Patients with advanced breast cancer tied to an inherited gene mutation who were treated with an experimental Pfizer drug went about three months longer before their disease worsened than those who received chemotherapy in a late-stage study, according to data released Friday.

The drug, talazoparib, a once-daily pill that Pfizer acquired with its $14 billion purchase of Medivation, belongs to a class of medicines called PARP inhibitors that may induce tumor cell death. They have shown promise in advanced ovarian and breast cancers.

Patients in the Phase III study had mutations of the BRCA1/2 genes, the type of mutation that led actress Angelina Jolie to have preventive breast removal surgery.