US regulators have approved Pfizer’s PARP inhibitor Talzenna to treat patients with breast cancer carrying a certain mutation, identified by a companion diagnostic developed by Myriad.

The decision allows physicians to prescribe Talzenna (talazoparib) to treat patients with deleterious or suspected deleterious germline BRCA-mutated (gBRCAm), HER2‑negative locally advanced or metastatic breast cancer.

Approval was based on data from the EMBRACA trial, in which 431 patients with gBRCAm HER2‑negative locally advanced or metastatic breast cancer were randomised to receive either talazoparib (1mg) or physician’s choice of chemotherapy.

The primary efficacy outcome was progression-free survival (PFS), which was estimated to be 8.6 and 5.6 months in the talazoparib and chemotherapy arms, respectively.

The FDA noted that the prescribing information for the drug includes warnings and precautions for myelodysplastic syndrome/acute myeloid leukemia, myelosuppression, and embryo-fetal toxicity.

Most common (≥20%) adverse reactions of any grade were fatigue, anemia, nausea, neutropenia, headache, thrombocytopenia, vomiting, alopecia, diarrhea, and decreased appetite.

European regulators are also currently reviewing Talzenna for this patient population, having accepted the marketing application last June.

The drug came to Pfizer in 2016 via its $14-billion purchase of Medivation, which had bought worldwide rights from BioMarin the year before.