No clinical trials have directly compared different PARP inhibitors, but preclinical studies have shown that PARP trapping capacity by different PARP inhibitors varies from strong to weak in a variety of tumor cells, including PC cells, talazoparib > niraparib > olaparib = rucaparib > veliparib (Figure 1) (18, 19). The gene discussed is PARP1; the disease is neoplasm.