The thrombospondin1-TGF-beta axis in multiple myeloma

描述(申请人提供)：多发性骨髓瘤(MM)是一种无法治愈的浆细胞癌，依赖于骨髓微环境进行进展。转化生长因子-β是一种多功能的生长因子，由多发性骨髓瘤细胞和骨髓微环境中的细胞合成。转化生长因子通过促进分解代谢性骨重建、IL-6分泌和Th17T细胞发育促进多发性骨髓瘤进展，导致溶骨性骨病和免疫失调。尽管转化生长因子受体在多发性骨髓瘤中具有重要作用，但目前尚无用于治疗多发性骨髓瘤的转化生长因子受体拮抗剂的临床试验。大多数转化生长因子受体拮抗剂主要针对配体、受体或下游的激酶，它们可以拮抗转化生长因子β的稳态水平，并增加不良事件的风险。我们开发了一种新的方法，通过仅靶向通过与细胞外基质蛋白凝血酶敏感蛋白1(TSP1)结合而激活的转化生长因子-伯，选择性地靶向多发性骨髓瘤骨髓微环境中与疾病相关的转化生长因子-β活性。TSP1是一种分泌型和细胞外基质蛋白，它控制 通过结合和激活潜伏的转化生长因子，在疾病中发挥转化生长因子的活性。我们的研究表明，TSP1在MM中增加，TSP1在体外激活人和小鼠MM细胞表达的潜在的转化生长因子-伯，重要的是，依赖TSP1激活的四肽拮抗剂(LSKL)减少MM小鼠模型中的MM肿瘤负担、间质IL-6和溶骨性疾病，LSKL几乎完全阻断治疗MM小鼠骨髓细胞中活性的转化生长因子-伯，表明TSP1-转化生长因子拮抗剂多肽通过靶向骨髓微环境中依赖TSP1的转化生长因子-伯激活发挥作用。这些数据表明，TSP1是多发性骨髓瘤中转化生长因子β活性的重要调节因子，并表明阻断这一途径代表了一种新的选择性治疗策略，可以减少多发性骨髓瘤的进展和骨病。我们的目标是开发一种治疗MM的LSKL多肽的口服可用形式。我们已经鉴定了一种基于LSKL的先导化合物(SRI31277)，它在MM小鼠模型中具有剂量依赖的体内活性，改善了药代动力学和口服生物利用度，这将成为鉴定和优化先导药物的基础。这项建议将结合机制研究(目标1)和药物开发努力(目标2)，以实现我们的目标，确定一种口服活性铅化合物治疗MM。在目标1，我们将进一步确定TSP1-转化生长因子(TSP1)途径在多发性骨髓瘤中的作用，通过使用免疫活性和TSP1缺失模型，通过比较SRI31277和全局转化生长因子(TSP1)抑制剂并在药物组合中使用，以及通过补充性体外研究来确定MM细胞上TSP1受体的转化生长因子活化以及这一途径在MM细胞细胞因子产生和成骨/破骨细胞调节中的作用。目标2的主要目标是确定SRI31277的口服活性衍生物和适用于GLP-IND研究的备用多肽模拟物/小分子，从而能够使用多肽和模拟多肽/小分子方法进行研究。

DESCRIPTION (provided by applicant): Multiple myeloma (MM) is an incurable cancer of plasma cells that is dependent on the bone marrow microenvironment for progression. Transforming growth factor-beta (TGF-ß) is a multi-functional growth factor elaborated by MM cells and by cells in the bone marrow microenvironment. TGF-ß stimulates MM progression through promotion of catabolic bone remodeling, IL-6 secretion, and Th17 T cell development, leading to osteolytic bone disease and immune dysregulation. Despite the importance of TGF-ß in MM, there are no clinical trials of TGF-ß antagonists for the treatment of MM. Most TGF-ß antagonists broadly target the ligand, receptors, or downstream kinases, which can antagonize homeostatic levels of TGF-ß and increase the risk of adverse events. We have developed a novel approach to selectively targeting disease-related TGF-ß activity in the MM bone marrow microenvironment through targeting only the TGF-ß which is activated through binding to the extracellular matrix protein, thrombospondin1 (TSP1). TSP1 is a secreted and extracellular matrix protein, which controls TGF-ß activity in disease by binding and activating latent TGF-ß. TSP1 is increased in MM. Our studies show that TSP1 activates latent TGF-ß expressed by human and mouse MM cells in vitro and importantly, a tetrapeptide antagonist (LSKL) of TSP1-dependent TGF-ß activation reduces MM tumor burden, stromal IL-6, and osteolytic bone disease in mouse models of MM. LSKL nearly completely blocks active TGF-ß in bone marrow cells of treated MM mice, indicating that the TSP1-TGF-ß antagonist peptide is working through targeting TSP1-dependent TGF-ß activation in the bone marrow microenvironment. These data establish that TSP1 is an important regulator of TGF-ß activity in MM and suggest that blockade of this pathway represents a novel and selective therapeutic strategy to reduce MM progression and bone disease. Our goal is to develop an orally available, "druggable" form of the LSKL peptide for treatment of MM. We have identified a lead compound (SRI31277) based on LSKL which has dose-dependent in vivo activity in a mouse model of MM, improved pharmacokinetics and oral bioavailability, and which will be the basis for identification and optimization of lead drugs. This proposal will combine mechanistic studies (Aim 1) with drug development efforts (Aim 2) to achieve our goal of identifying an orally active lead compound for treatment of MM. In Aim 1, we will further determine the role of the TSP1-TGF-ß pathway in MM through use of immune competent and TSP1 null models, by comparison of SRI31277 to global TGF-ß inhibitors and by use in drug combinations, and by complementary in vitro studies to define the TSP1 receptor on MM cells for TGF-ß activation and the role of this pathway in MM cell cytokine production and osteoblast/osteoclast regulation. The key goal of Aim 2 is to identify an orally active derivative of SRI31277 and a back-up peptide mimetic/small molecule suitable for GLP-IND enabling studies using both peptide and peptidomimetic/small molecule approaches.