Abstract LB029: AWT030: a first-in-class bi-functional IL-21 fusion protein selectively activates tumor infiltrated CD8 T cells and suppresses Treg cells

Abstract The tumor microenvironment (TME) has been identified as a significant obstacle to the success of immunotherapy, including anti-PD-1 therapy. The TME comprises several factors that limit the response rate to immunotherapy, including immunosuppressive cells such as regulatory T cells (Tregs), which directly or indirectly interact with effector cells and undermine the tumor recognition, activation, proliferation, and survival of the effector cells, thereby promoting tumor growth. To overcome suppressive TME, we designed AWT030, a first-in-class bi-functional IL-21 fusion protein that comprises a stability and potency optimized IL-21 mutein and an engineered functional domain that targets T cells. AWT030 is designed to selectively activate tumor-infiltrating CD8 T cells and suppress Tregs while avoiding the potential suppressive effect of IL-21 on dendritic cells.Compared to wild-type IL-21, mAWT030 greatly enhances the tolerability, half-life, and anti-tumor activity. In anti-PD-1 therapy resistant breast cancer EMT6 model, fibrosarcoma MCA205 model, and anti-PD-1 therapy responsive colon cancer MC38 model, mAWT030 achieved 100% complete response without noticeable toxicity, demonstrating a powerful synergy between tumor specific CD8 T cell activation axis and Treg suppression axis induced simultaneously by mAWT030. In addition, mAWT030 also exhibited a strong synergistic effect with anti-PD-1 antibody. Immunophenotyping revealed that AWT030 had minimal impact on circulating lymphocytes while altering the suppressive TME, with a significantly increased CD8 T cell population and suppressed Treg population. In summary, AWT030 is a novel bi-functional IL-21 fusion protein with high tumoral specificity, the excellent safety and antitumor activity of mAWT030 observed preclinically supports clinical development, focusing on treating PD-1 resistant/relapsed patients or combining with anti-PD-1 therapy. Citation Format: Fan Ye, Jianing Huang, Sandra Chen, Ella Li, Jenny Jiang, Hanna Lin, Michael Hua, Danny Huang, Zoey Huang, Joyce Kwan, Lili Cheng, Ziyang Zhong. AWT030: a first-in-class bi-functional IL-21 fusion protein selectively activates tumor infiltrated CD8 T cells and suppresses Treg cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB029.