Pfizer is stopping early a late-stage study of Ibrance as a second-line treatment for breast cancer because the drug clearly met progression-free survival targets.

The Phase III PALOMA-3 trial showed that Ibrance (palbociclib) plus fulvestrant significantly boosted progression-free survival compared to fulvestrant/placebo in women with hormone receptor positive, human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer, whose disease had worsened during or after endocrine therapy.

Pfizer notes that these are the first randomised Phase III trial results for Ibrance, a novel medicine that inhibits the enzymes CDK4 and CDK6. The drug won FDA accelerated approval earlier this year as a first-line treatment (in combination with Novartis’ Femara [letrozole]) for women with advanced or metastatic oestrogen receptor positive, ER+/HER2- breast cancer, but this was based on mid-stage data.

A full set of results will be submitted for presentation at the American Society of Clinical Oncology (ASCO) 2015 Annual Meeting later this year, the drug giant said, also noting that it is “engaging in discussions with health authorities regarding a regulatory path forward”. 

Ibrance has already been forecast a future blockbuster, with annual peak sales of up to $5 billion; approval in the second-line setting would likely further strengthen its position in the market.