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

What Was Tested

In this phase 2 trial, researchers set out to test Tirzepatide.

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).

It had four arms (groups): Arm A (Control): Immediate surgery (no intervention), Arm B: letrozole (active comparator), Arm C: tirzepatide (active comparator) and Arm D: letrozole + tirzepatide (active comparator).

Patient undergoes immediate surgery without intervention.

The registry classes the interventions as drug.

More on the Plan

Secondary objectives are: * To compare adherence to the GLP1/GIP RA, letrozole and combined treatment. * To compare safety * To compare perioperative complications * To explore the feasibility and utility of circulating tumour DNA (ctDNA) in plasma samples collected throughout the study.

Who Took Part

Enrollment: 168 planned participants were the target.

It was open to women only aged from 18 years with no upper age limit.

Healthy volunteers were not accepted; participants needed the condition being studied.

Examples of who could join: Voluntary written informed consent of the participant has been obtained prior to any screening procedures. Patient is \>18 years of age. Patient is postmenopausal, as defined per local practice. Tumour size of ≥1 cm. The patient has a biopsy-confirmed diagnosis of GII-III ER+, HER2 - early stage breast cancer scheduled for primary surgery as per standard-of-care.

The full record lists 14 inclusion and 25 exclusion criteria; among the exclusions: have type 1 or 2 diabetes mellitus, history of ketoacidosis, or hyperosmolar state or coma; have a history of bc exceptions are made for:; contralateral in situ bc without systemic treatment.

How the Study Was Run

It was run as a randomized, parallel-group and open-label study.

The participants were allocated by chance, so the Tirzepatide group and the comparison group should start out alike.

The Tirzepatide group and the comparison group ran side by side rather than switching.

Being open-label, the Tirzepatide study did not mask who received what.

It started in 2026-08-01 with completion listed for 2028-03-01.

Its stated primary purpose is treatment.

What Was Measured

The main thing measured (primary outcome): Ki67 proliferation marker (time frame: From enrollment till time of surgery (4-5 weeks)).

It also tracked 5 secondary outcomes, for example Adherence, Adverse Event profile, Perioperative complications, ctDNA presence and ctDNA changes.

What This Means in Plain Language

Put simply, this is a phase 2, randomized trial of Tirzepatide in 168 people.

Its status is not yet recruiting; no results are posted to the registry yet, so nothing here describes outcomes.

More context: the Tirzepatide compound page, all human trials.