FDA Grants Approval for New Combination Therapy in ESR1-Mutated Breast Cancer

On September 18, 2026, the FDA approved Inluriyo (imlunestrant) in combination with Verzenio (abemaciclib) for adults diagnosed with estrogen receptor-positive (ER-positive), human epidermal growth factor receptor 2-negative (HER2-negative), advanced or metastatic breast cancer exhibiting an estrogen receptor 1 (ESR1) mutation, as identified by an FDA-approved test. To qualify, patients must have experienced disease progression following at least one line of endocrine therapy. Additionally, the FDA has authorized the Guardant360 CDx assay as a companion diagnostic for identifying ESR1 mutations.

In the phase 3 EMBER-3 clinical trial, the combination of Verzenio with Inluriyo demonstrated a 47% reduction in the risk of disease progression or death when compared to Inluriyo alone, based on a cohort of 159 patients with ESR1-mutated tumors. The median progression-free survival (PFS) was reported at 11.1 months for the combination therapy versus 5.5 months for Inluriyo alone, with an objective response rate (ORR) of 35% compared to 15%. However, overall survival data at this time remain immature. It is significant to note that Inluriyo did not improve PFS when compared to the clinicians’ choice of endocrine therapy (fulvestrant or exemestane) in the overall population or in patients without detectable ESR1 mutations, highlighting the treatment’s specific efficacy for the ESR1-mutated subset.

The safety profile of this combination aligns with the known side effects of each medication, with most adverse events categorized as Grade 1 to 2. Commonly reported adverse reactions included diarrhea, decreased neutrophil counts, nausea, fatigue, anemia, infections, and elevated liver enzymes. Important warnings and precautions include potential neutropenia, interstitial lung disease or pneumonitis, hepatotoxicity, venous thromboembolism, and embryo-fetal toxicity.

The recent approval follows the FDA’s earlier accelerated approval of Etcamah (camizestrant) in conjunction with a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor (abemaciclib, palbociclib, or ribociclib) for patients whose ESR1 mutation is identified prior to radiographic progression, an approach that still needs the confirmatory evidence of clinical benefit. In contrast, Inluriyo (imlunestrant) combined with Verzenio (abemaciclib) received full approval for use after disease progression on previous endocrine therapy. Given that ESR1 mutations commonly indicate acquired resistance during or following aromatase inhibitor therapy, these two approvals furnish biomarker-directed treatment options at distinct phases of the treatment trajectory. They also raise pertinent questions in breast cancer management: whether changes in endocrine therapy should occur when an ESR1 mutation is first detected via circulating tumor DNA testing or only after clinical progression.

Dr. Komal Jhaveri of Memorial Sloan Kettering Cancer Center and principal investigator of EMBER-3 commented, “In EMBER-3, switching both the endocrine therapy and CDK 4/6 inhibitor, for the majority of patients, to imlunestrant plus abemaciclib at disease progression achieved a median progression-free survival of 11.1 months and a safety profile consistent with that of each medicine individually, establishing a meaningful new treatment option.”

Disclaimer: This document is intended for informational purposes only and should not be considered medical advice. Please consult a healthcare professional for personal medical guidance.

Fuente: https://www.epocrates.com/online/article/fda-approves-inluriyo-combo-for-esr1-mutated-breast-cancer