ABI-0043

ABI-0043 is a novel small molecule antibiotic belonging to the benzoxazinorifamycin class, a derivative of the rifamycin family. It functions as a potent bactericidal agent by specifically inhibiting bacterial DNA-dependent RNA polymerase, which prevents the transcription of DNA into RNA and subsequent protein synthesis. Developed by Advancis Pharmaceutical (which later became MiddleBrook Pharmaceuticals), ABI-0043 was primarily investigated for its activity against Gram-positive bacteria, including methicillin-resistant *Staphylococcus aureus* (MRSA) and penicillin-resistant *Streptococcus pneumoniae*. Preclinical studies in the mid-2000s demonstrated that ABI-0043 had in vivo efficacy comparable to ceftriaxone in murine pneumonia models. However, development of the compound appears to have been discontinued as the company shifted its focus toward its Pulsys delivery technology before eventually liquidating.