Advancing Gene Delivery: LNPs, Adenovirus, Lentivirus, And More
By Erin Harris, Editor-In-Chief, Cell & Gene
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During this month’s Cell and Gene Live, Advancing Gene Delivery: LNPs, Adenovirus, Lentivirus, And More, I had the pleasure of moderating a deeply detailed presentation, which brought together two leading experts to discuss the evolving landscape of gene delivery systems, focusing on platforms such as lentivirus, adenovirus, herpes simplex virus (HSV), and lipid nanoparticles (LNPs). Our expert panel featured Francesca Barone, M.D., Ph.D., CSO at Candel Therapeutics and Karen Kozarsky, Ph.D., President of Vector BioPartners, who shared their perspectives on current challenges, technological innovations, and future directions in gene therapy vector development and application.
Underutilized Gene Delivery Platforms: Adenovirus and HSV: The Case for Intratumoral Delivery
Dr. Barone emphasized that both adenovirus and HSV platforms, particularly in the context of viral immunotherapies for solid tumors, remain underutilized. She attributed this to historical hesitancy around intratumoral delivery, which many in the pharmaceutical industry have considered technically challenging. However, she noted a renewed interest from major companies, such as Johnson & Johnson, in this approach. Intratumoral delivery allows for direct targeting of tumors, minimizing systemic toxicity and potentially enhancing therapeutic efficacy. Dr. Barone argued that overcoming technical and commercial barriers to intratumoral administration could unlock the full potential of these vectors, especially for oncolytic viruses that stimulate robust immune responses.
Lentivirus: Expanding In Vivo Applications
Dr. Kozarsky identified the in vivo use of lentiviral vectors as an underexploited opportunity. While lentiviruses have been highly effective in ex vivo applications — where patient cells are modified outside the body and then reinfused — the process is complex and resource-intensive. The field is now working to develop lentiviral vectors that can efficiently and selectively target cells in vivo, which would simplify manufacturing and broaden clinical applications. Achieving efficient in vivo targeting and delivery remains a key area for future innovation.
Lentiviral Vectors: Current Status and Challenges
Scientific Rationale and Use Cases
Lentiviral vectors are particularly valued for their ability to transduce dividing cells and integrate genetic material into the host genome, ensuring long-term expression that is passed on to daughter cells. This makes them especially suitable for targeting cells of the immune system in ex vivo gene therapy. Their relatively large cargo capacity (up to 8 kilobases) also allows for more complex genetic payloads compared to adeno-associated virus (AAV) vectors, which are limited to about 4.5 kilobases.
Manufacturing Bottlenecks and Best Practices
Manufacturing lentiviral vectors involves transfecting mammalian cells, typically using a four-plasmid system. This process is feasible but costly and time-consuming, especially when producing GMP-grade plasmids. To address these challenges, Kozarsky stressed that the field is moving toward the use of packaging and producer cell lines, which can streamline production. However, establishing these cell lines can take up to a year. Another best practice is the early adoption of suspension cell cultures, which are more scalable than adherent cells and facilitate large-scale production.
Safety, Durability, and Scalability
Dr. Kozarsky shared that lentiviral vectors offer unique durability advantages, as their integration into the genome ensures persistent expression even in dividing cells — a feature critical for therapies targeting bone marrow-derived or rapidly dividing tissues. However, this permanence is a double-edged sword; for genome editing applications, transient expression may be preferable, necessitating alternative vectors. From a safety perspective, ex vivo use minimizes systemic immune responses, but the individualized nature of manufacturing for each patient increases complexity and cost. As the field advances toward in vivo applications, these limitations may be mitigated.
Adenoviral Vectors: Innovations and Clinical Impact
Multimodal Immunotherapy and Oncolytic Applications
Dr. Barone described her team’s work with a novel adenoviral vector, CAN-2409, which exemplifies the trend toward multimodal immunotherapies. This replication-defective adenovirus is delivered directly into tumors and encodes the HSV thymidine kinase gene. When administered with the prodrug valacyclovir, the system induces immunogenic cell death and releases tumor antigens, effectively combining oncolytic and vaccine-like mechanisms. Clinical trials have demonstrated significant synergy with standard-of-care treatments, such as radiotherapy, and improved outcomes in localized prostate cancer, where the combination reduced tumor recurrence by up to 30% compared to radiotherapy alone.
HSV Vectors: Engineering for Safety and Efficacy
In the HSV domain, Dr. Barone highlighted a first-in-class oncolytic virus that retains the ICP34.5 gene, crucial for tumor replication but historically associated with neurovirulence. By placing this gene under the control of a tumor-specific promoter (nestin), her team has engineered the virus to replicate selectively in aggressive tumors, such as gliomas, while minimizing risks to healthy tissue. This approach exemplifies the sophisticated genetic engineering now possible with viral vectors, enabling precise targeting and enhanced safety profiles.
Adenoviral Vectors: Additional Use Cases and Considerations
Dr. Kozarsky noted that adenoviral vectors are also valuable for applications requiring transient gene expression, such as delivering vascular endothelial growth factor (VEGF) to restore blood flow in specific tissues. Compared to mRNA-based approaches, adenoviral vectors offer greater stability and can be tailored for short-term therapeutic needs. However, the field must contend with the challenge of preexisting immunity to common adenoviral serotypes, which can reduce efficacy and complicate repeat dosing strategies.
Emerging Trends and Future Directions in Gene Delivery
A recurring theme throughout our presentation was the need for a diverse “toolbox” of delivery vehicles, as no single platform is universally optimal. The choice of vector depends on the disease target, desired duration of expression, safety considerations, and manufacturing feasibility. Drs. Barone and Kozarsky shared that the field is moving toward more personalized and disease-specific solutions, leveraging advances in vector engineering, targeting, and manufacturing technology.
Indeed, thanks to Drs. Barone and Kozarsky, this Cell and Gene Live highlighted the dynamic and rapidly evolving field of gene delivery. Our experts underscored the untapped potential of adenovirus, HSV, and lentiviral vectors, particularly as technical and commercial barriers are addressed. Innovations in vector engineering, manufacturing, and targeting are expanding the therapeutic possibilities for gene and cell therapies. As research continues, the integration of viral and non-viral platforms, alongside advances in personalized medicine, promises to drive the next generation of transformative treatments for a wide range of diseases.