Abstract: Immunoregulatory 2,5-diketopiperazine compounds of formula: ##STR1## wherein m is 1 or 2 and n is 3 or 4 possess the ability to regulate the immune system of humans and animals. Administration of the compounds will return to a normal state an immune system in need of regulation.

Abstract: There are disclosed peptides having the following formula:12 A-X-Z-Y-Bwherein A is ##STR1## 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 ##STR2## Y is GLY, SER, THR, LEU, ILE, VAl, or SAR; B is TYR-R', D-TYR-R', decarboxy-TYR, or ##STR3## 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; and R and R' are substituents which do not substantially affect the biological activity of the peptides, provided that R-ARG-LYS-ASP-VAL-TYR-R' is excluded. These peptides have the capability of inducing the differentiation of T-lymphocytes but not of complement receptor (CR.sup.+) B-lymphocytes and thus are useful in a number of therapeutic areas.

Abstract: A method for solution synthesis of H-SAR-LYS-SAR-GLN-NH.sub.2 in good yield and compositions useful therein are disclosed.

Abstract: Peptides of the following formula:A-Bwherein A is a member selected from the group consisting of deamino-GLN, GLN, and (SAR).sub.n -GLN; n is an integer from 1 to 4; and B is a member selected from the group consisting of LYS-OH, LYS-NH.sub.2, decarboxy-LYS, ##STR1## LYS-SAR-OH and LYS-SAR-NH.sub.2, have significantly increased ubiquitin-like activity. Also provided are therapeutic compositions and methods for use thereof.

Abstract: There are disclosed new biological active polypeptides:A--X--Bwherein A is deamino-LYS or LYS; X is a suitable neutral aliphatic amino acid residue; e.g., one selected from the group consisting of SER, ALA, 2-Me-ALA, GLY, LEU, THR, D-SER, D-ALA, D-THR, allo-THR, D-LEU, and SAR; B is GLN-R', decarboxy-GLN, or ##STR1## and R' is a substituent which does not substantially affect the biological activity of the tripeptide.These polypeptides have the capability of inducing the differentiation of T-lymphocytes as measured by the acquisition of the thymic differentiation antigen Th-1, as well as B-lymphocytes as measured by the acquisition of the differentiation antigen Bu-1. The polypeptides are thus useful in thymic function and immunity areas such as in treatment for congenital absence of thymus. Also provided are therapeutic compositions and methods for use of the polypeptides.

Abstract: A series of (substituted)ureidoacetohydroxamic acids are useful as inhibitors of Angiotensin I converting enzyme.