Development of a Novel Immunotherapy Platform for Triple-Negative Breast Cancer

三阴性乳腺癌（TNBC）占所有乳腺癌诊断的15-20%，是最常见的乳腺癌。 该疾病的侵袭性形式，并且具有最差的临床结果。化疗是主要的治疗方法 尽管存在显著的治疗相关毒性和短期临床反应，因此，我们认为， 需要更有效和更好耐受的TNBC治疗方式。免疫检查点 阻断（ICB）是一种基于免疫疗法的方法，可以在晚期患者中恢复持久的免疫力。 比如黑色素瘤和肺癌。对于其他癌症类型，如乳腺癌，FDA批准 2019年3月，TNBC的第一种免疫疗法。该方案包括α-PD-L1抗体（Tecentriq）加 Abraxane（白蛋白结合型紫杉醇）作为不可切除的局部晚期或转移性乳腺癌患者的一线治疗 PD-L1+ TNBC。不幸的是，总体反应率仍然相对较低，生存期延长 在很大程度上是由于免疫抑制性多形性骨髓源性 抑制细胞（PMN-MDSC），其有效地抑制抗肿瘤免疫。因此，制定战略， 降低PMN-MDSC活性可提高TNBC对α-PD-L1/Abraxane的应答率。一种减少 基于骨髓的免疫抑制机制是通过调节控制免疫的信号通路来实现的。 抑制促进刺激的基因，这就是所谓的重编程。Toll样受体（TLR）5 信号转导既可以降低MDSC活性，又可以刺激针对多种临床前肿瘤的抗肿瘤免疫 模型，包括PD-L1+ TNBC。因此，我们认为TLR 5激动剂是一类新的药物，可以介导， 骨髓重编程在PD-L1+ TNBC中具有潜在的体内治疗功效。为此，我们设计了 和优化的恩托莫德，一种天然TLR 5激动剂沙门氏菌鞭毛蛋白的衍生物。 重要的是，三项I期安全性试验累积涉及近200名受试者，表明系统性 使用恩托莫德是安全的。我们最近的研究表明，恩托莫德通过以下方式抑制转移性PD-L1+ TNBC： 刺激持久的CD 8 + T细胞免疫。在这里，我们表明，entolimod驱动的PMN-MDSC重编程 控制恩托莫德在PD-L1+ TNBC中的抗转移活性。这些发现为我们的研究提供了理论基础。 其他研究表明，联合使用恩托莫德与α-PD-L1/Paclitaxel可引发早期 小鼠PD-L1+ TNBC并诱导持久免疫。然而，恩托莫德是否能增强抗肿瘤作用， α-PD-L1/Abraxane在局部晚期和转移性PD的新辅助和/或辅助治疗中的活性- L1+ TNBC，这种疗法是FDA批准的，仍然是未知的，以及是否恩托莫德改变了TNBC。 PMN-MDSC反应作为其作用机制的一部分。为了检验我们的中心假设，我们提出了两个目标： (1)确定最有效的TNBC治疗平台和疾病背景， α-PD-L1/Abraxane的有效性;（2）阐明PMN-MDSC对该机制的贡献， 其中恩托莫德促进α-PD-L1/Abraxane在TNBC中的抗肿瘤功效。

Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer diagnoses, is the most aggressive form of the disease, and has the poorest clinical outcome. Chemotherapy is the mainstay treatment for these patients despite significant treatment-related toxicities and short-term clinical responses. Therefore, the need for more effective and better tolerated treatment modalities for TNBC is warranted. Immune checkpoint blockade (ICB) is an immunotherapy-based approach that can reinvigorate durable immunity in advanced cancers such as melanoma and lung. In the case of other cancer types, such as breast cancer, the FDA approved the first immunotherapy for TNBC in March 2019. This regimen consists of α-PD-L1 antibody (Tecentriq) plus Abraxane (Nab-paclitaxel) as a frontline therapy for patients with unresectable locally advanced or metastatic PD-L1+ TNBC. Unfortunately, overall response rates remain relatively low and survival outcomes are extended for only a few months due in large part to expansion of immunosuppressive polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) that potently suppress antitumor immunity. Thus, developing strategies to reduce PMN-MDSC activity may improve response rates to α-PD-L1/Abraxane in TNBC. One approach to lessen myeloid-based mechanisms of immune suppression is by modulating signaling pathways that govern immune suppression to those that promote stimulation in a concept known as reprogramming. Toll-like receptor (TLR) 5 signaling can both mitigate MDSC activity and stimulate antitumor immunity against multiple pre-clinical tumor models, including PD-L1+ TNBC. Thus, we posit that TLR5 agonists are a novel class of agents that can mediate myeloid reprogramming with potential in vivo therapeutic efficacy in PD-L1+ TNBC. To this end, we engineered and pharmacologically optimized entolimod, a derivative of the natural TLR5 agonist Salmonella flagellin. Importantly, three Phase I safety trials cumulatively involving nearly 200 subjects showed that systemically administered entolimod is safe. Our recent work showed that entolimod suppresses metastatic PD-L1+ TNBC by stimulating durable CD8+ T cell immunity. Here, we show that entolimod-driven PMN-MDSC reprogramming governs the anti-metastatic activity of entolimod in PD-L1+ TNBC. These findings provided the rationale for our additional studies showing that combining entolimod with α-PD-L1/Paclitaxel triggers regression of early-stage mouse PD-L1+ TNBC and induces durable immunity. However, whether entolimod enhances the antitumor activity of α-PD-L1/Abraxane in locally advanced and the neoadjuvant and/or adjuvant setting of metastatic PD- L1+ TNBC, for which this therapy is FDA approved, remains unknown, as well as whether entolimod alters the PMN-MDSC response as part of its mechanism of action. To test our central hypothesis, we propose two aims: (1) to determine the most effective TNBC treatment platform and disease setting by which entolimod bolsters the efficacy of α-PD-L1/Abraxane; and (2) to elucidate the contribution of PMN-MDSCs to the mechanism by which entolimod promotes the antitumor efficacy of α-PD-L1/Abraxane in TNBC.