Proven Intelligence Accelerating Next-Generation Therapies.

Executive Summary

A robust, validated cell-based neutralizing antibody (NAb) assay is a required component of the immunogenicity assessment for most viral vector-based gene therapy programs. These assays quantify the functional ability of antibodies in patient serum to inhibit vector transduction, providing data that directly informs patient selection, dose-response modeling, and overall risk assessment. Franklin Biolabs develops and validates phase-appropriate NAb assays for AAV, lentiviral, and adenoviral vectors under GxP conditions, supporting programs from preclinical characterization through pivotal clinical trials.

The Challenge of Vector Immunogenicity

The efficacy of a viral vector gene therapy can be significantly impacted by the host immune system. Pre-existing antibodies to vectors like Adeno-Associated Virus (AAV), often resulting from natural exposure, can neutralize the therapeutic vector upon administration. Quantifying this neutralizing antibody response is a standard regulatory expectation for clinical development.

An effective immunogenicity strategy hinges on a well-characterized, functional assay. The data informs patient inclusion/exclusion criteria and helps interpret clinical outcomes. For instance, clinical investigations have shown that sustained transgene expression is possible even when T-cell responses develop, underscoring the need to specifically measure the functional impact of humoral immunity (PMID: 19706466). A precisely calibrated NAb assay provides this functional data.

Developing a Robust Cell-Based NAb Assay

Our scientific team, operating within a >100,000 sq ft facility, designs NAb assays tailored to your specific vector and program needs. The process is built on a foundation of scientific rigor to ensure reproducibility and accuracy.

• Vector & Cell Line Selection: The assay uses a reporter construct (e.g., luciferase, GFP) packaged in your specific clinical vector capsid (AAV2, AAV5, AAV8, etc.). We select or engineer a target cell line that is highly permissive to transduction by your vector.

• Assay Optimization: We systematically optimize key parameters, including cell density, vector concentration (multiplicity of infection), and serum incubation times to establish a sensitive and reproducible assay window.

• Cut Point Determination: Statistical analysis of serum from a large, healthy donor population is performed to establish a statistically valid screening cut point, which differentiates negative samples from potentially positive samples.

Phase-Appropriate Validation and Regulatory Alignment

A NAb assay intended for clinical trial support must be validated according to GxP guidelines. Our validation protocols are designed to meet FDA and EMA expectations, assessing parameters such as precision, accuracy, specificity, and robustness. This rigorous approach provides confidence in the data used for clinical decision-making.

This level of detail is necessary for programs targeting indications where achieving high and well-tolerated vector delivery and expression are primary objectives (PMID: 32937039). Our approach to building a solid analytical foundation contributes to a projected 18-24 month timeline to get candidates to IND. This methodology has supported a 100% successful IND submission rate for programs initiated since 2019, with the Franklin Biolabs brand itself launching in 2024.

Beyond AAV: Assays for Lentiviral and Adenoviral Vectors

While AAVs are a common focus, our expertise extends to other clinically relevant viral vectors. We apply the same scientific principles to develop and validate custom NAb assays for lentiviral (LV) and adenoviral (AdV) platforms, adapting the assay design to the unique biology of each vector system. This capability ensures comprehensive immunogenicity support across a diverse range of gene therapy approaches.

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