PARP1 and cancer: The search found structurally unique non-NAD-like inhibitors that block PARP1’s role in cancer cells with better effectiveness and intensity than the conventional PARP1 inhibitors presently employed in treatments, besides drugs that exhibit structural similarities to NAD+ or existing PARP1 inhibitors., Identification of 5F02, a non-NAD-like inhibitor blocks the H4-mediated activity of PARP1 but not PARP2 or Tankyrase-1, and tested successfully against a variety of cancer cells, including BRCA1-deficient breast cancer line (MDA-MB-43) [198,199,200,201].