SPR741 acetate (NAB741 acetate) is a cationic peptide derived from polymyxin B and is a potentiator molecule. SPR741 acetate increases the permeability of the outer membrane of Gram-negative bacteria and is used to treat severe Gram-negative bacteria infections. SPR741 acetate inhibits multidrug-resistant Gram-negative bacteria. The spectrum of activity of the antibiotic can be widened when used in combination with SPR741 acetate.