Project 1: Transgenic TCR-mediated tumor therapy

摘要-项目1 默克尔细胞癌(MCC)是一种高度侵袭性的皮肤癌，每年有2500人被诊断为默克尔细胞癌。 美国。约80%的MCC是由默克尔细胞多瘤病毒(MCPyV)引起的，这些肿瘤依赖于 持续表达的促进细胞周期的癌蛋白(T抗原)。这些病毒T抗原是理想的靶标 用于免疫治疗：它们高度表达，不易丢失，仅限于肿瘤组织，非人类 序列(降低脱靶风险)和高度免疫原性。最近的研究表明，减少 MCC内源性T细胞功能障碍是有效的，因为一半的患者对PD-1轴有持久的反应 封锁。然而，许多患者没有反应，代表着一种未得到满足的临床需求。我们假设 对PD-1阻断无反应的肿瘤患者MCPyV反应T细胞不足或亲和力差 细胞，这种治疗效果可以通过多种方法的组合来提高。 在一项由R01资助的试验中，我们使用“三联疗法”治疗患有转移性疾病的MCC患者，其中 我们联合单次照射逆转MCC特异性下调MHC I类，输注 自体体外扩增的MCPyV特异性CD8+T细胞弥补有效MCPyV特异性的不足 T细胞和Avelumab(一种PD-L1检查点抑制物)，以增强抗原特异性反应。这些治疗方法 耐受性良好，令人鼓舞的有效(6例患者中3例完全缓解，2例持久 AT&GT；2年)，我们已经证明了输注T细胞的持久性、功能和肿瘤定位。 然而，这一策略受到内源性MCPyV特异性T细胞的稀有和低亲和力的限制 大多数患者，需要2-3个月才能产生T细胞产物，在面对快速进展性 疾病。 为了克服遇到的挑战，我们现在提出一种转基因T细胞治疗方法。我们会1) 使用一种新开发的高通量策略来识别安全、高亲和力的人类白细胞抗原限制性T细胞受体 (TCR)，以确保所有患者都能获得高度亲和力的、有效的MCPyV特异性T细胞。我们已经成功地 使用这种方法识别了MCPyV特异的HLAA*0201限制性TCR(TCRA2-MCC1)，现在将 使用这些策略来确定具有3个额外特性的TCR。2)在针对帕金森病患者的I/II期试验中- 1阻断难治性转移性MCC，评价转导自体CD8+T细胞的安全性和有效性 表达与MHC上调和PD-1轴阻断相结合的有效TCRA2-MCC1，以及3)使用 患者样本上的一套尖端工具，用于表征输注的T细胞、MCC细胞和其他特征 肿瘤微环境，确定与治疗反应和/或失败相关的参数。我们 我相信拟议的研究将为下一代T细胞疗法的设计提供关键的见解 MCC患者，以及其他免疫原性恶性肿瘤的影响。

Summary – Project 1 Merkel cell carcinoma (MCC) is a highly aggressive skin cancer diagnosed in >2,500 persons per year in the US. ~80% of MCCs are caused by the Merkel cell polyomavirus (MCPyV), and these tumors rely on persistently-expressed cell cycle promoting oncoproteins (T-Antigens). These viral T antigens are ideal targets for immunotherapies: they are highly expressed, not readily lost, exclusive to tumor tissue, non-human in sequence (reducing off-target risk), and highly immunogenic. Recent studies have shown that reducing dysfunction of endogenous T cells in MCC is effective, as half of patients have durable responses to PD-1 axis blockade. However, many patients do not respond, representing an unmet clinical need. We hypothesize that patients whose tumors do not respond to PD-1 blockade have insufficient or poorly avid MCPyV-responsive T cells, and that therapeutic efficacy can be improved with a combination of approaches. In an R01-funded trial, we have used “Triple Therapy” to treat MCC patients with metastatic disease, where we combined single-fraction radiation to reverse MCC-specific downregulation of MHC class I, infusion of autologous ex vivo-expanded MCPyV specific CD8+ T cells to supplement the lack of effective MCPyV-specific T cells and avelumab (a PD-L1 checkpoint inhibitor) to boost antigen-specific responses. These treatments have been well tolerated, encouragingly effective (with 3 of 6 patients achieving complete remission, 2 durable at >2 years), and we have demonstrated persistence, function, and tumor localization of infused T cells. However, this strategy was limited by the rarity and low avidity of the endogenous MCPyV-specific T cells in most patients, and the 2-3 months required to generate T cell products in the face of rapidly progressive disease. To circumvent the challenges encountered, we now propose a transgenic T cell therapy approach. We will 1) use a newly developed high-throughput strategy to identify safe, high-affinity HLA-restricted T cell receptors (TCRs) to ensure all patients can receive highly avid, effective MCPyV-specific T cells. We have successfully used this approach to identify an MCPyV-specific HLA A*0201-restricted TCR (TCRA2-MCC1) and will now employ these strategies to identify TCRs of 3 additional specificities. 2) in a Phase I/II trial for patients with PD- 1 blockade-refractory metastatic MCC, evaluate the safety and efficacy of autologous CD8+ T cells transduced to express the validated TCRA2-MCC1 combined with MHC upregulation and PD-1 axis blockade, and 3) use a suite of cutting-edge tools on patient samples to characterize infused T cells, MCC cells and other features of the tumor microenvironment, identify parameters associated with treatment responses and/or failures. We believe the proposed studies will provide critical insights into the design of next-generation T cell therapies for MCC patients, with implications for other immunogenic malignancies.