Clopyralid is an herbicide that selectively inhibits the growth of the broadleaf weed L. palustris over a panel of 17 New Zealand native non-broadleaf plant species when applied at a concentration of 1.5 mg/L.1 It does not inhibit growth of human pluripotent stem cells (IC50 = >100 μM) or decrease nuclear translocation of the transcription factor SOX17, a marker of teratogenic risk.2 In vivo, clopyralid induces brain defects in rabbits, but not rats, when administered at a dose of 250 mg/kg.
1.Champion, P.D.Selective control of weeds in New Zealand wetlandsProceedings of the 51st New Zealand Plant Protection Conference251-254(1998) 2.Kameoka, S., Babiarz, J., Kolaja, K., et al.A high-throughput screen for teratogens using human pluripotent stem cellsToxicol. Sci.137(1)76-90(2014)