An in vitro model for de- and remyelination using lysophosphatidyl choline in rodent whole brain spheroid cultures.

The process of demyelination occurring in diseases as multiple sclerosis is usually investigated in animal models. A major drawback of animal models is that only one condition can be tested per animal, necessitating many animals and systemic effects are factors to be considered. The aim of the study was to develop a reproducible in vitro model for de- and remyelination using whole brain spheroid cultures and lysophosphatidyl choline (LPC). In spheroid cultures, single cell suspensions of embryonic day 15 rodent brain cells reaggregate under constant rotation. Three-dimensional contacts form between the central nervous system cell types present. Multilayered myelin is maximal in four-week old cultures. A week of repeated exposure to LPC led to 30% loss of MBP protein concentration and 2',3'-cyclic nucleotide 3'-phosphodiesterase activity measurements in both rat and mouse spheroids and 56% loss in the number of myelin sheets, with partial remyelination after a week of recovery. The number of dividing cells was increased after LPC exposure and oligodendrocytes were shown to be among the dividing cells. Microglia and astrocytes were not affected and neurons were relatively spared. This suggests that LPC toxicity is specific for myelin and oligodendrocytes. LPC toxicity could be decreased using cholesterol and simvastatin, suggesting that LPC works through altering membrane composition. Thus, in different rodent species and using different read-outs, we could reproducibly show de- and remyelination in spheroid cultures after LPC exposure. This model for demyelination with potential for remyelination offers possibilities for testing novel therapies and studying mechanisms of remyelination.

Phase I pharmacokinetic and pharmacodynamic study of the prenyl transferase inhibitor AZD3409 in patients with advanced cancer.

AZD3409 is an orally active double prodrug that was developed as a novel dual prenyltransferase inhibitor. The formation of the active metabolite AZD3409 acid is mediated by esterases in plasma and cells. The aim of this phase I study was to determine the maximum tolerated dose, toxicities, pharmacokinetics and pharmacodynamics of AZD3409. AZD3409 was administered orally to patients with advanced solid malignancies using an interpatient dose-escalation scheme starting at 500 mg AZD3409 once daily. Twenty-nine patients were treated at seven dose levels. The MTD of part A was defined as 750 mg b.i.d. in the fasted state. Adverse events were mainly gastrointestinal and the severity was on average mild to moderate and reversible. The dose-limiting toxicities were vomiting, diarrhoea and uncontrolled nausea. Pharmacokinetic studies of the prodrug and the active metabolite indicated dose proportionality. Pharmacodynamic studies showed that farnesyltransferase (FTase) was inhibited at all dose levels. In conclusion, chronic oral dosing with AZD3409 is feasible and results in significant inhibition of FTase activity. Pharmacodynamic studies revealed that the maximal FTase inhibition, estimated at 49+/-11%, appeared to be reached at AZD3409 acid plasma concentrations at which the occurrence of drug-related toxicity was low. This study supports the rationale to implement biological effect studies in clinical trials with biologically active anticancer drugs to define optimal dosing regimens.