ASGCT 2025: Insights from Featured Talks and Posters

1. Nucleoside-modified mRNA-LNP Therapeutics

Dr. Drew Weissman from University of Pennsylvania presented his vision for the future of mRNA therapeutics, emphasizing its broad potential beyond vaccines. He began by highlighting the long history of mRNA research, debunking the notion that mRNA vaccines were a rapid, new invention. He then discussed his early work with Katalin Karikó on understanding and overcoming the inflammatory nature of mRNA by using nucleoside modifications, which surprisingly also enhanced translation.

A significant portion of his talk focused on targeted delivery of mRNA lipid nanoparticles (LNPs) to specific tissues and cell types in vivo. He described modifying LNPs with targeting moieties like antibodies, antibody fragments, receptor ligands, aptamers, and peptides to direct them to organs such as the lung and, importantly, to immune cells.

Weissman detailed their innovative approach to creating CAR T cells in vivo. By targeting T cells with modified LNPs carrying mRNA encoding the CAR, they achieved CAR T cell expression directly within the animal, bypassing the expensive and complex ex vivo manufacturing process. This in vivo CAR T cell approach showed promising results in treating cardiac fibrosis in mice and demonstrated rapid, transient B cell depletion in macaques, suggesting a potential off-the-shelf therapy for autoimmune diseases with improved safety compared to traditional CAR T cells. A clinical trial for autoimmune diseases using this technology is underway in Australia.

Furthermore, Weissman presented their work on targeting bone marrow stem cells in vivo using LNPs with CD117. This led to highly efficient gene editing in bone marrow stem cells in mice without the need for bone marrow extraction or chemotherapy. He highlighted the potential of this technology for treating sickle cell anemia via in vivo base editing, envisioning a simplified, accessible treatment option for underserved populations.

Finally, Weissman passionately discussed vaccine and therapeutic equity. He highlighted the disparity in disease burden and research funding, emphasizing the lack of focus on diseases prevalent in low and middle-income countries. He detailed his collaborative efforts to establish mRNA GMP production sites in these regions, starting in Thailand, and his work with the WHO to build 15 such sites globally. He also secured license-free access to Penn’s mRNA therapeutic IP for these countries, aiming to empower local development of affordable vaccines and therapeutics for diseases like malaria, TB, and sickle cell anemia.

 

2. Expedited Development of Bespoke Base Editing Therapy for a Newborn with CPS1 Deficiency

Dr. Kiran Musunuru from UPenn and Dr. Rebecca Ahrens-Nicklas at the Children’s Hospital of Philadelphia (CHOP) presented a compelling case study demonstrating the rapid development and delivery of a personalized base editing therapy for a newborn, named KJ, with a severe CPS1 deficiency. Faced with the urgency of this urea cycle disorder, Musunuru’s lab leveraged their established platform of mRNA-based CRISPR base editing and lipid nanoparticle (LNP) delivery. Within a remarkably short timeframe – just four weeks after the patient’s birth – they identified an effective base editor and guide RNA combination to correct the patient’s specific CPS1 variant (q335X) in lab-grown hepatocytes, which was further optimized within six weeks. In parallel, they rapidly generated a mouse model carrying the patient’s CPS1 variant to test the therapy in vivo, achieving significant (up to 42%) corrective editing in the liver within five months using LNPs, with any bystander editing found to be synonymous. Comprehensive off-target analysis, tailored where possible to the KJ’s specific genome, was completed within six months and indicated a favorable safety profile. Dr. Musunuru, Dr. Ahrens-Nicklas and the partners produced a clinical-grade LNP drug product containing the bespoke base editor and guide RNA, securing FDA expanded access approval and administering this personalized therapy to KJ, when he was only six to seven months old, showcasing the power of rapid base editing development and LNP delivery to address a life-threatening, ultra-rare genetic disorder like CPS1 deficiency in a timely manner, highlighting a potential paradigm shift towards patient-specific gene editing therapies. 

 

3. CRISPR-hfCas12Max Genome Editing Therapy Demonstrates Preclinical Efficacy and Early Clinical Benefit in Duchenne Muscular Dystrophy (DMD)

Dr. Alvin Luke from HuidaGene Therapeutics presented HG302, a one-time CRISPR therapy utilizing Cas12max delivered via a single adeno-associated virus serotype 9 (AAV9) vector to target exon 51 skipping in the DMD gene. Preclinical studies in a humanized DMD mouse model demonstrated that this AAV-delivered HG302, at a six-fold lower dose than a dual AAV approach, effectively restored dystrophin production and improved motor function, approaching wild-type levels. The AAV therapy showed widespread distribution in muscles with minimal immune response and a favorable safety profile in both mice and non-human primates following AAV administration, with no significant hepato-renal toxicity observed with the AAV delivery. Extensive off-target analysis indicated high in vivo specificity of the AAV-mediated gene editing.

Based on this promising preclinical data with the AAV gene therapy, HG302 advanced to a first-in-human clinical trial (Muscle trial) in ambulatory DMD boys aged 4-8 with specific exon deletions. Early data from two low-dose patients who received the AAV-delivered therapy showed it was well-tolerated with mild, transient adverse events. Encouraging functional trends were observed following the AAV treatment, including gains in the six-minute walk distance, improved stair climbing, and increased NSAA scores in one patient. Muscle biopsies confirmed stable AAV vector DNA delivery and traces of dystrophin protein expression, although RNA levels were low. Off-target analysis in patient biopsies following AAV delivery confirmed the intended on-target editing with no significant off-target activity. The speaker concluded that HG302 demonstrates precision, safety, and translational promise as a single AAV in vivo CRISPR therapy for DMD, highlighting the need for further optimization of expression kinetics and tissue sampling of the AAV-packaged genetic material.

 

4. Hematopoietic Stem Cell Lentiviral Gene Therapy for the Treatment of Angelman Syndrome

Christopher Luthers from UCLA presented a novel cross-correction gene therapy strategy for Angelman Syndrome, a neurodevelopmental disorder caused by the loss of the maternally inherited UBE3A gene in the brain. The paternal copy of UBE3A is silenced in neurons, making loss of the maternal copy critical.

The presented approach involves using hematopoietic stem cell (HSC)-derived macrophages genetically modified with lentivirus vectors (LVV) to express the UBE3A protein. The hypothesis is that this secreted UBE3A can then be taken up by UBE3A-deficient neurons in the brain, restoring its function. This strategy builds upon previous promising lentivirus gene therapy work that, however, raised safety concerns regarding insertional oncogenesis due to the use of the strong MND promoter within the lentivirus vector.

To address these safety concerns, Luthers’ team developed LVV utilizing alternative promoters (human PGK and EFS), both with established clinical safety profiles for lentivirus-mediated gene transfer. These new LVV demonstrated equivalent or increased UBE3A expression in vitro compared to the MND promoter-driven LVV.

In vivo studies in an Angelman syndrome mouse model involved transplanting these transduced HSCs. The results showed successful multi-tissue engraftment of the lentivirus-modified cells, including approximately 5% engraftment in the brain (a significant proportion considering immune cell representation in the brain). Importantly, UBE3A protein was detected in the neurons of the mice that received the lentivirus gene therapy.

Behavioral assessments (rotarod, balanced beam, open field, novel object recognition) demonstrated significant improvements in motor function and cognitive abilities in mice treated with the PGK and EFS promoter-driven lentivirus vectors, reaching levels comparable to wild-type mice in some assays. Furthermore, electroencephalogram (EEG) analysis, a key biomarker in Angelman Syndrome, showed a significant decrease in delta power in the treated mice that received the lentivirus therapy, mirroring the pattern seen in neurotypical individuals.

While these preclinical findings using LVV are promising, Luthers emphasized the need for further characterization, including confirming the biological activity and quantifying UBE3A expression in the brain following lentivirus-mediated gene transfer. Future steps involve validating the clinical feasibility and safety profile of both murine and human LVV to advance towards FDA IND investigations and eventual Phase 1 clinical trials for Angelman Syndrome. The presented work offers a potentially safer and effective lentivirus-based gene therapy approach for this challenging neurological disorder.

 

5. Preclinical Advances for the Translation of an AAV-Mediated Gene Therapy for CTNNB1 Syndrome

Dr. Andrea Perez Iturralde from the Children’s Medical Research Institute presented her work on developing an AAV-mediated gene therapy for CTNNB1 syndrome, a rare neurodevelopmental disorder caused by loss-of-function mutations in the CTNNB1 gene (encoding beta-catenin). They designed and screened several therapeutic cassettes, selecting the most promising in patient-derived brain organoids using AAV7m8 for efficient transduction. This lead cassette, packaged into an AAV9 vector, was then tested in a CTNNB1 mouse model, demonstrating a dose-dependent improvement in anxiety-like behaviors and gait abnormalities. Comprehensive toxicology studies in mice and non-human primates are in their final stages, with no significant safety signals identified to date. The project, funded by the CTNNB1 Foundation, is now moving towards clinical trial preparation with the clinical package being assembled for submission in Europe. The therapeutic strategy employs a ubiquitous promoter to target beta-catenin expression in both the brain and muscles, crucial for addressing the syndrome’s wide-ranging effects.

 

6. Treatment of Rheumatoid Arthritis in a Collagen-Induced Arthritis Mouse Model Using Intra-Articular Injection of AAV6-Delivered sIL17RA

Susi Feng and colleagues from the University of North Carolina at Chapel Hill presents a potential new localized treatment for Rheumatoid Arthritis (RA) using gene therapy in a mouse model.

The study investigated whether delivering a soluble Interleukin-17 Receptor A (sIL17RA) via an AAV6 directly into the affected joint could reduce inflammation in mice with collagen-induced arthritis (CIA), a model for RA.

The researchers successfully created a genetic construct that, when introduced into cells, produced a functional sIL17RA protein capable of blocking the activity of IL17A, a key inflammatory molecule in RA. This was confirmed in lab experiments (in vitro). In the mouse model of RA (CIA), injecting the AAV6 carrying the sIL17RA gene into one knee joint showed a promising trend towards reduced arthritis severity in that treated joint compared to the untreated joint in the same mice and control mice that received a control virus. The treatment appeared to be localized, as the produced sIL17RA was not detected in the bloodstream, and there was no significant difference in the overall immune response (anti-collagen antibody levels) between the treated and control groups.

In conclusion, the study suggests that delivering sIL17RA directly to the joint using AAV6 could be a potential localized therapeutic strategy for RA. The researchers highlight the need for future studies to optimize the gene delivery, explore preventative treatment strategies, and increase the number of animals studied to confirm these initial promising results.

 

7. Design of the First Clinical Trial of AAV Gene Therapy in Immuno-Oncology (SENTRY-ALL)

Allen Reha from Vironexis Biotherapeutics introduces the SENTRY-ALL trial, a Phase 1/2 clinical study investigating VNX-101, an innovative AAV gene therapy that delivers the genetic code for GP101, a secreted anti-CD19/anti-CD3 scFv diabody for patients with relapsed or refractory CD19+ B-cell acute lymphoblastic leukemia (ALL). The mechanism is to have GP101 bind to both cancerous B-cells (via CD19) and T-cells (via CD3), triggering the T-cells to eliminate the cancer cells.

Preclinical studies in mice demonstrated that VNX-101 could reduce leukemia/lymphoma cells and extend survival. Subsequent safety and pharmacokinetic studies in larger animals supported its advancement to human trials, resulting in FDA IND clearance.

The SENTRY-ALL trial is a two-part study. Part 1 will focus on determining the optimal dose of VNX-101 in adult patients by assessing drug levels in the body and identifying any dose-limiting toxicities. Part 2 will then evaluate the safety and how the drug moves through the body (pharmacokinetics) at the chosen dose in a larger group of patients, including adolescents. The study will also track how the treatment affects B-cell counts, disease progression, and survival over several years. Researchers believe VNX-101 has the potential to be a more accessible and potentially safer alternative to existing CD19-targeted therapies like CAR-T. The trial is set to begin enrolling patients in the first quarter of 2025. 

 

8. Tumor-specific AAV Delivery of Interleukin-12 Enhances Antitumor Immunity and Safety in Ovarian Cancer

Lei Zhao from Cure Genetics presents research on a novel approach to deliver Interleukin-12 (IL-12) for ovarian cancer therapy in a mouse model. IL-12 is a potent anti-cancer cytokine, but its clinical use is limited by toxicity and short duration in the body.

To overcome these limitations, the researchers developed a tumor-targeted tAAV9 to specifically deliver IL-12 to the tumor microenvironment (TME). This targeted delivery system was created by attaching an antibody fragment that recognizes FOLR1, a protein commonly found on ovarian cancer cells, to the AAV9 viral vector using a highly efficient Spy-ligation technique.

In their study using mice with ovarian cancer, intravenous injection of this tAAV9 carrying the IL-12 gene (tAAV9-IL-12) resulted in the specific delivery of IL-12 to the tumor. This targeted delivery led to a significant suppression of tumor growth and showed a better safety profile compared to using a standard, non-targeted AAV9 to deliver IL-12 (rAAV9). Importantly, the levels of IL-12 in the bloodstream were also significantly lower with the targeted approach, suggesting a promising negative feedback mechanism that could enhance safety.

In conclusion, this research demonstrates the potential of using a tumor-targeted AAV to deliver IL-12 specifically to the tumor microenvironment, leading to effective tumor suppression with improved safety in a preclinical model of ovarian cancer.

 

9. Development of a Novel AAV Gene Therapy for the Treatment of Dilated Cardiomyopathy

Simone Chiola from Stanford University presents research on a potential gene therapy for dilated cardiomyopathy (DCM), a severe heart condition. The study focuses on increasing the levels of a protein called activating transcription factor 4 (ATF4) in heart cells using AAV vectors.

Previous research suggested that increasing ATF4 levels could improve heart muscle function in lab-grown heart cells with DCM-related genetic defects. In this study, the researchers engineered several AAV vectors to deliver the human ATF4 gene (hATF4) specifically to the heart. They optimized the gene sequence and tested different heart-specific promoters to ensure high and targeted expression of ATF4.

The most promising AAV vector was then tested in mice that develop a form of DCM (TM54 transgenic mice). These mice, along with healthy control mice, received a single injection of the AAV vector at 6 weeks of age, when signs of DCM are present. Over the following weeks, the researchers used echocardiography to monitor the heart function of the mice.

The results showed that the engineered AAV vector successfully delivered the hATF4 gene to the heart tissue, with minimal expression in other organs like the liver and skeletal muscles. Importantly, the treatment did not show any significant signs of toxicity in the liver or kidneys. This study suggests that increasing ATF4 levels through gene therapy could be a promising therapeutic strategy for DCM. The researchers emphasize the need for further studies in larger animal models to fully evaluate the safety and effectiveness of this approach before it can be considered for human clinical trials.

 

10. AAV Gene Therapy for LMNA Associated Laminopathies

Monique Otero from UMass Chan Medical School is developing a gene therapy for L-CMD, a severe muscular dystrophy caused by dominant mutations in the LMNA gene. Their strategy, called “silence and replace,” aims to both reduce the production of the harmful, mutated Lamin A protein and restore the levels of healthy Lamin A and C proteins.

To achieve this, they designed a dual-function AAV vector. This vector contains an artificial microRNA (miRNA) that specifically targets and degrades the messenger RNA (mRNA) produced from the mouse’s own, mutated Lmna gene, effectively silencing its expression. Simultaneously, the vector carries a modified LMNA gene (a transgene) that is resistant to this miRNA-mediated silencing. This transgene is engineered to undergo normal alternative splicing, ensuring the production of both Lamin A and Lamin C proteins, mimicking the natural process.

The researchers screened various miRNAs to identify one that potently silenced both human and mouse LMNA in laboratory cell cultures. They then incorporated this top miRNA into different AAV vector backbones, testing how the miRNA’s position and surrounding genetic elements affected its silencing efficiency and the expression of the Lamin A/C transgene. They identified four promising AAV vector designs that showed good silencing of the endogenous LMNA and produced balanced levels of Lamin A and C in human cells.

These four lead vector candidates will now be packaged into a muscle-specific AAV delivery vehicle and tested in a mouse model that closely mimics the severe form of L-CMD. The success of the therapy will be determined by whether it can extend the lifespan of these mice and improve their muscle function. The ultimate goal is to identify the vector design that provides the most effective silencing of the disease-causing gene while restoring the correct balance of Lamin A and Lamin C in muscle tissue, which could lead to a significant therapeutic advancement for L-CMD.

 

11. AAV9-based gene therapy for PDHA1 deficiency

Siyuan Hao from UT Southwestern Medical Center presents research on developing an AAV gene therapy for Pyruvate Dehydrogenase Complex Deficiency (PDCD), a severe genetic disorder that often leads to early death. The primary cause of PDCD is mutations in the PDHA1 gene. Currently, there are limited effective treatments for this condition.

The researchers aimed to use AAV gene therapy to deliver a healthy copy of the PDHA1 gene to affected cells. Initial studies in patient-derived cells showed that an AAV vector carrying the PDHA1 gene could increase the production of the PDHA1 protein, properly locate it within the cell’s mitochondria, restore the enzyme’s activity, and improve mitochondrial function.

To study the therapy in living organisms, they created mouse models of PDCD using a special genetic technique that allowed them to turn off the PDHA1 gene after the mice were born. This resulted in male mice with a severe form of the disease and female mice with a milder form. When they injected an AAV vector carrying the PDHA1 gene into the spinal fluid of these newborn mice, they observed a small but significant increase in survival and improved enzyme activity in the major organs of the male mice. Long-term studies in the female mice are still ongoing, but initial results suggest a slight improvement in their weight and partially restored enzyme activity.

Furthermore, they conducted a long-term safety study in healthy mice and found no obvious side effects or deaths over a 12-month period, indicating that the AAV gene therapy approach appears to be safe.

In conclusion, this research demonstrates that AAV-based gene therapy can significantly improve cellular function and extend survival in PDCD mouse models without apparent toxicity. These findings support the further development of this AAV9/PDHA1 gene therapy as a potential treatment for PDHA1 deficiency.

 

12. Initial clinical results from OTC-HOPE, the first in vivo, liver directed, AAV-mediated gene insertion study in neonatal OTC deficiency

Julien Baruteau from Great Ormond Street Institute of Child Health University College London presents initial clinical results from the OTC-HOPE trial, a first-in-human study of an AAV-mediated gene editing therapy, ECUR-506, for severe neonatal-onset Ornithine Transcarbamylase Deficiency (OTCD) in a male infant. OTCD is a genetic disorder that impairs the urea cycle, leading to toxic ammonia buildup. Current treatments are limited, and liver transplantation is sometimes necessary.

ECUR-506 is an investigational gene editing product using two AAVrh79 vectors. One vector delivers a meganuclease (M2PCSK9) to target the PCSK9 gene in the liver, and the other delivers a healthy human OTC gene. The goal is for the OTC gene to be integrated into the liver cell genome, leading to long-term production of functional OTC enzyme.

The OTC-HOPE trial is a 24-week Phase 1/2 study assessing the safety and efficacy of ECUR-506 in young male infants with severe neonatal-onset OTCD. This presentation focuses on the first patient who completed the 6-month trial after receiving a single intravenous infusion of ECUR-506 at 6.5 months of age, having experienced two hyperammonemic episodes prior to treatment.

Following ECUR-506 infusion, the infant experienced asymptomatic liver inflammation that resolved with immunosuppression. Notably, the infant’s ammonia levels normalized, and glutamine levels decreased, allowing for the discontinuation of nitrogen scavenger medications by week 12 and increased protein intake by week 15. Throughout the remainder of the 6-month study, the infant maintained normal mean ammonia levels, experienced no further hyperammonemic events, showed increased blood urea nitrogen (BUN) and urinary nitrogen levels (indicating increased urea cycle activity), and exhibited normal growth.

The researchers conclude that these initial results from the first treated infant suggest that ECUR-506 may have led to at least partial restoration of functional OTC enzyme activity in the liver, as evidenced by the improved nitrogen processing and the ability to discontinue standard-of-care medications. The achievement of a complete clinical response in this patient, as defined by the study protocol, supports the continued evaluation of this low dose of ECUR-506 in the ongoing clinical trial.

 

13. Harnessing AAV-RNAi Technology for the Treatment of Neurodegenerative Diseases

Jessica Hogestyn from Sanofi presents research on using AAV-mediated RNA interference (RNAi) as a therapeutic platform for various neurodegenerative diseases characterized by the accumulation of toxic proteins, such as Huntington’s, Parkinson’s, and Alzheimer’s. The poster highlights the potential of this approach to overcome the complexity of protein aggregates by reducing all isoforms of the target protein with a single treatment.

For Huntington’s disease (HD), caused by a mutation in the huntingtin (HTT) gene, they designed artificial microRNAs (amiRNAs) to lower HTT mRNA levels. Through an optimization process, they identified potent amiRNAs that effectively reduced HTT in lab studies and in a rat model of HD, suggesting AAV-RNAi as a promising treatment strategy.

In the case of synucleinopathies, including Parkinson’s disease, which involve the accumulation of alpha-synuclein protein, they used an AAV vector that can cross the blood-brain barrier to achieve a 50% reduction of wild-type alpha-synuclein in a mouse model. This reduction prevented the development of alpha-synuclein pathology, protected dopamine-producing neurons, and stopped the spread of toxic protein aggregates. They also demonstrated that linking multiple amiRNAs together (concatenation) could further improve the potency of their gene therapy candidates.

For tauopathies like Alzheimer’s disease, where the tau protein accumulates, their AAV-RNAi approach targeted the microtubule-associated protein tau (MAPT). This resulted in a reduction of tau aggregates and markers of neurodegeneration in a mouse model. They emphasized the minimization of off-target effects through rigorous screening and identified a lead amiRNA with a good safety profile that achieved significant target knockdown without affecting other genes. Studies in nonhuman primates further supported the feasibility of reducing tau levels in the brain using this method.

In conclusion, the presented studies underscore the broad applicability and potential of AAV-RNAi technology for the treatment of neurodegenerative proteinopathies. Ongoing efforts to improve the delivery vectors and demonstrate efficacy in preclinical models suggest a promising path towards clinical translation and potential new therapies for these debilitating diseases.

 

14. Over a Decade of Gene Therapy Trials: Evolution from 2010 to 2025

Maryam Bemanalizadeh from Tehran University of Medical Sciences presents a review of gene therapy clinical trials conducted between 2010 and January 2025, updating a previous analysis to reflect the significant growth and expanding scope of the field.

The researchers analyzed data from Clinicaltrials.gov, focusing on key parameters such as the type of vector used, the approach (ex-vivo or in-vivo), the clinical trial phase, the disease category, and the specific condition being treated.

Their analysis of 2,987 clinical trials revealed that lentiviral vectors were the most commonly used (29%), followed by adenoviral vectors (15%), retroviral vectors (10%), and AAV (9%). Among non-viral methods, RNA-based approaches led (14%). Notably, gene editing technologies like CRISPR have recently entered clinical trials. Lentiviral vector use has significantly increased since 2019, coinciding with the rise of CAR T-cell therapies, which are also being increasingly explored for autoimmune diseases.

Over the past decade, in-vivo gene therapy approaches were initially more prevalent, but ex-vivo methods have steadily grown and now surpass in-vivo trials. Ex-vivo therapies are dominated by T cell-based approaches (85%), while in-vivo therapies most commonly target tumors (often using oncolytic viruses), followed by the immune system (in vaccine trials), the eye, and the central nervous system.

While cancer-related gene therapy trials are the most numerous in early phases (1 and 2), they don’t progress to later stages as frequently as trials for genetic diseases and infectious diseases, which show notable advancement into phases 2 and 3.

The authors conclude that analyzing the trends in successful clinical trials is crucial for guiding future research, optimizing study design, and informing policy development to improve the translation of gene therapies into effective clinical practice.

References:

https://www.dropbox.com/scl/fi/0ghk0d7a5r4x65q07gynw/USE-THIS-VERSION-PUB_AM25_v3.pdf?rlkey=dh1quvu0kj2lnuxywgdy4pmlb&e=1&st=qkwotqup&dl=0