This kind of therapy could ideally selectively kill tumor cells while sparing normal cells and reduce potential off-target side effects, for example, the clinically-used poly(ADP-ribose) polymerase 1 (PARP1) inhibitors in the selective treatment of breast cancer 1/2 (BRCA1/2) deficient cancers [1, 2]. The gene discussed is PARP1; the disease is breast carcinoma.