New cytotoxic drugs and targets in oncology

Protein kinase C as a target for new anti-cancer agents

Cancer joins the category of diseases involving abnormalities in the rate of proliferation of cells and is associated with uncontrolled cell division, where cells either generate their own growth-promoting stimuli or neighboring cells or do not respond to growth inhibitory signals. Protein kinase C (PKC) is one of the key elements in the tumor growth signal transduction pathways and is found to be overexpressed in several malignant cell types. A way to control cell proliferation and cell differentiation is by influencing signal transduction pathways by modulation of PKC. PKC encloses 12 different isoenzymes, and each isoenzyme is found to have a different functional property. Because specific PKC isoenzyme types are present in different (malignant) cell species, they may be an attractive target in the development of anti-cancer agents. Classification and identification of the available PKC isoenzymes in different tumor cells could be useful in targeting specific tumors. PKC also tends to be overexpressed in association with the multidrug resistance pheno-type. This concise review deals with the role of PKC isoenzymes in (tumor) cell biology and evaluates the antineoplastic agents interacting on PKC isoenzymes.

Pharmaceutical development of a parenteral formulation of the novel anti-tumor agent carzelesin (U-80,244)

The aim of this study was to design a parenteral dosage form for the investigational cytotoxic drug carzelesin. A stable formulation in PET (Polyethylene glycol 400/absolute ethanol/Tween 80, 6:3:1, v/v/v) was developed. The prototype, containing 0.50 mg carzelesin in 2.0 ml PET formulation, was found to be the optimal formulation in terms of solubility, stability and dosage requirements in phase I clinical trials. Quality control of the formulation showed that the pharmaceutical preparation of carzelesin in PET is not negatively influenced by the manufacturing process. Shelf life studies demonstrated that the formulation is stable for at least 1 year, when stored at -30 degrees C in the dark. In addition, the stability of carzelesin in the PET formulation is discussed as a function of temperature, additives and after dilution in infusion fluids.

High-performance liquid chromatographic analysis of the antitumour drug camptothecin and its lactone ring-opened form in rat plasma

A sensitive high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of the antitumour drug camptothecin (I) and its lactone ring-opened form (II) in plasma. The sample pretreatment involved protein precipitation with cold methanol (-30 degrees C). The methanolic extract was injected directly onto the HPLC column. Chromatography was carried out with a LiChrosorb RP-18 column (particle size 5 microns) and a mobile phase composed of methanol-phosphate buffer (5 mM, pH 6.5)-0.3 M tetrabutylammonium phosphate solution (500:500:15, v/v/v). The column effluent was monitored spectrofluorimetrically with the excitation wavelength set at 369 nm and the emission wavelength at 426 nm. The chemical stabilities of camptothecin and the ring-opened form in aqueous solutions, in plasma and after methanolic extraction, were investigated. The proposed method was validated and utilized in pharmacokinetic studies with rats.