Cytotoxic lymphocyte function PET imaging to predict cancer immunotherapy response

摘要 最近在理解免疫检查点在唐氏综合症中的作用方面取得了重大进展。 调节对癌症的免疫反应。这些发现反过来又导致了免疫系统的发展。 激活细胞毒性T细胞的检查点抑制剂，并已显示出惊人的积极临床结果 横跨多种肿瘤类型。然而，尽管许多患者持续缓解，但总体应答率 仍然很低。免疫检查点抑制剂也与高比例的潜在致命性 与免疫相关的不良事件。此外，评估治疗反应是具有挑战性的，因为肿瘤可能 最终，由于免疫细胞的涌入，解剖成像显示Response的大小会增加。这 同样的免疫渗透使FDG-PET分析变得模糊，因为免疫细胞高度依赖FDG。缺乏一种 有用的反应评估使患者护理和临床发展变得非常复杂。病人是 经常持续治疗的时间超过必要的时间，因为无法确定它们是否有效。 为了解决反应评估的困难，已经进行了大量的调查工作 预测性生物标志物，包括新的成像方法。到目前为止分析的成像生物标记物有 专注于识别肿瘤免疫浸润物的存在，并未被证明对 回应。它们缺乏实用性可能是因为它们不能区分主动免疫和非主动免疫 后者被认为是免疫治疗失败的常见原因。要监视 为了提高细胞毒性T淋巴细胞(CTL)活性，我们开发了一种一流的基于多肽的PET显像剂 它与颗粒酶B结合，颗粒酶B是CTL在积极攻击肿瘤细胞时释放的一种丝氨酸蛋白酶。 我们已经在两种不同的免疫治疗模型中展示了我们的显像剂，并表明它能够 预测对检查点抑制剂的反应。我们还审问了使用检查点抑制剂治疗的人类 黑色素瘤标本中颗粒酶B的表达。这些结果证实了我们的临床前发现的高 颗粒酶B的表达与免疫治疗应答相关。最后，我们设计了一个人体模拟器 我们的多肽与人体样本中的颗粒酶B特异性结合。这项提案旨在敲定一项 优化人体探头，告知患者群体和近期临床评估的时机。至 为了实现这一目标，我们将首先开发第二代多肽，这些多肽可能会增强亲和力或 颗粒酶B测定的药代动力学改进及其在人源化小鼠中的评价 免疫治疗模式。为了更好地构建临床试验成像时间点，我们将继续我们的 人类检查点抑制因子治疗的黑色素瘤活检标本中颗粒酶B表达的评估 以给药间隔为重点的目标表达的量化将有助于通过以下方式最大化临床影响 在进行后续治疗之前确定反应。共同努力，我们希望这些目标能够迅速实现 将颗粒酶B成像技术应用于临床，提供急需的反应生物标记物。

Abstract There have been recent significant advances in understanding the role that immune-checkpoints play in down regulating the immune response to cancer. These discoveries have in turn led to the development of immune- checkpoint inhibitors that activate cytotoxic T-cells, and have demonstrated strikingly positive clinical outcomes across multiple tumor types. However, despite durable remissions in many patients, the overall response rate remains low. Immune checkpoint inhibitors are also associated with a high percentage of potentially lethal immune-related adverse events. Further, assessing therapeutic response is challenging, as tumors that may ultimately respond can appear to increase in size on anatomic imaging due to an influx of immune cells. This same immune infiltrate obscures FDG-PET analysis, as the immune cells are highly FDG avid. The lack of a useful response assessment has significantly complicated patient care and clinical development. Patients are frequently kept on therapies longer than necessary, as it cannot be ascertained whether they are responding. In order to address the difficulty with response assessment, there has been significant effort investigating predictive biomarkers, including novel imaging methods. The imaging biomarkers analyzed thus far have focused on identifying the presence of tumoral immune infiltrate and have not proven strongly predictive of response. Their lack of utility is likely because they cannot distinguish between active and inactive immune infiltrate, the latter of which is hypothesized to be a common cause of immunotherapy failure. To monitor cytotoxic T lymphocyte (CTL) activity, we have developed a first-in-class peptide-based PET imaging agent that binds to granzyme B, a serine protease released by CTLs when they are actively attacking tumor cells. We have demonstrated our imaging agent in two different immunotherapy models and shown that it is able to predict response to checkpoint inhibitors. We have also interrogated checkpoint-inhibitor treated human melanoma samples for granzyme B expression. These results corroborate our pre-clinical findings of high granzyme B expression correlating with response to immunotherapy. Finally, we designed a human analogue of our peptide, which specifically bound to granzyme B in human samples. This proposal aims to finalize an optimized human probe and inform the patient population and timing for near-term clinical evaluation. To achieve this goal, we will first develop second-generation peptides that may provide enhanced affinity or improved pharmacokinetics for granzyme B measurement, and assess them in humanized mouse immunotherapy models. In order to better structure clinical trial imaging time-points, we will continue our assessment of granzyme B expression in human checkpoint inhibitor treated melanoma biopsy specimens. Quantification of target expression focused on dosing intervals will help to maximize clinical impact by identifying response prior to administration of subsequent therapy. Together, we hope these aims can rapidly advance granzyme B imaging into the clinic to provide the response biomarker that is so desperately needed.