Laboratory of Tumor Immunology and Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
Altor Bioscience, a NantWorks company, Miramar, FL, USA.
J Immunother Cancer. 2019 Mar 21;7(1):82. doi: 10.1186/s40425-019-0551-y.
Immunotherapy targeting PD-1/PD-L1 fails to induce clinical responses in most patients with solid cancers. N-803, formerly ALT-803, is an IL-15 superagonist mutant and dimeric IL-15RαSushi-Fc fusion protein complex that enhances CD8 T and NK cell expansion and function and exhibits anti-tumor efficacy in preclinical models. Previous in vitro studies have shown that IL-15 increases PD-L1 expression, a negative regulator of CD8 T and NK cell function. Most reported preclinical studies administered N-803 intraperitoneally not subcutaneously, the current clinical route of administration. N-803 is now being evaluated clinically in combination with PD-1/PD-L1 inhibitors. However, the mechanism of action has not been fully elucidated. Here, we examined the anti-tumor efficacy and immunomodulatory effects of combining N-803 with an anti-PD-L1 antibody in preclinical models of solid carcinomas refractory to anti-PD-L1 or N-803.
Subcutaneous N-803 and an anti-PD-L1 monoclonal antibody were administered as monotherapy or in combination to 4T1 triple negative breast and MC38-CEA colon tumor-bearing mice. Anti-tumor efficacy was evaluated, and a comprehensive analysis of the immune-mediated effects of each therapy was performed on the primary tumor, lung as a site of metastasis, and spleen.
We demonstrate that N-803 treatment increased PD-L1 expression on immune cells in vivo, supporting the combination of N-803 and anti-PD-L1. N-803 plus anti-PD-L1 was well-tolerated, reduced 4T1 lung metastasis and MC38-CEA tumor burden, and increased survival as compared to N-803 and anti-PD-L1 monotherapies. Efficacy of the combination therapy was dependent on both CD8 T and NK cells and was associated with increased numbers of these activated immune cells in the lung and spleen. Most alterations to NK and CD8 T cell phenotype and number were driven by N-803. However, the addition of anti-PD-L1 to N-803 significantly enhanced CD8 T cell effector function versus N-803 and anti-PD-L1 monotherapies, as indicated by increased Granzyme B and IFNγ production, at the site of metastasis and in the periphery. Increased CD8 T cell effector function correlated with higher serum IFNγ levels, without related toxicities, and enhanced anti-tumor efficacy of the N-803 plus anti-PD-L1 combination versus either monotherapy.
We provide novel insight into the mechanism of action of N-803 plus anti-PD-L1 combination and offer preclinical proof of concept supporting clinical use of N-803 in combination with checkpoint inhibitors, including for patients non- and/or minimally responsive to either monotherapy.
针对 PD-1/PD-L1 的免疫疗法未能在大多数实体瘤患者中诱导临床反应。N-803（以前称为 ALT-803）是一种 IL-15 超激动剂突变体和二聚体 IL-15RαSushi-Fc 融合蛋白复合物，可增强 CD8 T 和 NK 细胞的扩增和功能，并在临床前模型中表现出抗肿瘤疗效。先前的体外研究表明，IL-15 增加了 PD-L1 的表达，PD-L1 是 CD8 T 和 NK 细胞功能的负调节剂。大多数已报道的临床前研究通过腹腔内给药而不是皮下给药（目前的临床给药途径）给予 N-803。N-803 目前正在与 PD-1/PD-L1 抑制剂联合进行临床评估。然而，其作用机制尚未完全阐明。在这里，我们在对 PD-L1 或 N-803 耐药的实体癌临床前模型中，研究了 N-803 联合抗 PD-L1 抗体的抗肿瘤疗效和免疫调节作用。
皮下给予 N-803 和抗 PD-L1 单克隆抗体作为单药或联合治疗，用于携带 4T1 三阴性乳腺癌和 MC38-CEA 结肠癌的小鼠。评估抗肿瘤疗效，并对每种治疗方法在原发性肿瘤、肺部（转移部位）和脾脏中的免疫介导作用进行全面分析。
我们证明 N-803 治疗可增加体内免疫细胞上的 PD-L1 表达，支持 N-803 和抗 PD-L1 的联合应用。与 N-803 和抗 PD-L1 单药治疗相比，N-803 加抗 PD-L1 治疗耐受性良好，可降低 4T1 肺部转移和 MC38-CEA 肿瘤负担，并延长生存期。联合治疗的疗效依赖于 CD8 T 和 NK 细胞，并且与肺部和脾脏中这些活化免疫细胞数量的增加有关。NK 和 CD8 T 细胞表型和数量的大多数改变主要由 N-803 驱动。然而，与 N-803 和抗 PD-L1 单药治疗相比，抗 PD-L1 与 N-803 联合使用可显著增强 CD8 T 细胞的效应功能，表现在转移部位和外周血中 Granzyme B 和 IFNγ 的产生增加。CD8 T 细胞效应功能的增加与更高的血清 IFNγ 水平相关，没有相关的毒性，并增强了 N-803 加抗 PD-L1 联合治疗与任一单药治疗相比的抗肿瘤疗效。
我们为 N-803 加抗 PD-L1 联合治疗的作用机制提供了新的见解，并提供了支持 N-803 联合检查点抑制剂（包括对任一单药治疗无反应和/或反应不充分的患者）临床应用的临床前概念验证。
