Pfizer's bid to develop Ibrance (palbociclib) for a certain form of early breast cancer has hit a critical setback after an early analysis of data concluded that it the drug was unlikely to hit its primary goal.

The collaborative Phase III early breast cancer PALbociclib CoLlaborative Adjuvant Study (PALLAS) is comparing Ibrance plus standard adjuvant endocrine therapy to standard adjuvant endocrine therapy alone in women and men with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) early (stage 2 and 3) breast cancer.

It is an academically-led global collaboration, involving more than 400 centres in 21 countries around the globe.

Following a preplanned efficacy and futility analysis of data, an independent Data Monitoring Committee (DMC) concluded that the drug is unlikely to show a statistically significant improvement in the primary endpoint of invasive disease-free survival (iDFS).

"We are disappointed in this outcome,” said Chris Boshoff, chief development officer, Oncology, Pfizer Global Product Development.

“Breast cancer is a leading cause of death around the world and delaying or preventing the development of metastatic disease is a significant unmet need. PALLAS is a large study with many subgroups and we are actively collaborating to determine if there are patients who may benefit from adjuvant treatment with the palbociclib combination," he added.

Patients currently receiving palbociclib in the study will be advised about next steps by their physicians and long-term follow up of all patients will proceed as planned.

No unexpected new safety signals were observed in patients receiving the drug, Pfizer noted.