Semisynthetic pleuromutilin antimicrobials with therapeutic potential against methicillin-resistant Staphylococcus aureus by targeting 50S ribosomal subunit

Synthesis and evaluation of novel pleuromutilin derivatives targeting the 50S ribosomal subunit for antibacterial ability

Multidrug-resistant bacteria, particularly methicillin-resistant Staphylococcus aureus, have become a major global public health concern. Therefore, developing new antibiotics that do not possess cross-resistance for the currently available antibiotics is critical. Herein, we synthesized a novel class of pleuromutilin derivatives containing substituted triazine with improved antibacterial activity. Among these derivatives, 6d, which contains 4-dimethylamino-1,3,5-triazine in the side chain of pleuromutilin, exhibited highly promising antimicrobial activity and mitigated antibiotic resistance. The high antibacterial potency of 6d was further supported by docking model analysis and green fluorescent protein inhibition assay. Additionally, cytotoxicity and acute oral toxicity evaluation and in vivo mouse systemic infection experiments revealed that 6d possessed tolerable toxicity and promising therapeutic efficacy.

Design, synthesis, and evaluation of novel pleuromutilin aryl acrylate derivatives as promising broad-spectrum antibiotics especially for combatting multi-drug resistant gram-negative bacteria

The emergence of drug-resistant strains presents a grave challenge for traditional antibiotics, underscoring the exigency of exploring novel antibacterial drugs. To address this, the present study endeavors to design and synthesize a collection of pleuromutilin aromatic acrylate derivatives, guided by combination principles. The antibacterial activity and structure-activity relationship of these derivatives were evaluated, and most of the derivatives displayed moderate to excellent antibacterial activity against both Gram-positive bacteria and Gram-negative bacteria. Among these derivatives, 5g exhibited the strongest antibacterial activity, with MIC (minimum inhibitory concentration) values ranging from 1-32 μg/mL, and a MIC value against clinically isolated drug-resistant strains of 4-64 μg/mL. Additionally, 5g exhibited negligible cytotoxicity, superior anti-mycoplasma activity, and a greater propensity to perturb bacterial cell membranes. Notably, the administration of 5g resulted in an increased survival rate of MRSA (Methicillin-resistant Staphylococcus aureus)-infected mice, with an ED50 (median effective dose) value of 9.04 mg/kg. These results indicated the potential of 5g to be further developed as an antibacterial drug for the clinical treatment of drug-resistant bacterial infections.

Anti-methicillin-resistant Staphylococcus aureus activity and safety evaluation of 14-O-[(5-ethoxycarbonyl-4,6-dimethylpyrimidine-2-yl) thioacetyl] mutilin (EDT)

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have threated the public health worldwide, which emphasizes the urgent need for new drugs with novel mechanism of actions. 14-O-[(5-ethoxycarbonyl-4,6-dimethylpyrimidine-2-yl) thioacetyl] mutilin (EDT) is a pleuromutilin compound with high activity against several Gram-positive bacteria in vitro and in vivo. This study aimed to verifying the potential anti-MRSA activity and evaluating the safety of EDT. In in vitro antibacterial activity assays, EDT exhibited potent antibacterial activity against MRSA isolated from clinic (minimum inhibitory concentration = 0.0313-0.125 μg/mL), increased post-antibiotic effect (PAE) values and limited potential for the development of resistance. Docking model and green fluorescent protein (GFP) inhibition assay further elucidated the higher antibacterial activities of EDT via mechanism of action. In safety evaluation, EDT exhibited low cytotoxic effect and acute oral toxicity in mice and avoided to significantly increase the number of revertant colonies of six tested strains in the Ames study. Furthermore, EDT displayed a moderate inhibitory effect on CYP3A4 and moderate stability in mouse and human liver microsomes, providing a promising agent for the development of new antimicrobial candidate.

Discovery of urea-based pleuromutilin derivatives as potent gram-positive antibacterial agents

There is an urgent need to discover new antibacterial drugs and provide new treatment options for clinical antimicrobial resistance (AMR) pathogen infections. Inspired by the structural insights from analyzing the co-crystal structure of lefamulin with the ribosomes of S. aureus, a series of novel pleuromutilin derivatives of phenylene sulfide incorporated with urea moiety were designed and synthesized. The structure-activity relationship (SAR) study revealed that derivatives with urea in the meta position of phenylene sulfide had optimal antibacterial activities in vitro. Among them, 21h was the most potent one against Methicillin-resistant Staphylococcus aureus (MRSA) and clinical AMR Gram-positive bacteria with minimum inhibitory concentrations (MICs) in the range of 0.00195-0.250 μg/mL. And it possessed low resistance frequency, prolonged Post-Antibiotic Effect and the capability to overcome lefamulin-induced resistance. Furthermore, 21h exhibited potent antibacterial activity in vivo in both the thigh infection model and trauma infection model, representing a promising lead for the development of new antibiotics against Gram-positive pathogens, especially for AMR bacteria.