A Phase 3 interventional study of Atirmociclib and giredestrant in Early Breast Cancer and Estrogen Receptor Positive (ER+), Human Epidermal Growth Factor Receptor 2 Negative (HER2-), sponsored by Pfizer. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-22.
Sponsored by Pfizer · Phase 3, Interventional, and Treatment
This Phase 3 study will evaluate whether atirmociclib plus giredestrant improves invasive breast cancer-free survival compared with giredestrant alone in adults with ER-positive, HER2-negative early breast cancer at medium or high risk of recurrence.
This is a Phase 3, double blind, placebo controlled study of atirmociclib plus giredestrant vs. giredestrant monotherapy as adjuvant treatment in adult patients with ER+, HER2- early breast cancer. The study plans to enroll 3800 participants randomized 1:1 into one of two treatment arms (Arm A - investigational: atirmociclib plus giredestrant taken continuously in a 28-day cycle) or (Arm B - comparator: placebo plus giredestrant taken continuously in a 28-day cycle). Participants may be treated with atirmociclib/placebo up to 3 years and giredestrant up to 5 years followed by long term follow up for survival and evaluation of recurrence of disease.
12,815 studies on the registry are indexed under Breast Neoplasms; 2,920 are open to participants now.
This study's planned enrollment of 3,800 is above the median of 72 across 9,494 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Pfizer is the lead sponsor of 3,323 studies on the registry; 145 are open to participants now.
Of its 597 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
KEY INCLUSION CRITERIA
Histologically confirmed unilateral primary adenocarcinoma of the breast
Node positive or node negative as defined by:
pN0 and pT >1cm with at least one of the following:
KEY EXCLUSION CRITERIA
Has received the following prior systemic anti-cancer therapy for breast cancer
NOTES:
Atirmociclib tablet given orally twice daily, plus giredestrant capsule given orally once per day
Drug: Atirmociclib · Drug: giredestrant
Placebo atirmociclib tablets given orally twice a day plus giredestrant capsule given once a day
Drug: giredestrant · Other: Atirmociclib placebo
Atirmociclib tablet given orally twice daily, plus giredestrant capsule given orally once per day
Also known as: PF-07220060
giredestrant capsule given once a day
Atirmociclib placebo tablet given twice a day
Invasive Breast Cancer Free Survival (iBCFS)
iBCFS is defined as the time from the date of randomization to the date of first documented occurrence of invasive ipsilateral breast tumor recurrence, local-regional invasive breast cancer recurrence, invasive contralateral breast cancer, distant recurrence, or death from any cause, as determined by investigator assessment per STEEP v2.0 criteria
Time frame: Baseline until recurrence up to 64 months
Invasive Disease Free Survival (iDFS)
iDFS defined as the time from the date of randomization to the date of first documented occurrence of invasive ipsilateral breast tumor recurrence, local-regional invasive breast cancer recurrence, invasive contralateral breast cancer, distant recurrence, second primary invasive non-breast cancer, or death from any cause, as determined by investigator assessment per STEEP v2.0 criteria
Time frame: Baseline until recurrence up to 64 months
Disease Recurrence Free Survival (DRFS)
DRFS as per investigator assessment, defined as the time from the date of randomization to the date of distant recurrence as determined by investigator assessment or death from any cause, whichever occurs first
Time frame: Baseline until recurrence up to 64 months
Overall survival (OS)
OS is defined as the time from the date of randomization to the date of death due to any cause
Time frame: Baseline until recurrence up to 64 months
Number and percentage of Participants with Treatment-Emergent Adverse Events (AEs)
Type, incidence, severity of AE graded by NCI CTCAE v 5.0, seriousness and relationship to study intervention
Time frame: Baseline until recurrence up to 64 months
Percentage of participants With Clinical Laboratory Abnormalities
Time frame: Baseline until recurrence up to 64 months
Percentage of Participants With ECG abnormalities
Time frame: Baseline until recurrence up to 64 months
Patient Reported Outcomes (PRO)
Change from baseline in participant reported total score, well-being subscales and symptoms scores and TOI per FACT-ES
Time frame: Baseline until recurrence up to 64 months
Pre-dose Plasma Concentration (Ctrough) of atirmociclib
Time frame: Cycle 1 Day 15, Cycle 2 Day 1, and Cycle 3 Day 1. Cycle is defined as 28 days
No study locations are listed for this record.
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
Data sharing details ↗ · www.pfizer.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Atirmociclib