Longitudinal effect of tiludronate on bone mineral density, resonant frequency, and strength in monkeys.

The effect of Tiludronate on bone was studied in 72 growing monkeys (Papio papio), 36 males and 36 females, aged 4-7 years. They were randomly allocated into four groups (18 animals per group, 9 males and 9 females): group I, controls; group II, 10 mg/kg/day; group III, 20 mg/kg/day; and group IV, 40 mg/kg/day of Tiludronate. A total of 12 animals (6 males and 6 females) in each group were sacrificed at the end of treatment (1 year) and 6 animals (3 males and 3 females) per group 1 year later. Bone mineral density (BMD) was measured by dual-photon absorptiometry. Biomechanical properties were evaluated by an impact torsion test and by resonant frequency analysis. Bone mineral measurements indicated that at the end of 1 year of treatment BMD was significantly higher, especially at the distal epiphysis of the radius, than in controls. No significant differences between groups were found in BMD 1 year after stopping treatment. Biomechanical analyses indicated that torsional stiffness increased after treatment. No differences between groups were found 1 year after stopping treatment. Results of resonant frequencies indicated an increased calculated transversal stiffness after treatment and 1 year later and an increased buckling strength 1 year after stopping treatment. In conclusion, the results on the effect of Tiludronate in growing monkeys indicate a profound effect of this drug on bone density and biomechanical properties. The biomechanical results indicate that this drug is safe, with conservation of bone strength despite a change in intrinsic mechanical properties of the bone.

Immunotoxicology assessment in the pharmaceutical industry.

Through several inter-laboratory evaluation studies, selected methods were optimized and evaluated using reference compounds in rodents, to determine their predictive value for detecting toxicity to the immune system. These provide the basis for the OECD, EPA and pending FDA Guidelines. To describe the status of immunotoxicity evaluation using these methods in the pharmaceutical industry, a survey was conducted, and is reported, of ongoing activities among the major pharmaceutical companies. The results describe which assays are performed, how compounds are selected for evaluation; and when, during the drug development process, an evaluation is performed. Finally, the strategy at Sanofi, for the evaluation and application of immunotoxicity methods during the preclinical development of new molecular entities (NMEs) is described. During the past 8 years, Sanofi has evaluated more than 27 NMEs from multiple therapeutic classes as well as four reference compounds (azathioprine, dexamethasone, cyclophosphamide and cyclosporin A). Our experience with multiple animal species (rat, dog and monkey) and immunotoxicity assays selected from the recommended tiers as well as the outcome from the evaluation of our NMEs and reference standards, is described. This experience has led us to believe that immunotoxicology parameters represent an important adjunct for the safety assessment of NMEs. In addition, these methods were easily integrated into the drug development process and yielded an unexpectedly low frequency of positive results. In summary, immunotoxicity can be evaluated on a case-by-case basis driven by pathology or clinical hematology findings, by the drug's indication, the chemical class or indication of the NME evaluated (for example, anti-viral agents), or systematically performed.

Studies on the chronic phase of adjuvant arthritis: effect of SR 41319, a new diphosphonate.

We studied the course of adjuvant arthritis in rats by measuring clinical, biochemical, and histological parameters on day 36 after induction (representing the secondary reaction) and on day 171, which is at the stage of permanent deformity. The effect of SR 41319, a new diphosphonate, was evaluated on days 36 and 171, after three weeks of treatment (days 14-35 inclusive). In the absence of treatment all the measured parameters were markedly abnormal on day 36, indicating the presence of lesions that were still evolving. On day 171 clinical parameters and the lesion histological index remained the same, whereas the biochemical parameters and disease activity histological index had returned to normal, indicating that the lesions at this stage although severe were not inflammatory and consequently not progressing. SR 41319 treatment reduced the severity and progression of the disease both on day 36 and on day 171. We conclude that SR 41319 may be a potentially useful drug for the treatment of rheumatoid arthritis.

Neurobehavioral effects of D-glaucine in rats.

Adult, male Fischer-344 rats were dosed by gavage with 75 or 150 mg/kg of D-glaucine for six weeks. A battery of neurobehavioral tests was given prior to dosing, after three and six weeks of dosing and three and five weeks after cessation of dosing. Routine histopathological assessment was made five weeks after cessation of exposure. Animals receiving the high dose of glaucine showed a transient decrease in body weight, decreased motor activity after three weeks of dosing, and decreased grip strength after three and six weeks of dosing. The lower dose of glaucine decreased forelimb grip strength after six weeks of dosing. Glaucine had no effects on other measures of motor function (negative geotaxis, hindlimb splay) or reactivity to noxious (hot plate, tail flick) or non-noxious stimuli (sound or air puff). By five weeks postdosing, the neurobehavioral functioning of glaucine-exposed rats was not different than controls. Histopathological examination revealed a brown discoloration of the thyroid, brain, and muscles and the appearance of brown pigments in the cell bodies of neurons located in the brain stem and spinal cord.

Lack of initiating or promoting activity of six benzodiazepine tranquilizers in rat liver limited bioassays monitored by histopathology and assay of liver and plasma enzymes.

Six benzodiazepine tranquilizers were tested in limited in vivo bioassays for their ability to initiate or promote the development of preneoplastic and neoplastic rat liver lesions. The benzodiazepine produced no liver altered hepatocellular foci during a 14-week period of administration whereas a large number were produced by the liver carcinogen, N-2-fluorenylacetamide. To assay for promoting activity and confirm the lack of initiating activity, N-2-fluorenylacetamide was used to produce altered foci and early neoplastic nodules in rat liver by 8 weeks of dietary administration and the benzodiazepines were then administered for 12 weeks. The liver neoplasm promoter phenobarbital had a substantial enhancing effect upon the persistence of early lesions but none of the benzodiazepines showed a similar effect. Thus in these limited bioassays monitored by histopathology, the benzodiazepine tranquilizers failed to exhibit either an initiating or a promoting action. In these studies, the liver and plasma enzymes, glutamate-pyruvate transaminase, glutamate-oxalacetic transaminase, lactic dehydrogenase, alkaline phosphatases, and gamma-glutamyltranspeptidase were monitored to determine if any alterations correlated with liver pathological changes. gamma-Glutamyltranspeptidase activity in both liver and plasma was markedly increased during initiation by N-2-fluorenylacetamide. Following cessation of carcinogen exposure, gamma-glutamyltranspeptidase remained elevated, providing an indication of past initiation. Administration of phenobarbital after N-2-fluorenylacetamide resulted in an elevation of liver and plasma gamma-glutamyltranspeptidase, but none of the benzodiazepines produced this effect and thus no biochemical evidence of a promoting effect on the liver was observed. Correlations between liver and plasma gamma-glutamyltranspeptidase and the occurrence of foci were excellent, indicating that determination of plasma activity can be used as an index of the process of hepatocarcinogenesis.

Limited in vivo bioassays on some benzodiazepines: lack of experimental initiating or promoting effect of the benzodiazepine tranquillizers diazepam, clorazepate, oxazepam and lorazepam.

Four benzodiazepine tranquillizers were tested for their ability to initiate or promote the development of preneoplastic and neoplastic rat liver lesions. In comparison with the liver carcinogen, N-2-fluorenylacetamide, the benzodiazepines exhibited no initiating activity during a 14-week period of daily administration by gavage. To study the promoting activity, N-2-fluorenylacetamide was used to initiate altered foci and neoplastic nodules in rat liver during 8 weeks and then the benzodiazepines were administered by daily gavage for a period of 12 weeks. The liver tumor promoter phenobarbital had a substantial enhancing effect upon the persistence of nodules but none of the benzodiazepines showed a similar effect. Thus, in the process model systems used, to detect initiating or promoting potential effect, the benzodiazepine tranquillizers failed to exhibit either an initiating or a promoting action.

Toxicological studies on a benzofuran derivative. III. Comparison of peroxisome proliferation in rat and human hepatocytes in primary culture.

Primary cultures of rat and human hepatocytes were used in our in vitro studies for investigating species differences in the response to a peroxisome proliferating benzofuran derivative, benzbromarone. Cyanide-insensitive palmitoyl coenzyme A oxidation (a marker of peroxisome fatty acid beta-oxidation) and electron microscopy were used to assess peroxisome proliferation. Hepatocytes were cultured essentially as described by Mitchell et al. (1984, Arch. Toxicol. 55, 239-246); clofibric acid and mono(2-ethylhexyl) phthalate (MEHP) were used as reference compounds, as they are well known to cause peroxisome proliferation in rat hepatocytes in primary culture. The benzofuran derivative, tested at drug concentrations ranging from 2.37 to 59.20 microM in rat hepatocyte primary cultures, induced, after 96 hr, a dose-related increase of the peroxisomal beta-oxidase activity correlated with an increased number of peroxisomes; this increase was much less marked than that obtained with clofibric acid or MEHP. By contrast, using the same range of concentrations, human hepatocytes in primary culture treated with benzbromarone revealed no enhancement of enzymatic activity and no concomitant statistically significant increase in the number of peroxisomes; the same observations were reported with clofibric acid and MEHP. These results demonstrate clearly that species differences in sensitivity to peroxisome proliferation with the benzofuran derivative do exist.

Recovery from amiodarone-induced lipidosis in laboratory animals: a toxicological study.

Numerous amphiphilic cationic drugs cause lipid-lysosomal storage in animal tissues; one of these drugs is amiodarone, a major antiarrhythmic agent. The toxicological effects of amiodarone were studied in three animal species (rats, dogs, and monkeys). It was shown that sublethal dose levels of amiodarone induced lipid storage in a great variety of tissues in rats (Fischer and Sprague-Dawley strains) and dogs. However, this change was not observed in baboons and Wistar rats. This storage, essentially characterized by lamellated inclusions, affected foamy macrophages, and at a later phase multiple cell types. Tissue biochemical analysis provided evidence of the phospholipidic nature of the storage. In addition, amiodarone induced an increased cholesterolemia and marked modifications of the lipoproteinogram. The kinetics of lipid storage was demonstrated following oral administration of amiodarone. After jejunal absorption, lipid storage occurred in the mesenteric lymph nodes followed by widespread deposition in the other lymph nodes and tissues, particularly in the lung. A complete recovery from lipid storage as observed in dogs and rats. Finally, an investigation of a correlation between animal and man by means of long-term experiments is proposed.

Intestinal pathology in the dog induced by sublethal doses of amiodarone.

Amiodarone (A), an unique antiarrhythmic agent and amphiphilic drug, induces at sublethal doses dyslipidic storage in animals. The present work demonstrates a distinct intestinal pathology or "Malabsorption Syndrome" in the dog induced by A. Signs of intestinal pathology were observed in all animals receiving 100 mg/kg, but not in those receiving less than 50 mg/kg, after one month. The malabsorption syndrome was demonstrated by a dynamic study of lipid absorption and pathological lesions (partial villous atrophy and the accumulation of macrophages with dyslipidic inclusions.