Vepdegestrant For ESR1-Mutated Breast Cancer

  • The FDA has approved vepdegestrant for patients with ER+, HER2-, ESR1‑mutated advanced or metastatic breast cancer, along with the Guardant360 CDx test to identify who is eligible for treatment.
  • ESR1 mutations are found in roughly 20-40% of patients with metastatic disease previously treated with endocrine therapy, and they allow cancer cells to remain active despite estrogen-lowering drugs. This makes a targeted degrader like vepdegestrant a meaningful new option.
  • In the VERITAC‑2 trial, vepdegestrant significantly improved progression‑free survival in the ESR1‑mutated subgroup (5.0 months with vepdegestrant compared to 2.1 months with fulvestrant).
  • “By actively degrading the estrogen receptor through a PROTAC mechanism, vepdegestrant offers a mechanistically distinct alternative to fulvestrant with clinically meaningful efficacy,” Dr. Francisco J. Esteva, Chief of Breast Medical Oncology at Lenox Hill Hospital, tells SurvivorNet Connect.

Patients with ER+, HER2- ESR1‑mutated advanced or metastatic breast cancer now have a newly approved treatment option: vepdegestrant, a heterobifunctional protein degrader cleared for use in patients who have previously received endocrine therapy.

The U.S. Food and Drug Administration (FDA) approved vepdegestrant specifically for breast cancers carrying an ESR1 mutation, and also authorized the Guardant360 CDx liquid biopsy test as a companion diagnostic to identify eligible patients.

Dr. Francisco J. Esteva, Chief of Breast Medical Oncology at Lenox Hill Hospital, calls the approval a meaningful step forward.

“This introduces a biomarker‑driven, oral option for patients with ESR1‑mutated ER+ metastatic breast cancer, a setting where resistance to standard endocrine therapy is common,” he says.

ESR1 mutations, which allow cancer cells to remain active even when estrogen levels are driven down by hormonal therapy, are more common in patients previously treated with endocrine therapy, occurring in 20-40% of metastatic cases, according to the medical journal Breast Cancer Research.

Roughly one in three patients on long‑term aromatase inhibitors will eventually develop an ESR1 mutation, according to the report.

A ‘Mechanistically Distinct Alternative’

Vepdegestrant works differently from fulvestrant and other endocrine therapies.

“By actively degrading the estrogen receptor through a PROTAC mechanism, vepdegestrant offers a mechanistically distinct alternative to fulvestrant with clinically meaningful efficacy,” Dr. Esteva tells SurvivorNet Connect.

Its real‑world impact will depend on routine ESR1 testing and thoughtful integration with other targeted therapies, he adds.

The recommended dose is 200 mg orally once daily with food, continued until disease progression or unacceptable toxicity.

Promising Progression-Free Survival Data

The decision to approve vepdegestrant was based on results from VERITAC‑2, a randomized, open‑label, multicenter trial that enrolled 624 adults with ER+, HER2- advanced or metastatic breast cancer.

Of these, 270 patients had ESR1‑mutated tumors.

All of the trial participants had disease progression on one to two prior endocrine therapies, including at least one regimen with a CDK4/6 inhibitor.

In the ESR1‑mutated subgroup, vepdegestrant delivered a statistically significant improvement in progression‑free survival (PFS) compared with fulvestrant.

  • Median PFS: 5.0 months with vepdegestrant v. 2.1 months with fulvestrant
  • Hazard ratio: 0.57 (95% CI: 0.42–0.77)

The results show that vepdegestrant significantly prolonged PFS in patients with ESR1‑mutated disease, though this benefit did not extend to the full trial population without the mutation.