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 . 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 .