A review in Antimicrobial Agents and Chemotherapy found that the antibiotic development pipeline has comparatively few clinically differentiated products in late-stage clinical development, particularly against critical, multidrug-resistant pathogens.

Researchers examined all conventional and nonconventional antibacterial drug candidates that were being evaluated in clinical trials as of June 30, 2021. They tallied 76 products, of which 45 are conventional antibacterial agents and 31 nonconventional. Sixty of those candidates (79%) are in Phase 1 or Phase II trials (28 and 32, respectively), while 12 are in Phase III trials and 4 are under regulatory review.

Of the 76 candidates, 42 are being developed to address pathogens regarded as critical (26) and high/medium priority (16) by the World Health Organization. Furthermore, 16 products are being developed to treat mycobacterial infections (14 for tuberculosis and two for nontuberculosis mycobacteria) and 15 to treat Clostridioides difficile infections.

However, only 18 of the antibacterial agents in development have new pharmacophores, which is one of the components that can determine if an antibacterial candidate belongs to a new class or subclass of antibiotics. Only 4 have new overarching modes of action. The review also revealed that 12 new antibacterial products have been approved globally since 2017, but only one (vaborbactam) belongs to a new antibiotic class.