Novel Drug for Cancer Immunotherapy that Targets Phosphatidylserine

摘要 根据越来越多的证据，磷脂酰丝氨酸(PS)正在成为一个有吸引力的免疫治疗靶点 突出了它与免疫抑制的因果联系。我们已经确定外切体来源于黑色素瘤 卵巢肿瘤微环境在其表面表达PS并抑制多个激活终点 通过T细胞受体触发的T细胞。研究还表明，PS在细胞表面的表达 许多非凋亡性癌细胞会导致免疫抑制。黑色素瘤患者的最新临床研究 证明从患者肿瘤中释放的外切体抑制T细胞肿瘤的杀伤并有助于 与肿瘤进展有关。我们设计并合成了一种新的化合物，锌-DPA)6-DP-15K(ExoBlock 与磷脂酰丝氨酸结合，亲和力高。ExoBlock被证明一致并显著地阻止了 黑色素瘤外切体和卵巢肿瘤微环境的体外免疫抑制活性。 基于这些发现，我们预测ExoBlock将增强T细胞对肿瘤细胞的杀伤作用 肿瘤移植瘤由于其与PS结合在外周小体上，肿瘤细胞和凋亡细胞，代表了一种多细胞 多管齐下的方法。我们使用两种不同的人类肿瘤异种移植模型验证了这一预测：a)之前的 使用患者来源卵巢建立的内部开发的大网膜肿瘤异种移植模型(OTX 肿瘤，以及b)最近开发和验证的异种小鼠(X-小鼠)模型，它允许我们 在临床前对多种T细胞刺激免疫疗法的疗效进行量化和确定。这 模型使用黑色素瘤患者来源的肿瘤特异性T细胞过继转移到免疫缺陷 携带黑色素瘤移植瘤的小鼠，表达T细胞识别的肿瘤新抗原。治疗性 接下来，通过显著增强OTX和X-TX对肿瘤的抑制作用，确立了ExoBlock的疗效。 小鼠模型，并被发现与X-小鼠模型中抗PD-1治疗相当。总而言之，这些结果 为我们在第一阶段申请中提出的工作奠定了基础和理论基础。额外的毒性和 建议在AIM 1中对ExoBlock进行药代动力学(PK)研究。PK研究将有助于确定 将在目标2中测试的ExoBlock的最佳剂量、时间表和给药方法。在目标2中，ExoBlock将是 在由患者来源的大网膜肿瘤异种移植(OTX)模型中进行体内治疗效果测试 卵巢肿瘤和带有B16-F10肿瘤的同基因小鼠黑色素瘤模型。我们使用人类的理由是 并以小鼠肿瘤模型为例进行了讨论。这一阶段研究的结果将奠定基础 在未来的第二阶段研究中进行更广泛的研究，这将导致ExoBlock的IND和临床试验。

Abstract Phosphatidylserine (PS) is emerging as an attractive immunotherapeutic target in the light of mounting evidence highlighting its causal link to immune suppression. We have established that exosomes derived from melanoma and ovarian tumor microenvironments express PS on their surfaces and suppress multiple activation endpoints of T cells triggered through the T cell receptor. Studies have also shown that expression of PS on the surface of many non-apoptotic cancer cells lead to immunosuppression. Recent clinical studies in melanoma patients demonstrated that exosomes that are released from patient tumors suppress T cell tumor killing and contribute to tumor progression. We have designed and synthesized a new compound, Zn-DPA)6-DP-15K (ExoBlock) that binds to phosphatidylserine with high avidity. ExoBlock was shown to consistently and significantly block the immune suppressive activity of exosomes derived from melanoma and ovarian tumor microenvironments in vitro. Based upon these findings, we predicted that ExoBlock would enhance the killing of tumor cells by T cells in tumor xenografts due to its binding to PS on the exosomes, tumor and apoptotic cells, representing a multi- pronged approach. We tested this prediction using two different human tumor xenograft models: a) the previously validated in-house developed omental tumor xenograft (OTX) model established using patient-derived ovarian tumors, and b) the recently developed and validated Xenomimetic mouse (X-mouse) model that allows us to quantify and establish the efficacy of multiple T cell-stimulating immune-based therapies pre-clinically. This model uses melanoma patient-derived tumor-specific T cells that are adoptively transferred into immunodeficient mice bearing melanoma xenografts expressing tumor neo-antigens recognized by the T cells. The therapeutic efficacy of ExoBlock was next established by significantly enhancing tumor suppression in both the OTX and X- mouse models, and was found to be comparable to anti-PD-1 therapy in X-mouse model. Together, these results have laid the foundation and rationale for our work proposed in the Phase I application. Additional toxicity and pharmacokinetic (PK) studies are proposed for ExoBlock in Aim 1. The PK studies will help to determine the optimal dose, schedule and delivery method of ExoBlock that will be tested in aim 2. In Aim 2 ExoBlock will be tested in vivo for its therapeutic efficacy in omental tumor xenograft (OTX) model consisting of patient-derived ovarian tumor and syngeneic mouse melanoma model with B16-F10 tumor. Our rationale for using both a human and mouse tumor model is discussed in the Approach. The results of this Phase 1 study will lay the foundation for a more extensive study in a future phase 2 study that will lead to an IND and clinical trial of ExoBlock.