Precigen (PGEN) Study Result summary

Study background and design

• PRGN-2012, a gene therapy using a gorilla adenoviral vector, targets recurrent respiratory papillomatosis (RRP), a disease with no effective non-surgical treatments.

• The pivotal Phase 1/2 study enrolled adults with RRP who had at least three interventions or surgeries in the prior year, using a 4-dose regimen over 12 weeks, with each patient serving as their own control.

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

• The primary endpoint was the rate of complete response, defined as no clinically indicated procedures required in the year after treatment.

Efficacy 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 (p<0.0001).

Safety and tolerability

• PRGN-2012 was well-tolerated with no dose-limiting toxicities or treatment-related adverse events above Grade 2.

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

• The therapy showed a strong safety profile, with only mild, self-limiting side effects and no grade 3 or 4 adverse events.

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