Search

Health-care systems that develop rapidly and efficiently may increase the lifespan of humans. Nevertheless, the older population is more fragile, and is at an increased risk of disease development. A concurrently growing number of surgeries and transplantations have caused antibiotics to be used much more frequently, and for much longer periods of time, which in turn increases microbial resistance. In 1945, Fleming warned against the abuse of antibiotics in his Nobel lecture: "The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant". After 70 years, we are witnessing the fulfilment of Fleming's prophecy, as more than 700,000 people die each year due to drug-resistant diseases. Naturally occurring antimicrobial peptides protect all living matter against bacteria, and now different peptidomimetic strategies to engineer innovative antibiotics are being developed to defend humans against bacterial infections.

Nonpeptidic Arg-Gly-Asp (RGD)-mimic ligands were designed and synthesized by click chemistry between an arginine-azide mimic and an aspartic acid-alkyne mimic. Some of these molecules combine excellent in vitro properties (high α v β 3 affinity, selectivity, drug-like logD, high metabolic stability) with a variety of radiolabeling options (e.g., tritium and fluorine-18, plus compatibility with radio-iodination), not requiring the use of chelators or prosthetic groups. The binding mode of the resulting triazole RGD mimics to α v β 3 or α IIb β 3 receptors was investigated by molecular modeling simulations. Lead compound 12 was successfully radiofluorinated and used for in vivo positron emission tomography/computed tomography (PET/CT) studies in U87 tumor models, which showed only modest tumor uptake and retention, owing to rapid excretion. These results demonstrate that the novel click RGD mimics are excellent radiolabeled probes for in vitro and cell-based studies on α v β 3 integrin, whereas further optimization of their pharmacokinetic and dynamic profiles is necessary for successful use in in vivo imaging., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A 1,2,3-triazole-based RGD peptidomimetic having nanomolar affinity for αvβ3 integrin was conjugated to the potent antimitotic paclitaxel via an oxime heterobifunctional linker. The resulting construct maintained nanomolar binding concentration to αvβ3 integrin and showed 11-fold selectivity in terms of cytotoxicity towards highly αvβ3 expressing U87MG cancer cells relative to non αvβ3 expressing MCF7 cells, indicating promising cancer cell targeting capacity. 1 Design 2 Retrosynthesis 3 Synthesis 4 Solid-Phase Receptor Binding Assay 5 Cell Cytotoxicity Assays 6 Metabolic Stability Assays 7 Conclusions [ABSTRACT FROM AUTHOR]

The Arg-Gly-Asp (RGD) tripeptide is the smallest recognition sequence for the αvβ3 integrin receptor. A number of nonpeptide analogues of the RGD linear sequence, some of them having improved pharmacological properties, have been proposed in the last two decades. In this study, the stereogenic trifluoroethylamine function was employed as peptide bond surrogate for the development of a new class of RGD peptide mimics. In fact, the trifluoroethylamine group was shown to behave as a peptide-bond surrogate maintaining the H-bond donor capacity of the NH peptide group and a CH(CF3)NH backbone angle close to the native peptide bond 120°. The trifluoroethylamine function is also known to display high metabolic stability and in some cases it positively affects ligand-receptor interactions. Two linear Ψ[CH(CF3)NH]Gly-RGD diastereoisomers were synthesized with good stereocontrol and submitted to biological assays. A remarkable loss in αvβ3 integrin affinity was observed for both compounds, suggesting that the bulky CF3 moiety is not well tolerated within the αvβ3 binding pocket. [ABSTRACT FROM AUTHOR]