Drugs targeting the poly-(ADP-ribose) polymerase (PARP) enzymes PARP1 and PARP2 cause synthetic lethality in tumour cells with homologous recombination (HR) defects, including those with loss-of-function mutations in the BRCA1 or BRCA2 tumour suppressor genes1–3. Here, PARP1 is linked to neoplasm.