- Imetelstat animal and in vitro studies suggest it is not genotoxic or teratogenic. However, 13-cis-retinoic acid is known to be teratogenic. Pregnancy tests must be obtained in girls who are post menarchal. Males or females of reproductive potential may not participate unless they have agreed to use two reliable contraceptive methods. Pregnant or breast-feeding females will not be entered on this study due to the potential fetal and teratogenic adverse effects.