EMBER-3 (imlunestrant/abemaciclib)
Trial question
What is the effect of imlunestrant/abemaciclib in patients with ER+, HER2- advanced breast cancer?
Study design
Multi-center
Open label
RCT
Population
Characteristics of study participants
99.0% female
1.0% male
N = 544
544 patients (538 female, 6 male).
Inclusion criteria: adult patients with ER+, HER2- advanced breast cancer that recurred or progressed during or after aromatase inhibitor therapy, administered with or without a CDK4/6 inhibitor.
Key exclusion criteria: prior treatment for advanced breast cancer; visceral crisis, lymphangitic spread within the lung, or any evidence of leptomeningeal disease; symptomatic or untreated brain metastasis; serious preexisting medical conditions that would preclude participation in the study; known allergic reaction against study treatment.
Interventions
N=213 imlunestrant/abemaciclib (imlunestrant 400 mg once daily plus oral abemaciclib 150 mg BID).
N=331 imlunestrant (400 mg once daily).
Primary outcome
Median progression-free survival
9.4 months
5.5 months
9.4 months
7.1 months
4.7 months
2.4 months
0.0 months
Imlunestrant/abemaciclib
Imlunestrant
Significant
increase ▲
Significant increase in median progression-free survival (9.4 months vs. 5.5 months; HR 1.75, 95% CI 1.37 to 2.27).
Secondary outcomes
Significant increase in median progression-free survival, patients with previous CDK4/6 inhibitor treatment (9.1 months vs. 3.7 months; HR 1.96, 96% CI 1.47 to 2.63).
Safety outcomes
No significant difference in serious adverse events.
Significant differences in diarrhea (86.1 vs. 21.4%), nausea (48.6% vs. 17.1%), neutropenia (48.1% vs. 5.2%), anemia (43.8% vs. 10.1%).
Conclusion
In adult patients with ER+, HER2- advanced breast cancer that recurred or progressed during or after aromatase inhibitor therapy, administered with or without a CDK4/6 inhibitor, imlunestrant/abemaciclib was superior to imlunestrant with respect to median progression-free survival.
Reference
Komal L Jhaveri, Patrick Neven, Monica Lis Casalnuovo et al. Imlunestrant with or without Abemaciclib in Advanced Breast Cancer. N Engl J Med. 2025 Mar 27;392(12):1189-1202.
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