PD-1-Targeted IL-2v Expands a Novel Stem-like T Cell Subset Distinct from Anti-PD-1 Therapy to Enhance Effector Differentiation

Tumor-draining lymph nodes serve as critical sites for the generation, maintenance and differentiation of stem-like CD8⁺ T cells during antitumor immune responses. Recent evidence has shown that delivering interleukin-2 to PD1⁺ stem-like CD8⁺ T cells using PD1-IL2v, an immunocytokine combining PD-1 blockade and IL-2R agonism, promotes their differentiation into potent effector cells with enhanced tumor-killing capacity. However, it remains unclear how targeted interleukin-2 therapies imprint early stem-like T-cell differentiation programs. Here, using single-cell transcriptomics and T-cell receptor sequencing in murine pancreatic tumor models, we demonstrate that PD1-IL2v induces an early bifurcation in the differentiation of stem-like CD8⁺ T cells within tumor-draining lymph nodes. We identify an effector-primed stem-like population characterized by the expression of interferon-response genes, natural killer cell receptor genes, and Cx3cr1, consistent with activation of interleukin-2 and STAT5-associated programs. Clonal tracking revealed substantial overlap between these lymph node-derived cells and intratumoral effector populations, supporting a developmental relationship between early priming in lymph nodes and downstream effector differentiation. In contrast, an alternative stem-like state that displayed features associated with T-cell exhaustion, including increased Tox expression, was observed upon PD-1 therapy. Together, these findings identify an early branch point in stem-like T-cell differentiation and provide mechanistic insight into how PD1-IL2v circumvents exhaustion pathways to preferentially generate functional antitumor immunity.