Imlunestrant with or without Abemaciclib in Advanced Breast Cancer

BACKGROUND: ). METHODS: mutations and among all patients and with imlunestrant-abemaciclib as compared with imlunestrant among all patients who had undergone randomization concurrently. RESULTS: mutations, the median progression-free survival was 5.5 months with imlunestrant and 3.8 months with standard therapy. The estimated restricted mean survival time at 19.4 months was 7.9 months (95% confidence interval CI, 6.8 to 9.1) with imlunestrant and 5.4 months (95% CI, 4.6 to 6.2) with standard therapy (difference, 2.6 months; 95% CI, 1.2 to 3.9; P<0.001). In the overall population, the median progression-free survival was 5.6 months with imlunestrant and 5.5 months with standard therapy (hazard ratio for progression or death, 0.87; 95% CI, 0.72 to 1.04; P = 0.12). Among 426 patients in the comparison of imlunestrant-abemaciclib with imlunestrant, the median progression-free survival was 9.4 months and 5.5 months, respectively (hazard ratio, 0.57; 95% CI, 0.44 to 0.73; P<0.001). The incidence of grade 3 or higher adverse events was 17.1% with imlunestrant, 20.7% with standard therapy, and 48.6% with imlunestrant-abemaciclib. CONCLUSIONS: -mutation status. (Funded by Eli Lilly; EMBER-3 ClinicalTrials.gov number, NCT04975308.).