Modulating the PD-1/PD-L1 checkpoint to promote antitumor activity of HER2 CAR T cells in patients with sarcoma

项目总结/摘要 免疫疗法对儿童肉瘤的疗效有限。在我们最近完成的一期研究中， 输注HER 2靶向嵌合抗原受体T细胞（CAR-T）是安全的， 抗肿瘤活性的指标，包括三种持久的完全反应。这项研究的主要观察结果是， （1）淋巴细胞耗竭促进CAR-T扩增，但仅略微改善持久性，（2）过继性 转移的CAR-T对免疫抑制敏感，和（3）抗原下调/丢失与 疾病复发。虽然文献缺乏免疫抑制机制和肿瘤适应性， 我们的研究结果与其他人在早期临床和临床前研究中的观察结果一致， 用于实体瘤的细胞疗法。我们的长期目标是开发新的方法， 这可能是释放CAR-T对抗肉瘤和其他实体瘤潜力的关键。 整合策略以预先解决这些代偿机制的治疗方法可能 减轻下游肿瘤逃逸和复发。该项目的目标是进行前瞻性临床研究 HER 2 CAR-T联合PD-1/PD-L1检查点破坏策略在疾病特异性 队列。中心假设是联合免疫疗法将促进免疫浸润、重塑和/或免疫抑制。 肿瘤微环境，减轻CAR-T功能障碍，从而改善抗肿瘤反应。我们 具体目的将检验以下假设：（目的1）抗PD-1抗体和HER 2 CAR-1的组合， 淋巴细胞清除后给予T在肉瘤患者中是安全的，将改善CAR-T动力学，并将引起 抗肿瘤反应;（目标2）在治疗患者中进行基于细胞和血清的研究将有助于确定生物标志物 （目的3）工程化CAR-T，以积极转化PD-1/PD-L1相互作用， 肿瘤微环境将增强细胞产物的抗肿瘤作用 以提高其安全性。我们将通过开展第一阶段研究，评估目标1和2， 环磷酰胺和氟达拉滨淋巴细胞清除后的自体HER 2 CAR-T和抗PD-1抗体 肉瘤患者（HEROS 3.0临床试验）。在目标3中，我们将开发一种研究性新药（IND）， 共表达PD-1检查点逆转受体（CPR）的HER 2 CAR-T。在项目结束时，我们将 了解CAR-T是否可以安全地与免疫检查点抑制一起使用以改善治疗 儿童和年轻人肉瘤的结果。这些贡献的意义在于：（1） 建立肉瘤联合免疫治疗的临床效用，（2）潜在地识别“可修改的” 患者和治疗相关因素，以指导CAR-T治疗的未来改进，以及（3）使临床 测试创新的CAR-T平台。这些知识对于推动该领域的发展至关重要， 难治性肉瘤仍然大部分无法治愈。

PROJECT SUMMARY/ABSTRACT Immunotherapy has shown limited efficacy against pediatric sarcoma. In our recently completed phase I study, infusion of HER2-targeted chimeric antigen receptor T cells (CAR-T) was safe and showed encouraging indicators of antitumor activity, including three durable complete responses. The key observations from this study are: (1) lymphodepletion promotes CAR-T expansion but only marginally improves persistence, (2) adoptively transferred CAR-T are susceptible to immune inhibition, and (3) antigen downregulation/loss is associated with disease relapse. While the literature is lacking on immune inhibitory mechanisms and tumor adaptations in sarcoma, our findings are in line with observations made by others in early clinical and pre-clinical studies of cellular therapy for solid tumors. Our long-term goal is to develop new approaches that capitalize on expected tumor defenses which may be key to unleashing the potential of CAR-T against sarcomas and other solid tumors. Therapeutic approaches that integrate strategies to address these compensatory mechanisms up front may mitigate downstream tumor escape and relapse. The objective of this project is to conduct prospective clinical testing of HER2 CAR-T in combination with PD-1/PD-L1 checkpoint disruption strategies in a disease-specific cohort. The central hypothesis is that the combination immunotherapy will promote immune infiltration, remodel the tumor microenvironment, alleviate CAR-T dysfunction, and thereby improve antitumor responses. Our specific aims will test the following hypotheses: (Aim 1) The combination of anti-PD-1 antibody and HER2 CAR- T administered after lymphodepletion is safe in patients with sarcoma, will improve CAR-T kinetics, and will elicit antitumor responses; (Aim 2) Cellular and serum-based studies in treated patients will help identify biomarkers of toxicity and response; and (Aim 3) Engineering CAR-T to positively transform the PD-1/PD-L1 interaction in the tumor microenvironment will potentiate antitumor effects of the cellular product while incorporating design attributes to enhance its safety . We will evaluate Aims 1 and 2 through implementation of a phase I study of autologous HER2 CAR-T and anti-PD-1 antibody after cyclophosphamide and fludarabine lymphodepletion in patients with sarcoma (HEROS 3.0 clinical trial). In Aim 3, we will develop an investigational new drug (IND) for HER2 CAR-T co-expressing a PD-1 checkpoint reversal receptor (CPR). At the conclusion of the project, we will understand if CAR-T can be safely administered with immune checkpoint inhibition to improve treatment outcomes for children and young adults with sarcoma. The significance of these contributions are: (1) establishing the clinical utility of combination immunotherapy for sarcoma, (2) potentially identifying “modifiable” patient- and treatment-related factors to guide future improvements to CAR-T therapy, and (3) enabling clinical testing of an innovative CAR-T platform. This knowledge is critical to advancing the field, as recurrent or refractory sarcomas remain largely incurable.