- Pfizer Inc.'s investigational PARP inhibitor beat standard of care chemotherapy at improving progression free survival (PFS) for breast cancer patients with specific mutations, according to data released Friday.
- Results from the Phase 3 EMBRACA study showed, among breast cancer patients with BRCA1 or BRCA2 mutations, median PFS was 8.6 months for those taking talazoparib and 5.6 months for those receiving physician's choice standard of care chemotherapy.
- The trial enrolled 431 participants, who were then split into experimental and non-experimental arms in a two-to-one ratio. Overall discontinuation rates between the arms were 7.7% and 9.5%, respectively, and around 30% of the patients in both demonstrated serious adverse events.
PARP inhibitors have been potent anti-cancer agents for patients with BRCA mutations.
When the Food and Drug Administration approved AstraZeneca plc's Lynparza (olaprib) back in 2014, for instance, regulators based the decision on data from a single-arm Phase 2 study of patients with germline BRCA-mutated advanced ovarian cancer. The data showed overall response rate of 34% and a median duration of response of 7.9 months.
More recently, AstraZeneca revealed positive results from the Phase 3 OlympiAD trial demonstrating that Lynparza significantly improved progression-free survival for patients with BRCA-mutated metastatic breast cancer. Median PFS for participants taking the drug was 7 months versus 4.2 months for those who received chemotherapy.
Notably, Pfizer's EMBRACA readout puts talazoparib on a somewhat equal playing field with Lynparza in terms of efficacy and safety — though it's always hard to compare trial results unless the drugs in question go head to head. In any case, Pfizer has maintained an optimistic view of its candidate since it came onboard through the acquisition of Medivation.
Surely part of that optimism comes from the returns PARP drug developers are already seeing. Lynparza was first PARP inhibitor to receive FDA approval, and currently leads in space in terms of revenue; it brought in $81 million during the third quarter. Meanwhile, Tesaro Inc.'s Zejula (niraparib) and Clovis Oncology Inc.'s Rubraca (rucaparib) fetched $39.4 million and $16.8 million, respectively, over the period.
"When we bought Medivation, we said that the value drivers are, one, continue growth in the metastatic setting, primarily by growing prescription from urologists," said Albert Bourla, group president of Pfizer's Innovative Health unit, during a third quarter earnings call. "The second was to obtain a broader indication in non-metastatic prostate cancer. And the third was to develop and commercialize talazoparib."
The company is also looking at pairing talazoparib with Bavencio (avelumab) in multiple tumor indications and Xtandi (enzalutamide) in prostate cancer.