• M Hidalgo, E Izbicka, C Cerna, L Gomez, E K Rowinsky, S D Weitman, and D D Von Hoff.
• Institute for Drug Development, Cancer Therapy and Research Center, and University of Texas Health Science Center at San Antonio, 78245-3217, USA.
• Anticancer Drugs. 1999 Mar 1; 10 (3): 295-302.

AbstractAdozelesin, bizelesin and carzelesin are synthetic cyclopropylpyrroloindole (CPI) analogs, a class of potent antineoplastic agents modeled on the antitumor antibiotic CC-1065, that specifically bind to the minor groove of DNA and preferentially alkylate AT-rich regions. These compounds were evaluated against fresh human tumors in a human tumor colony-forming assay (HTCFA) to assess and to compare their relative antitumor spectra, concentration-response relationships and schedule-dependence. Human tumor colony-forming units were treated with adozelesin and bizelesin at concentrations of 0.02, 0.1 and 0.5 ng/ml as a continuous exposure for 14 days, and to 0.2, 1.0 and 5.0 ng/ml as a 1 h exposure. Carzelesin concentrations were 0.04, 0.2 and 1 ng/ml as a continuous exposure, and 0.6, 3.0 and 15.0 ng/ml as a 1 h exposure. A response was scored if there was 50% or less colony survival. The three analogs had similar antitumor activity against colon carcinoma, kidney carcinoma and melanoma colony-forming units. Adozelesin also displayed activity against both breast and non-small cell lung carcinoma colony-forming units, and carzelesin was active against ovarian carcinoma colony-forming units. Significantly positive concentration-response relationships were apparent with all three agents. Responses increased from below 15% at the lowest concentration to above 45% at the highest concentration for the three drugs on all schedules (p < 0.01). At the highest concentration, the overall response rate was significantly higher (p < 0.01) with carzelesin on the continuous schedule (71%) compared to the 1 h schedule (46%). However, overall response rates for adozelesin and bizelesin were similar on both schedules (1 h/continuous: adozelesin, 67/58%; bizelesin, 49/44%), indicating that adozelesin and bizelesin are less schedule dependent than carzelesin in the HTCFA. These results demonstrate that the CPIs have broad-spectrum activity against human tumor colony-forming units in the HTCFA at very low concentrations, as well as differences with regard to schedule dependence which may help guide the optimal clinical development of these agents.

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