An extended Reference Chemical Potency List (RCPL) for characterising the performance of New Approach Methodologies (NAMs) in measuring the skin sensitisation potency of fragrance chemicals

The development of a Reference Chemical Potency List (RCPL), and its purpose, has been described previously. That original RCPL comprised 33 chemicals, of varying skin sensitising activity, for each of which a discrete Potency Value (PV) was derived, based upon the best available human and/or animal (local lymph node assay) data. The purpose of the RCPL was to provide a reliable tool that would facilitate evaluation of the ability of New Approach Methodologies (NAMs) to measure skin sensitising potency. We here report the construction of an extended RCPL with 77 additional chemicals by applying the weight of evidence framework used previously. This extended RCPL adheres to the salient features of the original database. These comprise a focus largely on fragrance chemicals, provision of a wide range of chemical structures and of skin sensitising potency, the inclusion of both direct and indirect (pre- and pro-) haptens, the exclusion of NAMs data for the derivation of PVs, and avoidance of the use of potency categories for the classification of chemicals. It is anticipated that this extended RCPL will provide a more powerful database with which to assess the strengths and weakness of recently developed NAMs in the measurement of skin sensitising potency.