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The EMBER-3 trial demonstrated the effectiveness of imlunestrant, both as monotherapy and in combination with abemaciclib, in patients with ESR1-mutated oestrogen (ER)-positive/HER2-negative advanced breast cancer (BC). Imlunestrant improved progression-free survival (PFS) and had a favorable safety profile, highlighting the promising potential of imlunestrant for this patient group.
The EMBER-3 trial (NCT04975308) was a phase 3, randomized, open-label study evaluating imlunestrant, a next-generation brain-penetrant selective oestrogen receptor degrader (SERD), in ER-positive/HER2-negative advanced BC1. Komal Jhaveri, MD, from the Memorial Sloan Kettering Cancer Center, in New York, presented the trial results2.
The trial included 874 participants who had disease progression after prior treatment with aromatase inhibitors, either alone or with a CDK4/6 inhibitor. Participants were randomly assigned to receive either imlunestrant alone, imlunestrant plus abemaciclib, or standard endocrine therapy (ET). The primary endpoint was investigator-assessed PFS comparing imlunestrant to standard of care in all participants and those with ESR1 mutations.
The results showed that in participants with ESR1 mutations, imlunestrant significantly improved PFS compared with standard therapy, with a median PFS of 5.5 months versus 3.8 months (HR 0.62; 95% CI 0.46–0.82; P<0.001). However, imlunestrant did not show a significant PFS benefit for the overall population. The combination of imlunestrant and abemaciclib resulted in a median PFS of 9.4 months, significantly better than imlunestrant alone (HR 0.57; 95% CI 0.44–0.73; P<0.001). This benefit was seen regardless of ESR1 mutation, PI3K pathway mutation, or treatment with prior CDK4/6 inhibitor.
Safety data revealed that imlunestrant, both alone and with abemaciclib, had a favorable profile, with common AEs including mild fatigue, diarrhea, and nausea. Discontinuation rates due to AEs were low, and there were no oral SERD-specific signals of cardiac or ocular toxicity.
“These data show that imlunestrant, either as a monotherapy or in combination with abemaciclib, provides an all-oral targeted therapy option after progression on ET for patients with ER-positive/HER2-negative advanced BC,” concluded Dr. Jhaveri.
Medical writing support was provided by Kulsoom Abdul.
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