y;for the manufacture of a medicament for use in therapy.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 depicts a comparison of antimitotic activity of Hemiasterlins with that of known antimitotic agents.FIG. 2 shows the antimitotic activity of chemically modified Hemiasterlins.DETAILED DESCRIPTION OF THE INVENTIONPreferably, R.sup.1 represents a hydrogen atom or an alkyl group, especially a methyl group