Experimental Antitumor Activity of Taxotere (RP 56976, NSC 628503), a Taxol Analogue

Abstract

Taxotere (RP 56976; NSC 628503; N-debenzoyl-N-tert-butoxycarbonyl-10-deacetyl taxol) is a new microtubule stabilizing agent. It is obtained by semisynthesis from a noncytotoxic precursor extracted from the needles of the tree, Taxus baccata L. Taxotere was evaluated for antitumor activity against a variety of transplantable tumors of mice. Taxotere had no marked schedule dependency and was found active by the i.v. and the i.p. routes. Upon i.v. administration, 9 of 11 tumor models tested responded to Taxotere. B16 melanoma was found highly sensitive to Taxotere, with a tumor growth inhibition of 0% and a 3.0 log₁₀ tumor cell kill at the maximum tolerated dose. In the same trial, taxol produced only a 1.1 log₁₀ tumor cell kill at the maximum tolerated dose. Taxotere cured early stage pancreatic ductal adenocarcinoma 03 (6 of 6 cures) and colon adenocarcinoma 38 (7 of 7 cures). It also effected greater than 80% complete regressions of advanced stage disease with both tumors. Taxotere was active against early and advanced stage colon adenocarcinoma 51, with 2.3 and 1.7 log₁₀ cell kill, respectively. Four other tumors responded to a lesser extent: Lewis lung (5.5% tumor growth inhibition), Glasgow osteogenic sarcoma (27.2% tumor growth inhibition), L1210 and P388 leukemias (70 and 54% increase in life span, respectively). Because of its good preclinical activity and its unique mechanism of action, Taxotere has entered Phase I clinical trials.