Development of non-β-Lactam covalent allosteric inhibitors targeting PBP2a in Methicillin-Resistant Staphylococcus...

Area of Science:

• Medicinal Chemistry
• Microbiology
• Drug Discovery

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant public health threat due to its resistance to β-lactam antibiotics.
• MRSA's resistance is primarily mediated by penicillin-binding protein 2a (PBP2a), which has an allosteric site regulating its activity.
• Targeting this allosteric site offers a potential strategy to overcome existing resistance mechanisms.

Purpose of the Study:

• To design and synthesize novel covalent inhibitors targeting the allosteric site of MRSA PBP2a.
• To establish the structure-activity relationship of 1,3,4-oxadiazole-based compounds.
• To investigate the mechanism of action and therapeutic potential of the identified inhibitors.

Main Methods:

• Screening of 113 compounds with a 1,3,4-oxadiazole core.
• Stereoselective synthesis and optimization of lead compounds.
• In vitro antimicrobial activity testing, cytotoxicity assays, in vivo efficacy studies in a mouse model, LC-MS/MS, and in-silico analysis.

Main Results:

• Optimized sulfonyl oxadiazole compounds showed an eightfold increase in cell inhibition activity.
• Compounds formulated in PEG-based ointments exhibited low toxicity (CC50 > 78μM) and potent antimicrobial effects against MRSA (IC50 ≈ 1μM).
• Evidence supports a covalent binding mechanism via S_NAr reaction at the allosteric site, leading to active site closure.

Conclusions:

• Novel sulfonyl oxadiazole derivatives effectively inhibit MRSA by targeting the PBP2a allosteric site.
• The identified compounds demonstrate a promising therapeutic potential for treating MRSA infections.
• The study elucidates a covalent allosteric inhibition mechanism, offering new avenues for antibiotic development.