Characterization of the antitumor activity of hexadecylphosphocholine (D 18506).

Hexadecylphosphocholine (HPC) differs from ether lipids with known antitumor activity by its lack of the glycerol part. In the experiments described here HPC revealed outstanding antitumor activity in dimethylbenzanthracene (DMBA)-induced rat mammary tumors. A dose-response relationship was seen after daily oral treatment with complete suppression of tumor growth at doses of 46.4 mg/kg/day. There was no schedule dependence and the therapeutic efficacy was independent of the tumor weight at the initiation of therapy. Another autochthonous tumor, the benzo[a]pyrene-induced sarcoma of the rat did not respond to HPC treatment, indicating a highly selective spectrum of activity of the test compound. In comparison to an optimal single dose of cyclophosphamide, a single high dose of HPC was considerably more active against the DMBA tumor. At therapeutic dose levels no major toxicity of HPC was observed. Bone marrow suppression was not encountered, on the contrary, at high doses leukocytosis became apparent. The available pharmacological and toxicological data suggest that HPC may be useful in the treatment of human cancer.