Considering that A. baumannii easily acquires resistance, making CRAB a WHO priority one pathogen for antibiotic development, the results of D22 are highly promising. It displays equipotent in vitro activity with colistin against clinical CRAB isolates, while colistin exhibits severe side effects. D22 did, however, not show toxic effects tested in vitro with HepG2 cells (Table ) and in vivo using the highly sensitive zebrafish larvae model up to 500 µg/mL (Figure S 45), which emphasises the potential for application and encourages further development towards proof of concept in humans.