Introduction: A New Tool for Breast Cancer Treatment
On September 25, 2025, the FDA approved Inluriyo (imlunestrant), an oral selective estrogen receptor degrader (SERD), for ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer (MBC) after progression on endocrine therapy (ET).
Who Qualifies for Inluriyo?
Inluriyo is approved for adults with ER+, HER2-, ESR1-mutated advanced or MBC after prior ET, such as aromatase inhibitors with or without CDK4/6 inhibitors.
EMBER-3 trial eligibility included:
- Prior ET with aromatase inhibitors (± CDK4/6 inhibitors)
- ESR1 mutations in the ligand-binding domain, verified by Guardant360 CDx
- Exclusions: Patients suitable for PARP inhibitors; no prior fulvestrant or exemestane in the control group
Since the trial stratified patients by prior CDK4/6 inhibitor use, visceral metastases, and region, it reflects diverse oncology settings.
EMBER-3 Trial: Key Efficacy Results
The Inluriyo FDA approval is based on the EMBER-3 trial (NCT04975308), a randomized, open-label phase 3 study with 874 patients, comparing Inluriyo to standard ET (fulvestrant or exemestane).
| Endpoint | Inluriyo (n=138) | Standard ET (n=118) | HR (95% CI); P-value |
|---|---|---|---|
| Median PFS (mo) | 5.5 (3.9-7.4) | 3.8 (3.7-5.5) | 0.62 (0.46-0.82); 0.0008 |
| Response Rate | 14.3% | 7.7% | N/A |
| Survival | Immature (31% deaths); trend (HR 0.55, 0.35-0.86; P<0.01) | – | – |
Progression-free survival (PFS) followed RECIST v1.1 standards.
Safety and Side Effects
In EMBER-3, Inluriyo had a manageable safety profile, with most side effects being mild (grade 1-2).
Common side effects (≥10%):
- Low hemoglobin (25%)
- Joint or muscle pain (20%)
- Fatigue (18%)
- Diarrhea (15%)
- Nausea (14%)
- High liver enzymes (ALT/AST, 12% each)
- Low neutrophils, calcium, or platelets (11% each)
- High triglycerides or cholesterol (10% each)
- Constipation or abdominal pain (10% each)
Only 5% of patients stopped Inluriyo due to side effects (vs. 4% control). Importantly, Inluriyo may cause harmირ
System: harm to an unborn baby, so contraception is advised.
Dosing and Administration
- Dose: 400 mg (two 200 mg tablets) orally once daily.
- Administration: Take on an empty stomach (≥2 hours before or ≥1 hour after food).
- Monitoring: Regular checks for blood counts, liver function, and lipids; adjust for CYP3A drug interactions.
- Duration: Continue until disease progression or severe side effects.
No major warnings; full details on Drugs@FDA.
Impact on Oncology Practice
The Inluriyo FDA approval provides a new oral option for ESR1-mutated MBC, addressing ET resistance.
Ongoing studies:
- EMBER-4 (NCT05514054): Testing in early breast cancer.
- Trials with CDK4/6 inhibitors for broader use.
Oncologists should discuss options with teams, considering patient history and preferences.
Resources for Oncology Specialists
Related: Endocrine Resistance Strategies
FDA Approval Details
EMBER-3 Trial
Eli Lilly Oncology: Inluriyo prescribing and support programs
ASCO Guidelines: ESR1 testing updates
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