Pfizer palbociclib trial disappoints, despite meeting primary endpoint

At the American Association of Cancer Research (AACR) Annual Meeting 2014 in San Diego, US pharma giant Pfizer (NYSE: PFE) announced much anticipated results from the PALOMA-1 study, a randomized Phase II study of palbociclib (PD-0332991) in combination with letrozole which, while meeting its primary endpoint, disappointed investors, with the firm’s shares falling 3% to $31.16 by close yesterday.

PALOMA-1 achieved its primary endpoint by significantly prolonging progression-free survival (PFS) compared with letrozole alone in post-menopausal women with estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-) locally advanced or metastatic breast cancer. For women treated with the combination of palbociclib plus letrozole, the median PFS was 20.2 months, a statistically-significant improvement compared to the 10.2 months of PFS in women who received letrozole alone (hr=0.488 [95% ci:0.319)(hr=0.488 [95% ci:0.748])(hr=0.488 [95% ci:p=0.0004).

"These data demonstrate the potential of palbociclib to be a major advance in the treatment of women with this type of advanced breast cancer," said Mace Rothenberg, senior vice president of clinical development and medical affairs and chief medical officer for Pfizer Oncology.