PARP1 and neoplasm: The small molecule ABT-888 (Fig. 2A) has been characterized as a potent (low to sub-nanomolar binding) PARP-1/2 inhibitor with good oral availability and permeability for crossing the blood–brain barrier in tumour models.23 To ensure ABT-888 treatment demonstrated the desired effect of limiting PAR polymer formation, we treated HEK293FT cells with MNNG, with or without concurrent ABT-888 (Fig. 2B).