Kazuhiro Shimomura

Historical control data on prenatal developmental toxicity studies in rabbits

Historical control data on rabbit prenatal developmental toxicity studies, performed between 1994–2010, were obtained from 20 laboratories, including 11 pharmaceutical and chemical companies and nine contract laboratories, in Japan. In this paper, data were incorporated from a laboratory if the information was based on 10 studies or more. Japanese White rabbits and New Zealand White rabbits were used for prenatal developmental toxicity studies. The data included maternal reproductive findings at terminal cesarean sections and fetal findings including spontaneous incidences of morphological alterations. No noticeable differences between strains or laboratories were observed in the maternal reproductive and fetal developmental data. The inter‐laboratory variations in the incidences of fetal external, visceral, and skeletal alterations seem to be due to differences in the selection of observation parameters, observation criteria, and classification of the findings, and terminology of fetal alterations.

The value of juvenile animal studies: a Japanese industry perspective.

Pharmaceuticals have been used on adults and children; however, they were previously investigated only by adult human clinical studies and adult animal nonclinical studies. The US FDA finalized the guidance of juvenile animal toxicity studies in 2006, and EMEA was finalized in 2008. At that point, juvenile animal toxicity studies were encouraged to investigate the safety of the pediatric population. In Japan, the awareness of the development of pediatric drugs is increasing, and many scientific meetings about juvenile animal studies are being held. A Japanese guideline for juvenile animal toxicity studies has been long awaited by many Japanese pharmaceutical companies because concrete directionality has not been available in Japan thus far. The Ministry of Health, Labour, and Welfare started to prepare the guideline for nonclinical safety studies in juvenile animals since October 2010. After completion of the Japanese guideline, guidelines would exist in the three regions: Japan, US, and Europe. Then, global development of pediatric pharmaceuticals would be accelerated effectively.

Historical control data on developmental toxicity studies in rodents.

Historical control data on rodent developmental toxicity studies, performed between 1994 and 2010, were obtained from 19 laboratories in Japan, including 10 pharmaceutical and chemical companies and nine contract research organizations. Rats, mice, and hamsters were used for developmental toxicity studies. Data included maternal reproductive findings at terminal cesarean sections and fetal findings including the spontaneous incidences of external, visceral, and skeletal anomalies. No noticeable differences were observed in maternal reproductive data between laboratories. Inter‐laboratory variations in the incidences of fetuses with anomalies appeared to be due to differences in the selection of observation parameters, observation criteria, classification of the findings, and terminology of fetal alterations. Historical control data are useful for the appropriate interpretation of experimental results and evaluation of the effects of chemical on reproductive and developmental toxicities.

Testicular toxicity induced by a triple neurokinin receptor antagonist in male dogs

Mechanism mediating the testicular toxicity induced by CS-003, a triple neurokinin receptor antagonist, was investigated in male dogs. Daily CS-003 administrations showed testicular toxicity, such as a decrease in the sperm number, motility and prostate weight; and an increase in sperm abnormality, accompanying histopathological changes in the testis, epididymis and prostate. A single CS-003 administration suppressed plasma testosterone and LH levels in intact and castrated males. The suppressed LH release was restored by GnRH agonist injection, suggesting that pituitary sensitivity to GnRH is not impaired by CS-003. Treatment with SB223412, a neurokinin 3 receptor antagonist, caused a similar effect to CS-003, such as toxicity in the testis, prostate and epididymis and decreased plasma level of LH and testosterone. In conclusion, CS-003-induced testicular toxicity is caused by the inhibition of neurokinin B/neurokinin 3 receptor signaling probably at the hypothalamic level in male dogs.

Effects of Maternal Hypoglycemia on Fetal Eye and Skeleton Development in Rats

The relationship between insulin-induced maternal hypoglycemia and teratogenicity was investigated in detail. We injected 4 different forms of insulin (insulin human, aspart, glargine, and detemir) subcutaneously at 1 or 2 dose levels to Sprague-Dawley rats from Days 6 to 11 of pregnancy, measured blood glucose levels, and conducted fetal examination. In the insulin human and aspart (low dose) groups, while severe hypoglycemia (approximately 50mg/dL) was seen, it lasted only 6h and no fetal anomalies were observed. Fetal axial skeleton anomalies were observed in the aspart (high dose) group, which exhibited intermediate-duration of severe hypoglycemia (9h). Eye and axial skeleton anomalies were observed in the glargine and detemir groups, which exhibited continuous severe hypoglycemia (≥9h). These results revealed that insulin-induced maternal hypoglycemia caused fetal eye and skeleton anomalies and the causative key factors were duration of maternal severe hypoglycemia.

Occurrence of headless sperms in adolescent rat urine

Summary Increased incidence of headless sperms (HS) was spontaneously observed in the urine of adolescent naïve male SPF/VAF Crl:CD(SD) rats. To clarify the factors contributing to this event, the HS incidence in urine and the epididymis was periodically examined in conjunction with measurements of testis and epididymis weights, motility and morphology of sperms and testosterone, transferrin or follicle-stimulating hormone (FSH) concentrations in serum and/or the testis. The urinary HS incidence was 61%, 69%, 44%, 30%, 14%, 9% and 7% in 100 sperms counted at ages 8, 9, 10, 11, 12, 13 and 14 weeks, respectively; namely, HS peaked at 9 weeks, gradually decreased from 10 weeks and became almost a plateau from 12 weeks onwards. The epididymal HS incidence, which was lower than that in urine, peaked at 8 weeks, decreased from 10 weeks and became almost zero from 12 weeks. By scanning electron microscopy of HS in the epididymis, a narrow gap between the sperm head and neck was clearly seen along with the posterior ring. Concentrations of testicular testosterone and transferrin, a marker for Sertoli cell maturation, reached mature animal levels at 12 weeks. In contrast, no change in serum FSH concentration was seen throughout the study period. These results demonstrate that a marked increase in urinary HS incidence in naïve rats at ages 8–11 weeks would be a physiological phenomenon seen in connection with the process of Sertoli cell maturation.

Investigating toxicity specific to adjuvanted vaccines

ABSTRACT In an attempt to understand the unique toxicity of adjuvanted vaccines, we studied how toxicity develops over time following vaccine administration. In addition to on‐ and off‐target toxicity typically observed with general pharmaceuticals, we observed toxicity associated with both the generation and the broad action of effectors (antibodies and/or cytotoxic T lymphocytes, CTLs). The impact on effector generation appears to be related to local tolerance specific to the adjuvant. The vaccine immune response by effectors serves to demonstrate species relevance as outlined in the recent WHO guideline on the nonclinical evaluation of adjuvanted vaccines. When regarded as pharmaceuticals that function at sites of local administration, adjuvants have inherent on‐ and off‐target toxicity. On‐target toxicity of the adjuvant is typically associated with effector generation, and could vary depending on animal species. Therefore, the use of species with sensitivity to adjuvants described in the WHO guidelines is required to evaluate the toxicity of the vaccine associated with effector generation. Changes in safety pharmacology endpoints would be considered off‐target and further studies are conducted only if changes in these endpoints are observed in nonclinical or clinical studies. Thus our decision tree does not recommend the routine conduct of stand‐alone safety pharmacology studies. Highlights“Time–toxicity profiles” of adjuvanted vaccines were elucidated.Unique profiles other than ordinary on‐vs off‐target toxicity were observed.Adjuvants are also found to have their own on‐vs off‐target toxicity profiles.These profiles account for animal species specificity of vaccines and adjuvants.The profiles were also useful for understanding safety pharmacology of vaccines.

Note on Regulatory Toxicology Requirements for Adjuvants and Vaccines; in View of the Newly Established WHO Guidelines

1 Review Division, Pharmaceuticals and Medical Devices Agency (PMDA), Kasumigaseki 3-3-2, Chiyoda-ku, Tokyo 100-0013, Japan 2 Research and Development Department, POC Clinical Research Inc. Taishidou 4-11, Setagaya-ku, Tokyo 154-0004, Japan 3 Pathology Department, The Chemo-SeroTherapeutic Research Institute, Kyokushi Kawabe 1314-1, Kikuchi-shi, Kumamoto 869-1298, Japan 4 Vaccine Research Laboratories, Kitasato Daiichi Sankyo Vaccine Co. Ltd., Kita-Kasai 1-16-13, Edogawa-ku, Tokyo 134-8630, Japan 5 Research Division, Chugai Pharmaceutical Co. Ltd., Komakado, 1-135, Gotemba, Shizuoka 412-8513, Japan

Investigation of the teratogenic potential of VLA-4 antagonist derivatives in rats

Very late antigen-4 (VLA-4), which is concerned with cell-cell adhesion, plays important roles in development of the heart, and some VLA-4 antagonists cause cardiac anomalies. In this study, we evaluated the teratogenic potential of VLA-4 antagonist derivatives as screening, and investigated the conditions that induce cardiac anomalies. Seventeen compounds were orally administered to pregnant rats throughout the organogenesis period, and fetal examinations were performed. In addition, drug concentrations in the embryos were assayed. As a result, the incidence of ventricular septal defect (VSD) ranged from 0 to 100% depending on the compound. Plasma drug concentrations in the dams were related to increased incidence of VSD; however, these incidences were not increased when the concentration of the compound in the embryos at 24h after dosing was low. It is considered that continuous pharmacological activity in the embryo for more than 24h might disrupt closure of the ventricular septum.