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AAV Gene Therapy

PROVEN INTELLIGENCE ACCELERATING NEXT-GENERATION THERAPIES

AAV Gene Therapy

AAV Gene Therapy: Long-Term Durability & Expression Studies in NHP Models

CELL & GENE | RNA | BIOLOGICS

Proven Intelligence in Preclinical AAV Toxicology.

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Frequently Asked Questions

Why are long-term durability studies in nonhuman primate models required for AAV gene therapy IND submissions?

Regulatory bodies, including the FDA and international agencies, require robust data demonstrating the stability and duration of transgene expression from AAV vectors. Long-term studies in nonhuman primates (NHPs) provide the most predictive data on expression durability, potential for vector integration, and the long-term safety profile, which are necessary for calculating clinical risk.

What is the typical timeline for an IND-enabling toxicology study that includes long-term expression analysis?

While each program is unique, our scientific leadership and core operational teams have a track record of moving candidates to IND within an 18-24 month timeline. This history of success, achieved prior to our formal launch as Franklin Biolabs in 2024, is built on efficient study design that integrates long-term durability endpoints into the overall preclinical toxicology program.

How does Franklin Biolabs support extended NHP studies?

Franklin Biolabs has the established infrastructure and deep operational experience required to conduct long-term studies in nonhuman primate models. Our facilities, which include over 100,000 sq ft of animal housing, and our expert veterinary staff are equipped to manage extended in-life phases, ensuring animal welfare and data integrity throughout the duration of the program.

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Executive Summary

For AAV-based next-generation therapies, demonstrating long-term durability of expression is a core regulatory expectation. Preclinical programs must be designed to characterize both initial efficacy and the persistence of the therapeutic effect. This requires sophisticated in vivo studies in nonhuman primate models that can accurately profile the transition from initial, high-level episomal expression to stable, long-term expression potentially driven by vector genome integration. Franklin Biolabs designs and executes these IND-enabling studies to generate the definitive durability data required for global regulatory submissions.

Characterizing the Biphasic Expression of AAV Vectors

A standard preclinical template does not exist for AAV gene therapies. A data-driven strategy must account for the vector’s biological activity over an extended period. AAV-mediated transgene expression in primates often follows a biphasic pattern.

  • Initial Phase: Following administration, high levels of transgene expression are typically driven by non-integrated, episomal AAV constructs. This phase is informative for initial pharmacology and dose-response assessments.

  • Stable Phase: Over time, expression levels may stabilize at a lower, persistent level. Research from our scientific leadership (PMID: 37932420) indicates that integration of the vector’s genetic material can contribute to this long-term, stable expression in primate liver models.

Understanding this transition is fundamental to building a complete safety and efficacy profile. Our study designs incorporate multiple time points for sample collection (serum, plasma, and tissues) to map this expression curve and its underlying molecular basis.

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Study Design for Durability Assessment

A successful long-term durability study is built upon a structured design incorporating multiple endpoints. The study protocol must be designed to quantify expression and assess physiological impact through the systematic collection and analysis of biological samples.

  • Vector Biodistribution: We assess non-target tissue biodistribution to confirm the vector’s activity is localized to the intended tissues.

  • Transgene Expression: Biological samples are collected at multiple time points throughout the study to enable the measurement of protein or RNA levels, mapping the expression curve over time.

  • Histology: Microscopic tissue analysis provides direct evidence of transgene activity and evaluates any associated cellular changes.

This approach generates a comprehensive data package that addresses regulatory questions about long-term biological activity. The feasibility of achieving sustained, multi-year expression in primates has been demonstrated, with studies showing pharmacologically regulated expression for over six years from a single AAV administration (PMID: 15507527). This underscores the value of NHP models in predicting clinical outcomes.

Our preclinical programs are designed to meet harmonized international guidelines (ICH), supporting multi-jurisdictional IND and IMPD submissions. The infrastructure required to execute these complex programs is detailed in our overview of the preclinical value chain.

These specialized assessments are a core component of our work in Preclinical and Translational Services.

Visualizing AAV Expression Dynamics

The following diagram illustrates the two primary mechanisms contributing to AAV transgene expression over time in primate models. Understanding both phases is necessary for a complete assessment of long-term durability and safety.

Scientific Process Diagram

This content is for informational purposes. For guidance specific to your therapeutic program, please contact our team for a consultation.

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