Tumor-toxic CD47 mAb therapy for leukemia: a proof of concept study

肿瘤毒性 CD47 mAb 治疗白血病：概念验证研究

• 批准号: 8520948
• 负责人: WILLIAM A FRAZIER
• 金额: $ 29.97万
• 依托单位: VASCULOX, INC.
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-17 至 2015-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8520948
• 关键词: Acute Promyelocytic Leukemia; Adverse effects; Antineoplastic Agents; Binding; CD47 gene; Cell Death; Cell Surface Receptors; Cell surface; Cells; Clinical Trials; Colon Carcinoma; Complement; Cytolysis; Data; Dendritic Cells; Detection; Diagnosis; Eating; Fluorescence; Green Fluorescent Proteins; Hematologic Neoplasms; Human; Image; Immune; In Vitro; Knockout Mice; Leukocytes; Luciferases; MS4A1 gene; Malignant Neoplasms; Malignant neoplasm of brain; Malignant neoplasm of prostate; Mediating; Medical; Membrane Potentials; Mitochondria; Modeling; Monoclonal Antibodies; Mus; Natural Killer Cells; Non-Hodgkin' s Lymphoma; Normal Cell; PTPNS1 gene; Patients; Phagocytosis; Phase; Phosphatidylserines; Publishing; Quality of life; Reporting; Rest; Safety; Series; Signal Transduction; Solid Neoplasm; Survival Rate; T-Cell Leukemia; T-Lymphocyte; Testing; Tissues; Toxic effect; Tumor Burden; War; Xenograft procedure; cancer cell; cancer therapy; cell transformation; cytotoxic; cytotoxicity; efficacy testing; improved; in vivo; in vivo Model; killings; leukemia; macrophage; malignant breast neoplasm; mouse model; neoplastic cell; new therapeutic target; outcome forecast; prevent; programs; public health relevance; receptor; rituximab; tumor; tumor xenograft; uptake

DESCRIPTION (provided by applicant): CD47 has emerged as a novel therapeutic target in hematologic cancers. Leukemias expressing the highest levels of CD47 have the worst prognosis. Increased CD47 expression is thought to protect cancer cells from phagocytic clearance by sending a "don't eat me" signal to macrophages via SIRPa, an inhibitory receptor that prevents phagocytosis of CD47-bearing cells. Anti-CD47 mAbs (CD47mAbs) that block the CD47/SIRPa interaction enhance phagocytosis of cancer cells and contribute to control of tumor burden in human to mouse xenograft leukemia models (). However, there are mechanisms by which CD47 mAbs can attack transformed cells that have not yet been exploited in the war on cancer. A particular anti-human CD47mAb (clone 1F7) has a direct, cytotoxic effect on human leukemias. MAb 1F7 kills CD47-bearing tumor cells without the action of complement or other immune cells. Instead, mAb 1F7 acts via a non-apoptotic mechanism that involves a direct CD47-dependent attack on mitochondria, discharging their membrane potential (DYm) and destroying the ATP-generating capacity of the cell leading to rapid cell death. It is noteworthy that mAb 1F7 does not kill normal leukocytes, which also express CD47, but only those cells that are "activated" by transformation. Thus normal circulating cells, all of which express CD47, are spared while cancer cells are selectively killed by the tumor-toxic CD47mAb. Importantly, mAb 1F7 also blocks binding of SIRPa to CD47 and thus it can act via two mechanisms: (1) direct tumor cytotoxicity and (2) promoting phagocytosis of the dead and dying tumor cells. We hypothesize that a single mAb that can accomplish both functions will be superior to one that only blocks CD47/SIRPa binding. In this phase I project, we will characterize CD47mAbs with tumor-toxic activity toward mouse leukemia cells and then test these mAbs for efficacy in treating mouse acute promyelocytic leukemias (APL). In phase II of this program, we will humanize our candidate CD47mAb and evaluate its efficacy and safety. The PHASE I SPECIFIC AIMS are: 1. Identification/characterization of a tumor-toxic CD47mAb selected from a panel of CD47 mAbs (series 400 mAbs) that react with CD47 from many species including mouse and human. 2. Tumor-toxic CD47mAbs identified in Aim 1 will be tested for efficacy in syngeneic mouse APL models in vivo. APL cells will be tagged with luciferase and green fluorescent protein (GFP) for sensitive detection. We will compare anti-cancer efficacy of the tumor-toxic CD47mAbs to a CD47mAb that simply blocks CD47/SIRPa binding. This study will also give us a preliminary indication of in vivo safety/tolerability of these CD47mAbs that can bind CD47 on both the leukemia and the host's normal cells, a situation reflecting human cancer therapy.

描述（由申请人提供）：CD47已成为血液学癌症的新治疗靶点。CD47表达水平最高的白血病预后最差。CD47表达的增加被认为通过SIRPa向巨噬细胞发送“不要吃我”的信号，从而保护癌细胞免受吞噬清除。SIRPa是一种抑制受体，可以阻止携带CD47细胞的吞噬。在人-小鼠异种移植白血病模型中，阻断CD47/SIRPa相互作用的抗CD47单抗（cd47mab）增强了癌细胞的吞噬作用，有助于控制肿瘤负荷（）。然而，CD47单克隆抗体攻击转化细胞的机制还没有在抗癌战争中被利用。一种特殊的抗人类CD47mAb（克隆1F7）对人类白血病具有直接的细胞毒性作用。MAb 1F7在没有补体或其他免疫细胞作用的情况下杀死携带cd47的肿瘤细胞。相反，mAb 1F7通过非凋亡机制起作用，涉及直接依赖cd47的线粒体攻击，释放其膜电位（DYm）并破坏细胞的atp生成能力，导致细胞快速死亡。值得注意的是，mAb 1F7并不会杀死同样表达CD47的正常白细胞，而只会杀死那些被转化“激活”的细胞。因此，所有表达CD47的正常循环细胞都可以幸免，而癌细胞则被肿瘤毒性CD47mAb选择性杀死。重要的是，mAb 1F7也阻断SIRPa与CD47的结合，因此它可以通过两种机制起作用：(1)直接的肿瘤细胞毒性和(2)促进死亡和垂死肿瘤细胞的吞噬。我们假设，能够完成这两种功能的单抗将优于仅阻断CD47/SIRPa结合的单抗。在这个一期项目中，我们将对cd47mab对小鼠白血病细胞具有肿瘤毒性活性进行表征，然后测试这些mab对小鼠急性早幼粒细胞白血病（APL）的疗效。在该项目的II期，我们将对候选CD47mAb进行人源化，并评估其有效性和安全性。第一阶段的具体目标是：1。从CD47单克隆抗体（400系列单克隆抗体）中选择的肿瘤毒性CD47mAb的鉴定/表征，这些单克隆抗体可与包括小鼠和人类在内的许多物种的CD47发生反应。2. 在Aim 1中鉴定出的肿瘤毒性CD47mAbs将在同基因小鼠APL模型中进行体内有效性测试。APL细胞将被荧光素酶和绿色荧光蛋白（GFP）标记以进行敏感检测。我们将比较肿瘤毒性CD47mAb与单纯阻断CD47/SIRPa结合的CD47mAb的抗癌功效。这项研究也将给我们提供这些cd47mab的体内安全性/耐受性的初步指示，这些cd47mab可以结合CD47在白血病和宿主的正常细胞上，这反映了人类癌症治疗的情况。