1Heterocyclic amines are formed in parts per billion levels when meat is cooked. 2The heterocyclic amines MeIQx and PhIP are efficiently absorbed into the systemic circulation after ingestion of cooked food. 3We have shown that MeIQx and PhIP, both in vitro and in vivo, are substrates for human hepatic CYP1A2, which exclusively and efficiently catalyses their conversion to genotoxic hydroxylamines. 4MeIQx and PhIP are promutagens. MeIQx is a very powerful bacterial mutagen whereas PhIP is a more potent mammalian cell mutagen. Using a mammalian cell target gene, hprt, we have shown that PhIP induces a characteristic mutational ‘fingerprint’. 5MeIQx and PhIP are carcinogenic in bioassays. The PhIP mutational ‘fingerprint’ has been detected in the Apc gene of 5/8 colonic tumours induced by PhIP in rats.

ABSTRACT:The value of cynomolgus and rhesus monkeys to predict human pharmacokinetic parameters has been well established in recent years. However, practical limitations on cost and accessibility can often be a deterrent to obtain data in these valuable species, and the characterization of the predictive power of other nonhuman primates would be useful. Therefore, the present investigation was designed to evaluate the pharmacokinetics of a test set of marketed compounds in the African green monkey, to compare the pharmacokinetics of these agents between nonhuman primate species, and to validate the ability of the African green monkey to predict human pharmacokinetics. Intravenous pharmacokinetics were evaluated for 11 test compounds in this study and compared with data from rats, dogs, cynomolgus/rhesus monkeys, and humans. The results from this investigation indicate that African green monkeys deliver reasonable prediction of human clearance and mean residence time and volume of distribution, although somewhat less accurately than cynomolgus and rhesus monkeys, particularly for volume of distribution, potentially because of body size or composition or experimental design differences. Furthermore, use of an optimized clearance prediction algorithm from the literature enhanced predictivity over a simple liver blood flowbased extrapolation methodology. The data from this study show that African green monkeys have the potential to be used as a surrogate for cynomolgus or rhesus monkeys in preclinical pharmacokinetic studies, particularly for the study of clearance processes, and should be considered as an alternate nonhuman primate test species.

A conventional, rapid and high throughput method for tissue extraction and accurate and selective LC-MS/MS quantification of 2′-C-methylguanosine triphosphate (2′-MeGTP) in mouse liver was developed and qualified. Trichloroacetic acid (TCA) was used as the tissue homogenization reagent that overcomes instability challenges of liver tissue nucleotide triphosphates due to instant ischemic degradation to mono-and diphosphate nucleotides. Degradation of 2′-MeGTP was also minimized by harvesting livers using in situ clamp-freezing or snap-freezing techniques. The assay also included a sample clean-up procedure using weak anion exchange solid phase extraction followed by ion exchange chromatography and tandem mass spectrometry detection. The linear assay range was from 50 to 10000 pmol/mL concentration in liver homogenate (250-50000 pmol/g in liver tissue). The method was qualified over three intraday batches for accuracy, precision, selectivity and specificity. The assay was successfully applied to pharmacokinetic studies of 2′-MeGTP in liver tissue samples after single oral doses of IDX184, a nucleotide prodrug inhibitor of the viral polymerase for the treatment of hepatitis C, to mice. The study results suggested that the clamp-freezing liver collection method was marginally more effective in preventing 2′-MeGTP degradation during liver tissue collection compared to the snap-freezing method.Key words LC-MS/MS; nucleotide; liver tissue analysis; 2′-C-methylguanosine triphosphate; hepatitis C Hepatitis C virus (HCV) infection is an important global healthcare concern with approximately 150 million individuals infected worldwide and an estimated 4 million newly infected patients added each year.1-3) For many years, pegylated α-interferon in combination with ribavirin (PegIFN/RBV) was the standard of care therapy for HCV patients. This combination therapy boosts patient's immune response against the HCV infection to achieve a sustained virologic response (SVR). [4][5][6] In 2011, protease inhibitors were the first directacting antivirals (DAAs) introduced in combination with PegIFN/RBV, resulting in increased SVR rates and shorter duration of therapy for the majority of HCV patients. 7)The development of nucleoside and nucleotide analogue molecules have also been key to the evolution of HCV treatment as inhibitors of the important viral replication step catalyzed by HCV NS5B RNA polymerase. [8][9][10][11][12] For this class of compounds, the active entity is nucleoside triphosphate (NTP). The NTPs have poor cellular uptake and they undergo rapid enzymatic degradation. The conversion of a nucleoside to its monophosphate is a rate limiting first step towards the formation of the active NTP. To overcome these difficulties prodrug versions of these molecules have been developed to deliver and target nucleosides to the liver for HCV and address bioavailability and stability issues. [7][8][9]11,13,14) 2′-C-Methylguanosine triphosphate or 2′-MeGTP is a nucleotide analog which effectively disrupts RNA formation by the viral po...

African green monkeys (vervets) have been proposed as an alternate species that might allow improved access and provide high-quality pharmacokinetic results comparable with other primates. However, no oral data are available in vervets to evaluate cross-species predictive performance. Therefore, this study was conducted to evaluate the use of the vervet to predict human oral pharmacokinetics and drug interactions. Oral pharmacokinetic studies were conducted in the vervet for eight compounds: phenytoin, moxifloxacin, erythromycin, lidocaine, propranolol, ciprofloxacin, metroprolol, and prednisolone. To assess drug-drug interactions, co-administration experiments were conducted with ketoconazole and either propranolol or erythromycin. In general, the vervet provided similar predictivity for human oral exposure as cynomolgus or rhesus monkeys. In all non-human primates, human exposure to phenytoin would be over-predicted, and erythromycin, lidocaine, and propranolol under-predicted, with good predictivity for the other compounds studied. Furthermore, in the vervet, ketoconazole co-administration resulted in a six-fold increase in exposure to erythromycin, demonstrating proof of concept for drug-drug interaction screening. These data support further exploration of the vervet as an alternate primate species for use in preclinical pharmacokinetic screening.