Fragment-based drug design and drug repositioning using multiple ligand simultaneous docking (MLSD): identifying celecoxib and template compounds as novel inhibitors of signal transducer and activator of transcription 3 (STAT3)

Drug repositioning: A bibliometric analysis

Drug repurposing has become an effective approach to drug discovery, as it offers a new way to explore drugs. Based on the Science Citation Index Expanded (SCI-E) and Social Sciences Citation Index (SSCI) databases of the Web of Science core collection, this study presents a bibliometric analysis of drug repurposing publications from 2010 to 2020. Data were cleaned, mined, and visualized using Derwent Data Analyzer (DDA) software. An overview of the history and development trend of the number of publications, major journals, major countries, major institutions, author keywords, major contributors, and major research fields is provided. There were 2,978 publications included in the study. The findings show that the United States leads in this area of research, followed by China, the United Kingdom, and India. The Chinese Academy of Science published the most research studies, and NIH ranked first on the h-index. The Icahn School of Medicine at Mt Sinai leads in the average number of citations per study. Sci Rep, Drug Discov. Today, and Brief. Bioinform. are the three most productive journals evaluated from three separate perspectives, and pharmacology and pharmacy are unquestionably the most commonly used subject categories. Cheng, FX; Mucke, HAM; and Butte, AJ are the top 20 most prolific and influential authors. Keyword analysis shows that in recent years, most research has focused on drug discovery/drug development, COVID-19/SARS-CoV-2/coronavirus, molecular docking, virtual screening, cancer, and other research areas. The hotspots have changed in recent years, with COVID-19/SARS-CoV-2/coronavirus being the most popular topic for current drug repurposing research.

Emerging strategies in targeting tumor-resident myeloid cells for cancer immunotherapy

Immune checkpoint inhibitors targeting programmed cell death protein 1, programmed death-ligand 1, and cytotoxic T-lymphocyte-associated protein 4 provide deep and durable treatment responses which have revolutionized oncology. However, despite over 40% of cancer patients being eligible to receive immunotherapy, only 12% of patients gain benefit. A key to understanding what differentiates treatment response from non-response is better defining the role of the innate immune system in anti-tumor immunity and immune tolerance. Teleologically, myeloid cells, including macrophages, dendritic cells, monocytes, and neutrophils, initiate a response to invading pathogens and tissue repair after pathogen clearance is successfully accomplished. However, in the tumor microenvironment (TME), these innate cells are hijacked by the tumor cells and are imprinted to furthering tumor propagation and dissemination. Major advancements have been made in the field, especially related to the heterogeneity of myeloid cells and their function in the TME at the single cell level, a topic that has been highlighted by several recent international meetings including the 2021 China Cancer Immunotherapy workshop in Beijing. Here, we provide an up-to-date summary of the mechanisms by which major myeloid cells in the TME facilitate immunosuppression, enable tumor growth, foster tumor plasticity, and confer therapeutic resistance. We discuss ongoing strategies targeting the myeloid compartment in the preclinical and clinical settings which include: (1) altering myeloid cell composition within the TME; (2) functional blockade of immune-suppressive myeloid cells; (3) reprogramming myeloid cells to acquire pro-inflammatory properties; (4) modulating myeloid cells via cytokines; (5) myeloid cell therapies; and (6) emerging targets such as Siglec-15, TREM2, MARCO, LILRB2, and CLEVER-1. There is a significant promise that myeloid cell-based immunotherapy will help advance immuno-oncology in years to come.

Contemporary medicinal chemistry strategies for the discovery and optimization of influenza inhibitors targeting vRNP constituent proteins

Influenza is an acute respiratory infectious disease caused by the influenza virus, affecting people globally and causing significant social and economic losses. Due to the inevitable limitations of vaccines and approved drugs, there is an urgent need to discover new anti-influenza drugs with different mechanisms. The viral ribonucleoprotein complex (vRNP) plays an essential role in the life cycle of influenza viruses, representing an attractive target for drug design. In recent years, the functional area of constituent proteins in vRNP are widely used as targets for drug discovery, especially the PA endonuclease active site, the RNA-binding site of PB1, the cap-binding site of PB2 and the nuclear export signal of NP protein. Encouragingly, the PA inhibitor baloxavir has been marketed in Japan and the United States, and several drug candidates have also entered clinical trials, such as favipiravir. This article reviews the compositions and functions of the influenza virus vRNP and the research progress on vRNP inhibitors, and discusses the representative drug discovery and optimization strategies pursued.

Nifuroxazide Mitigates Angiogenesis in Ehlrich's Solid Carcinoma: Molecular Docking, Bioinformatic and Experimental Studies on Inhibition of Il-6/Jak2/Stat3 Signaling

Nifuroxazide is an antidiarrheal medication that has promising anticancer activity against diverse types of tumors. The present study tested the anticancer activity of nifuroxazide against Ehrlich’s mammary carcinoma grown in vivo. Furthermore, we investigated the effect of nifuroxazide on IL-6/jak2/STAT3 signaling and the possible impact on tumor angiogenesis. The biological study was supported by molecular docking and bioinformatic predictions for the possible effect of nifuroxazide on this signaling pathway. Female albino mice were injected with Ehrlich carcinoma cells to produce Ehrlich’s solid tumors (ESTs). The experimental groups were as follows: EST control, EST + nifuroxazide (5 mg/kg), and EST + nifuroxazide (10 mg/kg). Nifuroxazide was found to reduce tumor masses (730.83 ± 73.19 and 381.42 ± 109.69 mg vs. 1099.5 ± 310.83) and lessen tumor pathologies. Furthermore, nifuroxazide downregulated IL-6, TNF-α, NFk-β, angiostatin, and Jak2 proteins, and it also reduced tumoral VEGF, as indicated by ELISA and immunohistochemical analysis. Furthermore, nifuroxazide dose-dependently downregulated STAT3 phosphorylation (60% and 30% reductions, respectively). Collectively, the current experiment shed light on the antitumor activity of nifuroxazide against mammary solid carcinoma grown in vivo. The antitumor activity was at least partly mediated by inhibition of IL-6/Jak2/STAT3 signaling that affected angiogenesis (low VEGF and high angiostatin) in the EST. Therefore, nifuroxazide might be a promising antitumor medication if appropriate human studies will be conducted.

A Complex Metabolic Network Confers Immunosuppressive Functions to Myeloid-Derived Suppressor Cells (MDSCs) within the Tumour Microenvironment

Myeloid-derived suppressor cells (MDSCs) constitute a plastic and heterogeneous cell population among immune cells within the tumour microenvironment (TME) that support cancer progression and resistance to therapy. During tumour progression, cancer cells modify their metabolism to sustain an increased energy demand to cope with uncontrolled cell proliferation and differentiation. This metabolic reprogramming of cancer establishes competition for nutrients between tumour cells and leukocytes and most importantly, among tumour-infiltrating immune cells. Thus, MDSCs that have emerged as one of the most decisive immune regulators of TME exhibit an increase in glycolysis and fatty acid metabolism and also an upregulation of enzymes that catabolise essential metabolites. This complex metabolic network is not only crucial for MDSC survival and accumulation in the TME but also for enhancing immunosuppressive functions toward immune effectors. In this review, we discuss recent progress in the field of MDSC-associated metabolic pathways that could facilitate therapeutic targeting of these cells during cancer progression.

Repositioning Azelnidipine as a Dual Inhibitor Targeting CD47/SIRPα and TIGIT/PVR Pathways for Cancer Immuno-Therapy

Strategies boosting both innate and adaptive immunity have great application prospects in cancer immunotherapy. Antibodies dual blocking the innate checkpoint CD47 and adaptive checkpoint PD-L1 or TIGIT could achieve durable anti-tumor effects. However, a small molecule dual blockade of CD47/SIRPα and TIGIT/PVR pathways has not been investigated. Here, an elevated expression of CD47 and PVR was observed in tumor tissues and cell lines analyzed with the GEO datasets and by flow cytometry, respectively. Compounds approved by the FDA were screened with the software MOE by docking to the potential binding pockets of SIRPα and PVR identified with the corresponding structural analysis. The candidate compounds were screened by blocking and MST binding assays. Azelnidipine was found to dual block CD47/SIRPα and TIGIT/PVR pathways by co-targeting SIRPα and PVR. In vitro, azelnidipine could enhance the macrophage phagocytosis when co-cultured with tumor cells. In vivo, azelnidipine alone or combined with irradiation could significantly inhibit the growth of MC38 tumors. Azelnidipine also significantly inhibits the growth of CT26 tumors, by enhancing the infiltration and function of CD8⁺ T cell in tumor and systematic immune response in the tumor-draining lymph node and spleen in a CD8⁺ T cell dependent manner. Our research suggests that the anti-hypertensive drug azelnidipine could be repositioned for cancer immunotherapy.

STAT3 and p53: Dual Target for Cancer Therapy

The tumor suppressor p53 is considered the "guardian of the genome" that can protect cells against cancer by inducing cell cycle arrest followed by cell death. However, STAT3 is constitutively activated in several human cancers and plays crucial roles in promoting cancer cell proliferation and survival. Hence, STAT3 and p53 have opposing roles in cellular pathway regulation, as activation of STAT3 upregulates the survival pathway, whereas p53 triggers the apoptotic pathway. Constitutive activation of STAT3 and gain or loss of p53 function due to mutations are the most frequent events in numerous cancer types. Several studies have reported the association of STAT3 and/or p53 mutations with drug resistance in cancer treatment. This review discusses the relationship between STAT3 and p53 status in cancer, the molecular mechanism underlying the negative regulation of p53 by STAT3, and vice versa. Moreover, it underlines prospective therapies targeting both STAT3 and p53 to enhance chemotherapeutic outcomes.

Isoliquiritigenin prevents hyperglycemia-induced renal injuries by inhibiting inflammation and oxidative stress via SIRT1-dependent mechanism

Diabetic nephropathy (DN) as a global health concern is closely related to inflammation and oxidation. Isoliquiritigenin (ISL), a natural flavonoid compound, has been demonstrated to inhibit inflammation in macrophages. Herein, we investigated the effect of ISL in protecting against the injury in STZ-induced type 1 DN and in high glucose-induced NRK-52E cells. In this study, it was revealed that the administration of ISL not only ameliorated renal fibrosis and apoptosis, but also induced the deterioration of renal function in diabetic mice. Mediated by MAPKs and Nrf-2 signaling pathways, respectively, upstream inflammatory response and oxidative stress were neutralized by ISL in vitro and in vivo. Moreover, as further revealed by the results of molecular docking, sirtuin 1 (SIRT1) binds to ISL directly, and the involvement of SIRT1 in ISL-mediated renoprotective effects was confirmed by studies using in vitro models of SIRT1 overexpression and knockdown. In summary, by reducing inflammation and oxidative stress, ISL has a significant pharmacological effect on the deterioration of DN. The benefits of ISL are associated with the direct binding to SIRT1, the inhibition of MAPK activation, and the induction of Nrf-2 signaling, suggesting the potential of ISL for DN treatment.

Targeting STAT3 in Cancer Immunotherapy

As a point of convergence for numerous oncogenic signaling pathways, signal transducer and activator of transcription 3 (STAT3) is central in regulating the anti-tumor immune response. STAT3 is broadly hyperactivated both in cancer and non-cancerous cells within the tumor ecosystem and plays important roles in inhibiting the expression of crucial immune activation regulators and promoting the production of immunosuppressive factors. Therefore, targeting the STAT3 signaling pathway has emerged as a promising therapeutic strategy for numerous cancers. In this review, we outline the importance of STAT3 signaling pathway in tumorigenesis and its immune regulation, and highlight the current status for the development of STAT3-targeting therapeutic approaches. We also summarize and discuss recent advances in STAT3-based combination immunotherapy in detail. These endeavors provide new insights into the translational application of STAT3 in cancer and may contribute to the promotion of more effective treatments toward malignancies.

To inhibit TrxR1 is to inactivate STAT3-Inhibition of TrxR1 enzymatic function by STAT3 small molecule inhibitors

The transcription factor STAT3 plays a key role in cancer and immunity, being widely explored as a potential drug target for the development of novel immunomodulatory or anticancer therapeutics. The mechanisms of small molecule-derived inhibition of STAT3 appear, however, to be more complex than initially perceived. Our recent discovery, that some novel STAT3 inhibitors were bona fide inhibitors of the cytosolic selenoprotein oxidoreductase TrxR1 (TXNRD1), led us to explore the effects of a wide array of previously described STAT3 inhibitors on TrxR1 function. We found that 17 out of 23 tested STAT3 small molecule inhibitors indeed inhibited purified TrxR1 at the reported concentrations yielding STAT3 inhibition. All tested compounds were electrophilic as shown by direct reactivities with GSH, and several were found to also be redox cycling substrates of TrxR1. Ten compounds previously shown to inhibit STAT3 were here found to irreversibly inhibit cellular TrxR1 activity (Auranofin, Stattic, 5,15-DPP, Galiellalactone, LLL12, Napabucasin, BP1-102, STA-21, S3I-201 and Degrasyn (WP1130)). Our findings suggest that targeting of TrxR1 may be a common feature for many small molecules that inhibit cellular STAT3 function. It is possible that prevention of STAT3 activation in cells by several small molecules classified as STAT3 inhibitors can be a downstream event following TrxR1 inhibition. Therefore, the relationship between TrxR1 and STAT3 should be considered when studying inhibition of either of these promising drug targets.

Berbamine Enhances the Efficacy of Gefitinib by Suppressing STAT3 Signaling in Pancreatic Cancer Cells

Background

Small molecular inhibitors such as gefitinib (Gefi), which target EGF receptor (EGFR), are considered to be a viable pathway for the selective inhibition of pancreatic cancer (PC) development. However, the large difference in Gefi response between PC patient individuals and PC cell lines severely limits the clinical efficacy of Gefi. Berbamine (BBM) is a well-known natural-derived antitumor agent. However, no study yet exists on whether BBM can enhance the sensitivity of PC cells to Gefi or its underlying mechanisms.

Methods

MTS assay and clonogenic assay were used to determine whether BBM could enhance the anti-PC activity of Gefi by. Flow cytometric analysis was performed to study the cell cycle progression and rate of apoptosis after combined treatment with BBM and Gefi. Surface plasmon resonance (SPR) and Western blot experiments were carried out to detect the STAT3 binding affinity and the STAT3 inhibitory effect of BBM. Molecular docking and Molecular dynamic simulation were used to predicting the dominant interaction between BBM and STAT3.

Results

This study found that BBM synergizes with Gefi to inhibit cell growth and induce cell cycle arrest and PC cell apoptosis. Mechanistically, our results showed that BBM and Gefi have synergistic inhibitory effects on STAT3 phosphorylation, but have little effect on other EGFR downstream pathways, suggesting that BBM may exert sensitization through the inhibition of STAT3. Besides, BBM has a high affinity for STAT3 and a good inhibitory effect on STAT3 activation, further indicating that BBM was a potent direct STAT3 inhibitor. Molecular modeling between STAT3 and BBM suggested that BBM formed several key hydrophilic interactions with STAT3.

Conclusion

Our findings suggest that the combination of BBM and Gefi could be further developed as a potential PC therapy.

Fraxetin Suppresses Proliferation of Non-Small-Cell Lung Cancer Cells via Preventing Activation of Signal Transducer and Activator of Transcription 3

Lung cancer represents the leading cause of cancer-associated mortality, and non-small-cell lung cancer (NSCLC) is the most frequent histologic sub-type. It is therefore urgent to develop novel agents for the treatment of NSCLC. Fraxetin (FXT) is a potent plant-derived product and has been recognized as a promising anticancer agent for breast cancer and osteosarcoma. However, the anti-cancer potential of FXT for NSCLC remains to be elucidated. Accordingly, in the present study, we evaluated the inhibitory effect of FXT on the proliferation and growth of NSCLC cells using six human NSCLC cell lines: A549, H460, HCC827, H1650, PC-9 and H1975. FXT exhibited significant inhibitory effects on the proliferation of these cancer cell lines. By contrast, no inhibitory effect was observed on the viability of non-cancer lung cell lines even at the highest concentration of FXT (100 μM). Among the NSCLC cell lines, HCC827 and H1650 cells showed the most sensitive to FXT. Accordingly, HCC827 and H1650 cells were used for the subsequent experiments. Flow cytometric analysis revealed that FXT caused a significant cell cycle arrest and pro-apoptotic effects. Mechanistically, FXT suppressed the IL-6-induced phosphorylation of tyrosine residue (Tyr705) of signal transducer and activator of transcription 3 (STAT3) probably by binding to STAT3. Molecular docking and molecular dynamic simulations studies indicated that FXT interacts with STAT3 through hydrogen bond and hydrophobic interaction. In conclusion, these findings suggest that FXT could be a promising lead compound to be used as a novel STAT3 inhibitor and potential antitumor agent for the treatment of NSCLC.

Revisiting signal transducer and activator of transcription 3 (STAT3) as an anticancer target and its inhibitor discovery: Where are we and where should we go?

As a transcription factor, STAT3 protein transduces extracellular signals to the nucleus and then activates transcription of target genes. STAT3 has been well validated as an attractive anticancer target due to its important roles in cancer initiation and progression. Identification of specific and potent STAT3 inhibitors has attracted much attention, while there has been no STAT3 targeted drug approved for clinical application. In this review, we will briefly introduce STAT3 protein and review its role in multiple aspects of cancer, and systematically summarize the recent advances in discovery of STAT3 inhibitors, especially the ones discovered in the past five years. In the last part of the review, we will discuss the possible new strategies to overcome the difficulties of developing potent and specific STAT3 inhibitors and hope to shed light on future drug design and inhibitor optimization.

Luteolin Attenuates Atherosclerosis Via Modulating Signal Transducer And Activator Of Transcription 3-Mediated Inflammatory Response

Background

Inflammatory factors play a crucial role throughout the development and progression of atherosclerosis, which has been considered as a chronic vascular inflammatory disease. Luteolin, a natural flavonoid which exists in many natural medicinal materials, has anti-inflammatory, anti-fibrotic and other pharmacological effects. Recently, the protective effects of luteolin on the cardiovascular disease have been reported. However, there is a paucity of studies on anti-atherosclerosis. Therefore, the anti-atherosclerosis potential of luteolin remains to be elucidated.

Method

ApoE^-/- mice were fed with a high-fat diet to induce atherosclerosis in an animal model, where they were treated with oral administration of luteolin for 12 weeks. Primary mouse peritoneal macrophages challenged with oxidized low-density lipoprotein (oxLDL) were used for in vitro mechanistic study. The effectiveness of luteolin in the ApoE^-/- mouse model of atherosclerosis was estimated in the aortic sinus and enface, and the underlying mechanisms were explored by molecular modeling study and siRNA-induced gene silencing.

Results

Our results showed that luteolin remarkably attenuated atherosclerosis in high-fat diet-induced ApoE^-/- mouse via alleviating inflammation. We further found that luteolin decreased oxLDL-induced inflammation by inhibiting signal transducer and activator of transcription 3 (STAT3) in vitro, respectively. Further molecular modeling analysis indicated that luteolin interacted with STAT3 primarily through hydrogen bond interaction.

Conclusion

Luteolin could be a promising candidate molecule for atherosclerosis, and STAT3 may be a potential therapeutic target that could prevent the development of atherosclerosis.

STAT3: A Potential Drug Target for Tumor and Inflammation

STAT (Signal Transducers and Activators of Transcription) is a cellular signal transcription factor involved in the regulation of many cellular activities, such as cell differentiation, proliferation, angiogenesis in normal cells. During the study of the STAT family, STAT3 was found to be involved in many diseases, such as high expression and sustained activation of STAT3 in tumor cells, promoting tumor growth and proliferation. In the study of inflammation, it was found that it plays an important role in the anti-inflammatory and repairing of damage tissues. Because of the important role of STAT3, a large number of studies have been obtained. At the same time, after more than 20 years of development, STAT3 has also been used as a target for drug therapy. And the discovery of small molecule inhibitors also promoted the study of STAT3. Since STAT3 has been extensively studied in inflammation and tumor regulation, this review presents the current state of research on STAT3.

Design, synthesis and activity of novel 2,6-disubstituted purine derivatives, potential small molecule inhibitors of signal transducer and activator of transcription 3

Sustained activation of STAT3 is closely related to the cancer development, but the inhibitors for STAT3 overexpression are still in the clinical research stage. In this study, a series of 2,6-disubstituted purine derivatives were designed and synthesized, and their biological activities, as small molecule inhibitors of STAT3, were assessed. Compound PD26-TL07 exhibited remarkable antiproliferative activity against three cancer cell lines (IC₅₀ values for HCT-116, SW480 and MDA-MB-231 were 1.77 ± 0.35, 1.51 ± 0.19, and 1.25 ± 0.38 μM, respectively). Moreover, detailed biological assays revealed that PD26-TL07 could effectively inhibited STAT3 phosphorylation, and had little inhibition to others'. The newly discovered PD26-TL07 displayed an expecting anticancer effect both in vitro and in vivo. The molecular docking models revealed that PD26-TL07 could bind to the SH2 domain of STAT3. Three additional compounds (PD26-BZ01, PD26-TL03 and PD26-AS06) were also able to inhibit this phosphorylation. This study described novel 2,6-disubstituted purine derivatives as potent anticancer agents targeting STAT3.

Overview of Recent Strategic Advances in Medicinal Chemistry

Introducing novel strategies, concepts, and technologies that speed up drug discovery and the drug development cycle is of great importance both in the highly competitive pharmaceutical industry as well as in academia. This Perspective aims to present a "big-picture" overview of recent strategic innovations in medicinal chemistry and drug discovery.

Transition-metal-free regioselective construction of 1,5-diaryl-1,2,3-triazoles through dehydrative cycloaddition of alcohols with aryl azides mediated by SO2F2

A novel, simple and practical method for mild, efficient, cost-effective and regioselective synthesis of highly valuable 1,5-diaryl-1,2,3-triazoles was achieved through dehydrative annulation of readily available alcohols with aryl azides. The reaction proceeded at room temperature, without any metal catalysts, exhibiting excellent compatibility to a large variety of functional groups (>50 examples), resulting in up to quantitative yields.

Re-positioning of known drugs for Pim-1 kinase target using molecular docking analysis

The Concept of reusing existing drugs for new targets is gaining momentum in recent years because of cost-effectiveness as safety and toxicology data are already available. Therefore, it is of interest to re-profile known drugs against the Pim-1 kinase target using molecular docking analysis. Results show that known drugs such as nilotinib, vemurafenib, Idelalisib, and other small kinases inhibitors have high binding ability with Pim-1 kinase for consideration as potential inhibitors.

Novel small molecule IL-6 inhibitor suppresses autoreactive Th17 development and promotes Treg development

Multiple sclerosis (MS) is the leading cause of non-traumatic neurological disability in the United States in young adults, but current treatments are only partially effective, making it necessary to develop new, innovative therapeutic strategies. Myelin-specific interleukin (IL)-17-producing T helper type 17 (Th17) cells are a major subset of CD4 T effector cells (T_eff ) that play a critical role in mediating the development and progression of MS and its mouse model, experimental autoimmune encephalomyelitis (EAE), while regulatory T cells (T_reg ) CD4 T cells are beneficial for suppressing disease. The IL-6/signal transducer and activator of transcription 3 (STAT-3) signaling pathway is a key regulator of Th17 and T_reg cells by promoting Th17 development and suppressing T_reg development. Here we show that three novel small molecule IL-6 inhibitors, madindoline-5 (MDL-5), MDL-16 and MDL-101, significantly suppress IL-17 production in myelin-specific CD4 T cells in a dose-dependent manner in vitro. MDL-101 showed superior potency in suppressing IL-17 production compared to MDL-5 and MDL-16. Treatment of myelin-specific CD4 T cells with MDL-101 in vitro reduced their encephalitogenic potential following their subsequent adoptive transfer. Furthermore, MDL-101 significantly suppressed proliferation and IL-17 production of anti-CD3-activated effector/memory CD45RO⁺ CD4⁺ human CD4 T cells and promoted human T_reg development. Together, these data demonstrate that these novel small molecule IL-6 inhibitors have the potential to shift the T_eff  : T_reg balance, which may provide a novel therapeutic strategy for ameliorating disease progression in MS.

Medicinal chemistry of vicinal diaryl scaffold: A mini review

The privileged structures have been widely used as a valuable template in new drug discovery. 1,2-Diaryl or vicinal diaryl is a simple scaffold found in many drugs and naturally occurring compounds. From synthetic point of view, the vicinal diaryl derivatives are easily accessible due to their facile and expedient syntheses. These scaffolds have shown numerous interesting pharmacological activities against various diseases with lot of clinical potentials. This review aims to highlight the evidence of vicinal diaryl motif as a privileged scaffold in COX-2 inhibitors and CA-4 analogs.

A new synthetic derivative of cryptotanshinone KYZ3 as STAT3 inhibitor for triple-negative breast cancer therapy

Silencing STAT3 is confirmed as a promising therapeutic strategy for triple-negative breast cancer (TNBC) therapy to address the issue of its poor prognosis. In this study, the natural product cryptotanshinone was firstly remodeled and modified as a more effective STAT3 inhibitor by structure-based strategy. The synthetic derivative KYZ3 had 22-24-fold increase in antitumor activity than cryptotanshinone on two TNBC cell lines but had little effect on normal breast epithelial MCF-10A cells. Further investigation showed that KYZ3 inhibited persistent STAT3 phosphorylation. It also prevented the STAT3 protein nuclear translocation to regulate the expressions of the target oncogenes including Bax and Bcl-2. Furthermore, KYZ3 inhibited TNBC cell metastasis by decreasing the levels of MMP-9 which were directly regulated by activated STAT3. A STAT3 plasmid transfecting assay suggested that KYZ3 induced tumor cell apoptosis mainly by targeting STAT3. Finally, KYZ3 suppressed the growth of tumors resulting from subcutaneous implantation of MDA-MB-231 cells in vivo. Taken together, KYZ3 may be a promising cancer therapeutic agent for TNBC.

Rational application of drug promiscuity in medicinal chemistry

‘Drug promiscuity’ refers to a drug that can act on multiple molecular targets, exhibiting similar or different pharmacological effects. Drugs may interact with unwanted targets, leading to off-target effects (one of the main reasons for side effects). Thus, intervention to prevent off-target effects in the early stages of drug discovery could reduce the risk of failure. The conversion between target and off-target effects is important for drug repurposing. Drug repurposing strategies could reduce research and development costs. This review details the research progress in the rational application of drug promiscuity for the discovery of multi-target drugs, drug repurposing and improving druggability in medicinal chemistry over the last 5 years.

L61H46 shows potent efficacy against human pancreatic cancer through inhibiting STAT3 pathway

Background

Pancreatic cancer is the fourth leading cause of cancer-related death worldwide. The poor prognosis of this disease highlights the urgent need to develop more effective therapies. Activation of the STAT3 represents a potential drug target for pancreatic cancer therapy. Currently, clinically available small-molecule inhibitors targeting STAT3 are lacking.

Methods

Through bioassay screening and molecular docking, we identified a small molecule L61H46 that can potently target constitutive STAT3 signaling and kill human pancreatic cancer cells in vitro and in vivo.

Results

L61H46 effectively reduced colony formation and the viability of pancreatic cancer cells in a dose-dependent manner with half-maximal inhibitory concentration (IC₅₀) values in the range between 0.86 and 2.83 µM. L61H46 significantly inhibited STAT3 phosphorylation (Tyr705) and the subsequent nucleus translocation but did not downregulate STAT1 phosphorylation. Moreover, L61H46 demonstrated a potent activity in suppressing pancreatic tumor growth in BXPC-3 xenograft model in vivo. Furthermore, L61H46 showed no signs of adverse effects on liver, heart, and kidney cells in vivo.

Conclusion

Collectively, our results suggest that L61H46 could be further optimized into a highly potent STAT3 inhibitor for the treatment of pancreatic cancer.

Hot-spot analysis for drug discovery targeting protein-protein interactions

INTRODUCTION

Protein-protein interactions are important for biological processes and pathological situations, and are attractive targets for drug discovery. However, rational drug design targeting protein-protein interactions is still highly challenging. Hot-spot residues are seen as the best option to target such interactions, but their identification requires detailed structural and energetic characterization, which is only available for a tiny fraction of protein interactions. Areas covered: In this review, the authors cover a variety of computational methods that have been reported for the energetic analysis of protein-protein interfaces in search of hot-spots, and the structural modeling of protein-protein complexes by docking. This can help to rationalize the discovery of small-molecule inhibitors of protein-protein interfaces of therapeutic interest. Computational analysis and docking can help to locate the interface, molecular dynamics can be used to find suitable cavities, and hot-spot predictions can focus the search for inhibitors of protein-protein interactions. Expert opinion: A major difficulty for applying rational drug design methods to protein-protein interactions is that in the majority of cases the complex structure is not available. Fortunately, computational docking can complement experimental data. An interesting aspect to explore in the future is the integration of these strategies for targeting PPIs with large-scale mutational analysis.

Copper-catalyzed decarboxylative regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles

A copper-catalyzed decarboxylative regioselective protocol for the synthesis of 1,5-disubstituted 1,2,3-triazoles via direct annulation of cinnamic acids with aryl azides has been developed. This is the first example of 1,5-disubstituted 1,2,3-triazoles using Cu(ii) as the catalyst, which were generally synthesized using a ruthenium(ii) catalyst.

Identification of New Shikonin Derivatives as Antitumor Agents Targeting STAT3 SH2 Domain

Signal transducer and activator of transcription 3 (STAT3) is hyper-activated in diversiform human tumors and has been validated as an attractive therapeutic target. Current research showed that a natural product, shikonin, along with its synthetic analogues, is able to inhibit the activity of STAT3 potently. The potential space of shikonin in developing novel anti-cancer agents encouraged us to carry out the investigation of the probable binding mode with STAT3. From this foundation, we have designed new types of STAT3 SH2 inhibitors. Combined simulations were performed to filter for the lead compound, which was then substituted, synthesized and evaluated by a variety of bioassays. Among the entities, PMM-172 exhibited the best anti-proliferative activity against MDA-MB-231 cells with IC₅₀ value 1.98 ± 0.49 μM. Besides, it was identified to decrease luciferase activity, induce cell apoptosis and reduce mitochondrial transmembrane potential in MDA-MB-231 cells. Also, PMM-172 inhibited constitutive/inducible STAT3 activation without affecting STAT1 and STAT5 in MDA-MB-231 cells, and had no effect in non-tumorigenic MCF-10A cells. Moreover, PMM-172 suppressed STAT3 nuclear localization and STAT3 downstream target genes expression. Overall, these results indicate that the antitumor activity of PMM-172 is at least partially due to inhibition of STAT3 in breast cancer cells.

Functional characterization of TRPM7 in nasopharyngeal carcinoma and its knockdown effects on tumorigenesis

The aim of this study was to evaluate the association of functional expression of TRPM7 with nasopharyngeal carcinoma (NPC) growth. We examined the correlation of TRPM7 expression with cell growth and proliferation, cell cycle, and apoptosis in vitro in NPC cell lines and NPC tumorigenesis in mice by conducting experiments in mice and by further analyzing the tumor volume and growth. We further explored to see whether there is any positive correlation with the TRPM7 knockdown in NPC cells with their sensitivity to radiation. We found that the functional expression of TRPM7 in nasopharyngeal carcinoma is a critical requirement for physiological processes such as cell cycle, resistance to apoptosis, and cell proliferation. TRPM7 knockdown also enhanced sensitivity to radiotherapy of nasopharyngeal carcinoma. Moreover, we identified TRPM7 as a novel potential regulator of cell proliferation in NPC, through signal transducer and activator of transcription 3 (STAT3)-mediated signaling pathway and other anti-apoptotic factors. TRPM7 and STAT3 activation might be critical for the growth of NPC cells and could be an effective target for treatment of nasopharyngeal carcinoma.

Feedback Activation of STAT3 as a Cancer Drug-Resistance Mechanism

Signal transducer and activator of transcription 3 (STAT3) plays crucial roles in several cellular processes such as cell proliferation and survival, and has been found to be aberrantly activated in many cancers. Much research has explored the leading mechanisms for regulating the STAT3 pathway and its role in promoting tumorigenesis. We focus here on recent evidence suggesting that feedback activation of STAT3 plays a prominent role in mediating drug resistance to a broad spectrum of targeted cancer therapies and chemotherapies. We highlight the potential of co-targeting STAT3 and its primary target to overcome drug resistance, and provide perspective on repurposing clinically approved drugs as STAT3 pathway inhibitors, in combination with the FDA-approved receptor tyrosine kinase (RTK) inhibitors, to improve clinical outcome of cancer treatment.

The dual epigenetic role of PRMT5 in acute myeloid leukemia: gene activation and repression via histone arginine methylation

Changes in the enzymatic activity of protein arginine methyltransferase (PRMT) 5 have been associated with cancer; however, the protein's role in acute myeloid leukemia (AML) has not been fully evaluated. Here, we show that increased PRMT5 activity enhanced AML growth in vitro and in vivo while PRMT5 downregulation reduced it. In AML cells, PRMT5 interacted with Sp1 in a transcription repressor complex and silenced miR-29b preferentially via dimethylation of histone 4 arginine residue H4R3. As Sp1 is also a bona fide target of miR-29b, the miR silencing resulted in increased Sp1. This event in turn led to transcription activation of FLT3, a gene that encodes a receptor tyrosine kinase. Inhibition of PRMT5 via sh/siRNA or a first-in-class small-molecule inhibitor (HLCL-61) resulted in significantly increased expression of miR-29b and consequent suppression of Sp1 and FLT3 in AML cells. As a result, significant antileukemic activity was achieved. Collectively, our data support a novel leukemogenic mechanism in AML where PRMT5 mediates both silencing and transcription of genes that participate in a 'yin-yang' functional network supporting leukemia growth. As FLT3 is often mutated in AML and pharmacologic inhibition of PRMT5 appears feasible, the PRMT5-miR-29b-FLT3 network should be further explored as a novel therapeutic target for AML.

Novel 2-Carbonylbenzo[b]thiophene 1,1-Dioxide Derivatives as Potent Inhibitors of STAT3 Signaling Pathway

Signal transducer and activator of transcription 3 (STAT3) is considered to be an attractive therapeutic target for cancer therapy. In this study, a series of 2-carbonylbenzo[b]thiophene 1,1-dioxide derivatives (CBT) were designed to inhibit the STAT3 SH2 domain phosphorylation site Try 705. We demonstrated that incorporation of basic flexible groups through amide bond linkage to benzo[b]thiophene 1,1-dioxide (BTP) achieved compounds with higher antiproliferative potency than BTP itself. The most potent compound 6o, as indicated from luciferase reporter gene assay, inhibited the STAT3 pathway by decreasing the phosphorylation level of STAT3 Tyr705, while the phosphorylation level of other upstream tyrosine kinases in this pathway was not significantly inhibited. Compound 6o was also shown to trigger ROS generation and accumulation, thus consequently attributed partially to the observed cell apoptosis. This study provided important structural information for the development of inhibitors targeting the STAT3 pathway.

Novel aminotetrazole derivatives as selective STAT3 non-peptide inhibitors

The development of inhibitors blocking STAT3 transcriptional activity is a promising therapeutic approach against cancer and inflammatory diseases. In this context, the selectivity of inhibitors against the STAT1 transcription factor is crucial as STAT3 and STAT1 play opposite roles in the apoptosis of tumor cells and polarization of the immune response. A structure-based virtual screening followed by a luciferase-containing promoter assay on STAT3 and STAT1 signaling were used to identify a selective STAT3 inhibitor. An important role of the aminotetrazole group in modulating STAT3 and STAT1 inhibitory activities has been established. Optimization of the hit compound leads to 23. This compound inhibits growth and survival of cells with STAT3 signaling pathway while displaying a minimal effect on STAT1 signaling. Moreover, it prevents lymphocyte T polarization into Th17 and Treg without affecting their differentiation into Th1 lymphocyte.

Considerations of Protein Subpockets in Fragment-Based Drug Design

While the fragment-based drug design approach continues to gain importance, gaps in the tools and methods available in the identification and accurate utilization of protein subpockets have limited the scope. The importance of these features of small molecule-protein recognition is highlighted with several examples. A generalized solution for the identification of subpockets and corresponding chemical fragments remains elusive, but there are numerous advancements in methods that can be used in combination to address subpockets. Finally, additional examples of approaches that consider the relative importance of small-molecule co-dependence of protein conformations are highlighted to emphasize an increased significance of subpockets, especially at protein interfaces.

Drug repositioning and repurposing: terminology and definitions in literature

Drug repositioning and similar terms have been a trending topic in literature and represent novel drug development strategies. We analysed in a quantitative and qualitative manner how these terms were used and defined in the literature. In total, 217 articles referred to 'drug repositioning', 'drug repurposing', 'drug reprofiling', 'drug redirecting' and/or 'drug rediscovery'. Only 67 included a definition ranging from brief and general to extensive and specific. No common definition was identified. Nevertheless, four common features were found: concept, action, use and product. The different wording used for these features often leads to essential differences in meaning between definitions. In case a clear definition is needed, for example from a legal or regulatory perspective, the features can provide further guidance.

Early repositioning through compound set enrichment analysis: a knowledge-recycling strategy

Despite famous serendipitous drug repositioning success stories, systematic projects have not yet delivered the expected results. However, repositioning technologies are gaining ground in different phases of routine drug development, together with new adaptive strategies. We demonstrate the power of the compound information pool, the ever-growing heterogeneous information repertoire of approved drugs and candidates as an invaluable catalyzer in this transition. Systematic, computational utilization of this information pool for candidates in early phases is an open research problem; we propose a novel application of the enrichment analysis statistical framework for fusion of this information pool, specifically for the prediction of indications. Pharmaceutical consequences are formulated for a systematic and continuous knowledge recycling strategy, utilizing this information pool throughout the drug-discovery pipeline.

Antagonizing STAT3 dimerization with a rhodium(III) complex

Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity.

WITHDRAWN: Intrinsic molecular characteristics of inhibiting STAT3 activation and dimerization through targeting the phosphotyrosine binding site within the SH2 domain-A molecular dynamics study

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Identification and characterization of small molecule inhibitors of signal transducer and activator of transcription 3 (STAT3) signaling pathway by virtual screening

Inhibition of the signal transducer and activator of transcription 3 (STAT3) signaling pathway has been considered a novel therapeutic strategy to treat human cancers that harbor aberrantly-active STAT3. In this study, a series of small molecules were identified as novel inhibitors of STAT3 signaling pathway through virtual screening. A tricyclic scaffold containing compound, 6, was identified as an inhibitor of IL-6/STAT3 signaling with an IC50 of 26.68 μM. In addition, this compound inhibited Tyr705 phosphorylation of STAT3 and had no obvious effect on upstream tyrosine kinases. Thus, compound 6 is a potential lead structure and valuable for further drug development.

Fragment-based drug design and identification of HJC0123, a novel orally bioavailable STAT3 inhibitor for cancer therapy

Fragment-based drug design (FBDD) is a promising approach for the generation of lead molecules with enhanced activity and especially drug-like properties against therapeutic targets. Herein, we report the fragment-based drug design, systematic chemical synthesis and pharmacological evaluation of novel scaffolds as potent anticancer agents by utilizing six privileged fragments from known STAT3 inhibitors. Several new molecules such as compounds 5, 12, and 19 that may act as advanced chemical leads have been identified. The most potent compound 5 (HJC0123) has demonstrated to inhibit STAT3 promoter activity, downregulate phosphorylation of STAT3, increase the expression of cleaved caspase-3, inhibit cell cycle progression and promote apoptosis in breast and pancreatic cancer cells with low micromolar to nanomolar IC50 values. Furthermore, compound 5 significantly suppressed estrogen receptor (ER)-negative breast cancer MDA-MB-231 xenograft tumor growth in vivo (p.o.), indicating its great potential as an efficacious and orally bioavailable drug candidate for human cancer therapy.

Drug repositioning by structure-based virtual screening

Approved drugs have favourable or validated pharmacokinetic properties and toxicological profiles, and the repositioning of existing drugs for new indications can potentially avoid expensive costs associated with early-stage testing of the hit compounds. In recent years, technological advances in virtual screening methodologies have allowed medicinal chemists to rapidly screen drug libraries for therapeutic activity against new biomolecular targets in a cost-effective manner. This review article outlines the basic principles and recent advances in structure-based virtual screening and highlights the powerful synergy of in silico techniques in drug repositioning as demonstrated in several recent reports.