Development and Mechanistic Studies of an Engineered Human Enzyme to Abrogate Immune Suppression due to Elevated Methylthioadenosine (MTA) by MTAP null/low Tumors

一种工程化人类治疗药物的研制及机理研究 甲硫腺苷(MTA)升高对MTAP阴性/低度肿瘤的免疫抑制作用 在许多癌症中观察到的最常见的损害之一是纯合子基因 甲基硫代腺苷磷酸酶(MTAP)的缺失，MTAP是一种正常作用于氨基酸和 核苷酸循环途径。MTAP在肿瘤中的缺失导致其积聚和分泌 底物甲硫腺苷(MTA)。已证实MTA是一种非常有效的免疫抑制分子； 重要的是，在初步研究中，我们的实验室从多种小鼠肿瘤模型中获得了强有力的活体证据 MTAP零/低肿瘤产生的MTA强烈地减弱了抗肿瘤免疫反应。这 提案描述了德克萨斯大学奥斯汀分校的一个跨学科团队的努力，详细描述了这一发展 一种新的生物癌症治疗方法，逆转MTA的免疫抑制作用并辅助治疗 将MTAP零/低肿瘤患者作为一个关键的生物标志物。在初步研究中，我们已经证明 给予工程化的人MTA降解剂(基于人MTAP)可以逆转 MTA对体外淋巴细胞的有害作用，严重阻碍或完全抑制淋巴细胞的生长 MTAP缺失型小鼠同种异体肿瘤移植物的缓解及肿瘤和肿瘤中T细胞的恢复 引流淋巴结(TDLN)，联合使用时表现出相加/协同效应 现有的免疫检查点抑制剂。 MTAP缺失可抑制免疫效应细胞和促进免疫的证据 通过MTA积聚的耐受性基质细胞表型现在提示了一个明确的机制来解释为什么 在癌症中观察到的最常见的基因缺失之一。总体而言，我们假设MTAP删除在 癌症是一个免疫检查点，可以通过酶降解MTA在治疗上逆转 使用工程化的人甲硫腺苷磷酸化酶的肿瘤微环境。这项工作 本文旨在：(I)阐明细胞免疫学、生化/代谢组学和信号转导 细胞外MTA升高抑制免疫功能的机制(S)；(Ii)有助于阐明MTA- 介导的甲基转移酶抑制和代谢重塑以及(可能是继发性的)激活 嘌呤能受体对淋巴细胞的影响；(Iii)检查联合治疗的疗效 标准护理抗体免疫检查点抑制剂和非常重要的(Iv)开发一种优化的MTA 具有晚期/临床前/临床给药所需药理特性的降解性药物。

Development and Mechanistic Studies of an Engineered Human Therapeutic to Abrogate Immune Suppression due to Elevated Methylthioadenosine (MTA) by MTAP null/low Tumors One of the most common lesions observed across a broad number of cancers is the homozygous genetic deletion of methylthioadenosine phosporylase (MTAP), an enzyme that normally functions in amino acid and nucleotide recycling pathways. Deletion of MTAP in tumors results in the accumulation and secretion of its substrate methylthioadenosine (MTA). It is established that MTA is a very potent immunosuppressive molecule; importantly in preliminary studies our lab obtained strong in vivo evidence from multiple murine tumor models that the production of MTA by MTAPnull/low tumors strongly attenuates anti-tumor immune responses. This proposal describes an interdisciplinary team effort at the University of Texas at Austin detailing the development of a novel biologic cancer therapeutic, to reverse the immunosuppressive effects of MTA and aid in the treatment of patients with MTAPnull/low tumors as a key biomarker. In preliminary studies we have demonstrated that administration of an engineered human MTA degrading therapeutic (based on the human MTAP) can reverse the deleterious effects of MTA on lymphocytes in vitro, drastically retards the growth or elicits complete remissions of MTAP null murine cancer allografts and restores populations of T cells in both the tumor and tumor draining lymph node (TDLN) and demonstrates additive/synergistic effects when used in combination with existing immune checkpoint inhibitors. The evidence that the consequence of MTAP deletion acts to suppress immune effector cells and promote tolerogenic stromal cell phenotypes through the buildup of MTA now suggests a clear mechanism for why this is one of the more common gene deletions observed in cancer. Overall, we hypothesize that MTAP deletions in cancers act as an immune checkpoint that can be reversed therapeutically by enzymatic degradation of MTA in the tumor microenvironment using an engineered human methylthioadenosine phosphorylase. The work proposed here will seek to: (i) elucidate the cellular immunology and the biochemical/metabolomic and signaling mechanism(s) through which elevated extracellular MTA suppresses immune function; (ii) help clarify how MTA- mediated methyltransferase inhibition and remodeling of metabolism together with (likely secondarily) activation of the purinergic receptors impact lymphocytes; (iii) examine the efficacy of combinatorial treatments using standard of care antibody immune checkpoint inhibitors and very importantly (iv) develop an optimized MTA degrading drug that has the requisite pharmacological properties for late/stage preclinical/clinical administration..