TOPOI/PARP-1-IN-1 (Compound B6) is an orally active, low cytotoxic TOPOI/PARP dual inhibitor with an IC 50 value of 0.09 μM for PARP1. TOPOI/PARP-1-IN-1 can effectively inhibit the proliferation and migration of cancer cells. TOPOI/PARP-1-IN-1 also causes cell cycle arrest in the G0/G1 phase and induces apoptosis. The tumor growth inhibition rate (TGI) of TOPOI/PARP-1-IN-1 in mice is 75.4%.