Abstract: The invention relates to the use of compounds of formula (I): wherein X is —C(O)—, —C(S)—, —C?NOH, or —CH(R7)— wherein R7 is hydrogen, hydroxy, C1-7alkoxy, —OR8 or —NR8R9 (wherein R8 is a group —Y1R10 (wherein Y1 is a direct bond, —C(O)—, —C(S)—, —S—, —C(O)O, —C(O)NR11—, —SO2— or —SO2NR12— (wherein R11 and R12, which may be the same or different, each independently represents hydrogen, C1-3alkyl or C1-3alkoxyC2-3alkyl) and R10 is as defined herein, and R9 includes hydrogen; R1, R2 and R3 are as defined herein and are preferably methyl; R4, R5 and R6 are as defined herein with the proviso that R5 is not hydroxy, alkoxy, substituted alkoxy, —OPO3H2, —O—C1-7alkanoyl or benzyloxy; and salts thereof in the manufacture of a medicament for use in the production of a vascular damaging effect in warm-blooded animals such as humans.