution of AAV1, AAV2, Anc80L65, AAV9, AAV-PHP.B, and AAV-PHP.eB after round window membrane (RWM) injection in neonatal mice. The highest virus concentration was detected in the injected cochlea. AAV2, Anc80L65, AAV9, AAV-PHP.B, and AAV-PHP.eB transduced both inner hair cells (IHCs) and outer hair cells (OHCs) with high efficiency, while AAV1 transduced IHCs with high efficiency but OHCs with low efficiency. All AAV subtypes finitely transduced contralateral inner ear, brain, heart, and liver compared with the injected cochlea. In most brain regions, the enhanced green fluorescent protein (eGFP) expression of AAV1 and AAV2 was lower than that of other four subtypes. We suggested the cochlear aqueduct might be one of routes for vectors instantaneously infiltrating into the brain from the cochlea through a dye tracking test. In summary, our results provide available data for further investigating the biodistribution of vectors through local inner ear injection and afford a reference for selecting AAV serotypes for gene therapy toward deafness.

Permanent transduction of retinal ganglion cells by rAAV2-retro

Adeno-associated virus (AAV) is widely used as a vector for delivery of gene therapy. Long term therapeutic benefit depends on perpetual expression of the wild-type gene after transduction of host cells by AAV. To address this issue in a mass population of identified single cells, 4 rats received an injection of a 1:1 mixture of rAAV2-retro-hSyn-EGFP and rAAV2-retro-hSyn-mCherry into each superior colliculus. After the virus was transported retrogradely to both retinas, serial fundus imaging was performed at days 14, 45, 211, and 375 to visualize individual fluorescent ganglion cells. The location of each cell was plotted to compare labeling at each time point. In 12/16 comparisons, 97% or more of the cells identified in the initial baseline fundus image were still labeled at day 375. In 4 cases the percentage was lower, but in these cases the apparent reduction in the number of labeled cells at day 375 was attributable to the lower quality of follow-up fundus images, rather than true loss of transgene expression. These data indicate that retinal ganglion cells transduced by rAAV2-retro are transduced permanently.

Current Status and Prospects of Viral Vector-Based Gene Therapy to Treat Kidney Diseases

Inherited kidney diseases are among the leading causes of chronic kidney disease, reducing the quality of life and resulting in substantial socioeconomic impact. The advent of early genetic testing and the growing understanding of the molecular basis and pathophysiology of these disorders have opened avenues for novel treatment strategies. Viral vector-based gene therapies have evolved from experimental treatments for rare diseases to potent platforms that carry the intrinsic potential to provide a cure with a single application. Several gene therapy products have reached the market, and the numbers are only expected to increase. Still, none target inherited kidney diseases. Gene transfer to the kidney has lagged when compared to other tissue-directed therapies such as hepatic, neuromuscular, and ocular tissues. Systemic delivery of genetic information to tackle kidney disease is challenging. The pharma industry is taking steps to take on kidney disease and to translate the current research into the therapeutic arena. In this review, we provide an overview of the current viral vector-based approaches and their potential. We discuss advances in platforms and injection routes that have been explored to enhance gene delivery toward kidney cells in animal models, and how these can fuel the development of viable gene therapy products for humans.

Treatment of infantile-onset Pompe disease in a rat model with muscle-directed AAV gene therapy

OBJECTIVE

Pompe disease (PD) is caused by deficiency of the lysosomal enzyme acid α-glucosidase (GAA), leading to progressive glycogen accumulation and severe myopathy with progressive muscle weakness. In the Infantile-Onset PD (IOPD), death generally occurs <1 year of age. There is no cure for IOPD. Mouse models of PD do not completely reproduce human IOPD severity. Our main objective was to generate the first IOPD rat model to assess an innovative muscle-directed adeno-associated viral (AAV) vector-mediated gene therapy.

METHODS

PD rats were generated by CRISPR/Cas9 technology. The novel highly myotropic bioengineered capsid AAVMYO3 and an optimized muscle-specific promoter in conjunction with a transcriptional cis-regulatory element were used to achieve robust Gaa expression in the entire muscular system. Several metabolic, molecular, histopathological, and functional parameters were measured.

RESULTS

PD rats showed early-onset widespread glycogen accumulation, hepato- and cardiomegaly, decreased body and tissue weight, severe impaired muscle function and decreased survival, closely resembling human IOPD. Treatment with AAVMYO3-Gaa vectors resulted in widespread expression of Gaa in muscle throughout the body, normalizing glycogen storage pathology, restoring muscle mass and strength, counteracting cardiomegaly and normalizing survival rate.

CONCLUSIONS

This gene therapy holds great potential to treat glycogen metabolism alterations in IOPD. Moreover, the AAV-mediated approach may be exploited for other inherited muscle diseases, which also are limited by the inefficient widespread delivery of therapeutic transgenes throughout the muscular system.

Spherical nucleic acids: emerging amplifiers for therapeutic nanoplatforms

Gene therapy is a revolutionary treatment approach in the 21st century, offering significant potential for disease prevention and treatment. However, the efficacy of gene delivery is often compromised by the inherent challenges of gene properties and vector-related defects. It is crucial to explore ways to enhance the curative effect of gene drugs and achieve safer, more widespread, and more efficient utilization, which represents a significant challenge in amplification gene therapy advancements. Spherical nucleic acids (SNAs), with their unique physicochemical properties, are considered an innovative solution for scalable gene therapy. This review aims to comprehensively explore the amplifying contributions of SNAs in gene therapy and emphasize the contribution of SNAs to the amplification effect of gene therapy from the aspects of structure, application, and recent clinical translation - an aspect that has been rarely reported or explored thus far. We begin by elucidating the fundamental characteristics and scaling-up properties of SNAs that distinguish them from traditional linear nucleic acids, followed by an analysis of combined therapy treatment strategies, theranostics, and clinical translation amplified by SNAs. We conclude by discussing the challenges of SNAs and provide a prospect on the amplification characteristics. This review seeks to update the current understanding of the use of SNAs in gene therapy amplification and promote further research into their clinical translation and amplification of gene therapy.

Giroctocogene fitelparvovec gene therapy for severe hemophilia A: 104-week analysis of the phase 1/2 Alta study

ABSTRACT

Patients with hemophilia A require exogenous factor VIII (FVIII) or nonfactor hemostatic agents to prevent spontaneous bleeding events. Adeno-associated virus (AAV) vector-based gene therapy is under clinical investigation to enable endogenous FVIII production. Giroctocogene fitelparvovec is a recombinant AAV serotype 6 vector containing the coding sequence for the B-domain-deleted human F8 gene. In the ongoing phase 1/2, dose-ranging Alta study, 4 sequential cohorts of male participants with severe hemophilia A received a single IV dose of giroctocogene fitelparvovec. The primary end points are safety and changes in circulating FVIII activity. Interim results up to 214 weeks after treatment for all participants are presented. Eleven participants were dosed. Increases in alanine and aspartate aminotransferases were the most common treatment-related adverse events (AEs), which resolved with corticosteroid administration. Two treatment-related serious AEs (hypotension and pyrexia) were reported in 1 participant within 6 hours of infusion and resolved within 24 hours after infusion. At the highest dose level (3 × 1013 vg/kg; n = 5), the mean circulating FVIII activity level at week 52 was 42.6% (range, 7.8%-122.3%), and at week 104 it was 25.4% (range, 0.9%-71.6%) based on a chromogenic assay. No liver masses, thrombotic events, or confirmed inhibitors were detected in any participant. These interim 104-week data suggest that giroctocogene fitelparvovec is generally well tolerated with appropriate clinical management and has the potential to provide clinically meaningful FVIII activity levels, as indicated by the low rate of bleeding events in the highest dose cohort. This trial was registered at www.clinicaltrials.gov as #NCT03061201.

Choosing the right mouse model: comparison of humanized NSG and NBSGW mice for in vivo HSC gene therapy

ABSTRACT

In vivo hematopoietic stem cell (HSC) gene therapy is an emerging and promising area of focus in the gene therapy field. Humanized mouse models are frequently used to evaluate novel HSC gene therapy approaches. Here, we comprehensively evaluated 2 mouse strains, NSG and NBSGW. We studied human HSC engraftment in the bone marrow (BM), mobilization of BM-engrafted HSCs into circulation, in vivo transduction using vesicular stomatitis virus glycoprotein-pseudotyped lentiviral vectors (VSV-G LVs), and the expression levels of surface receptors needed for transduction of viral vectors. Our findings reveal that the NBSGW strain exhibits superior engraftment of human long-term HSCs compared with the NSG strain. However, neither model resulted in a significant increase in circulating human HSCs after mobilization. We show that time after humanization as well as human chimerism levels and platelet counts in the peripheral blood can be used as surrogates for human HSC engraftment in the BM. Furthermore, we observed low expression of the low-density lipoprotein receptor, a requirement for VSV-G LV transduction, in the human HSCs present in the murine BM. Our comprehensive characterization of humanized mouse models highlights the necessity of proper validation of the model and methods to study in vivo HSC gene therapy strategies.

Precise genome-editing in human diseases: mechanisms, strategies and applications

Precise genome-editing platforms are versatile tools for generating specific, site-directed DNA insertions, deletions, and substitutions. The continuous enhancement of these tools has led to a revolution in the life sciences, which promises to deliver novel therapies for genetic disease. Precise genome-editing can be traced back to the 1950s with the discovery of DNA's double-helix and, after 70 years of development, has evolved from crude in vitro applications to a wide range of sophisticated capabilities, including in vivo applications. Nonetheless, precise genome-editing faces constraints such as modest efficiency, delivery challenges, and off-target effects. In this review, we explore precise genome-editing, with a focus on introduction of the landmark events in its history, various platforms, delivery systems, and applications. First, we discuss the landmark events in the history of precise genome-editing. Second, we describe the current state of precise genome-editing strategies and explain how these techniques offer unprecedented precision and versatility for modifying the human genome. Third, we introduce the current delivery systems used to deploy precise genome-editing components through DNA, RNA, and RNPs. Finally, we summarize the current applications of precise genome-editing in labeling endogenous genes, screening genetic variants, molecular recording, generating disease models, and gene therapy, including ex vivo therapy and in vivo therapy, and discuss potential future advances.

Poly(ethylenimine)-Cyclodextrin-Based Cationic Polymer Mediated HIF-1α Gene Delivery for Hindlimb Ischemia Treatment

Hindlimb ischemia is a common disease worldwide featured by the sudden decrease in limb perfusion, which usually causes a potential threat to limb viability and even amputation or death. Revascularization has been defined as the gold-standard therapy for hindlimb ischemia. Considering that vascular injury recovery requires cellular adaptation to the hypoxia, hypoxia-inducible factor 1 α (HIF-1α) is a potential gene for tissue restoration and angiogenesis. In this manuscript, effective gene delivery vector PEI-β-CD (PC) was reported for the first application in the hindlimb ischemia treatment to deliver HIF-1α plasmid in vitro and in vivo. Our in vitro finding demonstrated that PC/HIF-1α-pDNA could be successfully entered into the cells and mediated efficient gene transfection with good biocompatibility. More importantly, under hypoxic conditions, PC/HIF-1α-pDNA could up-regulate the HUEVC cell viability. In addition, the mRNA levels of VEGF, Ang-1, and PDGF were upregulated, and transcriptome results also demonstrated that the cell-related function of response to hypoxia was enhanced. The therapeutic effect of PC/HIF-1α-pDNA was further estimated in a murine acute hindlimb ischemia model, which demonstrated that intramuscular injection of PC/HIF-1α-pDNA resulted in significantly increased blood perfusion and alleviation in tissue damage, such as tissue fibrosis and inflammation. The results provide a rationale that HIF-1α-mediated gene therapy might be a practical strategy for the treatment of limb ischemia.

Extended time frame for restoring inner ear function through gene therapy in Usher1G preclinical model

Neonatal gene therapy has been shown to prevent inner ear dysfunction in mouse models of Usher syndrome type I (USH1), the most common genetic cause of combined deafness-blindness and vestibular dysfunction. However, hearing onset occurs after birth in mice and in utero in humans, making it questionable how to transpose murine gene therapy outcomes to clinical settings. Here, we sought to extend the therapeutic time window in a mouse model for USH1G to periods corresponding to human neonatal stages, more suitable for intervention in patients. Mice with deletion of Ush1g (Ush1g-/-) were subjected to gene therapy after the hearing onset. The rescue of inner ear hair cell structure was evaluated by confocal imaging and electron microscopy. Hearing and vestibular function were assessed by recordings of the auditory brain stem response and vestibulo-ocular reflex and by locomotor tests. Up to P21, gene therapy significantly restored both the hearing and balance deficits in Ush1g-/- mice. However, beyond this age and up to P30, vestibular function was restored but not hearing. Our data show that effective gene therapy is possible in Ush1g-/- mice well beyond neonatal stages, implying that the therapeutic window for USH1G may be wide enough to be transposable to newborn humans.

Advanced strategies for CRISPR/Cas9 delivery and applications in gene editing, therapy, and cancer detection using nanoparticles and nanocarriers

Cancer remains one of the deadliest diseases, and is characterised by the uncontrolled growth of modified human cells. Unlike infectious diseases, cancer does not originate from foreign agents. Though a variety of diagnostic procedures are available; their cost-effectiveness and accessibility create significant hurdles. Non-specific cancer symptoms further complicate early detection, leading to belated recognition of certain cancer. The lack of reliable biomarkers hampers effective treatment, as chemotherapy, radiation therapy, and surgery often result in poor outcomes and high recurrence rates. Genetic and epigenetic mutations play a crucial role in cancer pathogenesis, necessitating the development of alternate treatment methods. The advent of CRISPR/Cas9 technology has transformed molecular biology and exhibits potential for gene modification and therapy in various cancer types. Nonetheless, obstacles such as safe transport, off-target consequences, and potency must be overcome before widespread clinical use. Notably, this review delves into the multifaceted landscape of cancer research, highlighting the pivotal role of nanoparticles in advancing CRISPR/Cas9-based cancer interventions. By addressing the challenges associated with cancer diagnosis and treatment, this integrated approach paves the way for innovative solutions and improved patient outcomes.

DNA-Based Nonviral Gene Therapy─Challenging but Promising

Over the past decades, significant progress has been made in utilizing nucleic acids, including DNA and RNA molecules, for therapeutic purposes. For DNA molecules, although various DNA delivery systems have been established, viral vector systems are the go-to choice for large-scale commercial applications. However, viral systems have certain disadvantages such as immune response, limited payload capacity, insertional mutagenesis and pre-existing immunity. In contrast, nonviral systems are less immunogenic, not size limited, safer, and easier for manufacturing compared with viral systems. What's more, nonviral DNA vectors have demonstrated their capacity to mediate specific protein expression in vivo for diverse therapeutic objectives containing a wide range of diseases such as cancer, rare diseases, neurodegenerative diseases, and infectious diseases, yielding promising therapeutic outcomes. However, exogenous plasmid DNA is prone to degrade and has poor immunogenicity in vivo. Thus, various strategies have been developed: (i) designing novel plasmids with special structures, (ii) optimizing plasmid sequences for higher expression, and (iii) developing more efficient nonviral DNA delivery systems. Based on these strategies, many interesting clinical results have been reported. This Review discusses the development of DNA-based nonviral gene therapy, including novel plasmids, nonviral delivery systems, clinical advances, and prospects. These developments hold great potential for enhancing the efficacy and safety of nonviral gene therapy and expanding its applications in the treatment of various diseases.

AAV-RPGR Gene Therapy Rescues Opsin Mislocalisation in a Human Retinal Organoid Model of RPGR-Associated X-Linked Retinitis Pigmentosa

Variants within the Retinitis Pigmentosa GTPase regulator (RPGR) gene are the predominant cause of X-Linked Retinitis Pigmentosa (XLRP), a common and severe form of inherited retinal disease. XLRP is characterised by the progressive degeneration and loss of photoreceptors, leading to visual loss and, ultimately, bilateral blindness. Unfortunately, there are no effective approved treatments for RPGR-associated XLRP. We sought to investigate the efficacy of RPGRORF15 gene supplementation using a clinically relevant construct in human RPGR-deficient retinal organoids (ROs). Isogenic RPGR knockout (KO)-induced pluripotent stem cells (IPSCs) were generated using established CRISPR/Cas9 gene editing methods targeting RPGR. RPGR-KO and isogenic wild-type IPSCs were differentiated into ROs and utilised to test the adeno associated virus (AAV) RPGR (AAV-RPGR) clinical vector construct. The transduction of RPGR-KO ROs using AAV-RPGR successfully restored RPGR mRNA and protein expression and localisation to the photoreceptor connecting cilium in rod and cone photoreceptors. Vector-derived RPGR demonstrated equivalent levels of glutamylation to WT ROs. In addition, treatment with AAV-RPGR restored rhodopsin localisation within RPGR-KO ROs, reducing mislocalisation to the photoreceptor outer nuclear layer. These data provide mechanistic insights into RPGRORF15 gene supplementation functional potency in human photoreceptor cells and support the previously reported Phase I/II trial positive results using this vector construct in patients with RPGR-associated XLRP, which is currently being tested in a Phase III clinical trial.

Toward low-cost gene therapy: mRNA-based therapeutics for treatment of inherited retinal diseases

Inherited retinal diseases (IRDs) stem from genetic mutations that result in vision impairment. Gene therapy shows promising therapeutic potential, exemplified by the encouraging initial results with voretigene neparvovec. Nevertheless, the associated costs impede widespread access, particularly in low-to-middle income countries. The primary challenge remains: how can we make these therapies globally affordable? Leveraging advancements in mRNA therapies might offer a more economically viable alternative. Furthermore, transitioning to nonviral delivery systems could provide a dual benefit of reduced costs and increased scalability. Relevant stakeholders must collaboratively devise and implement a research agenda to realize the potential of mRNA strategies in equitable access to treatments to prevent vision loss.

Multi-luminance mobility testing after gene therapy in the context of retinal functional diagnostics

BACKGROUND

Voretigene neparvovec (Luxturna®) is the first approved gene therapy for RPE65-linked Leber congenital amaurosis (LCA). Though individual effects are highly variable, most recipients report improved vision in everyday life. To describe such effects, visual navigation tests are now frequently used in clinical trials. However, it is still unclear how their results should be interpreted compared to conventional parameters of visual function.

METHODS

Seven LCA patients underwent a multi-luminance visual navigation test (Ora-VNCTM) before and 3 months after receiving Luxturna gene therapy. Their performance was rated based on the luminance level at which they passed the course. Differences between the first and second test were correlated to changes in visual acuity, full-field stimulus thresholds, chromatic pupil campimetry, and dark-adapted perimetry.

RESULTS

A few patients displayed notable improvements in conventional measures of visual function whereas patients with advanced retinal degeneration showed no relevant changes. Independent of these results, almost all participants improved in the visual navigation task by one or more levels. The improvement in the mobility test was best correlated to the change in full-field stimulus thresholds. Other measures of visual functions showed no clear correlation with visual navigation.

DISCUSSION

In patients who passed the test's more difficult levels, improved visual navigation can be attributed to the reactivation of rods. However, the performance of patients with low vision seemed to depend much more on confounding factors in the easier levels. In sum, such tests might only be meaningful for patients with better preserved visual functions.

Applications of Gene Therapy in Cardiomyopathies

Gene therapy is defined by the introduction of new genes or the genetic modification of existing genes and/or their regulatory portions via gene replacement and gene editing strategies, respectively. The genetic material is usually delivered though cardiotropic vectors such as adeno-associated virus 9 or engineered capsids. The enthusiasm for gene therapy has been hampered somewhat by adverse events observed in clinical trials, including dose-dependent immunologic reactions such as hepatotoxicity, acquired hemolytic uremic syndrome and myocarditis. Notably, gene therapy for Duchenne muscular dystrophy has recently been approved and pivotal clinical trials are testing gene therapy approaches in rare myocardial conditions such as Danon disease and Fabry disease. Furthermore, promising results have been shown in animal models of gene therapy in hypertrophic cardiomyopathy and arrhythmogenic cardiomyopathy. This review summarizes the gene therapy techniques, the toxicity risk associated with adeno-associated virus delivery, the ongoing clinical trials, and future targets.

Inhibition of orthotopic castration-resistant prostate cancer growth and metastasis in mice by JC VLPs carrying a suicide gene driven by the PSA promoter

Metastatic castration-resistant prostate cancer (mCRPC) is challenging to treat. Virus-like particles (VLPs), originating from JC polyomavirus (JCPyV) and carrying a suicide gene driven by the PSA promoter (PSAtk-VLPs), can inhibit tumor growth in animal models of human prostate cancer. However, the efficacy of suppression of orthotopic PCa growth and metastasis by PSAtk-VLPs remains undetermined. Here, we established an iRFP stable expression CRPC cell line suitable for deep-tissue observation using fluorescence molecular tomography (FMT). These cells were implanted into murine prostate tissue, and PSAtk-VLPs were systemically administered via the tail vein along with the prodrug ganciclovir (GCV), allowing for the real-time observation of orthotopic prostate tumor growth and CRPC tumor metastasis. Our findings demonstrated that systemic PSAtk-VLPs administration with GCV and subsequent FMT scanning facilitated real-time observation of the suppressed growth in mouse iRFP CRPC orthotopic tumors, which further revealed a notable metastasis rate reduction. Systemic PSAtk-VLPs and GCV administration effectively inhibited orthotopic prostate cancer growth and metastasis. These findings suggest the potential of JCPyV VLPs as a promising vector for mCRPC gene therapy. Conclusively, systemically administered JCPyV VLPs carrying a tissue-specific promoter, JCPyV VLPs can protect genes within the bloodstream to be specifically expressed in specific organs.

Adeno-associated viruses for gene therapy - clinical implications and liver-related complications, a guide for hepatologists

Gene therapy has garnered increasing interest over recent decades. Several therapies employing gene transfer mechanisms have been developed, and, of these, adeno-associated virus (AAV) vectors have demonstrated viability for use with in vivo gene therapy. Several AAV-based therapeutics have received regulatory approval in the last few years including those for retinal disease, spinal muscular atrophy or aromatic L-amino acid decarboxylase deficiency. Lately, with the introduction of novel liver-directed AAV vector-based therapeutics for the treatment of haemophilia A and B, gene therapy has attracted significant attention in the hepatology community, with the liver increasingly recognised as a target for gene therapy. However, the introduction of foreign DNA into hepatocytes is associated with a risk of hepatic reactions, with raised ALT (alanine aminotransferase) and AST (aspartate aminotransferase) being - so far - the most commonly reported side effects. The complete mechanisms underlying the ALT flairs remain to be determined and the long-term risks associated with these new treatments is not yet known. The liver community is increasingly being asked to support liver-directed gene therapy to mitigate potential liver associated harm. In this review, we focus on AAV vector-based gene therapy, shedding light on this promising technique and its remarkable success in haemophilia, with a special focus on hepatic complications and their management in daily clinical practice.

Next-generation biological vector platforms for in vivo delivery of genome editing agents

CRISPR-based genome editing holds promise for addressing genetic disease, infectious disease, and cancer and has rapidly advanced from primary research to clinical trials in recent years. However, the lack of safe and potent in vivo delivery methods for CRISPR components has limited most ongoing clinical trials to ex vivo gene therapy. Effective CRISPR in vivo genome editing necessitates an effective vehicle ensuring target cell transduction while minimizing off-target effects, toxicity, and immune reactions. In this review, we examine promising biological-derived platforms to deliver DNA editing agents in vivo and the engineering thereof, encompassing potent viral-based vehicles, flexible protein nanocages, and mammalian-derived particles.

An Update on the Application of CRISPR Technology in Clinical Practice

The CRISPR/Cas system, an innovative gene-editing tool, is emerging as a promising technique for genome modifications. This straightforward technique was created based on the prokaryotic adaptive immune defense mechanism and employed in the studies on human diseases that proved enormous therapeutic potential. A genetically unique patient mutation in the process of gene therapy can be corrected by the CRISPR method to treat diseases that traditional methods were unable to cure. However, introduction of CRISPR/Cas9 into the clinic will be challenging because we still need to improve the technology's effectiveness, precision, and applications. In this review, we first describe the function and applications of the CRISPR-Cas9 system. We next delineate how this technology could be utilized for gene therapy of various human disorders, including cancer and infectious diseases and highlight the promising examples in the field. Finally, we document current challenges and the potential solutions to overcome these obstacles for the effective use of CRISPR-Cas9 in clinical practice.

RNA therapeutics for treatment of diabetes

Diabetes is an ongoing global problem as it affects health of more than 537 million people around the world. Diabetes leaves many serious complications that affect patients and can cause death if not detected and treated promptly. Some of the complications of diabetes include impaired vascular system, increased risk of stroke, neurological diseases that cause pain and numbness, diseases related to the retina leading to blindness, and other complications affecting kidneys, heart failure, muscle weakness, muscle atrophy. All complications of diabetes seriously affect the health of patients. Recently, gene therapy has emerged as a viable treatment strategy for various diseases. DNA and RNA are among the target molecules that can change the structure and function of proteins and are effective methods of treating diseases, especially genetically inherited diseases. RNA therapeutics has attracted deep interest as it has been approved for application in the treatment of functional system disorders such as spinal muscular atrophy, and muscular dystrophy. In this review, we cover the types of RNA therapies considered for treatment of diabetes. In particular, we delve into the mechanism of action of RNA therapies for diabetes, and studies involving testing of these RNA therapies. Finally, we have highlighted the limitations of the current understanding in the mechanism of action of RNA therapies.

Caridac vein retroinjections provide an efficient approach for global left ventricular gene transfer with adenovirus and adeno-associated virus

Heart failure (HF) is a major burden worldwide, and new therapies are urgently needed. Gene therapy is a promising new approach to treat myocardial diseases. However, current cardiac gene delivery methods for producing global myocardial effects have been inefficient. The aim of this study was to develop an endovascular, reproducible, and clinically applicable gene transfer method for global left ventricular (LV) transduction. Domestic pigs (n = 52) were used for the experiments. Global LV myocardium coverage was achieved by three retrograde injections into the three main LV vein branches. The distribution outcome was significantly improved by simultaneous transient occlusions of the corresponding coronary arteries and the main anastomotic veins of the retroinjected veins. The achieved cardiac distribution was visualized first by administering Indian Ink solution. Secondly, AdLacZ (2 × 1012vp) and AAV2-GFP (2 × 1013vg) gene transfers were performed to study gene transduction efficacy of the method. By retrograde injections with simultaneous coronary arterial occlusions, both adenovirus (Ad) and adeno-associated virus (AAV) vectors were shown to deliver an efficient transduction of the LV. We conclude that retrograde injections into the three main LV veins is a potential new approach for a global LV gene transfer.

Lentiviral gene therapy with IGF2-tagged GAA normalizes the skeletal muscle proteome in murine Pompe disease

Pompe disease is a lysosomal storage disorder caused by deficiency of acid alpha-glucosidase (GAA), resulting in glycogen accumulation with profound pathology in skeletal muscle. We recently developed an optimized form of lentiviral gene therapy for Pompe disease in which a codon-optimized version of the GAA transgene (LV-GAAco) was fused to an insulin-like growth factor 2 (IGF2) peptide (LV-IGF2.GAAco), to promote cellular uptake via the cation-independent mannose-6-phosphate/IGF2 receptor. Lentiviral gene therapy with LV-IGF2.GAAco showed superior efficacy in heart, skeletal muscle, and brain of Gaa -/- mice compared to gene therapy with untagged LV-GAAco. Here, we used quantitative mass spectrometry using TMT labeling to analyze the muscle proteome and the response to gene therapy in Gaa -/- mice. We found that muscle of Gaa -/- mice displayed altered levels of proteins including those with functions in the CLEAR signaling pathway, autophagy, cytoplasmic glycogen metabolism, calcium homeostasis, redox signaling, mitochondrial function, fatty acid transport, muscle contraction, cytoskeletal organization, phagosome maturation, and inflammation. Gene therapy with LV-GAAco resulted in partial correction of the muscle proteome, while gene therapy with LV-IGF2.GAAco resulted in a near-complete restoration to wild type levels without inducing extra proteomic changes, supporting clinical development of lentiviral gene therapy for Pompe disease. SIGNIFICANCE: Lysosomal glycogen accumulation is the primary cause of Pompe disease, and leads to a cascade of pathological events in cardiac and skeletal muscle and in the central nervous system. In this study, we identified the proteomic changes that are caused by Pompe disease in skeletal muscle of a mouse model. We showed that lentiviral gene therapy with LV-IGF2.GAAco nearly completely corrects disease-associated proteomic changes. This study supports the future clinical development of lentiviral gene therapy with LV-IGF2.GAAco as a new treatment option for Pompe disease.

Brain-targeted delivery of neuroprotective survival gene minimizing hematopoietic cell contamination: implications for Parkinson's disease treatment

BACKGROUND

Neurodegenerative diseases, including Parkinson's disease, Amyotropic Lateral Sclerosis (ALS) and Alzheimer's disease, present significant challenges for therapeutic development due to drug delivery restrictions and toxicity concerns. Prevailing strategies often employ adeno-associated viral (AAV) vectors to deliver neuroprotective survival genes directly into the central nervous system (CNS). However, these methods have been limited by triggering immunogenic responses and risk of tumorigenicity, resulting from overexpression of survival genes in peripheral blood mononuclear cells (PBMC), thereby increasing the risk of tumorigenicity in specific immune cells. Thus, by coding selectively suppressive microRNA (miRNA) target sequences in AAV genome, we designed CNS-targeted neuroprotective gene expression vector system without leakage to blood cells.

METHODS

To minimize the potential for transgene contamination in the blood, we designed a CNS-specific AAV system. Our system utilized a self-complementary AAV (scAAV), encoding a quadruple repeated target sequence of the hematopoietic cell-specific miR142-3p at the 3' untranslated region (UTR). As a representative therapeutic survival gene for Parkinson's disease treatment, we integrated DX2, an antagonistic splice variant of the apoptotic gene AIMP2, known to be implicated in Parkinson's disease, into the vector.

RESULTS

This configuration ensured that transgene expression was stringently localized to the CNS, even if the vector found its way into the blood cells. A single injection of scAAV-DX2 demonstrated marked improvement in behavior and motor activity in animal models of Parkinson's disease induced by either Rotenone or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Importantly, comprehensive preclinical data adhering to Good Laboratory Practice (GLP) standards revealed no adverse effects in the treated animals.

CONCLUSIONS

Our CNS-specific vector system, which encodes a survival transgene DX2, signifies a promising avenue for safe gene therapy, avoiding unintended expression of survival gene in blood cells, applicable to various neurodegenerative diseases.

Recent advances in various adeno-associated viruses (AAVs) as gene therapy agents in hepatocellular carcinoma

Primary liver cancer, which is scientifically referred to as hepatocellular carcinoma (HCC), is a significant concern in the field of global health. It has been demonstrated that conventional chemotherapy, chemo-hormonal therapy, and conformal radiotherapy are ineffective against HCC. New therapeutic approaches are thus urgently required. Identifying single or multiple mutations in genes associated with invasion, metastasis, apoptosis, and growth regulation has resulted in a more comprehensive comprehension of the molecular genetic underpinnings of malignant transformation, tumor advancement, and host interaction. This enhanced comprehension has notably propelled the development of novel therapeutic agents. Therefore, gene therapy (GT) holds great promise for addressing the urgent need for innovative treatments in HCC. However, the complexity of HCC demands precise and effective therapeutic approaches. The adeno-associated virus (AAV) distinctive life cycle and ability to persistently infect dividing and nondividing cells have rendered it an alluring vector. Another appealing characteristic of the wild-type virus is its evident absence of pathogenicity. As a result, AAV, a vector that lacks an envelope and can be modified to transport DNA to specific cells, has garnered considerable interest in the scientific community, particularly in experimental therapeutic strategies that are still in the clinical stage. AAV vectors emerge as promising tools for HCC therapy due to their non-immunogenic nature, efficient cell entry, and prolonged gene expression. While AAV-mediated GT demonstrates promise across diverse diseases, the current absence of ongoing clinical trials targeting HCC underscores untapped potential in this context. Furthermore, gene transfer through hepatic AAV vectors is frequently facilitated by GT research, which has been propelled by several congenital anomalies affecting the liver. Notwithstanding the enthusiasm associated with this notion, recent discoveries that expose the integration of the AAV vector genome at double-strand breaks give rise to apprehensions regarding their enduring safety and effectiveness. This review explores the potential of AAV vectors as versatile tools for targeted GT in HCC. In summation, we encapsulate the multifaceted exploration of AAV vectors in HCC GT, underlining their transformative potential within the landscape of oncology and human health.

Combination HSCT and intravenous AAV-mediated gene therapy in a canine model proves pivotal for translation of Krabbe disease therapy

Hematopoietic stem cell transplantation (HSCT) is the only approved treatment for presymptomatic infantile globoid cell leukodystrophy (GLD [Krabbe disease]). However, correction of disease is not complete, and outcomes remain poor. Herein we evaluated HSCT, intravenous (IV) adeno-associated virus rh10 vector (AAVrh10) gene therapy, and combination HSCT + IV AAVrh10 in the canine model of GLD. While HSCT alone resulted in no increase in survival as compared with untreated GLD dogs (∼16 weeks of age), combination HSCT + IV AAVrh10 at a dose of 4E13 genome copies (gc)/kg resulted in delayed disease progression and increased survival beyond 1 year of age. A 5-fold increase in AAVrh10 dose to 2E14 gc/kg, in combination with HSCT, normalized neurological dysfunction up to 2 years of age. IV AAVrh10 alone resulted in an average survival to 41.2 weeks of age. In the peripheral nervous system, IV AAVrh10 alone or in addition to HSCT normalized nerve conduction velocity, improved ultrastructure, and normalized GALC enzyme activity and psychosine concentration. In the central nervous system, only combination therapy at the highest dose was able to restore galactosylceramidase activity and psychosine concentrations to within the normal range. These data have now guided clinical translation of systemic AAV gene therapy as an addition to HSCT (NCT04693598, NCT05739643).