Pfizer Inc.'s phase 3 trial of talazoparib to treat breast cancer showed superior progression-free survival compared to standard chemotherapy.

In the EMBRACA phase 3 trial, talazoparib was given to one group of patients with germline, or inherited BRCA1/2-positive locally advanced and metastatic breast cancer, while the other group was treated with chemotherapy.

The drug extended life while keeping the disease at bay for a median of 8.6 months, representing a 46% reduction in the risk of disease progression, while progression-free survival for those given chemotherapy was 5.6 months.

About 62.6% of patients treated with talazoparib achieved a complete or partial response, compared to 27.2% for those on chemotherapy.

The results also showed that progression-free survival was consistent across prespecified subgroups, which included hormone receptor status, triple negative or hormone receptor-positive, BRCA mutation (1 or 2), prior chemotherapy and history of central nervous system metastases.

The incidence of serious adverse events was 31.8% in the talazoparib arm and 29.4% in the chemotherapy arm. About 7.7% of patients who received the medicine discontinued treatment due to adverse events.

Pfizer said talazoparib showed promising activity in patients with germline BRCA and metastatic breast cancer in another phase 2 trial, ABRAZO.

These patients had been previously treated with platinum-based chemotherapy or were heavily pretreated with at least three prior lines of non-platinum-based chemotherapy.