PARP1 and breast cancer: Olaparib (AZD2281) inhibits PARP-1 and PARP-2 at single-digit nanomolar concentrations. Olaparib reportedly exhibits single-agent efficacy against breast cancer cells harboring BRCA1 deficiencies, has been applied to SW620 cell lysates, and can reportedly inhibit PARP-1 with an IC50 of ∼6 nM, fully inhibiting this enzyme at concentrations of 30–100 nM