Cyclic peptides with pharmacological activity

The claimed monocyclic and bicyclic oligopeptides in free or salt forms contain 5-6 natural or non-natural amino acid residues (or their guanidinylated or aminated versions), of which at least 1 is hydrophobic and 2 are basic. The 15 claimed compdounds were synthesized by solid-phase techniques followed by cyclization reactions. The peptides even at low concentrations. had antineoplastic activities, especially against highly invasive and metastatic tumors, as tested in vitro against animal and human tumor cell lines.