Immune-checkpoint inhibitors have shown modest efficacy against immunologically ‘cold’ tumours. Interleukin-12 (IL-12)—a cytokine that promotes the recruitment of immune cells into tumours as well as immune cell activation, also in cold tumours—can cause severe immune-related adverse events in patients. Here, by exploiting the preferential overexpression of proteases in tumours, we show that fusing a domain of the IL-12 receptor to IL-12 via a linker cleavable by tumour-associated proteases largely restricts the pro-inflammatory effects of IL-12 to tumour sites. In mouse models of subcutaneous adenocarcinoma and orthotopic melanoma, masked IL-12 delivered intravenously did not cause systemic IL-12 signalling and eliminated systemic immune-related adverse events, led to potent therapeutic effects via the remodelling of the immune-suppressive microenvironment, and rendered cold tumours responsive to immune-checkpoint inhibition. We also show that masked IL-12 is activated in tumour lysates from patients. Protease-sensitive masking of potent yet toxic cytokines may facilitate their clinical translation.

免疫检查点抑制剂对免疫“冷”肿瘤显示出适度的功效。白细胞介素-12 (IL-12) 是一种细胞因子，可促进免疫细胞募集至肿瘤以及免疫细胞激活，在冷肿瘤中也是如此，可导致患者出现严重的免疫相关不良事件。在这里，通过利用肿瘤中蛋白酶的优先过度表达，我们发现通过肿瘤相关蛋白酶可裂解的连接子将IL-12受体的结构域与IL-12融合在很大程度上限制了IL-12对肿瘤的促炎作用网站。在皮下腺癌和原位黑色素瘤小鼠模型中，静脉注射掩蔽IL-12不会引起全身性IL-12信号传导，并消除了全身性免疫相关不良事件，通过重塑免疫抑制微环境产生有效的治疗效果，并呈现冷肿瘤对免疫检查点抑制有反应。我们还表明，掩蔽的 IL-12 在患者的肿瘤裂解物中被激活。蛋白酶敏感的强效但有毒的细胞因子掩蔽可能有助于其临床转化。