C-1748

The compound 9-(2'-hydroxyethylamino)-4-methyl-1-nitroacridine (C-1748), the promising antitumor agent developed in our laboratory was determined to undergo phase I metabolic pathways. The present studies aimed to know its biotransformation with phase II enzymes - UDP-glucuronosyltransferases (UGTs) and its potential to be engaged in drug-drug interactions arising from the modulation of UGT activity.

UGT-mediated transformations with rat liver (RLM), human liver (HLM), and human intestine (HIM) microsomes and with 10 recombinant human isoenzymes were investigated. Studies on the ability of C-1748 to inhibit UGT were performed with HLM, HT29 colorectal cancer cell homogenate and the selected recombinant UGT isoenzymes. The reactions were monitored using HPLC-UV/Vis method and the C-1748 metabolite structure was determined with ESI-TOF-MS/MS analysis.

Pseudo-molecular ion (m/z 474.1554) and the experiment with β-glucuronidase indicated that O-glucuronide of C-1748 was formed in the presence of microsomal fractions. This reaction was selectively catalyzed by UGT2B7 and 2B17. High inhibitory effect of C-1748 was shown towards isoenzyme UGT1A9 (IC₅₀ = 39.7 μM) and significant but low inhibitory potential was expressed in HT29 cell homogenate (IC₅₀ = 84.5 μM). The mixed-type inhibition mechanism (K_i = 17.0 μM; K_i '= 81.0 μM), induced by C-1748 was observed for recombinant UGT1A9 glucuronidation, whereas HT29 cell homogenate resulted in noncompetitive inhibition (K_i = 94.6 μM).

The observed UGT-mediated metabolism of C-1748 and its ability to inhibit UGT activity should be considered as the potency for drug resistance and drug-drug interactions in the prospective multidrug therapy.

Drug resistance is one of the major causes of pancreatic cancer treatment failure. Thus, it is still imperative to develop new active compounds and novel approach to improve drug efficacy. Here we present 9-amino-1-nitroacridine antitumor agent, C-1748, developed in our laboratory, as a candidate for pancreatic cancer treatment. We examined (i) the cellular response of pancreatic cancer cell lines: Panc-1, MiaPaCa-2, BxPC-3 and AsPC-1, differing in expression levels of commonly mutated genes for this cancer type, to C-1748 treatment and (ii) the role of P450 3A4 isoenzyme and cytochrome P450 reductase (CPR) in the modulation of this response. C-1748 exhibited the highest cytotoxic activity against MiaPaCa-2, while AsPC-1 cells were the most resistant (IC₅₀: 0.015, 0.075µM, respectively). A considerable amount of apoptosis was detected in Panc-1 and MiaPaCa-2 cells but only limited apoptosis was observed in AsPC-1 and BxPC-3 cells as indicated by morphological changes and biochemical markers. Furthermore, only AsPC-1 cells underwent senescence. Since AsPC-1 cells were the most resistant to C-1748 as evidenced by the lowest P450 3A4 and CPR protein levels, this cell line was subjected to transient transfection either with P450 3A4 or CPR gene. The overexpression of P450 3A4 or CPR changed the pro-apoptotic activity of C-1748 and sensitized AsPC-1 cells to this drug compared to wild-type cells. However, metabolism was changed significantly only for CPR overexpressing cells. In conclusion, the antitumor effectiveness of C-1748 would be improved by multi-drug therapy with chemotherapeutics, that are able to induce P450 3A4 and/or CPR gene expression.