Controlled plasmid gene transfer to murine renal carcinoma by hexadecylphosphocholine

We report here that the anticancer drug hexadecylphosphocholine (HPC) can control plasmid DNA-mediated gene transfer to renal carcinoma following intratumoral administration. Significant improvement of gene expression levels could be achieved depending on HPC dose administered. Optimal concentration of HPC co-injected with plasmid DNA was found to be 0.2% (w/v) showing up to a 10-fold increase in reporter gene expression levels when compared to DNA administered alone. In vivo gene transfer activity of HPC was not affected by the nature of the diluent used, i.e. glucose-based or saline-based isotonic solutions. Although in vitro transfection activity of HPC formulations could not be evidenced, a liposome leakage assay revealed that HPC could significantly destabilize stable lipid membranes suggesting that a possible membrane permeation enhancer activity of HPC combined to the physical stress induced by the intratumor injection may facilitate plasmid DNA entry inside the cells resulting in increased gene expression. HPC/plasmid formulations represent new and attractive non-viral gene delivery systems with potential in cancer gene therapy and vaccination.

Secondary ion images of the developing rat brain

Secondary ion images were obtained from sections of rat brain over a 21 day postnatal period, using the intensity of m/z 184, phosphocholine. When compared with corresponding optical images of similar, but stained sections from the same animal, the secondary ion images appear to reflect less developed brains. During development, myelination occurs after axon extension. Apparently, myelination obscures the source of secondary m/z 184, phosphatidylcholine, from the analyzing ion probe; absenting myelination, secondary ion images show no physiological features.

Miltefosine (Impavido): the first oral treatment against leishmaniasis

Miltefosine is a novel antileishmanial drug that has significant selectivity in both in vitro and in vivo models. Clinical efficacy was demonstrated for the treatment of visceral leishmaniasis with the advantage of oral administration over the currently recommended antileishmanial drugs that require parenteral administration. Miltefosine produces high cure rates also in patients resistant to the standard antimonial therapy.

Lem3p is essential for the uptake and potency of alkylphosphocholine drugs, edelfosine and miltefosine

The alkylphosphocholine class of drugs, including edelfosine and miltefosine, has recently shown promise in the treatment of protozoal and fungal diseases, most notably, leishmaniasis. One of the major barriers to successful treatment of these infections is the development of drug resistance. To understand better the mechanisms underlying the development of drug resistance, we performed a combined mutant selection and screen in Saccharomyces cerevisiae, designed to identify genes that confer resistance to the alkylphosphocholine drugs by inhibiting their transport across the plasma membrane. Mutagenized cells were first selected for resistance to edelfosine, and the initial collection of mutants was screened a second time for defects in internalization of a short chain, fluorescent (7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD))-labeled phosphatidylcholine reporter. This approach identified mutations in a single gene, YNL323W/LEM3, that conferred resistance to alkylphosphocholine drugs and inhibited internalization of NBD-labeled phosphatidylcholine. Loss of YNL323W/LEM3 does not confer resistance to N-nitroquinilone N-oxide or ketoconazole and actually increases sensitivity to cycloheximide. The defect in internalization is specific to NBD-labeled phosphatidylcholine and phosphatidylethanolamine. Labeled phosphatidylserine is internalized at normal levels in lem3 strains. LEM3 is a member of an evolutionarily conserved family and has two homologues in S. cerevisiae. Single point mutations that produce resistance to alkylphosphocholine drugs and inhibition of NBD-labeled phosphatidylcholine internalization were identified in several highly conserved domains. These data demonstrate a requirement for Lem3p expression for normal phosphatidylcholine and alkylphosphocholine drug transport across the plasma membrane of yeast.

Oral miltefosine treatment in children with mild to moderate Indian visceral leishmaniasis

BACKGROUND

Miltefosine is the first oral drug with demonstrable success in treating visceral leishmaniasis in adults. Because approximately one-half of the visceral leishmaniasis patients worldwide are children, we performed a Phase I/II dose ranging study in the pediatric population in India.

METHODS

Thirty-nine (39) children (defined as < 12 years of age) with visceral leishmaniasis demonstrated by parasites in splenic aspirates, were treated with oral miltefosine daily for 28 days: 21 patients received 1.5 mg/kg/day (Group A); and 18 patients received 2.5 mg/kg/day (Group B). About one-half of these children had failed prior antileishmanial treatment.

RESULTS

All patients were parasitologically negative and symptomatically improved by the end of therapy on Day 28 of therapy; the initial parasitologic cure rate was 100%. Two patients in each treatment group relapsed with fever, splenomegaly and parasite-positive splenic aspirates by the end of the 6-month follow-up. The per protocol final clinical cure rate was 19 of 21 = 90% in Group A and 15 of 17 = 88% in Group B. Miltefosine was well-tolerated. As per the adult experience, gastrointestinal adverse events were seen: 33 and 39% of children experienced vomiting and 5 and 17% experienced diarrhea in Groups A and B, respectively, but all episodes were mild to moderate in severity and commonly lasted <1 day without symptomatic treatment.

CONCLUSION

Oral miltefosine was safe and approximately 90% effective in this initial clinical trial of childhood visceral leishmaniasis.

Increased delivery of erucylphosphocholine to C6 gliomas by chemical opening of the blood-brain barrier using intracarotid pentylglycerol in rats

BACKGROUND

Erucylphosphocholine (ErPC) has been shown to exert strong antineoplastic effects against various brain tumor cell lines in vitro. Since ErPC only enters the brain after long-term treatment, ineffective drug delivery to the tumor is considered to be the reason for the moderate responses to chemotherapy with ErPC observed in animal brain tumor models. We investigated a recently described method for chemically opening the blood-brain barrier (BBB) using intraarterial administration of alkylglycerols to increase the transfer of ErPC into the brain.

METHODS

ErPC (40 mg/kg) was given to C6 glioma-bearing rats either as a single intracarotid bolus injection in the presence or absence of 1- O-pentylglycerol (300 m M) or as an intracarotid infusion in conjunction with bradykinin. Brain tissue concentrations were analyzed and compared to values obtained after intravenous ErPC treatment over 14 and 30 days (cumulative ErPC doses of 210 and 350 mg/kg, respectively).

RESULTS

Pentylglycerol-induced BBB opening resulted in a significant increase in ErPC delivery to the tumor (17-fold) and, to a lesser extent, to the surrounding ipsilateral brain (7-fold) compared to intraarterial ErPC administration without alkylglycerol ( P<0.05). Furthermore, the resulting ErPC concentrations in the brain tumor exceeded those obtained in tumor and tumor-free brain after long-term intravenous ErPC administration. In contrast to this, intracarotid bradykinin did not increase the transfer of ErPC to the tumor or tumor-free brain.

CONCLUSIONS

The intracarotid administration of pentylglycerol represents a novel and nontoxic method of overcoming the limited access of ErPC to both brain tumors and brain tissue adjacent to tumors. The present results provide further evidence that chemical opening of the BBB by intraarterial alkylglycerols is a promising new concept for improving delivery of chemotherapeutic agents to brain tumors.

Phase I and pharmacological study of daily oral administration of perifosine (D-21266) in patients with advanced solid tumours

Alkylphosphocholines are a novel class of antitumour agents structurally related to ether lipids that interact with the cell membrane and influence intracellular growth signal transduction pathways. We performed a phase I trial with an analogue of miltefosine, perifosine (D-21266), which was expected to induce less gastrointestinal toxicity. Objectives of the trial were: to determine the maximum-tolerated dose (MTD) for daily administration, to identify the dose-limiting toxicity (DLT) of this schedule, to assess drug accumulation and to determine the relevant pharmacokinetic parameters. 22 patients with advanced solid tumours were treated at doses ranging from 50 to 350 mg/day for 3 weeks, followed by 1 week of rest. Toxicity consisted mainly of gastrointestinal side-effects: nausea was reported by 11 patients (52%, 10 patients Common Toxicity Criteria (CTC) grades 1-2 and 1 patient CTC grade 3), vomiting by 8 (38%, all CTC grades 1-2), and diarrhoea by 9 (43%, 8 patients CTC grades 1-2 and 1 patient CTC grade 3). The severity of these side effects appeared to increase with increasing doses. Another common side-effect was fatigue, occurring in 9 patients (43%). No haematology toxicity was observed. Dose-limiting toxicity (DLT) was not reached, but gastrointestinal complaints led to an early treatment discontinuation in an increasing number of patients at the higher dose levels. Therefore, MTD was established at 200 mg/day. The pharmacokinetic studies suggested dose proportionality.

Clearance of surfactant lipids by neutrophils and macrophages isolated from the acutely inflamed lung

Pulmonary surfactant reduces surface tension at the lung air-liquid interface and defends the host against infection. Several lines of evidence show that surfactant levels are altered in animal models and patients with inflammatory or infectious lung diseases. We tested the hypothesis that cells responding to lung injury alter surfactant levels through increased phospholipid clearance. Acute lung injury was induced by intratracheal administration of lipopolysaccharide (LPS; Escherichia coli 026:B6) into rats. LPS exposure resulted in a 12-fold increase in the number of cells isolated by lavage, the majority of which were neutrophils. Isolated macrophages and neutrophils from LPS-treated lungs internalized and degraded lipids in vitro, and LPS injury stimulated uptake by macrophages twofold. We estimate that lipid clearance by lavage cells in LPS-treated lungs could be enhanced 6- to 13-fold with both activated macrophages and increased numbers of neutrophils contributing to the process. These data show that the increased number of cells in the alveolar space after acute lung injury may lead to alterations in surfactant pools via enhanced clearance and degradation of lipids.

Quantitative determination of perifosine, a novel alkylphosphocholine anticancer agent, in human plasma by reversed-phase liquid chromatography-electrospray mass spectrometry

A sensitive and selective reversed-phase LC-ESI-MS method to quantitate perifosine in human plasma was developed and validated. Sample preparation utilized simple acetonitrile precipitation without an evaporation step. With a Develosil UG-30 column (10 x 4 mm I.D.), perifosine and the internal standard hexadecylphosphocholine were baseline separated at retention times of 2.2 and 1.1 min, respectively. The mobile phase consisted of eluent A, 95% 9 mM ammonium formate (pH 8) in acetonitrile-eluent B, 95% acetonitrile in 9 mM ammonium formate (pH 8) (A-B, 40:60, v/v), and the flow-rate was 0.5 ml/min. The detection utilized selected ion monitoring in the positive-mode at m/z 462.4 and 408.4 for the protonated molecular ions of perifosine and the internal standard, respectively. The lower limit of quantitation of perifosine was 4 ng/ml in human plasma, and good linearity was observed in the 4-2,000 ng/ml range fitted by linear regression with 1/x weight. The total LC-MS run time was 5 min. The validated LC-MS assay was applied to measure perifosine plasma concentrations from patients enrolled on a phase I clinical trial for pharmacokinetic/pharmacodynamic analyses.

Erucylphosphocholine: pharmacokinetics, biodistribution and CNS-accumulation in the rat after intravenous administration

The clinical use of alkylphosphocholines (APC) in cancer patients is restricted because of the high gastrointestinal toxicity and the need for oral administration. Therefore we evaluated the clinical pharmacology of erucylphosphocholine (ErPC), the first derivative of the APC family suitable for intravenous administration with strong antineoplastic activity, in vitro and in vivo in rats. The pharmacokinetic parameters after a single intravenous dose of 40 mg/kg were calculated using a two-compartment model: C(max) = 1.6 +/- 0.3 micromol/ml, T(1/2alpha) = 0.18 +/- 0.09 h, T(1/2beta) = 3.3 +/- 0.88 h, clearance = 9.7 +/- 1.2 ml/h, AUC = 2.5 +/- 0.3 micromol/ml per h and Vss = 40.4 +/- 7.9 ml. Biodistribution studies were performed after repeated ErPC administration at different doses. Intravenous injections of 20 mg/kg given at intervals of 48 h for up to 4 weeks were well tolerated. Neither clinical evaluation nor laboratory parameters (haematology and clinical chemistry) revealed toxic side effects. In contrast, higher doses of ErPC (40 mg/kg per 48 h) led to weight loss. After 2 and 4 weeks of therapy with 20 mg/kg per 48 h a high ErPC accumulation was found in the adrenal glands, small intestine and brain. The brain to serum concentration ratios averaged 2.1 after 2 weeks and 4.5 after 4 weeks. Significant leucocytosis and thrombocytosis were observed after 4 weeks of ErPC treatment. The findings suggest that ErPC is a suitable candidate for clinical trials. In particular, owing to the high accumulation in brain tissue, ErPC is a potential agent for chemotherapy against malignant brain tumours.

Pharmacokinetics of sterically stabilized hexadecylphosphocholine liposomes versus conventional liposomes and free hexadecylphosphocholine in tumor-free and human breast carcinoma bearing mice

The pharmacokinetics of free and different liposomal formulations of hexadecylphosphocholine (HPC) was investigated in tumor-bearing (human mammary tumor MaTu) and tumor-free mice after intravenous and intraperitoneal administration. The levels of HPC were evaluated at different times in serum, normal tissues, and tumor. The purpose was to test the hypothesis that the enhanced therapeutic efficacy of sterically stabilized HPC liposomes in comparison to conventional vesicles and free HPC is due to its pharmacokinetics. Conventional non-compartmental pharmacokinetic analysis and an elaborate three- and four-compartmental model were used for explaining the experimental data. The serum levels of HPC obtained with sterically stabilized liposomes were only consistently higher in comparison to conventional vesicles and free HPC in the first 4 h. In the xenografted MaTu carcinoma, the differences of the HPC content between the different groups are unexpectedly low and do not reflect the high therapeutic activity [5] of sterically stabilized HPC liposomes. Detailed analysis shows that the liposomally encapsulated drug displays a modified pharmacokinetic behavior, which may also involve lymphatic absorption of the liposomal drug.

A 1H-decoupled 31P chemical shift imaging study of medicated schizophrenic patients and healthy controls

BACKGROUND

Current 31P spectroscopy research in schizophrenia has examined phospholipid metabolism by measuring the sum of phosphomonoesters and the sum of phosphodiester-containing molecules. Proton decoupling was implemented to measure the individual phosphomonoester and phosphodiester components. This is the first study employing this technique to examine schizophrenic patients.

METHODS

Multivoxel two-dimensional chemical shift in vivo phosphorous-31 magnetic resonance spectroscopy with proton decoupling was used to examine a 50-cm3 volume in prefrontal, motor, and parieto-occipital regions in the brain. Eleven chronic medicated schizophrenic patients were compared to 11 healthy controls of comparable gender, education, parental education, and handedness.

RESULTS

A significant increase in the mobile phospholipid peak area and its full width at half maximum was observed in the medicated schizophrenic patients compared to the healthy controls in the prefrontal region. Inorganic orthophosphate and phosphocholine were lower in the schizophrenic group in the prefrontal region.

CONCLUSIONS

The increased sum of phosphodiester [mobile phospholipid + glycerol-3-phosphoethanolamine (GPEth) + glycerol-3-phosphocholine (GPCh)] in schizophrenic patients, measured in earlier studies, arises from the phospholipid peak (MP) and not the more mobile phosphodiesters (GPEth, GPCh) as was originally suspected. A decrease in the phosphocholine component of the phosphomonoesters was also observed in the schizophrenic patients. These findings are consistent with an abnormality in membrane metabolism in the prefrontal region in schizophrenics.

Quantification of perifosine, an alkylphosphocholine anti-tumour agent, in plasma by pneumatically assisted electrospray tandem mass spectrometry coupled with high-performance liquid chromatography

An HPLC assay with tandem mass spectrometric detection in the positive-ion Turbo-Ion-Spray (TISP) mode for the fast and sensitive determination of perifosine ((I), D-21266) in human plasma was developed, utilising the structural analogue, miltefosine ((II), D-18506), as internal standard. Automated solid-phase extraction of diluted plasma samples, based on 250-microl plasma aliquots, at pH 6.5, allowed a reliable quantification of perifosine down to 4 ng/ml. Injection of 200 microl of plasma extracts onto a 100x3 mm normal-phase analytical column at a flow-rate of 0.5 ml/min provided retention-times of 2.4 and 2.1 min for perifosine (I) and the internal standard (II), respectively. The standard curves were linear from 4 to 2000 ng/ml using weighted linear regression analysis (1/Y2). The inter-assay and intra-assay accuracies for the calibration standards were within +0.9% and -0.2%, exhibiting precisions (C.V.) of +/-6.5 and +/-7.3%, respectively. Up to 100 unknowns may be analysed each 24 h per analyst.

Erucylphosphocholine, a novel antineoplastic ether lipid, blocks growth and induces apoptosis in brain tumor cell lines in vitro

A potential benefit of alkylphosphocholines in brain tumor therapy was evaluated. The in vitro effects of the intravenously applicable erucylphosphocholine (ErPC) on proliferation, viability, morphology and cell cycle distribution of a rat glioma, four human astrocytoma/glioblastoma and a human medulloblastoma cell line were analyzed daily after continuous drug-exposure for up to six days. ErPC exerted strong cytostatic and direct cytotoxic effects on all cell lines tested at drug concentrations that are achieved in the rat brain after repeated intravenous injections of nontoxic drug doses. Concentrations of 70 microM (T98G, A172, 85HG66, 86HG39) and 110 microM (C6, D283 Med) led to complete cell death within 48-96 h. Particular characteristics of ErPC action are i) the accumulation of cells with a 4n DNA content corresponding to the G2/M-phase of the cell cycle, ii) the formation of two- and multinucleated cells and iii) the induction of apoptosis.

Antitumor effects of erucylphosphocholine on brain tumor cells in vitro and in vivo

The antineoplastic activity of erucylphosphocholine (ErPC) on C6 rat glioma cells and the human glioblastoma cell lines A172 and T98G was studied in vitro. ErPC exerted concentration- and time-dependent cytostatic and cytotoxic actions. The effects of ErPC on C6 cells were stronger than hexadecylphosphocholine and similar to 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine. The human cell lines were more sensitive to ErPC (LC50 = 36 microM and 29 microM) than C6 cells (LC50 = 70 microM) (48 hours, WST-1-test). Morphological characteristics of apoptotic cell death were observed. Rats bearing intracerebral and subcutaneous gliomas were treated with intravenous ErPC for 30 days to determine the antitumor effects of ErPC in vivo. ErPC accumulation in subcutaneous tumors was higher than in brain tissue. Peripheral tumors revealed a better response than CNS-tumors. There was a strong negative relationship between the concentration of ErPC and the weight of peripheral tumors. ErPC is considered to be promising for chemotherapy of malignant brain tumors.

Antineoplastic activity of sterically stabilized alkylphosphocholine liposomes in human breast carcinomas

New sterically stabilized liposomes derived from the antitumor agent hexadecylphosphocholine with reduced uptake by the mononuclear phagocyte system and improved antitumor activities were developed and tested. The bilayer of such sterically stabilized liposomes consists of hexadecylphosphocholine, cholesterol and polyethylene glycol-linked phosphoethanolamine. The measurement of carbon clearance in mice shows that these stabilized liposomes, in contrast to conventional alkylphosphocholine liposomes, are not largely engulfed by the mononuclear phagocyte system. Their therapeutic activity on experimental human breast carcinomas MaTu. MT-1 and MT-3 was tested in nude mice. Especially in the MaTu models the sterically stabilized hexadecylphosphocholine liposomes resulted in significantly reduced tumor growth in comparison to conventional hexadecylphosphocholine liposomes or free hexadecylphosphocholine. The enhanced therapeutic efficacy of sterically stabilized hexadecylphosphocholine liposomes is probably related to the extended circulation time of the formulation and its accumulation in tumors.

Electromagnetic field induced changes in lipid second messengers

Initial studies with a human hematopoietic cell line, TF-1, suggest multifarious effects of electromagnetic fields on lipid signal transduction. We have examined the effects of pulsed magnetic fields (2 T, 84 microseconds zero-to-peak haversine, 91 V/m induced electric field) on the cell cycle by flow cytometry. A 31% increase of cells in the G1 phase occurred concurrently with a 35% decrease of cells in S-phase, which suggests that doses of 30 or 40 pulses have an anti-proliferative effect. Changes in the lipid second messengers, diacylglycerol (DAG) and phosphatidic acid (PA) with stimuli of 2 T intensity were also dependent on the number of pulses. DAG production doubled with 30 pulses and tripled with 40 pulses, and PA levels were reduced to one third and one tenth of the original levels. Phospholipase D (PLD) up-regulation was assessed directly by the capacity of PLD to catalyze transphosphatidylation in the presence of alcohol. [3H]Phosphatidylethanol formed rapidly and continued to increase with concomitant decreases in [3H]PA and parallel generation of [3H]DAG. Propranolol, an inhibitor of PA phosphohydrolase, inhibited the formation of DAG in a dose-dependent manner with a marked increase in PA production. Examination of the kinetics of formation of [3H]choline and [3H]phosphocholine at different times after stimulation showed a rapid and consistent increase in [3H]choline, whereas [3H]phosphocholine increase was evident only 60 min after stimulation. Magnetic exposure also caused a shift in some molecular species patterns of DAG and PA which could be correlated with phosphatidylinositol, phosphatidylethanolamine and phosphatidylcholine molecular species decreases. Therefore, we propose that the PC-PLC pathway may be temporarily inactivated for a short period of time by exposure to pulsed stimuli, and the PC-PLD pathway is up-regulated based on: (1) cellular release of [3H]choline; (2) rapid intracellular formation of [3H]PA followed by [3H]DAG; (3)active transphosphatidylation; and (4) blockade of DAG formation by propranolol.

Early stage monitoring of miltefosine induced apoptosis in KB cells by multinuclear NMR spectroscopy

Synthetic ether lipids, like miltefosine (hexadecylphosphocholine), an alkylphosphocholine, are antineoplastic agents in vitro and in vivo. Their mode of action is mediated via the cell membrane, but the mechanism is still unclear. Miltefosine induces apoptosis in human epithelial KB cells, but slows down only proliferation in rat C6 glioma cells. NMR spectroscopy on lipid extracts reveals increased diacylglycerol and triacyglycerol biosynthesis in KB cells prior to DNA fragmentation indicating a CTP:phosphocholine-cytidylyl-transferase (CT) inhibition by the drug. Although C6 cells were morphologically affected by alterations in phospholipid composition and metabolism by a long term treatment (23 days) with the drug, no persistent diacylglycerol increase is observed.

Pharmacokinetic behavior and antineoplastic activity of liposomal hexadecylphosphocholine

Hexadecylphosphocholine (HePC) shows remarkable antineoplastic efficacy in Sprague-Dawley rats bearing methylnitrosourea-induced mammary carcinoma. Unfortunately, this is accompanied by detrimental side effects that include gastrointestinal damage, body weight loss, and thrombophlebitis after i.v. injection, which has precluded the use of the HePC in humans, where nausea and vomiting can occur at noneffective dose levels. We have developed small unilamellar vesicles (SUVs) composed of HePC, cholesterol, and 1,2-dipalmitoyl-sn-gly-cero-3-phosphoglycerol, which can be given p.o. and i.v. In contrast to the free drug, the toxicity of liposomal HePC is shown to be greatly reduced, and there is no risk of thrombophlebitis. Single administration of equimolar HePC doses results in differing pharmacokinetic values for free HePC (p.o.) and HePC-SUVs (p.o., i.v.).

Investigations on the cellular uptake of hexadecylphosphocholine

The uptake of [(9,10)-3H]hexadecylphosphocholine (HePC) in six tumor cell lines was studied. All cell lines incorporated HePC in similar amounts, with the exception of the epidermoid cancer cell line KB, which took up higher amounts of HePC. The uptake of HePC at 37 degrees C was shown to be time and concentration dependent. At 20 degrees C, uptake was drastically reduced and at 4 degrees C it was blocked completely. Binding of HePC, at 4 degrees C, was not saturable at concentrations between 5 micrograms/mL (11.8 microM) and 100 micrograms/mL (235.3 microM), indicating that cell surface binding is not receptor-mediated. Furthermore, the effects of inhibitors of endocytosis were investigated. We observed a pronounced inhibitory effect by monensin and cytochalasin B. Colchicine was somewhat less effective whereas chloroquine was almost without effect. From these data we conclude that uptake of HePC is most probably mediated via a receptor-independent endocytotic mechanism.

In vitro and in vivo antitumoral activity of alkylphosphonates

Hexadecylphosphocholine is a new antitumour agent with a highly selective activity in chemically induced mammary tumours. It was suggested, that hexadecylphosphocholine is a pro-drug, cleavable by phospholipases C and/or D, creating hexadecanol or hexadecylphosphate as the active principle. To test this hypothesis, the antineoplastic activity of three alkylphosphonates, cleavable either by phospholipase C or D, are compared with those of the parent compound, hexadecylphosphocholine. Cell culture experiments, in which radiolabelled alkylphosphonates were incubated with a neoplastic cell line, showed no metabolism even after 3 days of incubation. In in vivo experiments with dimethylbenzanthracene-induced rat mammary carcinomas, all three alkylphosphonates showed antineoplastic activity, although none of them reached the high activity of hexadecylphosphocholine. These results indicate that the antitumoral activity of alkylphosphocholines and alkyl lysophosphatidylcholines is due to direct toxicity and not dependent on metabolism by phospholipases C or D or related enzymes.

Distribution of hexadecylphosphocholine and octadecyl-methyl-glycero-3-phosphocholine in rat tissues during steady-state treatment

The distribution of the alkylphosphocholine hexadecylphosphocholine (He-PC) and the (alkyl)lysophospholipid 1-0-octadecyl-2-0-methyl-rac-glycero-3-phosphocholine (ET18-OCH3) was analyzed in rats. The compounds were given orally at a daily dose of 75 mumol/kg body weight. After 6, 11, and 18 days, three rats in each treatment group were killed and the drug concentration in various tissues and fluids was determined. With the exception of the kidney (He-PC) and brain (He-PC and ET18-OCH3), steady-state levels of the drugs could be achieved in all organs investigated and in serum. Maximal concentrations of He-PC were found in the kidney, adrenal glands, and spleen, whereas the highest concentrations of ET18-OCH3 were detected in the adrenal glands, spleen, and small intestine. The concentrations of He-PC exceeded those of ET18-OCH3 in most tissues by a factor of about 2-25. Since samples of urine and feces did not contain detectable amounts of the compounds, the absorption of both lipid analogues was assumed to be complete. The total amount of He-PC recovered after 6, 11, and 18 days was 15%, 12%, and 6%, respectively, and that of ET18-OCH3 was 1.3%, 0.8%, and 0.3%, respectively. This indicates that the bioavailability of He-PC and ET18-OCH3 is not controlled by differences in the uptake of the two drugs, but by differences in their metabolism. The results could explain the differing efficacy of these two compounds in their antitumor action in animal models.

Alkylphosphocholines: influence of structural variation on biodistribution at antineoplastically active concentrations

Hexadecylphosphocholine (HPC) and octadecylphosphocholine (OPC) show very potent antitumor activity against autochthonous methylnitrosourea-induced mammary carcinomas in rats. The longer-chain and unsaturated homologue erucylphosphocholine (EPC) forms lamellar structures rather than micelles, but nonetheless exhibits antineoplastic activity. Methylnitrosourea was used in the present study to induce autochthonous mammary carcinomas in virgin Sprague-Dawley rats. At 6 and 11 days following oral therapy, the biodistribution of HPC, OPC and EPC was analyzed in the serum, tumor, liver, kidney, lung, small intestine, brain and spleen of rats by high-performance thin-layer chromatography. In contrast to the almost identical tumor response noted, the distribution of the three homologues differed markedly. The serum levels of 50 nmol/ml obtained for OPC and EPC were much lower than the value of 120 nmol/ml measured for HPC. Nevertheless, the quite different serum levels resulted in similar tumor concentrations of about 200 nmol/g for all three of the compounds. Whereas HPC preferably accumulated in the kidney (1 mumol/g), OPC was found at increased concentrations (400 nmol/g) in the spleen, kidney and lung. In spite of the high daily dose of 120 mumol/kg EPC as compared with 51 mumol/kg HPC or OPC, EPC concentrations (100-200 nmol/g) were low in most tissues. High EPC concentrations were found in the small intestine (628 nmol/g). Values of 170 nmol/g were found for HPC and OPC in the brain, whereas the EPC concentration was 120 nmol/g. Obviously, structural modifications in the alkyl chain strongly influence the distribution pattern of alkylphosphocholines in animals. Since EPC yielded the highest tissue-to-serum concentration ratio in tumor tissue (5.1) and the lowest levels in other organs, we conclude that EPC is the most promising candidate for drug development in cancer therapy.

Hexadecylphosphocholine: preclinical and the first clinical results of a new antitumor drug

Dose-response studies on cytotoxic alkyl lysophospholipids with various chemical structures revealed that a long alkyl chain and a polar group are essential for antitumor activity. The combination of both the long alkyl chain and a phosphocholine group thus results in alkyl phosphocholines. Preclinical studies with hexadecylphosphocholine (He-PC) as a representative compound indicate distinct antineoplastic activity on leukemia cells of human origin. He-PC is highly effective in inhibiting the growth of chemically induced rat mammary carcinomas. Even more striking is the fact that a high percentage of the tumors regressed completely. In a clinical phase I trial on breast cancer patients with local recurrences, topically applied He-PC resulted in regression of skin metastases. A phase II trial for topical treatment and a phase I trial for orally applied He-PC have been initiated to further evaluate the antitumoral activity of this new compound.