The developmental toxicity testing of biologics.

The characteristics of biologic drugs, as compared with small molecules, confer significant advantages for both the drug developer and the prospective patients. The necessity for, and the timing of, developmental toxicity testing in the preclinical program must be considered. Choice of an appropriate test system is of particular importance, one that shows pharmacodynamic activity comparable to man. Where the conventional rodent/non-rodent species show such functional cross-reactivity, those species can be used in developmental testing, but often the only relevant species will be a nonhuman primate, in which case an extended study design (the ePPND) should be the default. Such an approach provides appropriate toxicity screening while reducing animal usage.

Terminology of developmental abnormalities in common laboratory mammals (version 2).

This update (Version 2) of the Terminology of Developmental Abnormalities in Common Laboratory Mammals (Version 1) 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 or interpretation. The skeletal terms have been augmented to accommodate cartilage findings.

Terminology of developmental abnormalities in common laboratory mammals (version 2).

This update (version 2) of the Terminology of developmental abnormalities in common laboratory mammals (version 1) by Wise et al. [Wise LD, Beck SL, Beltrame D, Beyer BK, Chahoud I, Clark RL, Clark R, Druga AM, Fueston MH, Guittin P, Henwood SM, Kimmel CA, Lindstrom P, Palmer AK, Petrere JA, Solomon HM, Yasuda M, York RG. Terminology of developmental abnormalities in common laboratory mammals (version 1). Teratology 1997;55:249-92] 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.

Terminology of developmental abnormalities in common laboratory mammals (Version 2).

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.

Analysis and integration of developmental neurotoxicity and ancillary data into risk assessment: a case study of dimethoate.

Dimethoate is an organophosphate (OP) pesticide used to control a wide variety of insects on agricultural crops and ornamentals. To ensure that dimethoate is used safely, it is important to determine exposure levels that protect against adverse effects at all life stages, including the developing fetus, infant, and child. Based on an analysis of a developmental neurotoxicity (DNT) study, a cholinesterase (ChE) sensitivity study, a cross-fostering study, and several single- and multigenerational reproductive toxicity studies, two potential critical endpoints for dimethoate were identified: brain ChE inhibition (ChEI) in adult females, and pup mortality. An initial evaluation concluded that pup mortality was a preferable endpoint, based on an increased number of pup deaths born to dams dosed with > or =3 mg/kg dimethoate via oral gavage. Closer examination, however, revealed that the pup deaths were clustered in a small number of litters in which the dams providing postnatal care exhibited maternal care deficits. When the data were analyzed using the dam as the unit of statistical significance, a significant increase in the average litter proportion of pup deaths was observed only when the dams were dosed postnatally with 6 mg/kg dimethoate while they were raising the pups. Gestational exposure (i.e., during pregnancy only) to 6 mg/kg dimethoate exerted no effect on pup survival. This leads to the conclusion that it is postnatal exposure of the nursing dams that is associated with pup mortality. Furthermore, a previous benchmark dose (BMD) meta-analysis approach revealed that BMDL(10) for adult females (the lower 95% bound of the dose resulting in a 10% reduction in the parameter of interest) for ChEI was > 3-fold lower than the BMDL(10) for pup mortality (0.19 and 0.68 mg/kg, respectively). Overall, this study underscores the importance of using the dam as the unit of statistical significance when assessing data collected in the perinatal period, and it is concluded that adult brain ChEI is the correct critical endpoint for assessing risk of dimethoate toxicity.