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LIMIT Clinical Trial Studies the Effect of Metformin on the Progression of Abdominal Aortic Aneurysm
03.07.2023
The Division of Vascular and Endovascular Surgery at Stanford Medicine is leading a clinical trial to study the effects of metformin on the growth of abdominal aortic aneurysm (AAA). Metformin is a very common medication that treats type 2 diabetes.
The study, called Limiting AAA with Metformin Trial, or LIMIT, investigates whether the drug prevents the progression (enlargement) of AAAs. Stanford Medicine is currently accepting new patients for this clinical trial, which is funded by the National Heart, Lung, and Blood Institute. The study drug for the trial, as well as additional resources to track medication tolerance, are provided by EMD Serono, a U.S. affiliate of Merck KGaA
Benefits of the LIMIT clinical trial
The vascular surgery team at Stanford Medicine launched this nationwide clinical trial based on findings from earlier studies. The prior studies showed that people who had AAA and type 2 diabetes—and who were taking metformin to control diabetes—experienced less aneurysm disease progression compared to diabetic patients not taking metformin. A prescription for metformin, which was intended to lower blood glucose levels, was consistently associated with reduced rates of AAA enlargement in multiple retrospective studies.

Dr. Dalman
The LIMIT trial will prospectively study whether metformin significantly prevents the enlargement of existing AAAs in non-diabetic people. “This exciting study gives us the opportunity to evaluate the effects of this promising medication on a larger group of patients with AAA,” says Ronald Dalman, MD, vascular surgeon, the Walter C. and Elsa R. Chidester Professor of Surgery at Stanford Medicine, and principal investigator for the LIMIT trial. “Our findings will help determine whether metformin will be an appropriate treatment option for some patients with this life-threatening condition.”

Throughout the study, LIMIT trial participants will learn more about their blood chemistry, the type of AAA they have, and their overall health. Trial participation will extend over 24 months for each participant—the study itself will finish data collection in 2026. As a placebo-controlled trial, participants will be randomly assigned to take either a placebo pill or metformin. Participants taking metformin may see a reduction in the expected rate of aneurysm enlargement, depending on the state of disease.
Eligibility for the LIMIT research study
Participation in the LIMIT clinical trial is completely voluntary, and patients can withdraw from the study at any time. Patients may be eligible for the study if they:
- Are between 55 and 90
- Have a diagnosis of AAA with a maximum diameter of 4.9 cm for males or 4.5 cm for females
- Have not had a surgical procedure to repair AAA
- Do not have diabetes and are not taking any diabetic medication, including metformin
- Do not have the following conditions:
- Severe liver disease
- Jaundice
- Active hepatitis
- Uncontrolled hypertension (systolic blood pressure ≥ 200)
- Severe anemia (Hgb < 10g/dl)
Details of the LIMIT clinical trial
LIMIT study participants will complete five study assessments over a two-year period. At the baseline visit, patients are randomly assigned to the study drug group or the placebo group. Each participant will submit blood and urine samples, get a CT scan, complete a questionnaire, and receive the study drug. Participants will need to take one pill per day at first and gradually increase the dose, taking up to four pills per day, as tolerated. Some participants will take as little as one pill per day for the duration of the study.
Participants will complete follow-up assessments at six, 12, and 18 months. Some participants may be able to complete these follow-up assessments remotely, either by telephone or video visits. Participants completing in-person follow-up visits will submit blood and urine samples and receive additional supplies of the study drug. They will also complete questionnaires that inquire about their quality of life and other disease-specific issues.
During the study’s final visit at 24 months, patients will give blood and urine samples, return any unused study medications, and get another CT scan. They will also complete a questionnaire about their experience.
Learn more and refer your patients to the LIMIT study
Stanford Medicine encourages you to share information about this research study with your patients. To learn more about the LIMIT clinical trial, contact the study research coordinator, Lori McDonnell, at 650-498-5521 or lorimcd2@stanford.edu.
For additional information and complete eligibility requirements, please download the LIMIT trial brochure, visit the LIMIT clinical trial website, or learn more about the background information for this trial.
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Stanford Health Care seeks to heal humanity through science and compassion, one patient at a time, through its commitment to care, educate and discover. Stanford Health Care delivers clinical innovation across its inpatient services, specialty health centers, physician offices, virtual care offerings and health plan programs.
Stanford Health Care is part of Stanford Medicine, a leading academic health system that includes the Stanford University School of Medicine, Stanford Health Care, and Stanford Children’s Health, with Lucile Packard Children's Hospital. Stanford Medicine is renowned for breakthroughs in treating cancer, heart disease, brain disorders and surgical and medical conditions. For more information, visit: www.stanfordhealthcare.org.