In vitro and in vivo cytotoxicity of alkyl lysophospholipid ET-18-OCH3 and thioether lipid BM 41.440

Miltefosine: a review of its pharmacology and therapeutic efficacy in the treatment of leishmaniasis

Miltefosine is an alkylphosphocholine drug with demonstrated activity against various parasite species and cancer cells as well as some pathogenic bacteria and fungi. For 10 years it has been licensed in India for the treatment of visceral leishmaniasis (VL), a fatal neglected parasitic disease. It is the first and still the only oral drug that can be used to treat VL and cutaneous leishmaniasis (CL). The standard 28 day miltefosine monotherapy regimen is well tolerated, except for mild gastrointestinal side effects, although its teratogenic potential severely hampers its general use in the clinic and roll-out in national elimination programmes. The pharmacokinetics of miltefosine are mainly characterized by its long residence time in the body, resulting in extensive drug accumulation during treatment and long elimination half-lives. At the moment, different combination therapy strategies encompassing miltefosine are being tested in multiple controlled clinical trials in various geographical areas of endemicity, both in South Asia and East Africa. We here review the most salient pre-clinical and clinical pharmacological aspects of miltefosine, its mechanism of action against Leishmania parasites and other pathogens, and provide a systematic overview of the efficacy and safety data from all clinical trials of miltefosine, either alone or in combination, in the treatment of VL and CL.

Effects of iron supplementation and ET-18-OCH3 on MDA-MB 231 breast carcinomas in nude mice consuming a fish oil diet

Lipid peroxidation products can be cytotoxic. Our objectives were (1) to use two pro-oxidants (iron and a pro-oxidative drug) to selectively increase lipid peroxidation in the implanted human breast tumours of mice consuming fish oil and (2) to kill the cancer cells without harming normal host tissues. The theoretical basis for selective cytotoxicity is that normal cells are better able to handle oxidative stress than cancer cells. Male athymic nude mice, consuming an AIN-76 diet, were injected s.c. with MDA-MB 231 human breast carcinoma cells. Three weeks later, all mice had palpable tumours, 3-10 mm in diameter, and diets were changed to modified AIN-76 diets containing 19% menhaden fish oil and 1% corn oil with or without supplemental 0.3% ferric citrate. After 2 weeks, half of the mice on each diet (19% fish oil with or without supplemental ferric citrate) were injected (three times per week for 2 weeks) with the ether-lipid drug edelfosine (ET-18-OCH3). The concentration of lipid peroxidation products in tumours (as measured by thiobarbituric acid-reactive substances, TBARS) was significantly increased by both ferric citrate and ET-18-OCH3. The TBARS in livers were not increased, nor was there evidence of other harmful side-effects to the host mice. The addition of iron enhanced tumour cell death whereas ET-18-OCH3 suppressed tumour cell mitosis. The use of iron supplementation combined with ET-18-OCH3 resulted in the slowest growth rate, lowest mitotic index, highest level of lipid peroxidation products and increased the cytotoxic index in tumours without detectable harm to the host. That iron supplementation increased tumour suppression beyond that expected from the increase in the concentration of TBARS in the tumour merits further investigation.

Analogs of alkyllysophospholipids: chemistry, effects on the molecular level and their consequences for normal and malignant cells

In the search for new approaches to cancer therapy, the first alkyllysophospholipid (ALP) analogs were designed and studied about two decades ago, either as potential immunomodulators or as antimetabolites of phospholipid metabolism. In the meantime, it has been demonstrated that they really act in this way. However, their special importance is based on the fact that, in addition, they interfere with key events of signal transduction, such as hormone (or cytokine)-receptor binding or processing, protein kinase C or phospholipase C function and phosphatidylinositol and calcium metabolism. There are no strict structural requirements for their activity. Differences in the cellular uptake or the state of cellular differentiation seem to be mainly responsible for higher or lower sensitivities of cells towards ALP analogs. Consequences of the molecular effects mentioned on the cellular level are cytostasis, induction of differentiation (while in contrast the effects of known inducers of differentiation such as 12-O-tetradecanoylphorbol-13-acetate are inhibited, probably as a consequence of protein kinase C inhibition) and loss of invasive properties. Already in sublytic concentrations, alterations in the membrane structure were observed, and lysis may begin at concentrations not much higher than those causing the other effects described. Few ALP analogs have already entered clinical studies or are in clinical use. ALP analogs are the only antineoplastic agents that do not act directly on the formation and function of the cellular replication machinery. Therefore, their effects are independent of the proliferative state of the target cells. Because of their interference with cellular regulatory events, including those failing in cancer cells, ALP analogs, beyond their clinical importance, are interesting model compounds for the development of new, more selective drugs for cancer therapy.

Antineoplastic activity of alkylphosphocholines (APC) in human breast carcinomas in vivo and in vitro; use of liposomes

This study examines the in vitro and in vivo activity of alkylphosphocholines (APC) in experimental human breast carcinomas. Three analogs, hexadecylphosphocholine (HPC), octadecylphosphocholine (OPC) and eicosanylphosphocholine (EPC) were investigated. Three hormone receptor negative cell lines were sensitive to all three APCs in vitro whereas the receptor positive MCF-7 line was more resistant. Sensitivity was seen in 4/6 hormone receptor negative tumors in vivo, with HPC being the most active analog. There were no antitumor effects in the four receptor positive models. The reasons for these differences in response between hormone receptor negative and -positive lines are not yet understood and require further study. Gastrointestinal toxicity and hemolysis, the major side effects of the APCs, were reduced by the use of liposomal preparations.

Enzymatic synthesis of structural analogs of PAF-acether by phospholipase D-catalysed transphosphatidylation

PAF-acether can be transformed into analogs by the phospholipase D enzyme activity of Streptomyces sp. In this reaction choline is replaced by primary cyclic alcohols (acceptors). The reaction products, cyclic phospholipid and phosphatidic acid, were separated by silicic acid chromatography. This procedure enabled us to synthetize five analogs of PAF-acether, with a cyclic ring structure. The primary cyclic alcohols used in this work were: 3-(2-hydroxyethyl)-indol, OH-Et-I; 2-(hydroxymethyl)-1,4-benzodioxan, OH-Met-BZD; N-(2-hydroxyethyl)-phthalimide, OH-Et-PHT; 2-(2-thienyl)-ethanol, Th-EtOH; (1-R)-(-)-Nopol, R-NOP.