Eli Lilly's Inluriyo Gains FDA Approval, Marking Second Oral SERD for Breast Cancer Treatment

Eli Lilly has secured FDA approval for Inluriyo (imlunestrant), its oral selective estrogen receptor degrader (SERD) for the treatment of advanced breast cancer. This marks the second approval in this drug class, following Menarini Group's Orserdu, and represents a significant advancement in breast cancer therapy.

Approval Details and Clinical Efficacy

Inluriyo has been cleared for use in adults with ESR1-mutated, estrogen receptor (ER)-positive, HER2-negative metastatic breast cancer who have progressed after at least one line of endocrine therapy. The approval is based on the phase 3 EMBER-3 trial results, which demonstrated a 38% reduction in the risk of disease progression or death compared to standard hormone-suppressing therapies.

Key efficacy data from the EMBER-3 trial include:

• Median progression-free survival of 5.5 months for Inluriyo, approximately 2 months longer than standard therapies
• Significant benefit observed specifically in patients with ESR1 mutations, which occur in about half of the target patient population

Dr. Komal Jhaveri, clinical director of early drug development at Memorial Sloan Kettering Cancer Center and a principal investigator of the EMBER-3 trial, highlighted the importance of this approval, stating, "This represents an important advancement for patients with ESR1-mutated [metastatic breast cancer], a mutation found in nearly half of patients who have taken hormone therapies, often contributing to treatment resistance."

Safety Profile and Pricing

The majority of side effects associated with Inluriyo were reported as "low grade," including:

• Lower hemoglobin and white blood cell counts
• Pain
• Fatigue
• Diarrhea

Treatment discontinuation due to adverse events occurred in 4.6% of patients, while 10% experienced treatment interruptions. The FDA's prescribing information includes a warning about potential harmful effects on developing fetuses.

Eli Lilly has set the list price for a 28-day supply of Inluriyo at $22,500 per patient.

Competitive Landscape and Future Prospects

The approval of Inluriyo adds to the growing field of oral SERDs, which aim to replace the injectable therapy fulvestrant, a longstanding component of breast cancer treatment. Several pharmaceutical companies are actively developing oral SERDs, including:

• Roche
• AstraZeneca
• Arvinas and Pfizer (partnership)

Lilly is exploring the potential of Inluriyo in early breast cancer as adjuvant therapy, with initial results expected in 2027. This could significantly expand the drug's market potential.

However, the impact of oral SERDs on cancer care remains uncertain. Some oncologists have expressed concerns about "unknowns" in existing oral SERD results, particularly their efficacy in patients without ESR1 mutations. The market for these drugs may be smaller than initially anticipated, as evidenced by Arvinas and Pfizer's recent decision to out-license their competing therapy.

As the landscape of breast cancer treatment continues to evolve, Inluriyo's approval marks an important step in the development of innovative, all-oral treatment approaches for patients with advanced disease.