Safety and Tolerability of Metformin in Patients with Idiopathic Pulmonary Fibrosis: A Randomized Placebo‑Controlled Phase II Study

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What is this study about?

The study focuses on Idiopathic Pulmonary Fibrosis, a condition in which scar tissue forms in the lungs without a known cause, making breathing harder over time. Participants will receive either the medication metformin, a drug commonly used for diabetes but being tested for its safety and how well it is tolerated in this lung disease, or a harmless tablet called placebo that looks the same but contains no active ingredient.

The main goal is to see whether metformin changes a specific blood marker that reflects lung tissue activity compared with placebo. After random assignment, participants will take the assigned tablets daily for about three months. Throughout the study they will attend regular visits where simple blood samples are taken, breathing tests are performed to measure how much air the lungs can hold and move, and a short walking test is done to check exercise ability. The study is conducted in a way that neither the participants nor the study staff know which tablet is being taken, helping to keep the results unbiased.

1 randomization and baseline assessments

after joining the study you will be randomly assigned to receive either metformin or a placebo tablet. the assignment is done by a computer and you will not know which one you receive.

at this visit the study team will collect blood samples, perform lung function tests, measure exercise capacity with a six‑minute walking test, and ask you to complete questionnaires about your symptoms and quality of life.

2 start of medication

once randomization is complete you will begin taking the study medication every day by mouth.

if you are in the metformin group you will take a total of 1500 mg of metformin hydrochloride each day, usually divided into the tablets provided. the placebo group will take tablets that contain no active drug (0 mg).

3 daily medication intake

you will swallow the tablet(s) with water at roughly the same time each day. the medication is taken orally and does not require any special preparation.

4 regular clinic visits during the 12‑week treatment period

you will attend scheduled visits approximately every four weeks (at week 4, week 8, and week 12). during each visit the study staff will:

check for any side effects or adverse events
repeat blood tests to monitor safety
perform lung function measurements (such as forced vital capacity and total lung capacity)
repeat the six‑minute walking test
ask you to fill out the same questionnaires used at baseline

5 end of the 12‑week treatment period

after twelve weeks of taking the study medication you will stop taking the tablets. the final dose will be taken on the last day of the treatment period.

6 post‑treatment follow‑up

for four weeks after the last dose you will continue to be monitored. during this time you may have additional phone calls or visits to report any new symptoms and to have safety blood tests performed.

7 study completion

at the end of the follow‑up period the study is concluded for you. all collected data will be used to evaluate the safety and tolerability of metformin compared with placebo in patients with idiopathic pulmonary fibrosis.

Who Can Join the Study?

Be older than 40 years.
If you are a woman who could become pregnant, you must have a negative highly sensitive pregnancy test before joining.
Women who could become pregnant must agree to use effective birth control methods during the study and until the medication is stopped.
Have a confirmed diagnosis of idiopathic pulmonary fibrosis based on the accepted ATS/ERS Consensus Guidelines (medical standards for this disease).
Show a Forced Vital Capacity (FVC) greater than 50% of the predicted normal value – this is a breathing test that measures how much air you can exhale forcefully.
Show a Diffusion Capacity for carbon monoxide (TLCO) greater than 25% of the predicted normal value – this test checks how well oxygen moves from your lungs into your blood.
Have a blood oxygen level (pO2) higher than 60 mm Hg while at rest, while using no more than 2 liters per minute of supplemental oxygen.
Have a blood oxygen level (pO2) higher than 60 mm Hg during exercise, while using no more than 6 liters per minute of supplemental oxygen.
Have been receiving standard care (including the medication Nerandomilast) for at least 3 months, or if you stopped standard care, you must have been off that therapy for at least 4 weeks.
Sign a written informed consent form indicating you understand the study.
Be able and willing to follow all study procedures.

Who Cannot Join the Study?

Any recent worsening of lung symptoms or a respiratory infection within the last four weeks (exacerbation or infection).
Any recent heart attack in the last four weeks, whether a NSTEMI (non‑ST‑segment elevation) or STEMI (ST‑segment elevation) type.
Having known bronchial asthma.
A past episode of lactic acidosis (dangerously high acid levels from lactic acid) or any other acute metabolic acidosis (sudden acid buildup in the body).
Having type I or type II diabetes mellitus.
Being enrolled in another clinical trial that uses an experimental treatment.
Having taken other experimental medicines that could cause overlapping toxicity within a period based on the drug’s half‑life (the time it takes for half of the drug to leave the body).
History of alcohol or drug abuse in the past year, or drinking alcohol during the trial.
If the doctor believes you are unlikely to follow the study’s procedures, limits, and requirements.
Allergy (hypersensitivity) to the study drug or any of its ingredients such as Povidone K30, highly dispersed silicon dioxide, magnesium stearate, hypromellose, titanium dioxide, macrogol 400, lactose, cellulose powder, microcrystalline cellulose, or red iron oxide.
Use of contrast agents (dye used in imaging tests) within the past 48 hours.
Having emphysema affecting more than 10 % of lung volume as shown on a High Resolution Computed Tomography (HRCT) scan.
Any acute condition that could harm kidney function, such as severe dehydration, serious infection, or shock.
Diseases that can cause low oxygen in body tissues (tissue hypoxia), including severe (decompensated) heart failure, a recent heart attack, shock, or worsening breathing failure in the last four weeks.
Taking medicines that block or increase the activity of the transport proteins OCT1 or OCT2, except for the drug nintedanib.
Inherited conditions like hereditary galactose intolerance, lactase deficiency (difficulty digesting lactose), or glucose‑galactose malabsorption.
Being pregnant or breastfeeding.
Having chronic obstructive pulmonary disease (COPD) with a lung function ratio FEV1/FVC less than 70 %.
Having an active malignant disease (cancer) that requires treatment.
An estimated life expectancy of less than one year for any reason.
Significant kidney problems, defined as a glomerular filtration rate (GFR) below 60 % of the predicted value or a blood creatinine level higher than 2 mg/dL.
Advanced liver cirrhosis beyond the Child‑A stage.
Any other liver disease with liver enzymes (AST/ALT) more than three times the normal upper limit.
Any acute or chronic heart failure with an ejection fraction (the percentage of blood the heart pumps out) less than 40 %.

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

Site Name	City	Country
Justus-Liebig-Universitaet Giessen	Giessen	Germany
Klinikum der Universitaet Muenchen AöR	Munich	Germany
Thoraxklinik Heidelberg gGmbH	Heidelberg	Germany

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
Germany	Not yet recruiting	01.12.2026

Trial locations

Investigated Drugs:

Metformin is an oral tablet that is normally used to help control blood sugar in people with diabetes. In this study, researchers are giving metformin to patients with idiopathic pulmonary fibrosis (IPF) to see if it is safe and well‑tolerated when taken for 12 weeks. They will compare the results with a group that receives a placebo, looking at changes in a specific blood marker (PRO‑C3) that may reflect the activity of the lung disease. The goal is to find out whether metformin could be helpful for people with IPF.

Investigated Diseases:

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis – A chronic lung condition in which the tissue surrounding the air sacs becomes thickened and scarred without a known cause. The scarring makes the lungs stiff, reducing their ability to expand fully during breathing. Over time, patients typically notice increasing shortness of breath and a persistent dry cough. The disease progresses gradually, leading to a steady decline in lung function.

Trial ID:

2025-523341-10-00

Protocol code:

KKS-329

Trial Phase:

Therapeutic exploratory (Phase II)

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Safety and Tolerability of Metformin in Patients with Idiopathic Pulmonary Fibrosis: A Randomized Placebo‑Controlled Phase II Study

What is this study about?

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