A non-peptide NK1 receptor agonist showing subpicomolar affinity

Crystal structure of the human NK1 tachykinin receptor

The NK₁ tachykinin G-protein-coupled receptor (GPCR) binds substance P, the first neuropeptide to be discovered in mammals. Through activation of NK₁R, substance P modulates a wide variety of physiological and disease processes including nociception, inflammation, and depression. Human NK₁R (hNK₁R) modulators have shown promise in clinical trials for migraine, depression, and emesis. However, the only currently approved drugs targeting hNK₁R are inhibitors for chemotherapy-induced nausea and vomiting (CINV). To better understand the molecular basis of ligand recognition and selectivity, we solved the crystal structure of hNK₁R bound to the inhibitor L760735, a close analog of the drug aprepitant. Our crystal structure reveals the basis for antagonist interaction in the deep and narrow orthosteric pocket of the receptor. We used our structure as a template for computational docking and molecular-dynamics simulations to dissect the energetic importance of binding pocket interactions and model the binding of aprepitant. The structure of hNK₁R is a valuable tool in the further development of tachykinin receptor modulators for multiple clinical applications.

Design, synthesis and biological studies of a library of NK1-Receptor Ligands Based on a 5-arylthiosubstituted 2-amino-4,6-diaryl-3-cyano-4H-pyran core: Switch from antagonist to agonist effect by chemical modification

A library of 5-arylthiosubstituted 2-amino-4,6-diaryl-3-cyano-4H-pyrans has been synthesized as a new family of non-peptide NK1 receptor ligands by a one-pot cascade process. Their biological effects via interaction with the NK1 receptor were experimentally determined as percentage of inhibition (for antagonists) and percentage of activation (for agonists), compared to the substance P (SP) effect, in IPone assay. A set of these amino compounds was found to inhibit the action of SP, and therefore can be considered as a new family of SP-antagonists. Interestingly, the acylation of the 2-amino position causes a switch from antagonist to agonist activity. The 5-phenylsulfonyl-2-amino derivative 17 showed the highest antagonist activity, while the 5-p-tolylsulfenyl-2-trifluoroacetamide derivative 20R showed the highest agonist effect. As expected, in the case of the 5-sulfinylderivatives, there was an enantiomeric discrimination in favor of one of the two enantiomers, specifically those with (S_S,R_C) configuration. The anticancer activity studies assessed by using human A-549 lung cancer cells and MRC-5 non-malignant lung fibroblasts, revealed a statistically significant selective cytotoxic effect of some of these 2-amino-4H-pyran derivatives toward the lung cancer cells. These studies demonstrated that the newly synthesized 4H-pyran derivatives can be used as a starting point for the synthesis of novel SP-antagonists with higher anticancer activity in the future.

Neuropeptides: metabolism to bioactive fragments and the pharmacology of their receptors

The proteolytic processing of neuropeptides has an important regulatory function and the peptide fragments resulting from the enzymatic degradation often exert essential physiological roles. The proteolytic processing generates, not only biologically inactive fragments, but also bioactive fragments that modulate or even counteract the response of their parent peptides. Frequently, these peptide fragments interact with receptors that are not recognized by the parent peptides. This review discusses tachykinins, opioid peptides, angiotensins, bradykinins, and neuropeptide Y that are present in the central nervous system and their processing to bioactive degradation products. These well-known neuropeptide systems have been selected since they provide illustrative examples that proteolytic degradation of parent peptides can lead to bioactive metabolites with different biological activities as compared to their parent peptides. For example, substance P, dynorphin A, angiotensin I and II, bradykinin, and neuropeptide Y are all degraded to bioactive fragments with pharmacological profiles that differ considerably from those of the parent peptides. The review discusses a selection of the large number of drug-like molecules that act as agonists or antagonists at receptors of neuropeptides. It focuses in particular on the efforts to identify selective drug-like agonists and antagonists mimicking the effects of the endogenous peptide fragments formed. As exemplified in this review, many common neuropeptides are degraded to a variety of smaller fragments but many of the fragments generated have not yet been examined in detail with regard to their potential biological activities. Since these bioactive fragments contain a small number of amino acid residues, they provide an ideal starting point for the development of drug-like substances with ability to mimic the effects of the degradation products. Thus, these substances could provide a rich source of new pharmaceuticals. However, as discussed herein relatively few examples have so far been disclosed of successful attempts to create bioavailable, drug-like agonists or antagonists, starting from the structure of endogenous peptide fragments and applying procedures relying on stepwise manipulations and simplifications of the peptide structures.

N-(1-Oxy-2-picolyl)oxalamic acids as a new type of O,O-ligands for the Cu-catalyzed N-arylation of azoles with aryl halides in water or organic solvent

A new type of chelators was identified as efficient ligands for promoting Cu-catalyzed N-arylation of azoles with applicability to different solvents.

Non-peptide NK1 receptor ligands based on the 4-phenylpyridine moiety

The quinoline nucleus of the previously described 4-phenylquinoline-3-carboxamides NK(1) receptor ligands 7 has been transformed into either substituted or azole-(i.e., triazole or tetrazole) fused pyridine moieties of compounds 9 and 10, respectively, in order to obtain NK(1) receptor ligands showing lower molecular weight or higher hydrophilicity. The program of molecular manipulations produced NK(1) receptor ligands showing affinity in the nanomolar range. In particular, 4-methyl-1-piperazinyl derivative 9j showed an IC(50) value of 4.8 nM and was proved to behave as a NK(1) antagonist blocking Sar(9)-SP-sulfone induced proliferation and migration of microvascular endothelial cells. Therefore, compound 9j has been labeled with [(11)C]CH(3)I (t(1/2)=20.4 min, β(+)=99.8%) starting from the corresponding des-methyl precursor 9i using with a radiochemical yield of about 10% (not decay corrected) and a specific radioactivity>1 Ci/μmol in order to be used as a radiotracer in next PET studies.

Divergent effects of quercetin conjugates on angiogenesis

The present study reports the activities of quercetin and its main circulating conjugates in man (quercetin-3'-sulphate (Q3'S) and quercetin-3-glucuronide (Q3G)) on in vivo angiogenesis induced by vascular endothelial growth factor (VEGF) and examines the effects of these molecules on cultured endothelial cells. We found opposing effects of quercetin and its metabolites on angiogenesis. While quercetin and Q3G inhibited VEGF-induced endothelial cell functions and angiogenesis, Q3'S per se promoted endothelial cell proliferation and angiogenesis. The inhibitory effect elicited by Q3G was linked to inhibition of extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation elicited by VEGF. The activation of endothelial cells by Q3'S was associated to stimulation of VEGF receptor-2 and to downstream signalling activation (phosphatidylinositol-3 kinase/Akt and nitric oxide synthase pathways), ultimately responsible for ERK1/2 phosphorylation. These data indicate that the effects of circulating quercetin conjugates on angiogenesis are different depending on the nature of the conjugate. Q3G and Q3'S are the two major conjugates in plasma, but their ratio is dependent on several factors, so that inhibition or activation of angiogenesis could be subtly shifted as a result of metabolism in vivo.