PARPi such as olaparib, the first FDA-approved PARPi for the treatment of BRCA-mutant HR-deficient breast cancer [8], are NAD+ analogs whose mechanism of action relies on the catalytic inhibition of PARP1, PARP2, and other PARP enzymes via their binding to the NAD+-binding site [9]. This evidence concerns the gene PARP1 and breast cancer.