Pfizer Presents Positive Phase II Data of PD-991

Pfizer Inc. has presented randomized phase II data that showed PD-0332991 (PD-991) in combination with letrozole, a significantly extended progression-free survival (PFS) compared with letrozole alone in post-menopausal patients with estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2ai), and locally advanced or metastatic breast cancer. For patients treated with the combination of PD-991 plus letrozole, median PFS was 26.1 months, a statistically significant improvement compared to the median PFS in women who received letrozole alone, which was 7.5 months (HR = 0.37 [95 percent CI: 0.21, 0.63]; P <0.001).