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A study of hydroxyurea added to standard drug combination to assess safety and effectiveness in adults with relapsed or refractory acute myeloid leukemia

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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study involves adults whose acute myeloid leukemia has returned after previous therapy or has not responded to earlier treatment. The standard rescue regimen used for this condition includes the chemotherapy agents fludarabine, cytarabine, idarubicin and the targeted drug venetoclax. The trial adds the oral medication hydroxyurea to this combination in an effort to improve results.

The purpose of the study is to find out whether adding hydroxyurea to the rescue regimen is safe and can lead to better outcomes. Participants will receive the set of drugs in several treatment cycles, with infusions given through a vein and oral tablets taken at home. Throughout the treatment period and during follow‑up visits, blood tests and other routine checks will be performed to monitor health and response.

During the trial, doctors will closely watch for side effects such as low blood counts, infections, or organ problems, and will record any signs that the leukemia comes back. The study will measure how many patients stay free of disease for at least one year after starting the combined therapy.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

Step 1
Initial evaluation
After joining, baseline blood work and health checks are performed to confirm eligibility for the study.
The study doctor explains the treatment plan, including the medicines that will be given.
Step 2
Start of treatment cycle 1
On day 1, an infusion of idarubicin is given through a vein over a short period.
On day 1, a dose of fludarabine is given as an infusion, usually once daily for several days as directed.
On day 1, an infusion of cytarabine (also called ara‑c) is started, typically given once daily for a set number of days.
On day 1, oral tablets of venetoclax are taken each day, following the schedule given by the study doctor.
In addition, oral hydroxyurea tablets are taken each day at a dose level that is being tested; the first dose level is low and may be increased later in the study.
Step 3
Subsequent treatment cycles
After a rest period, the same group of medicines is given again for the next cycle, following the same order and route.
The dose of hydroxyurea may be adjusted to a higher level if the first level is well tolerated.
Each cycle repeats the infusions of idarubicin, fludarabine, and cytarabine, and the daily oral doses of venetoclax and hydroxyurea for the number of days specified by the study protocol.
Step 4
Monitoring and safety assessments
Blood counts and other laboratory tests are performed regularly to check how the body is responding and to detect any side effects.
The doctor records any adverse events, such as fever, low blood counts, or other symptoms, and may adjust treatment if needed.
If severe toxicity occurs, the dose of the study medicines may be reduced or treatment may be paused.
Step 5
End of treatment and follow‑up
When the planned number of cycles is completed, treatment stops and the patient enters a follow‑up period.
Periodic visits are scheduled to assess disease status, overall survival, and any long‑term side effects.
The primary outcome measured is the 1‑year event‑free survival, which means the time from the start of treatment until disease progression, relapse, or death.

Who can join the trial?

14 criteria

Be 18 years old or older.
Have a diagnosis of acute myeloid leukemia (AML) that is either:
- Refractory – meaning the disease did not improve after at least one cycle of strong chemotherapy, with more than 10% abnormal cells (called “bone marrow blasts”) still present, or no complete remission after two cycles.
- Relapsed – meaning the disease has come back, including spread outside the bone marrow, according to the 2022 ELN criteria (a set of medical guidelines).
- Showing measurable residual disease (MRD) of 5% or higher, detected by validated genetic tests or special blood‑cell analysis called multiparameter flow cytometry.
- Give written permission (signed consent) to join the study and be able to understand what the study involves.
- Have an ECOG Performance Status of 2 or lower (a simple scale that measures how well a person can carry out daily activities; 0 = fully active, 2 = able to care for oneself but unable to work).
- Show adequate kidney and liver function, demonstrated by:
  - Creatinine clearance ≥ 30 mL/min (a test that estimates how well the kidneys filter waste, calculated with the Cockcroft‑Gault formula).
  - Serum bilirubin ≤ 3 times the upper limit of normal (ULN) unless due to a harmless condition called Gilbert’s syndrome (bilirubin is a substance processed by the liver).
  - Alanine aminotransferase (ALT) ≤ 5 times ULN (ALT is an enzyme that rises when the liver is stressed).
  - Be considered fit enough to receive intensive chemotherapy (strong cancer‑killing drugs).
  - If male, agree to use a latex condom with any female partner who could become pregnant, avoid fathering a child during treatment and for 6 months after the last dose, and ensure the partner uses a highly effective birth‑control method.
  - If male, agree not to donate sperm from the time of screening through the study and for 6 months after the last dose.
  - If female and not able to become pregnant, be either postmenopausal (no periods for at least one year) or have had surgical sterilization before screening.
  - If female and able to become pregnant, agree to avoid pregnancy during the study and for 6 months after the last dose, have a negative pregnancy test at screening, and use a highly effective birth‑control method together with a barrier method (such as a condom) throughout the study and for 6 months afterward.

Who cannot join the trial?

15 criteria

Having acute promyelocytic leukemia, a special type of blood cancer that is different from the one being studied.
Being 75 years old or older.
Being known to be intolerant (unable to tolerate) any of the chemotherapy drugs used in the study.
Having a positive pregnancy test.
Being a nursing mother or a woman who could become pregnant and is not using reliable birth control.
Having an inherited bone‑marrow failure disorder such as Fanconi anemia or Dyskeratosis congenita (genetic conditions that affect the production of blood cells).
Having a history of not following medical instructions or being considered unreliable for taking study medication.
Having a white blood cell count (WBC) of 30 × 10⁹/L or higher before treatment (a very high level of blood cells).
Having a TP53 double hit mutation or biallelic TP53 inactivation (a specific genetic change that makes the disease harder to treat).
Having leukemia that has spread to the central nervous system (CNS), which includes the brain and spinal fluid.
Relapsing (cancer returning) within three months after receiving an allogeneic stem‑cell transplant (allo‑HCT).
Having an infection that cannot be controlled.
Having an ECOG Performance Status greater than 2 (meaning the person is unable to carry out most daily activities).
Having severe failure of a major organ (such as heart, liver, or kidneys) that would prevent safe delivery of the chemotherapy.
Having serious heart problems, including any of the following: a heart attack (myocardial infarction) in the past three months; a weakened left side of the heart with an ejection fraction below 50% (a measure of how well the heart pumps blood); unstable chest pain (unstable angina); advanced heart failure classified as NYHA class III or IV (significant shortness of breath and limited activity); or dangerous irregular heart rhythms (arrhythmias).

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Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Karolinska University Hospital
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Solna, Sweden
Queen Silvia Childrens Hospital - Sahlgrenska University Hospital - Vaestra Goetalandsregionen
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Gothenburg, Sweden
Uppsala University Hospital
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Uppsala, Sweden

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Investigated drugs

Hydroxyurea
is an oral medication that slows down the production of blood cells. In this study it is added to the standard chemotherapy plan to see if it can help control the leukemia better and improve patients’ chances of staying disease‑free.
Fludarabine
is a chemotherapy drug given through an IV infusion. It works by interfering with the DNA inside cancer cells, which makes it harder for the cells to grow and divide. It is one of the main drugs used in the salvage treatment for relapsed or refractory leukemia.
Cytarabine
(also called Ara‑C) is a chemotherapy agent administered by IV infusion. It looks like a building block of DNA, so when cancer cells try to use it, they make faulty DNA and die. It is a key part of the intensive chemotherapy regimen in this trial.
Idarubicin
is an anthracycline chemotherapy drug given by IV infusion. It slides into the DNA of cancer cells and stops them from copying their genetic material, leading to cell death. It is combined with the other drugs to attack the leukemia from several angles.
Venetoclax
is an oral tablet that targets a protein called BCL‑2, which helps cancer cells survive. By blocking this protein, venetoclax encourages the leukemia cells to die. In the study it is used together with the other chemotherapy drugs to improve treatment effectiveness.

What is already known about the treatment

Venetoclax
This medication is taken as a film‑coated tablet taken by mouth. It is an approved drug for certain blood cancers such as chronic lymphocytic leukemia and acute myeloid leukemia and is widely described in medical literature. Venetoclax works by blocking a protein called BCL‑2, which helps cancer cells survive, thereby allowing them to die. It belongs to the class of targeted therapies known as BCL‑2 inhibitors.
Idarubicin hydrochloride
Idarubicin is given as an injection that is slowly infused into a vein. It is a standard chemotherapy drug used for acute myeloid leukemia and is well documented in clinical practice. The drug inserts itself between DNA strands and stops an enzyme called topoisomerase II, preventing cancer cells from copying their DNA. It is classified as an anthracycline antibiotic chemotherapy agent.
Fludarabine phosphate
Fludarabine is supplied as a solution for injection and is administered by intravenous infusion. It is approved for chronic lymphocytic leukemia and is also used in salvage regimens for acute myeloid leukemia. The drug mimics a building block of DNA, disrupting DNA synthesis and leading to cell death. It falls under the antimetabolite class of chemotherapy agents.
Hydroxycarbamide
Hydroxycarbamide (hydroxyurea) comes in hard capsules taken orally. It is an established medication for conditions such as sickle cell disease, chronic myeloid leukemia, and is being studied for acute myeloid leukemia. It blocks an enzyme called ribonucleotide reductase, which reduces the production of DNA building blocks and slows cell growth. This drug is classified as a ribonucleotide reductase inhibitor, a type of antimetabolite.
Cytarabine
Cytarabine is provided as a liquid that is given by intravenous infusion. It is a cornerstone chemotherapy for acute myeloid leukemia and is described in many treatment guidelines. The drug acts as a fake piece of DNA, gets incorporated into the cancer cell’s DNA and stops the strand from being extended, causing cell death. It is categorized as a pyrimidine antimetabolite chemotherapy agent.

Investigated diseases

Acute myeloid leukemia - Acute myeloid leukemia is a fast‑growing cancer that starts in the bone marrow and produces abnormal myeloid cells. These immature cells crowd out normal blood‑forming cells, leading to reduced red cells, white cells, and platelets. As the disease advances, patients may experience fatigue, increased infections, and easy bruising or bleeding. In some adults the disease returns after initial treatment (relapsed) or does not respond to standard therapy (refractory). The condition can progress from an initial diagnosis to a state where the abnormal cells dominate the marrow and blood.