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Phase 1/2 Study of LB-208 in Adults with Relapsed or Refractory Acute Myeloid Leukaemia and High‑Risk Myelodysplastic Syndrome

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What is this trial about?

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

The study examines adults whose blood cancers have either returned after treatment or have not responded to standard therapy, specifically those with relapsed or refractory acute myeloid leukaemia (AML) and relapsed or refractory myelodysplastic syndrome (MDS). The investigational medicine is LB-208, an oral capsule that blocks a protein called serotonin 5‑hydroxytryptamine receptor 1B (HTR1B), which helps the cancer cells grow. The purpose of the study is to evaluate the safety of the drug and to identify a dose that can be used in later trials.

Participants will take the study drug by mouth each day while doctors regularly check for side effects, collect blood samples, and monitor how the medicine moves through the body. Any serious side effects that limit the amount of drug that can be given (dose‑limiting toxicity) are recorded, and doctors look for signs that the disease is responding using accepted criteria. The study continues until sufficient information on safety and appropriate dosing is gathered.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline assessment

    After joining the study you will undergo a baseline assessment that includes medical history, physical examination, and laboratory tests to determine your current health status.

    These assessments help the study team understand your condition before starting the medication.

  2. Step 2

    Receive study medication

    You will be given lb-208 capsules, which are taken by mouth (oral route).

    The dosage amount and strength are determined by the study protocol and will be written on the medication label.

  3. Step 3

    Start medication

    You will begin taking the medication continuously as a single agent, meaning you will take it every day without interruption unless instructed otherwise.

    The capsules are taken according to the schedule provided, typically once daily, but follow the exact instructions given to you.

  4. Step 4

    Regular safety monitoring visits

    You will attend clinic visits at regular intervals (for example weekly or as specified) where blood samples are taken and your health is reviewed.

    The study team will check for any adverse events (side effects) and assess their severity using standard criteria.

  5. Step 5

    Dose evaluation and possible adjustment

    If a dose limiting toxicity (a side effect that prevents further increase of the dose) is observed, the dose may be reduced or the medication paused.

    Any changes to the dose will be explained to you and recorded.

  6. Step 6

    Continuous treatment period

    You will continue the medication for the duration of the study unless disease progression, unacceptable side effects, or a decision to stop treatment occurs.

    During this period regular monitoring continues as described in step 4.

  7. Step 7

    End of treatment assessment

    When treatment ends, a final assessment is performed to evaluate your response to the medication and to record any lasting side effects.

    The results may be used to help determine the recommended dose for future studies.

Who can join the trial?

12 criteria

  • Give your informed consent (sign a form showing you understand the study) before any study procedures are done.
  • You must be able to understand the consent information and be willing to sign it.
  • You must be 18 years old or older when you sign the consent.
  • You need a life expectancy of at least 3 months (the doctors expect you to live for three more months or longer).
  • You must have a type of blood cancer called relapsed or refractory acute myeloid leukaemia (AML) or higher‑risk myelodysplastic syndrome (MDS), diagnosed by standard tests and judged by your doctor to need new treatment.
  • You must agree to have repeated bone marrow (BM) biopsies, peripheral blood (PB) tests, and urine tests during the study. A bone marrow biopsy is a small sample taken from inside your hip bone to check the disease.
  • Your overall health must be good enough to have an ECOG performance status of 0 to 2 (a scale doctors use to rate how well you can carry out daily activities, where 0 is fully active and 2 means you are up and about but unable to work).
  • Your platelet count (cells that help blood clot) must be at least 20,000 per microliter. If needed, you may receive transfusions to reach this level.
  • Your liver must be working well enough, shown by blood tests for AST, ALT and alkaline phosphatase (ALP) that are no more than three times the normal upper limit, unless the disease itself is affecting those numbers.
  • Your kidneys must work well enough, shown by a serum creatinine level no higher than 2.0 mg/dL or a creatinine clearance greater than 40 mL/min (a calculation that estimates how well the kidneys filter waste).
  • If you are a woman who could become pregnant, you must have a negative serum pregnancy test within 7 days before starting the medication.
  • Women who could become pregnant, as well as men who can father children and their partners, must agree to use a highly effective form of contraception or avoid sex during the study, and continue using contraception for 90 days after the last dose for men and for 6 months after the last dose for women. Men must also not donate sperm while taking the drug and for 3 months after stopping it.

Who cannot join the trial?

19 criteria

  • Have had a stem cell transplant (called HSCT) within the last 60 days, are taking medicines that suppress the immune system after the transplant, or have serious graft‑versus‑host disease (GVHD), which is when donor cells attack the patient's body (skin steroid creams are allowed).
  • Received regular cancer chemotherapy or radiation (except the drug hydroxyurea) less than 14 days before the first dose of the study medication.
  • Taken another experimental drug less than 14 days before the first dose, and must wait until at least five times the drug’s half‑life has passed (the time it takes for half of the drug to leave the body).
  • Have a treatment option that could cure the disease, making the study drug unnecessary.
  • Are taking medicines that strongly affect the liver enzymes CYP 2B6 or CYP 2C8, which could cause unsafe drug interactions.
  • Are pregnant or are breastfeeding.
  • Have an active severe infection or an unexplained fever higher than 38.5 °C (101 °F) at screening or on the first day of medication (a fever caused by the tumor may be allowed).
  • Are allergic (hypersensitive) to any part of the study drug LB‑208.
  • Have moderate or severe heart failure (classified as New York Heart Association Class III or IV) or a left‑ventricular ejection fraction (LVEF) below 40%, which means the heart pumps poorly.
  • Had a heart attack (myocardial infarction) within the past 6 months.
  • Have unstable or uncontrolled chest pain from heart disease (angina pectoris).
  • Have a known history of dangerous rapid heart rhythms from the lower chambers of the heart (ventricular arrhythmias).
  • Have a heart‑rate‑corrected QT interval (called QTc) of 470 milliseconds or more, or have other conditions that raise the risk of QT prolongation such as heart failure, low blood potassium (hypokalaemia), or a family history of long QT syndrome.
  • Are taking medicines that can lengthen the QT interval unless those medicines can be stopped permanently or replaced before the first dose, with a washout period of at least five drug half‑lives.
  • Are infected with HIV, have active hepatitis B or C, or have any other serious systemic infection rated grade 2 or higher.
  • Have any other medical or psychological condition that the doctor believes will make it difficult to give consent, follow study instructions, or take part in the trial.
  • Have difficulty swallowing (dysphagia), short‑gut syndrome, gastroparesis, or other problems that would prevent the oral medication from being absorbed.
  • Show signs of leukemia in the brain or spinal fluid (called central nervous system (CNS) leukemia) or have symptoms that suggest it.
  • Have life‑threatening severe leukemia complications such as uncontrolled bleeding, pneumonia with low oxygen levels, shock, or disseminated intravascular coagulation (a serious clotting disorder).
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Investigated drugs

LB-208 is a medicine that blocks a specific serotonin receptor called 5‑hydroxytryptamine 1B. It is taken by mouth in a hard capsule. In this trial the drug is given continuously as the only treatment to adults with acute myeloid leukaemia or higher‑risk myelodysplastic syndrome that has returned or has not responded to earlier therapy. The study is looking at how safe the medicine is, how well patients can tolerate it, and what the highest dose can be without causing serious side effects, so that the right dose can be used in later studies.

What is already known about the treatment

LB-208 - LB-208 is taken by mouth in a hard capsule form and is currently an investigational drug being studied in a Phase 1/2 clinical trial. It is being tested for people whose acute myeloid leukemia (AML) or high‑risk myelodysplastic syndrome (MDS) has come back or did not respond to other treatments. The medicine works by blocking the serotonin 5‑hydroxytryptamine (5‑HT) 1B receptor, which interferes with signals that help cancer cells grow and survive. Pharmacologically, LB-208 is classified as a selective serotonin 5‑HT1B receptor antagonist.

Investigated diseases

  • Acute Myeloid Leukemia (relapsed or refractory)

    Acute Myeloid Leukemia is a blood cancer where the bone marrow makes abnormal immature white cells. In the relapsed form, the disease returns after a period of improvement; in the refractory form, it does not respond to initial therapy. The abnormal cells multiply and crowd out normal blood cells, leading to reduced red cells, platelets, and healthy white cells. Over time, the marrow becomes increasingly filled with these immature cells, causing worsening blood counts. The disease may spread to the spleen, liver, or other tissues as the abnormal cells accumulate. This ongoing growth characterizes its progression.

  • Higher‑risk Myelodysplastic Syndrome (relapsed or refractory)

    Myelodysplastic Syndrome is a condition where the bone marrow produces poorly formed blood cells. In higher‑risk cases, the abnormal cells increase in number and the risk of progressing to acute leukemia is greater. When the disease relapses, the abnormal cell count rises again after a period of improvement; if it is refractory, the condition does not improve with treatment. The marrow becomes more crowded with defective cells, leading to worsening anemia, low platelets, and low neutrophils. Over time, the blood cell deficits become more pronounced, and the marrow environment continues to change. This pattern reflects the disease’s natural course.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase ITrial ID2025-523396-38-00Protocol codeLB208-1-002Estimated enrolment60 patientsSponsorAop Orphan Pharmaceuticals GmbH

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