PARP1 and cancer: Currently, four PARP inhibitors (olaparib, rucaparib, niraparib and talazoparib) have been approved by FDA for cancer therapy (https://www.fda.gov/drugs) and many others are under clinical trials (NCT01827384, NCT01605162, and veliparib) (https://clinicaltrials.gov/ct2/home) due to their synthetic lethality mechanism.