This invention provides aryl-substituted acyclic enediyne compounds of formula (I): ##STR00001## or a pharmaceutically acceptable salt or solvate thereof, wherein R.sub.1=R.sub.2=H; or R.sub.1 and R.sub.2 together form a moiety represented by the formula ##STR00002## R.sub.3 represents a substituted or unsubstituted alkyl having 4-30 carbon atoms, or a substituted or unsubstituted aryl group having 3-30 carbon atoms; and R.sub.4 represents a substituted or unsubstituted aryl group having 3-30 carbon atoms; with the proviso that R.sub.3 is not butyl, pentyl, tetrahydropyranyloxymethyl, tetrahydropyranyloxypropyl or phenyl when R.sub.1=R.sub.2=H and R.sub.4 is o-cyanophenyl,; and with the proviso that R.sub.3 is not butyl when R.sub.1=R.sub.2=H and R.sub.4 is phenyl. The compounds of formula (I) are found to have inhibitory activities against topoisomerase I or act as a S phase or G2/M phase blocker.