Dissecting the mechanistic basis of response to combined decitabine and ipilimumab following hematopoietic stem cell transplantation for relapsed acute myelogenous leukemia

异基因造血干细胞移植(HCT)主要基于强大的移植物抗白血病效应(GVL)，为高危急性髓系白血病(AML)提供了潜在的治疗方法。HCT后AML复发仍然是死亡率的主要来源，因此，提高GVL的努力是高度优先的。同时，尽管HCT的临床记录已有很长时间，但GVL的发病机制仍未完全阐明。最近，免疫调节剂(如检查点阻断)和现有的积极治疗方法(如去甲基化药物)的临床应用为增强GVL打开了新的大门。单独使用这些药物的临床试验显示，在解决HCT后AML复发方面具有良好的临床活性，这表明联合使用这些治疗方式可能会提供更好的疗效。这就是DFCI正在进行的NCI ETCTN/CTEP第一阶段研究(#10026)的基本原理，该研究试图探索爱普利单抗和地西他滨在急性髓细胞白血病HCT后复发中的联合应用。早期的数据表明，这种方法在临床上是积极的。我们假设，联合应用地西他滨和伊普利单抗的应答者将具有不同的疾病和免疫微环境特性，并表现出对肿瘤抗原的激活的T细胞反应。来自这项研究的专门的纵向生物样品收集提供了一个丰富的机会来剖析这种新的治疗组合后的反应基础。今天，强大的研究工具可以用来以前所未有的深度研究癌症免疫学。大规模并行测序、高通量单细胞技术和计算导向的抗原发现方法为全面评估研究对象的样本提供了令人兴奋的基础。通过应用先进的免疫基因组学工具，并以我在肿瘤反应性T细胞的单个T细胞受体(TCR)分析方面的经验为基础，我的目标是阐明GVL效应背后的免疫机制。AIM 2将使用流式细胞术、单细胞RNA测序和质量细胞术跟踪免疫微环境的定量和定性变化。目的3将利用单个TCR测序和发现肿瘤反应性TCR的同源抗原的方法来了解肿瘤抗原-T细胞相互作用驱动反应。这些目的的完成有望揭示HCT后免疫反应的重要原理，并将阐明检查点阻断和低甲基化药物如何增强GVL。这将具有直接的临床意义，因为结果可能有助于识别从这种治疗组合中受益的患者，并可能为开发新的治疗方法铺平道路，如接种疫苗或采用T细胞转移策略。

Allogeneic hematopoietic stem cell transplantation (HCT) provides potentially curative therapy for high-risk acute myelogenous leukemia (AML), mainly based on potent graft-versus-leukemia effects (GvL). Relapse of AML after HCT remains the key source of mortality, and hence efforts to enhance GvL are of high priority. At the same time, despite the long-established clinical track record of HCT, the mechanistic basis of GvL remains not fully elucidated.The recent clinical availability of immunomodulatory agents such as checkpoint blockade along with existing active therapeutics, for example hypomethylating agents, opens new doors for enhancing GvL. Clinical trials with single use of these agents have demonstrated promising clinical activity in addressing post-HCT AML relapse, suggesting combination of these treatment modalities could provide even greater effectiveness. This was the rationale for an ongoing NCI ETCTN/CTEP phase I study (#10026) at DFCI which seeks to probe the combination of ipilimumab and decitabine in AML relapse post-HCT. Early data indicate that this approach is clinically active.We hypothesize that responders to combined decitabine and ipilimumab will have distinct disease and immune microenvironment properties and show activated T cell responses against tumor antigens. The dedicated longitudinal biospecimen collection from this study provides a rich opportunity to dissect the basis of response following this novel therapeutic combination. Today powerful research tools are available to study cancer immunology at unprecedented depth. Massively parallel sequencing, high throughput single cell technologies and computationally guided antigen discovery approaches provide exciting foundations for comprehensive evaluation of samples from study subjects. Through application of advanced immunogenomic tools and building on my experience in single T cell receptor (TCR) analysis of tumor-reactive T cells, my objective is to elucidate the immune mechanisms underlying GvL effects.Aim 1 will thus undertake genomic evaluation of tumor samples to link response to disease-specific properties such as tumor antigen load and expression of genes critical to immune signaling pathways. Aim 2 will track quantitative and qualitative changes in the immune microenvironment using flow cytometry, single-cell RNA sequencing and mass cytometry. Aim 3 will exploit single TCR sequencing and methods to uncover cognate antigens of tumor-reactive TCRs to understand tumor antigen-T cell interactions driving responses.Completion of these aims is expected to reveal important principles of immune responses after HCT and will shed light on how checkpoint blockade and hypomethylating agents enhance GvL. This will have direct clinical implications as the results could aid in identifying patients that benefit from this therapeutic combination and might pave the way for developing novel therapeutic approaches like vaccination or adoptive T cell transfer strategies.