Clinical Study of Local and Systemic Biological Impact of GLP1/GIP-Receptor Agonists in Patients With Breast Cancer: The CLARA Trial

NCT07676331 · Not yet recruiting

Last updated 2026-08-27

This clinical trial is testing how GLP1/GIP-receptor agonists affect breast cancer in women with hormone-receptor-positive early breast cancer by measuring changes in the Ki67 proliferation marker.

Status Not yet recruiting Approved but enrollment has not started.

Phase Phase 2 Tests whether it works and watches safety in a moderate group.

Type Interventional (clinical trial)

Design Randomized, open-label (no blinding) treatment study

Participants 168 people Planned (estimated).

Who can join Ages 18+ · female only

Timeline Started 2026-08 · est. completion 2028-05

What this study is testing ClinicalTrials.gov NCT07676331 ↗

Description as written by the study sponsor.

The CLARA trial is a phase II window-of-opportunity trial evaluating how a commonly used weight-loss medication (tirzepatide, a GLP-1/GIP receptor agonist) affects breast cancer biology, alone and in combination with standard hormone therapy (letrozole). The main goal is to determine whether tirzepatide, alone or combined with letrozole, reduces tumor cell growth.

Treatments tested

Tirzepatide Drug

Tirzepatide is a GIP and GLP-1R agonist. It is approved by FDA and EMA as a weight-loss drug for patients with BMI ≥30 kg/m2 or ≥27 kg/m2 and previously diagnosed with at least 1 weight-related comorbidity.
Letrozole (Aromatase Inhibitors) Drug

Letrozole is an nonsteroidal aromatase inhibitor (NSAI). It is an adjuvant endocrine treatment indicated for HR+ breast cancer.

Main thing measured	Ki67 proliferation marker
Sponsor	Universitaire Ziekenhuizen KU Leuven
Conditions studied	Hormone-receptor-positive Breast Cancer, Early Breast Cancer
GLP-1 drugs	—

Full protocol, eligibility, and contacts on ClinicalTrials.gov NCT07676331 ↗