cyclic(arg-gly-asp-d-phe-val) and arginyl-glycyl-aspartic-acid

Halogenated l- or d-tryptophan obtained by biocatalytic halogenation was incorporated into RGD peptides together with a variety of alkyl or aryl boronic acids. Suzuki-Miyaura cross-coupling either in solution or on-resin results in side chain-to-tail-cyclized RGD peptides, for example, with biaryl moieties, providing a new dimension of structure-activity relationships. An array of RGD peptides differing in macrocycle size, the presence of d-amino acid,

Topics: Boronic Acids; Cell Line, Tumor; Cyclization; Humans; Hydrocarbons, Halogenated; Models, Chemical; Molecular Dynamics Simulation; Molecular Structure; Oligopeptides; Solvents; Structure-Activity Relationship

On the basis of a previously discovered anti-α

Topics: Angiogenesis Inhibitors; Animals; Cell Line; Humans; Indoles; Integrin alphaVbeta3; Mice; Neoplasms, Experimental; Neovascularization, Pathologic; Oligopeptides; Pyrroles; Sunitinib; Vascular Endothelial Growth Factor Receptor-2

A novel series of β-lactam derivatives that was designed and synthesized to target RGD-binding and leukocyte integrins is reported. The compound library was evaluated by investigating the effects on integrin-mediated cell adhesion and cell signaling in cell lines expressing α

Topics: beta-Lactams; Binding Sites; Cell Adhesion; Cells, Cultured; Dose-Response Relationship, Drug; Humans; Integrins; Leukocytes; Models, Molecular; Molecular Structure; Oligopeptides; Signal Transduction; Structure-Activity Relationship

Tumor targeting anticancer drug conjugates that contain a tumor recognition motif (homing device) are of high current relevance. Cryptophycins, naturally occurring cytotoxic cyclo-depsipeptides, have been modified by total synthesis to provide analogues suitable for conjugation to peptide-based homing devices. An array of functionalized β(2)-amino acids was synthesized and incorporated into cryptophycins. All analogues proved to be highly active in the cytotoxicity assay using the human cervix carcinoma cell line KB-3-1 and its multidrug-resistant subclone KB-V1. Conformational analysis of cryptophycin-52 and two synthetic analogues was performed by NMR and MD methods to obtain information on the influence of the unit C configuration on the overall conformation. An azide-functionalized cryptophycin was connected by CuAAC to an alkyne-containing fluorescently labeled cyclic RGD-peptide as the homing device for internalization studies. Confocal fluorescence microscopy proved integrin-mediated internalization by endocytosis and final lysosomal localization of the cryptophycin prodrug.

Topics: Cell Line, Tumor; Depsipeptides; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Endocytosis; Female; Humans; Inhibitory Concentration 50; Microscopy, Confocal; Molecular Dynamics Simulation; Nuclear Magnetic Resonance, Biomolecular; Oligopeptides; Protein Conformation

A small library of integrin ligand-paclitaxel conjugates 10-13 was synthesized with the aim of using the tumor-homing cyclo[DKP-RGD] peptidomimetics for site-directed delivery of the cytotoxic drug. All the paclitaxel-RGD constructs 10-13 inhibited biotinylated vitronectin binding to the purified αVβ3 integrin receptor at low nanomolar concentration and showed in vitro cytotoxic activity against a panel of human tumor cell lines similar to that of paclitaxel. Among the cell lines, the cisplatin-resistant IGROV-1/Pt1 cells expressed high levels of integrin αVβ3, making them attractive to be tested in in vivo models. cyclo[DKP-f3-RGD]-PTX 11 displayed sufficient stability in physiological solution and in both human and murine plasma to be a good candidate for in vivo testing. In tumor-targeting experiments against the IGROV-1/Pt1 human ovarian carcinoma xenotransplanted in nude mice, compound 11 exhibited a superior activity compared with paclitaxel, despite the lower (about half) molar dosage used.

Topics: Animals; Antineoplastic Agents, Phytogenic; Cell Line, Tumor; Female; Humans; Immunohistochemistry; In Vitro Techniques; Integrin alphaVbeta3; Magnetic Resonance Spectroscopy; Male; Oligopeptides; Paclitaxel; Peptidomimetics; Spectrometry, Mass, Electrospray Ionization

We synthesized disulfide-based cyclic RGD pentapeptides bearing a near-infrared fluorescent dye (cypate), represented by cypate-c(CRGDC) (1) for integrin-targeted optical imaging. These compounds were compared with the traditional lactam-based cyclic RGD counterpart, cypate-c(RGDfK) (2). Molecular modeling suggests that the binding affinity of 2 to integrin α(v)β(3) is an order of magnitude higher than that of 1. This was confirmed experimentally, which further showed that substitution of Gly with Pro, Val and Tyr in 1 remarkably hampered the α(v)β(3) binding. Interestingly, cell microscopy with A549 cells showed that 1 exhibited higher cellular staining than 2. These results indicate that factors other than receptor binding affinity to α(v)β(3) dimeric proteins mediate cellular uptake. Consequently, 1 and its analogs may serve as valuable molecular probes for investigating the selectivity and specificity of integrin targeting by optical imaging.

Topics: Chromatography, High Pressure Liquid; Cyclization; Disulfides; Fluorescent Dyes; Integrins; Oligopeptides; Spectrometry, Mass, Electrospray Ionization; Spectroscopy, Near-Infrared

The solid-phase synthesis of two diastereomeric cyclic pseudopeptides containing the Arg-Gly-Asp sequence and the dipeptide isostere 2-amino-3-oxotetrahydro-1H-pyrrolizine-7a(5H)-carboxylic acid (GPTM) is described. Competition binding assays to purified alphavbeta3 and alphavbeta5 integrins with respect to [125I]echistatin showed a high inhibitory activity for the (2S,7aS)-GPTM derivative. Effects of the structural constraint induced by the two enantiomeric scaffolds (2R,7aR)-GPTM and (2S,7aS)-GPTM on the conformation of Arg-Gly-Asp sequence have been computationally investigated using as a reference the recently solved X-ray structure of cyclo(Arg-Gly-Asp-d-Phe-[N-Me]Val) in complex with the extracellular fragment of the alphavbeta3 receptor. The computational method disclosed the key role played by a bridging water molecule on differentiating the two ligands by a diverse stabilization of the ligand-protein complex.

Topics: Computer Simulation; Integrin alphaVbeta3; Integrins; Ligands; Models, Molecular; Molecular Structure; Oligopeptides; Peptides, Cyclic; Receptors, Vitronectin; Structure-Activity Relationship

A series of six arginine-glycine-aspartate (RGD) cyclopeptide analogues containing a C(alpha)-di- or trifluoromethylamino acid (alpha-Dfm or alpha-TfmAaa) at different positions of the ring were synthesized. All peptides were obtained in two diastereomeric forms, which were separated by HPLC. In vitro biological tests of the new cyclopeptides P were carried out in comparison with their corresponding cyclopeptides R lacking the alpha-fluoromethyl group. Five out of the six compounds P-I (containing (S)-alpha-Tfm-Aaa) showed activities in the nanomolar range, while the P-II compounds (containing (R)-alpha-Tfm-Aaa) were much less active or totally inactive. Only cyclo[RGDf-(S)-alphaTfmV] (P1-I) was found to be significantly more active than its model compound cyclo(RGDfV) (R1). The three-dimensional structure in water and DMSO was determined by NMR techniques and molecular dynamics (MD) calculations, but it was not possible to highlight significant differences in the backbone conformation of the peptides examined. Significant interproton distances, derived from nuclear Overhauser effect (NOE) experiments, were used to determine the absolute configuration of the side chains.

Topics: Amino Acids; Dimethyl Sulfoxide; Fluorine; Integrin alphaVbeta3; Integrins; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Conformation; Oligopeptides; Peptides, Cyclic; Receptors, Vitronectin; Stereoisomerism; Structure-Activity Relationship; Water

Among RGD-dependent integrins, the alpha(v)beta3 receptor has recently received increasing attention as a therapeutic target because of its critical role in tumor-induced angiogenesis and metastasis formation. Here, we describe a new peptide antagonist of alpha(v)beta3 receptor, designed on the basis of the crystal structure of integrin alpha(v)beta3 in complex with c(RGDf[NMe]V) and the NMR structure of echistatin. Cell adhesion assays have demonstrated that the peptide is a potent and selective antagonist of the alpha(v)beta3 receptor.

Topics: Cell Adhesion; Crystallography, X-Ray; Drug Design; Humans; Integrin alphaVbeta3; Integrins; Intercellular Signaling Peptides and Proteins; K562 Cells; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Mimicry; Molecular Structure; Oligopeptides; Peptides; Radioligand Assay; Receptors, Vitronectin; Vitronectin

Eleven gamma-aminocyclopentane carboxylic acid (Acpca) platforms, including four dihydroxy representatives (19-22), three hydroxy analogues (34-36), and four deoxy derivatives (30-33), were prepared in a chiral nonracemic format. These simple units were then grafted onto an Arg-Gly-Asp (RGD) tripeptide framework by a mixed solid phase/solution protocol delivering an ensemble of 11 macrocyclic analogues of type cyclo-[-Arg-Gly-Asp-Acpca-], 1-11. The individual compounds were evaluated for their binding affinity toward the alphaVbeta3 and alphaVbeta5 integrin receptors. The analogue 10 exhibited a very interesting activity profile (IC50/alphaVbeta3= 1.5 nM; IC50/alphaVbeta5= 0.59 nM), comparable to that of reference compounds EMD121974 and ST1646. Closely related congeners 6, 8, and 9 also proved to be excellent dual binders with activity levels in the low nanomolar range. The three-dimensional (3D) NMR solution structures were determined, and docking studies to X-ray crystal structure of the extracellular segment of integrin alphaVbeta3 in complex with the reference compound EMD121974 were performed on selected analogues to elucidate the interplay between structure and function in these systems and to evidence the subtle bases for receptorial recognition. The results prove that the principle of isosteric dipeptide replacement for peptidomimetics design and synthesis can be violated, without detriment to the development of highly effective integrin binders.

Topics: Binding, Competitive; Crystallography, X-Ray; Cycloleucine; Integrin alphaVbeta3; Integrins; Models, Molecular; Molecular Structure; Oligopeptides; Peptides, Cyclic; Protein Binding; Radioligand Assay; Receptors, Vitronectin; Snake Venoms; Solutions; Structure-Activity Relationship