Enhancing the oral bioavailability of peptide drug leads is a major challenge in drug design. As such, methods to address this challenge are highly sought after by the pharmaceutical industry. Here, we propose a strategy to identify appropriate amides for N-methylation using temperature coefficients measured by NMR to identify exposed amides in cyclic peptides. N-methylation effectively caps these amides, modifying the overall solvation properties of the peptides and making them more membrane permeable. The approach for identifying sites for N-methylation is a rapid alternative to the elucidation of 3D structures of peptide drug leads, which has been a commonly used structure-guided approach in the past. Five leucine-rich peptide scaffolds are reported with selectively designed N-methylated derivatives. In vitro membrane permeability was assessed by parallel artificial membrane permeability assay and Caco-2 assay. The most promising N-methylated peptide was then tested in vivo. Here we report a novel peptide (15), which displayed an oral bioavailability of 33% in a rat model, thus validating the design approach. We show that this approach can also be used to explain the notable increase in oral bioavailability of a somatostatin analog.cyclic peptide | permeability | N-methylation P eptides are potentially valuable compounds for drug development, offering many advantages over other molecular classes (1-4). Specifically, their ability to mimic endogenous bioactive molecules allows them to bind potently and selectively to "difficult" drug targets, including protein-protein interactions that are too challenging for small-molecule therapeutics. However, the widespread use of peptides in the clinic has been slow in coming, in large part because of their generally low stability in vivo, high clearance, and poor oral bioavailability.The low oral bioavailability of peptides is attributed to a disparity between their physicochemical properties and those traditionally expected for "drug-likeness" (5, 6), leading to a perception that peptides are good drug leads but poor drugs. However, this perception is being challenged by a growing number of peptides that seem to be stable (7) and well absorbed within the gastrointestinal tract (8) and examples in which cyclic peptides have shown orally delivered bioactivity in animal disease models, including inflammatory pain (9) and neuropathic pain (10), prompting us to devise new rules for predicting pharmacokinetic properties of this compound class. Arguably the most famous example of a peptide with poor drug-likeness but reasonable oral bioavailability is cyclosporin A, widely used as the immunosuppressant drug cyclosporine (11). Two structural features of cyclosporin A in particular are thought to contribute to its oral bioavailability, namely its macrocyclic architecture and backbone N-methylation.Cyclization imparts increased rigidity to a parent peptide, which not only improves its stability against proteolytic degradation but also directs it into specific conformations that m...
The incidence of obesity is rising worldwide at an alarming rate and is becoming a major public health concern with incalculable social and economic costs. Studies have exposed the relationship between the adiposity, inflammation and the development of other metabolic disorders, so dietary factors that influence some or all of these are of interest. Dietary phytochemicals appear to be able to target different stages of the adipocyte (fat cell) lifecycle. For example, several classes of polyphenols have been implicated in suppressing the growth of adipose tissue through modifying the adipocyte lifecycle. Many dietary phytochemicals also have strong anti-inflammatory activity, but the amount present in plants varies and may be affected by processing. In this review we summarise the likely mechanisms of action of plant phytochemicals. We highlight the major vegetable sources of polyphenols, including those with possible synergistic attributes, discuss the variation in polyphenol levels and their distribution in cultivars and outline the effects of food processing. The identification and characterisation of the anti-obesogenic properties of phytochemicals in vegetables, as well as an appreciation of the effect of cooking on phytochemical content provide significant new information supporting dietary guidelines that encourage vegetable consumption for the prevention and management of lifestyle related disease.
New phenoxyacetic acid antagonists of CRTH2 are described. Following the discovery of a hit compound by a focused screening, high protein binding was identified as its main weakness. Optimization aimed at reducing serum protein binding led to the identification of several compounds that showed not only excellent affinities for the receptor (41 compounds with K(i) < 10 nM) but also excellent potencies in a human whole blood assay (IC(50) < 100 nM; PGD2-induced eosinophil shape change). Additional optimization of the PK characteristics led to the identification of several compounds suitable for in vivo testing. Of these, 19k and 19s were tested in two different pharmacological models (acute FITC-mediated contact hypersensitivity and ovalbumin-induced eosinophilia models) and found to be active after oral dosing (10 and 30 mg/kg).
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