Abstract 5080: TU2218, a novel ALK5/VEGFR2 dual inhibitor, overcomes tumor endothelial cell anergy and enhances anti-PD1 immunotherapy efficacy
Authors: Lee Jihyun , Kim Nam-hoon , Kim Hun-Taek 
Published: April 2023

Abstract
Immune tolerance by TGF-β and VEGF is inextricably related with poor outcomes of approved anti-PD-(L)1 therapy. Accordingly, a dual target for ALK5 and VEGFR2 via single or combination treatments can be an unequivocal tactic to tune tumor-microenvironment (TME) favorable to ICI, and to essentially overcome immune evasion against TGF-β- and VEGF-enriched tumors. Specifically, several reports from clinical data suggest that VEGF-induced endothelial cell anergy (ECA) acts as a vascular immune checkpoint in TME immune response, and the activation of ECA is associated with worse outcomes. Herein, we demonstrate that TU2218, a first-in-class, orally available inhibitor against ALK5 and VEGFR2 can recover the downregulated endothelial adhesion molecules, i.e., ICAM-1 and VCAM-1, and suppress ECA. In this work, TU2218 completely recovered the expression of ICAM-1 and VCAM-1 on VEGF-induced ECA in HUVECs. The restored level of ICAM-1 and VCAM-1 at 1 μM TU2218 was equivalent to the activity of combined treatment of 1 μM Vactosertib (ALK5 inhibitor) and 25 μg/ml Ramucirumab (VEGFR2 inhibitor). 1 μM of Vactosertib alone, however, did not show such restoration. These results indicate that VEGF-induced ECA is mediated by both VEGFR2 and TGF-β signal, thereby validating the superiority of dual target strategy for ALK5 and VEGFR2 over a single target in overcoming ECA. We further tested if TU2218 could restore VEGF-induced decrease of Jurkat adhesion to HUVECs, considering the close relationship between the expression of adhesion-molecules of endothelial cell surface and the adhesion of lymphocytes to endothelium. TU2218 recovered the number of Jurkat adhering to VEGF-elicited HUVEC monolayer in a dose-dependent manner, but Vactosertib did not. Furthermore, the activity of TU2218 on Jurkat adhesion was reversed by VCAM-1 neutralizing antibody. Therefore, our results demonstrate that TU2218 improves Jurkat adhesion by restoring VCAM-1 expression. Finally, the in vivo translatability of TU2218 in overcoming ECA was confirmed with B16F10-bearing mice, a well-defined immune desert model, after treatments of anti-PD1 antibody, TU2218, or combined regimen for 15 days. TU2218 combined with an anti-PD1 antibody significantly suppressed tumor growth by c.a. 74 % compared to vehicle, thus being superior to a single treatment (e.g., tumor growth inhibition (TGI) 44% for TU2218, TGI 45% for anti-PD1). In this combination, TU2218 increased the number of both CD31+VCAM-1+ and IFNγ+CD8+ T cells in the tumor. We conclude that TU2218 leads not only to the enhancement of T cell-traffic toward TME, but also to the conversion of immune balance favorable to anti-PD1 therapy. The Phase 1b trial of TU2218 combined with pembrolizumab is underway for advanced solid cancers (NCT05204862).
Citation Format: Jihyun Lee, Nam-hoon Kim, Hun-Taek Kim. TU2218, a novel ALK5/VEGFR2 dual inhibitor, overcomes tumor endothelial cell anergy and enhances anti-PD1 immunotherapy efficacy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5080.