Abstract 2361: A PD1-antibody-attenuated IL-2 fusion protein activates immune cells leading to the inhibition of tumor growth in ex vivo human 3D tumor models

Abstract IL-2 has been prescribed to effectively treat malignancies, mainly melanoma, for decades. Its use has waned in recent years due to significant toxicity and a narrow therapeutic index. To overcome the limitations of systemic administration of IL-2, we have generated a modified IL-2 (IL2Att) with specific substitutions to reduce the binding affinity with the IL-2R. The attenuated cytokine was fused to a high-affinity anti-PD1 antibody that does not block PD-1 binding with its ligands (PD-L1 and PD-L2). The resulting antibody-cytokine fusion, anti-PD1-IL2Att, allows selective delivery of IL-2 to tumor-reactive PD1+ T cells, with limited potential to activate PD1− cells. To evaluate the effect of anti-PD1-IL2Att in a human tumor microenvironment (TME), we established a unique human 3D multi-cellular cancer system. This model system includes neoplastic and somatic cells that make up the TME, further supplemented with peripheral blood mononuclear cells (PBMC). We found that the anti-PD1-IL2Att reduced tumor cell survival more effectively in several types of these 3D cancer models (melanoma, glioblastoma, ovarian and colon cancer) than standard immune checkpoint inhibitors pembrolizumab or nivolumab. Combination treatments of anti-PD1-IL2Att with either of these agents resulted in improved immune activation and tumor cell killing. Our findings suggest that tumor-targeted attenuated cytokines such as IL-2 can promote robust tumor killing while minimizing systemic toxicity. Citation Format: Ronit Satchi-Fainaro, Opal Avramoff, Anshika Katyal, Eilam Yeini, Anne Krinsky, Yulia Liubomirski, Shai Dulberg, Galia Tiram, Ayelet Kaminitz, Jason Gill, Jessica Pedersen, Dana Bar-On, Ayala Tamir, Paul Ayton, Tetsuya Taura, David Wilson, Asaf Madi. A PD1-antibody-attenuated IL-2 fusion protein activates immune cells leading to the inhibition of tumor growth in ex vivo human 3D tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2361.