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Clinical Trials

Pfizer’s Ibrance breast cancer drug combo fails to improve OS in phase 3 trial

PBR Staff Writer Published 27 June 2018

Pfizer said that its breast cancer drug Ibrance (palbociclib) in combination with fulvestrant was not statistical significant in extending overall survival (OS) in a phase 3 Paloma-3 trial.

The study assessed Ibrance in combination with fulvestrant against placebo plus fulvestrant in women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer whose disease has progressed after prior endocrine therapy.

Ibrance is an oral inhibitor of CDKs 4 and 6, which are crucial regulators of the cell cycle that activate cellular progression.

The phase 3 trial showed a positive trend in the hazard ratio supporting the Ibrance combination, while this trend did not achieve statistical significance.

Pfizer said that OS is a secondary endpoint of the Paloma-3 trial, buy its design was not optimized to detect a statistically significant difference in OS

Pfizer global product development chief development officer Dr Mace Rothenberg said: “While the difference in overall survival narrowly missed the threshold for statistical significance – a high bar for any trial in this patient population – it is similar, in absolute terms, to the improvement in median progression-free survival previously demonstrated in this trial.”

“Ibrance in combination with endocrine therapy has transformed the treatment landscape for patients with HR+, HER2- metastatic breast cancer.”

The Paloma-3 trial, which achieved its primary endpoint of progression-free survival (PFS) at interim analysis, showed a statistically significant and clinically meaningful improvement in PFS for Ibrance plus fulvestrant compared against placebo plus fulvestrant.

Based on the PFS demonstrated in Paloma-3 trial, the Ibrance in combination with fulvestrant secured approval in over 80 countries across the globe.

In the US, Ibrance secured approval for the treatment of HR+, HER2- advanced or metastatic breast cancer in combination with an aromatase inhibitor as initial endocrine based therapy in postmenopausal women, or fulvestrant in women with disease progression following endocrine therapy.