Campylobacter jejuni and Campylobacter coli are major foodborne pathogens. We announce the deposition of Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS) proteomic data sets from PBT2-treated and untreated cultures. These data sets provide a resource for investigating the proteomic response of Campylobacter spp. to the antimicrobial ionophore PBT2.

Background and objectives Enterococcus faecium and Staphylococcus aureus are opportunistic bacterial pathogens with a demonstrated capacity to develop antimicrobial resistance and cause serious life-threatening infections, underscoring the urgent need for new therapeutic options.Methods Here, we have synthesized and characterized the activities of an 8-hydroxyquinoline-based ionophore antibiotic (ionophoroantibiotic; IP antibiotic), designated 'IP-antibiotic 12.'Results Using multidrug-resistant strains of E. faecium and S. aureus, in vitro investigations revealed that IP-antibiotic 12 exhibits bactericidal activity, demonstrates a low propensity for resistance emergence, increases the susceptibility of particular strains to select antibiotics, possesses a favorable toxicity profile, and dysregulates bacterial metal homeostasis. IP-antibiotic 12 demonstrated therapeutic efficacy against multidrug-resistant S. aureus skin infection, as a direct-acting topical antimicrobial and antibiotic adjunct when co-administered with oral linezolid. Interestingly, it was not efficacious in murine models of systemic and pulmonary infection.Conclusions These results highlight the potential of IP-antibiotic 12 as a novel therapeutic against multidrug-resistant gram-positive bacteria and provide a foundation for the development of next-generation IP-antibiotics with enhanced in vivo therapeutic efficacy.

Helicobacter pylori colonizes the gastric mucosa of around half of the world's population and is a major cause of chronic gastritis, peptic ulcer disease, and gastric cancer. Current therapies are becoming increasingly ineffective due to the rapid spread of antibiotic resistance, creating an urgent need for new treatment options with distinct mechanisms of action. Drug repurposing offers a practical and cost-effective approach to address this gap. PBT2 is an 8-hydroxyquinoline derivative originally developed for the treatment of neurodegenerative diseases and has more recently been shown to possess antimicrobial activity. In this study, we demonstrate that PBT2 displays potent bactericidal activity against H. pylori, including multidrug-resistant clinical isolates. PBT2 rapidly killed H. pylori in vitro at low concentrations, with faster killing kinetics than commonly used antibiotics, and no resistance was detected after 30 days of continuous exposure. Importantly, PBT2 was effective in clearing an H. pylori infection in a murine model. Quantitative sequential window acquisition of all theoretical-mass spectrometry proteomic analysis revealed that PBT2 triggers broad disruption of essential bacterial processes, including global suppression of translation, impairment of iron-sulfur cluster assembly and respiration, dysregulation of metal homeostasis, and reduced abundance of virulence- and motility-associated proteins. We reported that PBT2 can act as a nickel ionophore, with Ni2+ being the highest-affinity ligand for PBT2 reported to date. Together, these findings suggest that PBT2 acts through a multifaceted, metal-dependent mode of action that limits the potential for emergence of resistance. Our work highlights PBT2 as a promising candidate for repurposing to treat multidrug-resistant H. pylori infections.IMPORTANCEAntibiotic resistance is steadily reducing our ability to treat common bacterial infections, while the development of new antibiotics has slowed. Helicobacter pylori is a clear example of this growing problem, with treatment failures becoming more common worldwide. This study highlights the value of taking a different approach by repurposing existing drugs for new antibacterial uses. Rather than acting on a single bacterial target, the compound examined here disrupts multiple essential processes at once, reducing the probability of resistance developing.

3-Fluoroneuraminosyl fluorides are invaluable probes for studying the catalytic mechanism of sialidases (neuraminidases), and as sialidase inhibitors. Significantly, when a C-3 equatorial fluorine is installed on a C-4 functionalised N-acylneuraminic acid (Neu)-based template, the compounds are potent and selective inhibitors of both influenza and parainfluenza sialidases, and of virus replication. Typically, the reported syntheses of 3-fluoroneuraminosyl fluorides involve either an enzymatic or a chemical synthesis that have uncontrolled stereoselectivity in the introduction of fluorine at C-3 of Neu and consequently yield a mixture of C-3 ax and C-3 eq fluoro derivatives. We now report a simple approach for the exquisitely stereo-controlled introduction of the C-3 equatorial fluorine on Neu by incorporation of steric bulk at C-4. Through this method, we have elaborated a novel synthetic route that exclusively produces the potent anti-influenza drug candidate; 2,3-difluoro-zanamivir analogue with C-3 eq fluoride.

The rise of multidrug-resistant (MDR) Neisseria gonorrhoeae is a growing health concern. New treatments are urgently needed as resistance to last-line antibiotics increases. The zinc ionophore, PBT2, has previously been shown to facilitate zinc uptake in bacteria and restore susceptibility to existing antibiotics in combination therapies. In contrast, we demonstrate that PBT2 alone is sufficient to inhibit the growth of N. gonorrhoeae. Guided by this finding, we synthesized a series of 8-hydroxyquinoline-based new chemical entities, herein termed a "ionophoroantibiotics (IP-antibiotics)." These compounds displayed potent activity against MDR N. gonorrhoeae, with several exhibiting greater efficacy than PBT2. Proteomic profiling studies suggested IP-antibiotics disrupt metal and phosphate metabolism in N. gonorrhoeae, upregulating iron transport and downregulating phosphate pathways. PBT2 broadly affects metal and metabolic proteins, whereas the new compounds act more selectively. This distinct mode of action circumvents established resistance mechanisms and targets key bacterial vulnerabilities. Collectively, these findings identify IP-antibiotics as a promising new class of antibiotics for the treatment of MDR N. gonorrhoeae.

Fibrillarin (FBL) is an essential and evolutionarily highly conserved S-adenosyl methionine (SAM) dependent methyltransferase. It is the catalytic component of a multiprotein complex that facilitates 2′-O-methylation of ribosomal RNAs (rRNAs), a modification essential for accurate and efficient protein synthesis in eukaryotic cells. It was recently established that human FBL (hFBL) is critical for Nipah, Hendra, and respiratory syncytial virus infections. In addition, overexpression of hFBL contributes towards tumorgenesis and is associated with poor survival in patients with breast cancer, suggesting that hFBL is a potential target for the development of both antiviral and anticancer drugs. An attractive strategy to target cofactor-dependent enzymes is the selective inhibition of cofactor binding, which has been successful for the development of inhibitors against several protein methyltransferases including PRMT5, DOT1L, and EZH2. In this work, we solved crystal structures of the methyltransferase domain of hFBL in apo form and in complex with the cofactor SAM. Screening of a fluorinated fragment library, via X-ray crystallography and 19F NMR spectroscopy, yielded seven hit compounds that competed with cofactor binding, two of which resulted in co-crystal structures. One of these structures revealed unexpected conformational variability in the cofactor binding site, which allows it to accommodate a compound significantly different from SAM. Our structural data provide critical information for the design of selective cofactor competitive inhibitors targeting hFBL, and preliminary elaboration of hit compounds has led to additional cofactor site binders.

Streptococcus pneumoniae is the primary cause of community-acquired bacterial pneumonia with rates of penicillin and multidrug-resistance exceeding 80% and 40%, respectively. The innate immune response generates a variety of antimicrobial agents to control infection, including zinc stress. Here, we characterize the impact of zinc intoxication on S. pneumoniae, observing disruptions in central carbon metabolism, lipid biogenesis, and peptidoglycan biosynthesis. Characterization of the pivotal peptidoglycan biosynthetic enzyme GlmU indicates a sensitivity to zinc inhibition. Disruption of the sole zinc efflux pathway, czcD, renders S. pneumoniae highly susceptible to β-lactam antibiotics. To dysregulate zinc homeostasis in the wild-type strain, we investigated the safe-for-human-use ionophore 5,7-dichloro-2-[(dimethylamino)methyl]quinolin-8-ol (PBT2). PBT2 rendered wild-type S. pneumoniae strains sensitive to a range of antibiotics. Using an invasive ampicillin-resistant strain, we demonstrate in a murine pneumonia infection model the efficacy of PBT2 + ampicillin treatment. These findings present a therapeutic modality to break antibiotic resistance in multidrug-resistant S. pneumoniae.

Multidrug-resistant (MDR) N. gonorrhoeae is a current public health threat. New therapies are urgently needed. PBT2 is an ionophore that disrupts metal homeostasis. PBT2 administered with zinc is shown to reverse resistance to antibiotics in several bacterial pathogens. Here we show that both N. meningitidis and MDR N. gonorrhoeae are sensitive to killing by PBT2 alone. PBT2 is, thus, a candidate therapeutic for MDR N. gonorrhoeae infections.

Acinetobacter baumannii causes high mortality in ventilator-associated pneumonia patients, and antibiotic treatment is compromised by multidrug-resistant strains resistant to beta-lactams, carbapenems, cephalosporins, polymyxins, and tetracyclines. Among COVID-19 patients receiving ventilator support, a multidrug-resistant A. baumannii secondary infection is associated with a 2-fold increase in mortality. Here, we investigated the use of the 8-hydroxyquinoline ionophore PBT2 to break the resistance of A. baumannii to tetracycline class antibiotics. In vitro, the combination of PBT2 and zinc with either tetracycline, doxycycline, or tigecycline was shown to be bactericidal against multidrug-resistant A. baumannii, and any resistance that did arise imposed a fitness cost. PBT2 and zinc disrupted metal ion homeostasis in A. baumannii, increasing cellular zinc and copper while decreasing magnesium accumulation. Using a murine model of pulmonary infection, treatment with PBT2 in combination with tetracycline or tigecycline proved efficacious against multidrug-resistant A. baumannii. These findings suggest that PBT2 may find utility as a resistance breaker to rescue the efficacy of tetracycline-class antibiotics commonly employed to treat multidrug-resistant A. baumannii infections. IMPORTANCE Within intensive care unit settings, multidrug-resistant (MDR) Acinetobacter baumannii is a major cause of ventilator-associated pneumonia, and hospital-associated outbreaks are becoming increasingly widespread. Antibiotic treatment of A. baumannii infection is often compromised by MDR strains resistant to last-resort beta-lactam (e.g., carbapenems), polymyxin, and tetracycline class antibiotics. During the on-going COVID-19 pandemic, secondary bacterial infection by A. baumannii has been associated with a 2-fold increase in COVID-19-related mortality. With a rise in antibiotic resistance and a reduction in new antibiotic discovery, it is imperative to investigate alternative therapeutic regimens that complement the use of current antibiotic treatment strategies. Rescuing the efficacy of existing therapies for the treatment of MDR A. baumannii infection represents a financially viable pathway, reducing time, cost, and risk associated with drug innovation.

Gram-positive bacteria do not produce lipopolysaccharide as a cell wall component. As such, the polymyxin class of antibiotics, which exert bactericidal activity against Gram-negative pathogens, are ineffective against Gram-positive bacteria. The safe-for-human-use hydroxyquinoline analog ionophore PBT2 has been previously shown to break polymyxin resistance in Gram-negative bacteria, independent of the lipopolysaccharide modification pathways that confer polymyxin resistance. Here, in combination with zinc, PBT2 was shown to break intrinsic polymyxin resistance in Streptococcus pyogenes (Group A Streptococcus; GAS), Staphylococcus aureus (including methicillin-resistant S. aureus), and vancomycin-resistant Enterococcus faecium. Using the globally disseminated M1T1 GAS strain 5448 as a proof of principle model, colistin in the presence of PBT2 + zinc was shown to be bactericidal in activity. Any resistance that did arise imposed a substantial fitness cost. PBT2 + zinc dysregulated GAS metal ion homeostasis, notably decreasing the cellular manganese content. Using a murine model of wound infection, PBT2 in combination with zinc and colistin proved an efficacious treatment against streptococcal skin infection. These findings provide a foundation from which to investigate the utility of PBT2 and next-generation polymyxin antibiotics for the treatment of Gram-positive bacterial infections.

Triple-negative breast cancer (TNBC) is a heterogeneous subtype of tumors that tests negative for estrogen receptors, progesterone receptors, and excess HER2 protein. The mainstay of treatment remains chemotherapy, but the therapeutic outcome remains inadequate. This paper investigates the potential of a duocarmycin derivative, tafuramycin A (TFA), as a new and more effective chemotherapy agent in TNBC treatment. To this extent, we optimized the chemical synthesis of TFA, and we encapsulated TFA in a micellar system to reduce side effects and increase tumor accumulation. In vitro and in vivo studies suggest that both TFA and SMA–TFA possess high anticancer effects in TNBC models. Finally, the encapsulation of TFA offered a preferential avenue to tumor accumulation by increasing its concentration at the tumor tissues by around four times in comparison with the free drug. Overall, the results provide a new potential strategy useful for TNBC treatment.

Background Neisseria gonorrhoeae is a Gram-negative bacterial pathogen that causes gonorrhoea. No vaccine is available to prevent gonorrhoea and the emergence of MDR N. gonorrhoeae strains represents an immediate public health threat. Objectives To evaluate whether PBT2/zinc may sensitize MDR N. gonorrhoeae to natural cationic antimicrobial peptides. Methods MDR strains that contain differing resistance mechanisms against numerous antibiotics were tested in MIC assays. MIC assays were performed using the broth microdilution method according to CLSI guidelines in a microtitre plate. Serially diluted LL-37 or PG-1 was tested in combination with a sub-inhibitory concentration of PBT2/zinc. Serially diluted tetracycline was also tested with sub-inhibitory concentrations of PBT2/zinc and LL-37. SWATH-MS proteomic analysis of N. gonorrhoeae treated with PBT2/zinc, LL-37 and/or tetracycline was performed to determine the mechanism(s) of N. gonorrhoeae susceptibility to antibiotics and peptides. Results Sub-inhibitory concentrations of LL-37 and PBT2/zinc synergized to render strain WHO-Z susceptible to tetracycline, whereas the killing effect of PG-1 and PBT2/zinc was additive. SWATH-MS proteomic analysis suggested that PBT2/zinc most likely leads to a loss of membrane integrity and increased protein misfolding and, in turn, results in bacterial death. Conclusions Here we show that PBT2, a candidate Alzheimer’s and Huntington’s disease drug, can be repurposed to render MDR N. gonorrhoeae more susceptible to the endogenous antimicrobial peptides LL-37 and PG-1. In the presence of LL-37, PBT2/zinc can synergize with tetracycline to restore tetracycline susceptibility to gonococci resistant to this antibiotic.

The hydroxyquinoline analog PBT2 breaks resistance to polymyxin class antibiotics in polymyxin-resistant Gram-negative bacteria.

Tafuramycin-A (TAF) is naturally occurring duocarmycin-SA derivative with known DNA alkylating and/or intercalating potential. On the other hand, TAF possesses excessive and non-specific toxic properties. Epicatechin (EPI) and thymoquinone (TQ) are naturally occurring compounds with a wide range of biological activities, such as anticancer and chemomodulatory potentials. Herein, we temporally assessed the anti-breast cancer properties of TAF alone and in combination with EPI or TQ against naive (MCF-7, MDA-MB-231 and T47D cells) and resistant breast cancer cells (MCF-7Adr). TAF alone showed very potent cell-killing properties against both naive and resistant breast cancer cell lines in a time-dependent manner with IC509s ranging from 17 - 190 nM, 2 - 19 nM and 1 - 2 nM after 24 h, 48 h, and 72 h exposures, respectively. To a lesser extent, TQ alone showed moderate cytotoxic properties against all cell lines in a time-dependent manner with IC509s ranging from 4.4 - 18.9 µM, 2.8 - 16.5 µM and 2.1 - 22.7 µM after 24 h, 48 h, and 72 h exposures, respectively. EPI was the weakest in comparison to the previous two agents with IC509s above 100 µM in all cell lines in all durations of exposure. Except 24 h exposure of MDA-MB-231 cells, equitoxic combinations of TAF with TQ showed antagonistic interaction in all cells under investigation with combination indices ranging from 2 - 9.3, 1.3 - 3.7, 1.4 - 3.2 and 0.6 - 3.7 in MCF-7, MCF-7Adr, T47D, and MDA-MB-231 cells, respectively. Combination of TAF with 10 µM EPI did not induce any prominent enhancement in TAF cytotoxic properties. Cell cycle analysis using DNA content flow cytometry showed moderate S-phase and G2/M-phase partial arrest in response to treatment with TAF, TQ and their combinations. While treatment with EPI induced significant arrest in G0/G1-phase which is similar to its reported antiproliferative activity. Further analysis for the differential apoptosis/necrosis cell death using annexin-V/FITC with PI counterstain and coupled with flow cytometric analysis showed significant necrosis induction of TAF alone against breast cancer cells under investigation. Yet, a combination of TAF with TQ or EPI decreased the percentage of necrosis induced by TAF alone; however, it induced significant apoptosis cell death. Yet, the explanation for shifting breast cancer cell death from necrosis to apoptosis due to a combination of TAF with TQ or EPI is currently under molecular investigation and might constitute a high potential in utilizing TAF for the treatment of breast cancer. Citation Format: Ohoud Y. Alshehri, Hanan A. Henidi, Fahad A. Alabbasi, Ibrahim M. El-Deeb, Majed A. Halwani, Ahmed M. Al-Abd. Thymoquinone and epicatechin ameliorate the anticancer properties of tafuramycin-A against naive and resistant breast cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6558.

Neisseria gonorrhoeae causes the sexually transmitted infection gonorrhea. High-coverage (∼3,300-fold) transcriptome sequencing data have been collected from multidrug-resistant N. gonorrhoeae strain WHO Z grown in the presence and absence of PBT2.

Neisseria gonorrhoeae (N. gonorrhoeae) causes the sexually transmitted disease gonorrhea, which has a global incidence of 106 million cases per year. No vaccine is available to prevent the disease, and the emergence of multidrug resistant (MDR) strains makes N. gonorrhoeae an immediate public health threat. Here, we show that an ionophore, PBT2, can reverse the intrinsic resistance of N. gonorrhoeae to polymyxin B and colistin. These antibiotics administered in combination with PBT2 may be an effective path to treat MDR gonococcal infections.

Human parainfluenza viruses cause acute respiratory tract infections and disease predominantly in young children and immunocompromised individuals. Currently, there are no vaccines to prevent hPIV infections, nor licensed anti-hPIV drugs. There is therefore a need for specific antiviral therapies to decrease the morbidity and mortality associated with hPIV diseases. Haemagglutinin-neuraminidase (HN) is one of two hPIV surface proteins with critical roles in host receptor recognition, binding and cleavage; it has been explored as a key drug development target for the past few decades with variable success. Recent advancements in computational modelling and the availability of the X-ray crystal structure of hPIV3 HN have improved our understanding of the structural and mechanistic features of HN. This review explores structural features of the HN protein that are being exploited for structure-guided inhibitor design. We describe past and present hPIV HN inhibition strategies based on sialic acid scaffolds, together with other novel approaches that decrease hPIV infectivity. Although many HN inhibitors have been developed and evaluated as anti-hPIV agents, currently only a host-directed therapy (DAS181) has succeeded in phase II clinical drug trials. Hence, the review concludes with future considerations for targeting the specific function(s) of hPIV HN and suggestions for antiviral drug design.

New phenylaminopyrimidine (PAP) derivatives have been designed and synthesised as potential tyrosine kinase inhibitors for the treatment of cancer. The synthesized compounds share a general structure and vary in the substitution pattern at position-2 of the pyridine ring. Several derivatives have demonstrated potent anticancer activities against HCT-116, HT-29 and LS-174T colorectal cancer cells. Furthermore, a number of hits showed good selectivity to Src-kinase. The cytotoxic mechanisms of these compounds were also investigated by studying their effects on cell-cycle distribution. Among all the compounds examined, compound 8b (with a terminal pyridin-3-yl moiety at the pyridine ring) showed the highest inhibitory selectivity towards src-kinase, which was coupled with cell cycle arrest, and apoptotic and autophagic interference, in colorectal cancer cells. This report introduces a novel category of PAP derivatives with promising kinase inhibitory and anticancer effects against colon cancer.

Human parainfluenza virus (hPIV) infections are a major cause of respiratory tract illnesses in children, with currently no available vaccine or drug treatment. The surface glycoprotein haemagglutinin-neuraminidase (HN) of hPIV has a central role in the viral life cycle, including neuraminic acid-recognising receptor binding activity (early stage) and receptor-destroying activity (late stage), which makes it an ideal target for antiviral drug disovery. In this study, we showed that targeting the catalytic mechanism of hPIV-1 HN by a 2α,3β-difluoro derivative of the known hPIV-1 inhibitor, BCX 2798, produced more potent inhibition of the neuraminidase function which is reflected by a stronger inhibition of viral replication. The difluorosialic acid-based inhibitor efficiently blocked the neuraminidase activity of HN for a prolonged period of time relative to its unsaturated neuraminic acid (Neu2en) analogue, BCX 2798 and produced a more efficient inhibition of the HN neuraminidase activity as well as in vitro viral replication. This prolonged inhibition of the hPIV-1 HN protein suggests covalent binding of the inhibitor to a key catalytic amino acid, making this compound a new lead for a novel class of more potent hPIV-1 mechanism-based inhibitors.