BRCA 1/2 plays an essential role in homologous recombination repair and breast cancer patients with BRCA 1/2 germline mutation have homologous recombination defects (HRD). Besides BRCA1 or BRCA2 germline mutation, a proportion of breast cancer is characterized as having HRD through germline mutation, somatic mutation, and epigenetic alteration of other homologous recombination repair (HRR) genes (which includes but are not limited to ATM, BARD1, BRIP1, CDK12, CHEK1, CHEK2, FANCL, PALB2, PPP2R2A, RAD51B, RAD51C, RAD51D, and RAD54L) (5). It is speculated that tumor with HRD may have clinical benefit from PARP inhibitor. However, the efficacy of talazoparib in advanced breast cancer with HRD is not known. The primary purpose of the present study is to evaluate the efficacy of talazoparib in breast cancer with HRD.
Talazoparib has shown clinical efficacy in breast cancer patients with germline BRCA1 or BRCA2 mutations. Beyond BRCA1 and BRCA2 mutations, it is plausible that talazoparib may have activity in patients with homologous recombination defects (HRD).