A PARP1 inhibitor (Ki = 6.3 nM); inhibits PARP1 activity in permeabilized and intact SW620 cells (IC50s = 29 and 14 nM, respectively); potentiates the growth inhibitory effects of temozolomide and topotecan in vitro at 0.4 μM; also inhibits cell growth in a PARP1-independent manner (GI50s = 66 and 65 μM for cells derived from PARP1+/+ and PARP1-/- mice, respectively); leads to tumor regression in an SW620 mouse xenograft model when used in combination with temozolomide