The Novel Oxazolidinone TBI-223 Is Effective in Three Preclinical Mouse Models of Methicillin-Resistant Staphylococcus aureus Infection

Discovery and Optimization of Novel SaFabI Inhibitors as Specific Therapeutic Agents for MRSA Infection

As the rate-limiting enzyme in fatty acid biosynthesis, Staphylococcus aureus enoyl-acyl carrier protein reductase (SaFabI) emerges as a compelling target for combating methicillin-resistant S. aureus (MRSA) infections. Herein, compound 1, featuring a 4-(1H-benzo[d]imidazol-2-yl)pyrrolidin-2-one scaffold, was identified as a potent SaFabI inhibitor (IC50 = 976.8 nM) from an in-house library. Subsequent optimization yielded compound n31, with improved inhibitory efficacy on enzymatic activity (IC50 = 174.2 nM) and selective potency against S. aureus (MIC = 1-2 μg/mL). Mechanistically, n31 directly inhibited SaFabI in cellular contexts. Moreover, n31 exhibited favorable safety and pharmacokinetic profiles, and dose-dependently treated MRSA-induced skin infections, outperforming the approved drug, linezolid. The chiral separation of n31 resulted in (S)-n31, with superior activities (IC50 = 94.0 nM, MIC = 0.25-1 μg/mL) and in vivo therapeutic efficacy. In brief, our research proposes (S)-n31 as a promising candidate for SaFabI-targeted therapy, offering specific anti-S. aureus efficacy and potential for further development.

New Oxazolidinones for Tuberculosis: Are Novel Treatments on the Horizon?

Multidrug-resistant tuberculosis (MDR-TB) is a global health concern. Standard treatment involves the use of linezolid, a repurposed oxazolidinone. It is associated with severe adverse effects, including myelosuppression and mitochondrial toxicity. As such, it is imperative to identify novel alternatives that are better tolerated but equally or more effective. Therefore, this review aims to identify and explore the novel alternative oxazolidinones to potentially replace linezolid in the management of TB. The keywords tuberculosis and oxazolidinones were searched in PubMed to identify eligible compounds. The individual drug compounds were then searched with the term tuberculosis to identify the relevant in vitro, in vivo and clinical studies. The search identified sutezolid, tedizolid, delpazolid, eperezolid, radezolid, contezolid, posizolid and TBI-223, in addition to linezolid. An additional search resulted in 32 preclinical and 21 clinical studies. All novel oxazolidinones except posizolid and eperezolid resulted in positive preclinical outcomes. Sutezolid and delpazolid completed early phase 2 clinical studies with better safety and equal or superior efficacy. Linezolid is expected to continue as the mainstay therapy, with renewed interest in drug monitoring. Sutezolid, tedizolid, delpazolid and TBI-223 displayed promising preliminary results. Further clinical studies would be required to assess the safety profiles and optimize the dosing regimens.

Recent advances in the exploration of oxazolidinone scaffolds from compound development to antibacterial agents and other bioactivities

Bacterial infections cause a variety of life-threatening diseases, and the continuous evolution of drug-resistant bacteria poses an increasing threat to current antimicrobial regimens. Gram-positive bacteria (GPB) have a wide range of genetic capabilities that allow them to adapt to and develop resistance to practically all existing antibiotics. Oxazolidinones, a class of potent bacterial protein synthesis inhibitors with a unique mechanism of action involving inhibition of bacterial ribosomal translation, has emerged as the antibiotics of choice for the treatment of drug-resistant GPB infections. In this review, we discussed the oxazolidinone antibiotics that are currently on the market and in clinical development, as well as an updated synopsis of current advances on their analogues, with an emphasis on innovative strategies for structural optimization of linezolid, structure-activity relationship (SAR), and safety properties. We also discussed recent efforts aimed at extending the activity of oxazolidinones to gram-negative bacteria (GNB), antitumor, and coagulation factor Xa. Oxazolidinone antibiotics can accumulate in GNB by a conjugation to siderophore-mediated β-lactamase-triggered release, making them effective against GNB.

Antibiotics in the clinical pipeline as of December 2022

The need for new antibacterial drugs to treat the increasing global prevalence of drug-resistant bacterial infections has clearly attracted global attention, with a range of existing and upcoming funding, policy, and legislative initiatives designed to revive antibacterial R&D. It is essential to assess whether these programs are having any real-world impact and this review continues our systematic analyses that began in 2011. Direct-acting antibacterials (47), non-traditional small molecule antibacterials (5), and β-lactam/β-lactamase inhibitor combinations (10) under clinical development as of December 2022 are described, as are the three antibacterial drugs launched since 2020. Encouragingly, the increased number of early-stage clinical candidates observed in the 2019 review increased in 2022, although the number of first-time drug approvals from 2020 to 2022 was disappointingly low. It will be critical to monitor how many Phase-I and -II candidates move into Phase-III and beyond in the next few years. There was also an enhanced presence of novel antibacterial pharmacophores in early-stage trials, and at least 18 of the 26 phase-I candidates were targeted to treat Gram-negative bacteria infections. Despite the promising early-stage antibacterial pipeline, it is essential to maintain funding for antibacterial R&D and to ensure that plans to address late-stage pipeline issues succeed.

γδ T cell-intrinsic IL-1R promotes survival during Staphylococcus aureus bacteremia

Staphylococcus aureus is a leading cause of bacteremia, further complicated by the emergence of antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA). A better understanding of host defense mechanisms is needed for the development of host-directed therapies as an alternative approach to antibiotics. The levels of IL-1, IL-17, and TNF-α cytokines in circulation have been associated with predictive outcomes in patients with S. aureus bacteremia. However, their causative role in survival and the cell types involved in these responses during bacteremia is not entirely clear. Using a mouse model of S. aureus bacteremia, we demonstrated that IL-17A/F and TNF-α had no significant impact on survival, whereas IL-1R signaling was critical for survival during S. aureus bacteremia. Furthermore, we identified that T cells, but not neutrophils, monocytes/macrophages, or endothelial cells were the crucial cell type for IL-1R-mediated survival against S. aureus bacteremia. Finally, we determined that the expression of IL-1R on γδ T cell, but not CD4+ or CD8+ T cells was responsible for survival against the S. aureus bacteremia. Taken together, we uncovered a role for IL-1R, but not IL-17A/F and TNF-α in protection against S. aureus bacteremia. Importantly, γδ T cell-intrinsic expression of IL-1R was crucial for survival, but not on other immune cells or endothelial cells. These findings reveal potential cellular and immunological targets for host-directed therapies for improved outcomes against S. aureus bacteremia.

Study on skin infection model of Staphylococcus aureus based on analytic hierarchy process and Delphi method

Purpose

Infectious skin diseases are a type of inflammatory skin lesions caused by pathogenic microorganisms. Because of the uncertainty of methodology, the skin infection model usually have low replication rate and lack of good evaluation system. We aimed to establish multi-index and comprehensive evaluation method for Staphylococcus aureus (S.aureus) skin-infection models through Analytic hierarchy process (AHP) and Delphi method, and screen high quality animal models through it.

Materials and methods

Firstly, the evaluation indicators of skin infection were collected basing on literature research. The weight of the evaluation indicators were decided according to AHP and Delphi method. Then different ulcer models (mouse or rat) infected by S. aureus were selected as the research objects.

Results

The evaluation indicators were classified into four groups of criteria (including ten sub-indicators) and given different weights, physical sign changes (0.0518), skin lesion appearance (0.2934), morphological observation (0.3184), etiological examination (0.3364). Through the evaluation system, we screened and found that the mouse ulcer model which caused by a round wound and 1.0 × 10¹⁰ CFU/mL (0.1 mL) bacterial concentration got the highest comprehensive score, and also found that the model which caused by a 1.5 cm-round wound and 1.0 × 10¹⁰ CFU/mL (0.2 mL) maybe the best rat ulcer model.

Conclusions

This study has established an evaluation system based on AHP and Delphi method, also provided the best skin ulcer models selected by this system, the models are suitable for disease research and drug development research of skin ulcer.

Next-Generation Diarylquinolines Improve Sterilizing Activity of Regimens with Pretomanid and the Novel Oxazolidinone TBI-223 in a Mouse Tuberculosis Model

A regimen comprised of bedaquiline (BDQ, or B), pretomanid, and linezolid (BPaL) is the first oral 6-month regimen approved by the U.S. Food and Drug Administration and recommended by the World Health Organization for the treatment of extensively drug-resistant tuberculosis. We used a well-established BALB/c mouse model of tuberculosis to evaluate the treatment-shortening potential of replacing bedaquiline with either of two new, more potent diarylquinolines, TBAJ-587 and TBAJ-876, in early clinical trials. We also evaluated the effect of replacing linezolid with a new oxazolidinone, TBI-223, exhibiting a larger safety margin with respect to mitochondrial toxicity in preclinical studies. Replacing bedaquiline with TBAJ-587 at the same 25-mg/kg dose significantly reduced the proportion of mice relapsing after 2 months of treatment, while replacing linezolid with TBI-223 at the same 100-mg/kg dose did not significantly change the proportion of mice relapsing. Replacing linezolid or TBI-223 with sutezolid in combination with TBAJ-587 and pretomanid significantly reduced the proportion of mice relapsing. In combination with pretomanid and TBI-223, TBAJ-876 at 6.25 mg/kg was equipotent to TBAJ-587 at 25 mg/kg. We conclude that replacement of bedaquiline with these more efficacious and potentially safer diarylquinolines and replacement of linezolid with potentially safer and at least as efficacious oxazolidinones in the clinically successful BPaL regimen may lead to superior regimens capable of treating both drug-susceptible and drug-resistant TB more effectively and safely.

Oxazolidinone: A promising scaffold for the development of antibacterial drugs

Due to the long-term and widespread use of antibiotics in clinic, the problem of bacterial resistance is increasingly serious, and the development of new drugs to treat drug-resistant bacteria has gradually become the mainstream direction of antibiotic research. The oxazolidinone-containing drugs linezolid, tedizolid phosphate and contezolid have been approved to the market, which are effective against a variety of Gram-positive bacterium infections. Moreover, there are also many antibiotics containing oxazolidinone fragment under clinical investigation that show good pharmacokinetic and pharmacodynamic properties with unique mechanism of action against resistant bacteria. In this review, we summarized the oxazolidinone-based antibiotics already on the market or in clinical trials and the representative bioactive molecules, and mainly focused on their structural optimizations, development strategies and structure-activity relationships in hope of insight into the reasonable design for medical chemists to develop new oxazolidinone antibiotics with highly potency and fewer side effects.

Inhibition of planktonic growth and biofilm formation of Staphylococcus aureus by entrectinib through disrupting the cell membrane

Over the last few decades, Staphylococcus aureus infection remain a major medical challenge and health concern worldwide. Biofilm formation and antibiotic resistance caused by S. aureus make it difficult to be eradicated from bacterial infections in clinics. In this study, our data demonstrated the antibacterial and excellent anti-biofilm activity of entrectinib against S. aureus. Entrectinib also exhibited the good safety, suggesting no toxicity with antibacterial concentration of entrectinib toward the erythrocytes and mammalian 239 T cells. Moreover, entrectinib significantly reduced the bacterial burden of septic tissue in a murine model of MRSA infection. Global proteomic analysis of S. aureus treated with entrectinib showed significant changes in the expression levels of ribosomal structure-related (rpmC, rpmD, rplX, and rpsT) and oxidative stress-related proteins (Thioredoxin system), suggesting the possible inhibition of bacterial protein biosynthesis with entrectinib exposure. The increased production of reactive oxygen species (ROS) was demonstrated in the entrectinib-treated S. aureus, supported the impact of entrectinib on the expression changes of ROS-correlated proteins involved in oxidative stress. Furthermore, entrectinib-induced resistant S. aureus clone was selected by in vitro induction under entrectinib exposure and 3 amino acid mutations in the entrectinib-induced resistant S. aureus strain, 2 of which were located in the gene encoding Type II NADH: quinoneoxidoreductase and one were found in GTP pyrophosphokinase family protein. Finally, the bactericidal action of entrectinib on S. aureus were confirmed by disrupting the bacterial cell membrane. Conclusively, entrectinib exhibit the antibacterial and anti-biofilm activity by destroying cell membrane against S. aureus.