Precigen (PGEN) Study Result summary

Study background and design

• PRGN-2012 is a gene therapy using a gorilla adenoviral vector targeting HPV 6 and 11 for recurrent respiratory papillomatosis (RRP).

• The pivotal Phase 1/2 study enrolled adults with RRP needing at least 3 interventions or surgeries in the prior year, using a 4-dose regimen over 12 weeks.

• 38 patients enrolled; 35 received the recommended Phase 2 dose, with a median age of 49 and median disease duration of 20 years.

• Each patient served as their own control, comparing interventions required before and after treatment.

• The trial population is representative of typical adult RRP patients, with a mean of 4.5 surgeries in the year prior to enrollment.

Efficacy and safety results

• 51% (18/35) achieved complete response, defined as no surgeries needed in the 12 months post-treatment, with durable responses beyond 12 months (median follow-up 20 months).

• 86% (30/35) had a reduction in surgical interventions, with median surgeries dropping from 4 pre-treatment to 0 post-treatment (p<0.0001).

• Significant improvements in Derkay scores (mean reduced from 9 to 1) and quality of life (VHI-10 mean reduced from 25 to 7) in complete responders.

• The safety profile was favorable, with only mild (grade 1-2) adverse events, no grade 3/4 events, and no dose-limiting toxicities.

• Most common adverse events were mild injection site reactions, fatigue, chills, and fever; no serious treatment-related events reported.

Mechanism and platform advantages

• The gorilla adenoviral vector allows for large genetic payloads and minimal pre-existing immunity, enabling repeat dosing.

• The platform demonstrated strong HPV 6/11-specific T cell responses, with greater expansion in responders, and can be administered subcutaneously.

• No meaningful anti-drug antibody response observed with repeat dosing.

• Manufacturing processes are established to support commercial scale, with capacity for thousands of patients.

• The platform's differentiation supports potential expansion to other HPV-related diseases.