A dual-action niclosamide-based prodrug that targets cancer stem cells and inhibits TNBC metastasis.

Chemotherapy typically destroys the tumor mass but rarely eradicates the cancer stem cells (CSCs) that can drive metastatic recurrence. A key current challenge is finding ways to eradicate CSCs and suppress their characteristics. Here, we report a prodrug, Nic-A, created by combining a carbonic anhydrase IX (CAIX) inhibitor, acetazolamide, with a signal transducer and transcriptional activator 3 (STAT3) inhibitor, niclosamide. Nic-A was designed to target triple-negative breast cancer (TNBC) CSCs and was found to inhibit both proliferating TNBC cells and CSCs via STAT3 dysregulation and suppression of CSC-like properties. Its use leads to a decrease in aldehyde dehydrogenase 1 activity, CD44high/CD24low stem-like subpopulations, and tumor spheroid-forming ability. TNBC xenograft tumors treated with Nic-A exhibited decreased angiogenesis and tumor growth, as well as decreased Ki-67 expression and increased apoptosis. In addition, distant metastases were suppressed in TNBC allografts derived from a CSC-enriched population. This study thus highlights a potential strategy for addressing CSC-based cancer recurrence.

Niclosamide-loaded nanoparticles disrupt Candida biofilms and protect mice from mucosal candidiasis.

Candida albicans biofilms are a complex multilayer community of cells that are resistant to almost all classes of antifungal drugs. The bottommost layers of biofilms experience nutrient limitation where C. albicans cells are required to respire. We previously reported that a protein Ndu1 is essential for Candida mitochondrial respiration; loss of NDU1 causes inability of C. albicans to grow on alternative carbon sources and triggers early biofilm detachment. Here, we screened a repurposed library of FDA-approved small molecule inhibitors to identify those that prevent NDU1-associated functions. We identified an antihelminthic drug, Niclosamide (NCL), which not only prevented growth on acetate, C. albicans hyphenation and early biofilm growth, but also completely disengaged fully grown biofilms of drug-resistant C. albicans and Candida auris from their growth surface. To overcome the suboptimal solubility and permeability of NCL that is well known to affect its in vivo efficacy, we developed NCL-encapsulated Eudragit EPO (an FDA-approved polymer) nanoparticles (NCL-EPO-NPs) with high niclosamide loading, which also provided long-term stability. The developed NCL-EPO-NPs completely penetrated mature biofilms and attained anti-biofilm activity at low microgram concentrations. NCL-EPO-NPs induced ROS activity in C. albicans and drastically reduced oxygen consumption rate in the fungus, similar to that seen in an NDU1 mutant. NCL-EPO-NPs also significantly abrogated mucocutaneous candidiasis by fluconazole-resistant strains of C. albicans, in mice models of oropharyngeal and vulvovaginal candidiasis. To our knowledge, this is the first study that targets biofilm detachment as a target to get rid of drug-resistant Candida biofilms and uses NPs of an FDA-approved nontoxic drug to improve biofilm penetrability and microbial killing.

Niclosamide, but not ivermectin, inhibits anoctamin 1 and 6 and attenuates inflammation of the respiratory tract.

Inflammatory airway diseases like cystic fibrosis, asthma and COVID-19 are characterized by high levels of pulmonary cytokines. Two well-established antiparasitic drugs, niclosamide and ivermectin, are intensively discussed for the treatment of viral inflammatory airway infections. Here, we examined these repurposed drugs with respect to their anti-inflammatory effects in airways in vivo and in vitro. Niclosamide reduced mucus content, eosinophilic infiltration and cell death in asthmatic mouse lungs in vivo and inhibited release of interleukins in the two differentiated airway epithelial cell lines CFBE and BCi-NS1.1 in vitro. Cytokine release was also inhibited by the knockdown of the Ca2+-activated Cl- channel anoctamin 1 (ANO1, TMEM16A) and the phospholipid scramblase anoctamin 6 (ANO6, TMEM16F), which have previously been shown to affect intracellular Ca2+ levels near the plasma membrane and to facilitate exocytosis. At concentrations around 200 nM, niclosamide inhibited inflammation, lowered intracellular Ca2+, acidified cytosolic pH and blocked activation of ANO1 and ANO6. It is suggested that niclosamide brings about its anti-inflammatory effects at least in part by inhibiting ANO1 and ANO6, and by lowering intracellular Ca2+ levels. In contrast to niclosamide, 1 µM ivermectin did not exert any of the effects described for niclosamide. The present data suggest niclosamide as an effective anti-inflammatory treatment in CF, asthma, and COVID-19, in addition to its previously reported antiviral effects. It has an advantageous concentration-response relationship and is known to be well tolerated.

Wnt Signaling Modulators Exhibit Neuroprotective Effects via Combating Astrogliosis and Balancing Synaptic Density at Early and Late Stage Temporal Lobe Epilepsy.

Temporal Lobe Epilepsy (TLE) is a severe neurological condition characterized by recurrent seizures that often do not respond well to available anti-seizure medications. TLE has been associated with epileptogenesis, a process that starts during the latent period following a neurologic insult and is followed by chronic phase. Recent research has linked canonical Wnt signaling to the pathophysiology of epileptogenesis and TLE. Our previous study demonstrated differential regulation of canonical Wnt signaling during early and late stage post status epilepticus (SE) induction. Building on these findings, our current study utilized Wnt modulators: GSK-3ß inhibitor 6-bromoindirubin-3'-oxime (6-Bio) and disheveled inhibitor niclosamide and investigated their impact on canonical Wnt signaling during the early (30 days) and later stages (60 days) following SE induction. We assessed several parameters, including seizure frequency, astrogliosis, synaptic density, and neuronal counts in hippocampal tissue. We used immunohistochemistry and Nissl staining to evaluate gliosis, synaptic density, and neuronal counts in micro-dissected hippocampi. Western blotting was used to examine the expression of proteins involved in canonical Wnt/ß-catenin signaling, and real-time PCR was conducted to analyze their relative mRNA expression. Wnt modulators, 6-Bio and Niclosamide were found to reduce seizure frequency and various other parameters including behavioral parameters, hippocampal morphology, astrogliosis and synaptic density at different stages of TLE.

In vitro synergistic antiviral activity of repurposed drugs against enterovirus 71.

Enteroviruses cause viral diseases that are harmful to children. Hand, foot, and mouth disease (HFMD) with neurological complications is mainly caused by enterovirus 71 (EV71). Despite its clinical importance, there is no effective antiviral drug against EV71. However, several repurposed drugs have been shown to have antiviral activity against related viruses. Treatments with single drugs and two-drug combinations were performed in vitro to assess anti-EV71 activity. Three repurposed drug candidates with broad-spectrum antiviral activity were found to demonstrate potent anti-EV71 activity: prochlorperazine, niclosamide, and itraconazole. To improve antiviral activity, combinations of two drugs were tested. Niclosamide and itraconazole showed synergistic antiviral activity in Vero cells, whereas combinations of niclosamide-prochlorperazine and itraconazole-prochlorperazine showed only additive effects. Furthermore, the combination of itraconazole and prochlorperazine showed an additive effect in neuroblastoma cells. Itraconazole and prochlorperazine exert their antiviral activities by inhibiting Akt phosphorylation. Repurposing of drugs can provide a treatment solution for HFMD, and our data suggest that combining these drugs can enhance that efficacy.

Repurposing Niclosamide as a plausible neurotherapeutic in autism spectrum disorders, targeting mitochondrial dysfunction: a strong hypothesis.

Autism Spectrum Disorders (ASD) are a complex set of neurodevelopmental manifestations which present in the form of social and communication deficits. Affecting a growing proportion of children worldwide, the exact pathogenesis of this disorder is not very well understood, and multiple signaling pathways have been implicated. Among them, the ERK/MAPK pathway is critical in a number of cellular processes, and the normal functioning of neuronal cells also depends on this cascade. As such, recent studies have increasingly focused on the impact this pathway has on the development of autistic symptoms. Improper ERK signaling is suspected to be involved in neurotoxicity, and the same might be implicated in autism spectrum disorders (ASD), through a variety of effects including mitochondrial dysfunction and oxidative stress. Niclosamide, an antihelminthic and anti-inflammatory agent, has shown potential in inhibiting this pathway, and countering the effects shown by its overactivity in inflammation. While it has previously been evaluated in other neurological disorders like Alzheimer's Disease and Parkinson's Disease, as well as various cancers by targeting ERK/MAPK, it's efficacy in autism has not yet been evaluated. In this article, we attempt to discuss the potential role of the ERK/MAPK pathway in the pathogenesis of ASD, specifically through mitochondrial damage, before moving to the therapeutic potential of niclosamide in the disorder, mediated by the inhibition of this pathway and its detrimental effects of neuronal development.

The Antifungal Potential of Niclosamide and Structurally Related Salicylanilides.

Human mycoses cover a diverse field of fungal diseases from skin disorders to systemic invasive infections and pose an increasing global health problem based on ineffective treatment options, the hampered development of new efficient drugs, and the emergence of resistant fungal strains. Niclosamide is currently applied for the treatment of worm infections. Its mechanisms of action, which include the suppression of mitochondrial oxidative phosphorylation (also known as mitochondrial uncoupling), among others, has led to a repurposing of this promising anthelmintic drug for the therapy of further human diseases such as cancer, diabetes, and microbial infections. Given the urgent need to develop new drugs against fungal infections, the considerable antifungal properties of niclosamide are highlighted in this review. Its chemical and pharmacological properties relevant for drug development are also briefly mentioned, and the described mitochondria-targeting mechanisms of action add to the current arsenal of approved antifungal drugs. In addition, the activities of further salicylanilide-based niclosamide analogs against fungal pathogens, including agents applied in veterinary medicine for many years, are described and discussed for their feasibility as new antifungals for humans. Preliminary structure-activity relationships are determined and discussed. Various salicylanilide derivatives with antifungal activities showed increased oral bioavailabilities when compared with niclosamide. The simple synthesis of salicylanilide-based drugs also vouchsafes a broad and cost-effective availability for poorer patient groups. Pertinent literature is covered until 2024.

Repurposing Niclosamide to Modulate Renal RNA-Binding Protein HuR for the Treatment of Diabetic Nephropathy in db/db Mice.

Hu antigen R (HuR) plays a key role in regulating genes critical to the pathogenesis of diabetic nephropathy (DN). This study investigates the therapeutic potential of niclosamide (NCS) as an HuR inhibitor in DN. Uninephrectomized mice were assigned to four groups: normal control; untreated db/db mice terminated at 14 and 22 weeks, respectively; and db/db mice treated with NCS (20 mg/kg daily via i.p.) from weeks 18 to 22. Increased HuR expression was observed in diabetic kidneys from db/db mice, which was mitigated by NCS treatment. Untreated db/db mice exhibited obesity, progressive hyperglycemia, albuminuria, kidney hypertrophy and glomerular mesangial matrix expansion, increased renal production of fibronectin and a-smooth muscle actin, and decreased glomerular WT-1+-podocytes and nephrin expression. NCS treatment did not affect mouse body weight, but reduced blood glucose and HbA1c levels and halted the DN progression observed in untreated db/db mice. Renal production of inflammatory and oxidative stress markers (NF-κBp65, TNF-a, MCP-1) and urine MDA levels increased during disease progression in db/db mice but were halted by NCS treatment. Additionally, the Wnt1-signaling-pathway downstream factor, Wisp1, was identified as a key downstream mediator of HuR-dependent action and found to be markedly increased in db/db mouse kidneys, which was normalized by NCS treatment. These findings suggest that inhibition of HuR with NCS is therapeutic for DN by improving hyperglycemia, renal inflammation, and oxidative stress. The reduction in renal Wisp1 expression also contributes to its renoprotective effects. This study supports the potential of repurposing HuR inhibitors as a novel therapy for DN.

Targeting the epithelial-mesenchymal transition (EMT) pathway with combination of Wnt inhibitor and chalcone complexes in lung cancer cells.

Non-small cell lung cancer (NSCLC) is the most common type of the lung cancer. Despite development in treatment options in NSCLC, the overall survival ratios is still poor due to epithelial and mesenchymal transition (EMT) feature and associated metastasis event. Thereby there is a need to develop strategy to increase antitumor response against the NSCLC cells by targeting EMT pathway with combination drugs. Niclosamide and chalcone complexes are both affect cancer cell signaling pathways and therefore inhibit the EMT pathway. In this study, it was aimed to increase antitumor response and suppress EMT pathway in NSCLC cells by combining niclosamide and chalcone complexes. SRB cell viability assay was performed to investigate the anticancer activity of drugs. The drugs were tested on both NSCLC cells (A549 and H1299) and normal lung bronchial cells (BEAS-2B). Then the two drugs were combined and their effects on cancer cells were evaluated. Fluorescence imaging and enzyme-linked immunosorbent assay were performed on treated cells to observe the cell death manner. Wound healing assay, real-time quantitative polymerase chain reaction, and western blot analysis were performed to measure EMT pathway activity. Our results showed that niclosamide and chalcone complexes combination kill cancer cells more than normal lung bronchial cells. Compared to single drug administration, the combination of both drugs killed NSCLC cells more effectively by increasing apoptotic activity. In addition, the combination of niclosamide and chalcone complexes decreased multidrug resistance and EMT activity by lowering their gene expressions and protein levels. These results showed that niclosamide and chalcone complexes combination could be a new drug combination for the treatment of NSCLC.

Mitochondrial uncouplers impair human sperm motility without altering ATP content†.

In human spermatozoa, the electrochemical potentials across the mitochondrial and plasma membranes are related to sperm functionality and fertility, but the exact role of each potential has yet to be clarified. Impairing sperm mitochondrial function has been considered as an approach to creating male or unisex contraceptives, but it has yet to be shown whether this approach would ultimately block the ability of sperm to reach or fertilize an egg. To investigate whether the mitochondrial and plasma membrane potentials are necessary for sperm fertility, human sperm were treated with two small-molecule mitochondrial uncouplers (niclosamide ethanolamine and BAM15) that depolarize membranes by inducing passive proton flow, and evaluated the effects on a variety of sperm physiological processes. BAM15 specifically uncoupled human sperm mitochondria while niclosamide ethanolamine induced proton current in the plasma membrane in addition to depolarizing the mitochondria. In addition, both compounds significantly decreased sperm progressive motility with niclosamide ethanolamine having a more robust effect. However, these uncouplers did not reduce sperm adenosine triphosphate (ATP) content or impair other physiological processes, suggesting that human sperm can rely on glycolysis for ATP production if mitochondria are impaired. Thus, systemically delivered contraceptives that target sperm mitochondria to reduce their ATP production would likely need to be paired with sperm-specific glycolysis inhibitors. However, since niclosamide ethanolamine impairs sperm motility through an ATP-independent mechanism, and niclosamide is FDA approved and not absorbed through mucosal membranes, it could be a useful ingredient in on-demand, vaginally applied contraceptives.

Strategies to target SARS-CoV-2 entry and infection using dual mechanisms of inhibition by acidification inhibitors.

Many viruses utilize the host endo-lysosomal network for infection. Tracing the endocytic itinerary of SARS-CoV-2 can provide insights into viral trafficking and aid in designing new therapeutic strategies. Here, we demonstrate that the receptor binding domain (RBD) of SARS-CoV-2 spike protein is internalized via the pH-dependent CLIC/GEEC (CG) endocytic pathway in human gastric-adenocarcinoma (AGS) cells expressing undetectable levels of ACE2. Ectopic expression of ACE2 (AGS-ACE2) results in RBD traffic via both CG and clathrin-mediated endocytosis. Endosomal acidification inhibitors like BafilomycinA1 and NH4Cl, which inhibit the CG pathway, reduce the uptake of RBD and impede Spike-pseudoviral infection in both AGS and AGS-ACE2 cells. The inhibition by BafilomycinA1 was found to be distinct from Chloroquine which neither affects RBD uptake nor alters endosomal pH, yet attenuates Spike-pseudovirus entry. By screening a subset of FDA-approved inhibitors for functionality similar to BafilomycinA1, we identified Niclosamide as a SARS-CoV-2 entry inhibitor. Further validation using a clinical isolate of SARS-CoV-2 in AGS-ACE2 and Vero cells confirmed its antiviral effect. We propose that Niclosamide, and other drugs which neutralize endosomal pH as well as inhibit the endocytic uptake, could provide broader applicability in subverting infection of viruses entering host cells via a pH-dependent endocytic pathway.

Niclosamide inhibits TGF-ß1-induced fibrosis of human Tenon's fibroblasts by regulating the MAPK-ERK1/2 pathway.

Preventing postoperative bleb scar formation is an effective way of improving glaucoma filtration surgery (GFS) outcome. Use of more effective antifibrotic drugs with fewer adverse effects may be a good way to address the problem. In the present study, we use a primary cell model, consisting of Tenon's fibroblasts obtained from patients with glaucoma, which were stimulated with TGF-ß1 to induce the fibrotic phenotype. We explored the effects of niclosamide on TGF-ß1-induced fibrosis in these cells and examined its underlying mechanism of action. A transcriptome sequencing assay was used to explore possible signaling pathways involved. Niclosamide inhibited cell proliferation and migration, and decreased the levels of alpha-smooth muscle actin, type I and type III collagen in human Tenon's fibroblasts induced by TGF-ß1. Niclosamide also induced apoptosis and counteracted TGF-ß1-induced cytoskeletal changes and extracellular matrix accumulation. Moreover, niclosamide decreased TGF-ß1-induced phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) protein expression in human Tenon's fibroblasts. The results indicate that niclosamide inhibits TGF-ß1-induced fibrosis in human Tenon's fibroblasts by blocking the MAPK-ERK1/2 signaling pathway. Thus, niclosamide is a potentially promising antifibrotic drug that could improve glaucoma filtration surgery success rate.

SAR study of niclosamide derivatives for neuroprotective function in SH-SY5Y neuroblastoma.

Neurodegenerative disease is a debilitating and incurable condition that affects millions of people around the world. The loss of functions or malfunctions of neural cells are the causes of mortality. A proteosome inhibitor, MG132, is well known to cause neurodegeneration in vitro when model neuronal-derived cell lines are exposed to it. Niclosamide, an anthelmintic drug, which has been used to treat tapeworm infections for more than 50 years, has recently attracted renewed attention in drug repurposing because it has been found to be a good candidate in many drug development screenings. We recently found that all markers of MG132-induced neuronal cell toxicity, including the accumulation of ubiquitinated proteins, were prevented by the presence of niclosamide. In addition, niclosamide was shown to enhance autophagy induced by MG132. There results suggested that niclosamide could act as a neuroprotective agent. In the present study, niclosamide derivatives were synthesized, and the structure-activity relationship (SAR) were determined with respect to protein ubiquitination induced by MG132 and effect on cell survival signaling pathways for neuroprotective function. Our results indicate that phenol OH plays a significant role in neuroprotective activity while the niclosamide derivatives without Cl (5- or 2'-Cl) showed almost the same neuroprotective effect. 4'-NO2 can be replaced by N3 or CF3 whereas NH2 significantly decreased activity. These findings provide guidance for the development of new niclosamide analogues against neurodegenerative diseases including Parkinson's disease.

Salicylanilides and Their Anticancer Properties.

Salicylanilides are pharmacologically active compounds with a wide spectrum of biological effects. Halogenated salicylanilides, which have been used for decades in human and veterinary medicine as anthelmintics, have recently emerged as candidates for drug repurposing in oncology. The most prominent example of salicylanilide anthelmintic, that is intensively studied for its potential anticancer properties, is niclosamide. Nevertheless, recent studies have discovered extensive anticancer potential in a number of other salicylanilides. This potential of their anticancer action is mediated most likely by diverse mechanisms of action such as uncoupling of oxidative phosphorylation, inhibition of protein tyrosine kinase epidermal growth factor receptor, modulation of different signaling pathways as Wnt/ß-catenin, mTORC1, STAT3, NF-κB and Notch signaling pathways or induction of B-Raf V600E inhibition. Here we provide a comprehensive overview of the current knowledge about the proposed mechanisms of action of anticancer activity of salicylanilides based on preclinical in vitro and in vivo studies, or structural requirements for such an activity.

Antitumor effect and metabonomics of niclosamide micelles.

Polymer micelles now have promising applications in the treatment of cancer, increasing the water solubility and bioavailability of drugs. Previous studies have found that micelles of niclosamide have good anti-liver cancer effect. In view of the poor water solubility of niclosamide (NIC), we decided to prepare niclosamide micelles. However, its therapeutic mechanism is not clear, so this paper conducted a preliminary study on its vitro anti-tumour mechanism and metabonomics to find out its impact. It was found that the drug-loaded micelles (PEG2K -FIbu/NIC) had an inhibitory effect on HepG2 cells. Moreover, it can promote apoptosis of HepG2 cells and block S and G2/M phase of cell cycle. The plasma and liver metabolomics of mice in normal group, model group and administration group were studied by UPLC-MS and 1 H-NMR. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to process the data and find the relevant metabolites. metaboanalyst 5.0 was used to integrate the relevant metabolites to find the main related metabolic pathways. Thus, the anti-tumour mechanism of PEG2K -FIbu/NIC was analysed. Fifty-one biomarkers were detected in plasma, and 43 biomarkers were detected in liver. After comprehensive biomarker and metabolic pathway analysis, it was found that PEG2K -FIbu/NIC micelles could affect the changes of many metabolites, mainly affecting amino acid metabolism. This article is an in-depth study based on the published Preparation and pharmacodynamics of niclosamide micelles (DOI: 10.1016/j.jddst.2021.103088).

Harnessing autophagy to fight SARS-CoV-2: An update in view of recent drug development efforts.

Drug repurposing is an attractive option for identifying new treatment strategies, in particular in extraordinary situations of urgent need such as the current coronavirus disease 2019 (Covid-19) pandemic. Recently, the World Health Organization announced testing of three drugs as potential Covid-19 therapeutics that are known for their dampening effect on the immune system. Thus, the underlying concept of selecting these drugs is to temper the potentially life-threatening overshooting of the immune system reacting to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. This viewpoint discusses the possibility that the impact of these and other drugs on autophagy contributes to their therapeutic effect by hampering the SARS-CoV-2 life cycle.

Adaptation of clinical isolates of Klebsiella pneumoniae to the combination of niclosamide with the efflux pump inhibitor phenyl-arginine-ß-naphthylamide (PaßN): co-resistance to antimicrobials.

OBJECTIVES: To search for new means of combatting carbapenemase-producing strains of Klebsiella pneumoniae by repurposing the anti-helminth drug niclosamide as an antimicrobial agent and combining it with the efflux pump inhibitor (EPI) phenyl-arginine-ß-naphthylamide (PaßN). METHODS: Niclosamide and PaßN MICs were determined for six clinical K. pneumoniae isolates harbouring different carbapenemases by broth microdilution and chequerboard assays. Time-kill curves in the presence of each drug alone and in combination were conducted. The viability of bacterial cells in the presence of repetitive exposures at 8 h to the treatment at the same concentration of niclosamide and/or PaßN (adapted isolates) was determined. The acrAB-tolC genes and their regulators were sequenced and quantitative RT-PCR was performed to assess whether the acrA gene was overexpressed in adapted isolates compared with non-adapted isolates. Finally, the MICs of several antimicrobials were determined for the adapted isolates. RESULTS: Niclosamide and PaßN had synergistic effects on the six isolates in vitro, but adaptation appeared when the treatment was applied to the medium every 8 h, with an increase of 6- to 12-fold in the MIC of PaßN. Sequencing revealed different mutations in the regulators of the tripartite AcrAB-TolC efflux pump (ramR and acrR) that may be responsible for the overexpression of the efflux pump and the adaptation to this combination. Co-resistance to different antimicrobials confirmed the overexpression of the AcrAB-TolC efflux pump. CONCLUSIONS: Despite the synergistic effect that preliminary in vitro stages may suggest, the combinations of drugs and EPI may generate adapted phenotypes associated with antimicrobial resistance that must be taken into consideration.

Niclosamide as a repurposing drug against Gram-positive bacterial infections.

OBJECTIVES: Niclosamide is commonly used as an antiparasitic drug in veterinary clinics. The objectives of this study were to evaluate the efficacy of niclosamide against resistant Gram-positive bacteria in vitro and in an in vivo experimental model of topical bacterial infection. Moreover, to study the antibacterial mechanism of niclosamide to Staphylococcus aureus. METHODS: A mouse topical infection model was established to detect the antibacterial activity of niclosamide in vivo. The antimicrobial mechanism was probed by visualizing the bacterial morphologies using scanning electron microscopy and transmission electron microscopy. Moreover, the haemolytic assay and western blotting analysis were performed to evaluate whether niclosamide could inhibit the secretion of alpha-haemolysin (α-HL) from S. aureus. RESULTS: The MICs of niclosamide were below 0.5 mg/L for Gram-positive bacteria, showing excellent antibacterial activity in vitro. The in vivo antibacterial activity results indicated that niclosamide treatment at 10 mg/kg of body weight caused a significant reduction in the abscess area and the number of S. aureus cells. Moreover, the antibacterial mechanism of niclosamide showed that the surface morphology of S. aureus displayed noticeable shrinkage, with an increasing number of small vacuole-like structures observed as the drug concentration increased. Intracellular ATP levels were found to decrease in a niclosamide dose-dependent manner. Haemolysis and western blotting analyses revealed that niclosamide inhibited the haemolytic activity of S. aureus by inhibiting α-HL expression under subinhibitory concentration conditions. CONCLUSIONS: Niclosamide has significant potential for development into drugs that prevent and treat diseases caused by Gram-positive bacteria such as Staphylococcus and Streptococcus.

Efficacy of niclosamide on the intra-abdominal inflammatory environment in endometriosis.

Endometriosis, a common gynecological disease, causes chronic pelvic pain and infertility in women of reproductive age. Due to the limited efficacy of current therapies, a critical need exists to develop new treatments for endometriosis. Inflammatory dysfunction, instigated by abnormal macrophage (MΦ) function, contributes to disease development and progression. However, the fundamental role of the heterogeneous population of peritoneal MΦ and their potential druggable functions is uncertain. Here we report that GATA6-expressing large peritoneal MΦ (LPM) were increased in the peritoneal cavity following lesion induction. This was associated with increased cytokine and chemokine secretion in the peritoneal fluid (PF), as well as MΦ infiltration, vascularization and innervation in endometriosis-like lesions (ELL). Niclosamide, an FDA-approved anti-helminthic drug, was effective in reducing LPM number, but not small peritoneal MΦ (SPM), in the PF. Niclosamide also inhibits aberrant inflammation in the PF, ELL, pelvic organs (uterus and vagina) and dorsal root ganglion (DRG), as well as MΦ infiltration, vascularization and innervation in the ELL. PF from ELL mice stimulated DRG outgrowth in vitro, whereas the PF from niclosamide-treated ELL mice lacked the strong stimulatory nerve growth response. These results suggest LPM induce aberrant inflammation in endometriosis promoting lesion progression and establishment of the inflammatory environment that sensitizes peripheral nociceptors in the lesions and other pelvic organs, leading to increased hyperalgesia. Our findings provide the rationale for targeting LPM and their functions with niclosamide and its efficacy in endometriosis as a new non-hormonal therapy to reduce aberrant inflammation which may ultimately diminish associated pain.

Synthesis and biological evaluation of niclosamide PROTACs.

Roughly 268,000 new cases of prostate cancer and 34,000 deaths from prostate cancer are projected by the American Cancer Society to occur in the United States in 2022. Androgen receptor is a key protein in the proliferation and survival of prostate cancer cells and has been revealed to be overexpressed in 30% to 50% of castration-resistant prostate cancer patients. One promising approach to reducing the level of this protein is Proteolysis Targeting Chimeras (PROTACs) that is an emerging drug discovery technology. PROTACs are hetero-bifunctional molecules where one end binds to a protein of interest and the other to an E3 ligase ligand, initiating the Ubiquitin-Proteasome Pathway for protein degradation. Two PROTACs with niclosamide as androgen receptor ligand and VHL-032 as the E3 ligase ligand have been designed and synthesized for suppressing proliferation of androgen receptor-positive prostate cancer cells via degrading androgen receptor. The in vitro antiproliferative assessment suggested that they can selectively suppress PC-3, LNCaP, and 22Rv1 prostate cancer cell proliferation, but cannot inhibit DU145 cell proliferation. However, the mechanism of both compounds in suppressing prostate cancer cell proliferation is not through the AR PROTAC mechanism because they did not degrade AR in our Western Blotting assay up to 1 µM.