FDA Approves Lilly’s New Breast Cancer Drug Combination

The U.S. Food and Drug Administration (FDA) has approved a new drug combination from Eli Lilly for certain adults with advanced or metastatic breast cancer. The approval, announced on September 18, 2026, covers Inluriyo (imlunestrant) used with Verzenio (abemaciclib) for tumors that are estrogen receptor-positive (ER+), HER2-negative and carry an ESR1 mutation. The cancer must have progressed after at least one line of endocrine therapy.

What Did the FDA Approve?

The FDA approved imlunestrant (Inluriyo) in combination with abemaciclib (Verzenio) for adults with ER-positive, HER2-negative, ESR1-mutated locally advanced or metastatic breast cancer, when the disease has progressed following at least one line of endocrine therapy. The approval also includes the use of an FDA-authorized test to identify the relevant ESR1 mutation.

The FDA also approved the Guardant360 CDx companion diagnostic to help identify patients whose breast cancer carries ESR1 mutations and may be eligible for this treatment combination.

How Does the Drug Combination Work?

Inluriyo is an oral estrogen receptor antagonist. Verzenio is a CDK4/6 inhibitor. The two medicines target different biological mechanisms involved in ER-positive breast cancer growth. Both medicines are taken orally.

What Did the Clinical Trial Show?

The approval was supported by the Phase 3 EMBER-3 trial, which enrolled 874 adults with ER-positive, HER2-negative locally advanced or metastatic breast cancer who had previously received an aromatase inhibitor, alone or with a CDK4/6 inhibitor.

In an exploratory analysis of 159 patients with ESR1-mutated tumors, median progression-free survival was 11.1 months for patients receiving imlunestrant plus abemaciclib, compared with 5.5 months for those receiving imlunestrant alone. The FDA reported an objective response rate of 35% versus 15%, respectively. Overall-survival data were immature at the interim analysis.

Who Is This Treatment For?

• Adults with advanced or metastatic breast cancer
• Tumors that are estrogen receptor-positive (ER+)
• Tumors that are HER2-negative
• An ESR1 mutation detected using an FDA-authorized test
• Disease progression after at least one line of endocrine therapy

This approval is for a specific patient population; it does not mean the combination is approved for every type or stage of breast cancer.

Recommended Dosage

According to the FDA, the recommended dose of imlunestrant is 400 mg once daily on an empty stomach, taken at least two hours before food or one hour after food. The recommended abemaciclib dose in combination is 150 mg twice daily, with or without food, until disease progression or unacceptable toxicity.

Safety and Side Effects

The FDA prescribing information for the combination includes important safety warnings. Abemaciclib carries warnings and precautions related to diarrhea, neutropenia, interstitial lung disease or pneumonitis, liver toxicity, blood clots and embryo-fetal toxicity. Inluriyo also includes a warning regarding embryo-fetal toxicity.

Patients considering this treatment should discuss its potential benefits, risks, drug interactions and monitoring requirements with their oncology team. This article is for general information and does not replace medical advice.

Why This FDA Approval Matters

The approval adds another treatment option for a defined group of patients with advanced or metastatic ER-positive, HER2-negative breast cancer whose tumors have ESR1 mutations. The FDA’s decision is based on evidence from a randomized Phase 3 trial and includes a companion diagnostic to identify the relevant mutation.

Final Thoughts

The FDA’s September 18, 2026 approval gives eligible patients with ESR1-mutated, ER-positive, HER2-negative advanced or metastatic breast cancer another oral treatment option. The decision is supported by the EMBER-3 trial and a companion diagnostic designed to identify the relevant mutation.

Source: U.S. Food and Drug Administration; Reuters; Eli Lilly and Company.