PARP-family ADP-ribosyltransferases (PARPs) and sirtuin deacetylases all use 
NAD(+) as cosubstrate for ADP-ribosyl transfer. PARP inhibitors are important 
research tools and several are being evaluated in cancer treatment. With the 
exception of a few tankyrase inhibitors, all current PARP inhibitors mimic the 
nicotinamide moiety in NAD(+) and block the nicotinamide binding pocket. We 
report here that while the activities of the four human sirtuin isoforms SIRT1, 
SIRT2, SIRT3 and SIRT6 are blocked by sirtuin inhibitor Ex527 in vitro, they are 
unaffected by the seven clinical and commonly used PARP inhibitors niraparib, 
olaparib, rucaparib, talazoparib, veliparib, PJ34, and XAV939. These findings 
indicate that PARP inhibitors containing planar nicotinamide mimetics do not 
bind to sirtuin cofactor sites. In conclusion, a simple commercially available 
assay can be used to rule out interference of novel PARP inhibitors with sirtuin 
NAD(+) binding.