Reshape the Fates of Treg and CD8+T Cells Through IL-2Rα by Synergizing Divergent Receptor-Biased IL-2 PEGylates

Clinical trials of receptor-biased interleukin-2 (IL-2) variants in cancer therapy show limited efficacy. To investigate, we re-evaluated divergent receptor-biased IL-2 PEGylates (generated via site-specific PEGylation at residues D20 (not-β) and Y45 (not-α)), alone or in combination. Results showed the not-α variant (Y45) activates regulatory T cells (Tregs) via βγ chain binding, overriding CD8+ T cells and impairing efficacy. Conversely, the not-β IL-2 (D20) is inert alone but spatially blocks Y45's βγ engagement, suppressing Treg activation. D20 also modulates activated CD8+ T cells by preferentially binding the α chain, disrupting Y45-mediated βγ signaling to prevent exhaustion and terminal differentiation. Synergy between these PEGylates highlights the α chain as a regulatory switch reshaping Treg, CD8+ T cell, and endothelial cell fates. In syngeneic tumor models, combined therapy enhanced CD8+ T cell infiltration, suppressed tumor growth, and reduced vascular leak syndrome risk. These findings propose combinatorial IL-2 strategies targeting α chain regulation to optimize antitumor responses.