Abstract 7286: A first-in-class αPD-1/αVEGF/IL-2v tri-specific fusion protein demonstrates promising anti-tumor efficacy in immune checkpoint inhibitor-resistant tumor models

Abstract Immune checkpoint inhibitors (ICIs), including anti-PD(L)1 monoclonal antibodies, have been widely approved and used for various cancer types. However, the response rate to ICIs is limited to certain cancer types, largely attributed to the absence or low presence of immune cells within the tumor microenvironment (TME). αVEGF antibodies not only facilitate immune cell infiltration into tumors but also improve the immunosuppressive conditions of the TME. Notably, the combination of αPD-1 and αVEGF antibodies and αPD-1/αVEGF bispecific antibody therapy have demonstrated improved efficacy compared to αPD-1 monotherapy across various cancer types. Despite such advances, boosting immune cell proliferation within the TME remains crucial for achieving superior efficacy in ICI-resistant or refractory patients. αPD-1/αVEGF/IL-2v is a highly TME-selective tri-specific fusion protein comprising αPD-1, αVEGF, and IL-2v. This compound was engineered to activate T cells continuously via αPD-1, enhance tumor-infiltrating lymphocytes (TILs) via αVEGF, and proliferate effector T cells strongly via novel IL-2v. We evaluated the intrinsic activity of each functional arm of the αPD-1/αVEGF/IL-2v fusion protein individually. The αPD-1/αVEGF/IL-2v exhibited blocking activity against PD-1/PD-L1 binding comparable to pembrolizumab, showed VEGF/VEGFR blockade activity similar to that of αVEGF antibody, and effectively induced CD8+ T cell activation comparable to aldesleukin. In vitro trans-endothelial migration assay demonstrated that αPD-1/αVEGF/IL-2v significantly enhanced T cell migration compared to the combination of αPD-1 and αVEGF or αPD-1/αVEGF bispecific antibody. This tri-specific fusion protein also improved the CD8+ T cell/Treg ratio and reduced exhausted CD8+ T cell population during in vitro immune cell expansion in TME mimic condition. Furthermore, αPD-1/αVEGF/IL-2v showed TME selective immune cell activation and cytokine release while exhibiting minimal effects on immune cells in peripheral blood. The murine surrogate of αPD-1/αVEGF/IL-2v demonstrated dose-dependent anti-tumor efficacy, superior to αPD-1 or αPD-1/αVEGF bispecific antibody in both ICI-resistant MC38 and B16F10 tumor models without body weight loss. In conclusion, αPD-1/αVEGF/IL-2v represents a first-in-class tri-specific fusion protein with therapeutic potential to overcome the limitations of αPD-1 or αPD-1/αVEGF therapies. Citation Format: Sunjung Cho, Jun-Eui Park, Yongjun Jung, Hyojoo Bang, Jeongseok Heo, Seokchan Kang, Suna Kim, Minwoo Kim, Young Jin Park. A first-in-class αPD-1/αVEGF/IL-2v tri-specific fusion protein demonstrates promising anti-tumor efficacy in immune checkpoint inhibitor-resistant tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7286.