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Juvenile animal toxicity studies are conducted to support applications for drugs intended for use in children. They are designed to address specific questions of potential toxicity in the growing animal or provide data about long-term safety effects of drugs that cannot be obtained from clinical trials. Decisions to conduct a juvenile animal study are based on existing data, such as a safety signal already identified in adult studies, or previous knowledge of the drug or chemical class for its potential to impair growth or developmental milestones. In 2006, the FDA issued an industry guidance in which considerations for determining when a juvenile animal study is warranted were outlined. A retrospective study was conducted covering years both before and after the issued guideline to examine the contribution of juvenile animal toxicity studies to the risk/benefit assessment of pediatric drugs at the FDA. The initial findings were presented as part of the May 2010 HESI workshop on the value of juvenile animal studies. The objective of the review was to better understand the value that the juvenile animal study contributes to regulatory decision making for pediatric drug development by looking at when the studies have been included in the product assessment; what, if any, impact the studies had on the regulatory decisions made; and whether the data were incorporated into the label. The data described below represent a first look at impact of the juvenile animal study since the pediatric legislation and the juvenile animal guidance were issued in the US.

Docosahexanoic acid (DHA) and arachidonic acid (ARA) are long chain essential fatty acids used as supplements in commercial infant formula. DHA/ARA deficient states are associated with adverse neurological outcomes in animals and humans. Preterm infants are at risk for DHA/ARA deficiency. A few clinical reports on the effects of fatty acid supplementation have shown benefit in preterm, low birth weight, and normal infants in the first year of life, whereas others did not. Studies in animals have reported shortened gestation, fetal growth retardation, reduced infant body mass, and increased fetal mortality with consumption of fatty acids during pregnancy. To understand the data that support fatty acid supplementation in infant formula, a review of the animal model literature was undertaken, to examine the effects of DHA/ARA on neurodevelopment, including the effects on visual acuity. Several points emerged from this review. (1) Animal studies indicate that requirements for DHA/ARA vary depending on developmental age. Alterations of the ratio of DHA/ARA can impact developmental outcome. (2) The available studies suggest that while supplementation of DHA/ARA in an appropriate ratio can increase tissue levels of these fatty acids in the brain and retina, tissues sensitive to depletion of fatty acids, the benefit of routine supplementation remains unclear. Few studies measure functional outcome relative to changes in physiologic pools of DHA/ARA after supplementation. (3) Animal literature does not support a clear long-term benefit of replenishing DHA/ARA tissue levels and administration of these fatty acids at concentrations above those in human milk suggests adverse effects on growth, survival, and neurodevelopment.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed to pregnant women. Some case-control studies have linked the NSAIDs aspirin and indomethacin with a risk of congenital abnormalities and low birthweight. High doses of aspirin produce developmental toxicity in rats (e.g., gastroschisis/umbilical hernia, diaphragmatic hernia [DH]) when administered during sensitive windows of development. Unlike other NSAIDs, aspirin irreversibly inhibits cyclooxygenases (COXs) 1 and 2. Hence, the developmental toxicity seen in rats after exposure to aspirin may be due to the irreversible inhibition of COX-1 and/or COX-2. If so, other NSAIDs, which act through a reversible inhibition of COX, may produce a weak developmental toxicity signal or no developmental toxicity signal when tested in preclinical models. To investigate this relationship, a comprehensive analysis of the NSAID developmental toxicity literature was undertaken to determine whether NSAIDs other than aspirin induce developmental anomalies similar to those elicited by aspirin. METHODS: Developmental toxicity studies were identified through literature searches of PubMed and TOXNET, and pregnancy outcome data were extracted and tabulated. By using a set of defined criteria, each study was evaluated for quality and assigned to one of five tiers. The relation between certain malformations and NSAID treatment was analyzed for the best studies (tiers 1–4) by using concurrent control data (Mantel–Haenszel and permutation tests) and by combining the concurrent control data with historical control data (χ2 test and permutation tests). RESULTS: A qualitative analysis of these data led to a focus on three types of malformations: DH, ventricular septal defects (VSDs), and midline defects (MDs). In rats, the incidences of VSD and MD were increased among fetuses treated with NSAIDs when compared with the concurrent controls. The extent of the increase was attenuated when the data from the aspirin studies were excluded from the analysis. There were no qualifying (i.e., tiers 1–4) aspirin studies conducted in rabbits, but the incidences of the three defects were increased over control incidences among non-aspirin NSAID-treated animals. Statistical analysis of these data was subsequently conducted. When tiers 1–4 were combined and compared with concurrent controls plus the most appropriate historical control database, the strongest associations were between NSAID treatment and VSD in rats, VSD in rabbits, and MD in rabbits. There also was some suggestion of an association between NSAID treatment and DH in rabbits. CONCLUSIONS: This analysis of the non-clinical NSAID literature demonstrated a possible association between exposure to NSAIDs and developmental anomalies. The anomalies were similar for aspirin and for other NSAIDs, but effects occurred at a much lower incidence with non-aspirin NSAIDs than previously reported with aspirin. Such a finding is consistent with the concept that reversible inhibition of COX-1 and/or COX-2 by other NSAIDs would produce weaker developmental toxicity signals than aspirin. However, there were limitations of the evaluated studies: (1) there were very few robust International Conference on Harmonization–compliant studies conducted with NSAIDs in the published literature; (2) many of the studies were conducted at doses well below the maximum tolerated dose (MTD), where effects are rarely seen; and (3) numerous studies were conducted above the MTD, where reduced numbers of fetuses hampered detection of low-incidence findings. Although weak associations were observed, these limitations prevented us from definitively determining the presence or absence of a developmental toxicity signal from the existing body of NSAID data. Further exploration of this hypothesis will require assessing the potential association in animal models by using dose levels centered around the MTD. Birth Defects Research (Part B) 68:5–26, 2003. © 2003 Wiley-Liss, Inc.