Abstract 4334: AR170, a novel PD-1xVEGFxIL-2v tri-specific immunocytokine to redefine next generation cancer immunotherapy

Abstract Background: Bispecific antibodies that simultaneously target PD-1 and VEGF have shown promise in extending the efficacy of PD-1 inhibition alone, yet despite improved treatment response and prolonged progression-free survival, overall survival advantage over anti-PD-1 monotherapy is so far limited. Interleukin-2 (IL-2) combination can markedly potentiate the efficacy of PD-1xVEGF bispecific antibodies, but challenges remain due to systemic toxicity. To overcome this limitation, AR170 was designed as a novel tri-specific immunocytokine that simultaneously engages PD-1, VEGF, and the IL-2 receptor by incorporating an optimized cis-acting IL-2 variant (IL-2v) and complete Fc-silencing. Methods: VEGF-induced AR170 dimerization was assessed by SE-HPLC. Enhanced PD-1 binding after dimerization was confirmed using bio-layer interferometry (BLI) and flow cytometry. Blockade of PD-1/PD-L1 and VEGF/VEGFR interactions was validated using a luciferase reporter assay. Functional assays were conducted to measure T cell activation, proliferation, cytotoxicity, and cytokine secretion by flow cytometry or ELISA. Fc-silencing was confirmed by ADCC, ADCP, and CDC assays. Antitumor efficacy was evaluated in both hPBMC-engrafted and hPD-1/hPD-L1/hVEGF triple knocked-in mouse models. Safety and pharmacokinetic studies were carried out in hIL-2R knock-in mice and cynomolgus monkeys. Results: AR170 undergoes VEGF-induced dimerization that synergizes blockade activity of both PD-1 and VEGF. AR170 delivers PD-1-dependent cis-acting IL-2v signaling. In addition, Fc-silencing technology effectively minimizes Fc-mediated effector function. AR170 under VEGF-enriched exhaustion conditions induced robust proliferation and activation of CD8+ T cells compared to either PD-1 inhibitor or PD-1xVEGF bispecific antibody in vitro. AR170 elicited rapid and durable antitumor responses superior to either PD-1 inhibitor or PD-1xVEGF bispecific antibody in VEGF-expressing tumor-bearing (≥300 mm3) humanized mouse models, while depletion of CD8+ T cells eliminated antitumor efficacy. Immune cell profiling showed elevated proportion of TCF1+PD-1+CD8+ T cells following AR170 treatment. AR170 demonstrated favorable safety and pharmacokinetic profiles in both mice and cynomolgus monkeys. Conclusions: AR170 is a next-generation cancer immunotherapy that uses a novel IL-2v fusion approach to surpass the efficacy limitations of PD-1xVEGF bispecific antibodies. Citation Format: Seon-Mi Yu, Jaeho Song, Juhan Yoon, Bum-Chan Park, Wooick Jang, Young woo Park, Chonghun Rhee, Jihye Yoon, Da-Mi Kim, Wanki Park, Yeung-chul Kim. AR170, a novel PD-1xVEGFxIL-2v tri-specific immunocytokine to redefine next generation cancer immunotherapy abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4334.