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Live-cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real-time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase-2 (COX-2). We developed celecoxib-azide derivative 14, possessing favorable biophysical properties and excellent COX-2 selectivity profile. In cellulo strain-promoted fluorogenic click chemistry of COX-2-engaged compound 14 with non/weakly-fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX-2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein-ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX-2 in live cells with superior sensitivity in the visible range., (© 2020 Wiley-VCH GmbH.)

Cyclooxygenase-2 isozyme is a promising anti-inflammatory drug target, and overexpression of this enzyme is also associated with several cancers and neurodegenerative diseases. The amino-acid sequence and structural similarity between inducible cyclooxygenase-2 and housekeeping cyclooxygenase-1 isoforms present a significant challenge to design selective cyclooxygenase-2 inhibitors. Herein, we describe the use of the cyclooxygenase-2 active site as a reaction vessel for the in situ generation of its own highly specific inhibitors. Multi-component competitive-binding studies confirmed that the cyclooxygenase-2 isozyme can judiciously select most appropriate chemical building blocks from a pool of chemicals to build its own highly potent inhibitor. Herein, with the use of kinetic target-guided synthesis, also termed as in situ click chemistry, we describe the discovery of two highly potent and selective cyclooxygenase-2 isozyme inhibitors. The in vivo anti-inflammatory activity of these two novel small molecules is significantly higher than that of widely used selective cyclooxygenase-2 inhibitors.Traditional inflammation and pain relief drugs target both cyclooxygenase 1 and 2 (COX-1 and COX-2), causing severe side effects. Here, the authors use in situ click chemistry to develop COX-2 specific inhibitors with high in vivo anti-inflammatory activity.

The copper-free click chemistry reaction between norbornene and tetrazine species is known to proceed in a rapid, reliable and selective manner under mild conditions. Due to these attractive properties, this reaction has recently been explored as a generally applicable method of bioconjugation. Here, we report a convenient synthetic procedure towards a novel (18)F-labelled norbornene derivative ([(18)F]NFB) and have evaluated its ability to undergo strain-promoted copper-free click chemistry reactions with two model tetrazine species: an asymmetric dipyridyl tetrazine derivative (Tz) and a tetrazine thiourea-coupled stabilised bombesin peptide (TT-BBN). In both cases, [(18)F]NFB was found to undergo rapid and high-yielding click chemistry reactions. Furthermore, as reactions of this type could also potentially be used in vivo to facilitate the development of a novel pretargeting approach for tumour imaging and therapy, we have also assessed the radiopharmacological profile (bioavailability, biodistribution, blood clearance and metabolic stability) of [(18)F]NFB in normal BALB/c mice. This radiolabelled compound exhibits both high bioavailability and metabolic stability with approximately 90% remaining intact up to 30 min following administration.

Live‐cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real‐time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase‐2 (COX‐2). We developed celecoxib‐azide derivative 14, possessing favorable biophysical properties and excellent COX‐2 selectivity profile. In cellulo strain‐promoted fluorogenic click chemistry of COX‐2‐engaged compound 14 with non/weakly‐fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX‐2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein‐ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX‐2 in live cells with superior sensitivity in the visible range. [ABSTRACT FROM AUTHOR]

The first application of sulfo-click chemistry with 18F-labeled thio acids is described. The simple one-pot/three-component reaction proceeded rapidly within 30 min using mild reaction conditions to give various 18F-labeled small molecule N-acylsulfonamides in radiochemical conversions of 38–99%, and radiolabeled peptides in 20–25% isolated and decay-corrected radiochemical yields. [ABSTRACT FROM AUTHOR]

Abstract: A series of 1,4- and 1,5-diaryl substituted 1,2,3-triazoles was synthesized by either Cu(I)-catalyzed or Ru(II)-catalyzed 1,3-dipolar cycloaddition reactions between 1-azido-4-methane-sulfonylbenzene 9 and a panel of various para-substituted phenyl acetylenes (4-H, 4-Me, 4-OMe, 4-NMe2, 4-Cl, 4-F). All compounds were used in in vitro cyclooxygenase (COX) assays to determine the combined electronic and steric effects upon COX-1 and COX-2 inhibitory potency and selectivity. Structure-activity relationship studies showed that compounds having a vicinal diaryl substitution pattern showed more potent COX-2 inhibition (IC50 =0.03–0.36μM) compared to their corresponding 1,3-diaryl-substituted counterparts (IC50 =0.15 to >10.0μM). In both series, compounds possessing an electron-withdrawing group (Cl and F) at the para-position of one of the aryl rings displayed higher COX-2 inhibition potency and selectivity as determined for compounds containing electron-donating groups (Me, OMe, NMe2). The obtained data show, that the central carbocyclic or heterocyclic ring system as found in many COX-2 inhibitors can be replaced by a central 1,2,3-triazole unit without losing COX-2 inhibition potency and selectivity. The high COX-2 inhibition potency of some 1,2,3-triazoles having a vicinal diaryl substitution pattern along with their ease in synthesis through versatile Ru(II)-catalyzed click chemistry make this class of compounds interesting candidates for further design and synthesis of highly selective and potent COX-2 inhibitors. [Copyright &y& Elsevier]

Cover Feature: In Cellulo Generation of Fluorescent Probes for Live-Cell Imaging of Cylooxygenase-2 (Chem. Eur. J. 10/2021) Keywords: cancer; drug design; fluorescence; fluorogenic click chemistry; imaging agents; live cell imaging EN cancer drug design fluorescence fluorogenic click chemistry imaging agents live cell imaging 3189 3189 1 02/17/21 20210215 NES 210215 B In cellulo generation of fluorescent probes b is an essential tool in chemical biology to visualize the dynamics of biological processes in real-time. Cancer, drug design, fluorescence, fluorogenic click chemistry, imaging agents, live cell imaging. [Extracted from the article]

The study describes for the first time the application of Cu(I)-mediated 1,3-dipolar [3+2]cycloaddition for the labelling of proteins with the short-lived positron emitter fluorine-18 as exemplified with azide-functionalized human serum albumin (HSA). [ABSTRACT FROM AUTHOR]

Abstract: A novel group of 1,4-diaryl-substituted triazoles was designed and synthesized by introducing the cyclooxygenase-2 (COX-2) pharmacophore SO2NH2 attached to one aryl ring and various substituents (H, F, Cl, CH3 or OCH3) attached to the other aryl ring. The effects of size and flexibility of the compounds upon COX-1/COX-2 inhibitory potency and selectivity was studied by increasing the size of an alkyl linker chain [(–CH2) n , where n =0, 1, 2]. In vitro COX-1/COX-2 inhibition studies showed that all compounds (14–18, 21–25 and 28–32) are more potent inhibitors of COX-2 isozyme (IC50 =0.17–28.0μM range) compared to COX-1 isozyme (IC50 =21.0 to >100μM range). Within the group of 1,4 diaryl-substituted triazoles, 4-{2-[4-(4-chloro-phenyl)-[1,2,3]triazol-1-yl]-ethyl}-benzenesulfonamide (compound 30) displayed highest COX-2 inhibitory potency and selectivity (COX-1: IC50 =>100μM, COX-2: IC50 =0.17μM, SI >588). Molecular docking studies using the catalytic site of COX-1 and COX-2, respectively, provided complementary theoretical support for the obtained experimental biological structure–activity relationship data. Results of molecular docking studies revealed that COX-2 pharmacophore SO2NH2 in compound 30 is positioned in the secondary pocket of COX-2 active site; with the nitrogen atom of the SO2NH2 group being hydrogen bonded to Q192 (N⋯O C=2.85Å), and one of the oxygen atoms of SO2NH2 group forming a hydrogen bond to H90 (S O⋯N=2.38Å). [Copyright &y& Elsevier]

Abstract: Two neurotensin(8–13)-containing peptide heterodimers were prepared via copper(I)-mediated click chemistry. The resulting peptide dimers could be obtained in 28–31% yield after HPLC purification. Neurotensin(8–13)-containing peptide dimers were used in an in vitro binding assay to determine binding affinity towards the neurotensin receptor-1 (NTR1). The determined IC50 values of 8.3μM and 0.7μM indicate only very low binding affinity of the neurotensin(8–13)-containing peptide heterodimers towards the NTR1. [Copyright &y& Elsevier]