Inhibition of the tumor-promoting effects of TGF-beta in advanced prostate cancer

描述（由申请人提供）：转化生长因子β亚型（TGFβ1、β2和β3）是分泌型信号蛋白。它们在正常和早期肿瘤细胞中作为免疫调节因子和肿瘤抑制因子发挥作用，但在许多已建立的癌症中，包括雄激素非依赖性前列腺癌，它们促进肿瘤生长和转移。使用中和抗体和小分子受体激酶抑制剂拮抗TGFβ的治疗益处已在癌症动物模型中得到充分证明，但尚未批准抑制剂用于人类癌症治疗。激酶抑制剂LY 2157299具有显着的脱靶活性，由于安全性，在临床试验中进展缓慢 性问题泛同种型中和抗体GC 1008虽然具有特异性和安全性，但效力有限。后者可能是由于i）抗体的有限亲和力（Kd 4-10 nM），其阻碍其与内源性受体复合物竞争的能力，所述内源性受体复合物是以0.1-1 pM的亲和力结合TGFβ的异源四聚体，ii）需要两种抗体结合同二聚体TGFβ以完全阻断受体结合，或iii）抗体的大尺寸（160 kDa）和/或与Fc受体的结合限制了其穿透肿瘤和微环境的能力。本研究的目的是研究一类有前途的新的TGFβ抑制剂，其中TGFβ受体的配体结合结构域通过柔性接头融合在一起。这些融合的优点包括i）潜在的更高亲和力，ii）用单一抑制剂阻断所有受体结合位点，和iii）减小的大小（24-91 kDa）。通过初步研究，产生了四种融合体。这些药物在体外有效抑制TGFβ活性（EC 50 2 nM-1 pM），并在几种模型（包括人前列腺癌异种移植模型）中高度有效地抑制原发性肿瘤生长和远处转移。目的1的目的是产生一系列不同亲和力的受体融合物，受体结合位点的阻断和大小-这将使我们能够研究我们的假设，即这些参数决定治疗效果。还将在目标1中评价融合物的PK特性。目的2的主要目的是评价融合物对免疫活性背景下自发性前列腺癌发生的两种遗传小鼠模型和免疫受损背景下人前列腺癌异种移植模型中主要器官原发性肿瘤生长以及转移性集落数量和大小的抑制作用。为了更好地理解抑制剂如何影响治疗效果，我们将研究它们的PD特性及其对TGFβ调节的免疫抑制、血管生成和EMT的影响。目的2的次要目的是确定融合物是否干扰免疫活性小鼠中TGFβ的肿瘤抑制和/或免疫调节功能-这将提供关于在不干扰其在正常细胞和组织中的功能的情况下如何积极地抑制TGFβ的信息。长期目标是生产用于中和TGFβ促肿瘤活性的融合物，这些融合物安全有效地用于晚期前列腺癌的临床试验。

DESCRIPTION (provided by applicant): Transforming growth factor-beta isoforms (TGFβ1, β2, and β3) are secreted signaling proteins. They function as immunomodulatory factors and tumor suppressors in normal and early neoplastic cells, but in many established cancers, including androgen-independent prostate cancer, they promote tumor growth and metastasis. The therapeutic benefit of antagonizing TGFβ using neutralizing antibodies and small molecule receptor kinase inhibitors has been amply demonstrated in animal models of cancer, yet no inhibitors have been approved for cancer treatment in humans. The kinase inhibitor LY2157299 has significant off-target activity and has progressed slowly through clinical trials due to safety concerns. The pan-isoform neutralizing antibody GC1008, while specific and safe, has limited efficacy. The latter may be due to i) the limited affinity of the antibody (Kd 4-10 nM) that hinder its ability to compete against the endogenous receptor complex, a heterotetramer that binds the TGFβs with affinities of 0.1-1 pM, ii) a requirement that two antibodies bind to homodimeric TGFβ to completely block receptor binding, or iii) the large size of the antibody (160 kDa) and/or binding to Fc receptors that restricts its ability to penetrate the tumor and microenvironment. The objective of this study is to investigate a promising new class of TGFβ inhibitors in which the ligand-binding domains of the TGFβ receptors are fused together by flexible linkers. The advantages of these fusions include i) potentially higher affinities, ii) blockage of all receptor binding sites with a single inhibitor, and iii) reduced size (24-91 kDa). Through preliminary studies, four fusions have been generated. These potently inhibit TGFβ activity in vitro (EC50 2 nM -1 pM) and are highly effective in suppressing primary tumor growth and distant metastases in several models, including a xenograft model of human prostate cancer. The objective of Aim 1 is to generate a series of receptor fusions of varying affinity, blockage of receptor binding sites, and size - this will allow us to investigate our hypothesis tha these parameters determine therapeutic efficacy. The PK properties of the fusions will also be evaluated in Aim 1. The primary objective of Aim 2 is to evaluate the inhibitory effect of the fusions on primary tumor growth and number and size of metastatic colonies to the major organs in two genetic mouse models with spontaneous prostate carcinogenesis in an immune-competent background and a xenograft model of human prostate cancer in an immune compromised background. To better understand how the inhibitors influence therapeutic efficacy, we will investigate their PD properties and their effects on TGFβ - regulated immune suppression, angiogenesis, and EMT. The secondary objective of Aim 2 is to determine whether the fusions interfere with TGFβ's tumor suppressive and/or immune modulatory functions in immune competent mice - this will provide information as to how aggressively TGFβ can be inhibited without interfering with its function in normal cells and tissues. The long-term goal is o produce fusions for neutralizing TGFβ's tumor promoting activity that are both safe and effective for use in clinical trials for advanced prostate cancer.