Therapy of pancreatic cancer with 212Pb-labeled B7-H3 specific Ab and LDE225

描述（由申请人提供）：由于迫切需要开发新的有效治疗胰腺腺癌（PDAC）的方法，本提案将验证一个新的假设，即212pb标记的基于单克隆抗体的放射免疫疗法（RIT）靶向PDAC细胞上选择性表达的B7-H3表位，将增强吉西他滨和Sonic hedgehog （SHH）抑制剂LDE225根除PDAC的能力，不仅消除分化的PDAC细胞，而且消除胰腺癌启动细胞（CICs）。我们计划优化的联合策略利用了mAb 376.96的独特特异性。该单抗识别共抑制分子B7-H3的细胞外表位，该表位在人PDAC细胞系和手术切除的PDAC病变（包括胰腺CICs）中表达，但在正常组织中分布有限。该提案将验证PDAC可以被根除的假设，通过将212Pb偶联到新的mAb 376.96上，不仅可以靶向分化/分化的胰腺癌细胞（构成肿瘤的大部分），还可以靶向疾病的根源胰腺CICs。这一假设源于癌症干细胞理论，该理论认为必须消除CICs才能“治愈”恶性疾病，因为CICs是导致疾病复发和转移性扩散的原因。我们的初步结果支持了我们联合策略的有效性：如图4、5和6所示，mAb 376.96增强了吉西他滨的抗增殖活性和消除CICs的能力。吉西他滨目前是PDAC的标准化疗药物。然而，单独使用吉西他滨的效果有限，大多数患者对治疗产生耐药性。这种耐药性可能反映了CICs的化学耐药性。212Pb的靶向RIT会衰变成212Bi，将与吉西他滨和SHH通路抑制剂LDE225联合使用，因为该抑制剂已被证明可有效降低胰腺CICs。本提案的具体目的是测试：i.标记212Pb的b7 - h3特异性mAb 376.96是否与人PDAC细胞系结合，并单独或联合吉西他滨和LDE225抑制人胰腺CIC肿瘤球的体外增殖。2。212Pb标记的b7 - h3特异性mAb 376.96与吉西他滨和LDE225联合使用，可以根除移植了人类PDAC细胞的免疫缺陷小鼠的原位疾病，因为这种联合不仅消除了分化的PDAC细胞，还消除了胰腺CICs。3。212Pb标记的b7 - h3特异性mAb 376.96与吉西他滨和LDE225联合使用，可根除移植了人PDAC细胞的免疫缺陷小鼠的微转移性疾病。从上述研究中获得的信息将为拟议的212Pb-376.96抗体和CIC治疗胰腺癌的临床转化提供坚实的基础。

DESCRIPTION (provided by applicant): Because of the urgent need to develop novel effective therapies for pancreatic adenocarcinoma (PDAC), this proposal will test the novel hypothesis that a 212Pb-labeled mAb-based radioimmunotherapy (RIT) targeting a B7-H3 epitope selectively expressed on PDAC cells will enhance the ability of gemcitabine and the Sonic hedgehog (SHH) inhibitor LDE225 to eradicate PDAC, by eliminating not only differentiated PDAC cells, but also pancreatic cancer initiating cells (CICs). The combination strategy we plan to optimize takes advantage of the unique specificity of mAb 376.96. This mAb recognizes an extracellular epitope of the coinhibitory molecule B7-H3 which is expressed on human PDAC cell lines and in surgically removed PDAC lesions, including pancreatic CICs, but has a restricted distribution in normal tissues. This proposal will test the hypothesis that PDAC can be eradicated by targeting not only differentiated/differentiating pancreatic cancer cells, which form the bulk of the tumor, but also pancreatic CICs, the root of the disease, with 212Pb conjugated to the novel mAb 376.96. This hypothesis stems from the cancer stem cell theory which postulates that CICs have to be eliminated to "cure" a malignant disease, since CICs are responsible for disease recurrence and metastatic spread. The validity of our combination strategy is supported by our preliminary results: as shown in Figs. 4, 5, and 6 mAb 376.96 enhances the anti-proliferative activity of gemcitabine and its ability to eliminate CICs. Gemcitabine is currently the standard chemotherapeutic agent for PDAC. However, the effect of gemcitabine alone is limited and most patients develop resistance to the therapy. This resistance may reflect the chemo-resistance of CICs. Targeted RIT with 212Pb, which decays to 212Bi, will be combined with gemcitabine and LDE225, an inhibitor of the SHH pathway, since this inhibitor has been shown to be effective in reducing pancreatic CICs. The specific aims of this proposal will test whether: i. B7-H3-specific mAb 376.96 labeled with 212Pb binds to human PDAC cell lines and inhibits in vitro proliferation of human pancreatic CIC tumorspheres alone or in combination with gemcitabine and LDE225. ii. B7-H3-specific mAb 376.96 labeled with 212Pb, in combination with gemcitabine and LDE225 eradicates orthotopic disease in immunodeficient mice grafted with human PDAC cells, since this combination eliminates not only differentiated PDAC cells, but also pancreatic CICs. iii. B7-H3-specific mAb 376.96 labeled with 212Pb, in combination with gemcitabine and LDE225, eradicates micrometastatic disease in immunodeficient mice grafted with human PDAC cells. The information derived from the outlined studies will provide a solid foundation for clinical translation of the proposed 212Pb-376.96 antibody and CIC therapy to treat pancreatic cancer.