It relates to polymyxin analogues having either a short length fatty acyl unit than polymyxin or simply there is a lack of such unit, a hydrophobic chain at the 6th amino acid position of the polymixyn analogue, and in some cases a lower cationic charge than polymyxin, as well as a disulfide bond and an amide or an ester bond in the scaffold. These polymyxin analogues are selective against Gram-negative bacteria and show a particular high antibacterial activity against P. aeruginosa resistant strains, thus they are useful in the treatment of bacterial infections. It also relates to pharmaceutical compositions comprising them.
