Developmental and reproductive toxicology testing in nonhuman primates (NHPs) has become more common due to the increasing number of biopharmaceuticals in drug development, since NHPs are frequently the only species to express pharmacologic responses similar to humans. NHPs may also be used to help resolve issues associated with small-molecule reproductive toxicology in traditional species (rodents and rabbits). Adequate designs in NHP are presented for developmental toxicity (embryo-fetal development, pre-postnatal development, enhanced pre-postnatal development), reproductive toxicity (male and female), and juvenile toxicity studies. Optional parameters that may be included in these studies are discussed, as are new study designs that consolidate multiple aspects of the reproductive assessment and thereby conserve the limited supply of sexually mature NHPs available for testing. The details described will assist scientists in pharmaceutical, regulatory, and contract research organizations who are involved in conducting these unique studies to optimize their design based on case-by-case considerations.

The objective of juvenile animal toxicity studies of pharmaceuticals is to obtain safety data, including information on the potential for adverse effects on postnatal growth and development. Studies in juvenile animals may assist in identifying postnatal developmental toxicities or other adverse effects that are not adequately assessed in the routine toxicity evaluations and that cannot be safely or adequately measured in pediatric clinical trials. Unlike the traditional reproductive and developmental toxicology studies that have been discussed in the accompanying reports, the design requirements for toxicity studies in juvenile animals are not explicitly defined in regulatory guidance. However, studies in juvenile animals can be useful in providing safety information necessary to enable pediatric clinical trials in pediatric patients or when there are special concerns for toxicities that cannot be safely or adequately measured in clinical trials. These juvenile animal toxicity studies are designed on a case-by-case basis. General design considerations and examples of study designs for assessment of juvenile animal toxicity are discussed.

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The testes from 136 male cynomolgus monkeys were examined histopathologically in order to investigate the relationship between the development of spermatogenesis and testis weight, age, and body weight. At Grade 1 (immature), Sertoli cells and spermatogonia were the only cell classes in the testis. At Grade 2 (pre-puberty), no elongated spermatids were observed in the testis, although a few round spermatids and small lumen formation were observed. At Grade 3 (onset of puberty), all classes of germ cells were observed in the testis, although seminiferous tubule diameters and numbers of germ cells were small. Slight debris in the epididymis was observed in almost all animals. At Grade 4 (puberty), almost complete spermatogenesis was observed in the seminiferous tubules and it was possible to ascertain the spermatogenesis stage as described by Clermont, although tubule diameters and numbers of germ cells were small. There was less debris in the epididymis than at Grade 3. At Grade 5 (early adult), complete spermatogenesis was observed in the seminiferous tubules. At Grade 6 (adult), complete spermatogenesis in the seminiferous tubules and a moderate or large number of sperm in the epididymis were observed. Moreover, sperm analysis using ejaculated sperm was possible. Logistic regression analysis showed that testis weight is a good indicator of testicular maturity.

This update (Version 2) of the Terminology of Developmental Abnormalities in Common Laboratory Mammals (Version 1) by Wise et al. (1997) incorporates improvements and enhancements to both content and organization of the terminology, to enable greater flexibility in its application, while maintaining a consistent approach to the description of findings. The revisions are the result of an international collaboration among interested organizations, advised by individual experts and the outcomes of several workshops. The terminology remains organized into tables under the broad categories of external, visceral, and skeletal observations, following the manner in which data are typically collected and recorded in developmental toxicity studies. This arrangement of the tables, as well as other information provided in appendices, is intended to facilitate the process of specimen evaluation at the laboratory bench level. Only the commonly used laboratory mammals (i.e., rats, mice, rabbits) are addressed in the current terminology tables. The inclusion of other species that are used in developmental toxicity testing, such as primates, is considered outside the scope of the present update. Similarly, categorization of findings as, for example, "malformation" or "variation" remains unaddressed, in accordance with the overall principle that the focus of this document is descriptive terminology and not diagnosis/interpretation. The skeletal terms have been augmented to accommodate cartilage findings.