Effective pharmacodynamic (PD) assessment is central to de-risking AAV gene therapy programs for Hemophilia A. The primary objective is to establish a clear relationship between AAV8 vector dose, human Factor VIII (hFVIII) transgene expression, and durable phenotypic correction. Franklin Biolabs designs and executes IND-enabling pharmacology studies that quantify therapeutic efficacy and inform clinical dose selection. Our programs are structured to deliver a comprehensive data package supporting an 18-24 month IND timeline.

Defining Efficacy for AAV-Mediated Factor VIII Replacement

The central challenge in developing AAV-based therapies for Hemophilia A is achieving stable and therapeutic levels of FVIII expression from a liver-directed vector. A robust preclinical pharmacodynamic program must precisely quantify the dose-dependent restoration of coagulation function and establish the durability of the therapeutic effect.

These studies provide the quantitative evidence needed to build confidence in a therapeutic candidate’s mechanism of action before advancing to pivotal GxP toxicology studies. The data directly inform the design of first-in-human clinical trials.

Key Parameters in AAV8 Pharmacodynamic Modeling

Our efficacy studies for AAV8-hFVIII constructs are designed to evaluate multiple integrated endpoints. This approach provides a holistic view of the biological activity and therapeutic potential.

• Transgene Expression and Activity: We quantify circulating hFVIII antigen levels via ELISA and measure functional activity using chromogenic or one-stage clotting assays.

• Coagulation Cascade Correction: The functional impact on the coagulation cascade is confirmed using standard clinical assays, primarily the activated partial thromboplastin time (aPTT).

• Phenotypic Rescue: Efficacy is confirmed by assessing the correction of the bleeding diathesis using validated in vivo challenge models.

• Vector Biodistribution: At study termination, quantitative PCR is used to determine vector genome copy numbers in the target organ (liver) and to assess non-target tissue biodistribution.

Vector Engineering and Long-Term Expression

Translational success depends heavily on optimizing the AAV vector construct. Scientific literature reinforces that capsid serotype and the design of the expression cassette are primary drivers of therapeutic protein expression and persistence.

One key study demonstrated that liver-directed gene therapy using an optimized AAV serotype could mediate sustained correction of a bleeding disorder, even in subjects with pre-existing antibodies to a different serotype (PMID: 15637142). This highlights the importance of serotype selection in product design. Further research has shown that systematically evaluating different promoter and enhancer combinations is a powerful strategy for maximizing transgene expression from the target tissue (PMID: 28056565).

“We started collaborating with UPenn Vector core in 2023 and the AAV vector which they manufactured laid a foundation for development of a gene therapy candidate which will enter soon preclinical studies. The key people from UPenn Vector Core joined Franklin Biolabs and our partnership transitioned without interruption from UPenn Vecor Core to Franklin Biolabs Research Vector Division. Franklin Biolabs is our trusted partner in our AAV-vector based gene therapy candidate development and we hope to continue the partnership for years to come.”
— Biotech Partner

Our >100,000 sq ft preclinical facility is fully equipped to conduct these complex in vivo studies.

])

Commitment to Animal Welfare and the 3Rs

All in vivo studies at Franklin Biolabs are conducted in strict compliance with USDA regulations in our AAALAC-accredited facilities. We are committed to the principles of the 3Rs: Replacement, Reduction, and Refinement, ensuring the highest standards of ethical and humane animal care in our research programs.