Eli Lilly's Inluriyo Approved: A New Treatment for ESR1-Mutated Advanced Breast Cancer

On September 26, 2025, Eli Lilly and Company announced that its oral selective estrogen receptor degrader (SERD), Inluriyo (imlunestrant), received U.S. FDA approval for the treatment of adult patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2–), and ESR1-mutated advanced or metastatic breast cancer (MBC) whose disease has progressed after at least one line of endocrine therapy (ET).

Breast cancer is the second most common cancer worldwide. According to GLOBOCAN data, 2.3 million new cases were diagnosed in 2022 (approximately 1 in 4 newly diagnosed cancers), resulting in 666,000 deaths that year, ranking fourth among cancer deaths worldwide. Metastatic/advanced breast cancer has an extremely low survival rate, with a five-year survival rate of only 30%, creating a pressing clinical need.

The approval was based on results from the EMBER-3 trial: In 256 patients with ESR1-mutant MBC, Inluriyo reduced the risk of disease progression or death by 38% compared with standard endocrine therapy. The median progression-free survival (PFS) was 5.5 months, significantly superior to the control group's 3.8 months (HR = 0.62, p = 0.0008), demonstrating clear efficacy. In terms of safety, Inluriyo-related adverse events (AEs) were mostly grade 1-2, with common reactions including decreased hemoglobin and musculoskeletal pain. Only 4.6% of patients permanently discontinued treatment due to AEs, 2.4% required dose reductions, and 10% required dose interruptions, demonstrating a well-tolerated treatment profile.

Lilly is currently advancing Inluriyo in the Phase 3 EMBER-4 trial, which plans to enroll 8,000 patients worldwide. The trial will evaluate Inluriyo's potential as an adjuvant treatment for ER+, HER2- early breast cancer (EBC) with a high risk of recurrence, continuing its expansion into breast cancer treatment.