Bernard Leblanc

Characterization of the arteritis induced by infusion of rats with UK-61,260, an inodilator, for 24 h. A comparison with the arteritis induced by fenoldopam mesylate.

Administration of fenoldopam mesylate (FM), a dopaminergic agonist, or of cyclic cAMP phosphodiesterase inhibitors (PDE III), for example theophylline and caffeine, induces arteritis in the rat. In this study we characterized the arteritis induced by UK-61,260, an investigational inotropic agent with vasodilatory properties which displays an inhibitory action on cyclic AMP phosphodiesterase, in comparison with lesions induced by FM. The compounds were administered to Sprague-Dawley rats by intravenous infusion over 24 h (FM and UK-61,260), orally or subcutaneously (UK-61,260); the rats were killed and necropsied for pathological examination at various times between 0 h and 28 days post-infusion. Infusion of UK-61,260 at doses of 100, 300 or 400 mg/kg produced arteritis mainly in the mesenteric arteries and occasionally in the renal, pancreatic, gastric and coronary arteries. There were no arterial lesions after infusion of 30 mg/kg, or after administration of 30, 100 or 200 mg/kg per day subcutaneously for 7 days, or after acute administration of 100, 300, 400 or 600 mg/kg orally. Infusion of rats with 72 or 144 mg/kg FM produced arteritis over a wider range of tissues than did UK-61,260. However, the arterial lesions produced by infusion of either drug have the same initial aspect and a similar evolution with time. Immediately after the end of the infusion, minimal necrosis and haemorrhage occurred in the media only, without involvement of the endothelium or the perivascular space. This indicates that the media of the artery is the primary site of injury. The lesions seen 1 and 3 days post-infusion were characterized by severe medial necrosis and haemorrhage with perivas cular acute inflammation and appeared macroscopically as haemorrhagic spots on the vessels. On days 7, 14 and 28 post-infusion, no medial necrosis or haemorrhage were present, while perivascular chronic inflammation and moderate smooth muscle hyperplasia were seen. It appeared therefore, that the lesions underwent repair in 28 days, but footprints of the damage were still present 28 days post-infusion. The similarity between arteritis induced in rats by fenoldopam or by UK-61,260, at doses inducing PDE III inhibition, is consistent with the view that they have a similar pathogenesis. In our view it is probable that these pharmacologically and chemically distinct drugs trigger an increase in intracellular levels of cAMP which in turn triggers vascular damage. The arterial changes observed in the current study after acute administration may explain the increased incidence of polyarteritis nodosa occurring in long term toxicity studies with FM or PDE III inhibitors.

Nucleolar organizer regions in cardiac lesions induced by doxorubicin.

The use of the argyrophilic (Ag) staining technique for nucleolar organizer regions (NORs) revealed nuclear changes in myocytes of the left atrium of 10 rats treated twice a week for 6 weeks with doxorubicin (1 mg/kg body weight) iv and sacrificed after 6 weeks without treatment. The changes were easily detected qualitatively and further assessed by quantification. Cardiac myocytes of doxorubicin-treated rats had larger nuclei and/or a larger quantity of AgNORs that were either dispersed in a number of small dots or clustered in rounded, rod-shaped, or tortuous large structures. AgNOR alterations may reflect a defect of nucleolar association leading to an impairment of protein synthesis that could be involved in doxorubicin cardiotoxicity.

Hyperplastic Gastritis with Intraepithelial Campylobacter-like Organisms in a Beagle Dog

Chronic hypertrophic gastritis, proliferative gastritis, or hyperplastic gastritis are generic terms in dogs for rare conditions characterized by a marked thickening of gastric rugae due to mucosal hyperplasia. The lesions may predominantly involve the mucosa of the body of the stomach, as in Menetrier’s disease in human beings,14 or the antral mucosa, as the name antral pyloric hypertrophy syndrome implies4 Similar gastric lesions have been seen as isolated findings, in Zollinger-Ellison syndrome, as part of the gastrointestinal disease affecting Basenji dogs and dogs with mast cell tumors.’ The causes are unknown; however, immune or hormonal disorders, environmental factors, and genetic predispositions may be involved in the pathogenesis.

Acceptability of Low Levels of Genotoxic Impurities in New Drug Substances

The Safety Working Party (SWP) of the European Committee for Proprietary Medicinal Products (CPMP) published a draft “Position paper on the limits for genotoxic impurities” in December 2002. Genotoxic impurities was a topic selected for the joint Drug Information Association (DIA)/European Medicines Agency (EMEA) meeting that was organised in London on October 27–28, 2003, to facilitate the exchange of opinion and perspective between industry and regulatory scientists. Scientific and regulatory updates were presented and discussed in the light of case studies, which are described in this article. The four cases span a range of different scenarios that can be encountered in development: (i) candidate for life-threatening indication — an alkylating reagent used in synthesis is an impurity in the active substance; (ii) late-stage candidate for non-life-threatening chronic indication — a route change leads to a new intermediate becoming a potential impurity — as it is an isolated intermediate, worker safety data is generated and needs to be risk managed; (iii) late-stage candidate for non-life-threatening chronic indication — a mutagenic and structural-alerting starting material — the commercial route confers excellent purging; and (iv) early-stage candidate for non-life-threatening chronic indication — considers strategic approaches for impurities with structural-alerting functionality under different scenarios (dependent upon toxicological data available, daily dosing regimen, route of delivery etc.).The outcomes of the discussions of the cases at the DIA/EMEA Workshop are presented in a separate article in this issue of the journal.

Acceptability of Low Levels of Genotoxic Impurities in New Drug Substances: Case Reports

The Safety Working Party (SWP) of the European Committee for Proprietary Medicinal Products (CPMP) published a draft Position paper on the limits for genotoxic impurities in December 2002. Genotoxic impurities was a topic selected for the joint Drug Information Association (DIA)/European Medicines Agency (EMEA) meeting that was organised in London on October 27-28, 2003, to facilitate the exchange of opinion and perspective between industry and regulatory scientists. Scientific and regulatory updates were presented and discussed in the light of case studies, which are described in this article. The four cases span a range of different scenarios that can be encountered in development: (i) candidate for life-threatening indication - an alkylating reagent used in synthesis is an impurity in the active substance; (ii) late-stage candidate for non-life-threatening chronic indication - a route change leads to a new intermediate becoming a potential impurity - as it is an isolated intermediate, worker safety data is generated and needs to be risk managed; (iii) late-stage candidate for non-life-threatening chronic indication - a mutagenic and structural-alerting starting material - the commercial route confers excellent purging; and (iv) early-stage candidate for non-life-threatening chronic indication - considers strategic approaches for impurities with structural-alerting functionality under different scenarios (dependent upon toxicological data available, daily dosing regimen, route of delivery etc.). The outcomes of the discussions of the cases at the DIA/EMEA Workshop are presented in a separate article in this issue of the journal.

Panel Discussion: Alternative Mouse Models for Carcinogenicity Assessment

This article summarizes key points from Dr. Bernard Leblanc’s presentation European Perspectives on Alternative Mouse Carcinogenicity Models and a distillation of questions and answers from a panel discussion following presentations on Alternative Mouse Models for Carcinogenicity Assessment at the Society of Toxicologic Pathology’s annual symposium on June 23, 2009, in Washington, DC.