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A Quantitative In Vitro Potency Assay for Adeno-Associated Virus Vectors Encoding for the UGT1A1 Transgene.

Molecular therapy. Methods & clinical development (2020-07-09)
Sem J Aronson, Robert S Bakker, Sascha Moenis, Remco van Dijk, Giulia Bortolussi, Fanny Collaud, Xiaoxia Shi, Suzanne Duijst, Lysbeth Ten Bloemendaal, Giuseppe Ronzitti, Andrés F Muro, Federico Mingozzi, Ulrich Beuers, Piter J Bosma
RESUMEN

Potency assessment of clinical-grade vector lots is crucial to support adeno-associated virus (AAV) vector release and is required for future marketing authorization. We have developed and validated a cell-based, quantitative potency assay that detects both transgenic expression and activity of an AAV8-hUGT1A1 vector, which is currently under clinical evaluation for the treatment of Crigler-Najjar syndrome. Potency of AAV8-hUGT1A1 was evaluated in vitro. After transduction of human hepatoma 7 (Huh7) cells, transgene-positive cells were quantified using flow cytometry and transgenic activity by a bilirubin conjugation assay. The in vitro potency of various AAV8-hUGT1A1 batches was compared with their potency in vivo. After AAV8-hUGT1A1 transduction, quantification of UGT1A1-expressing cells shows a linear dose-response relation (R2 = 0.98) with adequate intra-assay and inter-day reproducibility (coefficient of variation [CV] = 11.0% and 22.6%, respectively). In accordance, bilirubin conjugation shows a linear dose-response relation (R2 = 0.99) with adequate intra- and inter-day reproducibility in the low dose range (CV = 15.7% and 19.7%, respectively). Both in vitro potency assays reliably translate to in vivo efficacy of AAV8-hUGT1A1 vector lots. The described cell-based potency assay for AAV8-hUGT1A1 adequately determines transgenic UGT1A1 expression and activity, which is consistent with in vivo efficacy. This novel approach is suited for the determination of vector lot potency to support clinical-grade vector release.

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Bilirrubina, ≥98% (EmM/453 = 60), powder