Antitumour activity of miltefosine alone and after combination with platinum complexes on MXT mouse mammary carcinoma models.

Miltefosine, an alkylphosphocholine structurally related to alkyllysophospholipids showed highly selective antitumour activity against the hormone-sensitive variant of the s.c. transplantable MXT mouse mammary adenocarcinoma, the ovary-dependent MXT (M3.2), whereas it was inactive against the hormone-insensitive MXT (M3.2) OVEX variant. A dose of 32 mg/kg miltefosine p.o. daily for 5 weeks was well tolerated. Histopathological evaluation gave no signs of gastroenteral toxicity. After therapy the microarchitecture of the MXT (M3.2) tumours changed from that of a moderately differentiated adenocarcinoma to that of an anaplastic mammary carcinoma. A dose of 16 mg/kg miltefosine p.o. daily, though in effective per se, enhanced the antitumour activity of suboptimal i.p. doses of cisplatin and the hormone-like platinum analogue meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl) ethylenediamine]dichloroplatinum(II). Furthermore, it was shown, that miltefosine exhibited no (anti)hormonal properties. However, the mechanism of action of miltefosine remains unclear.