Eli Lilly and Co (LLY) dropped some genuinely encouraging breast cancer data on Friday, and the headline number is one that matters a lot to patients: delaying chemotherapy by more than a year.

The company shared updated Phase 3 results for Inluriyo (imlunestrant), a treatment for patients with estrogen receptor positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer. These are patients whose disease had already progressed despite prior treatment with an aromatase inhibitor, with or without a CDK4/6 inhibitor.

The Monotherapy Numbers

First, the standalone results. When used alone, imlunestrant showed a clinically meaningful 38% reduction in the risk of disease progression or death. Median progression-free survival was 5.5 months versus 3.8 months for standard endocrine therapy. More impressively, in patients with ESR1-mutated disease specifically, the drug demonstrated an 11.4-month improvement in median overall survival: 34.5 months compared to 23.1 months with endocrine therapy. That's the kind of difference that actually matters in people's lives.

The Combination Therapy Shows Real Promise

But here's where things get interesting. When Lilly combined imlunestrant with abemaciclib, the results improved across the board. In all patients, the combination reduced the risk of progression or death by 41% compared to imlunestrant alone. Median progression-free survival nearly doubled, jumping from 5.5 months to 10.9 months.

The time to chemotherapy metric is particularly meaningful. Nobody wants to start chemotherapy earlier than necessary, given the side effects and quality of life impact. The combination therapy delayed time to chemotherapy by more than a year—27.8 months versus 15.5 months for imlunestrant alone. That's an extra year where patients can avoid the harsh realities of chemotherapy.

For patients with ESR1-mutated disease, median progression-free survival with the combination reached 11.0 months versus 5.6 months with imlunestrant alone. The results were consistent regardless of ESR1 mutation status, and showed durable benefit across efficacy endpoints.

What Happens Next

These findings were published in Annals of Oncology and presented at the San Antonio Breast Cancer Symposium. Lilly noted that follow-up for overall survival is ongoing, with additional analyses planned as the data matures.

The company is also investigating imlunestrant in earlier-stage disease. The Phase 3 EMBER-4 trial has completed enrollment of approximately 8,000 patients with ER+, HER2- early breast cancer who face an increased risk of recurrence. These patients had received two to five years of adjuvant endocrine therapy, reflecting the current standard of care with CDK4/6 inhibitors.

Lilly shares were up 1.26% at $1,022.09 at the time of publication on Friday.