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.

Following exposure to Intoplicine dimesylate for one hour at concentrations of 2.5 and 10.0 micrograms/mL, in vitro assays demonstrated positive responses in 26% and 54% of the evaluated specimens, respectively[2]. Continuous exposure to the compound at lower concentrations of 0.25 and 2.5 micrograms/mL resulted in 16% and 71% of specimens showing positive responses, accordingly[2]. Notably, Intoplicine dimesylate exhibited activity against various cancer types, with efficacy observed in 71% of breast, 69% of non-small cell lung, and 45% of ovarian cancer colony-forming units at a concentration of 10.0 micrograms/mL following a one-hour exposure period[2].

At the highest non-toxic dose (HNTD) of 6 mg/kg per injection (total dose of 36 mg/kg), intoplicine dimesylate exhibited significant activity, as indicated by a tumor control (T/C) rate of 0% and a total log cell kill value of 3[3].