Small molecule enhancers of tumor immunity targeting the LPA5 GPCR

溶血磷脂酸(LPA)GPCR5亚型(LPAR5)在人和小鼠CD8中大量表达 细胞毒性T淋巴细胞(CTL)，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。具体地说，生理水平的LPAR5刺激 LPA显著抑制抗原特异性TCR诱导的钙动员、T细胞活化、增殖和... 杀伤肿瘤细胞的细胞功能，导致抗肿瘤免疫反应受损。事实上，CD8+T细胞 缺乏LPAR5表达对降低EG7淋巴瘤和B16黑色素瘤的生长速度更有效 小鼠肿瘤与野生型(WT)CD8+T细胞的比较。此外，Lpar5-/-小鼠的 CD8+CTL强健的B16黑色素瘤患者肺转移发生率与小鼠相比 在肺转移较少的Lpar5-/-小鼠中观察到了浸润现象。这些数据突显了一个独特的角色 LPAR5作为一种免疫检查点分子，调节免疫监视和细胞毒效应功能。 这项建议的目的是确定LPAR5的小分子抑制剂可用于临床 用于癌症治疗的免疫调节剂。使用VALIDATED对200万个化合物进行虚拟筛选(VS) LPAR模型识别了300多次命中，其中90次对LPAR5拮抗剂化合物具有选择性 不同的脚手架。此外，高通量筛选(HTS)活动包括200,000种化合物和二次 对19个有效HIT的分析已经导致了两个不同的分子支架的鉴定。这个 最有希望的HIT，SRI-42730，在五个独立的检测中显示了LPAR5拮抗作用：β-arrestin 在高温超导平台和体内实现的募集、钙动员、转化生长因子α释放、IL-2产生 对B16小鼠黑色素瘤转移模型的疗效。我们已经确定了这部小说的热门作品和类比 将在以下拟议的研究中用作工具化合物：1)进行Hit-to-Lead药物化学 LPAR5拮抗剂的优化。计算方法将包括HTS点击的脚手架跳跃，以及 药效团模型的建立有助于新药效价和选择性的综合优化 设计类似物；2)确定新的LPA GPCR亚型拮抗剂和自体趋化因子的特异性 溶血磷脂酶；3)根据增强抗原特异性TCR的效力对特异性拮抗剂进行排序 在LPA存在的情况下激活和产生IL-2；8种关键化合物随后将在细胞中进行评估 在体内毒性研究和动物疗效研究之前，将对3种化合物进行PK分析的分析 学习。5)确定提名的三种潜在先导化合物增强肿瘤免疫的有效性 用小鼠和同种异体人体外肿瘤杀伤试验和体内小鼠转移种植和 发展模型。这项研究的影响将是确定和提名一个单一的线索 化合物和结构多样化的LPAR5拮抗剂，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.