Advancing Ocular Gene Therapy Through Principled Preclinical Design.
Why are rabbits a preferred large-animal model for ocular AAV gene therapy studies?
Rabbits are frequently selected for ocular gene therapy programs due to their eye size and anatomical structures, which are more analogous to the human eye than those of rodent models. This similarity provides more translatable data for surgical delivery techniques, vector biodistribution, and potential inflammatory responses within a comparable intraocular volume.
What are the primary immunogenicity challenges in rabbit ocular studies?
A significant challenge is the presence of pre-existing neutralizing antibodies (NAbs) to common AAV serotypes in animal populations. These NAbs can neutralize the vector before it reaches its target cells, confounding efficacy assessments and obscuring the true therapeutic potential of a vector. Post-administration, anti-capsid immune responses can also impact long-term transgene expression and safety.
How can study design be refined to improve animal welfare and data quality?
Refinement involves multiple strategies, including the use of advanced, tailored anesthesia and post-operative analgesia protocols. Incorporating non-invasive imaging techniques like optical coherence tomography (OCT) and electroretinography (ERG) allows for longitudinal assessment of safety and efficacy, reducing the number of animals required for terminal timepoints. Establishing clear, objective humane endpoints is also fundamental to ethical study conduct.
What is the scientific rationale for using immunosuppression in these models?
Prophylactic immunosuppression regimens may be employed to mitigate the host immune response against the AAV capsid. By managing the development of anti-capsid antibodies, it is possible to enhance the durability and efficacy of the gene therapy, potentially improving long-term therapeutic outcomes.
The translatability of ocular AAV gene therapy programs depends on ethically sound preclinical models that accurately predict human immunological and physiological responses. For rabbit models, this requires rigorous screening for pre-existing neutralizing antibodies (NAbs) and the implementation of refined surgical and post-operative care protocols. Proactive immunomodulation strategies and non-invasive endpoints are key components of a robust, data-driven IND-enabling package.
