Pig-a gene mutation assay study design: critical assessment of 3- versus 28-day repeat-dose treatment schedules.

The in vivo Pig-a assay is being used in safety studies to evaluate the potential of chemicals to induce somatic cell gene mutations. Ongoing work is aimed at developing an Organisation for Economic Cooperation and Development (OECD) test guideline to support routine use for regulatory purposes (OECD project number 4.93). Among the details that will need to be articulated in an eventual guideline are recommended treatment and harvest schedules. With this in mind, experiments reported herein were performed with Wistar Han rats exposed to aristolochic acid I (AA), 1,3-propane sultone, chlorambucil, thiotepa or melphalan using each of two commonly used treatment schedules: 3 or 28 consecutive days. In the case of the 3-day studies, blood was collected for Pig-a analysis on days 15 or 16 and 29 or 30. For the 28-day studies blood was collected on day 29 or 30. The effect of treatment on mutant reticulocytes and mutant erythrocytes was evaluated with parametric pair-wise tests. While each of the five mutagens increased mutant phenotype cell frequencies irrespective of study design, statistical significance was consistently achieved at lower dose levels when the 28-day format was used (e.g. 2.75 vs 20 mg/kg/bw for AA). To more thoroughly investigate the dose-response relationships, benchmark dose (BMD) analyses were performed with PROAST software. These results corroborate the pair-wise testing results in that lower BMD values were obtained with the 28-day design. Finally, mutagenic potency, as measured by BMD analyses, most consistently correlated with the mutagens' tumorigenic dose 50 values when the lengthier treatment schedule was used. Collectively, these results suggest that both 3- and 28-day treatment schedules have merit in hazard identification-type studies. That being said, for the purpose of regulatory safety assessments, there are clear advantages to study designs that utilise protracted exposures.

In vitro and in vivo assessment of the genotoxic effects of ceric ammonium nitrate and 1,3-propane sultone.

A variety of methods have been developed for accurate and systematic evaluation of chemical genotoxicity. Ceric ammonium nitrate (CAN) and 1,3-propane sultone (1,3-PS) have been extensively applied in industrial fields. Although 1,3-PS, but not CAN, has been reported as a potent carcinogen, systematic assessment of the genotoxic properties of these chemicals has not been conducted. The purpose of this study was to establish a decision tree for evaluating genotoxicity based on the good laboratory practices (GLP) system using 1,3-PS and CAN as test chemicals. In vitro studies were performed including the bacterial reverse mutation assay, chromosomal aberration assay, and micronucleus assay. We conducted in vivo studies using a combined micronucleus and alkaline comet (MN-CMT) assay and the Pig-a gene mutation assay, which is a promising method for detecting gene mutations in vivo. CAN showed negative responses in all in vitro genotoxicity assays and the in vivo combined MN-CMT assay. Meanwhile, 1,3-PS had positive results in all in vitro and in vivo genotoxicity assays. In this study, we confirmed the genotoxicity of 1,3-PS and CAN using both in vitro and in vivo assays. We propose a decision tree for evaluating chemical-induced genotoxicity.

Non-clinical safety evaluation and risk assessment to human of aleglitazar, a dual PPAR α/γ agonist, and its major human metabolite.

The non-clinical safety profile of aleglitazar, a peroxisome proliferator activated receptor alpha/gamma agonist, and its major human metabolite M6 was studied in a complete package consisting of drug metabolism and pharmacokinetics characterization, safety pharmacology, genotoxicity, repeat dose toxicity, reproductive toxicity and carcinogenicity studies. These studies identified the following main targets similar to other PPAR agonists: red blood cell parameters, liver, heart, kidney, ovaries, testes, bone marrow, adipose tissue, and fluid accumulation. Additionally, and in the 12-month monkey study only, an increased incidence of generalized hair loss/thinning was observed in all groups including controls. In the rat carcinogenicity study there was no statistically significant increase in tumors. In the mouse carcinogenicity study, there was an increased incidence of angiomatous tumors and there were three males with gallbladder adenoma. No relevant compound-related effects were observed in safety pharmacology, genotoxicity, and a 28-day immunotoxicity rat study. Effects observed in reproductive toxicity studies were similar to those known for other PPARγ agonists. Separate studies with the human metabolite M6 did not reveal findings that would prevent human dosing. Overall, the results from the non-clinical safety studies conducted with aleglitazar and the human metabolite M6 were considered to support the clinical Phase 3 program.

Developmental toxicity assessment of the new turf herbicide, methiozolin ([5-(2,6-difluorobenzyl)oxymethyl-5-methyl-3,3(3-methylthiophen-2-yl)-1,2-isoxazoline]), in rabbits.

Methiozolin is a new herbicide to control annual bluegrass (Poa annua L.) and large crabgrass (Digitaria sanguinalis (L.) Scop.) in various turfgrasses. The potential of methiozolin to induce maternal and developmental toxicity was investigated in the pregnant New Zealand White Rabbits. Methiozolin was, at dose levels of 0, 125, 250 and 500 mg/kg/day, administered by oral gavage to artificially inseminated rabbits (25 females per group) from days 6 to 28 of gestation. All does were subjected to Cesarean section on day 29 of gestation. At 500 mg/kg/day, treatment-related toxicities including abortion (10/22), decreased mean body weight, weight gain, net body weight change, reduced food consumption and decreased fetal weight were observed. At 125 and 250 mg/kg/day, no signs of maternal and developmental toxicity were observed. There were no treatment-related external, visceral and skeletal abnormalities of fetuses at all doses tested. In the current experimental conditions, the no observed adverse effect levels (NOAELs) of methiozolin are considered to be 250 mg/kg/day for does and prenatal development.

An Internet snapshot study to compare the international availability of the novel psychoactive substance methiopropamine.

CONTEXT: With the increased use of novel psychoactive substances, there is an increasing availability of these substances from Internet-based suppliers. Methiopropamine, first reported in 2011, is a recreational drug available over the Internet. The aim of this study was to investigate availability and cost of methiopropamine in three different countries: the UK, France, and Canada. METHODS: Using the European Monitoring Centre for Drugs and Drug Addiction Internet snapshot methodology, this study, conducted in June 2013, was undertaken in two different languages: in English (the UK and Canada) and in French (France and Canada), using three Internet searching engines: " google.co.uk ", " google.fr " and " google.ca ". RESULTS: A total of 62 sites were found, most of them were found from the English searches. 45% of the suppliers seemed to originate from the UK. The prices of methiopropamine were comparable between suppliers, no matter which search engine or language was used. The cost of a unit of methiopropamine was inversely related to the purchased quantity, going from 19.49 ± 0.15 GBP per gram for a purchase amount of 500 mg to 3.54 ± 0.13 GBP per gram for a purchase amount of 1 kg. DISCUSSION: The results of the present study demonstrate that the sale of methiopropamine has the potential to reach users across the world. It also appears to support that snapshot studies could be used for toxicovigilance across different countries, by studying the Internet market of novel psychoactive substances. CONCLUSION: To date, snapshot studies, used to monitor the Internet novel psychoactive substances market, have only been undertaken in Europe. We have shown that the flexibility of this methodology enables comparison of the online activity of drug sellers between different countries and continents and that, at least for methiopropamine, the UK is the predominant source for Internet supply.

Assessment of the genotoxic and carcinogenic potentials of 3-aminothiophene derivatives using in vitro and in silico methodologies.

Thiophene derivatives, a class of compounds widely used in products such as pharmaceuticals, agrochemicals or dyestuffs, represent chemicals of concern. Indeed, the thiophene ring is often considered as a structural moiety that may be involved in toxic effects in humans. We primarily focus on the genotoxic/mutagenic and carcinogenic potentials of the methyl 3-amino-4-methylthiophene-2-carboxylate (1), a precursor of the articaine local anesthetic (4) which falls within the scope of the European REACH (Registration, Evaluation, Authorisation and restriction of CHemicals) legislation. To discern some structure-toxicity relationships, we also studied two related compounds, namely the 3-amino 4-methylthiophene (2) and the 2-acetyl 4-chlorothiophene (3). Techniques employed to assess mutagenic and DNA-damaging effects involved the Salmonella mutagenicity assay (or Ames test) and the single-cell gel electrophoresis assay (or Comet assay). In the range of tested doses, none of these derivatives led to a positive response in the Ames tests and DNA damage was only observed in the Comet assay after high concentration exposure of 2. The study of their carcinogenic potential using the in vitro SHE (Syrian Hamster Embryo) cell transformation assay (CTA) highlighted the activity of compound 2. A combination of experimental data with in silico predictions of the reactivity of thiophene derivatives towards cytochrome P450 (CYP450), enabled us to hypothesize possible pathways leading to these toxicological profiles.

Preclinical assessment of gastrooesophageal tolerance of the new antiosteoporotic drug strontium ranelate: an endoscopic study in monkeys.

This study was aimed at evaluating the digestive tolerance of the new antiosteoporotic drug, strontium ranelate, and to compare it to that of another strontium salt, strontium chloride (SrCl2). Strontium ranelate, SrCl2, or placebo were administered orally (capsules) to 3 groups of 2 male and 2 female cynomolgus monkeys (Macaca fascicularis) once a day for 7 days at a dose of 2 g/day, which is the recommended therapeutic dose in man. Endoscopic examination of the oesophagus, the stomach and the first part of the duodenum was performed on fasted animals approximately 3 hr after the first (Day 1) and last dosing (Day 7), and, on Day 8 and Day 14 in case of lesions on Day 7. Strontium ranelate did not induce any acute or subchronic toxic effect on the gastric mucosa, the oesophagus and the first part of the duodenum. On the contrary, acute and superficial damages were noted on all animals receiving SrCl2 such as haemorrhagic and erosive lesions (formation of an ulcer in one male and a marked congestive antritis in one female). These effects were reversible after cessation of treatment. The microscopic examination of biopsies sampled at the site of gastric lesions revealed moderate granulocyte infiltration, indicating a local irritating origin of the lesions. Strontium ranelate by oral route is safe for the gastric mucosa while SrCl2 induced superficial and reversible lesions.