Preclinical studies of steroid-linked nitrosoureas in murine pancreatic adenocarcinoma PANO2.

PURPOSE: In earlier studies, this laboratory carried out research on the synthesis and anticancer evaluation of hybrid compounds, which combine two molecules in one such as homo-aza-steroidal esters (HASE) of carboxylic derivatives of N, N-bis (2-chloroethyl) aniline. In this combination, steroidal hormones are employed as carriers for transporting the alkylating agents to specific targeted tissues. Aiming to continue our research, we used alkylating agents, as nitrosoureas, instead of nitrogen mustards. In this work the N-[N- (2-chloroethyl)-N-nitroso-carbomoyl]-L-alanine (CNC-ala) has been used and was bound to 7 newly synthesized modified steroidal esters (carrier molecule) of nitrosourea and the hybrid molecules were tested for antitumor activity against PANO2 murine pancreatic adenocarcinoma. MATERIALS AND METHODS: PANO2 adenocarcinoma was used in this study. C57Bl mice were used for chemotherapy evaluation. The activity was assessed from the inhibition of tumor growth and the oncostatic parameter T/C %. RESULTS: The antitumor activity displayed by 7 hybrid steroidal esters of nitrosourea was quite interesting. It was able to discern 4 of 7 compounds that exhibited considerable antitumor activity, increasing the lifespan of the tumor-bearing mice by inhibiting the tumor growth. CONCLUSION: The comparative study of 7 newly synthesized hybrid steroidal esters of nitrosourea shows that the antitumor effects of compound 7, which has an enlarged (7 carbon atoms) A-lactamic ring and nitrosourea esterified at the position 17, which seems to be the most appropriate for the connection of a DNA cross-linking amino acid derivative is superior.

Melanocyte-Directed enzyme prodrug therapy (MDEPT): development of second generation prodrugs for targeted treatment of malignant melanoma.

Evaluation of second generation prodrugs for MDEPT, by oximetry, has highlighted structural properties that are advantageous and disadvantageous for efficient oxidation using mushroom tyrosinase. In particular, a sterically undemanding prodrug bis-(2-chloroethyl)amino-4-hydroxyphenylaminomethanone 28 was synthesised and found to be oxidised by mushroom tyrosinase at a superior rate to tyrosine methyl ester, the carboxylic acid of which is the natural substrate for tyrosinase. The more sterically demanding phenyl mustard prodrugs 9 and 10 were oxidised by mushroom tyrosinase at a similar rate to tyrosine methyl ester. In contrast, tyramine chain elongation via heteroatom insertion was detrimental and the rate of mushroom tyrosinase oxidation of phenyl mustard prodrugs 21 and 22 decreased by 10 nanomol/min.

Thiazolidinyl- and perhydrothiazinylphosphamidesters: toxicity and preliminary antitumour evaluation.

Aldophosphamide thiazolidine (NSC 613060) and aldophosphamide perhydrothiazine (NSC 612567), which hydrolyse spontaneously to 4-hydroxycyclophosphamide (4-OH-CP) in aqueous solution, were synthesised. These substances are prototypes of a new class of prodrugs for activated oxazaphosphorines. They were developed according to our hypothesis on the mechanism of action of oxazaphosphorine cytostatics. According to this hypothesis, toxicity and canceroselectivity are the results of phosphoramide mustard (PAM) release from 4-OH-CP catalysed by two classes of phosphodiesterase. 4-OH-CP toxicity results (a) from oxazaphosphorine-specific toxicity due to reactivity of the hemiaminal group with thiol groups of membrane proteins and (b) from PAM release catalysed by ubiquitous phosphodiesterases present in blood and tissues. Specific cytotoxicity suitable for antitumour therapy is based on specific PAM release in the vicinity of the target molecule DNA by the exonuclease subsites of DNA polymerases delta and epsilon. To unfold this specific core, which, we assume, improves efficacy in cancer treatment, low, long-lasting concentrations of OH-CP have to be guaranteed beneath the affinity range of the ubiquitous phosphodiesterase. This goal is facilitated by the rapid transfer of 4-OH-CP released from the perhyrothiazine derivative NSC 612567 to protein SH groups, as shown by protein-binding studies. Half-lives of hydrolysis and dissociation constants of the thiazolidine and perhydrothiazine derivatives, in which the reactivity of the hemiaminal group is inactivated by inclusion into the thiazolidine or perhydrothiazine ring, were determined to be 23 h and 6.0 x 10(-6) mol/l for NSC 613060 and 1.5 h and 1.1 x 10(-4) mol/l for NSC 312567. Accordingly the compounds guarantee low but long-lasting steady-state concentrations of 4-OH-CP. The acute toxicity determined in mice was 2400 mg/kg for NSC 613060 and 1900 mg/kg for NSC 612567. Except for a 30% decrease in leucocytes, daily i.p. injections of 260 mg/kg NSC 612567 (15% of LD50) were tolerated without signs of toxicity over a period of 4 weeks. In contrast, equitoxic doses of cyclophosphamide caused severe signs of toxicity, only five daily applications were tolerated. In mice treated repeatedly with NSC 613060, oxazaphosphorine toxicity was overlapped by thiazolidine toxicity. Scheduled activity tests in mice bearing P815 ascites tumour showed optimal therapeutic response when mice were treated daily. Repeated applications of 4% LD50 of NSC 613060 and 13% LD50 of NSC 612567 prevented tumour growth in mice with advanced, P388 lymphomas, implanted subcutaneously, without signs of overall toxicity to the host.