A new phase III trial of Pfizer’s Ibrance will test whether the drug is effective in early-stage as well as advanced breast cancer.
Ibrance (palbociclib) became the first drug in the new CD4/6 inhibitor class to reach the market after it was granted accelerated approval by the US FDA as a first-line therapy for advanced, hormone-positive breast cancer in February.
Since then, a late-stage trial of the drug as a second-line therapy in metastatic breast cancer was halted after it showed a clear therapeutic benefit, and now Pfizer wants to explore whether it can improve disease-free survival rate in patients with early-stage tumours that can be treated with surgery.
The aim is to quickly encourage use of the drug, which has been hailed as a breakthrough for patients whose breast cancer tests positive for oestrogen receptors but negative for the HER2 receptor targeted by drugs such as Roche’s Herceptin (trastuzumab).
Around two thirds of breast cancer cases fall into this category, and Ibrance’s benefits beyond standard therapy with drugs designed to block the growth-promoting effects on tumours could drive sales of $3bn to $5bn a year, according to analysts.
Pfizer will conduct the new trial – called PALLAS – in premenopausal and postmenopausal women as well as men who have stage 2 or stage 3 hormone receptor-positive/HER2-negative early breast cancer.
It will have an open-label design, with an estimated 4,600 participants receiving either standard hormonal therapy or hormonal therapy plus Ibrance for at least five years.
Ibrance was approved on the back of the PALOMA-1 trial, which revealed the combination of the drug with Novartis’ Femara (letrozole) doubled progression-free survival – to 20 months – compared to Femara alone.
Overall survival also improved although not by a clinically significant margin, and a second trial – PALOMA-2 – is now fully enrolled in order to confirm the earlier results.
Other CDK 4/6 inhibitors coming through the pipeline include Novartis’ ribociclib, which is in phase III development and Eli Lilly’s abemaciclib also in phase III trials.