[Classical oxazaphosphorines--metabolism and therapeutic properties--new implications]. / Klasyczne oksazafosforinany--metabolizm i wlasciwosci terapeutyczne--nowe implikacje.

Cyclophosphamide (CPA) and ifosfamide (IFO) belong to oxazaphosphorine drugs and for a few decades have been widely used for treatment of solid tumours and haematological malignancies. Both drugs are administered in pharmacologically inactive form and require metabolic activation by cytochrome P-450 (CYP). Metabolic transformations taking place under the action of specific CYP isoenzymes lead to the formation of therapeutically essential metabolites and some toxic compounds affecting quality of therapy. The first stage of these conversions is connected with hydroxylation reactions occurring on the C-4 carbon atom within a ring and C-1 atoms of 2-chloroethyl chains. As a result of C-4 hydroxylation 4-hydroxy derivatives (4-OH-CPA and 4-OH-IFO) are formed and remain in tautomeric equilibrium with aldo compounds which in cancer cells spontaneously release cytotoxic phosphoramide mustards and urotoxic acrolein. At the same time hydroxychloroethyl compounds formed during hydroxylation of side-chains are unstable and collapse with the release of inter alia nephro- and neurotoxic chloroacetaldehyde (CAA). Due to formation of toxic metabolites it is essential to use some preventive agents such as mesna and recently examined agmatine. Since CPA and IFO are widely used anticancer drugs, their efficacy is limited not only by their toxicity but also due to occurring resistance. This resistance seems to be a result of changes of expression and activity of enzymes such as CYP and aldehyde dehydrogenase (ALDH) and increase of intracellular levels of glutathione (GSH) and glutathione S-transferase (GST). At present a few methods of overcoming this resistance are being examined including the use of metabolism modulators, antisense oligonucleotides selectively inhibiting gene expression, and introducing genes of some CYP isoenzymes to a cancer tissue.

Anticancer effect of A-ring or/and C-ring modified oleanolic acid derivatives on KB, MCF-7 and HeLa cell lines.

New A-ring or/and C-ring modified methyl oleanolate derivatives were prepared. New simple method of synthesis of 3,12-diketone (3) from methyl oleanonate (2) was worked out. The obtained new compounds were tested for cytotoxic activity on KB, MCF-7 and HeLa cell lines. The derivatives had acetoxy, oxo or hydroxyimino function at the C-3 position and in some cases oxo, hydroxyimino or acyloxyimino group at the C-12 position. Almost all of the compounds showed strong cytotoxic activity, higher than unchanged oleanolic acid. The most active substances turned out to be the derivatives with acyloxyimino function, especially 4 and 8d.

Synthesis and anticancer activity of 5'-chloromethylphosphonates of 3'-azido-3'-deoxythymidine (AZT).

A series of novel N-alkyl 5'-chloromethylphosphonates of 3'-azido-3'-deoxythymidine (6-15) was synthesized by means of phosphonylation of 3'-azido-3'-deoxythymidine (4) with P-chloromethylphosphonic ditriazolide (3) followed by a reaction with the appropriate amine. The synthesized phosphonamidates 6-15 were evaluated for their cytotoxic activity in two human cancer cell lines: oral (KB) and breast (MCF-7) using the sulforhodamine B (SRB) assay. The highest activity in KB human cancer cells was displayed by phosphonamidate 8 (IC(50)=5.8 µg/mL), however, this compound was less potent than the parent AZT (IC(50)=3.1 µg/mL). Phosphonamidate 10 showed only moderate activity (IC(50)=12.1 µg/mL) whereas the other phosphonamidates proved inactive. Similarly, the highest activity in MCF-7 human cancer cells was displayed by phosphonamidate 8 (IC(50)=3.7 µg/mL) but it proved somewhat less active than AZT (IC(50)=2.6 µg/mL). Some activity was also displayed by phosphonamidate 10 (IC(50)=12.8 µg/mL) but the other phosphonamidates were found inactive. Hydrolysis studies indicate that the synthesized phosphonamidates are likely to act as prodrugs of the parent nucleoside (AZT). Transport measurements showed that the most active phosphonamidates (8 and 10) were able to permeate across the intestinal epithelium in vitro. The apparent permeability coefficients determined in Caco-2 cell monolayers indicated that these compounds could be moderately absorbed in humans.

In vitro cytostatic activity of 8-substituted and tricyclic analogues of acyclovir.

Out of a series of twenty 8-substituted or/and 1,N-2-bridged (tricyclic) derivatives of acyclovir (a selective antiherpetic drug), known to be nontoxic to normal cells, seven compounds were found to exhibit moderate cytostatic activity in KB human tumor tissue culture system with ED50 activity values ranging from 0.052-0.094 x 10(-3) mole/l. The structure-activity relationship analysis indicated that the primary factors determining their cytotoxicity were: 1) bromine atom at the C-8 position of the bicyclic derivatives and 2) unsubstituted appended ring in the tricyclic derivatives. Combination of two structural elements carrying the cytotoxicity gave diverse effects, enhancement or decrease in activity depending on particular cases. Two compounds (of four selected), 8-bromoacyclovir and 1,N-2-etheno-acyclovir, having unsubstituted 9-[(2-hydroxyethoxy)methyl] chain, showed approximately 2-fold increase in their cytotoxicity against HeLa tumor cells in the presence of the induced microsomal generating system suggesting that their cytotoxicity depends on the drug metabolic transformation into their active metabolites (intermediates) via MFO-system, and that structural unit of this chain is essential for abovementioned activation. Presently found remarkable cytotoxic selectivity of acyclovir analogues against KB and HeLa tumor cells together with previously reported in the literature specific cytotoxic activity of acyclovir against murine leukemia L 1210 cells seem to be encouraging for further investigation of this class of compounds in other tumor systems.