postMONARCH
What it tests: Abemaciclib plus fulvestrant versus placebo plus fulvestrant in HR+/HER2− advanced breast cancer following progression on a prior CDK4/6 inhibitor plus endocrine therapy. Phase 3 overall survival results.
4Sight: postMONARCH
All ESMO 2026 4Sights
In brief
OncoAlert 4Sight, #ESMO2026
Final Overall Survival Analysis of postMONARCH: Abemaciclib Plus Fulvestrant After Progression on Prior CDK4/6 Inhibitor in HR+, HER2– Advanced Breast Cancer
Phase 3, double-blind trial (n=368): abemaciclib or placebo plus fulvestrant in HR+, HER2– ABC after progression on prior CDK4/6i + ET. Final OS analysis.
Median OS 32.1 vs 24.6 mo; HR 0.80 (0.60–1.06); p=0.1145, statistical significance not reached
Updated PFS HR 0.78 (0.62–0.99); nominal p=0.0390
Safety consistent with the established abemaciclib profile; no new signals
Numerically longer median OS, not statistically significant. While absolute PFS benefit was modest, overall evidence supports considering abemaciclib-based treatment after disease progression on prior CDK4/6i + ET.
Kevin Kalinsky
Giampaolo Bianchini · Erika Hamilton · Stephanie Graff · Kyong Hwa Park · Rinath Jeselsohn · Umut Demirci · Miguel Martin · Rachel Layman · Sara Hurvitz · Sarah Sammons · Peter Kaufman · Montserrat Muñoz · Jiun-I Lai · Holly Knoderer · Cynthia Sandoval · Aarti Chawla · Bastien Nguyen · Yanhong Zhou · Elizabeth Ravenberg · Lacey Litchfield · Lillian Smyth · Seth Wander