The invention relates to modified antibiotic peptides, in particular derivatives of apidaecin and oncocin, preferably having increased stability, reduced immunoreaction, and improved pharmacokinetics. In the invention, the peptide antibiotics are reversibly protected by means of a linker having the polymer polyethylene glycol (PEG). The peptide linker contains a recognition sequence for trypsin-like serum proteases. In the apidaecin derivatives, the linker and the PEG are bonded to a side chain. In the serum, the linker is cut by serum proteases and PEG is separated off. The released peptide still contains remnants of the linker, which are still bonded to the amino group in the side chain. Astonishingly, said remaining remnants of the linker impair the activity of the antimicrobial peptide only a little or not at all.
