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

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

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7 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)250-258
Number of pages9
JournalMolecular therapy. Methods & clinical development
Publication statusPublished - 11 Sept 2020


  • AAV8
  • Crigler-Najjar syndrome
  • UGT1A1 activity
  • adeno-associated virus
  • bilirubin
  • gene therapy
  • potency
  • quantitative potency assay
  • transduction efficiency

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