PRF-119

PRF-119 is a recombinant chimeric bacteriophage endolysin (chimeolysin) designed as an antibacterial agent targeting *Staphylococcus aureus*, including methicillin-resistant *S. aureus* (MRSA). It is composed of an enzymatic active domain (EAD) containing a cysteine- and histidine-dependent aminopeptidase/hydrolase (CHAP) domain from the endolysin of phage K, fused to a cell wall-binding domain (CBD) from lysostaphin. PRF-119 was originally developed by Hyglos (which was later succeeded by HYpharm). It serves as the precursor/progenitor to HY-133, which features a shortened linker peptide for improved stability. PRF-119 has demonstrated potent, rapid bactericidal activity in vitro against clinical isolates of *S. aureus* without affecting coagulase-negative staphylococci or other normal microbiota.