Abstract: A peptide derivative represented by the following formula or a salt thereof ##STR1## wherein A represents a hydrogen atom, and B represents a phenyl group substituted with a hydroxyl group;said derivative has an antitumor activity stronger than that of dolastatin 10, and is useful as an anticancer or antitumor agent.

Abstract: A tetrapeptide derivative represented by the following formula or a salt thereof has a higher cytostatic activity than dolastatin 10, and is useful as an antitumor agent: ##STR1## wherein, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and each represent a hydrogen atom, a lower alkyl group or an aralkyl group;Q represents ##STR2## or a group of -A.sub.2 -R.sub.7, wherein, A.sub.1 represents a direct bond or ##STR3## Y represents a hydrogen atom or --COR.sub.6, R.sub.5 represents a hydrogen atom, a lower alkyl group or an aralkyl group,R.sub.6 represents a hydroxyl group, a lower alkoxy group, an aralkyloxy group or ##STR4## wherein, R.sub.8 and R.sub.9 are the same or different and each represent a hydrogen atom, a lower alkyl group, a phenyl group or a 4- to 7-membered heterocyclic group containing one or two hetero atoms selected from S, O and N, or alternativelyR.sub.8 and R.sub.

Abstract: This invention relates to peptide derivatives of the formula ##STR1## or salts thereof, wherein: (a) Q.sub.1 represents a 1-dimethylamino-2-methylpropyl group and Q.sub.2 represents an (R)- or (S)-2-hydroxy-2-phenylethylamino group, a 2-phenylcyclopropylamino group or a 1,2,3,4-tetrahydroisoquinolin-2-yl group, or(b) Q.sub.1 represents a 1-methyl-2-pyrrolidinyl group and Q.sub.

Abstract: A peptide derivative represented by the following formula or a salt thereof ##STR1## wherein A and B each represent either of the following (a) and (b), (a) A represents a hydrogen atom, and B represents a phenyl group substituted with a halogen atom, hydroxyl group, lower alkyl group or lower alkoxy group, or a heteroaryl group,(b) A represents --CONH--R.sup.1, --CSNH--R.sup.1, a hydroxymethyl group, a lower alkoxycarbonyl group or a carboxyl group, wherein, R.sup.1 represents a lower alkyl group or a heteroaryl group, and B represents a phenyl group optionally substituted with a halogen atom, hydroxyl group, lower alkyl group or lower alkoxy group,has an antitumor activity stronger than that of dolastatin 10, and is useful as an anticancer or antitumor agent.

Abstract: A tetrapeptide derivative represented by the following formula or a salt thereof has a higher cyto-static activity than dolastatin 10, and is useful as an antitumor agent: ##STR1## wherein, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and each represent a hydrogen atom, a lower alkyl group or an aralkyl group;Q represents ##STR2## or a group of --A.sub.2 --R.sub.7, wherein,A.sub.1 represents a direct bond or ##STR3## Y represents a hydrogen atom or --COR.sub.6, R.sub.5 represents a hydrogen atom, a lower alkyl group or an aralkyl group,R.sub.6 represents a hydroxyl group, a lower alkoxy group, an aralkyloxy group or ##STR4## wherein, R.sub.8 and R.sub.9 are the same or different and each represent a hydrogen atom, a lower alkyl group, a phenyl group or a 4- to 7-membered heterocyclic group containing one or two hetero atoms selected from S, O and N, or alternatively R.sub.8 and R.sub.

Abstract: Novel immunochemical assay reagents comprising combinations of (A) a carboxyl-containing water-soluble mono-olefinic polymeric compound combined with a hapten or its chemically modified product, or a hapten-supported latex resulting from the chemical linking of the hapten-bound polymeric compound to a polymeric latex, with (B) a hapten antibody, or a hapten antibody-supported carrier; and a method for immunochemically determining haptens by using the aforesaid reagent. This reagent is very stable and can be stored for an extended period of time without degradation. It enables transition from an agglutination inhibited pattern to an agglutinated pattern to be discerned clearly and rapidly with high sensitivity.