Lefamulin acetate (BC-3781 acetate) (formally BC-3781 acetate) is a novel pleuromutilin antibiotic and is the first to be used for the systemic treatment of bacterial infections in humans. Lefamulin acetate (BC-3781 acetate) inhibits protein synthesis by binding to the peptidyl transferase center of the 50S bacterial ribosome, preventing the binding of transfer RNA for peptide transfer. Lefamulin acetate (BC-3781 acetate) is an orally active antibiotic for community-acquired bacterial pneumonia (CABP) treatment.

Lefamulin has activity against gram-negative organisms, including Haemophilus influenza (MIC50=1 μg/ml; MIC90=0.12 μg/ml) and Moraxella cotarrhali (MIC50=2 μg/ml; MIC90=0.25 μg/ml)[1].Lefamulin acetate (BC-3781 acetate) has activity against the resistant gram-postive organisms, including taphylococcus aureus (MRSA) (MIC50=0.12 μg/ml; MIC90=0.25 μg/ml); β-Hemolytic strepococcus (MIC50=0.03 μg/ml; MIC90=0.03 μg/ml); Viridans group Streptococcus (MIC50=0.12 μg/ml; MIC90=0.5 μg/ml), Enterocossus faecium (MIC50=0.12 μg/ml; MIC90=4 μg/ml), Streptococcus pneumonia (MIC50=0.12 μg/ml; MIC90 =0.25 μg/ml)[1].