Pexiganan acetate

Pexiganan acetate (MSI 78) is a synthetic cationic peptide (22 amino acids) with antibacterial activity. It is an analogue of magainin 2, which is a host defence peptide isolated from frog skin. The drug is thought to act by disturbing the permeability of the cell membrane or cell wall. Pexiganan acetate has good in vitro activity against Gram-positive and Gram-negative aerobes; 99% of strains were susceptible to the agent using a break-point of 64 mg/L. 89 to 97% of anaerobes were susceptible to pexiganan acetate using the same break-point. After 7 passages in vitro, there was no evidence of resistance to pexiganan acetate among 2 strains of Staphylococcus aureus. In 2 phase III multicentre randomised double-blind trials in diabetic patients with infected foot ulcers, both topical pexiganan acetate 1% and oral ofloxacin 800 mg/day achieved clinical cure or improvement in about 90% of patients. Eradication of pathogens in the 2 studies was achieved in 82% of ofloxacin recipients and 66% of pexiganan acetate recipients at the end of therapy. Limited data indicate that pexiganan acetate is well tolerated.