AMALEE Trial Shows 400mg Ribociclib Dose Fails to Match 600mg Efficacy in Advanced Breast Cancer
Key Insights
The phase II AMALEE trial found that ribociclib 400mg daily was not noninferior to 600mg in newly diagnosed hormone receptor (search)-positive, HER2-negative advanced breast cancer (search) patients.
While progression-free survival was similar between doses (26.9 vs 25.1 months), the 400mg group showed lower objective response rates (48.9% vs 56.1%) and longer time to response.
The lower dose demonstrated significantly improved safety with reduced grade 3-4 neutropenia (search) (41.0% vs 58.5%) and fewer dose reductions (15.4% vs 36.9%).
A phase II randomized trial has demonstrated that a reduced starting dose of ribociclib at 400mg daily fails to achieve noninferiority compared to the standard 600mg dose in patients with newly diagnosed hormone receptor (search)-positive, HER2-negative advanced breast cancer (search), according to results published in JAMA Oncology.
The AMALEE trial, conducted across 23 countries, randomly assigned 376 patients between June 2019 and December 2020 to receive either ribociclib 400mg daily (n=188) or 600mg daily (n=188), both administered for 3 weeks on/1 week off with a nonsteroidal aromatase inhibitor. All premenopausal women also received goserelin.
Efficacy Outcomes Show Mixed Results
After a median follow-up of 53.5 months, the primary endpoint of objective response rate revealed significant differences between the two dosing regimens. The 400mg group achieved a 48.9% objective response rate compared to 56.1% in the 600mg group, yielding a response ratio of 0.87 (90% CI = 0.74-1.03). This result failed to meet the prespecified noninferiority margin, which required the lower bound of the 90% confidence interval to be at least 0.814.
The reduced dose also demonstrated a longer median time to response at 13.1 months versus 9.0 months for the standard dose. However, other key efficacy measures showed comparable outcomes between the two groups, with median duration of response being 26.5 months versus 28.8 months, and median progression-free survival reaching 26.9 months versus 25.1 months, respectively.
Safety Profile Favors Lower Dose
The 400mg ribociclib dose demonstrated a substantially improved safety profile across multiple parameters. Grade 3 or 4 neutropenia (search) occurred in 41.0% of patients in the lower dose group compared to 58.5% in the standard dose group. Cardiac safety also improved, with the 400mg group showing a shorter ΔQTcF interval of 12.5ms versus 19.7ms at cycle 1 day 15, measured 2 hours post-dose.
Treatment tolerability was notably better with the reduced dose, as evidenced by dose reductions due to adverse events occurring in only 15.4% of patients compared to 36.9% in the 600mg group. Other toxicities including liver and kidney complications, interstitial lung disease/pneumonitis, and treatment discontinuations due to adverse events remained similar between the two groups.
Clinical Implications for Treatment Strategy
The study investigators concluded that while the AMALEE trial did not demonstrate objective response rate noninferiority for the 400mg dose, the results confirm the standard 600mg starting dose for hormone receptor (search)-positive, HER2-negative advanced breast cancer (search) while supporting dose reduction strategies to manage dose-dependent adverse events.
Dr. Sergio Cifuentes Canaval, Medical Oncologist at Las Américas Auna Clinic (search), noted that despite the failure to meet noninferiority for overall response rate, "efficacy outcomes were remarkably similar, while safety significantly improved with the 400mg dose." He suggested this evidence "opens the door for considering lower starting doses — particularly relevant in LMICs settings or in patients with a history of QT prolongation or concomitant QT-prolonging medications."
The research was led by Dr. Fatima Cardoso of Medical Oncology, ABC Global Alliance (search), Lisbon, Portugal, as the corresponding author for the JAMA Oncology publication.