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

工程化人治疗剂的研制及机理研究 MTAP无效/低肿瘤导致甲硫腺苷（MTA）升高导致的免疫抑制 在许多癌症中观察到的最常见的病变之一是纯合子遗传性肿瘤， 缺失甲硫腺苷磷酸化酶（MTAP），该酶通常在氨基酸中起作用， 核苷酸循环途径。肿瘤中MTAP的缺失导致其在肿瘤中的积累和分泌。 底物甲硫腺苷（MTA）。已经确定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体内证据 由MTAP无效/低肿瘤产生的MTA强烈减弱抗肿瘤免疫应答。这 一份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，详细介绍了开发 一种新的生物癌症治疗方法，逆转MTA的免疫抑制作用， 作为关键生物标志物的MTAP无效/低肿瘤患者。在初步研究中，我们已经证明， 施用工程化的人MTA降解治疗剂（基于人MTAP）可以逆转 MTA在体外对淋巴细胞的有害作用， MTAP无效小鼠癌症同种异体移植物的缓解和肿瘤和肿瘤内T细胞群的恢复 引流淋巴结（TDLN），并在与以下药物联合使用时表现出累加/协同作用： 免疫检查点抑制剂。 MTAP缺失的结果起到抑制免疫效应细胞和促进免疫应答的作用的证据。 现在，通过MTA的积累，致耐受性基质细胞表型表明了为什么这是一个明确的机制， 是癌症中最常见的基因缺失之一总的来说，我们假设MTAP缺失在 癌症作为免疫检查点，可以通过MTA的酶促降解在治疗上逆转， 肿瘤微环境使用工程改造的人甲硫腺苷磷酸化酶。工作 这里提出的将寻求：（i）阐明细胞免疫学和生物化学/代谢组学和信号传导 升高的细胞外MTA抑制免疫功能的机制;（ii）帮助澄清MTA- 介导的甲基转移酶抑制和代谢重塑以及（可能继发）活化 嘌呤能受体的影响淋巴细胞;（iii）检查组合治疗的功效， 护理标准抗体免疫检查点抑制剂，并且非常重要的是（iv）开发优化的MTA 具有后期/阶段临床前/临床给药所需药理学性质的降解药物。

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..