There are at least 53 systemic antibiotic NCEs in clinical development, of which 14 fall into innovative classes/mechanisms of action, defined as compounds that are not based on chemical classes of any antibiotics used systemically in humans. (A) Topoisomerase IIA (TOP2A) is not a new target, but GSK2140944, a TOP2A inhibitor from GlaxoSmithKline plc (LSE:GSK; NYSE:GSK), was included because it is not based on an already approved antibiotic chemical class. Source: BCIQ: BioCentury Online Intelligence; company documents; www.clinicaltrials.gov