Toward a comparative retrospective analysis of rat and rabbit developmental toxicity studies for pharmaceutical compounds

Based on a proposal made at the ICH Workshop in Tallinn, Estonia (2010), the value of the rabbit embryo-fetal development (EFD) versus the rodent EFD was examined by the HESI DART group. A cross-industry data survey provided anonymised EFD and toxicokinetic data from EFD studies on over 400 marketed and unmarketed drugs (over 800 studies) that were entered by experts at RIVM into US EPA's ToxRefDB style database. The nature and severity of findings at the lowest observed adverse effect level (LOAEL) are being reviewed to quantitate the frequency with which lesser signs of embryo-fetal effects (e.g., delays in ossification, minor changes in frequency of variants) are driving the LOAELs. Interpretation was based on exposure rather than administered dose. This paper provides an update of this ongoing project as discussed during a workshop of the European Teratology Society in Ispra, Italy (2013). This was the first presentation of the initial data set, allowing debate on future directions, to provide a better understanding of the implications of either delaying a rabbit EFD or waiving the need in particular circumstances.