PFM01 rescues the repair defect in 48BR (WT) and HSC62 (BRCA2-defective) primary cells, diminishes the RAD51 foci formation in 1BR3 (WT) and HSC62 (BRCA2-defective) cells, enhances non-homologous end-joining (NHEJ) in H1299 dA3 cells and reduces homologous recombination (HR) in U2OS DR-GFP cells, also substantially relieves the double-strand break (DSB) repair defect confers by mirin or PFM39 in irradiated G2 cells.