Intoplicine is the most active analogue evaluated in the 7H-benzo[e]-pyrido-[4,3-b]-indole series of antineoplastic compounds. Activity of Intoplicine against human tumor colony-forming units in vitro. Intoplicine shows its activity through inhibition of DNA topoisomerase I and II[1]. Intoplicine is found to unwind DNA and to inhibit purified calf thymus topoisomerase II via stabilization of the ternary cleavable complex[2].