What Comes After a CDK4/6 Inhibitor? SABCS 2025 Findings from the evERA Study
In this article
Resistance to CDK4/6 Inhibitors in HR+ Metastatic Breast Cancer: SABCS 2025 Findings from the evERA Trial
CDK4/6 inhibitors (palbociclib/ribociclib) are standard treatment for HR-positive metastatic breast cancer, but resistance inevitably develops. After disease progression (post-CDK4/6), available options are limited and PFS is short. The study presented at SABCS 2025, evERA , shows how combining the next-generation oral SERD Giredestrant with Everolimus can overcome this resistance.
1) Clinical Need: The "Post-CDK4/6" Gap
After progression on CDK4/6 inhibitors, progression-free survival (PFS) with standard endocrine therapies generally remains around 3-6 months. evERAaimed to create synergy in this challenging patient group by combining a potent oral SERD (giredestrant) with the mTOR pathway inhibitor Everolimus. [1]
2) Study Design
A total of 420 patients were randomized to two arms:
• Experimental Arm: Giredestrant (Oral, 30mg) + Everolimus
• Control Arm: Physician's Choice of AI (Letrozole/Exemestane, etc.) + Everolimus
All patients had previously received a CDK4/6 inhibitor and experienced progression.
3) Primary Result: Comparison of Median PFS
MonthsStatistical Strength
The combination reduced the risk of disease progression or death by 42% (HR 0.58; p<0.001). This is one of the most impressive differences seen to date in the "post-CDK4/6" setting.
4) Summary of Secondary Findings
| Metric | Giredestrant + Eve | Control (AI + Eve) |
|---|---|---|
| Objective Response (ORR) | 32% | 18% |
| Duration of Response (DOR) | 11.2 Months | 6.8 Months |
| ESR1 Mutation (HR) | 0.45 | - |
| Overall Survival (OS) | HR 0.72 (Trend) | - |
Note: Efficacy is more pronounced in patients with an ESR1 mutation (~25% of the population), with a risk reduction of 55%.
5) Why Does ESR1 Matter?
After prolonged endocrine therapy, the tumor develops mutations in the estrogen receptor (ESR1), acquiring resistance to standard drugs. As a SERD, giredestrant binds to and degrades the mutated receptor, overcoming this resistance and explaining the strong results in this subgroup (HR 0.45).
Safety Profile
The adverse-effect profile is generally consistent with the known effects of everolimus. Adding giredestrant did not produce any new, unexpected toxicity signals.
Common adverse effects (giredestrant arm):
• Stomatitis (Mouth Sores): 18% (Grade 3)
• Hyperglycemia: 12% (Grade 3)
• Treatment discontinuation rate: 11% (similar to the control arm).
5 Frequently Asked Questions
Expert Commentary
evERA has the potential to change our view of "standard care" in metastatic breast cancer. In resistant cases, increasing PFS from 5 to 10 monthsis a major clinical gain in delaying the transition to chemotherapy. We can say that the era of oral SERDs has begun.
Was this article helpful?
Your feedback helps us improve our content.
Reader comments
Share your comment
Your name and comment are published only after administrator approval. Your email address is never shown to visitors.
Be the first to comment.