QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia.
School of Medicine, University of Queensland, Herston, Queensland, Australia.
J Immunother Cancer. 2020 Nov;8(2). doi: 10.1136/jitc-2020-001687.
Concomitant tumor necrosis factor (TNF) neutralization in combination with immune checkpoint inhibitors (ICIs) reduces clinical immune-related adverse events (irAEs) and appears to improve antitumor efficacy in preclinical tumor models. Agonistic antibodies targeting costimulatory receptors such as CD40 represent an additional strategy to boost antitumor immune response and potentiate the activity of ICIs. However, the dose-limiting toxicities observed in anti-CD40-treated cancer patients have hindered its clinical development.
We previously described a mouse model to assess both antitumor activity and irAEs induced by various effective combination immunotherapies. Using the BALB/c and C57BL/6 strains of FoxP3-GFP-DTR (FoxP3) mice, transient depletion of T regulatory cells (Tregs) prior to immunotherapy with additional immunomodulatory antibodies, lowered immune self-tolerance, resulting in the development of a spectrum of physical and biochemical irAEs similar to that reported clinically. In MC38 and 4T1.2 tumor models, following transient Treg depletion, we evaluated the impact of anti-CD40 on antitumor efficacy and the development of irAEs and the impact of concomitant or delayed TNF blockade on both these parameters. Physical irAEs were scored and biochemical irAEs were measured in the serum (ALT and cytokine levels). Histopathological liver and colon tissue analysis were performed to assess immune cell infiltration and tissue damage.
Similar to early clinical trials of CD40 agonists, in our tumor models we observed liver toxicities and rapid release of proinflammatory cytokines (TNF, interleukin 6, interferon-γ). In the BALB/c strain, anti-CD40 induced severe physical and biochemical irAEs. Concomitant anti-TNF treatment abrogated weight loss, liver damage and colitis, which consequently resulted in an improved clinical score. However, concomitant anti-TNF impaired antitumor response in a proportion of anti-CD40-treated C57BL/6 FoxP3 mice. Delaying TNF blockade in these mice reduced biochemical but not physical irAEs while preserving antitumor efficacy.
Our results suggest concomitant rather than delayed anti-TNF is most effective in reducing biochemical and physical irAEs induced by anti-CD40, although it had the potential to negatively impact antitumor efficacy. Furthermore, our findings highlight the utility of our mouse model to assess the severity of irAEs induced by novel immunotherapeutic agents and evaluate whether their toxicity and antitumor efficacy can be uncoupled.
同时抑制肿瘤坏死因子（TNF）与免疫检查点抑制剂（ICI）可减少临床免疫相关不良事件（irAEs），并似乎能提高临床前肿瘤模型中的抗肿瘤疗效。靶向共刺激受体（如 CD40）的激动性抗体是增强抗肿瘤免疫反应和增强 ICI 活性的另一种策略。然而，在接受抗 CD40 治疗的癌症患者中观察到的剂量限制毒性阻碍了其临床开发。
我们之前描述了一种评估各种有效联合免疫疗法的抗肿瘤活性和 irAEs 的小鼠模型。使用 FoxP3-GFP-DTR（FoxP3）小鼠的 BALB/c 和 C57BL/6 品系，在免疫治疗前短暂耗尽 T 调节细胞（Tregs），降低免疫自身耐受，导致类似于临床报道的一系列理化 irAEs 的发展。在 MC38 和 4T1.2 肿瘤模型中，在短暂耗尽 Treg 后，我们评估了抗 CD40 对抗肿瘤疗效和 irAEs 发展的影响，以及同时或延迟 TNF 阻断对这两个参数的影响。对理化 irAEs 进行评分，并检测血清中的生化 irAEs（ALT 和细胞因子水平）。进行肝和结肠组织的组织病理学分析，以评估免疫细胞浸润和组织损伤。
与 CD40 激动剂的早期临床试验类似，在我们的肿瘤模型中，我们观察到肝毒性和促炎细胞因子（TNF、白细胞介素 6、干扰素-γ）的快速释放。在 BALB/c 品系中，抗 CD40 引起严重的理化 irAEs。同时给予抗 TNF 治疗可消除体重减轻、肝损伤和结肠炎，从而改善临床评分。然而，在一部分接受抗 CD40 治疗的 C57BL/6 FoxP3 小鼠中，同时给予抗 TNF 治疗会削弱抗肿瘤反应。在这些小鼠中延迟 TNF 阻断可减少生化但不减少理化 irAEs，同时保留抗肿瘤疗效。
我们的结果表明，同时而非延迟给予抗 TNF 最能有效减少抗 CD40 引起的生化和理化 irAEs，尽管它有可能对抗肿瘤疗效产生负面影响。此外，我们的研究结果强调了我们的小鼠模型在评估新型免疫治疗药物引起的 irAEs 严重程度以及评估其毒性和抗肿瘤疗效是否可以分离方面的应用价值。
