Adding ribociclib to letrozole significantly prolonged progression-free survival compared with letrozole alone in postmenopausal women who have received no prior therapy for advanced breast cancer, a preplanned interim analysis has shown.1

Ribociclib is a kinase inhibitor that inhibits cyclin-dependent kinases 4 and 6, which can promote cancer cell proliferation when over-activated.

The efficacy and safety were evaluated in the phase 3 MONALEESA-2 trial, which compared ribociclib plus letrozole with letrozole in postmenopausal women with hormone receptor-positive (HR+), human epidermal growth factor 2-negative (HER2-) breast cancer who had received no prior therapy for advanced disease. The study was stopped early due to the positive findings from the preplanned interim analysis.

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A total of 668 participants from 294 global sites were randomly assigned 1:1 to receive letrozole 2.5 mg orally daily in combination with ribociclib 600 mg orally daily for 3 weeks on, 1 week off, or placebo.

“We are excited that these results validate our belief that LEE011 in combination with letrozole can be a beneficial treatment option for women diagnosed with HR+/HER2- advanced breast cancer,” said Alessandro Riva, global head, oncology development and medical affairs, Novartis Oncology.

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In terms of safety, the adverse events observed with the combination were generally consistent with each component’s known adverse event profile.

The pivotal trial will continue to assess overall survival data, as well as overall response rate, clinical benefit rate, and health-related quality of life.                                        


  1. MONALEESA-2 trial of Novartis’ LEE011 (ribociclib) stopped due to positive efficacy results at interim analysis in HR+/HER2- advanced breast cancer [news release]. Basel, Switzerland; May 18, 2016. Accessed May 18, 2016.