Nadofaragene firadenovec (nadofaragene firadenovec-vncg; Adstiladrin ® ) is a non-replicating adenoviral vector-based gene therapy developed by Ferring Pharmaceuticals for the treatment of high-risk Bacillus Calmette-Guérin (BCG)-unresponsive non-muscle invasive bladder cancer (NMIBC). Nadofaragene firadenovec constitutes vector DNA that encodes for interferon (IFN)-α2b and is the first approved gene therapy in bladder cancer. The production of IFN-α2b by transfected urothelial cells is associated with anticancer activity, including immunostimulatory, antiangiogenic and apoptotic effects. In December 2022, nadofaragene firadenovec received its first global approval in the USA for the treatment of high-risk BCG-unresponsive NMIBC with carcinoma in situ (CIS) with or without papillary tumours in adults. This article summarizes the milestones in the development of nadofaragene firadenovec leading to this first approval for this indication.