HER2-targeted exosomal delivery of therapeutic mRNA for enzyme pro-drug therapy

描述（由申请人提供）：为了响应NIH RFA: RM-12-014，建议设计外泌体，即人体的“天然抗原递送系统”，以增强其激活还原性前药并附着在其表面配体上的自然能力，特异性靶向her2阳性乳腺癌，其中许多病例对当前治疗（例如曲妥珠单抗）具有耐药性。这将用于P.I. （a.c.m atin, Ph.D.）新发现的酶激活前药治疗。前药为6-氯-9-硝基-5-氧- 5h -苯并-(a)-苯恶嗪（CNOB），经PI改良的人源化酶为hChrR43。该方案的一个非常有用的特点是，活化的细胞毒性产物，9-氨基-6-氯- 5h -苯并[A]苯恶嗪-5- 1 (MCHB)，是强荧光的，可以在活体小鼠中观察到。这一特性使“观察方法”成为可能，并将最大限度地减少对小鼠牺牲的需要和使用更复杂的测试，例如LC/MS/MS、免疫组织化学、western。将从小鼠树突状细胞中分离出外泌体，并使用外泌体表面蛋白Lamp2b将HER2靶向配体KCCYSL添加到其表面。治疗方案将包括通过尾静脉注射给药的两种类型的外泌体，一种装载稳定的hChrR43 mRNA，另一种装载CNOB。mRNA将代替DNA用于基因传递，因为它被证明在这方面更好；它将通过电穿孔和/或使用选择性地将细胞mRNA导入外泌体的“邮政编码”序列装载到外泌体中。通过将CNOB与外泌体一起在PBS中孵育，通过先前证实的技术将其装载。我们还将构建几种类型的报告外泌体，以优化特异性靶向her2阳性乳腺癌的条件，确保mRNA转染癌细胞所需的水平及其翻译效率。UH2期将涉及定向和负载外泌体的构建；在体外优化它们的靶向特异性和her2阳性乳腺癌细胞杀伤，然后在免疫功能低下小鼠体内植入人her2阳性乳腺癌细胞系的肿瘤进行优化。后一项研究还将包括一个过表达HER2+受体的患者源性乳腺癌肿瘤异种移植小鼠模型，这是一个更现实的测试治疗效果的系统。UH3阶段将涉及大鼠和狗的单剂量药代动力学和毒性研究，随后在大鼠和狗中进行重复剂量范围毒性研究，以根据未观察到的不良反应水平（NOAEL）和靶器官毒性选择GLP亚慢性研究的剂量水平；并向FDA寻求ind前的反馈。拟议的研究拥有所需的专业知识，包括5名斯坦福大学的科学家，附近的外泌体专家和一个主要的药理学研究组织SRI。

DESCRIPTION (provided by applicant): In response to NIH RFA: RM-12-014, it is proposed to engineer exosomes, the body's "natural antigen delivery system," in order to enhance their natural capacity to activate reductive prodrugs and attach to their surface ligands that specifically target HER2-positive breast cancer, many cases of which are resistant to the current therapies (e.g., trastuzumab) . This will be done for an enzyme-activated prodrug therapy newly discovered by the P.I. (A.C. Matin, Ph.D.). The prodrug is 6-chloro-9-nitro-5-oxo-5H-benzo-(a)-phenoxazine (CNOB), and the humanized enzyme improved by the PI is hChrR43. A highly helpful feature of this regimen is that the activated cytotoxic product of CNOB, 9-amino-6-chloro-5H-benzo[a]phenoxazine-5-one (MCHB), is strongly fluorescent and can be visualized in living mice. This property makes an 'observational approach' possible, and will minimize the need for mouse sacrifice and the use of more involved tests, e.g., LC/MS/MS, immunohistochemical, Westerns. Exosomes will be isolated from mouse dendritic cells, and the HER2- targeting ligand KCCYSL will be added to their surface using the exosome surface protein Lamp2b. The therapeutic regimen will consist of two types of exosomes administered by tail vein injection, those loaded with stabilized hChrR43 mRNA and those loaded with CNOB. mRNA instead of DNA will be used for gene delivery as it is proving to be better for this purpose; it will be loaded into the exosomes by electroporation and/or using the "zip code" sequence that selectively directs cellular mRNA into the exosomes. CNOB will be loaded by previously proven techniques by incubating it in PBS with the exosomes. Several types of reporter exosomes will also be constructed to optimize the conditions for specific targeting of HER2-positive breast cancer, ensuring the necessary transfection levels of cancer cells by the mRNA and its translational efficiency. The UH2 phase will concern with the construction of the directed and loaded exosomes; the optimization of their targeting specificity and HER2-positive breast cancer cell killing in vitro, followed by this optimization in vivo using implanted tumors o human HER2-positive human breast cancer cell lines in immunocompromised mice. The latter studies will also include a patient-derived breast cancer tumor xenograft mouse model that overexpress the HER2+ receptor, which is a more realistic system for testing the efficacy of the therapy. The UH3 phase will concern single dose pharmacokinetics and toxicity studies in rats and dogs, followed by repeat dose range finding toxicity studies in rats and dogs to select dose levels for the GLP subchronic studies, based on the no observed adverse effects level (NOAEL) and target organs for toxicity; and seeking pre-IND feedback from the FDA. The proposed research possesses the required mix of expertise and involves 5 Stanford scientists, a nearby exosome expert, and a premier organization, SRI for pharmacological studies.