Peptides having thymopoietin-like activity

A peptide having the biological capability of inducing the differentiation of T-lymphocytes but not of complement receptor (CR.sup.+) B lymphocytes, said peptide having the following sequence:

• A-X-Z-Y-B
• and the pharmaceutically acceptable salts thereof, wherein A is ##STR18## X is a suitable neutral, aliphatic or aromatic amino acid residue;
• e.g., one selected from the group consisting of ALA, 2-Me-ALA, GLY, LEU, ILE, LYS, THR, SER, PHE, MET, D-ALA, D-LEU, D-ILE, D-LYS, D-THR, allo-THR, D-SER, D-PHE, D-MET, and SAR;
• Z is ##STR19## Y is GLY, SER, THR, LEU, ILE, VAL, or SAR;
• B is TYR-R', D-TYR-R', decarboxy-TYR, or ##STR20## m is 3 or 4;
• n is 1, 2, or 3;
• R''' is hydrogen, C.sub.1 -C.sub.7 alkyl, C.sub.6 -C.sub.12 aryl, or C.sub.1 -C.sub.7 alkanoyl;
• R and R' are terminal groups on said peptide which do not substantially affect the biological capability thereof, said R and R' being selected from the groups consisting of:
• ______________________________________ R R' ______________________________________ Hydrogen OH C.sub.1 -C.sub.7 alkyl NH.sub.2 C.sub.6 -C.sub.12 aryl NHR" C.sub.6 -C.sub.20 alkaryl N(R").sub.2 C.sub.6 -C.sub.20 aralkyl OR" C.sub.1 -C.sub.7 alkanoyl -- C.sub.2 -C.sub.7 alkenyl VAL C.sub.2 -C.sub.7 alkynyl GLN GLN LEU GLU TYR GLY VAL--GLN GLU--GLN VAL--LEU GLY--GLN VAL--TYR GLY--GLU GLN--LEU GLY--GLU--GLN GLN--TYR GLN--VAL LEU--TYR LEU--LEU TYR--LEU VAL--GLN--LEU VAL--GLN--LEU--TYR VAL--GLN--LEU--TYR--LEU ______________________________________
• wherein R" is C.sub.1 -C.sub.7 alkyl, C.sub.2 -C.sub.7 alkenyl, C.sub.2 -C.sub.7 alkynyl, C.sub.6 -C.sub.20 aryl, C.sub.6 -C.sub.20 aralkyl, or C.sub.6 -C.sub.20 alkaryl;
• provided that R-ARG-LYS-ASP-VAL-TYR-R' is excluded.