The Substitution Principle within the REACH Regulation: Nuclear Receptor-Bound Endocrine Disruptors

Within the REACH Regulation (EC/1907/2006), the substitution principle for chemicals classified as Substances of Very High Concern (SVHC) for either human health or environmental risks has been implemented in order to support their replacement by suitable alternatives. Considering the thousands of chemicals to be tested within the frame of REACH, animal testing by internationally-accepted guidelines sounds unreasonable in terms of the required time, costs as well ethical issues. Hence, REACH recommended also the use of alternative methods to animal experimentation although no validated in silico or in vitro tools were available when regulation entried into force. To search for suitable alternatives to SVHC having an Endocrine Disruptor (ED)-like Mode-of-Action (MoA) by means of an integrated, tiered in silico-in vitro approach, the EU-granted project LIFE-EDESIA (contract no. LIFE12 ENV/IT/000633) is combining computational-based tools and cell-based bioassays, in order to develop a no-animal testing procedure to screen for chemicals having less or no toxicity in terms of endocrine disruption-like activities. A general view of the no-animal testing approach implementing REACH and the substitution principle will be given, emphasising ligand-nuclear receptor (NR) assessment by molecular docking (one of the LIFE-EDESIA in silico approaches) and the use of clinical biomarkers in in vitro toxicology to detect ED-like adverse effects in cell-based bioassays.