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 (BC-3781) is a semi-synthetic compound that inhibits the synthesis of bacterial protein, which is required for bacteria to grow.