配体靶向药物传递系统的研究进展

利用肿瘤细胞表面过度表达的某些生物大分子受体能够与其配体特异性结合的特点,用配体与药物结合,形成配体靶向药物递送系统。配体发挥导向物作用,将药物靶向递送到肿瘤细胞(或组织),实现主动靶向释药,提高药物的选择性,从而增加药效。文中介绍了以维生素(叶酸、维生素B12,维生素A)、蛋白质(转铁蛋白、低密度脂蛋白)、多糖(半乳糖、甘露糖、透明质酸)、整合素等生物大分子为配体的靶向药物递送系统研究进展。     

叶酸靶向的肿瘤治疗研究进展

叶酸靶向的递药系统是一种新兴的治疗多种恶性肿瘤的方法。利用叶酸分子与肿瘤细胞表面叶酸受体的高亲和力,叶酸偶联的化合物能够将分子大小不同的复合物递送给病理细胞而不对正常组织造成伤害。目前,通过这种方法成功递送到叶酸受体高表达肿瘤细胞的复合物包括:蛋白毒素、化疗药物、免疫治疗剂、基因载体、反义寡核苷酸、小分子干扰RNA和纳米载体。该文综述了多种叶酸作为靶向配体治疗恶性肿瘤的方法。     

配体-受体系统介导的药物靶向性研究进展

配体-受体系统介导的药物靶向性研究在过去10年中得到了很大的发展。配体介导的主动靶向能够将药物定向运送到血管腔隙、细胞表面和细胞内。使用的配体包括抗体、蛋白质、肽、脂蛋白、糖类以及其他内源性分子。文章介绍了药物靶向研究中使用的多种配体-受体系统，包括运铁蛋白受体、脂蛋白受体、细胞因子受体、凝集素受体、清道夫受体和叶酸受体。     

RGD肽在肿瘤靶向纳米给药系统中的应用

RGD肽是一类含有精氨酸一甘氨酸一天冬氨酸(Arg-Gly-Asp)的短肽,作为肿瘤细胞或者新生血管特异表达的整合素和其配体相互作用的识别位点,可介导肿瘤的靶向治疗.抗肿瘤药物及其递送系统经过RGD肽修饰.可增加药物的肿瘤主动靶向特性,达到更有效、精确和安全的治疗.本文主要综述了RGD肽在脂质体、聚合物胶束、基因载体等...     

多肽修饰脂质体靶向药物递送系统研究进展

目的介绍近年来多肽修饰脂质体靶向药物递送系统的研究进展。方法查阅和归纳总结近几年相关文献。结果阐述了精氨酸-甘氨酸-天冬氨酸（RGD）多肽、丙氨酸-脯氨酸-精氨酸-脯氨酸-甘氨酸（APRPG）多肽、细胞穿透肽（CPP）、血管活性肠肽（VIP）等修饰脂质体的研究进展。多肽修饰的包载药物的脂质体可以增加药物在体内的选择性,减少药物毒副作用,提高药物治疗指数。结论多肽分子是机体内一类重要的生物活性物质,将其作为导向物以配体-受体特异性结合的方式应用于靶向药物递送系统,具有良好的研究价值和应用前景。     

多肽修饰脂质体靶向药物递送系统研究进展

目的 介绍近年来多肽修饰脂质体靶向药物递送系统的研究进展。方法 查阅和归纳总结近几年相关文献。结果 阐述了精氨酸-甘氨酸-天冬氨酸(RGD)多肽、丙氨酸-脯氨酸-精氨酸-脯氨酸-甘氨酸(APRPG)多肽、细胞穿透肽(CPP)、血管活性肠肽(VIP)等修饰脂质体的研究进展。多肽修饰的包载药物的脂质体可以增加药物在体内的选择性,减少药物毒副作用,提高药物治疗指数。结论 多肽分子是机体内一类重要的生物活性物质,将其作为导向物以配体-受体特异性结合的方式应用于靶向药物递送系统,具有良好的研究价值和应用前景。     

基于去唾液酸糖蛋白受体的肝靶向药物的研究

去唾液酸糖蛋白受体(asialoglycoprotein receptor, ASGPR)是一种在肝实质细胞表面高度表达的受体,它可以特异性识别和结合末端带有半乳糖或N-乙酰基半乳糖胺残基的分子,通过网格蛋白介导其内吞并转运至溶酶体中降解。基于这一特性, ASGPR介导的肝靶向药物递送会增加药物在肝脏中的分布、减少药物潜在不良反应并降低给药剂量。本文全面综述了ASGPR的表达、组成与结构、结合及内吞,系统总结了基于ASGPR的配体设计、优化及其释放策略,并展望该受体在药物开发中的应用。     

叶酸受体介导的靶向给药系统研究进展

叶酸受体在多种肿瘤细胞表面过度表达,能与特异性的配体结合并将药物靶向运输到特定的肿瘤细胞。本文介绍了叶酸受体介导的靶向给药系统的作用机制和几种常见的药物载体系统。     

受体介导肿瘤主动靶向的研究进展

肿瘤细胞表面过度表达一系列受体，能与特异性的配体或抗体结合并诱导细胞内化。以这些受体作为靶点，使药物与特异性配体或抗体结合即可将药物主动靶向肿瘤细胞。本文综述目前在临床和实验研究中用于肿瘤主动靶向的几种受体，包括酪氨酸激酶受体、叶酸受体、激素受体、脂蛋白受体、转铁蛋白受体等。通过了解这些受体及其在肿瘤主动靶向方面的作用，有助于我们对抗肿瘤药物和新型抗肿瘤药物载体的研究。     

功能基修饰的脑靶向递药系统的研究概况

目的:研究功能基修饰的脑靶向递药系统,为提高脑靶向递药系统的靶向效率提供参考。方法:以"功能基""修饰""脑靶向""Functional group""Modified""Brain-targeting"等为关键词,组合查询2001年1月-2018年12月在中国知网、万方数据、维普网、PubMed、Elsevier、Springer Link等数据库中的相关文献,对功能基修饰的脑靶向递药系统进行综述。结果与结论:共检索到相关文献394篇,其中有效文献41篇。脑靶向包括受体介导(介导的受体如转铁蛋白受体、低密度脂蛋白受体、N-乙酰胆碱受体等)、转运体介导(介导的转运体如葡萄糖转运体、谷胱甘肽转运体等)、吸附介导。以上述受体、转运体的配体作为功能基,采用共价键结合或非共价键连接方法进行修饰,构建脑靶向递药系统;功能基通过与相应受体或转运体特异性结合,使药物跨越血脑屏障(BBB)并且在脑内病灶部位释药;除此之外,还可通过功能基带有的正电荷与BBB膜上的负电荷发生静电吸附作用产生非特异性的吸附,介导药物进入脑内。基于受体介导、转运体介导、吸附介导的靶向方式,有望提高脑组织中的药物浓度,提高中枢神经系统疾病的治疗效果,降低毒副作用及不良反应。与受体介导、转运体介导、吸附介导相比较,双级靶向可同时修饰两种靶向分子(一种靶向分子靶向于BBB,另一种靶向分子靶向于病灶),有望提高脑部疾病的治疗效果并降低药物在非病灶部位的蓄积,是一种更为理想的手段。在后续相关研究中建议开发新靶点和新型靶向分子,进一步提高脑靶向递药系统的靶向效率,为开发操作简单、成本低廉的脑靶向递药系统提供参考。     

Anticancer activity of a peptide combination in gastrointestinal cancers targeting multiple neuropeptide receptors

Summary  A novel peptide combination consisting of four synthetic neuropeptide analogs of Vasoactive Intestinal Peptide (VIP), Bombesin, Substance P and Somatostatin has been found to have potent anticancer activity in vitro and in vivo. The receptors of these four neuropeptides are known to be over expressed in various cancers. We have found the presence of native neuropeptides in the culture supernatant of the primary tumor cells of human colon adenocarcinomas. It was further demonstrated by receptor-ligand assays that not only do these tumor cells synthesize and secrete four peptide hormones but also possess specific high affinity receptors on their surface. Screening a large panel of analogs to the four peptide hormones on tumor cell proliferation led to the identification of four cytotoxic analogs, the combination of which was code-named DRF7295. The design and synthesis of the peptide analogs have been described in this paper. In vitro anticancer activity of DRF7295 was studied in a large panel of human tumor cells. Gastrointestinal tumor cells of the colon, pancreas and duodenum were found to be most sensitive to DRF7295 with moderate activity seen in glioblastoma, prostate, leukemia and those of oral cancer cells. Efficacy studies in xenograft models of colon and duodenum resulted in T/C% of less than 40%, which is indicative of strong tumor regressing potential of DRF7295 in gastrointestinal cancers. Acute and long-term toxicity studies as well as safety pharmacology studies conducted indicate the safety of the drug upon systemic administration with no significant adverse pharmacological effects.     

Targeted delivery of a proapoptotic peptide to tumors in vivo

RGD peptides recognize the α_vβ₃ integrin, a receptor that is overexpressed on the surface of both tumor blood vessels and cancerous cells. These peptides are powerful tools that act as single antiangiogenic molecules, but recently also have been used for tumor imaging and drug targeting. We designed the molecule RAFT-(c[-RGDfK-])₄, a constrained and chemically defined entity that can be produced at clinical-grade quality. This scaffold was covalently coupled via a labile bridge to the proapoptotic peptide (KLAKLAK)₂ (RAFT-RGD-KLA). A fluorescent, activatable probe was also introduced, allowing intracellular localization. At 2.5 µM, this molecule induced the intracellular release of an active KLA peptide, which in turn caused mitochondrial depolarization and cell death in vitro in tumor cells. In a mouse model, the RAFT-RGD-KLA peptide was found to prevent the growth of remote subcutaneous tumors. This study demonstrated that the antitumor peptide is capable of killing tumor cells in an RGD-dependent manner, thus lowering the nonspecific cytotoxic effects expected to occur when using cationic cytotoxic peptides. Thus, this chemistry is suitable for the design of complex, multifunctional molecules that can be used for both imaging and therapeutics, representing the next generation of perfectly controlled, targeted drug-delivery systems.     

Use of analogs of peptide hormones conjugated to cytotoxic radicals for chemotherapy targeted to receptors on tumors

Specific receptors for luteinizing hormone-releasing hormone (LH-RH), somatostatin, bombesin, and other peptides are found on various cancers. We review the development of cytotoxic analogs of LH-RH, somatostatin, and bombesin/gastrin releasing peptide (GRP) designed for targeting chemotherapy to peptide receptors on various cancers. Cytotoxic analogs of LH-RH, AN-152 and AN-207, containing doxorubicin (DOX) or 2-pyrrolino-DOX (AN-201), respectively, target LH-RH receptors and may be used for the treatment of prostatic and urinary bladder (urothelial), breast, ovarian and endometrial cancers, non-Hodgkin's lymphomas, melanomas, and renal cell carcinomas. DOX and AN-201 have also been incorporated into the cytotoxic analogs of somatostatin, AN-162 and AN-238, respectively, which are targeted to receptors for somatostatin in prostatic, mammary, ovarian, gastric, renal, colorectal and pancreatic cancers, non-Hodgkin's lymphomas, as well as glioblastomas and lung cancers. They are found to suppress the growth of these tumors and their metastases. A cytotoxic analog of bombesin/GRP, AN-215, containing 2-pyrrolino-Dox, has also been synthesized and shown to inhibit growth of various human cancer lines expressing receptors for bombesin/GRP. The toxicity, pharmacokinetics and maximum tolerated doses of AN-152 were assessed in a phase I clinical trial in women with ovarian or endometrial cancer. Disease stabilization and objective responses were found. Analog AN-152 is now in phase II clinical trials. Phase I/II studies with AN-152 in men with hormone-independent relapsed prostate cancer and patients with pancreatic and bladder cancers are pending. Targeted cytotoxic peptide analogs could provide a more efficacious and less toxic therapy for various cancers.     

Application of human pancreatic carcinoid BON cells for receptor-targeted drug development

In our previous study, we found that several tumor cell lines displayed high receptor-specific binding affinity, one of which, the human pancreatic carcinoid BON cell line, demonstrates high affinity binding of the bombesin (BN) and somatostatin (SST) receptor-specific ligands. In the present study, BON cells, as a representative model, were further applied to evaluate various peptide analogs and cytotoxic receptor-targeted peptide conjugates. We observed quick ligand–receptor internalization in BON cells as well as high binding affinity. Furthermore, BON cells have high expression of multidrug resistance-associated genes (MDR1) and show camptothecin (CPT) resistance. Various receptor-specific cytotoxic conjugates were synthesized and evaluated in the BON cell model via in vitro and in vivo studies. We found that all the tested conjugates displayed potent antitumor ability in xenografts. Especially, the CPT conjugates, CPT-SST, and CPT-BN, are most likely to increase sensitivity to CPT-resistant BON cells. Our findings suggest that appropriately defined tumor cell lines may provide physiologically relevant cell-based evaluations of novel peptide analogs and receptor-targeted chemotherapeutics.     

Investigation of cancer cell lines for peptide receptor-targeted drug development

Many tumors highly express specific populations of G-protein-coupled receptors (GPCRs) that could be utilized for receptor-targeted therapy. We confirmed significant quantities of mRNAs specific for certain somatostatin (SST), vasoactive intestinal peptide (VIP), and bombesin (BN) receptors in various commercially available tumor cell lines. Very few of the tumor cell lines examined displayed the high receptor-binding affinity despite exhibiting the expression of appropriate mRNAs and proteins of the cognate receptors. However, binding assays establish that some tumor cell lines, such as pancreatic cancer CFPAC-1, prostate cancer DU-145, and pancreatic carcinoid BON, demonstrate high BN receptor binding. BON cells also demonstrate high somatostatin receptor (SSTR) affinity binding. We also found that tumor cell lines, such as BON and host cells expressing SST receptor subtypes 1 or 2 (CHO-R1 or CHO-R2), underwent a decrease in cell surface receptor density in multiple passages. BON and CHO-R2 cells also rapidly internalize a significant proportion of cell surface ligand–receptor complexes. The tumor cells CFPAC-1, DU-145, and BON with high receptor binding could be useful for peptide drug studies. BON cells were further applied to test SST/BN analogs and cytotoxic conjugates. Furthermore, the in vivo antitumor assay showed that the cytotoxic conjugate CPT-SST targeting all SSTR subtypes displayed a potent tumor-suppressive ability to BON tumors expressing multiple SSTR subtypes.     

Design of chimeric peptide ligands to galanin receptors and substance P receptors

Several chimeric peptides were synthesized and found to be high-affinity ligands for both galanin and substance P receptors in membranes from the rat hypothalamus. The peptide galantide, composed of the N-terminal part of galanin and C-terminal part of substance P (SP), galanin-(1-12)-Pro-SP-(5-11) amide, which is the first galanin antagonist to be reported, recognizes two classes of galanin binding sites (K_D(1)<0.1 nM and K_D(2)∼ 6 nM) in the rat hypothalamus, while it appears to bind to a single population of SP receptors (K_D∼ 40 nM). The chimeric peptide has higher affinity towards galanin receptors than the endogenous peptide galanin-(1-29) (KD ∼ 1 nm ) or its N-terminal fragment galanin-(1-13) (K_D∼ 1,nm ), which constitutes the A′-terminus of the chimeric peptide. Galantide has also higher affinity for the SP receptors than the C-terminal SP fragment-(4-11) amide (K_D= 0.4μm ), which constitutes its C-terminal portion. Substitution of amino acid residues, which is of importance for recognition of galanin by galanin receptors, such as [Trp²], in the galanin portion of the chimeric peptide or substitution of ([Phe⁷] or [Met¹¹]-amide) in the SP portion of chimeric peptide both cause significant loss in affinity of the analogs of galantide for both the galanin- and the SP-receptors. These results suggest that the high affinity of the chimeric peptide, galantide, may in part be accounted for by simultaneous recognition/binding to both receptors. In line with this suggestion is the finding that the binding of the chimeric ligands to the galanin receptor is strongly influenced by the presence of SP (1 μm ) or spantide (1 μm ). We have performed the synthesis and binding studies with 11 chimeric peptides, all composed of the N-terminal galanin-(1-13) fragment or of its analogs, linked to the C-terminal portion of SP or its peptide antagonist, spantide. Our results, similar to earlier reports on chimeric peptides, suggest that high-affinity ligands to peptide receptors can be produced by linking biologically active N-terminal and C-terminal portions of peptides via linkers, enabling a) independent recognition of the chimeric peptide by the relevant receptors and b) intramolecular interactions between the joined N- and C-terminal peptide fragments. These two phenomena may also explain why some of the chimeric peptides have higher affinity than the endogenous peptide(s) and why galantide, and some of its analogs presented here, behave(s) as a galanin receptor antagonist(s).     

Synthesis and evaluation of potential affinity labels derived from endomorphin‐2

Abstract: In an attempt to identify potential peptide‐based affinity labels for opioid receptors, endomorphin‐2 (Tyr‐Pro‐Phe‐PheNH₂), a potent and selective endogenous ligand for µ‐opioid receptors, was chosen as the parent peptide for modification. The tetrapeptide analogs were prepared using standard Fmoc‐solid phase peptide synthesis in conjunction with incorporation of Fmoc‐Phe(p‐NHAlloc) and modification of the p‐amino group. The electrophilic groups isothiocyanate and bromoacetamide were introduced into the para position on either Phe³ or Phe⁴; the corresponding free amine‐containing peptides were also prepared for comparison. The peptides bearing an affinity label group and their free amine analogs were evaluated in a radioligand‐binding assay using Chinese hamster ovary (CHO) cells expressing µ‐ and δ‐opioid receptors. Modification on Phe⁴ was better tolerated than on Phe³ for µ‐receptor binding. Among the analogs tested, [Phe(p‐NH₂)⁴]endomorphin‐2 showed the highest affinity (IC₅₀ = 37 nm ) for µ‐receptors. The Phe(p‐NHCOCH₂Br)⁴ analog displayed the highest µ‐receptor affinity (IC₅₀ = 158 nm ) among the peptides containing an affinity label group. Most of the compounds exhibited negligible binding affinity for δ‐receptors, similar to the parent peptide.     

Novel CD123-aptamer-originated targeted drug trains for selectively delivering cytotoxic agent to tumor cells in acute myeloid leukemia theranostics

Since conventional chemotherapy for acute myeloid leukemia (AML) has its limitations, a theranostic platform with targeted and efficient drug transport is in demand. In this study, we developed the first CD123 (AML tumor marker) aptamers and designed a novel CD123-aptamer-mediated targeted drug train (TDT) with effective, economical, biocompatible and high drug-loading capacity. These two CD123 aptamers (termed as ZW25 and CY30, respectively) can bind to a CD123 peptide epitope and CD123?+?AML cells with high specificities and KD of 29.41?nM and 15.38?nM, respectively, while has minimal cross reactivities to albumin, IgG and trypsin. Further, TDT is self-assembled from two short primers by ligand-modified ZW25 that acted as initiation position for elongation, while intercalated by doxorubicin (Dox). TDT is capable of transporting high capacity of Dox to CD123?+?cells and retains the efficacy of Dox, while significantly reducing drug uptake and eased toxicity to CD123? cells in vitro (p?in vivo. These suggest that CD123 aptamer and CD123 aptamer-mediated targeted drug delivery system may have potential applications for selective delivery cytotoxic agents to CD123-expressing tumors in AML theranostics.     

The ATTEMPTS delivery systems for macromolecular drugs

Aiming at successful targeted drug delivery – a system that possesses both targeting and prodrug features that can be activated once the system reaches the target site upon systemic administration – would be desired to reduce systemic toxicity. Previously we proposed a heparin/protamine-based system for delivery of protease drugs such as tissue-specific plasminogen activator (t-PA). This approach, termed ‘antibody targeted, triggered, electrically modified prodrug-type strategy’ (ATTEMPTS), would permit antibody-directed administration of inactive t-PA and allow a subsequent triggered release of the active t-PA at the target site. This system can be adapted to target tumor tissues when protein transduction domain (PTD) peptide such as TAT is incorporated in the ATTEMPTS construct. Both in vitro and preliminary in vivo studies using TAT-gelonin (TAT-Gel) and TAT-asparaginase (TAT-ASNase) conjugates have demonstrated that the on/off regulation of the membrane translocation activity of PTD at tumor target, followed by intracellular delivery of cytotoxic macromolecular drug, can be accomplished. Hence, the PTD-mediated delivery system derived from our previous ATTEMPTS approach is a system that incorporates all of the targeting function, prodrug feature, release mechanism and cell entry mechanism and could become a generic system for delivery of macromolecular drugs.     

Estrogen(s) and analogs as a non-immunogenic endogenous ligand in targeted drug/DNA delivery

The maximum therapeutic potentials of pharmacologically active molecules are generally not attained due to their non specific delivery. Ligands associated with drug or delivery system through which it is delivered provide navigation and direction to the carrier system(s) so as to reach and release bioactive(s) at the desired site of action in a optimum therapeutic concentration vis a vis minimizing the undesired side effects associated with non specific delivery. Many ligands employed and implicated in targeted drug delivery have been reportedly found to be mild to strong immunogenic. Hence, their potential utility is considered to be compromised in achieving concept of magic bullet. Therefore endogenous ligand (bio self molecules) based drug/DNA delivery may be a better alternative they being biocomponents so are non-immunogenic and biocompatible per se. Estrogens and their receptors are over expressed in the several pathophysiological conditions including cardiovascular, osteoarthritis and cancer of prostate and ovaries etc. The selective high density of such portal may be utilized for targeting such estrogen receptor rich sites. The several scientific communities from various fields of specialization of science have explored estrogen(s) and their analogs for the purpose of targeting of bioactive(s) either by preparing estrogen-drug conjugates of using estrogens as site-directing ligands attached with various carrier system(s). This review presents an exhaustive account of how hormones especially estrogens and their derivatives could be used for site-specific delivery of bioactive(s), as diagnostic agents and also the future prospects of these bioligands in controlled and targeted clinical pharmacology. Estrogen-drug conjugates and various carrier systems that utilized estrogens as ligands for site-specific delivery have been reviewed and are discussed in detail.