Intoplicine (RP 60475) dimesylate, an antitumor derivative in the 7H-benzo[e]pyrido[4,3-b]indole series, is a DNA topoisomerase I and II inhibitor. Intoplicine dimesylate strongly binds DNA (KA = 2 x 105 /M) and thereby increases the length of linear DNA[1][2].
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].
[1]. Riou JF, et al. Intoplicine (RP 60475) and its derivatives, a new class of antitumor agents inhibiting both topoisomerase I and II activities. Cancer Res. 1993;53(24):5987-5993.
[2]. Eckardt JR, et al. Activity of intoplicine (RP60475), a new DNA topoisomerase I and II inhibitor, against human tumor colony-forming units in vitro. J Natl Cancer Inst. 1994;86(1):30-33.
[3]. Bissery MC, et al. Antitumor activity of intoplicine (RP 60475, NSC 645008), a new benzo-pyrido-indole: evaluation against solid tumors and leukemias in mice. Invest New Drugs. 1993;11(4):263-277.