A Study to Investigate the Efficacy and Safety of Letrozole SIE Compared With Femara® (Both Combined With the CDK4/6 Inhibitor Ribociclib) in Postmenopausal Women With HR-Positive, HER2-Negative, Inoperable Locally Advanced or Metastatic Breast Cancer
SIE-3
A Multicenter, Randomized, Double-Blind, Double-Dummy, Phase III Study to Evaluate the Efficacy and Safety of Letrozole SIE Compared to Femara® (Both in Combination With the CDK4/6 Inhibitor Ribociclib) in Postmenopausal Women With HR-Positive, HER2-Negative, Inoperable Locally Advanced or Metastatic Breast Cancer (SIE-3)
Other study identifiers
Sponsor study identifier
Secondary identifiers
CTIS
NIH
interventional
300
13 countries
30
Study Start
August 2026
Estimated (date passed)This estimate has passed. The registry has not confirmed an actual date for this milestone.
Primary Completion
February 2029
EstimatedPlanned date reported by the registry; this milestone is not confirmed as achieved.
Study Completion
December 2033
EstimatedPlanned date reported by the registry; this milestone is not confirmed as achieved.
Brief Summary
The purpose of this study is to evaluate the efficacy and safety of Letrozole SIE (injectable) compared to Femara® (oral tablet), both given together with ribociclib, for the first-line treatment of postmenopausal women with HR-positive, HER2-negative, inoperable locally advanced or metastatic breast cancer.
Registry Overview
Registry-reported information. Elapsed time and enrollment totals alone do not measure study progress or recruitment pace.
- Recruitment status
- not yet recruiting
- Estimated enrollment
- 300 participants
- Study completion date
December 2033
EstimatedPlanned date reported by the registry; this milestone is not confirmed as achieved.
- Listed locations
- 13 countries · 30 sites
Trial Relationships
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Study Timeline
Dates and qualifiers reported by the registry. Estimated dates do not confirm that a milestone has occurred.
First Submitted
January 9, 2026
Actual (reported)First Posted
January 14, 2026
Actual (reported)Study Start
August 2026
Estimated (date passed)This estimate has passed. The registry has not confirmed an actual date for this milestone.
Primary Completion
February 2029
EstimatedPlanned date reported by the registry; this milestone is not confirmed as achieved.
Study Completion
December 2033
EstimatedPlanned date reported by the registry; this milestone is not confirmed as achieved.
- Last Updated
- April 2, 2026
- Status Verified
- March 2026
- Last Update Submitted
- March 27, 2026