Concordance of 3 alternative teratogenicity assays with results from corresponding in vivo embryo-fetal development studies: Final report from the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ) DruSafe working group 2.

An IQ DruSafe working group evaluated the concordance of 3 alternative teratogenicity assays (rat whole embryo culture, rWEC; zebrafish embryo culture, ZEC; and murine embryonic stem cells, mESC) with findings from rat or rabbit embryo-fetal development (EFD) studies. Data for 90 individual compounds from 9 companies were entered into a database. In vivo findings were deemed positive if malformations or embryo-fetal lethality were reported in either species. Each company used their own criteria for deciding whether the alternative assay predicted the in vivo findings. Standard concordance parameters were calculated, positive and negative predictive values (PPV and NPV) were adjusted for the aggregate portfolio prevalence of positive compounds (established by a survey of participating companies), and positive and negative likelihood ratios (LR+ and iLR-) were calculated. Of the 3 assays, only rWEC data were robustly predictive, particularly for negative predictions (NPVadj = 92%). However, both LR+ (4.92) and iLR- (4.72) were statistically significant for the rWEC assay. When analyzed separately for rats, the NPVadj and iLR-values for the rWEC assay increased to 96% and 9.75, respectively. These data suggest that a negative rWEC outcome could defer or replace a rat EFD study in certain regulatory settings.

Inter-laboratory assessment of a harmonized zebrafish developmental toxicology assay - progress report on phase I.

This report provides a progress update of a consortium effort to develop a harmonized zebrafish developmental toxicity assay. Twenty non-proprietary compounds (10 animal teratogens and 10 animal non-teratogens) were evaluated blinded in 4 laboratories. Zebrafish embryos from pond-derived and cultivated strain wild types were exposed to the test compounds for 5 days and subsequently evaluated for lethality and morphological changes. Each of the testing laboratories achieved similar overall concordance to the animal data (60-70%). Subsequent optimization procedures to improve the overall concordance focused on compound formulation and test concentration adjustments, chorion permeation and number of replicates. These optimized procedures were integrated into a revised protocol and all compounds were retested in one lab using embryos from pond-derived zebrafish and achieved 85% total concordance. To further assess assay performance, a study of additional compounds is currently in progress at two laboratories using embryos from pond-derived and cultivated-strain wild type zebrafish.

Predictive teratology: teratogenic risk-hazard identification partnered in the discovery process.

Unexpected teratogenicity is ranked as one of the most prevalent causes for toxicity-related attrition of drug candidates. Without proactive assessment, the liability tends to be identified relatively late in drug development, following significant investment in compound and engagement in pre clinical and clinical studies. When unexpected teratogenicity occurs in pre-clinical development, three principle questions arise: Can clinical trials that include women of child bearing populations be initiated? Will all compounds in this pharmacological class produce the same liability? Could this effect be related to the chemical structure resulting in undesirable off-target adverse effects? The first question is typically addressed at the time of the unexpected finding and involves considering the nature of the teratogenicity, whether or not maternal toxicity could have had a role in onset, human exposure margins and therapeutic indication. The latter two questions can be addressed proactively, earlier in the discovery process as drug target profiling and lead compound optimization is taking place. Such proactive approaches include thorough assessment of the literature for identification of potential liabilities and follow-up work that can be conducted on the level of target expression and functional characterization using molecular biology and developmental model systems. Developmental model systems can also be applied in the form of in vitro teratogenicity screens, and show potential for effective hazard identification or issue resolution on the level of characterizing teratogenic mechanism. This review discusses approaches that can be applied for proactive assessment of compounds for teratogenic liability.