Abstract: Non-hemolytic cytolytic agents selected from peptides, complexes of bundled peptides, mixtures of peptides or random peptide copolymers have a selected cytolytic activity manifested in that they have a cytolytic activity on pathogenic cells, being cells which are non-naturally occurring with the body consisting of microbial pathogenic organisms and malignant cells; and are non-hemolytic, having no cytolytic effect on red blood cells. The peptides may be cyclic derivatives of natural peptides such as pardaxin and mellitin and fragments thereof in which L-amino acid residues are replaced by corresponding D-amino acid residues, or are diastereomers of linear peptides composed of varying ratios of at least positively charged amino acid and at least one hydrophobic amino acid, and in which at one of the amino acid residues is a D-amino acid.

Abstract: The invention provides diastereomeric peptides with a net positive charge greater than +1, and cyclic analogues thereof, having at least 15 amino acid residues, wherein said residues are selected from: (i) leucine and lysine;, (ii) leucine, lysine and arginine; (iii) glycine, serine, spargine, threonine, or glutamine optionally present at the N-terminus; (iv) and/or lysine, arginine, glycine, or serine optionally present at the C-terminus. The diastereomeric peptides are suitable for treatment of cancer and for treatment, particularly topical treatment, of infections caused by pathogenic organisms such as bacteria and fungi. In addition, they may be used for controlling, mycoplasma infection in cell cultures and for food preservation as food supplements and as alternative to antibiotics for animal nutrition.

Abstract: Peptides which have a net positive charge and none or only a partial a-helix configuration were found to have a non-hemolytic selective cytolytic activity. The peptides may be derived from natural peptides such as pardaxin and mellitin and fragments thereof in which L-amino acid residues are replaced by corresponding D-amino acid residues, and cyclic derivatives of the foregoing, or are diastereomers of linear peptides composed of varying ratios of at least one positively charged amino acid and at least one hydrophobic amino acid, and in which at least one of the amino acid residues is a D-amino acid, and preferably at least one third of the sequence is composed of D-amino acid residues. Pharmaceutical compositions comprising the non-hemolytic cytolytic peptides can be used for the treatment of several diseases caused by pathogens including antibacterial, fungal, viral, mycoplasma and protozoan infections and for the treatment of cancer.