Imlunestrant with or without abemaciclib in advanced breast cancer: safety analysis from the EMBER-3 trial

The multinational EMBER-3 trial showed that among patients with ER-positive, HER2-negative advanced breast cancer (ER+ HER2- aBC) with recurrence or progression on or after endocrine therapy (ET), imlunestrant significantly prolonged PFS versus standard ET in patients with ESR1 mutations, and imlunestrant plus abemaciclib prolonged PFS versus imlunestrant alone in the overall population. Safety analyses from EMBER-3 have now been published. In both imlunestrant-containing arms, the most common treatment-emergent adverse events were reversible, low grade, single occurrences, occurred early in treatment, and resulted in few treatment-related discontinuations (imlunestrant 5%; imlunestrant plus abemaciclib 6%). TEAEs in the imlunestrant plus abemaciclib arm were managed with dose adjustments and supportive medication. Imlunestrant monotherapy had a similar safety profile between patients aged < 65 and ≥ 65 years, while imlunestrant plus abemaciclib had a similar safety profile to other abemaciclib plus ET combinations in both age groups. The authors conclude that imlunestrant with or without abemaciclib provides effective, convenient oral therapy with a manageable safety profile for patients with ER+ HER2- aBC) with recurrence or progression on or after ET.