Investigating the Antibacterial Effects of Synthetic Gamma-Lactam Heterocycles on Methicillin-Resistant Staphylococcus aureus Strains and Assessing the Safety and Effectiveness of Lead Compound MFM514

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be one of the main causes of hospital-acquired infections in all regions of the world, while linezolid is one of the only commercially available oral antibiotics available against this dangerous gram-positive pathogen. In this study, the antibacterial activity from 32 analogues of synthetic gamma-lactam heterocycles against MRSA was determined. Amongst screened analogues for the minimum inhibitory concentration (MIC) assay, compound MFM514 displayed good inhibitory activity with MIC values of 7.8–15.6 µg/mL against 30 MRSA and 12 methicillin-sensitive S. aureus (MSSA) clinical isolates, while cytotoxicity evaluations displayed a mean inhibitory concentration (IC(50)) value of > 625 µg/mL, displaying a potential to becoming as a lead compound. In subsequent animal studies for MFM514, a single-dose oral acute toxicity test revealed an estimated mean lethal dose (LD(50)) value of <5000 mg/kg, while in the mice infection test, a mean effective dose (ED(50)) value of 29.39 mg/kg was obtained via oral administration. These results suggest that gamma-lactam carbon skeleton, particularly MFM514, is highly recommended to be evaluated further as a new safe and efficacious orally delivered antibacterial agent against MRSA.