Novartis announced detailed results at the European Society for Medical Oncology (ESMO) congress from the Phase III MONALEESA-2 trial, which investigated ribociclib in combination with Femara (letrozole) as a first-line treatment in postmenopausal women with hormone receptor-positive, HER2-negative advanced or metastatic breast cancer. The company stopped  the study earlier this year after a pre-planned interim analysis showed that it met its primary endpoint of a clinically meaningful improvement in progression-free survival (PFS).
The trial randomised 668 postmenopausal women with hormone receptor-positive, HER2-negative advanced breast cancer who received no prior therapy for their advanced breast cancer to receive ribociclib or placebo, both in combination with Femara. Along with the main goal of PFS, secondary endpoints of the study included overall survival, overall response rate, clinical benefit rate, health-related quality of life, safety and tolerability.
According to Novartis, results showed that ribociclib in combination with Femara reduced the risk of progression or death by 44 percent versus Femara alone, with the combination significantly extending PFS across all patient subgroups. The drugmaker noted that median PFS was 14.7 months in patients who received Femara alone, while the median point has not yet been reached in the combination arm. Further, ribociclib plus Femara significantly improved tumour shrinkage, as 57 percent of women with measurable disease saw their tumour size shrink by at least 30 percent, versus 37 percent given Femara alone.
The company indicated that marketing applications for the drug, also known as LEE011, are expected to be made in the US and Europe before the end of the year. The CDK 4/6 inhibitor was developed by the Novartis Institutes for BioMedical Research under a research collaboration with Astex Pharmaceuticals.
Last year, Pfizer's Ibrance (palbociclib) became the first CDK 4/6 approved  by the FDA, in combination with Femara, for the treatment of postmenopausal women with oestrogen receptor-positive, HER2-negative metastatic breast cancer. Analysts estimate that Pfizer's product will record sales of nearly $2.2 billion this year, with ribociclib, if approved, predicted to generate revenue of $1 billion by 2020.
Gabriel Hortobagyi, lead investigator on the MONALEESA-2 trial, suggested that ribociclib and Ibrance appeared very similar both in terms of their efficacy and side effects. "This is a practice-changing study and when it (ribociclib) is approved by the appropriate regulatory agencies it will be one of the major choices," Hortobagyi remarked. Meanwhile, Alessandro Riva, global head of oncology development and medical affairs at Novartis, said he believed the data showed that ribociclib was "at least as good" as Ibrance, adding that the company expects to gain the first approval for the drug by the end of June next year.
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