Levofloxacin prophylaxis to reduce bloodstream infections in patients with hematologic malignancies undergoing allogeneic hematopoietic stem cell transplantation

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What is this study about?

Patients who receive an allogeneic hematopoietic stem cell transplantation for blood cancers such as acute leukemias, myelodysplastic syndromes, lymphomas, or for inherited immune disorders are at risk of serious infections because their immune system is very weak after the procedure. The study compares an antibiotic called levofloxacin with a harmless substance called placebo to see if taking the antibiotic can prevent infections that enter the bloodstream, known as bloodstream infection, during the period when white blood cells are low, called the neutropenic phase.

The main goal is to find out whether the antibiotic reduces the number of these infections in the first month after transplantation. Participants receive the study medication by IV or by mouth starting soon after the transplant and continue until their white blood cell counts recover, usually about 30 days. During and after this time they are monitored for signs of infection, fever, and other complications, and their health status is checked for up to a year to record any serious outcomes.

1 enrollment and baseline assessment

after agreeing to participate, basic health information and blood samples are collected to confirm eligibility for the study.

the purpose of these tests is to create a reference point before the preventive antibiotic treatment begins.

2 random assignment to treatment or placebo

the study uses a random process to decide whether the patient will receive levofloxacin (the active antibiotic) or a placebo (a solution that looks the same but contains no active drug).

the assignment is kept confidential, and the patient receives the same type of preparation regardless of the group.

3 start of intravenous prophylaxis

on the day of transplantation, an infusion is given through a vein.

if assigned to the active group, the infusion contains levofloxacin at a dose of 500 mg per day; if assigned to the placebo group, the infusion contains 900 mg of sodium chloride, which has no antibiotic effect.

the infusion is administered once daily and continues until the patient is able to take oral medication, typically during the first few days after transplantation.

4 switch to oral prophylaxis

once oral intake is possible, the patient begins a daily tablet.

the active tablet contains levofloxacin 500 mg taken once each day; the placebo tablet looks identical but contains no active ingredient.

the oral medication is continued for the entire neutropenic phase—the period of low white‑blood‑cell counts—up to 30 days after transplantation, or until blood counts recover, whichever occurs later.

5 regular monitoring and safety checks

the patient visits the clinic regularly for blood tests that check white‑blood‑cell levels and look for signs of infection.

temperature is measured each day, and any fever or new symptoms are reported to the study team promptly.

blood cultures may be taken if an infection is suspected, to determine whether bacteria are present in the bloodstream.

6 end of prophylactic treatment and final assessment

when the neutropenic phase ends or the 30‑day period is reached, the study medication (either levofloxacin or placebo) is stopped.

the patient undergoes a final set of tests to record any infections that occurred during the treatment period.

these results are used to compare the frequency of bloodstream infections between the two groups.

7 long‑term follow‑up

the patient continues to be followed for up to 12 months after transplantation to record overall survival and any infection‑related deaths.

additional clinic visits are scheduled at 100 days and at 12 months to collect this information.

Who Can Join the Study?

Be 18 years old or older, meaning you are an adult.
Be scheduled to receive an allogeneic hematopoietic stem cell transplantation (a treatment where stem cells from a donor are used to replace your own blood‑forming cells) at Helsinki University Hospital.
The transplant must be for a condition that is approved for this procedure, such as blood cancers (like acute leukemia, myelodysplastic syndrome, lymphoma) or inherited immune disorders (such as severe combined immunodeficiency or congenital immune dysregulation).
Be a patient (not a healthy volunteer); both males and females are allowed to join.

Who Cannot Join the Study?

Known hypersensitivity (allergy) to fluoroquinolone antibiotics such as levofloxacin.
Having epilepsy or any other known seizure disorder.
Having Long‑QT syndrome, a heart rhythm condition that can cause dangerous fast heartbeats.
Having an acquired prolonged QT‑time (measured on an ECG as cQT > 500 ms), which is another heart rhythm problem.
Having a history of tendinopathy (pain, inflammation, or rupture of a tendon) while taking a fluoroquinolone antibiotic.
Being pregnant or breastfeeding.
Any other known contraindication (reason not to use) to levofloxacin or other fluoroquinolone antibiotics.

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Hchpbgnp Uclidqymwk Chshqhp Hkudhmpo	Helsinki	Finland

Trial status

Country	Status	Recruitment Start
Finland	Not yet recruiting	05.10.2026

Trial locations

Investigated Drugs:

Levonic is an intravenous (IV) solution that contains the antibiotic levofloxacin. In the study it is given through a vein to provide a strong, rapid dose of the medicine that can help prevent bacterial infections during the period when the patient’s immune system is very weak after a stem cell transplant.

Levofloxacin (taken by mouth) is the same antibiotic used in the IV form, but it is given as a tablet or liquid that the patient swallows. This oral version is also tested to see if it can safely prevent bloodstream infections during the same low‑immune‑cell period after transplantation.

Investigated Diseases:

Acute leukemia – a fast‑growing cancer of the blood‑forming cells in the bone marrow. It causes a rapid increase of abnormal white blood cells that crowd out normal cells. Patients develop low blood counts, leading to fatigue, easy bruising, and infections. The disease can spread to the blood and other organs as it progresses.
Myelodysplastic syndrome – a group of disorders where the bone marrow produces poorly formed blood cells. Over time, the number of healthy blood cells falls, causing anemia, low platelets, and susceptibility to infection. The condition can become more severe and may evolve into acute leukemia.
Lymphoma – a cancer that starts in the lymphatic system, which includes lymph nodes and other immune tissues. Abnormal lymphocytes grow and form tumors that can enlarge lymph nodes or affect organs such as the spleen. As it advances, the disease can spread beyond the lymphatic system.
Severe combined immunodeficiency – a genetic disorder in which both T‑cell and B‑cell immune functions are severely impaired. Affected infants cannot fight off common infections, leading to frequent, serious illnesses. Without functional immune cells, the condition worsens as infections accumulate.
Congenital immune dysregulation syndrome – an inherited condition where the immune system is unable to regulate its responses properly. Patients may experience uncontrolled inflammation and autoimmunity, along with recurrent infections. Over time, the imbalance can lead to organ damage.
Other inherited immunodeficiency disorders – a range of genetic diseases that weaken the immune system in various ways. They often result in repeated infections and may affect different immune cell types. The severity can increase as the body fails to clear pathogens effectively.

Trial ID:

2025-524982-25-00

Protocol code:

FLG-L03

Trial Phase:

Therapeutic confirmatory (Phase III)

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Levofloxacin prophylaxis to reduce bloodstream infections in patients with hematologic malignancies undergoing allogeneic hematopoietic stem cell transplantation

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