Intoplicine (RP 60475) dimesylate is a DNA topoisomerase I and II inhibitor belonging to the 7H-benzo[e]pyrido[4,3-b]indole series. It exhibits a strong affinity for DNA (K A = 2 x 10^5 /M), resulting in increased linear DNA length.

With 1-hour exposure to Intoplicine dimesylate at final concentrations of 2.5 micrograms/mL and 10.0 micrograms/mL, 26% and 54% of the assessable specimens shows positive in vitro responses, respectively[2]. With continuous exposure to Intoplicine dimesylate at concentrations of 0.25 micrograms/mL and 2.5 micrograms/mL, 16% and 71% of the assessable specimens showed positive responses, respectively[2]. Activity is seen against breast (71%), non-small-cell lung (69%), and ovarian (45%) cancer colony-forming units at a Intoplicine dimesylate concentration of 10.0 micrograms/mL after 1-hour exposure[2].

At the highest non-toxic dose (HNTD) (6 mg/kg/injection, total dose, 36 mg/kg), intoplicine dimesylate shows highly active with a T/C of 0% and a corresponding total log cell kill of 3[3].