The FDA has approved ribociclib (Kisqali, Novartis) in combination with the aromatase inhibitor letrozole (Femara, Novartis) as initial endocrine-based therapy for the treatment of postmenopausal women with hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2–) advanced or metastatic breast cancer.
Ribociclib is a selective cyclin-dependent kinase inhibitor, a class of drugs that helps slow the progression of cancer by inhibiting cyclin-dependent kinase 4 and 6 (CDK4/6) proteins. These proteins, when overactivated, can enable cancer cells to grow and divide too quickly.
The FDA’s approval of ribociclib was based on data from a pivotal phase 3 trial that met its primary endpoint early, demonstrating a statistically significant improvement in progression-free survival (PFS) compared with letrozole alone at the first preplanned interim analysis. Ribociclib was reviewed and approved under the FDA’s breakthrough therapy designation and priority review programs.
The MONALEESA-2 trial enrolled 668 postmenopausal women with HR+/HER2– advanced or metastatic breast cancer who had received no prior systemic therapy for their disease. The results showed that ribociclib plus letrozole reduced the risk of progression or death by 44% compared with letrozole alone (median PFS not reached vs. 14.7 months, respectively; hazard ratio, 0.556; P < 0.0001).
More than half of the patients treated with ribociclib plus letrozole remained alive and progression-free at the time of the interim analysis; therefore, median PFS could not be determined. At a subsequent analysis with additional 11-month follow-up and progression events, median PFS was 25.3 months for ribociclib plus letrozole compared with 16.0 months for letrozole alone.
Ribociclib is taken with or without food as a once-daily oral dose of 600 mg (three 200-mg tablets) for three weeks, followed by one week off treatment. The drug is administered in combination with four weeks of treatment with any aromatase inhibitor.
Breast cancer is the second most common cancer among women in the United States. The American Cancer Society estimates that more than 250,000 women will be diagnosed with invasive breast cancer in 2017. Up to one-third of patients with early-stage breast cancer will develop metastatic disease.
Source: Novartis; March 13, 2017.