Imaging Acidosis and Immune Therapy in PDAC

摘要 胰腺导管腺癌(PDAC)是所有癌症中最致命的，对所有癌症都有很大的耐药性 治疗，包括免疫治疗(IT)。尽管存在这种阻力，但仍有不少于12家开放诊所 研究使用检查点封锁IT治疗PDAC的试验。有多种机制可以 解释这种耐药性，包括PDAC肿瘤的酸中毒，这是由于高糖酵解率 再加上血流灌注率低。将激活的T细胞放置在酸性条件下会深刻地抑制它们的 效应器功能。我们已经证明，口服NaHCO3中和小鼠肿瘤酸中毒模型 PDAC可以显著改善对检查站封锁的反应。然而，I/IIa期临床 使用重碳酸盐的试验未能提高剂量。因此，迫切需要开发在临床上可行的方法。 实现相同结果的替代方案，即。体内中和肿瘤酸度，以便与IT结合。一个 旨在直接中和肿瘤酸度的疗法是一种经过临床测试的CEACAM6靶向尿素酶(L- DOS47，Helix Biophma)。这会将内源尿素分解成两个NH4+和一个CO2，从而使局部碱化 PH，这个试剂将是我们在拟议的研究中的主要重点。 我们将使用这些方法来检验用L-DOS47中和肿瘤酸性将 在PDAC小鼠模型中与检查点阻断相加或协同作用。我们的初步数据 支持这些假设，但在着手之前，我们的知识中有一些空白需要填补 L-DOS47联合免疫治疗的临床试验。初步数据显示，对 关卡封闭联合L-DOS47治疗Panc02肿瘤的研究 我们计划在目前的工作中将其扩展到更多与生物医学相关的模型。这些问题将得到解决 在3个目标中：目标1将使用分子成像技术确定这些药物的原位药效学(PD)。 1.1)pH和1.2)酶活，以优化给药方案以实现酸中和。在目标2中， 我们将把这些药物与检查点阻断(抗PD1和抗PD-L1)结合起来，以改善对 表达CEACAM6的PDAC小鼠模型(Panc02，UN-KPC960/961)。次要端点 这一目标将是开发反应的成像生物标记物，可以在治疗前使用来预测，以及 在治疗过程中进行监测、反应。目标3将解决一个基本问题，即酸性pH值如何 导致T细胞停滞。初步数据表明，苯丙氨酸的酸化导致了一种微妙而又重要的 Phi的下降，这可能是随后T细胞停滞的原因。我们还将调查是否有一个 钙信号动力学的破坏，导致NFAT分布的改变，以及是否存在差异 T细胞对酸中毒的敏感性，与酸适应或酸天真的癌细胞和成纤维细胞相比。 在这项研究完成后，我们将开发出一种临床上可翻译的方法来改善IT PDAC以及对酸抑制潜在机制的更好的理解。

Abstract Pancreatic Ductal Adenocarcinoma (PDAC) is the most lethal of all cancers and is largely resistant to all therapies, including immune therapies (IT). Despite this resistance, there are no fewer than 12 open clinical trials investigating treatment of PDAC with checkpoint blockade IT. There are multiple mechanisms that can account for this resistance, including the acidosis of PDAC tumors, which is due to high rates of glycolysis in combination with poor perfusion. Placement of activated T cells in acidic conditions profoundly inhibits their effector functions. We have shown that neutralization of tumor acidosis with oral NaHCO3 in murine models of PDAC can lead to dramatic improvements in response to checkpoint blockade. However, phase I/IIa clinical trials with bicarbonate failed to dose escalate. Thus, there is a compelling need to develop clinically viable alternatives to achieve the same result, viz. neutralization of tumor acidity in vivo in order to combine with IT. A therapy designed to directly neutralize tumor acidity is a clinically-tested CEACAM6-targeted urease (L- DOS47, Helix Biopharma). This cleaves endogenous urea into two NH4+ and one CO2, thus alkalinizing local pH, and this agent will be our primary focus in the proposed studies. We will use these approaches to test the hypothesis that neutralizing tumor acidity with L-DOS47 will be additive or synergistic with checkpoint blockade in mouse models of PDAC. Our preliminary data support these hypotheses, yet there are gaps in our knowledge that need to be filled prior to embarking on clinical trials combining L-DOS47 with immune therapy. Preliminary data have shown improved response to checkpoint blockade in combination with L-DOS47 in Panc02 tumors; an immune competent model of PDAC, and we plan to expand this to more biomedically relevant models in the current work. These will be addressed in 3 Aims: Aim 1 will determine the in situ pharmacodynamics (PD) of these agents using molecular imaging of 1.1) pH and 1.2) enzyme activity in order to optimize dosing schema to achieve acid neutralization. In Aim 2, we will combine these agents with checkpoint blockade (anti-PD1 and anti-PD-L1) to improve tumor control in mouse models of PDAC engineered to express CEACAM6 (Panc02, UN-KPC960/961). A secondary endpoint in this aim will be to develop imaging biomarkers of response that can be used prior to therapy to predict, and during therapy to monitor, response. Aim 3 will address the fundamental question of HOW an acidic pH induces T cell stasis. Preliminary data have shown that acidification of pHe induces a subtle, yet significant, drop in pHi, which may be responsible for subsequent T-cell stasis. We will also investigate whether there is a disruption of Ca2+ signaling dynamics, leading to altered NFAT distribution, and whether there is a differential sensitivity of T-cells to acidosis, compared with acid-adapted or acid-naïve cancer cells and fibroblasts. At the completion of this study, we will have developed a clinically translatable approach to improve IT in PDAC as well as an improved understanding of the mechanism underlying acid inhibition.