Roche reports Phase III miss for giredestrant in first-line breast cancer setting

Edited by Robert McTiernan··3 min read

Roche’s giredestrant misses primary endpoint in persevERA trial for ER-positive advanced breast cancer Roche announced that the Phase III persevERA Breast Cancer study evaluating giredestrant in combination with palbociclib did not meet its primary endpoint of a statistically significant improvement in progression-free survival in ER-positive, HER2-negative locally advanced or metastatic breast cancer. The result complicates the trajectory of Roche’s oral selective estrogen receptor degrader (SERD) in the first-line advanced setting, even as the company points to positive Phase III readouts from two other giredestrant trials to sustain its broader development program.

Trial specifics

The persevERA Breast Cancer study is a Phase III, randomized, double-blind, placebo-controlled, multicenter trial that enrolled 992 patients globally. Participants with ER-positive, HER2-negative locally advanced or metastatic breast cancer were randomized to receive either giredestrant plus palbociclib or letrozole plus palbociclib as first-line treatment. The primary endpoint was investigator-assessed progression-free survival. Key secondary endpoints included overall survival, objective response rate, duration of response, and safety. While the study did not achieve statistical significance on its primary endpoint, Roche reported that a numerical improvement in PFS was observed, though no hazard ratio or p-value were disclosed. Adverse events in the giredestrant arm were described as manageable and consistent with the known safety profiles of each treatment. Full results are expected at an upcoming medical meeting.

Despite the miss, Roche signaled continued commitment to giredestrant across multiple settings. The US FDA recently accepted a New Drug Application based on the Phase III evERA study, which showed positive results for giredestrant plus everolimus in previously treated advanced disease. Roche also plans to submit Phase III lidERA data in early-stage adjuvant breast cancer to the US FDA in the coming weeks. A second first-line advanced study, pionERA, evaluating giredestrant with physician’s choice of CDK4/6 inhibitor in endocrine-resistant disease, is expected to read out in 2027. Levi Garraway, Roche’s Chief Medical Officer, stated: “We believe there is a path forward for combining giredestrant with a CDK4/6 inhibitor in the adjuvant setting and we are conducting further studies”. Giredestrant has not received regulatory approval for any indication to date.

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Research context

Giredestrant is an oral SERD and full antagonist designed to block estrogen from binding to ERα and trigger receptor degradation. Unlike fulvestrant, the only approved SERD, giredestrant is orally administered and active against ESR1-mutant forms of the receptor that commonly arise during endocrine resistance. ER-positive breast cancer accounts for approximately 70% of all breast cancer cases, and despite advances with CDK4/6 inhibitors and aromatase inhibitors, up to a third of early-stage patients eventually experience recurrence, while resistance in the advanced setting remains a persistent clinical challenge.

The oral SERD class has attracted substantial investment, though clinical setbacks have been common. Key competitors include:

  • Menarini/Stemline’s elacestrant (Orserdu), the first oral SERD approved by the US FDA in 2023 for ESR1-mutated ER-positive metastatic breast cancer.
  • Eli Lilly’s imlunestrant (EMBER-3), an oral SERD that received US FDA approval in early 2026 for ESR1-mutated advanced breast cancer.
  • AstraZeneca’s camizestrant (SERENA program), a next-generation oral SERD in Phase III development for both early and advanced ER-positive breast cancer settings.
  • Earlier stage programs include Accutar Biotechnology’s AC699, palazestrant (Olema Oncology) and vepdegestrant (Arvinas/Pfizer).

The persevERA miss narrows the differentiation case for giredestrant in the first-line combination setting, where letrozole plus a CDK4/6 inhibitor remains standard of care. Roche’s strategy now depends on the pending NDA review for evERA, the lidERA adjuvant submission, and the pionERA readout to establish giredestrant’s clinical position across the ER-positive breast cancer treatment continuum.