PRGN-2009 and bintrafusp alfa for patients with advanced or metastatic human papillomavirus-associated cancer.

Background: This first-in-human phase 1 study (NCT04432597) evaluated the safety and recommended phase 2 dose (RP2D) of PRGN-2009, a gorilla adenoviral-vector targeting oncoproteins E6, E7 (human papillomavirus (HPV)16/18) and E5 (HPV16), as monotherapy (Arm 1A) and combined with the bifunctional TGF-β "trap"/anti-PD-L1 fusion protein bintrafusp alfa (BA; Arm 1B), in patients with recurrent/metastatic HPV-associated cancer.

Methods: Patients with ≥ 1 prior treatment (immunotherapy allowed) received PRGN-2009 (1 × 10¹¹ particle units or 5 × 10¹¹ particle units, subcutaneously) every 2 weeks for 3 doses, then every 4 weeks (Arm 1A), or PRGN-2009 (RP2D, schedule per Arm 1A) and BA (1200 mg, intravenously) every 2 weeks (Arm 1B). Primary endpoints were safety and RP2D of PRGN-2009; secondary objectives included overall response rate (ORR) and overall survival (OS).

Results: Seventeen patients were treated. In Arm 1A (n = 6) there were no dose limiting toxicities or grade 3/4 treatment-related adverse events (TRAEs), 5 × 10¹¹ PU was selected as RP2D, no responses were observed, and median OS (mOS) was 7.4 months (95% CI 2.9-26.8). In Arm 1B (n = 11), grade 3/4 TRAEs occurred in 27% of patients, ORR was 20% for all patients (22% in checkpoint-resistant patients), and mOS was 24.6 months (95% CI 9.6-not reached). Multifunctional HPV-specific T cells were increased or induced de novo in 80% of patients and not impacted by anti-vector antibodies. Higher serum IL-8 at baseline associated with shorter OS.

Conclusions: PRGN-2009 was well tolerated, and immune responses were observed to PRGN-2009. Encouraging anti-tumor activity and OS were noted in the combination with BA arm, consisting mainly of checkpoint-resistant patients. Trial Registration ClinicalTrials.gov Identifier: NCT04432597.