Novel Therapeutics Targeting HER2 Positive Breast Cancer Brain Metastasis

描述（由申请人提供）：乳腺癌脑转移发生在超过三分之一的HER 2+肿瘤转移患者中，非常难以治疗，生存率<1年。尽管乳腺癌中的异常HER 2受体过表达与脑转移高度相关，但分子靶向抗HER 2治疗（如曲妥珠单抗和拉帕替尼）无法穿过血脑屏障（BBB）到达治疗浓度的转移部位。该提案解决了将“分子靶向”抗HER 2药物拉帕替尼递送到特定转移部位-大脑的关键障碍。 我们的方法利用脑归巢肽Angiopep-2的独特性质来改善拉帕替尼穿过BBB的渗透，以治疗HER 2+脑转移。19个氨基酸的血管肽素-2结合低密度脂蛋白受体相关蛋白（LRP-1）受体，后者以比转铁蛋白高得多的BBB转胞吞效率被转胞吞入脑。本研究的目标是开发脑渗透性拉帕替尼Angiopep-2缀合物，其可以提高脑中的治疗药物水平以治疗HER 2+乳腺癌脑转移。我们假设拉帕替尼-血管肽素-2偶联物将比拉帕替尼本身更有效地穿过BBB，并导致拉帕替尼在脑转移中的更高蓄积，因此，将在靶向和破坏HER 2+乳腺癌脑转移中获得治疗益处。我们计划通过三个具体目标来测试该假设：（1）优化具有改善的溶解度、血清稳定性和实现局部拉帕替尼释放的能力的拉帕替尼-血管肽缀合物;（2）证明优化缀合物的脑渗透、细胞摄取和释放的有效性以及细胞毒性效力;（3）验证优化的缀合物在免疫缺陷小鼠中的HER 2过表达乳腺癌脑转移模型中的增强的脑积累和治疗功效。 我们将优化合成方案，通过不同的交联剂将拉帕替尼化学连接到Angiopep-2的肽骨架上。我们将研究偶联物在小鼠和人血清中的稳定性以及在HER 2过表达乳腺癌细胞中的细胞毒性。我们将使用原位小鼠脑灌注技术测定缀合物的BBB转运速率。我们将通过向裸鼠心内和颅内注射过表达脑寻求HER 2的人乳腺癌细胞，并在缀合物治疗后监测肿瘤生长和/或消退，在我们建立的乳腺癌脑转移小鼠模型中测试缀合物的功效。该项目的成功完成将确定一种拉帕替尼给药系统，该系统能够穿过血脑屏障，并对乳腺癌脑转移动物模型具有活性。如果成功，这项研究可以转化为临床，并可能在延长HER 2阳性脑转移乳腺癌患者的生命方面向前迈出重要一步。这项工作将对其他分子靶向酪氨酸激酶抑制剂（如吉非替尼和厄洛替尼，拉帕替尼的结构类似物）的递送产生更广泛的影响，用于治疗源自其他癌症的CNS转移。

DESCRIPTION (provided by applicant): Breast cancer brain metastasis, which occurs in more than one third of metastatic patients with HER2+ tumors, is extremely difficult to treat with survival rates of <1 year. Even though aberrant HER2 receptor overexpression in breast cancer is highly correlated with brain metastasis, molecularly targeted anti-HER2 therapy such as trastuzumab and lapatinib cannot cross the blood brain barrier (BBB) to reach the metastatic site at therapeutic concentrations. This proposal addresses overcoming a critical barrier to delivering the "molecularly targeted" anti-HER2 drug lapatinib to a specific metastatic site - the brain. Our approach exploits the unique properties of brain homing peptide Angiopep-2 to improve penetration of lapatinib across the BBB to treat HER2+ brain metastasis. The 19-amino acid peptide Angiopep-2 binds to the low-density lipoprotein receptor-related protein (LRP-1) receptor, which is transcytosed into the brain with a much higher BBB transcytosis efficiency than transferrin. The goal of this research is to develop brain permeable lapatinib Angiopep-2 conjugates that can enhance therapeutic drug levels in the brain to treat HER2+ breast cancer brain metastasis. We hypothesize that lapatinib-Angiopep-2 conjugates will cross the BBB more efficiently than lapatinib itself and lead to higher lapatinib accumulation in the brain metastasis consequently, therapeutic benefits will be obtained in targeting and destroying HER2+ breast cancer brain metastasis. We plan to test the hypothesis through three specific aims: (1) optimize lapatinib-Angiopep conjugates with improved solubility, serum stability, and ability to achieve localized lapatinib release; (2) demonstrate the effectiveness of brain penetration, cellular uptake and release, and cytotoxic potency of the optimized conjugates; (3) validate enhanced brain accumulation and therapeutic efficacy of optimized conjugates in HER2-overexpressing breast cancer brain metastasis models in immunodeficient mice. We will optimize synthetic protocols to chemically attach the lapatinib to the peptide backbone of Angiopep-2 via different cross-linkers. We will study the stability of conjugates in mouse and human serum and cytotoxicity in the HER2-overexpressing breast cancer cells. We will determine the BBB transport rates of the conjugates using in situ mouse brain perfusion technique. We will test the efficacy of conjugates in our established breast cancer brain metastasis mouse models by intracardiac and intracranial injection of brain-seeking HER2 overexpressing human breast cancer cells into nude mice, and monitoring tumor growth and/or regression after conjugate treatment. Successful completion of this project will identify a lapatinib delivery system that is capable of crossing the BBB and is active against breast cancer brain metastases animal models. If successful, the research can be translatable into the clinic and will potentially lead t a major step forward in extending the lives of breast cancer patients with HER2 positive brain metastases. This work will have a broader impact upon the delivery of other molecular targeted tyrosine kinase inhibitors such as gefitinib and erlotinib, structural analogs of lapatinib, for th treatment of CNS metastases originating from other cancers.