Introduction: Zopapogene imadenovec-drba (zopa), a novel adenoviral vector-based immunotherapy, is the first and only FDA-approved treatment for adults with recurrent respiratory papillomatosis (RRP), a rare disorder caused by chronic human papillomavirus (HPV) type 6 or 11 infection.

Methods: The pivotal trial (NCT04724980) evaluated safety and efficacy in adult patients with RRP treated with 4 subcutaneous injections of zopa over a 12-week interval at the approved dose of 5×10^11 particle units per injection; n=35.

Results: Robust efficacy was observed following treatment, with 51% (34 to 69; 95% CI) of patients achieving a complete response (CR), defined as no requirement for surgical interventions in the 12 months (m) following treatment and 86% of patients experienced a decrease in interventions. Patients are in long-term follow-up and as of the data cut-off (September 19, 2025), 15/18 (83%) patients achieving a CR remain in CR. The median duration of follow-up was 36m (range: 27-37m), with median duration of CR yet to be reached.

No grade >2 treatment-related adverse events (TRAEs), no serious TRAEs, and no early treatment discontinuations were observed. No new safety events were observed during long-term follow-up.

The induction of HPV-specific T-cells at the time of zopa treatment completion was significantly higher in responders compared to non-responders (mean fold-change 165 vs 5, P<0.018).

Conclusions: Zopa treatment demonstrated significant clinical benefit with most of the patients experiencing either ongoing durable complete responses for up to 3 years or sustained reduction in the need for debulking procedures, with excellent long-term safety. Updated data will be presented.