A Tumor-Microenvironment-Responsive Chemically Masked IL-2 Prodrug Potentiates PD-1 Checkpoint Blockade and Elicits Robust Antitumor Efficacy
Linzhi Tan, Yunwen Yang, Kerui Zhao, Jingjing Zhou, Xin Wang, Xingyu Zhao, Qiang Lu, Junyu Lin, Yijie Zhao, Yushun Tian, Yong Wang, Chao Zhong, Tao LiuAbstract
Interleukin-2 (IL-2) is a potent mediator of T-cell activation with significant potential for cancer immunotherapy, yet its clinical utility is severely constrained by its narrow therapeutic window. Here we report a chemically masked IL-2 prodrug (Cm-proIL2) that enables tumor-microenvironment-responsive cytokine activation through tumor-associated protease cleavage. Site-specific conjugation of a poly(ethylene glycol) (PEG) moiety selectively masks peripheral receptor engagement, while PEG removal within the tumor microenvironment restores IL-2 receptor binding and reduces molecular size, thereby enhancing intratumoral lymphocyte penetration and effector T cell functionality. Building on this modular platform, we further engineered a PD-1-targeted nanobody fusion, PD1-Cm-proIL2, to enable the cis delivery of IL-2 activity to PD-1+ tumor-infiltrating T cells. PD1-Cm-proIL2 induces robust antitumor immunity, resulting in complete tumor regression and durable protection upon tumor rechallenge in a murine colorectal cancer model. Together, these findings demonstrate the feasibility of chemically masked, tumor-responsive cytokine activation as a strategy for improving the therapeutic index of IL-2-based immunotherapies.