Abstract: The present invention provides anti-tumor peptides of Formula I,A--B--NR.sup.3 --CHD--CH(OCH.sub.3)--CH.sub.2 CO--E--K (I),and the acid salts thereof. A is an amino acid residue selected from the group consisting of N-methyl-D-prolyl, N-methyl-D-homoprolyl and N,N-dimethyl-2-ethylphenylglycyl, or an amino acid residue of the formula R.sup.1 R.sup.2 N--CHX--CO, wherein R.sup.1 is a-methyl group or an ethyl group, R.sup.2 is a hydrogen atom, a methyl group or an ethyl group, and X is an alkyl group. B is an amino acid residue selected from the group consisting of valyl, isoleucyl, leucyl, and 2-t-butylglycyl. R.sup.3 is a hydrogen atom or a methyl group. D is a normal or branched C.sub.2 -C.sub.5 -alkyl group. E is an amino acid residue selected from the group consisting of prolyl, homoprolyl, 5-methylprolyl, and phenylalanyl, or E is a residue derived from an amino acid comprising a pyrrolidine group. K is an alkoxy group or an amino group.

Abstract: The present invention provides anti-tumor peptides of Formula I,A-B-N (CH.sub.3)-CHD-CH(OCH.sub.3)-CH.sub.2 CO-Pro-Pro-K (I),and the acid salts thereof. A is an amino acid residue of the formula (CH.sub.3).sub.2 N--CHX--CO, wherein X is a normal or branched alkyl group. B is an amino acid residue selected from the group consisting of valyl, isoleucyl, leucyl, and 2-t-butylglycyl. D is a normal or branched C.sub.3 -C.sub.4 -alkyl group. K is a t-butoxy group or a substituted amino group.An additional embodiment of the present invention is a method for treating a malignancy in a mammal, such as a human, comprising administering to the mammal an effective amount of a compound or compounds of Formula I in a pharmaceutically acceptable composition.