IL-15 is a promising cytokine to expand NK and CD8⁺ T cells for cancer immunotherapy, but its application is limited by dose-limiting, on-target off-tumor toxicity. Here, we have developed a next-generation IL-15 that is activated inside the tumor microenvironment (TME). This pro-IL-15 has the extracellular domain of IL-15Rβ fused to the N-terminus of sIL-15-Fc through a tumor-enriched Matrix Metalloproteinase (MMP) cleavable peptide linker to block its activity. Unlike sIL-15-Fc, pro-IL-15 does not activate the peripheral expansion of NK cells and T cells, thus reducing systemic toxicity, but it still preserves efficient anti-tumor abilities. In various mouse tumors, the anti-tumor effect of pro-IL-15 depends on intratumoral CD8⁺ T cells and IFN-γ. Pro-IL-15 increases the stem-like TCF1⁺Tim-3⁻CD8⁺ T cells within tumor tissue and helps overcome immune checkpoint blockade (ICB) resistance. Moreover, pro-IL-15 synergizes with current tyrosine kinase inhibitor (TKI) targeted-therapy in a poorly inflamed TUBO tumor model, suggesting that pro-IL-15 helps overcome targeted-therapy resistance. Our results demonstrate a next-generation IL-15 cytokine that can stimulate potent anti-tumor activity without severe toxicity.

IL-15 是一种很有前途的细胞因子，可用于扩增 NK 和 CD8 ⁺  T 细胞用于癌症免疫治疗，但其应用受到剂量限制、靶向脱瘤毒性的限制。在这里，我们开发了在肿瘤微环境 (TME) 内激活的下一代 IL-15。这种 pro-IL-15 具有 IL-15Rβ 的细胞外结构域，通过富含肿瘤的基质金属蛋白酶 (MMP) 可切割肽接头与 sIL-15-Fc 的 N 端融合，以阻断其活性。与 sIL-15-Fc 不同，pro-IL-15 不会激活 NK 细胞和 T 细胞的外周扩张，从而降低全身毒性，但仍保留有效的抗肿瘤能力。在各种小鼠肿瘤中，pro-IL-15 的抗肿瘤作用取决于瘤内 CD8 ⁺ T 细胞和 IFN-γ。Pro-IL-15 增加肿瘤组织内的干细胞样 TCF1 ⁺ Tim-3 ^- CD8 ⁺  T 细胞，并有助于克服免疫检查点阻断 (ICB) 抗性。此外，在炎症不良的 TUBO 肿瘤模型中，pro-IL-15 与当前的酪氨酸激酶抑制剂 (TKI) 靶向治疗具有协同作用，这表明 pro-IL-15 有助于克服靶向治疗耐药性。我们的研究结果表明，下一代 IL-15 细胞因子可以刺激有效的抗肿瘤活性而没有严重的毒性。