Compounds of the present invention include cell growth inhibitors which are peptides of Formula I,A-B-D-E-F-(G).sub.r -(K).sub.s -L (I),and acid salts thereof, wherein A, B, D, E, F, G and K are .alpha.-amino acid residues, and s and r are each, independently, 0 or 1. L is a monovalent radical, such as, for example, an amino group, an N-substituted amino group, a .beta.-hydroxylamino group, a hydrazido group, an alkoxy group, a thioalkoxy group, an aminoxy group, or an oximato group. The present invention also includes a method for treating cancer in a mammal, such as a human, comprising administering to the mammal an effective amount of a compound of Formula I in a pharmaceutically acceptable composition.