Design, synthesis, and bioactivity evaluation of novel indole-selenide derivatives as P-glycoprotein inhibitors against multi-drug resistance in MCF-7/ADR cell

Design, synthesis, and biological evaluation of C-12 modified ocotillol-type derivatives as novel P-glycoprotein modulators for overcoming multidrug resistance

Ocotillol-type ginsenoside derivatives exhibit significant potential as modulators of P-glycoprotein (Pgp). To date, structural investigations of Ocotillol-type saponins have predominantly focused on modifications at the C-3 position of the A-ring, with limited exploration of the C-12 position on the C-ring. In this study, we designed and synthesized a series of C-12 modified ocotillol-type derivatives and assessed their efficacy in reversing multidrug resistance (MDR) in KBV cells. Most of the newly synthesized derivatives exhibited minimal cytotoxicity and potent MDR reversal capabilities. Notably, compound 9e emerged as the most effective agent in reversing tumor MDR in vitro, showing more than twice the potency of verapamil. Furthermore, 9e displayed high selectivity for Pgp, being 40- and 20-fold more effective than verapamil in inhibiting Rh123 efflux and enhancing doxorubicin sensitivity, respectively. Molecular docking analysis revealed that 9e possesses a unique T-shaped configuration that occupies the access channel of Pgp, obstructing the peristaltic extrusion mechanism of TM12 and TM9, thereby inhibiting the efflux function of Pgp. Overall, 9e represents a promising lead compound for the development of novel Pgp modulators to overcome MDR in cancer therapy.

Optimized ebselen derivatives as novel potent Escherichia coli β-glucuronidase covalent allosteric inhibitors

Gut microbial β-glucuronidase (GUS) plays a key role in metabolizing compounds and influencing disease and drug metabolism, highlighting the need for potent inhibitors to improve drug efficacy and intestinal health. To identify Escherichia coli β-glucuronidase (EcGUS) inhibitors, we designed and synthesized fifty 1,2-benzoselenazol-3-one (BSEA) derivatives using a bioisosterism strategy. Among these, twenty-five BSEA derivatives demonstrated greater inhibitory efficacy than the most potent known EcGUS inhibitor, amoxapine (AMX), with compound 49 showing the strongest activity, achieving an IC50 of 12.9 nM. Structure-inhibitory activity relationship analysis suggested that modifications such as adding benzene rings or nitrogenous heterocycles to the BSEA scaffold enhanced inhibitory activity, influenced by the type and position of substituents. The LC-MS analysis confirmed that compounds 31 and 49 covalently modify Cys197 in EcGUS, and additional covalent linkage of compound 49 was observed on Cys28 and Cys443. In addition, the jump dilution assays proved that compounds 31 was irreversible covalent inhibitors, and its kinetic parameter kinact/KI were determined to be 21292.9 M-1s-1. The compounds 49 was reversible covalent inhibitors and its apparent steady-state inhibition constant Ki∗app were determined to be 23.33 nM. Molecular docking predicted specific interactions, such as hydrogen bonds involving Se and the pyrazole NH of compound 49 with Cys28 and Cys449, which may contribute to its inhibitory action. This study reports the first discovery of covalent inhibitors for EcGUS, with optimized BSEA derivatives acting as novel allosteric covalent inhibitors, revealing structure-activity relationships and molecular determinants that establish their potential in drug development.

Multicomponent Reaction Integrating Selenium(II)-Nitrogen Exchange (SeNEx) Chemistry and Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC)

Multicomponent reactions (MCRs) are powerful tools for rapidly constructing compound libraries with sufficient molecular diversity and complexity. Herein, to fully leverage a third aspect of molecular diversity enabled by the selenium-nitrogen exchange (SeNEx) reaction between alkynes and benzoselenazolones, a novel CuI-catalyzed three-component reaction has been successfully developed. This reaction integrates SeNEx with CuAAC click chemistry, enabling rapid and regioselective synthesis of 1,4,5-trisubstituted 5-seleno-1,2,3-triazoles with high atom economy and good to excellent yields (65 examples, 50%-95%). Notably, this MCR demonstrates excellent functional group tolerance and features modular, predictable, robust, mild reaction conditions, and operational simplicity (air and water compatibility). Extensive mechanism studies have revealed that this reaction proceeds by a unique SeNEx-CuAAC tandem reaction pathway, distinguishing it from conventional copper(I)-catalyzed interrupted click reactions. Importantly, a mononuclear σ-bound copper(I)-acetylide Cu1 was synthesized and confirmed to be an efficient catalyst for the SeNEx reaction. This discovery provides crucial mechanistic insights into the preferential reactivity of alkynyl groups toward SeNEx over CuAAC. Furthermore, preliminary biological activity screening identified compound 14 as a potent inhibitor of Escherichia coli β $\upbeta$ -glucuronidase (EcGUS), with an IC50 value of 3.16 µM. These findings underscore the significant potential of this MCR in synthetic chemistry, medical chemistry, and chemical biology.

Spiroindoline quinazolinedione derivatives as inhibitors of P-glycoprotein: potential agents for overcoming multidrug resistance in cancer therapy

Multidrug resistance (MDR) presents a major challenge for effectiveness of chemotherapy. This study investigates the effectiveness of spiroindoline quinazolinediones in reversing MDR mediated by P-glycoprotein (P-gp) overexpression in cancer cells. A series of synthesized hybrid spiro[indoline-3,2'-quinazoline]-2,4'(3'H)-dione derivatives (compounds 5a-5l) were analyzed for their ability to enhance rhodamine 123 (Rhd123) accumulation in the MES-SA/DX5 cell line using flow cytometry. The MTT assay was also employed to evaluate the compounds' effectiveness in reversing drug resistance. Additionally, docking studies and molecular dynamics simulations were conducted to investigate the interaction of these compounds with the P-gp transporter. The Rhd123 accumulation assay in MDR cancer cells revealed that most compounds, in particular 5f, 5g, 5h, 5i, 5j, 5k, and 5l, exhibited significant potential as P-gp inhibitors. Among the tested derivatives, compounds 5g and 5l demonstrated the best effects, and increased Rhd123 accumulation up to 12.9 times compared to untreated cells. Additionally, compounds 5f through 5 l bearing methylbenzyl (5f), benzyl (5g), pentyl (5 ), p-bromobenzyl (5i), p-chlorobenzyl (5j), dichlorobenzyl (5k), and tert-butylbenzyl (5l) substituents on the isatin ring effectively restored sensitivity to doxorubicin at their non-toxic concentrations in resistant MES-SA/DX5 cells. Among these, compound 5l at 5 μM exhibited the highest inhibitory potential, and lowered doxorubicin's IC50 value 10.1 times compared to control. Moreover, in silico investigation identified the potential interactions of test compounds with critical residues of P-gp involved in its efflux function. Our study suggests that the synthesized spiroindoline quinazolinediones may have high potentials as agents capable of reversing MDR in cancer cells.

Selenium(II)-Nitrogen Exchange (SeNEx) Chemistry: A Good Chemistry Suitable for Nanomole-Scale Parallel Synthesis, DNA-encoded Library Synthesis and Bioconjugation

The continuous development of click reactions with new connecting linkage is crucial for advancing the frontiers of click chemistry. Selenium-nitrogen exchange (SeNEx) chemistry, a versatile chemistry in click chemistry, represents an all-encompassing term for nucleophilic substitution events that replace nitrogen at an electrophilic selenium(II) center, enabling the flexible and efficient assembly of linkages around a Se(II) core. Several SeNEx chemistries have been developed inspired by the biochemical reaction between Ebselen and cysteine residue, and demonstrated significant potential in on-plate nanomole-scale parallel synthesis, selenium-containing DNA-encoded library (SeDEL) synthesis, as well as peptide and protein bioconjugation. This concept aims to present the origins, advancements, and applications of selenium(II)-nitrogen exchange (SeNEx) chemistry while also outlining the potential directions for future research in this field.

Organoselenium compounds beyond antioxidants

Organoselenium chemistry has become a significant field due to its role in synthesizing numerous biologically active and therapeutic compounds. In early phase, researchers focused on designing organoselenium compounds with antioxidant properties and were quite successful. In last two decades, synthetic chemists shifted their focus toward synthesis of organoselenium compounds with biological properties, moving beyond their traditional antioxidant properties. The review includes synthesis and study of organo-selenium compounds as anticancer, antimicrobial, antiviral, antidiabetic, antithyroid, anti-inflammatory therapies, contributing to disease treatment. This review covers the synthesis and medicinal applications of synthetic organoselenium compounds over the past 10 years, thus making it a valuable resource for researchers in the field of medicinal chemistry.

Discovery of novel pyrazolo[1,5-a]pyrimidine derivatives as potent reversal agents against ABCB1-mediated multidrug resistance

The P-glycoprotein (ABCB1)-mediated multidrug resistance (MDR) has emerged as a significant impediment to the efficacy of cancer chemotherapy in clinical therapy, which could promote the development of effective agents for MDR reversal. In this work, we reported the exploration of novel pyrazolo [1,5-a]pyrimidine derivatives as potent reversal agents capable of enhancing the sensitivity of ABCB1-mediated MDR MCF-7/ADR cells to paclitaxel (PTX). Among them, compound 16q remarkably increased the sensitivity of MCF-7/ADR cells to PTX at 5 μM (IC50 = 27.00 nM, RF = 247.40) and 10 μM (IC50 = 10.07 nM, RF = 663.44). Compound 16q could effectively bind and stabilize ABCB1, and does not affect the expression and subcellular localization of ABCB1 in MCF-7/ADR cells. Compound 16q inhibited the function of ABCB1, thereby increasing PTX accumulation, and interrupting the accumulation and efflux of the ABCB1-mediated Rh123, thus resulting in exhibiting good reversal effects. In addition, due to the potent reversal effects of compound 16q, the abilities of PTX to inhibit tubulin depolymerization, and induce cell cycle arrest and apoptosis in MCF-7/ADR cells under low-dose conditions were restored. These results indicate that compound 16q might be a promising potent reversal agent capable of revising ABCB1-mediated MDR, and pyrazolo [1,5-a]pyrimidine might represent a novel scaffold for the discovery of new ABCB1-mediated MDR reversal agents.

Discovery of new tricyclic spiroindole derivatives as potent P-glycoprotein inhibitors for reversing multidrug resistance enabled by a synthetic methodology-based library

The discovery of novel and highly effective P-gp inhibitors is considered to be an effective strategy for overcoming tumor drug resistance. In this paper, a phenotypic screening via a self-constructed synthetic methodology-based library identified a new class of tricyclic spiroindole derivatives with excellent tumor multidrug resistance reversal activity. A stereospecific compound OY-103-B with the best reversal activity was obtained based on a detailed structure-activity relationship study, metabolic stability optimization and chiral resolution. For the VCR-resistant Eca109 cell line (Eca109/VCR), co-administration of 5.0 μM OY-103-B resulted in a reversal fold of up to 727.2, superior to the typical third-generation P-gp inhibitor tariquidar. Moreover, the compound inhibited the proliferation of Eca109/VCR cells in a concentration-dependent manner in plate cloning and flow cytometry. Furthermore, fluorescence substrate accumulation assay and chemotherapeutic drug reversal activity tests demonstrated that OY-103-B reversed tumor drug resistance via P-gp inhibition. In conclusion, this study provides a novel skeleton that inspires the design of new P-gp inhibitors, laying the foundation for the treatment of drug-resistant tumors.