Design, synthesis and evaluation of 1,2-benzisothiazol-3-one derivatives as potent caspase-3 inhibitors

Synthesis, in silico modelling, and in vitro biological evaluation of substituted pyrazole derivatives as potential anti-skin cancer, anti-tyrosinase, and antioxidant agents

Twenty-five azole compounds (P1-P25) were synthesised using regioselective base-metal catalysed and microwave-assisted approaches, fully characterised by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and infrared spectra (IR) analyses, and evaluated for anticancer, anti-tyrosinase, and anti-oxidant activities in silico and in vitro. P25 exhibited potent anticancer activity against cells of four skin cancer (SC) lines, with selectivity for melanoma (A375, SK-Mel-28) or non-melanoma (A431, SCC-12) SC cells over non-cancerous HaCaT-keratinocytes. Clonogenic, scratch-wound, and immunoblotting assay data were consistent with anti-proliferative results, expression profiling therewith implicating intrinsic and extrinsic apoptosis activation. In a mushroom tyrosinase inhibition assay, P14 was most potent among the compounds (half-maximal inhibitory concentration where 50% of cells are dead, IC50 15.9 μM), with activity greater than arbutin and kojic acid. Also, P6 exhibited noteworthy free radical-scavenging activity. Furthermore, in silico docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) simulations predicted prominent-phenotypic actives to engage diverse cancer/hyperpigmentation-related targets with relatively high affinities. Altogether, promising early-stage hits were identified - some with multiple activities - warranting further hit-to-lead optimisation chemistry with further biological evaluations, towards identifying new skin-cancer and skin-pigmentation renormalising agents.

Design, synthesis, cytotoxic activities, and molecular docking of chalcone hybrids bearing 8-hydroxyquinoline moiety with dual tubulin/EGFR kinase inhibition

The present study established thirteen novel 8-hydroxyquinoline/chalcone hybrids3a-mof hopeful anticancer activity. According to NCI screening and MTT assay results, compounds3d-3f, 3i,3k,and3ldisplayed potent growth inhibition on HCT116 and MCF7 cells compared to Staurosporine. Among these compounds,3eand3fshowed outstanding superior activity against HCT116 and MCF7 cells and better safety toward normal WI-38 cells than Staurosporine. The enzymatic assay revealed that3e,3d, and3ihad goodtubulin polymerization inhibition (IC₅₀ = 5.3, 8.6, and 8.05 µM, respectively) compared to the reference Combretastatin A4 (IC₅₀ = 2.15 µM). Moreover,3e,3l, and3fexhibited EGFR inhibition (IC₅₀ = 0.097, 0.154, and 0.334 µM, respectively) compared to Erlotinib (IC₅₀ = 0.056 µM). Compounds3eand3fwere investigated for their effects on the cell cycle, apoptosis induction, andwnt1/β-cateningene suppression. The apoptosis markers Bax, Bcl2, Casp3, Casp9, PARP1, and β-actin were detected by Western blot. In-silico molecular docking, physicochemical, and pharmacokinetic studies were implemented for the validation of dual mechanisms and other bioavailability standards. Hence, Compounds3eand3fare promising antiproliferative leads with tubulin polymerization and EGFR kinase inhibition.

Discovery and mechanism studies of a novel ATG4B inhibitor Ebselen by drug repurposing and its anti-colorectal cancer effects in mice

Cysteine protease ATG4B, a key autophagy protein, is an attractive target for colorectal cancer therapy. However, ATG4B inhibitors with higher efficiency, safety, and clear mechanism are still limited. In this study, we discovered ATG4B inhibitors based on the FDA-approved drug library through FRET-based high-throughput screening and gel-based analysis. Among the nine hits, compound Ebselen showed the most potent ATG4B inhibitory activity (IC₅₀ = 189 nM) and exhibited controllable selectivity and structural optimizable possibility against ATG4A and caspases. We then performed mass spectrometry assay and cysteine mutations to confirm that Ebselen could covalently bind to ATG4B at Cys74. Moreover, Cys292 and Cys361 instead of Cys74 are responsible for the redox-oligomerization and efficient activity inhibition of ATG4B. Ultimately through cell culture and mouse xenograft tumor models, we established the impact of Ebselen on autophagy and tumor suppression via ATG4B inhibition other than apoptosis. These results suggest that old drug Ebselen as an ATG4B inhibitor through oxidative modification may be repurposed as a promising anti-colorectal cancer drug.

BTZ-Derived Benzisothiazolinones with In Vitro Activity against Mycobacterium tuberculosis

8-Nitro-1,3-benzothiazin-4-ones (BTZs) are known as potent antitubercular agents. BTZ043 as one of the most advanced compounds has reached clinical trials. The putative oxidation products of BTZ043, namely, the corresponding BTZ sulfoxide and sulfone, were reported in this journal (Tiwari et al. ACS Med. Chem Lett. 2015, 6, 128-133). The molecular structures were later revised to the constitutionally isomeric benzisothiazolone and its 1-oxide, respectively. Here, we report two BTZ043-derived benzisothiazolinones (BITs) with in vitro activity against mycobacteria. The constitutionally isomeric O-acyl benzisothiazol-3-ols, in contrast, show little or no antimycobacterial activity in vitro. The structures of the four compounds were investigated by X-ray crystallography and NMR spectroscopy. Molecular covalent docking of the new compounds to Mycobacerium tuberculosis decaprenylphosphoryl-β-d-ribose 2'-epimerase (DprE1) suggests that the active BITs exert antimycobacterial activity through inhibition of DprE1 like BTZs.

Interleukin-18 Inhibition Protects Against Intervertebral Disc Degeneration via the Inactivation of Caspase-3/9 Dependent Apoptotic Pathways

BACKGROUND

The present study was designed to identify and understand the potential effectiveness of therapeutic target in intervertebral disc degeneration (IVDD) and its regulation mechanism.

METHODS

The role and mechanism of interleukin-18 (IL-18) in the disease were investigated. The IVDD degenerative nucleus pulposus (NP) tissues from the human and mouse models were used.A total of three groups of Male BALB/c mice were randomly made i.e control, IVDD, and IVDD+Ad-shIL-18 groups. After Ad-shIL-18 transfection, the expression of ECM synthesis related protein Aggrecan (ACAN) and Collagen II, apoptotic effector Caspases (Caspase-3, 8, 9, 12 and Cleaved-Caspase 3, 8, 9, 12), pro-apoptotic gene Bax and anti-apoptotic factors Bcl-2 in NP cells of the human were evaluated.

RESULTS

The results of our study revealed that the mRNA and protein expression levels of IL-18 were notably increased in the NP tissues of IVDD patients and mice models. In the IVDD mice model, Ad-sh-IL-18 treatment reversed the IVDD progression. The levels of Aggrecan and Collagen II, contributing to ECM degradation in NP cells, were also significantly increased. Additionally, Ad-sh-IL-18 could inhibit the NP cell's apoptosis via regulating the caspase-3/9 pathway.

CONCLUSION

The IL-18 knockdown via the caspase-3/9 pathway, might reduce the NP cell's death as well as the imbalance between catabolism and anabolism of ECM in IVDD.

Synthesis and Evaluation of Structurally Diverse C-2-Substituted Thienopyrimidine-Based Inhibitors of the Human Geranylgeranyl Pyrophosphate Synthase

Novel analogues of C-2-substituted thienopyrimidine-based bisphosphonates (C2-ThP-BPs) are described that are potent inhibitors of the human geranylgeranyl pyrophosphate synthase (hGGPPS). Members of this class of compounds induce target-selective apoptosis of multiple myeloma (MM) cells and exhibit antimyeloma activity in vivo. A key structural element of these inhibitors is a linker moiety that connects their (((2-phenylthieno[2,3-d]pyrimidin-4-yl)amino)methylene)bisphosphonic acid core to various side chains. The structural diversity of this linker moiety, as well as the side chains attached to it, was investigated and found to significantly impact the toxicity of these compounds in MM cells. The most potent inhibitor identified was evaluated in mouse and rat for liver toxicity and systemic exposure, respectively, providing further optimism for the potential value of such compounds as human therapeutics.

Structure-Guided Discovery of the Novel Covalent Allosteric Site and Covalent Inhibitors of Fructose-1,6-Bisphosphate Aldolase to Overcome the Azole Resistance of Candidiasis

Fructose-1,6-bisphosphate aldolase (FBA) represents an attractive new antifungal target. Here, we employed a structure-based optimization strategy to discover a novel covalent binding site (C292 site) and the first-in-class covalent allosteric inhibitors of FBA from Candida albicans (CaFBA). Site-directed mutagenesis, liquid chromatography-mass spectrometry, and the crystallographic structures of APO-CaFBA, CaFBA-G3P, and C157S-2a4 revealed that S268 is an essential pharmacophore for the catalytic activity of CaFBA, and L288 is an allosteric regulation switch for CaFBA. Furthermore, most of the CaFBA covalent inhibitors exhibited good inhibitory activity against azole-resistant C. albicans, and compound 2a11 can inhibit the growth of azole-resistant strains 103 with the MIC₈₀ of 1 μg/mL. Collectively, this work identifies a new covalent allosteric site of CaFBA and discovers the first generation of covalent inhibitors for fungal FBA with potent inhibitory activity against resistant fungi, establishing a structural foundation and providing a promising strategy for the design of potent antifungal drugs.

Inhibitors of HIV-1 Nef-Mediated Activation of the Myeloid Src-Family Kinase Hck Block HIV-1 Replication in Macrophages and Disrupt MHC-I Downregulation

HIV-1 Nef is an attractive target for antiretroviral drug discovery because of its role in promoting HIV-1 infectivity, replication, and host immune system avoidance. Here, we applied a screening strategy in which recombinant HIV-1 Nef protein was coupled to activation of the Src-family tyrosine kinase Hck, which enhances the HIV-1 life cycle in macrophages. Nef stimulates recombinant Hck activity in vitro, providing a robust assay for chemical library screening. High-throughput screening of more than 730 000 compounds using the Nef·Hck assay identified six unique hit compounds that bound directly to recombinant Nef by surface plasmon resonance (SPR) in vitro and inhibited HIV-1 replication in primary macrophages in the 0.04 to 5 μM range without cytotoxicity. Eighty-four analogs were synthesized around an isothiazolone scaffold from this series, many of which bound to recombinant Nef and inhibited HIV-1 infectivity in the low to submicromolar range. Compounds in this series restored MHC-I to the surface of HIV-infected primary cells and disrupted a recombinant protein complex of Nef with the C-terminal tail of MHC-I and the μ1 subunit of the AP-1 endocytic trafficking protein. Nef inhibitors in this class have the potential to block HIV-1 replication in myeloid cells and trigger recognition of HIV-infected cells by the adaptive immune system in vivo.

Hemorrhage-Induced Sphingosine Kinase 1 Contributes to Ferroptosis-Mediated Secondary Brain Injury in Intracerebral Hemorrhage

The pathogenic processes of brain injury after intracerebral hemorrhage (ICH) have not yet been fully elucidated. Increasing evidence suggests that ferroptosis activation aggravates injury after ICH, but the underlying mechanism remains unclear. Sphingosine kinase 1 (Sphk1) is a key enzyme in the regulation of sphingosine metabolism involved in the ferroptosis pathway, but its role in ICH needs clarification. In this study, transcriptional changes in ICH patients were assessed by microarray data, exposing Sphk1 as a highly upregulated gene during ICH. Furthermore, Sphk1 chemical inhibitors and siRNA were used to inhibit ICH-induced Sphk1 upregulation in in vivo and in vitro models, showing that Sphk1 inhibition after protects against ferroptosis and attenuates secondary brain injury and cell death. Mechanistically, this study unveiled that sphingosine kinase 1/sphingosine 1-phosphate/extracellular-regulated protein kinases/phosphorylated extracellular-regulated protein kinases (Sphk1/S1p/ERK/p-ERK) pathway is responsible for regulation of ferroptosis leading to secondary brain injury and cell death following ICH. Collectively, this study demonstrates that ferroptosis is closely associated with ICH, and that Sphk1 has a critical role in this lethal process. These results suggest a novel unique and effective therapeutic approach for ICH prevention and treatment.

Silica nanoparticles inducing the apoptosis via microRNA-450b-3p targeting MTCH2 in mice and spermatocyte cell

Silica nanoparticles (SiNPs) could cause reproductive toxicity. The role of miRNAs in reproductive toxicity induced by SiNPs is still ambiguous. The present study was designed to investigate the role of miRNA-450 b-3p. In vivo, 40 male mice were randomly divided into control, and 20 mg/kg SiNPs groups. The mice were administrated by tracheal perfusion for 35 days. In vitro, spermatocyte cells (GC-2spd cells) were divided into 6 groups: 0 μg/mL SiNPs groups, 5 μg/mL SiNPs groups, 5 μg/mL SiNPs + miRNA-450 b-3p mimic transfection group, 5 μg/mL SiNPs + miRNA-450 b-3p mimic negative control group, 5 μg/mL SiNPs + miRNA-450 b-3p inhibitor transfection group, and 5 μg/mL SiNPs + miRNA-450 b-3p inhibitor negative control group. The results showed that SiNPs induced the apoptosis of spermatogenic cells, decreased the quantity and quality of the sperm, reduced the expressions of miR-450 b-3p, and increased the protein expressions of the MTCH2, BID, BAX, Cytochrome C, Caspase-9, and Caspase-3 in the testis. In vitro, the mimic of miRNA-450 b-3p reversed the decrease of viability and the increase of apoptosis rate and significantly antagonized the expression enhancements of the MTCH2, BID, BAX, Cytochrome C, Caspase-9, Caspase-3 induced by SiNPs, while inhibitor of miRNA-450 b-3p further promoted the effects induced by SiNPs. The result suggested that SiNPs could inhibit the miR-450 b-3p expression resulting in activation of the mitochondrial apoptosis signaling pathways by regulating the MTCH2 in the spermatocyte cells and, thus, induce the reproductive toxicity.

Targeting Chikungunya Virus Replication by Benzoannulene Inhibitors

A benzo[6]annulene, 4-(tert-butyl)-N-(3-methoxy-5,6,7,8-tetrahydronaphthalen-2-yl) benzamide (1a), was identified as an inhibitor against Chikungunya virus (CHIKV) with antiviral activity EC₉₀ = 1.45 μM and viral titer reduction (VTR) of 2.5 log at 10 μM with no observed cytotoxicity (CC₅₀ = 169 μM) in normal human dermal fibroblast cells. Chemistry efforts to improve potency, efficacy, and drug-like properties of 1a resulted in a novel lead compound 8q, which possessed excellent cellular antiviral activity (EC₉₀ = 270 nM and VTR of 4.5 log at 10 μM) and improved liver microsomal stability. CHIKV resistance to an analog of 1a, compound 1c, tracked to a mutation in the nsP3 macrodomain. Further mechanism of action studies showed compounds working through inhibition of human dihydroorotate dehydrogenase in addition to CHIKV nsP3 macrodomain. Moderate efficacy was observed in an in vivo CHIKV challenge mouse model for compound 8q as viral replication was rescued from the pyrimidine salvage pathway.

Synthesis, inverse docking-assisted identification and in vitro biological characterization of Flavonol-based analogs of fisetin as c-Kit, CDK2 and mTOR inhibitors against melanoma and non-melanoma skin cancers

Due to hurdles, including resistance, adverse effects, and poor bioavailability, among others linked with existing therapies, there is an urgent unmet need to devise new, safe, and more effective treatment modalities for skin cancers. Herein, a series of flavonol-based derivatives of fisetin, a plant-based flavonoid identified as an anti-tumorigenic agent targeting the mammalian targets of rapamycin (mTOR)-regulated pathways, were synthesized and fully characterized. New potential inhibitors of receptor tyrosine kinases (c-KITs), cyclin-dependent kinase-2 (CDK2), and mTOR, representing attractive therapeutic targets for melanoma and non-melanoma skin cancers (NMSCs) treatment, were identified using inverse-docking, in vitro kinase activity and various cell-based anticancer screening assays. Eleven compounds exhibited significant inhibitory activities greater than the parent molecule against four human skin cancer cell lines, including melanoma (A375 and SK-Mel-28) and NMSCs (A431 and UWBCC1), with IC50 values ranging from 0.12 to < 15 μM. Seven compounds were identified as potentially potent single, dual or multi-kinase c-KITs, CDK2, and mTOR kinase inhibitors after inverse-docking and screening against twelve known cancer targets, followed by kinase activity profiling. Moreover, the potent compound F20, and the multi-kinase F9 and F17 targeted compounds, markedly decreased scratch wound closure, colony formation, and heightened expression levels of key cancer-promoting pathway molecular targets c-Kit, CDK2, and mTOR. In addition, these compounds downregulated Bcl-2 levels and upregulated Bax and cleaved caspase-3/7/8 and PARP levels, thus inducing apoptosis of A375 and A431 cells in a dose-dependent manner. Overall, compounds F20, F9 and F17, were identified as promising c-Kit, CDK2 and mTOR inhibitors, worthy of further investigation as therapeutics, or as adjuvants to standard therapies for the control of melanoma and NMSCs.

Silencing myelin protein zero-like 1 expression suppresses cell proliferation and invasiveness of human glioma cells by inhibiting multiple cancer-associated signal pathways

Glioma is the most common primary malignant tumor of the adult central nervous system. It has high morbidity and poor survival. Myelin protein zero-like protein 1 (MPZL1) is a cell surface glycoprotein that activates numerous adhesion-dependent signaling pathways. MPZL1 plays important roles in human cancers that include metastatic process; however, it is not clear if MPZL1 plays a role in human glioma. Therefore, this study aimed to determine if silencing MPZL1 impacted the cell proliferative features of human glioma cells. First, MPZL1 expression was investigated in human glioma samples and tumor cell lines. Then the effects of small interfering RNA (siRNA)-targeting MPZL1 were analyzed on proliferation, colony formation, cell cycle progression, and invasion of human glioma cells. The results from this study demonstrated that MPZL1 was highly expressed in human glioma tissues and glioma cell lines. In addition, knockdown of MPZL1 significantly inhibited cell proliferation, colony formation, and invasiveness of glioma cells, and effectively induced cell cycle arrest at the G1 phase. Western blotting analysis indicated that silencing MPZL1 expression downregulated the expression of matrix metalloproteinase-2 (MMP-2), WNT1, caspase-3, cyclin A1, epidermal growth factor receptor (EGFR), and signal transducer and activator of transcription 3 (STAT3), and upregulated p53. The results from this study suggest that MPZL1 might be a marker for tumors and could be a potential therapeutic target for human glioma.

Synthesis of Isothiazoles and Isoselenazoles through Rhodium-Catalyzed Oxidative Annulation with Elemental Sulfur and Selenium

A rhodium-catalyzed oxidative annulation of benzimidates with elemental sulfur for the direct construction of isothiazole rings is reported. The proposed reaction mechanism involving Rh(I)/Rh(III) redox is supported by a stoichiometric reaction of metallacycle species as well as DFT calculations. This method is also applicable to selenium cyclization to produce isoselenazole derivatives. The alkoxy substituent at C3 can be used for further functionalization of the azole core.

Design, synthesis and structure-activity relationship study of novel urea compounds as FGFR1 inhibitors to treat metastatic triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive type of cancer characterized by higher metastatic and reoccurrence rates, where approximately one-third of TNBC patients suffer from the metastasis in the brain. At the same time, TNBC shows good responses to chemotherapy, a feature that fuels the search for novel compounds with therapeutic potential in this area. Recently, we have identified novel urea-based compounds with cytotoxicity against selected cell lines and with the ability to cross the blood-brain barrier in vivo. We have synthesized and analyzed a library of more than 40 compounds to elucidate the key features responsible for the observed activity. We have also identified FGFR1 as a molecular target that is affected by the presence of these compounds, confirming our data using in silico model. Overall, we envision that these compounds can be further developed for the potential treatment of metastatic breast cancer.

Synthesis and biological evaluation of a new series of 1-aryl-3-[4-(pyridin-2-ylmethoxy)phenyl]urea derivatives as new anticancer agents

The diaryl ureas are very important fragments in medicinal chemistry. By means of computer-aided design, 1-aryl-3-[4-(pyridin-2-ylmethoxy)phenyl]urea derivatives were designed and synthesized, and evaluated for their antiproliferative activity against A549, HCT-116, PC-3 cancer cell lines, and HL7702 human normal liver cell lines in vitro by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. Most of the target compounds demonstrate significant antiproliferative effects on all the selective cancer cell lines. The calculated IC₅₀ values were reported. The target compound 1-(4-chlorophenyl)-3-{4-{[3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-yl]methoxy}phenyl}urea (7u) demonstrated the most potent inhibitory activity (IC₅₀ = 2.39 ± 0.10 μM for A549 and IC₅₀ = 3.90 ± 0.33 μM for HCT-116), comparable to the positive-control sorafenib (IC₅₀ = 2.12 ± 0.18 μM for A549 and IC₅₀ = 2.25 ± 0.71 μM for HCT-116). Conclusively, 1-aryl-3-[4-(pyridin-2-ylmethoxy)phenyl]urea derivatives as the new anticancer agents were discovered, and could be used as the potential BRAF inhibitors for further research.

Synthesis and anticancer evaluation of novel 1H-benzo[d]imidazole derivatives of dehydroabietic acid as PI3Kα inhibitors

Phosphatidylinositol 3-kinase (PI3K) is one of the most attractive therapeutic targets for cancer treatment. In this study, a series of new 2-arylthio- and 2-arylamino-1H-benzo[d]imidazole derivatives of dehydroabietic acid were designed, synthesized and characterized by ¹H NMR, ¹³C NMR, IR and MS spectra analyses. In the in vitro anticancer assay, some title compounds showed significant inhibitory activities against four cancer cell lines (HCT-116, MCF-7, HeLa and HepG2). Among them, compound 9g exhibited the most potent activity with IC₅₀ values of 0.18 ± 0.03, 0.43 ± 0.05, 0.71 ± 0.08 and 0.63 ± 0.09 μM against four cancer cell lines, and considerably lower cytotoxicity to human gastric mucosal cell line Ges-1 (IC₅₀: 21.95 ± 0.73 μM). Besides, compound 9g displayed a certain selective activity to PI3Kα (IC₅₀ = 0.012 ± 0.002 μM) over PI3Kβ, γ and δ, and meanwhile, it can remarkably decrease the expression level of p-Akt (Ser473). In addition, compound 9g could increase intracellular reactive oxygen species level, decrease mitochondrial membrane potential, upregulate Bax and cleaved caspase-3/9 levels, downregulate Bcl-2 level and thus induce the apoptosis of HCT-116 cells in a dose-dependent manner. The results suggested that compound 9g could be considered as a promising PI3Kα inhibitor.

Synthesis and structure-activity relationship study of pyrrolidine-oxadiazoles as anthelmintics against Haemonchus contortus

Parasitic roundworms (nematodes) are significant pathogens of humans and animals and cause substantive socioeconomic losses due to the diseases that they cause. The control of nematodes in livestock animals relies heavily on the use of anthelmintic drugs. However, their extensive use has led to a widespread problem of drug resistance in these worms. Thus, the discovery and development of novel chemical entities for the treatment of parasitic worms of humans and animals is needed. Herein, we describe our medicinal chemistry optimization efforts of a phenotypic hit against Haemonchus contortus based on a pyrrolidine-oxadiazole scaffold. This led to the identification of compounds with potent inhibitory activities (IC₅₀ = 0.78-22.4 μM) on the motility and development of parasitic stages of H. contortus, and which were found to be highly selective in a mammalian cell counter-screen. These compounds could be used as suitable chemical tools for drug target identification or as lead compounds for further optimization.

Synthesis and biological evaluation of novel N-(piperazin-1-yl)alkyl-1H-dibenzo[a,c]carbazole derivatives of dehydroabietic acid as potential MEK inhibitors

In this paper, a series of novel 1H-dibenzo[a,c]carbazole derivatives of dehydroabietic acid bearing different N-(piperazin-1-yl)alkyl side chains were designed, synthesised and evaluated for their in vitro anticancer activities against three human hepatocarcinoma cell lines (SMMC-7721, HepG2 and Hep3B). Among them, compound 10g exhibited the most potent activity against three cancer cell lines with IC₅₀ values of 1.39 ± 0.13, 0.51 ± 0.09 and 0.73 ± 0.08 µM, respectively. In the kinase inhibition assay, compound 10g could significantly inhibit MEK1 kinase activity with IC₅₀ of 0.11 ± 0.02 µM, which was confirmed by western blot analysis and molecular docking study. In addition, compound 10g could elevate the intracellular ROS levels, decrease mitochondrial membrane potential, destroy the cell membrane integrity, and finally lead to the oncosis and apoptosis of HepG2 cells. Therefore, compound 10g could be a potent MEK inhibitor and a promising anticancer agent worthy of further investigations.

Benzisothiazolinone Derivatives as Potent Allosteric Monoacylglycerol Lipase Inhibitors That Functionally Mimic Sulfenylation of Regulatory Cysteines

We describe a set of benzisothiazolinone (BTZ) derivatives that are potent inhibitors of monoacylglycerol lipase (MGL), the primary degrading enzyme for the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). Structure-activity relationship studies evaluated various substitutions on the nitrogen atom and the benzene ring of the BTZ nucleus. Optimized derivatives with nanomolar potency allowed us to investigate the mechanism of MGL inhibition. Site-directed mutagenesis and mass spectrometry experiments showed that BTZs interact in a covalent reversible manner with regulatory cysteines, Cys201 and Cys208, causing a reversible sulfenylation known to modulate MGL activity. Metadynamics simulations revealed that BTZ adducts favor a closed conformation of MGL that occludes substrate recruitment. The BTZ derivative 13 protected neuronal cells from oxidative stimuli and increased 2-AG levels in the mouse brain. The results identify Cys201 and Cys208 as key regulators of MGL function and point to the BTZ scaffold as a useful starting point for the discovery of allosteric MGL inhibitors.

Design, synthesis, and anticancer evaluation of novel quinoline derivatives of ursolic acid with hydrazide, oxadiazole, and thiadiazole moieties as potent MEK inhibitors

In this article, a series of novel quinoline derivatives of ursolic acid (UA) bearing hydrazide, oxadiazole, or thiadiazole moieties were designed, synthesised, and screened for their in vitro antiproliferative activities against three cancer cell lines (MDA-MB-231, HeLa, and SMMC-7721). A number of compounds showed significant activity against at least one cell line. Among them, compound 4d exhibited the most potent activity against three cancer cell lines with IC50 values of 0.12 ± 0.01, 0.08 ± 0.01, and 0.34 ± 0.03 μM, respectively. In particular, compound 4d could induce the apoptosis of HeLa cells, arrest cell cycle at the G0/G1 phase, elevate intracellular reactive oxygen species level, and decrease mitochondrial membrane potential. In addition, compound 4d could significantly inhibit MEK1 kinase activity and impede Ras/Raf/MEK/ERK transduction pathway. Therefore, compound 4d may be a potential anticancer agent and a promising lead worthy of further investigation.

Colocalization Strategy Unveils an Underside Binding Site in the Transmembrane Domain of Smoothened Receptor

We unveiled an underside binding site on smoothened receptor (SMO) by a colocalization strategy using two structurally complementary photoaffinity probes derived from a known ligand Allo-1. Docking study and structural dissection identified key interactions within the site, including hydrogen bonding, π-π interactions, and hydrophobic interactions between Allo-1 and its contacting residues. Taken together, our results reveal the molecular base of Allo-1 binding and provide a basis for the design of new-generation ligands to overcome drug resistance.

An improved process for the preparation of pimavanserin tartrate

A practical synthetic route to pimavanserin tartrate, in which the target compound was obtained with 99.84% purity and in 46% total yield via a 5-step synthesis starting from 4-hydroxybenzaldehyde and (4-fluorophenyl)methanamine, is reported. The main advantages of the route include inexpensive starting materials, mild reaction conditions and an acceptable overall yield.

Design, Synthesis and Biological Evaluation of a New Series of 1-Aryl-3-{4-[(pyridin-2-ylmethyl)thio]phenyl}urea Derivatives as Antiproliferative Agents

To discover new antiproliferative agents with high efficacy and selectivity, a new series of 1-aryl-3-{4-[(pyridin-2-ylmethyl)thio]phenyl}urea derivatives (7a–7t) were designed, synthesized and evaluated for their antiproliferative activity against A549, HCT-116 and PC-3 cancer cell lines in vitro. Most of the target compounds demonstrated significant antiproliferative effects on all the selective cancer cell lines. Among them, the target compound, 1-[4-chloro-3-(trifluoromethyl)phenyl]-3-{4-{{[3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-yl]methyl}thio}phenyl}urea (7i) was identified to be the most active one against three cell lines, which was more potent than the positive control with an IC₅₀ value of 1.53 ± 0.46, 1.11 ± 0.34 and 1.98 ± 1.27 μM, respectively. Further cellular mechanism studies confirmed that compound 7i could induce the apoptosis of A549 cells in a concentration-dependent manner and elucidated compound 7i arrests cell cycle at G1 phase by flow cytometry analysis. Herein, the studies suggested that the 1-aryl-3-{4-[(pyridin-2-ylmethyl)thio]phenyl}urea skeleton might be regarded as new chemotypes for designing effective antiproliferative agents.

Multifunctional platinum(IV) complexes as immunostimulatory agents to promote cancer immunochemotherapy by inhibiting tryptophan-2,3-dioxygenase

Increasing evidences suggested that cisplatin can be involved in a tumor-specific immune response as an immunomodulator to improve antitumor immunity, but the designation and development are limited. Here, we report a series of novel Pt(IV) complexes derived from the conjugation of platinum(II) anticancer agents with an immune checkpoint TDO inhibitor. These complexes not only showed significant cytotoxic effects on the tested cancer cell lines, but also could enhance antitumor immune response. Particularly, complex T2, the mono-conjuagte of oxoplatin and (E)-4-oxo-4-(3-(2-(pyridin-3-yl)vinyl)-1H-indol-1-yl)butanoic acid, displayed 35-fold more potency than cisplatin against TDO-overexpressed HepG-2 cancer cells. Further study indicated that T2 could inhibit TDO via releasing a derivative of a TDO inhibitor and block kynurenine production, resulting in T-cell activation and proliferation in vitro. In vivo tests proved that T2 as a potent immunomodulator could highly promote the antitumor activity of cisplatin and effectively suppress the expression of TDO. This immunochemotherapeutic strategy can be promisingly applied to treat with TDO-overexpressed cancers.

Dual-targeting antitumor hybrids derived from Pt(IV) species and millepachine analogues

Many strategies have been developed to circumvent the shortcomings of Pt(II)-based chemotherapy, but the inherent problems still have not been effectively resolved. Here we report a new series of dual-targeting Pt(IV) prodrugs, conjugates of millepachine analogues with the related Pt(IV) complexes derived from cisplatin or oxaliplatin, respectively, which can inhibit tubulin polymerization and induce DNA damage. Among them, compound 19 possessed excellent antitumor activities against the tested human cancer cell lines, and arrested the cell cycle at the G2/M phases and ultimately induced cell apoptosis. Interestingly, its low cytotoxicity toward two human normal cells and sensitivity toward two cisplatin-resistant cells revealed the possibility for cancer therapy. More importantly, 19 displayed excellent antitumor efficacy in the SK-OV-3 xenograft model better than cisplatin and the corresponding millepachine analogue. Our research provided an efficient strategy for multi-targeting antitumor drug development.

Virtual Screening against Phosphoglycerate Kinase 1 in Quest of Novel Apoptosis Inhibitors

Inhibition of apoptosis is a potential therapy to treat human diseases such as neurodegenerative disorders (e.g., Parkinson’s disease), stroke, and sepsis. Due to the lack of druggable targets, it remains a major challenge to discover apoptosis inhibitors. The recent repositioning of a marketed drug (i.e., terazosin) as an anti-apoptotic agent uncovered a novel target (i.e., human phosphoglycerate kinase 1 (hPgk1)). In this study, we developed a virtual screening (VS) pipeline based on the X-ray structure of Pgk1/terazosin complex and applied it to a screening campaign for potential anti-apoptotic agents. The hierarchical filters in the pipeline (i.e., similarity search, a pharmacophore model, a shape-based model, and molecular docking) rendered 13 potential hits from Specs chemical library. By using PC12 cells (exposed to rotenone) as a cell model for bioassay, we first identified that AK-918/42829299, AN-465/41520984, and AT-051/43421517 were able to protect PC12 cells from rotenone-induced cell death. Molecular docking suggested these hit compounds were likely to bind to hPgk1 in a similar mode to terazosin. In summary, we not only present a versatile VS pipeline for potential apoptosis inhibitors discovery, but also provide three novel-scaffold hit compounds that are worthy of further development and biological study.

Antitumor lignanamides from the aerial parts of Corydalis saxicola

BACKGROUND

Cancer is one of the leading cause of unnatural death globally. There is still a great need for effective anticancer agents from plant sources. Corydalis saxicola Bunting is a medicinal plant that is traditionally used to treat various diseases in southwest China. Previous phytochemical investigations of C. saxicola have focused on isoquinoline alkaloids that have been isolated, which have activity against anti-hepatitis B virus and inhibit DNA topoisomerase I. However, the exploration of other classes of constituents and their bioactivities needs further study.

PURPOSE

The aim of this study was to investigate the antitumor activity of isolated lignanamides as well as their detailed cellular proliferation, suppression, and cytotoxic mechanisms.

METHODS

Herbs were extracted and constituents were purified by chromatographic separation, including silica gel, ODS, MCI, Sephadex LH-20 and Preparative HPLC. The compound structures were elucidated by the use of UV, IR, NMR and MS spectral data. The cytotoxicity effects of all compounds from the MGC-803, HepG2, T24, NCI-H460, Spca-2, and HL-7702 cell lines were studied by MTT assays. The induction of apoptosis by corydalisin C was investigated using acridine orange/ethidium bromide staining, Hoechst 33,258 staining, JC-1 mitochondrial membrane potential staining and flow cytometry.

RESULTS

Three new lignanamides, together with five known analogues, were isolated from the aerial parts of C. saxicola. Corydalisin C possessed the most potent inhibitory effects, with an IC₅₀ value of 8.81 ± 2.05µM against MGC-803 cells. SAR analysis showed that the sterics and chirality of lignanamides play a crucial role in pharmacologically relevant events. The antitumor activity was possibly due to the induction of cell apoptosis. Western blot experiments demonstrated that corydalisin C may induce apoptosis through both intrinsic and extrinsic apoptosis pathways, accompanied by down-regulating the expression of Bcl-2 and FasL in a time-dependent manner.

CONCLUSION

This study provides evidence that a lignanamide from the ethyl acetate extract of whole plants of C. saxicola showing potential in cancer treatment.

Molecular Mechanism of Action of Antimalarial Benzoisothiazolones: Species-Selective Inhibitors of the Plasmodium spp. MEP Pathway enzyme, IspD

The methylerythritol phosphate (MEP) pathway is an essential metabolic pathway found in malaria parasites, but absent in mammals, making it a highly attractive target for the discovery of novel and selective antimalarial therapies. Using high-throughput screening, we have identified 2-phenyl benzo[d]isothiazol-3(2H)-ones as species-selective inhibitors of Plasmodium spp. 2-C-methyl-_D-erythritol-4-phosphate cytidyltransferase (IspD), the third catalytic enzyme of the MEP pathway. 2-Phenyl benzo[d]isothiazol-3(2H)-ones display nanomolar inhibitory activity against P. falciparum and P. vivax IspD and prevent the growth of P. falciparum in culture, with EC₅₀ values below 400 nM. In silico modeling, along with enzymatic, genetic and crystallographic studies, have established a mechanism-of-action involving initial non-covalent recognition of inhibitors at the IspD binding site, followed by disulfide bond formation through attack of an active site cysteine residue on the benzo[d]isothiazol-3(2H)-one core. The species-selective inhibitory activity of these small molecules against Plasmodium spp. IspD and cultured parasites suggests they have potential as lead compounds in the pursuit of novel drugs to treat malaria.

Design, Synthesis and Structure-Activity Relationships of Novel Diaryl Urea Derivatives as Potential EGFR Inhibitors

Two novel series of diaryl urea derivatives 5a–i and 13a–l were synthesized and evaluated for their cytotoxicity against H-460, HT-29, A549, and MDA-MB-231 cancer cell lines in vitro. Therein, 4-aminoquinazolinyl-diaryl urea derivatives 5a–i demonstrated significant activity, and seven of them are more active than sorafenib, with IC₅₀ values ranging from 0.089 to 5.46 μM. Especially, compound 5a exhibited the most active potency both in cellular (IC₅₀ = 0.15, 0.089, 0.36, and 0.75 μM, respectively) and enzymatic assay (IC₅₀ = 56 nM against EGFR), representing a promising lead for further optimization.

The influence of intramolecular sulfur-lone pair interactions on small-molecule drug design and receptor binding

Sulfur-lone pair interactions are important conformational control elements in sulfur-containing heterocycles that abound in pharmaceuticals, natural products, agrochemicals, polymers and other important classes of organic molecules. Nonetheless, the role of intramolecular sulfur-lone pair interactions in the binding of small molecules to receptors is often overlooked. Here we analyze the magnitudes and origins of these interactions for a variety of biologically relevant small molecules using quantum chemical and automated docking calculations. In most cases examined in this study, the lowest energy conformation of the small molecule displays a sulfur-lone pair close contact. However, docking studies, both published and new, often predict that conformations without sulfur-lone pair contacts have the best binding affinity for their respective receptors. This is a serious problem. Since many of these predicted bound conformations are not actually energetically accessible, pursuing design (e.g., drug design) around these binding modes necessarily will lead, serendipity aside, to dead end designs. Our results constitute a caution that one best not neglect these interactions when predicting the binding affinities of potential ligands (drugs or not) for hosts (enzymes, receptors, DNA, RNA, synthetic hosts). Moreover, a better understanding and awareness of sulfur-lone pair interactions should facilitate the rational modulation of host-guest interactions involving sulfur-containing molecules.

A Scalable and Facile Process for the Preparation of N-(Pyridin-4-yl) Piperazine-1-Carboxamide Hydrochloride

A scalable and facile synthetic process for N-(pyridin-4-yl)piperazine-1-carboxamide hydrochloride, a novel Rho kinase inhibitor with an unsymmetrical urea structure currently under investigation for the treatment of central nervous system disorders, was established. After optimisation of the reaction conditions, N-(pyridin-4-yl)piperazine-1-carboxamide hydrochloride was synthesised from 4-aminopyridine and N,N′-carbonyldiimidazole through acylation, deprotection and salt formation. This new procedure affords the product in 53% overall yield with high purity and it can be easily scaled up for production.

Synthesis and pharmacological evaluation of dehydroabietic acid thiourea derivatives containing bisphosphonate moiety as an inducer of apoptosis

A series of DHAA thiourea derivatives containing bisphosphonate moiety were designed and synthesized as potent antitumor agents. Structures of target molecules were confirmed using HR-MS, (1)H NMR and (13)C NMR and they exhibited potent anti-tumor activities against the SK-OV-3, BEL-7404, A549, HCT-116 and NCI-H460 tumor cell lines in vitro. Especially, compound 6e (IC50 = 1.79 ± 0.43 μM) exhibited the best anticancer activity against SK-OV-3 cell line. Its role as an inducer of apoptosis was investigated in this cell line by Annexin-V/PI binding assay and by following its capability for ROS generation, depolarization of mitochondrial transmembrane potential, activation of caspases and expression of pro- and anti-apoptotic proteins. Elevated level of ROS generation, activation of caspase-3, caspase-8, caspase-9, and Fas, higher expression of Bax, lower expression of Bcl-2, and increased level of Bax/Bcl-2 ratio identified 6e as a promising inducer of apoptosis that follows both of the mitochondria dependent pathway and the death receptor-mediated pathway. In addition, the cell cycle analysis indicated that compound 6e caused cell cycle arrest at G1 phase, induced apoptosis and led to cell death by increasing the proportion of sub-G1 cells. Furthermore, molecular docking studies showed that 6e could bind to the ATP pocket sites.

Small Molecule Active Site Directed Tools for Studying Human Caspases

Caspases are proteases of clan CD and were described for the first time more than two decades ago. They play critical roles in the control of regulated cell death pathways including apoptosis and inflammation. Due to their involvement in the development of various diseases like cancer, neurodegenerative diseases, or autoimmune disorders, caspases have been intensively investigated as potential drug targets, both in academic and industrial laboratories. This review presents a thorough, deep, and systematic assessment of all technologies developed over the years for the investigation of caspase activity and specificity using substrates and inhibitors, as well as activity based probes, which in recent years have attracted considerable interest due to their usefulness in the investigation of biological functions of this family of enzymes.

miR-98 and its host gene Huwe1 target Caspase-3 in Silica nanoparticles-treated male germ cells

Silica nanoparticles (NP) is one of the most commonly used nanomaterials with potential health hazards. However, the effects of Silica NP on germ cells and the underlying mechanisms are still unclear. In this study, GC-2 and TM-4, which are two different types of male germ cells were exposed to Silica NP for 24h, and then general cytotoxicity and multi-parameter cytotoxicity were evaluated. Our results showed that Silica NP could induce apoptosis in GC-2 cells. Transmission electron microscopy (TEM) results showed that Silica NP was localized in the lysosomes of GC-2 cells. High content screening (HCS) showed that Silica NP exposure could increased cell permeabilization and decreased mitochondrial membrane potential in GC-2 cells. The mRNA and protein levels of apoptosis markers (Bax, Caspase-3, Caspase-9) in GC-2 cells were significantly increased, while Bcl-2 was decreased. Accordingly, the expression level of miR-98, which can regulate Caspase-3, was significantly decreased. Huwe1, the host gene of miR-98, was positively associated with miR-98 expression after Silica NP exposure. Dual luciferase reporter assay suggested that miR-98 directly targets Caspase-3. These results suggest that Silica NP induces apoptosis via loss of mitochondrial membrane potential and Caspase-3 activation, while miR-98 plays key role in modulating this effect.

Synthesis and evaluation of N-acyl-substituted 1,2-benzisothiazol-3-one derivatives as caspase-3 inhibitors

A small molecule library of N-acyl-substituted 1,2-benzisothiazol-3-one derivatives has been synthesized and evaluated as inhibitors of caspase-3 and -7, in which some of them showed nanomolar potency against caspase-3 and -7 in vitro. Meanwhile, in 10 lM concentration, both compounds 24 and 25 showed significant protection against apoptosis in camptothecin-induced Jurkat T cells system. The docking studies predicted the interactions and binding modes of the synthesized inhibitors in the caspase-3 active site.