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，在美国每年有超过2,500人被诊断出。 美方约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 持续表达的细胞周期促进癌蛋白（T抗原）。这些病毒T抗原是理想的靶点 对于免疫疗法：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中的内源性T细胞功能障碍是有效的，因为一半的患者对PD-1轴具有持久的应答 封锁然而，许多患者没有反应，代表未满足的临床需求。我们假设 肿瘤对PD-1阻断无应答的患者，其MCP γ V应答性T细胞不足或亲和力差， 细胞，并且可以通过方法的组合来改善治疗功效。 在R 01资助的试验中，我们使用“三联疗法”来治疗患有转移性疾病的MCC患者，其中 我们结合单次照射逆转MHC I类分子的MCC特异性下调， 自体离体扩增的MCPyV特异性CD 8 + T细胞，以补充有效的MCPyV特异性CD 8 + T细胞的缺乏， T细胞和avelumab（PD-L1检查点抑制剂），以增强抗原特异性反应。这些治疗 耐受性良好，有效（6例患者中有3例达到完全缓解，2例持久缓解， 在>2年），并且我们已经证明了输注的T细胞的持久性、功能和肿瘤定位。 然而，这种策略受到了小鼠中内源性MCPyV特异性T细胞的稀有性和低亲合力的限制。 大多数患者，和2-3个月所需的T细胞产生的产品，在面对迅速进行性 疾病 为了规避所遇到的挑战，我们现在提出了一种转基因T细胞治疗方法。我们将（1） 使用新开发的高通量策略来识别安全、高亲和力的HLA限制性T细胞受体 （TCR），以确保所有患者都能接受高度亲和力、有效的MCP γ V特异性T细胞。我们已经成功 使用这种方法鉴定MCPyV特异性HLA A*0201限制性TCR（TCRA 2-MCC 1），现在将 使用这些策略来鉴定3种额外特异性的TCR。2)在PD患者的I/II期试验中， 1例阻断难治性转移性MCC，评估自体CD 8 + T细胞转导的安全性和有效性。 表达经验证的TCRA 2-MCC 1与MHC上调和PD-1轴阻断的组合，和3）使用经验证的TCRA 2-MCC 1与MHC上调和PD-1轴阻断的组合，和 一套先进的工具，用于患者样本，以表征输注的T细胞，MCC细胞和其他特征， 肿瘤微环境识别与治疗反应和/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重要的见解， MCC患者，与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.