Antimicrobial Agents and Chemotherapy

The global dissemination of Enterobacterales producing both metallo-{beta}-lactamases (MBLs) and serine {beta}-lactamases (SBLs) represents a critical threat to modern medicine, as no currently marketed antibiotics effectively target MBL-mediated resistance. APC148 is a novel, selective zinc-chelating MBL inhibitor designed to restore {beta}-lactam activity in MBL positive isolates, when used in combination with a broad-spectrum carbapenem. In this study, we evaluated the in vitro efficacy of APC148 in triple combinations with either meropenem-avibactam (APC301) or cefepime-avibactam (APC302) against a diverse global collection (JMI collection) of 176 MBL- and SBL-producing Enterobacterales isolates (including NDM, VIM, and IMP variants). Using broth microdilution, the triple combinations were compared against several newly approved and late-stage pipeline antibiotic products. Both APC301 and APC302 demonstrated superior potency, achieving a MIC90 of 0.12 {micro}g/mL. When applying CLSI breakpoint interpretive criteria for the parent {beta}-lactams, 99.4% of the MBL and SBL-containing isolates were susceptible to APC301, while 97.2% were susceptible to APC302. These results indicate that the addition of a selective MBL inhibitor to an SBL-inhibitor/{beta}-lactam antibiotic effectively bypasses complex co-existing {beta}-lactam resistance mechanisms in multidrug-resistant (MDR) pathogens. Given that MDR Enterobacterales frequently harbor multiple {beta}-lactamase classes simultaneously, these triple combinations constitute a highly promising clinical strategy to address the therapeutic void in MBL-mediated resistance

The rise of multidrug-resistant (MDR) bacteria, particularly carbapenem-resistant Enterobacterales (CRE), poses a significant threat to public health. Infections caused by CRE, such as Escherichia coli and Klebsiella pneumoniae, are associated with high rates of antibiotic treatment failure. {beta}-lactam antibiotics, like meropenem, remain crucial in treating these infections, but their efficacy is undermined by {beta}-lactamase production. This study investigates the potential of APC24-7, a novel broad-spectrum {beta}-lactamase inhibitor (BLi) with dual activity, to restore antimicrobial activity of meropenem against CRE clinical isolates. The in-vitro analysis of a diverse panel of clinically relevant E. coli and K. pneumoniae isolates expressing both serine- and metallo-{beta}-lactamases demonstrated that APC24-7 effectively restored meropenem activity by reducing the minimum inhibitory concentrations (MICs) to below breakpoint. Time-kill assays confirmed that the combination therapy showed dose-dependent bacterial killing, with significant potentiation of meropenem activity against isolates expressing both serine- and metallo-{beta}-lactamases. In-vivo efficacy evaluation in a murine thigh infection model further confirmed APC24-7s potential to restore meropenem efficacy against meropenem resistant strains. These findings suggest that APC24-7offers a promising strategy to combat infections caused by {beta}-lactamase-producing Enterobacterales.

Cefiderocol exhibits excellent in vitro activity against Pseudomonas aeruginosa; however, resistance can emerge. We investigated the molecular mechanisms underlying cefiderocol resistance (MIC >2 mg/L) in 103 clinical strains collected from 61 hospitals (2021-2024). MICs ranged from 4 to >128 mg/L, with 39.8% of strains showing MICs >8 mg/L. Although 37.8% were classified as difficult-to-treat resistant (DTR), acquired {beta}-lactamases were detected in 72.8% of strains, including carbapenemases (39.8%), mainly NDM-1 (29.1%), and Extended Spectrum {beta}-Lactamases (ESBLs) (38.8%). Cloning of 11 {beta}-lactamases into pUCP24, including the acquired cephalosporinase PAC-1 and ESBLs (VEB-1, and VEB-9), resulted in marked increases in cefiderocol MICs (up to 128-fold). Introduction of 6 mutations in the PDC enzyme into a PAO1{Delta}blaPDC-1 background increased MICs up to 4 mg/L and conferred cross-resistance to ceftolozane/tazobactam, notably F121L, G157D, T70I, and E219K. Alterations in siderophore transporters or regulators were identified in 38.8% of strains, most frequently a PirR frameshift (R132fs), consistent with PirR inactivation, which was confirmed in the PAO1 strain to contribute to cefiderocol resistance. Overall, cefiderocol resistance in clinical strains is multifactorial, mainly involving acquired {beta}-lactamases (ESBLs, carbapenemases) and impaired siderophore uptake (PiuA/PiuD, PirA, PiuC), leading to high-level resistance (>8 mg/L). The polyclonal distribution and diversity of mechanisms highlight the need for routine susceptibility testing and surveillance. Detection of NDM producers is critical, as cefiderocol should be used with caution in this context.

BackgroundPatients undergoing hematopoietic stem cell transplantation (HSCT) often receive multiple antibiotics and antifungal agents concurrently, making it crucial to understand potential pharmacokinetic interactions. We report here an interaction between the glycopeptide antibiotic teicoplanin (TEIC) and sulfo-butyl ether-{beta}-cyclodextrin (SBECD), a solubilizing excipient in the intravenous formulation of posaconazole (PSCZ). MethodsWe performed a single-center retrospective analysis of HSCT patients who received oral and intravenous PSCZ during TEIC therapy. Associations between PSCZ administration and TEIC concentration-to-dose (C/D) ratios were evaluated using linear mixed-effects models. In rats, we examined the effects of intravenous PSCZ and SBECD on TEIC pharmacokinetics by assessing the area under the concentration-time curve (AUC) and urinary excretion of total TEIC and its components. Molecular docking and in vitro protein-binding assays were also conducted to investigate the interaction between TEIC and SBECD. ResultsIn HSCT patients, TEIC C/D ratios were significantly lower during intravenous PSCZ administration but not during oral PSCZ use. In rats, both intravenous PSCZ and SBECD decreased TEIC AUC and increased urinary excretion, particularly for the A2 group. Docking simulations indicated that the hydrophobic side chain of TEIC A2-2 fit within the SBECD cavity, and in vitro assays confirmed SBECD concentration-dependent increases in TEIC unbound fractions. ConclusionCo-administration of intravenous PSCZ containing SBECD may reduce TEIC protein binding, thereby enhancing renal elimination.

The 8-aminoquinoline family are a well-established class of antimalarial drugs containing two clinically relevant analogues, primaquine and tafenoquine. These compounds have two therapeutically significant activities across the plasmodial lifecycle; elimination of Plasmodium vivax hypnozoites as part of a radical cure (relapse prevention), and as prophylactic transmission blocking compounds. Primaquine is currently recommended as a single low (0.25 mg/kg) dose administered with artemisinin-based combination therapy to reduce malarial transmission in areas at high risk of artemisinin partial resistance. Tafenoquine was approved in 2018 for radical cure when co-administered with chloroquine however, its transmission blocking efficacy in humans has not yet been fully evaluated, and direct head-to-head comparisons of transmission-blocking efficacy of primaquine and tafenoquine have not been performed. Given that primaquine and tafenoquine are presumed to have similar mechanisms of action, tafenoquine may have potential use as a transmission blocking intervention. Furthermore, tafenoquine has a substantially longer half-life than primaquine, which could provide a pharmacokinetic advantage if such efficacy is confirmed. However, assessment of 8-aminoquinoline efficacy against the sexual stages of Plasmodium is complicated by the requirement for metabolic activation to generate parasite-reactive species, limiting the utility of in vitro assays. Here, we directly compare the transmission blocking effects of primaquine and tafenoquine using two in vivo preclinical models. We titrate the transmission blocking efficacy of each compound, and evaluate the pharmacokinetics of each compound over time, linking drug exposure to efficacy. The evidence presented here suggests that beyond 24 hours, a single dose of tafenoquine is likely to have more clinically desirable pharmacokinetics, resulting in higher transmission blocking efficacy than primaquine. These findings are observed across multiple models, both in the absence or presence of a partner schizonticide and thus demonstrate a potential advantage of the utilisation of tafenoquine when compared to primaquine.

The prevalance of non-susceptibility to ceftolozane-tazobactam (C/T) among Pseudomonas aeruginosa remains low but novel mechanisms of C/T resistance are of concern. Herein, we describe a novel Pseudomonas aeruginosa genotype associated with high-level C/T resistance (>256/4 {micro}g/mL) in a single patient. Whole genome sequencing of the isolate was compared to that of a susceptible isolate cultured from the same patient two months earlier. Analysis of the sequences revealed two different P. aeruginosa high-risk clones: ST111 followed by ST235. The C/T-resistant ST235 isolate contained five copies of a genetic element comprised of an L2 {beta}-lactamase gene (blaL2) and a truncated ampRL2 transcriptional regulator gene, which are commonly found together in Stenotrophomonas maltophilia strains and have not been reported to mediate resistance to C/T. Comparative genomic analysis with other P. aeruginosa isolates failed to identify alternative explanations for the observed C/T resistance. We found that exogenous expression of blaL2 modestly increased C/T MICs in genetically distinct P. aeruginosa strains. A screen of our archived isolates identified two P. aeruginosa clinical isolates, PS2045 and PS2046, with one and two copies, respectively, of the genetic element containing blaL2 and truncated ampRL2. Interestingly, disruption of the gene blaL2 but not the truncated ampRL2 in PS2045 led to a significant decrease in C/T MIC. Thus, we report a novel mechanism of C/T resistance in P. aeruginosa mediated by an L2 {beta}-lactamase independently of its canonical regulator AmpRL2.

APC148 is a novel metallo-beta-lactamase inhibitor with broad activity against Ambler class B enzymes including NDM, VIM and IMP. It is being developed for patients with serious infections caused by multidrug-resistant Gram-negative bacteria. APC148 is combined with the broad-spectrum beta-lactam antibiotic meropenem and the serine-beta-lactamase inhibitor avibactam, which targets Ambler class A, C, and some class D (OXA-48-like) enzymes. In combination with meropenem and avibactam, APC148 demonstrated superior in vitro activity against a global, multidrug resistant collection of Enterobacterales, showing its promising activity against beta-lactamase producing pathogens. In this randomized, placebo-controlled, first-in-human study, the safety, tolerability and pharmacokinetics of APC148 were evaluated in healthy adults. Single doses ranging from 50 mg to 760 mg APC148 were administered intravenously over 3 h to 46 participants across six dose groups. APC148 was well tolerated at all dose levels. All adverse events were of mild intensity, and no serious adverse events or adverse events leading to study- or treatment discontinuation occurred. The pharmacokinetics of APC148 were dose-proportional with low plasma clearance, low to moderate volume of distribution and a mean plasma half-life of 2.6 h. APC148 is well tolerated in humans at therapeutically relevant doses and represents a promising candidate in the fight against antibiotic-resistant bacteria. (This study has been registered at ClinicalTrials.gov under registration number NCT06360640).

Toxoplasmosis remains a world-wide public health concern, especially for the immunocompromised. Although this population segment is increasing due to therapeutic interventions, organ transplants and infections including HIV, treatment relies almost exclusively on sulfadoxine and pyrimethamine, antifolates developed against malaria but with only moderate efficacy against acute toxoplasmosis and no effect on the chronic stage. Here we explore whether 7-substituted analogues of 7-deazaadenosine (tubercidin) that have shown remarkable efficacy against other protozoan pathogens, might also show anti-toxoplasmic activity. Tubercidin and a series of eleven 7-substituted analogues including 2-deoxy and 3-deoxyribofuranoses was tested against intracellular Toxoplasma gondii tachyzoites. The test compounds yielded EC50 values between 0.012 and 1.72 {micro}M, well below those of the control drug sulfadiazine (11.9 {micro}M) and the previously identified purine analogue adenosine arabinoside (Ara-A; 11.4 {micro}M). The tubercidin analogues displayed at most moderate toxicity to HFF cells, with the most efficacious compound, 7-(3,4-di-Cl-phenyl)-3-deoxytubercidin (FH8513) reaching a selectivity index of >2500. These nucleosides are most likely taken up by T. gondii through one of the four Equilibrative Nucleoside Transporters (ENTs) encoded by the parasites. However, deletion of TgENT2 and/or TgENT3 had no effect on the EC50 values, and deletion of TgAT1 actually sensitised the tachyzoites to most of the tubercidin analogues. We propose that these nucleosides are internalised through the TgENT1 uridine transporter and that the sensitisation in {Delta}TgAT1 cells is the result of reduced uptake of adenosine that competes with the tubercidin analogues for metabolic enzymes such as adenosine kinase.

Artemisinin-based combination therapies (ACTs) remain the cornerstone of malaria treatment, but emerging resistance threatens their efficacy. The potential for the development of drug resistance against plasmepsin X (PMX)-selective inhibitors and dual plasmepsin IX/X (PMIX/X) inhibitors was investigated in Plasmodium falciparum. A series of PMX-selective (WM4, WM76, WM92) and PMIX/X dual inhibitors (WM382, WM09, WM42) were characterised for potency against parasite growth and enzyme inhibition. In vitro selection experiments showed that all compounds had a high barrier to resistance, although parasites with reduced sensitivity to PMX-selective inhibitors could still be selected. Resistance mechanisms involved pmx gene amplification and point mutations (D245N, S315P, S359P, I363L) that alter inhibitor binding. Recombinant expression and Michaelis-Menten kinetics demonstrated that these mutations impair drug binding whilst preserving PMX catalytic function. Reverse genetics confirmed that introducing these mutations into the pmx gene resulted in decreased potency of the inhibitors. In this study, resistance to the PMIX/X dual inhibitors evaluated here could not be selected, despite prolonged selection pressure. Antimalarial Resistome Barcoding (AReBar) assays confirmed the absence of pre-existing resistance to either inhibitor class. Critically, PMIX/X dual inhibitors maintained efficacy against parasites with decreased sensitivity to PMX-selective compounds. These findings demonstrate that dual PMIX/X inhibitors present a substantially higher barrier to resistance than PMX-selective inhibitors, informing antimalarial drug development strategies and highlighting dual-target inhibition as a promising approach to mitigate resistance risks.

Despite multiple treatment strategies and extensive research on resistance mechanisms, tuberculosis (TB) remains a major global health threat, largely because of the rise of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB. Among various mechanisms complicating the situation, active antibiotic export via efflux pumps is particularly significant, yet largely unexplored. Mycobacterium sp. encodes numerous transporters, many of which are overexpressed in clinical isolates or under drug stress. Here, we examined the possible role of Rv0783c, a putative transporter that is reportedly overexpressed in drug-stressed conditions. Rv0783c conferred resistance to multiple structurally diverse antibiotics, fluoroquinolones and anti-TB drugs in the heterologous hosts, namely, Escherichia coli and Mycobacterium smegmatis. Reduced drug accumulation and active efflux of ethidium bromide (EtBr) confirmed its transport activity, which in turn gets nullified upon using the proton-motive force blocker, CCCP. On the other hand, its expression enhanced biofilm formation, linking antibiotic resistance to persistence-associated phenotype. Furthermore, site-directed mutagenesis confirmed the presence of crucial interacting residues with antibiotics that were identified by in silico analysis. Overall, we demonstrate the role of Rv0783c in the extrusion of first and second-line anti-TB drugs and enhancing biofilm formation.

The lack of a reliable chronic murine model limits drugs evaluation against Mycobacterium abscessus. Models show discrepancies, especially regarding host factors (mouse strain, sex and age). Using beads-model, we compared BALB/cJRJ and C57BL/6NCrl across sexes and ages. BALB/cJRJ showed more sustained infection and lower variability, with no significant sex- or age-related differences. Considering these results and the higher prevalence of NTM pulmonary infections in female patients, 5-6 weeks-old female BALB/cJRJ are appropriate for M. abscessus beads-model.

Aminoglycoside drugs, amikacin, streptomycin, and amikacin liposome inhalation suspension are crucial for treating refractory Mycobacterium avium-intracellulare complex pulmonary disease. In Mycobacterium tuberculosis, cross-resistance occurs between amikacin and kanamycin, but not between amikacin and streptomycin in genetic drug susceptibility testing. However, the occurrence of cross-resistance among aminoglycosides remains unclear in M. avium-intracellulare complex. We aimed to evaluate cross-resistance among aminoglycosides to determine whether streptomycin or kanamycin remains effective after the development of amikacin resistance. This single-center retrospective study included 20 patients with amikacin-resistant M. avium-intracellulare complex harboring rrs mutations. Paired analyses of streptomycin and kanamycin minimum inhibitory concentration values before and after amikacin resistance development were performed. In addition, streptomycin- and kanamycin-resistant strains were generated in vitro and resistance-associated mutations were identified using whole-genome sequencing. No significant increase was observed in streptomycin minimum inhibitory concentration values following amikacin resistance. In contrast, kanamycin values uniformly increased to >256 g/mL after the acquisition of amikacin resistance. Furthermore, amikacin- and kanamycin-resistant isolates shared mutations at position 1408 in the rrs gene, whereas streptomycin-resistant isolates exhibited mutations at position 20 in the rrs gene. These results suggest that amikacin and kanamycin exhibit cross-resistance in M. avium-intracellulare complex, whereas amikacin and streptomycin may not. Two cases in our cohort in which streptomycin treatment was effective after the acquisition of amikacin resistance further support these findings. In conclusion, streptomycin may be a potential therapeutic alternative for amikacin-resistant M. avium-intracellulare complex pulmonary disease. Future studies correlating streptomycin minimum inhibitory concentration values with clinical outcomes are required.

WHO recommends bedaquiline-pretomanid-linezolid- (BPaL) and BPaL-moxifloxacin (BPaLM) for treatment of rifampicin-resistant tuberculosis, informed by the TB-PRACTECAL results. However, clinical explanatory data of these drugs exposure and Mycobacterium tuberculosis clearance rates and toxicity relationships remain understudied. We therefore investigated the relationship between the patients exposure to anti-TB drugs in TB-PRACTECAL trial investigational regimens and their treatment outcomes. PRACTECAL-PKPD was a prospective pharmacokinetics and pharmacodynamics study nested in TB-PRACTECAL. Patients with rifampicin-resistant pulmonary tuberculosis were enrolled from Belarus and South Africa. The first objective was to develop drug exposure metrics for bedaquiline, pretomanid, linezolid, moxifloxacin and clofazimine. The efficacy objectives were to establish an exposure-response model for each drug and regimen to both bactericidal activity and long-term treatment outcomes. The safety objective was to investigate the exposure-toxicity relationship of each drug. Antimicrobial exposure did not correlate with the speed of sputum bacterial clearance, however there was a 20% increased bacillary killing rate with BPaLM compared to the standard of care arm whilst BPaL and BPaL-clofazimine (BPaLC) displayed a 15% decreased bacillary killing rate compared to the standard of care arm. Linezolid plasma exposure was higher amongst patients with anaemia or neutropenia compared to those without. No other exposure-toxicity relationships were identified for all other drugs. Absence of correlation between drug exposure and bacillary clearance suggest that the dosages used achieve saturation of bacillary killing, while remaining safe.

Mycobacterium abscessus is a rapidly growing non-tuberculous mycobacterium with rising global incidence. This pathogen exhibits intrinsic resistance to most antibiotics, presenting a major public health threat. Ethionamide (ETH) requires bioactivation by monooxygenase EthA to form the active ETH-NAD adduct. We previously identified MAB_3513 (NudC) as a phosphohydrolase that confers intrinsic resistance to M. abscessus by hydrolyzing this adduct. However, deletion of nudC results in only partial susceptibility to ETH, indicating the existence of additional resistance mechanisms. This study identified MAB_0984 as the EthR regulator in M. abscessus. Deletion of ethR in a nudC knockout background ({Delta}{Delta}ethR) significantly enhanced ETH-NAD adduct accumulation, leading to hypersusceptibility to ETH. Notably, the {Delta}ethR mutant exhibited higher susceptibility than {Delta}nudC, demonstrating that EthR is a more dominant mediator of ETH resistance than NudC. Furthermore, MAB_0985 (EthA1) and MAB_0103 (EthA2) were identified as the primary EthAs in M. abscessus. Deletion of either gene alone or in combination in the {Delta}nudC reduced adduct formation and increased resistance, while the triple mutant {Delta}{Delta}ethA1{Delta}ethA2 restored wild-type resistance. Using an intergenic region-eGFP reporter system and quantitative reverse transcription-PCR, we demonstrated that EthR confers resistance by specifically suppressing ethA1 expression in M. abscessus. The Mycobacterium tuberculosis EthR inhibitor BDM31343 could boost the efficacy of ETH against M. abscessus by inhibiting EthR. Collectively, this study identified the ethR and ethA genes in M. abscessus for the first time and elucidated their role in mediating resistance to ETH. Therefore, EthR is a promising target for potentiating the efficacy of ETH against M. abscessus. Impact statementMycobacterium abscessus constitutes an escalating global health threat, primarily due to its intrinsic resistance to most antibiotics. This study identifies MAB_0984 (EthR) as a dominant resistance determinant that exerts a more profound impact on ETH susceptibility than the previously characterized NudC. We demonstrate that EthR mediates resistance by specifically repressing the expression of EthA1 (MAB_0985), one of the primary monooxygenases responsible for ETH bioactivation. The EthRMtb inhibitor BDM31343 potentiated the activity of ETH against M. abscessus through inhibition of the EthR. These findings elucidated the mechanism of ETH resistance in M. abscessus, identifying EthR as a promising target for boosting the efficacy of ETH against M. abscessus.

1.Pharmacokinetic studies in critically ill patients are often constrained by small sample sizes, limiting the strength and generalizability of conclusions drawn solely from observed data. Bayesian inference offers a powerful strategy to address this challenge by incorporating prior knowledge. In this study, we evaluated two model-based approaches for characterizing the population pharmacokinetics of ceftolozane and tazobactam in critically ill patients, comparing nonlinear mixed-effects modeling with Bayesian hierarchical analyses. The Bayesian methods incorporated literature-derived prior information. The data was collected from 13 critically ill patients receiving 3.0 g of ceftolozane combined with tazobactam (2:1) via intravenous infusion. Pharmacokinetic modeling was performed using NONMEM and Stan software with the Torsten extension. Model diagnostics and graphical analyses were conducted in RStudio with relevant packages. In the absence of prior information, a one-compartment model with a limited set of parameters describing inter-individual variability adequately characterized the pharmacokinetics of ceftolozane and tazobactam. When prior information was incorporated, a two-compartment model became feasible and yielded a characterization of parameter variability and correlations that was more consistent with published literature. The application of Bayesian inference ensured alignment with existing literature on ceftolozane and tazobactam pharmacokinetics and mitigated some systematic biases observed in the data-driven approaches. Moreover, the Bayesian approach enables direct decision-making by incorporating uncertainty into the analysis, as demonstrated by probability of target attainment analysis. Collectively, these results underscore the utility of Bayesian methods in pharmacokinetic modeling for critically ill patients, offering a robust framework for optimizing dosing strategies in data-limited settings.

Toxoplasma gondii is a protozoan parasite capable of infecting most warm-blooded animals, including humans, and can cause severe disease in immunocompromised individuals and the developing fetus. Current treatments for toxoplasmosis are effective only against the acute stage of infection and have limited or no activity against the latent bradyzoite stage found within tissue cysts. The mitochondrion of T. gondii is a validated drug target, and the clinically used drug atovaquone acts by inhibiting the mitochondrial electron transport chain (ETC) at the coenzyme Q:cytochrome c oxidoreductase (bc1 complex). In this study, we evaluate two legacy 4(1H)-quinolones: ICI 56,780 and WR 243246, previously shown to inhibit the Plasmodium falciparum bc1 complex, for their efficacy against T. gondii. Both compounds inhibit tachyzoite growth with low-nanomolar EC values and disrupt parasite mitochondrial function by blocking cytochrome c reduction and collapsing the mitochondrial membrane potential. Notably, ICI 56,780 protects mice from lethal infection with type I RH tachyzoites. Importantly, ICI 56,780 also exhibits potent activity against chronic-stage parasites, reducing cyst size and bradyzoite viability in vitro and showing low-nanomolar EC values against in vivo-derived bradyzoites. In mice chronically infected with T. gondii, treatment with ICI 56,780 significantly decreases brain cyst burden. Although these 4(1H)-quinolones display some pharmacokinetic limitations, our findings highlight their potential as promising chemotypes active against both acute and chronic stages of T. gondii and provide a framework for future medicinal chemistry efforts to improve drug-like properties while preserving or enhancing anti-bradyzoite activity.

Osteoporosis is a progressive skeletal disorder characterized by decreased bone mass and an increased risk of fracture. Current treatments are limited by adverse effects and poor long-term compliance, necessitating alternative therapeutic approaches. Tetracycline (TC) derivatives, which are traditionally used as antibiotics, have shown promise in modulating bone remodeling. In this study, the effects of TC and three TC derivatives--oxytetracycline (OC), doxycycline (DC), and minocycline (MC)--on osteoclast and osteoblast activities were investigated using in vitro human cell models and in vivo zebrafish assays. All TC derivatives inhibited osteoclast differentiation and bone resorption, as shown by reductions in the number of TRAP-positive cells, resorption pit volume, and matrix metalloproteinase (MMP)-2/MMP-9 secretion. DC demonstrated the most potent inhibitory effects across all concentrations. Low to moderate concentrations of OC, DC, and MC promoted osteoblast proliferation and mineralization, whereas high doses inhibited these processes. Confocal imaging confirmed the accumulation of TC derivatives in mineralized bone nodules. Zebrafish studies revealed dose-dependent suppression of craniofacial bone development at higher concentrations. These findings highlight the dose dependent, dual effects of TC derivatives on bone cells (osteoblasts and osteoclasts) and underscore the potential of these agents as dual-function therapies for osteoporosis.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are key components of combination antiretroviral therapy (ART) for the treatment of human immunodeficiency virus type 1 (HIV-1) infection, binding an allosteric pocket of reverse transcriptase (RT) and inhibiting viral replication. Although second-generation NNRTIs have improved potency and resistance profiles compared to first-generation NNRTIs, the continued emergence of resistant viral strains and the need for long-acting therapeutic options underscore the importance of developing next-generation compounds. Depulfavirine (VM1500A) is a potent NNRTI being developed as a long-acting formulation. Its prodrug, elsulfavirine (ESV), is approved for HIV-1 treatment in Eurasian countries as a once-daily oral regimen and has demonstrated favorable antiviral efficacy, pharmacokinetics, and tolerability in clinical studies. Here, we report the 2.4 [A] crystal structure of HIV-1 RT in complex with depulfavirine, revealing an extended binding conformation within the NNRTI pocket that reaches from the back of the binding pocket to the entrance. These interactions may shed light on mechanisms of resistance to the F227C mutation, with and without V106 substitution, and Y188L. Notably, depulfavirine maintains potent inhibition of common NNRTI-resistant RT variants, including K103N and Y181C. Combination studies of ESV with antivirals from diverse inhibitor categories demonstrated additive or near-synergistic activity with islatravir (ISL), cabotegravir (CAB), lenacapavir (LEN), and tenofovir (TDF). These findings highlight the broad resistance profile and potential of the depulfavirine combination.

BackgroundHospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP), particularly those caused by multi-drug resistant organisms (MDROs), often require newer antibiotic treatment. The efficacy and safety of newer antibiotics compared to generic antibiotics in randomized controlled trials (RCTs) have not been evaluated before. MethodsIn this systematic review, we searched RCTs in the United States National Library of Medicine (PubMed), Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, Ovid MEDLINE, Clinical Trials.gov and Google Scholar databases published between 2013 and 2025. The primary efficacy endpoint was 28-day all-cause mortality. Secondary efficacy endpoints were clinical and microbiological response. Safety endpoint was nephrotoxicity. ResultsWe identified eight eligible RCTs involving 2,881 patients (1,450 patients treated with newer antibiotics and 1,431 patients treated with generic antibiotics) with HABP/VABP. The meta-analysis did not reveal any significant differences between newer and generic antibiotics for all-cause mortality at day 28 (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.72-1.30), clinical response (RR 1.04, 95%CI 0.93-1.17), and microbiological response (RR 1.05, 95%CI 0.89-1.24). However, newer antibiotics showed significant lower occurrences of nephrotoxicity compared to colistin component (RR 0.30, 95%CI 0.11-0.79). In subgroup analysis, newer antibiotic regimens demonstrated significant improvement in microbiological eradication of carbapenem-resistant Gram-negative bacilli (RR 1.50, 95%CI 1.18-1.90). ConclusionsNewer antibiotics showed similar efficacy and safety in treating HABP/VABP compared to generic drugs. The superiority in microbiological eradication of carbapenem-resistant Gram-negative bacilli of newer antibiotics could suggest that future trials should be targeted for those patients to improve understanding of their therapeutic use and pathophysiology of these conditions. Key pointsNewer antibiotics, despite broader antimicrobial coverage, have not significantly outperformed generic comparators in terms of 28-day all-cause mortality, clinical, or microbiological response in patients with Gram-negative HABP/VABP. This may reflect limitations in current trial designs focused primarily on regulatory approval.

Klebsiella pneumoniae ST383 has emerged as a high-risk clone, characterized by carbapenem resistance and increasing detection of hypervirulence determinants. We describe a novel ST383 lineage in Lebanon, defined by the acquisition of ICEKp5, which carries the yersiniabactin locus. Three ST383 K. pneumoniae clinical isolates (LBN_CAKp91, LBN_CTKp3, LBN_CTKp11) recovered from a Lebanese medical center were subjected to whole-genome sequencing. Comparative genomic analysis included regional ST383 strains and previously characterized Lebanese isolates. The study isolates formed a tight, monophyletic cluster (3-9 SNPs) that is phylogenetically distinct from the previously reported Lebanese ST383 clone (>164 SNPs) and grouped most closely to an Egyptian ST383 strain (59-65 SNPs). All three isolates carried ICEKp5 with yersiniabactin lineage ybt14, a feature absent in the earlier Lebanese ST383 clone. The isolates were the only ST383 strains to harbor the full spectrum of hypervirulence determinants to date, including capsule regulators (rmpA, rmpA2), aerobactin (iucABCD, iutA), yersiniabactin, and the hypervirulence biomarker peg-344. All isolates carried dual carbapenemases (blaOXA-48 and blaNDM-5) in addition to blaCTX-M-15 and blaCTX-M-14b. The genetic environments of blaOXA-48 and blaNDM-5 were highly conserved across geographically diverse ST383 isolates, indicating common plasmid origins. This study documents the emergence of a novel hypervirulent extensively drug-resistant (XDR) ST383 K. pneumoniae lineage in Lebanon. The acquisition of ICEKp5, combined with plasmid-borne hypervirulence and resistance determinants, reveals the concerning convergence of hypervirulence and XDR. Enhanced surveillance and infection control measures are urgently needed to monitor this emerging high-risk clone.