As the fundamental mechanism of PARP inhibition is interfering with DNA repair pathways, another severe class effect, although rare, is the onset of secondary malignancies, namely, myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), with an incidence of 0.5%–1.4%, usually after long-term treatment. This evidence concerns the gene PARP1 and acute myeloid leukemia.