Pfizer’s Ibrance flunks early breast cancer trial

Pfizer’s oral CDK4/6 inhibitor Ibrance has failed to meet the primary endpoint of improved invasive disease-free survival (iDFS) in early breast cancer, nixing its chances in the adjuvant setting.

The results come from the phase III PENELOPE-B trial, which evaluated Ibrance (Palbociclib) in women with hormone receptor-positive (HR+), human epidermal growth factor-negative (HER2-) early breast cancer who have residual invasive disease after completing pre-surgery chemotherapy.

The trial compared one year of Ibrance treatment plus at least five years of standard adjuvant endocrine therapy to place plus at least five years of standard adjuvant endocrine therapy.

Pfizer didn’t reveal the full data in its statement, adding only that the detailed finding from the PENELOPE-B study are set to be presented at an upcoming medical congress.

Ibrance is already approved in the US for the treatment of adult patients with HR+, HER2- advanced or metastatic breast cancer in combination with an aromatase inhibitor as initial endocrine based therapy in postmenopausal women or in men.

“This is the first randomised phase III study to establish mature iDFS results for a CDK4/6 inhibitor as part of the adjuvant treatment for early breast cancer,” said Chris Boshoff, chief development officer, oncology, Pfizer Global Product Development.

“While we are disappointed with this result, we look forward to continuing to work with our research partners to understand subgroup data and how these could inform the development of our next-generation CDK inhibitors in early breast cancer,” he added.

Pfizer had been hoping that the therapy could show early potential in a high-risk population, although that hope seems now to have been finally crushed.