The availability of effective antibiotics is a key factor of today’s medicine. Without antibiotics many of the modern achievements in neonatal and geriatric care, surgery and cancer therapy would be at risk. With the emergence and continuous spread of resistance among pathogens of different origin, this risk is growing rapidly. At the same time the development of novel agents with new modes of action lacking cross resistance does not follow the medical need. The reasons for this discrepancy are numerous, ranging from scientific challenges, regulatory requirements to economic and societal issues. Only very few pharmaceutical companies remain active in the field.

The complexity of antibacterial drug discovery in the 21st century will be illustrated with a journey through the chemical space of Actelion/Idorsias bacterial topoisomerase inhibitor program.