Therapeutic activity of ET-18-OCH3 and hexadecylphosphocholine against mammary tumors in BD-VI rats.

The present therapy experiments with two different transplantable mammary tumors were performed to compare the therapeutic efficacy in BD-VI rats of 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3) and hexadecylphosphocholine (HPC). Both compounds were administered orally, subcutaneously or intracutaneously at equimolar doses ranging from 4.8 to 88 mumol/kg/day five times per week for two weeks. Under the experimental conditions, both transplanted mammary carcinomas were moderately sensitive to the therapy with either HPC or ET-18-OCH3. Comparing both tumors, TMA2 was more sensitive than TMA1. The activity and toxicity of both compounds were dose-related in both tumor lines. Females seemed to be less sensitive with respect to antineoplastic activity and toxicity. Like ET-18-OCH3, HPC was active also at low, probably noncytotoxic doses associated with no detectable toxicity according to body weight development. This suggests that there are at least two different mechanisms of action that lead to tumor growth inhibition.