Pentadecapeptide

A method of treating an immunologically supressed or deficient individual which comprises treating said individual with an immunopotentiating amount of a pharmaceutical composition consisting of a penta-decapeptide and salts thereof containing the following amino acids:

• arginine (1 mole), glutamic acid* (1 mole), lanthionine (1 mole), .beta.-methyllanthionine (2 moles), D-phenylalanine (3 moles), glycine (2 moles), proline (1 mole), valine (1 mole), aspartic acid* (1 mole), .beta.-hydroxyaspartic acid* (1 mole), and lysinoalanine (1 mole), the asterisks indicating that either two of these amino acids or one of them and the carboxy terminal amino acid are present as amides, the hydrochloride salt thereof being characterized by the following parameters:
• (a) Melting point:
• 257.degree.-259.degree. C. (dec.);
• (b) Specific rotation:
• [.alpha]sub.D.sup.25 =-72.degree. (C=1.0, 0.1N HCl);
• (c) Ultraviolet absorption spectrum;
• Maxima at 251.5 nm-(E.sub.1 cm.sup.1% =2.68), 257 nm(E.sub.1 cm.sup.1% =2.90) and 263 nm-.) and a shoulder at 266 nm in water;
• (d) Infrared absorption spectrum as shown in FIG. 2.
• (e) Solubility in solvents:
• Soluble in water or methanol;
• hardly soluble in ethyl acetate;
• and insoluble in hexane;
• (f) Color reaction:
• Positive to Sakaguchi and Reidon-Smith reactions, and negative to Pauly reaction;
• (g) Thin layer chromatography on silica gel F.sub.254 (Merck) in benzene/ethanol/25% aqueous ammonia (2:4:1, v/v/v):
• RF=0.4 in admixture with a pharmaceutical diluent or carrier.