Abstract 7264: AI-guided engineering and preclinical characterization of anti-PD1/IL15 mutein bifunctional fusion proteins

Abstract IL15, a cytokine of the IL2 family, is pivotal for activating natural killer cells and effector/memory CD8 T cells. Clinical application with various IL15 formulations for cancer therapy, however, has been greatly hindered by its pharmacokinetics and dose-dependent systemic toxicity. A promising approach involves the fusion of IL15 with an anti-TAA antibody or an immune checkpoint antibody, in an attempt to specifically target IL15 to the tumor and its microenvironment while reducing peripheral exposure and toxicity. In this study, we generated a panel of stable IL15 variants (IL15v), utilizing an internally developed AI algorithm, with attenuated binding affinity to IL2Rβ and biological activity. We then engineered a panel of fusion proteins each comprising of a disulfide-bond stabilized IL15v, the IL15Ra sushi domain, and an anti-PD1 antibody IgG. Several lead molecules were produced with good expression level, stability and drugability. These anti-PD1/IL15v fusions not only fully retained their PD1-blocking activity, but also were significantly more potent in promoting the activation of PD1-expressing T cells, comparing to those of PD1-negative cells. In vivo pharmacokinetics and antitumor activity of these anti-PD1/IL15v fusions are currently being investigated. Anti-PD1 targeted delivery of stabilized and attenuated IL15v may provide an effective approach, with an improved safety profile, to reverse the suppressive state of tumor-infiltrating antigen-specific PD1-expressing CD8 T cells. Citation Format: Yun Zhang, Liang Tian, Chenpeng Su, Xiangyu Sun, Ran Hao, Tianhong Li, Dandan Liu, Jiyuan Tian, Xiaoqian Chen, Jian Peng, Zhenping Zhu. AI-guided engineering and preclinical characterization of anti-PD1/IL15 mutein bifunctional fusion proteins [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 7264.