The breakthrough therapy designation was based on preliminary Phase 2 trial, which demonstrated that women treated with the combination of palbociclib plus letrozole achieved a statistically significant improvement in median progression free survival (PFS) compared to women who received letrozole alone (26.1 months and 7.5 months, respectively).
The company said it will continue to work with the FDA to better understand the implications of Breakthrough Therapy designation on the palbociclib development program and to generate evidence needed to support a potential regulatory submission.
Pfizer has initiated a randomized, multi-centre, double-blind Phase 3 study, known as Study 1008, to assess palbociclib in combination with letrozole compared to letrozole alone as a first-line treatment for post-menopausal patients with ER+, HER2- locally advanced or metastatic breast cancer.
Breakthrough Therapy designation is intended to expedite the development and review of a potential new medicine to treat a serious or life-threatening disease.