N-Benzyladriamycin (AD 288) is a highly lipophilic, semi-synthetic congener of 
doxorubicin (DOX). Unlike DOX, which stimulates double-stranded DNA scission by 
stabilizing topoisomerase II/DNA cleavable complexes, AD 288 is a catalytic 
inhibitor of topoisomerase II, capable of preventing topoisomerase II activity 
on DNA. The concentration of AD 288 required to inhibit the topoisomerase 
II-catalyzed decatenation of linked networks of kinetoplast DNA was comparable 
to that for DOX. However, AD 288 did not stabilize cleavable complex formation 
or stimulate topoisomerase II-mediated DNA cleavage. In addition, AD 288 
inhibited the formation of cleavable complexes by etoposide in a 
concentration-dependent manner. Human CCRF-CEM cells and murine J774. 2 cells 
exhibiting resistance against DOX, teniposide, or 
3'-hydroxy-3'-deaminodoxorubicin through reduced topoisomerase II activity 
remained sensitive to AD 288. These studies suggest that AD 288 inhibits 
topoisomerase II activity by preventing the initial non-covalent binding of 
topoisomerase II to DNA. Since AD 288 is a potent DNA intercalator, catalytic 
inhibition is achieved by prohibiting access of the enzyme to DNA binding sites. 
These results also demonstrate that specific substitutions on the aminosugar of 
DOX can alter the mechanism of topoisomerase II inhibition.