DNA-Targeted 1,2,4-Benzotriazine 1,4-Dioxides: Potent Analogues of the Hypoxia-Selective Cytotoxin Tirapazamine

Stanford University, Palo Alto, California, United States
Journal of Medicinal Chemistry (Impact Factor: 5.45). 02/2004; 47(2):475-88. DOI: 10.1021/jm030399c
Source: PubMed


Tirapazamine (TPZ, 1,2,4-benzotriazin-3-amine 1,4-dioxide) is a bioreductive hypoxia-selective cytotoxin, currently in phase II/III clinical trials in combination with radiotherapy and with cisplatin-based chemotherapy. We have prepared a series of 1,2,4-benzotriazine 1,4-dioxide (BTO) analogues of TPZ where a DNA-targeting chromophore is attached at the 3-position via a flexible linker. DNA binding affinity was modified through variation of the chromophore or the pK(a) of the linker chain. The association constants (K-DNA) for calf thymus DNA ranged from 1 x 10(2) to 5.6 x 10(5) M-1 (ionic strength of 0.01 M). DNA binding affinity was dependent on the presence of a positive charge, either in the linker chain or in the chromophore, and (for a series of 4-acridine carboxamide chromophore analogues) correlated strongly with linker chain pKa. The efficacy of these BTOs in killing aerobic and hypoxic mouse SCCVII tumor cells in vitro was determined by clonogenic survival. Cytotoxicity was measured as the concentration required to reduce plating efficiency to 10% of controls (C-10), and the hypoxic cytotoxicity ratio (HCR) for each BTO was calculated as C-10(aerobic)/C-10(hypoxic). BTOs bearing a positive charge showed increased hypoxic cytotoxicity (1.5-56-fold) compared to TPZ and mostly modest HCRs (8-51), but some excellent (> 167 and 400) values. There was a strong correlation between K-DNA and hypoxic cytotoxicity but no correlation between K-DNA and HCR. Cytotoxicity in HT-29 human colon carcinoma cells, determined using IC50 assays, showed similar relationships with a correlation between KDNA and hypoxic cytotoxicity but no correlation between KDNA and HCR. In this cell line, a higher proportion of compounds (7 of 11) had HCRs greater than or equal to that of TPZ. The data confirm that DNA targeting is a useful concept for increasing potency while maintaining hypoxic selectivity and provide a direction for the further development of DNA-targeted analogues of TPZ.

Download full-text


Available from: Michael P Hay, Jun 23, 2015
  • Source
    • "The synthesis of compounds 6aew and 7aec is shown in Scheme 1. First, compounds 3aee were obtained from the Ullmann reaction of 2,4-dichlorobenzoic acid 2 with anthranilic acid 1a or its derivatives 1bee in DMF using Cu as the catalyst [16] [17]. Subsequent FriedeleCrafts acylation was carried out in concentrated sulfuric acid at 80 C for 5 h to give acridone-4-carboxylic acid derivatives 4aee in high yields [36], which were then reacted with the corresponding primary aliphatic amines using N,N 0 -carbonyldiimidazole (CDI) as the condensation agent [37] to afford the Fig. 1. The structures of C-1311, DACA, PZA, BRACO-19 and m-AMSA as typical acridine/acridone derivatives. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A series of novel pyridyl acridone derivatives comprised of a pseudo-five-cyclic system to extend the π-conjugated acridone chromophore, were designed and synthesized as potent DNA binding antitumor compounds. Most synthesized compounds displayed good activity against human leukemia K562 cells in MTT tests, with compound 6d exhibiting the highest activity with IC50 value at 0.46 μM. Moreover, 6d showed potent activities against solid tumor cell lines (0.16-3.79 μM). Several experimental studies demonstrated that the antitumor mode of action of compound 6d involves DNA intercalation, topoisomerase I inhibition, and apoptosis induction through the mitochondrial pathway. In summary, compound 6d represents a novel and promising lead structure for the development of new potent anticancer DNA-binding agents. Copyright © 2015 Elsevier Masson SAS. All rights reserved.
    Full-text · Article · Mar 2015 · European Journal of Medicinal Chemistry
  • Source
    • "P-450 reductase plays an important role in the reductive activation of the bioreductive drug, e.g. tirapazamine (Paterson et al. 1995; Hay et al. 2004; Siim et al. 2004). Tirapazamine is an antitumour agent with a high selective toxicity against hypoxic cells, which are resistant to ionizing radiation (Moulder & Rockwell 1987) and also to some chemotherapeutic agents (Kennedy 1987). "
    [Show abstract] [Hide abstract]
    ABSTRACT: NADPH-cytochrome P-450 reductase (P-450 reductase) plays a crucial role in the metabolism of many endogenic compounds and xenobiotics detoxication. The enzyme is also involved in the toxicity of some clinically important antitumour drugs (doxorubicin) and pesticides (paraquat). P-450 reductase activates them to their more toxic metabolites via one electron reduction which triggers free radical cascade. In some cases however, such transformation is essential to produce therapeutic effect in anticancer drugs. The main purpose of the paper was to evaluate the effect of three natural compounds found in human diet: (-)-epigallocatechin gallate (EGCG), quercetin and resveratrol on P-450 reductase activity. The activity of the enzyme was determined spectrophotometrically by measurement of the rate of cytochrome c reduction at 550 nm, in vitro, using human heart, liver and lung microsomes. It was found that quercetin increased the P-450 reductase activity in human organs at all tested doses. The activity of microcosms in all organs was enhanced according to the concentrations of quercetin, which increased the activity in the order lung>heart>liver. Addition of EGCG to the reaction mixture enhanced the P-450 reductase activity in the following order: liver>heart>lung. However, no significant effect of resveratrol on P-450 reductase activity was observed. It seems that the presence of quercetin and EGCG in the diet may increase P-450 reductase activity during doxorubicin therapy with subsequent increased risk of toxicity. A beneficial effect may be obtained in anticancer therapy with bioreductive agents like tirapazamine.
    Full-text · Article · Aug 2005 · Basic & Clinical Pharmacology & Toxicology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tirapazamine (3-amine-1,2,4-benzotriazine-1,4-dioxide, SR4233, WIN 59075, TPZ) is a perfect prodrug to fight against hypoxic tumor cells. Analogues of tirapazamine show better activity when they have a better lipophilicity and an adapted one-electron reduction potential. Using this knowledge, we have synthesized novel molecules derived from tirapazamine. We have also tried to know what kinds of effect are generated by the presence of a basic amino group.
    No preview · Article ·
Show more