Proven Intelligence Accelerating Next-Generation Therapies.

Executive Summary

Achieving high volumetric productivity for Adeno-Associated Virus (AAV) vectors in suspension culture is a function of multi-parameter optimization. This requires a systematic approach that addresses cell line stability, media and feed strategies, transfection efficiency, and bioreactor control. A data-driven upstream process, developed within a GxP framework, is foundational to generating sufficient, high-quality material for IND-enabling toxicology studies and subsequent clinical phases. Franklin Biolabs leverages a >100,000 sq ft facility to execute these programs, consistently moving candidates toward IND within an 18-24 month timeline.

Optimizing the Cellular Environment for AAV Production

The foundation of any scalable AAV manufacturing process is a robust and well-characterized producer cell line. Stability and growth kinetics of the host cell line, typically HEK293 or a derivative, must be rigorously defined. The process begins with adapting the selected clone to the target suspension media, ensuring consistent performance at increasing scales.

Systematic evaluation of media formulation and feed strategies is then performed. This process optimizes nutrient concentrations and defines a feeding schedule that sustains high-density cell culture without inducing metabolic stress. This phase establishes the conditions necessary for the cells to reach the optimal density and physiological state for efficient transfection.

Fine-Tuning Transfection and Plasmid Stoichiometry

Transient transfection remains a common method for AAV production. The efficiency of this step is a significant determinant of final vector yield. Key parameters that require empirical optimization include:

• Plasmid Quality: High-purity, supercoiled plasmid DNA is required for consistent results.

• DNA-to-Reagent Ratio: The complexation of plasmid DNA with the transfection reagent must be optimized to facilitate cellular uptake without inducing cytotoxicity.

• Plasmid Stoichiometry: The molar ratios of the three plasmids (Rep/Cap, transgene/ITR, and adenoviral helper) are adjusted to maximize capsid assembly and genome packaging.

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 provides the essential development and manufacturing for our AAV-vector based gene therapy candidate, and we hope to continue the collaboration for years to come.

Bioreactor Control and Payload Considerations

Translating optimized parameters from shake flasks to controlled single-use bioreactors is the final stage of upstream development. Maintaining precise control over pH, dissolved oxygen (DO), and temperature is necessary for reproducible outcomes. The agitation strategy must also be defined to ensure homogenous mixing without subjecting the cells to excessive shear stress.

Upstream considerations also extend to the therapeutic payload itself. Insights from preclinical safety assessments can inform vector design to mitigate biological risks. For instance, data from nonhuman primate models has shown that incorporating specific microRNA binding sites into the transgene expression cassette can de-target expression from certain tissues, reducing potential toxicity without compromising efficacy in the target organ (PMID: 33177182). This demonstrates how upstream process development and vector design are interlinked components of a comprehensive manufacturing and safety strategy.