PRGN-2012, a novel gorilla adenovirus-based immunotherapy, provides the first treatment that leads to complete and durable responses in recurrent respiratory papillomatosis patients.

LBA6015 Background: Recurrent respiratory papillomatosis (RRP) is a rare, neoplastic disorder caused by chronic infection with human papillomavirus (HPV) type 6 or 11. Significant morbidity can occur due to airway obstruction and, although rare, transformation into malignant cancer. There are no approved therapeutics. RRP is currently managed with frequent ablative procedures that can lead to irreversible laryngotracheal scarring and disability. PRGN-2012 is a gorilla adenovirus-based gene therapy/immunotherapy designed to generate HPV6/11-specific T cell immunity. The FDA has granted PRGN-2012 Breakthrough Therapy Designation for the treatment of RRP recognizing that this single arm study can serve as pivotal to support a licensing application. Methods: This pivotal trial (NCT04724980) evaluates the safety and efficacy of PRGN-2012 in patients with RRP requiring a minimum of 3 surgeries in the 12 months prior to treatment. Eligible patients received 4 subcutaneous (SC) injections of PRGN-2012 at dose level (DL) 1 (1x10 11 Particle Units (PU) per injection; n=3) or DL2 (5x10 11 PU per injection; n=35) over 12 weeks. The primary endpoint was the rate of complete response (CR), defined as no requirement for surgery in the 12 months following completion of treatment. Other key endpoints include duration of response, change in extent of papilloma growth (anatomic Derkay score) and vocal function. Results: PRGN-2012 was well-tolerated, with no serious adverse events, grade > 2 treatment-related adverse events, or early treatment discontinuations. The most common adverse events were injection-site reaction, fatigue, chills, fever, and myalgia. PRGN-2012 treatment at DL2 significantly (p<0.0001) decreased the requirement for surgery, with a median number of surgeries in the 12 month period decreasing from 4 (3-10) prior to treatment to 0 (0-7) surgeries post-treatment. Approximately 90% of patients experienced a decrease in the number of surgeries in the 12 months post-treatment compared to pre-treatment with PRGN-2012. The primary endpoint evaluation demonstrated a confirmed complete response in 17/31 (55%) of evaluable patients. The median duration of complete response has yet to be reached with a median follow up of 15 months (12 - 30) at the time of data cutoff (March 6, 2024). Additionally, PRGN-2012 treatment resulted in a significant reduction in Derkay score, improvement in vocal function and generation of HPV-specific immune responses. Conclusions: These data demonstrate the overall favorable safety profile and significant clinical benefit of PRGN-2012 in adult RRP patients. These findings support PRGN-2012 as a potential therapeutic option for this patient population where no FDA-approved therapeutics exist. Clinical trial information: NCT04724980 .