TNP and its analogs: Modulation of IP6K and CYP3A4 inhibition.

Inositol hexakisphosphate kinase (IP6K) is an important mammalian enzyme involved in various biological processes such as insulin signalling and blood clotting. Recent analyses on drug metabolism and pharmacokinetic properties on TNP (N2-(m-trifluorobenzyl), N6-(p-nitrobenzyl)purine), a pan-IP6K inhibitor, have suggested that it may inhibit cytochrome P450 (CYP450) enzymes and induce unwanted drug-drug interactions in the liver. In this study, we confirmed that TNP inhibits CYP3A4 in type I binding mode more selectively than the other CYP450 isoforms. In an effort to find novel purine-based IP6K inhibitors with minimal CYP3A4 inhibition, we designed and synthesised 15 TNP analogs. Structure-activity relationship and biochemical studies, including ADP-Glo kinase assay and quantification of cell-based IP7 production, showed that compound 9 dramatically reduced CYP3A4 inhibition while retaining IP6K-inhibitory activity. Compound 9 can be a tool molecule for structural optimisation of purine-based IP6K inhibitors.

Linoleic acid inhibits Pseudomonas aeruginosa biofilm formation by activating diffusible signal factor-mediated quorum sensing.

Bacterial biofilm formation causes serious problems in various fields of medical, clinical, and industrial settings. Antibiotics and biocide treatments are typical methods used to remove bacterial biofilms, but biofilms are difficult to remove effectively from surfaces due to their increased resistance. An alternative approach to treatment with antimicrobial agents is using biofilm inhibitors that regulate biofilm development without inhibiting bacterial growth. In the present study, we found that linoleic acid (LA), a plant unsaturated fatty acid, inhibits biofilm formation under static and continuous conditions without inhibiting the growth of Pseudomonas aeruginosa. LA also influenced the bacterial motility, extracellular polymeric substance production, and biofilm dispersion by decreasing the intracellular cyclic diguanylate concentration through increased phosphodiesterase activity. Furthermore, quantitative gene expression analysis demonstrated that LA induced the expression of genes associated with diffusible signaling factor-mediated quorum sensing that can inhibit or induce the dispersion of P. aeruginosa biofilms. These results suggest that LA is functionally and structurally similar to a P. aeruginosa diffusible signaling factor (cis-2-decenoic acid) and, in turn, act as an agonist molecule in biofilm dispersion.

Structure-activity relationship studies of dipeptide-based hepsin inhibitors with Arg bioisosteres.

Hepsin is a type II transmembrane serine protease (TTSP) associated with cell proliferation and overexpressed in several types of cancer including prostate cancer (PCa). Because of its significant role in cancer progression and metastasis, hepsin is an attractive protein as a potential therapeutic and diagnostic biomarker for PCa. Based on the reported Leu-Arg dipeptide-based hepsin inhibitors, we performed structural modification and determined in vitro hepsin- and matriptase-inhibitory activities. Comprehensive structure-activity relationship studies identified that the p-guanidinophenylalanine-based dipeptide analog 22a exhibited a strong hepsin-inhibitory activity (Ki = 50.5 nM) and 22-fold hepsin selectivity over matriptase. Compound 22a could be a prototype molecule for structural optimization of dipeptide-based hepsin inhibitors.

Design and synthesis of a novel BODIPY-labeled PSMA inhibitor.

Prostate-specific membrane antigen (PSMA) is a zinc-bound metalloprotease which is highly expressed in metastatic prostate cancer. It has been considered an excellent target protein for prostate cancer imaging and targeted therapy because it is a membrane protein and its active site is located in the extracellular region. We successfully synthesized and evaluated a novel PSMA ligand conjugated with BODIPY650/665. Compound 1 showed strong PSMA-inhibitory activity and selective uptake into PSMA-expressing tumors. Compound 1 has the potential to be utilized as a near infrared (NIR) optical imaging probe targeting PSMA-expressing cancers.

Structure-activity relationship studies of prostate-specific membrane antigen (PSMA) inhibitors derived from α-amino acid with (S)- or (R)-configuration at P1' region.

Prostate-specific membrane antigen (PSMA), a type II membrane glycoprotein, is considered an excellent target for the diagnosis or treatment of prostate cancer. We previously investigated the effect of ß- and γ-amino acids with (S)- or (R)-configuration in the S1 pocket on the binding affinity for PSMA. However, comprehensive studies on the effect of α-amino acid with (R)-configuration in the S1' pocket has not been reported yet. We selected ZJ-43 (1) and DCIBzL (5) as templates and synthesized their analogues with (S)- or (R)-configuration in the P1 and P1' regions. The PSMA-inhibitory activities of compounds with altered chirality in the P1' region were dropped dramatically, with their IC50 values changing from nM to µM ranges. The compounds with (S)-configuration at both P1 and P1' regions were more potent than the others. The findings of this study may provide insights regarding the structural modification of PSMA inhibitor in the S1' binding pocket.

Design and synthesis of dye-conjugated hepsin inhibitors.

Hepsin is a type II serine protease that is highly expressed in neoplastic prostate. It is an attractive biomarker for imaging metastatic prostate cancer because of its overexpression in advanced prostate cancer and the location of its active site on the cell surface. We designed and synthesized novel hepsin-targeted imaging probes by conjugating the hepsin-binding ligand with near-infrared (NIR) optical dyes. The Leu-Arg dipeptides, attached to BODIPY or SulfoCy7, exhibited strong hepsin-inhibitory activities with Ki values of 21 and 22 nM, respectively. Compound 2 showed selective uptake and retention in hepsin-overexpressing cells. This is the first report of hepsin-targeted optical probes with strong binding affinities and high selectivity over matriptase. Compound 2 has the potential to be used for developing hepsin-based imaging probes and be as a prototype molecule in the design of new hepsin inhibitors.

Structure-based design, synthesis, and biological evaluation of Leu-Arg dipeptide analogs as novel hepsin inhibitors.

Hepsin, a type II transmembrane serine protease, is an attractive protein as a potential therapeutic and diagnostic biomarker for prostate cancer because it is highly up-regulated in prostate cancer and promotes both progression and metastasis. Starting from the reported tetrapeptide hepsin inhibitor Ac-KQLR-ketothiazole (kt) (1), we investigated the minimal structural requirements for hepsin inhibitory activity by truncating amino acids at the N-terminus. The kt and ketobenzothiazole (kbt) dipeptide analogs Ac-LR-kt (3) and Ac-LR-kbt (15) were found to be potent hepsin inhibitors, exhibiting Ki values of 22nM and 3nM, respectively. The present work suggests that LR-containing dipeptide molecules could be useful as lead compounds for the development of novel hepsin inhibitors.

Inhibitors of prostate-specific membrane antigen in the diagnosis and therapy of metastatic prostate cancer - a review of patent literature.

INTRODUCTION: Prostate-specific membrane antigen (PSMA), also known as glutamate carboxypeptidase II, is a potential target protein for imaging and treatment of patients with prostate cancer because of its overexpression during metastasis. Various PSMA-targeted imaging and therapeutic probes have been designed and synthesized based on the Lys-urea-Glu motif. Structural modifications have been made exclusively in the linker region, while maintaining the Lys-urea-Glu structure that interacts with S1 and S1' pockets. AREA COVERED: This review includes WIPO-listed patents (from January 2017 to June 2020) reporting PSMA-targeted probes based on the Lys-urea-Glu or Glu-urea-Glu structure. EXPERT OPINION: : PSMA-targeted imaging agents labeled with radionuclides such as fluorine-18, copper-64, gallium-68, and technetium-99m have been successfully translated into clinical phase for the early diagnosis of metastatic prostate cancer. Recently, PSMA-targeted therapeutic agents labeled with iodine-131, lutetium-177, astatine-211, and lead-212 have also been developed with notable progress. Most PSMA-targeted agents are based on the Lys-urea-Glu or Glu-urea-Glu structure, demonstrate strong PSMA-binding affinity in nanomolar range, and achieve diverse structural modifications in the non-pharmacophore pocket. By exploiting the S1 accessory pocket or the tunnel region of the PSMA active site, the in vivo efficacy and pharmacokinetic profiles of the PMSA-targeted agents can be effectively modulated.

Discovery and Characterization of Pure RhlR Antagonists against Pseudomonas aeruginosa Infections.

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic human pathogen that forms biofilms and produces virulence factors via quorum sensing (QS). Blocking the QS system in P. aeruginosa is an excellent strategy to reduce biofilm formation and the production of virulence factors. RhlR plays an essential role in the QS system of P. aeruginosa. We synthesized 55 analogues based on the chemical structure of 4-gingerol and evaluated their RhlR inhibitory activities using the cell-based reporter strain assay. Comprehensive structure-activity relationship studies identified the alkynyl ketone 30 as the most potent RhlR antagonist. This compound displayed selective RhlR antagonism over LasR and PqsR, strong inhibition of biofilm formation, and reduced production of virulence factors in P. aeruginosa. Furthermore, the survival rate of Tenebrio molitor larvae treated with 30 in vivo greatly improved. Therefore, compound 30, a pure RhlR antagonist, can be utilized for developing QS-modulating molecules in the control of P. aeruginosa infections.

Novel ß- and γ-Amino Acid-Derived Inhibitors of Prostate-Specific Membrane Antigen.

Prostate-specific membrane antigen (PSMA) is an excellent biomarker for the early diagnosis of prostate cancer progression and metastasis. The most promising PSMA-targeted agents in the clinical phase are based on the Lys-urea-Glu motif, in which Lys and Glu are α-(l)-amino acids. In this study, we aimed to determine the effect of ß- and γ-amino acids in the S1 pocket on the binding affinity for PSMA. We synthesized and evaluated the ß- and γ-amino acid analogues with (S)- or (R)-configuration with keeping α-(l)-Glu as the S1'-binding pharmacophore. The structure-activity relationship studies identified that compound 13c, a ß-amino acid analogue with (R)-configuration, exhibited the most potent PSMA inhibitory activity with an IC50 value of 3.97 nM. The X-ray crystal structure of PSMA in complex with 13c provided a mechanistic basis for the stereochemical preference of PSMA, which can guide the development of future PSMA inhibitors.

(S)-3-(Carboxyformamido)-2-(3-(carboxymethyl)ureido)propanoic Acid as a Novel PSMA Targeting Scaffold for Prostate Cancer Imaging.

In an effort to seek novel agents targeting prostate-specific membrane antigen (PSMA), 16 ligands (L1-L16) with structural modifications in S1' binding pocket were synthesized and evaluated for PSMA inhibition. (S)-3-(Carboxyformamido)-2-(3-(carboxymethyl)ureido)propanoic acids proved to be potent PSMA ligands with Ki values ranging from 0.08 nM to 8.98 nM, which are in the range of or are higher in potency compared to previously published urea-based ligands. Computational docking was performed to study the binding mode of the two most potent ligands discovered. FITC-conjugated L14 could selectively stain PSMA+ LNCaP cells over PSMA- PC3 cells. IRDye800CW conjugated L16 can effectively image tumors in a murine xenograft model of prostate cancer.

A pathogen-derived metabolite induces microglial activation via odorant receptors.

Microglia (MG), the principal neuroimmune sentinels in the brain, continuously sense changes in their environment and respond to invading pathogens, toxins, and cellular debris, thereby affecting neuroinflammation. Microbial pathogens produce small metabolites that influence neuroinflammation, but the molecular mechanisms that determine whether pathogen-derived small metabolites affect microglial activation of neuroinflammation remain to be elucidated. We hypothesized that odorant receptors (ORs), the largest subfamily of G protein-coupled receptors, are involved in microglial activation by pathogen-derived small metabolites. We found that MG express high levels of two mouse ORs, Olfr110 and Olfr111, which recognize a pathogenic metabolite, 2-pentylfuran, secreted by Streptococcus pneumoniae. These interactions activate MG to engage in chemotaxis, cytokine production, phagocytosis, and reactive oxygen species generation. These effects were mediated through the Gαs -cyclic adenosine monophosphate-protein kinase A-extracellular signal-regulated kinase and Gßγ -phospholipase C-Ca2+ pathways. Taken together, our results reveal a novel interplay between the pathogen-derived metabolite and ORs, which has major implications for our understanding of microglial activation by pathogen recognition. DATABASE: Model data are available in the PMDB database under the accession number PM0082389.

Author Correction: Structure-Activity Relationships of Baicalein and its Analogs as Novel TSLP Inhibitors.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Structure-Activity Relationships of Baicalein and its Analogs as Novel TSLP Inhibitors.

Thymic stromal lymphopoietin (TSLP) plays an important role in the differentiation and proliferation of Th2 cells, resulting in eosinophilic inflammation and numerous allergic diseases. Baicalein (1), a major component of Scutellaria baicalensis, was found to be the first small molecule to block TSLP signaling pathways. It inhibited effectively eosinophil infiltration in house dust mite-induced and ovalbumin-challenged mouse models. Structure-activity relationship studies identified compound 11a, a biphenyl flavanone analog, as a novel human TSLP inhibitor for the discovery and development of new anti-allergic drugs.

Recent Advances of Hepsin-Targeted Inhibitors.

Hepsin is a type II transmembrane serine protease (TTSP) that plays a crucial role in cell growth and development. Hepsin is highly expressed in prostate cancer (PCa) and associated with its progression and metastasis. Therefore, it has been considered as an attractive biomarker of PCa. Recently, low molecular weight inhibitors targeting hepsin have been developed. Based on the key chemical scaffold, they can be classified into four classes: Indolecarboxamidines, benzamidines, peptide-based analogs, and 2,3-dihydro- 1H-perimidines. In this review, we discuss design strategy, structure-activity relationship (SAR), and binding mode of the four classes of hepsin inhibitors.