An inhibitor of PARP1, PARP2, and TNKS1/2 (IC50s = 1, 1.2, and 50-11 nM, respectively); selective for PARP1, PARP2, and TNKS1/2 over PARP3 and PARP6-15 (IC50s = >3 μM); inhibits growth of DT40 cells in a PARP-dependent manner (IC50s = 3.2 and >15 μM for wild-type and PARP-/- cells, respectively); decreases expression of Wnt/β-catenin signaling pathway proteins in SW480 cells; enhances antitumor activity of temozolomide and carboplatin in a B16/F10 isograft model and MX-1 mouse xenograft model, respectively; inhibits tumor growth in a BRCA1 mutant MDA-MB-436 breast cancer mouse xenograft model at 30 and 100 mg/kg per day; delays hair regrowth in mice following hair removal,