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，并且对所有肿瘤都有很大的耐药性。 免疫疗法（Immune Therapy，IT）尽管有这种阻力，有不少于12个开放的临床 研究检查点阻断IT治疗PDAC的试验。有多种机制可以 解释了这种耐药性，包括PDAC肿瘤的酸中毒，这是由于糖酵解的高速率， 同时伴有灌注不良。将活化的T细胞置于酸性条件下， 效应器功能。我们已经证明，在小鼠肿瘤模型中，口服NaHCO 3中和肿瘤酸中毒， PDAC可以显著改善对检查点封锁的响应。然而，I/IIa期临床试验 使用碳酸氢盐的试验未能增加剂量。因此，迫切需要开发临床上可行的 实现相同结果的替代方案，即在体内中和肿瘤酸性以与IT联合收割机结合。 设计用于直接中和肿瘤酸性的疗法是临床测试的CEACAM 6靶向尿素酶（L- D0S47，Hubiffiirma）。这将内源性尿素分解成两个NH 4+和一个CO2，从而使局部碱化。 pH值，该试剂将是我们在拟议研究中的主要关注点。 我们将使用这些方法来检验用L-DOS 47中和肿瘤酸性将 与PDAC小鼠模型中的检查点阻断是相加的或协同的。我们的初步数据 支持这些假设，但在我们的知识中存在空白，需要在开始之前填补 L-DOS 47与免疫疗法相结合的临床试验。初步数据显示， 在Panc 02肿瘤中与L-DOS 47组合的检查点阻断; PDAC的免疫活性模型， 我们计划在目前的工作中将其扩展到更多的生物医学相关模型。这些问题将得到解决 在3个目标中：目标1将使用分子成像确定这些药物的原位药效学（PD）， 1.1)pH和1.2）酶活性，以便优化给药方案以实现酸中和。在目标2中， 我们将联合收割机将这些药物与检查点阻断剂（抗PD 1和抗PD-L 1）结合起来，以改善肿瘤控制 经工程改造以表达CEACAM 6的PDAC小鼠模型（Panc 02，UN-KPC 960/961）。次要终点 本发明的目的是开发反应的成像生物标志物，其可以在治疗前用于预测， 在治疗过程中监测反应。目标3将解决一个基本问题，即酸性pH值 诱导T细胞停滞。初步数据表明，pH的酸化诱导了一种微妙但重要的， pHi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 Ca 2+信号动力学的破坏，导致NFAT分布改变，以及是否存在差异 T细胞对酸中毒的敏感性，与酸适应或酸未处理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，以改善IT， PDAC以及对酸抑制机制的更好理解。

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.