Small molecule enhancers of tumor immunity targeting the LPA5 GPCR

溶血磷脂酸（LPA）GPCR亚型5（LPAR 5）在人和鼠CD 8 细胞毒性T淋巴细胞（CTL），并作为抑制T细胞受体（TCR）的抑制性受体发挥作用 导致肿瘤免疫抑制的信号传导。具体地，通过生理水平的LPAR 5的刺激， LPA显著阻碍抗原特异性TCR诱导的Ca 2+动员、T细胞活化、增殖和增殖。 细胞溶解性肿瘤细胞杀伤功能，导致抗肿瘤免疫应答受损。事实上，CD 8 + T细胞 在降低EG 7淋巴瘤和B16黑色素瘤的生长速率方面， 与野生型（WT）CD 8 + T细胞相比，小鼠中的肿瘤。此外，Lpar 5-/-小鼠的免疫功能降低了85%。 与WT同窝小鼠相比，B16黑色素瘤源性肺转移的发生率，具有稳健的CD 8 + CTL 在发展很少肺转移的Lpar 5-/-小鼠中观察到浸润。这些数据突出了一个独特的作用 对于LPAR 5作为调节免疫监视和细胞毒性效应器功能的免疫检查点分子。 本提案的目的是确定临床适用的LPAR 5小分子抑制剂 用于癌症治疗的免疫调节剂。使用经验证的方法对200万种化合物进行虚拟筛选（VS） LPAR模型鉴定了超过300个命中，其中90个对LPAR 5拮抗剂化合物具有选择性， 不同的脚手架。此外，200 K化合物的高通量筛选（HTS）活动和二级筛选（二级筛选）也将在2010年进行。 对19个经验证的命中的分析已经导致鉴定出两种不同的分子支架。的 最有希望的命中，SRI-42730，在五个独立的测定中证明了LPAR 5拮抗作用：β-抑制蛋白 在HTS平台和体内实施募集、Ca 2+动员、TGFα脱落、IL-2产生 在B16鼠黑素瘤转移模型中的功效。我们已经发现的新的热门和类似物 将在以下拟定研究中用作工具化合物：1）进行靶向药物化学 LPAR 5拮抗剂的优化。计算方法将包括HTS命中的支架跳跃，以及 药效团模型的产生，以帮助合成新化合物的效力和选择性的优化， 2）确定新型拮抗剂对LPA GPCR亚型和自分泌运动因子的特异性 溶血磷脂酶; 3）通过加强抗原特异性TCR的效力对特异性拮抗剂命中进行排名 在LPA存在下的活化和IL-2产生; 4）.然后将在细胞中评估8种关键化合物 在体内毒性研究和动物疗效之前，对3种化合物进行PK分析的试验 问题研究5)确定提名的三种潜在先导化合物在增强肿瘤免疫力方面的功效 使用鼠和同种异体人体外肿瘤杀伤测定和体内鼠转移接种， 进展模型本研究的影响将是确定和提名单一线索 化合物和结构多样的LPAR 5拮抗剂库用于进一步的临床前开发。

Lysophosphatidic acid (LPA) GPCR subtype 5 (LPAR5) is abundantly expressed by human and murine CD8 cytotoxic T lymphocytes (CTLs) and functions as an inhibitory receptor that represses T cell receptor (TCR) signaling leading to inhibition of tumor immunity. Specifically, stimulation of LPAR5 by physiological levels of LPA significantly impedes antigen specific TCR-induced Ca2+ mobilization, T cell activation, proliferation and cytolytic tumor cell killing functions, resulting in an impaired anti-tumor immune response. Indeed, CD8+ T cells lacking LPAR5 expression are more effective at reducing the growth rate of EG7 lymphoma and B16 melanoma tumors in mice compared to wild type (WT) CD8+ T cells. Moreover, Lpar5 -/- mice have 85% reduction in the incidence of B16 melanoma-derived lung metastasis compared to WT littermates, with a robust CD8+ CTL infiltration observed in the Lpar5 -/- mice that developed few lung metastasis. These data highlight a unique role for LPAR5 as an immune checkpoint molecule regulating immune surveillance and cytotoxic effector function. The objective of this proposal is to identify small molecule inhibitors of LPAR5 as clinically applicable immunomodulators for cancer treatment. A virtual screening (VS) of 2 million compounds using validated LPAR models identified more than 300 hits of which 90 were selective for LPAR5 antagonist compounds with diverse scaffolds. In addition, a high throughput screening (HTS) campaign of 200K compounds and secondary analyses of 19 validated hits have already resulted in the identification of two distinct molecular scaffolds. The most promising hit, SRI-42730, demonstrated LPAR5 antagonism in five independent assays: β-arrestin recruitment, Ca2+ mobilization, TGFα-shedding, IL-2 production implemented in HTS platform and in vivo efficacy in the B16 murine melanoma metastasis model. The novel hits and analogs we have already identified will be used as tool compounds in the following proposed studies: 1) Perform hit-to-lead medicinal chemistry optimization of LPAR5 antagonists. Computational approaches will include scaffold hopping on HTS hits, and the generation of a pharmacophore model to aid synthetic optimization of potency and selectivity of newly designed analogs; 2) Determine the specificity of novel antagonists at LPA GPCR subtypes and autotaxin lysophospholipase enzyme; 3) Rank specific antagonist hits by potency in boosting antigen-specific TCR activation and IL-2 production in the presence of LPA; 4). 8 key compounds will then be evaluated in cellular assays from which 3 compounds will undergo PK analysis prior to in vivo tox studies and animal efficacy studies. 5) Determine efficacy of nominated three potential lead compounds in boosting tumor immunity using murine and allogeneic human in vitro tumor killing assays and in vivo murine metastasis seeding and progression models. The impact of this research will be the identification and nomination of a single lead compound and a pool of structurally diverse LPAR5 antagonists for further preclinical development.