Phosphatase activation as therapeutic strategy for Chronic lymphocyic leukemia

 描述(申请人提供)：尽管随着慢性淋巴细胞白血病(CLL)新疗法的引入，无进展生存期延长，但目前可用的疗法并不是对所有患者都有效，复发的患者通常反应较差。识别对耐药患者有效的新药物是调查的主要重点。在慢性淋巴细胞性白血病和其他癌症中，与延长生存期和有缺陷的细胞凋亡相关的蛋白质的结构性磷酸化是一个反复出现的主题。在积极寻求抑制蛋白磷酸酶的同时，对蛋白磷酸酶的药理学激活的研究较少，代表着对CLL中异常磷酸化蛋白的潜在治疗调节的范式转变。我们已经确定了FDA批准的免疫抑制剂FTY720可以通过蛋白磷酸酶2A(PP2A)激活依赖的机制在CLL中介导细胞毒性。尽管FTY720对包括CLL、套细胞淋巴瘤、慢性髓系白血病和急性淋巴细胞白血病在内的多种血红素恶性肿瘤具有较强的临床前活性，但其免疫抑制特性阻碍了其在血红素恶性肿瘤的临床应用上的进一步发展。因此，我们开发了一种非免疫抑制的FTY720衍生物，OSU-2S，具有很强的细胞毒活性。这项建议将寻求OSU-2S在B细胞恶性肿瘤中的机制、药理学和翻译发展。具体地说，在目标1中，我们建议确定OSU-2S的直接靶点，并确定OSU-2S诱导CLL细胞凋亡的机制基础，重点是CLL中的磷酸酶。为了克服OSU-2S在体内潜在的脱靶效应，我们制备了CLL肿瘤抗原(ROR1)靶向免疫脂质体制剂(2A2-OSU-2S-ILP)和在白血病B细胞上表达人ROR1抗原的CLL小鼠模型。在目标2中，我们建议通过a)确定2a2-OSU-2S-ILP在人ROR1+TCL1 CLL小鼠中的最大耐受剂量和暴露；b)表征2a2-OSU-2S-ILP在E-ROR1-TCL1小鼠骨髓、脾、循环WBC和其他组织中的药代动力学和药效学(PK/PD)调节之间的体内关系，以及c)使用PK/PD建模和模拟来设计2a2-OSU-2S-ILP的最佳剂量方案，以最大限度地诱导pSHP1的诱导，同时最小化非病变组织中的OSU-2S暴露。在目标3中，我们将在我们的人ROR1+CLL小鼠模型中验证人ROR1靶向OSU-2S制剂的体内治疗效果。在这个项目完成时，我们将产生足够的OSU-2S机制和药理学数据，证明其过渡到CLL的早期临床试验是合理的。我们准备通过我们的专利OSU-2S、新颖的CLL靶向给药配方和专门开发的独特动物模型来实现这一点，以满足我们进行全面临床前评估的需求。为了实现这一目标，我们组建了一支高度互动的团队，拥有蛋白质组学、转化医学、药物开发、小鼠建模、药物输送以及PK/PD建模和模拟方面的专业知识。

 DESCRIPTION (provided by applicant): Despite prolonged progression free survival with the introduction of novel therapies for Chronic lymphocytic leukemia (CLL) currently available therapies are not curative in all patients and patients who relapse generally respond poorly. Identification of new agents that work in resistant patients represents a major focus of investigation. Constitutive phosphorylation of proteins associated with prolonged survival and defective apoptosis is a recurrent theme in CLL and other cancers. While inhibition of kinases is actively pursued, pharmacological activation of protein phosphatases is less explored and represents a paradigm shift for potential therapeutic modulation of aberrantly phosphorylated proteins in CLL. We have identified FTY720, an FDA approved immunosuppressant, to mediate cytotoxicity through a protein phosphatase 2A (PP2A) activation dependent mechanism in CLL. Despite its potent pre-clinical activity in multiple heme-malignancies including CLL, mantle cell lymphoma, chronic myeloid leukemia and acute lymphoid leukemia, the immunosuppressive property of FTY720 precluded its further development for clinical application in heme-malignancies. We therefore developed a non-immunosuppressive FTY720 derivative, OSU-2S, with potent cytotoxic activity. This proposal will pursue mechanistic, pharmacological and translational development of OSU-2S in B cell malignancies. Specifically, in Aim 1 we propose to identify the direct target of OSU-2S and determine the mechanistic basis of OSU-2S induced apoptosis with emphasis on phosphatases in CLL. To overcome potential off target effects of OSU-2S in-vivo, we generated CLL tumor antigen (ROR1) targeted immunoliposomal delivery formulations (2A2-OSU-2S-ILP) and CLL mouse models expressing human ROR1 antigen on leukemic B cells. In Aim 2, we propose to maximize the therapeutic index of 2A2-OSU-2S-ILP by a) determining maximum tolerable doses and exposures of 2A2-OSU-2S-ILP in human ROR1+Tcl1 CLL mice; b) characterizing the in-vivo relationships between 2A2-OSU-2S-ILP pharmacokinetics and pharmacodynamic (PK/PD) modulation of pSHP1 in bone marrow, spleen, circulating WBCs and other tissues in Eµ-ROR1-Tcl1 mice, and c) using PK/PD modeling and simulation to design optimal dose regimens of 2A2-OSU-2S-ILP that maximize pSHP1 induction while minimizing dose levels and OSU-2S exposure in non-diseased tissues. We will validate the in-vivo therapeutic efficacy of the human ROR1 targeted OSU-2S formulations in our human ROR1+ CLL mouse model in Aim 3. At completion of this project we will have generated sufficient mechanistic and pharmacological data with OSU-2S to justify its transition to early clinical trials for CLL. We are poised to accomplish this through our patented OSU-2S, novel CLL targeted delivery formulation and unique animal models exclusively developed to meet our needs to perform a comprehensive pre-clinical evaluation. To accomplish this goal we have assembled a highly interactive team with expertise in proteomics, translational medicine, drug development, mouse modeling, drug delivery, and PK/PD modeling and simulation.