OEFilterType::PAINS is a new filter for removing substructures that commonly cause problems in bioassays. The SMARTS patterns used in this filter have been adapted from the SLN patterns in the original paper:
Baell, J.B. and Holloway G.A.,New Substructure Filters for Removal of Pan Assay Interference Compounds (PAINS) from Screening Libraries and for Their Exclusion in Bioassays,Journal of Medicinal Chemistry, Vol 53, pp. 2719-2740, 2010
The PAINS section.