Search

Although vaccines are obviously mitigating the COVID-19 pandemic diffusion, efficient complementary antiviral agents are urgently needed to combat SARS-CoV-2. The viral papain-like protease (PLpro) is a promising therapeutic target being one of only two essential proteases crucial for viral replication. Nevertheless, it dysregulates the host immune sensing response. Here we report repositioning of the privileged 1,2,4-oxadiazole scaffold as promising SARS-CoV-2 PLpro inhibitor with potential viral entry inhibition profile. The design strategy relied on mimicking the general structural features of the lead benzamide PLpro inhibitor GRL0617 with isosteric replacement of its pharmacophoric amide backbone by 1,2,4-oxadiazole core. Inspired by the multitarget antiviral agents, the substitution pattern was rationalized to tune the scaffold's potency against other additional viral targets, especially the spike receptor binding domain (RBD) that is responsible for the viral invasion . The Adopted facial synthetic protocol allowed easy access to various rationally substituted derivatives. Among the evaluated series, the 2-[5-(pyridin-4-yl)-1,2,4-oxadiazol-3-yl]aniline (5) displayed the most balanced dual inhibitory potential against SARS-CoV-2 PLpro (IC 50= 7.197 μM) and spike protein RBD (IC 50  = 8.673 μM), with acceptable ligand efficiency metrics, practical LogP (3.8) and safety profile on Wi-38 (CC 50  = 51.78 μM) and LT-A549 (CC 50  = 45.77 μM) lung cells. Docking simulations declared the possible structural determinants of activities and enriched the SAR data for further optimization studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

The development of novel therapeutics promoting selective tumor elimination is the mainstay of clinical oncology. Emerging insights into tumor targeting reveal caspases activation, especially caspase-3, as a personalized anticancer strategy. Our on-going cancer research has exploited Passerini α-acyloxy carboxamides as caspase-3/7-dependent apoptotic inducers. Herein, we adopted scaffold hopping design to introduce new series of isoindole-based Passerini adducts as caspase-3/7 activators inspired by natural alkaloids from Lion's Mane mushroom promoting caspase-3-mediated apoptosis. Additional pharmacophoric motifs of lead caspase activators were merged into the tailored Passerini skeleton. The rationally designed adducts were synthesized utilizing one-pot reaction of the novel 4-(2'-phthalimido)phenylisonitrile 5, cyclohexanone and miscellaneous carboxylic acids under Passerini conditions. All derivatives were screened for their antiproliferative activities against lung A549, colorectal Caco-2 and breast MDA-MB 231 cancer cells compared to normal fibroblasts utilizing MTT assay. Most of the evaluated derivatives were superior to 5-fluorouracil. The 2-(1H-indol-3-yl)acetate derivative (8a) recorded the highest anticancer potency (IC 50  = 0.04-0.11 μM) and selectivity (SI = 42.59-125.53), followed by the 3-(4-(trifluoromethyl)phenyl)acrylate (8m), the 2-(phenylsulfonyl)glycinate (8q), and the 2-(2-(3-phenyl-1,2,4-oxadiazol-5-yl)phenoxy)acetate (8c) derivatives, respectively. The four hits induced cancer cells apoptosis (up to 57.99%) via caspase-3/7 activation (up to 5.47 folds). Apoptosis-inducing factor1 (AIF1) quantification assay excluded their caspase-independent apoptosis induction potential via AIF1 signaling pathway. Docking simulations clarified the possible binding modes of the hit compounds with XIAP BIR2 domain; the specific receptor of caspase-3/7 activators, and aided identifying their structural determinants of activity. Finally, their practical LogP, efficiency metrics, in silico ADMET profiling were drug-like., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Harnessing the antioxidant cellular machinery has sparked considerable interest as an efficient anticancer strategy. Activating Nrf2, the master switch of the cellular redox system, suppresses ROS, alleviates oxidative stress, and halts cancer progression. 1,2,4-oxadiazoles are iconic direct Nrf2 activators that disrupt Nrf2 interaction with its endogenous repressor Keap1. This study introduces rationally designed 1,2,4-oxadiazole derivatives that inhibit other Nrf2 suppressors (TrxR1, IKKα, and NF-kB) thus enhancing Nrf2 activation for preventing oxidative stress and carcinogenesis. Preliminary screening showed that the phenolic oxadiazoles 11, 15, and 19 were comparable to ascorbic acid (ROS scavenging) and EDTA (iron chelation), and superior to doxorubicin against HepG-2, MDA-MB231, and Caco-2 cells. They suppressed ROS by 3 folds and activated Nrf2 by 2 folds in HepG-2 cells. Mechanistically, they inhibited TrxR1 (IC 50 ; 13.19, 17.89, and 9.21 nM) and IKKα (IC 50 ; 11.0, 15.94, and 19.58 nM), and downregulated NF-κB (7.6, 1.4 and 1.9 folds in HepG-2), respectively. They inhibited NADPH oxidase (IC 50 ; 16.4, 21.94, and 10.71 nM, respectively) that potentiates their antioxidant activities. Docking studies predicted their important structural features. Finally, they recorded drug-like in silico physicochemical properties, ADMET, and ligand efficiency metrics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Matrix metalloproteinases (MMPs) are major modulators of the tumor microenvironment. They participate in extracellular matrix turnover, tumor growth, angiogenesis and metastasis. Accordingly, MMPs inhibition seems to be ideal solution to control cancer. Many MMPs inhibitors have been introduced ranging from hydroxamate-based peptidomimetics to the next generation non-hydroxamate inhibitors. Among MMPs, MMP-9 is attractive druggable anticancer target. Studies showed that inhibiting AKT, the central signaling node of MMP-9 upregulation, provides additional MMP-9 blockade. Furthermore, caspase-dependent AKT cleavage leads to cell death. Herein, Ugi MCR was utilized as a rapid combinatorial approach to generate various decorated bis-amide scaffolds as dual MMP-9/AKT inhibitors endowed with caspase 3/7 activation potential. The target adducts were designed to mimic the thematic structural features of non-hydroxamate MMP inhibitors. p-Nitrophenyl isonitrile 1 was utilized as structure entry to Ugi products with some structural similarities to amide-based caspase 3/7 activators. Besides, various acids, amines and aldehydes were employed as Ugi educts to enrich the SAR data. All adducts were screened for cytotoxicity against normal fibroblasts and three cancer cell lines; MCF-7, NFS-60 and HepG-2 utilizing MTT assay. 8, 11 and 28 were more active and safer than doxorubicin with single-digit nM IC 50 and promising selectivity. Mechanistically, they exhibited dual MMP-9/AKT inhibition at single-digit nM IC 50 with excellent selectivity over MMP-1,-2 and -13, and induced >51% caspase 3/7 activation. Consequently, they induced >49% apoptosis as detected by flow cytometric analysis, and inhibited cell migration (metastasis) up to 97% in cancer cells. Docking simulations were nearly consistent with enzymatic evaluation, also declared possible binding modes and essential structure features of active compounds. In silico physicochemical properties, ligand efficiency and drug-likeness metrics were reasonable for all adducts. Interestingly, 8 and 28 can be considered as drug-like candidates., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Evasion of apoptosis is a hallmark of cancer. Caspases; the key executors of apoptotic cascade are attractive targets for selective induction of apoptosis in cancer cells. Within this approach, various caspase activators were introduced as lead anticancer agents. In the current study, a new series of multifunctional Passerini products was synthesized and evaluated as potent caspase-dependent apoptotic inducers. The synthetic strategy adopted this isocyanide-based multicomponent reaction to possibly mimic the pharmacophoric features of various lead apoptotic inducers, where a series of α-acyloxy carboxamides was prepared from p-nitrophenyl isonitrile, cyclohexanone and various carboxylic acids. Accordingly, the main amide-based scaffold was decorated by substituents with varying nature and size to gain more information about structure-activity relationship. All the synthesized compounds were screened for cytotoxicity against normal human fibroblasts and their potential anticancer activities against three human cancer cell lines; MCF-7 (breast), NFS-60 (myeloid leukemia), and HepG-2 (liver) utilizing MTT assay. Among the most active compounds, 13, 21 and 22 were more potent and safer than doxorubicin with nanomolar IC 50 values and promising selectivity indices. Mechanistically, 13, 21 and 22 induced apoptosis by significant caspase activation in all the screened cancer cell lines utilizing flow cytometric analysis and caspase 3/7 activation assay. Again, 13 and 21 recorded higher activation percentages than doxorubicin, while 22 showed comparable results. Apoptosis-inducing factor1 (AIF1) quantification assay declared that 13, 21 and 22 didn't mediate apoptosis through AIF1-dependent pathway (i.e. only by caspase activation). Physicochemical properties, pharmacokinetic profiles, ligand efficiency metrics and drug-likeness data of all the synthesized compounds were computationally predicted and showed that 13, 21 and 22 could be considered as drug-like candidates. Finally, selected compounds were preliminarily screened for possible antimicrobial activities searching for dual anticancer/antimicrobial agents as an advantageous approach for cancer therapy., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)