Their antitumor effects primarily depend on inducing synthetic lethality in specific tumor types, especially those with defects in homologous recombination (HR) repair pathways, such as tumors containing mutations in BRCA1 or BRCA2 genes.[21, 36] PARP1 inhibitors are widely used in the treatment of HR‐deficient tumors, including ovarian cancer, breast cancer—particularly triple‐negative breast cancer—and prostate cancer. Here, PARP1 is linked to breast cancer.