Targeting tumor-specific T cells with LAG3-directed interleukin-2 prevents T-cell exhaustion and reinvigorates antitumor immunity

Signal Transduction and Targeted Therapy ARTICLE www.nature.com/sigtrans OPEN Targeting tumor-specific T cells with LAG3-directed interleukin-2 prevents T-cell exhaustion and reinvigorates antitumor immunity 1234567890();,: Xiaohong Yu1, Huiping Liao1, Jiaoyun Lv1, Yu Sun1, Ruiqi Zhang1, Yiwei Chen1, Yifan Lin1, Lulu Liu1, Shijie Li1,2,3, Hui Tang4, Panpan Jia1,5, Bin Shao5, Zaopeng Yang 1, Yang-Xin Fu 1,2,3 ✉ and Zhenhua Ren1,5 ✉ LAG3 is a critical inhibitory receptor that is highly enriched on exhausted T cells within the tumor microenvironment (TME), where it acts as a key driver of T-cell exhaustion—an archetypal barrier to robust antitumor immunity. In a colon cancer model, LAG3+CD8+ tumorinfiltrating lymphocytes (TILs) constitute the predominant type of tumor-specific T cells but exhibit defective IL2 signaling. To address whether exogenous IL2 replenishment unpins their dysfunction, we engineered LAG3-LaIL2 (low-affinity IL2), a fusion protein that selectively delivers IL2 to LAG3+CD8+ TILs. LAG3-LaIL2 expanded pre-exhausted tumor-specific CD8+ T cells, reprogrammed their exhaustion trajectory toward an intermediate effector state, and prevented terminal exhaustion, leading to tumor regression and prolonged survival in mice. Mechanistically, LAG3-LaIL2 restored IL2R-JAK3-STAT5 signaling by upregulating the high-affinity IL2 receptor subunit CD122, thereby restoring TIL functionality. Furthermore, LAG3-LaIL2 amplified tumor-specific effector and memory T cells in draining lymph nodes, enabling systemic antitumor immunity against distal tumors and preventing tumor recurrence. Collectively, our findings identify LAG3-LaIL2 as a precision immunotherapy that specifically targets exhausted TILs while restricting IL2 exposure to nontarget cells, thereby enhancing both the efficacy and safety of this approach. This approach provides a translatable strategy to overcome T-cell exhaustion in solid tumors and represents a promising avenue to improve clinical outcomes in cancer patients. Signal Transduction and Targeted Therapy (2026)11:207 INTRODUCTION Tumor-reactive CD8+ T cells have the inherent capacity to eradicate cancer cells, as evidenced by the clinical success of immune checkpoint blockade (ICB) therapies targeting pathways such as the PD-1/PD-L1 pathway.1 However, tumors frequently evade immune elimination via compensatory upregulation of alternative inhibitory receptors, including LAG3 and TIM3, which drive T-cell dysfunction and exhaustion.2–4 Lymphocyte activation gene-3 (LAG3; CD223), a coinhibitory receptor enriched in exhausted and dysfunctional tumor-infiltrating CD8+ T cells, synergizes with PD-1 to suppress T-cell receptor (TCR) signaling and cytokine production, thereby establishing a resilient immunosuppressive axis in the TME.3,5–7 Notably, dual anti-PD-1/anti-LAG3 blockade therapy (Opdualag®) was approved by the FDA in 2022 for unresectable or metastatic melanoma, demonstrating that LAG3 inhibition can enhance antitumor immunity when combined with PD-1 blockade.8–10 This regulatory milestone demonstrates the therapeutic potential of cotargeting nonredundant inhibitory pathways, addressing the immune evasion mechanisms that often constrain responses to single-agent checkpoint therapies. While dual PD-1/ LAG3 blockade has shown promise for overcoming resistance to single-agent ICBs, many patients still fail to respond because of ; https://doi.org/10.1038/s41392-026-02667-8 the epigenetic and functional heterogeneity of exhausted T-cell states.11 This highlights the urgent need for novel immunomodulatory strategies to dismantle treatment resistance mechanisms. Exhausted CD8+ T cells within the TME exhibit significant heterogeneity, encompassing early dysfunctional subsets with plastic epigenetic profiles amenable to reprogramming and latestage exhausted populations characterized by stable fixed epigenetic states that confer functional irreversibility.12 A critical subset of “pre-exhausted” LAG3+CD8+ T cells retains partial functionality and reprogramming potential, offering a therapeutic window to restore antitumor immunity. IL2, a potent T-cell growth factor, could theoretically rejuvenate these cells by activating the IL2R-JAK3-STAT5 axis, which is often impaired in exhausted T cells. One promising approach involves stimulating early dysfunctional LAG3+ pre-exhausted T cells with IL2. IL2 exerts its primary biological effects through CD8+ T cells and NK lymphocytes.13 However, the therapeutic application of IL2 is hindered by its short half-life in vivo and its propensity to promote the differentiation trajectory, immunosuppressive potential, and homeostasis of regulatory T cells (Tregs), which directly counteract the cytotoxic antitumor potential of effector T cells.14–16 Furthermore, the substantial doses required for therapeutic efficacy pose a risk of lethal toxicity.13 To address these limitations, strategies that 1 Changping Laboratory, Beijing, China; 2Center for Cancer Biology, School of Basic Medical Sciences, Tsinghua University, Beijing, China; 3State Key Laboratory of Molecular Oncology, Tsinghua University, Beijing, China; 4Department of Medical Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China and 5Department of Lymphoma, Department of Breast Oncology, Key laboratory of Carcinogenesis and Translational Research (Ministry of Education), Peking University Cancer Hospital & Institute, Beijing, China Correspondence: Yang-Xin Fu () or Zhenhua Ren () These authors contributed equally: Xiaohong Yu, Huiping Liao Received: 17 June 2025 Revised: 19 January 2026 Accepted: 3 March 2026 © The Author(s) 2026 Targeting tumor-specific T cells with LAG3-directed interleukin-2. . . Yu et al. 2 selectively deliver IL2 to effector cells within tumor tissues while concomitantly minimizing unintended systemic toxicity are urgently needed. Current therapeutic approaches typically rely on targeting tumor antigens to deliver IL2 to the tumor microenvironment, but these methods risk off-target effects on tumor-specific CD8+ T cells.17–19 To overcome these challenges, we propose two key strategies: targeted delivery of IL2 to LAG3+CD8+ T cells within the TME rather than tumor cell targeting and the use of a low-affinity IL2 variant (LaIL2)20 with reduced binding to both IL2Rα and IL2Rβ to allow better targeting of LAG3+ dysfunctional tumor-infiltrating lymphocytes (TILs), leading to better tumor control. In this study, we designed a T-cell-specific fusion protein (LaIL2 linked to an anti-LAG3 antibody, LAG3-LaIL2) designed to enhance efficacy while minimizing toxicity. Our work establishes LAG3LaIL2 as a precision immunotherapy that synergizes the antitumor potency of IL2 with the spatial specificity of LAG3 targeting, addressing key limitations of current ICB and cytokine-based therapies. These findings emphasize the therapeutic potential of reprogramming pre-exhausted T-cell states to overc (...truncated)