Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not yet recruitingRare disease

Safety and tolerability study of S-241656 with posaconazole in patients with AML, MDS/AML or CMML

Verified siteRegistered drugNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

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

The study involves participants who have certain blood cancers, specifically Acute Myeloid Leukemia, Myelodysplastic Syndrome (often occurring together with AML) or Chronic Myelomonocytic Leukemia. These diseases affect the bone marrow’s ability to produce normal blood cells. The investigational medication is an oral tablet called S241656, which is being tested in two strengths (25 mg and 50 mg). In some participants the tablet will be taken together with the antifungal drug posaconazole, a strong CYP3A4 inhibitor that can change how other medicines are processed in the body.

The purpose of the study is to evaluate the safety and tolerability of S241656 when used alone and, optionally, when combined with posaconazole in the listed blood cancers. Participants will receive the study drug for several treatment cycles, with regular check‑ups that include physical examinations, laboratory tests, and monitoring for any side effects. In the optional part of the trial, participants will also take the antifungal medication for a short period to see how it influences the study drug. The trial follows a step‑wise design that starts with a low dose and may increase it if safety criteria are met, and participants may continue treatment as long as it remains safe and they choose to remain in the study.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline assessments

    After you join the study, you will undergo a series of baseline assessments that include a physical examination, collection of medical history, and laboratory tests such as blood work and bone‑marrow analysis to confirm eligibility and document the status of your disease.

    The results of these assessments establish a reference point for later comparison while you receive study medication.

  2. Step 2

    Start of part 1a monotherapy

    You will begin taking s241656 as a single oral tablet. the study provides tablets that contain either 25 mg or 50 mg of the active substance; the exact dose and any future adjustments are defined by the study protocol.

    The tablet is taken by mouth once daily, preferably at the same time each day, and you will continue this dosing throughout each treatment cycle.

    The first treatment cycle is typically 28 days long; during this period the study team closely monitors safety and tolerability.

  3. Step 3

    Monitoring during the first cycle

    Throughout the 28‑day cycle you will attend scheduled clinic visits where vital signs, physical condition, and any symptoms are recorded.

    Regular laboratory tests, including blood counts and chemistry panels, are performed to detect any changes that might indicate a dose limiting toxicity or other adverse event.

    If a serious side effect occurs, the study medication may be reduced, temporarily stopped, or discontinued according to the protocol.

  4. Step 4

    Optional part 1b with posaconazole

    After the initial safety evaluation, you may be offered the optional part 1b, in which you will take the antifungal drug posaconazole together with s241656.

    Posaconazole is taken orally, usually once daily, at a dose specified in the study protocol; its purpose is to assess how a strong CYP3A4 inhibitor affects the levels of s241656 in the bloodstream.

    You will continue to take both medications for several days until steady‑state concentrations are reached, after which additional blood samples are collected to measure drug levels.

  5. Step 5

    Subsequent treatment cycles

    If you remain eligible and no unacceptable toxicity occurs, you will start additional 28‑day cycles of s241656 (and posaconazole if you are in part 1b).

    Each new cycle repeats the same pattern of daily dosing, periodic clinic visits, and laboratory monitoring.

    The study protocol may allow dose adjustments, temporary interruptions, or permanent discontinuation based on safety findings.

  6. Step 6

    Assessment of response

    At predefined times, usually after several cycles, disease‑specific evaluations are performed to determine whether the leukemia or myelodysplastic syndrome has responded to treatment.

    Responses may include complete remission, partial remission, or other measures of disease control; these assessments are made by the study physicians using standard criteria.

  7. Step 7

    Treatment discontinuation

    Treatment may be stopped after a set number of cycles, if disease progression is observed, or if side effects become severe enough to outweigh potential benefit.

    The decision to discontinue is based on the safety and efficacy data collected during the trial.

  8. Step 8

    Post‑treatment follow‑up

    After the last dose of study medication, you will continue to attend follow‑up visits for a period defined by the protocol.

    These visits include physical examinations, laboratory tests, and disease assessments to monitor long‑term safety and any lasting effects of the treatment.

Who can join the trial?

13 criteria

  • Must be 18 years old or older.
  • Must have an Eastern Cooperative Oncology Group (ECOG) performance status of 2 or lower, which means you can carry out daily activities with only minor limitations.
  • Doctor must estimate that you have a life expectancy of at least 3 months.
  • You must be able and willing to follow all study requirements and visits.
  • If you are a woman who could become pregnant, you must use a highly effective birth‑control method as described in the study.
  • If you are a man and your partner could become pregnant, you must use a condom as described in the study.
  • You must have a confirmed diagnosis of Acute Myeloid Leukemia (AML), Myelodysplastic Syndrome that has become AML (MDS/AML), or Chronic Myelomonocytic Leukemia (CMML) that has relapsed or did not respond to prior treatment.
  • You must have already tried at least one approved standard therapy for your disease and have no other approved standard treatment options left.
  • Your disease must have been examined for genetic changes according to the usual practice at your treatment center.
  • Your white blood cell count must be less than 25 × 10⁹ per liter; doctors may use medicines such as hydroxyurea, cytarabine, or a procedure called leukapheresis to lower the count.
  • You must have adequate kidney function, measured as a creatinine clearance of at least 60 mL per minute (calculated with the Cockcroft‑Gault formula).
  • Your liver enzymes (AST and ALT) must be no more than three times the normal upper limit (or up to five times if you have leukemia).
  • Your total bilirubin level must be no more than 1.5 times the normal upper limit (or up to three times if you have Gilbert’s syndrome, a common harmless condition).

Who cannot join the trial?

22 criteria

  • Allergy: If you are known to have an allergic reaction (hypersensitivity) to the study drug S241656 or to posaconazole (used in part 1B), you cannot join.
  • Pregnancy or breastfeeding: Women who are pregnant, may become pregnant, or are nursing a baby are excluded. A positive pregnancy test also disqualifies a woman of child‑bearing potential.
  • Acute promyelocytic leukemia (FAB M3): This specific type of leukemia makes you ineligible.
  • Myeloproliferative neoplasm (MPN), mixed/ambiguous lineage disease, or histiocytic/dendritic cell cancers: These blood or immune‑cell cancers exclude participation.
  • AML with isolated extramedullary disease: If you have acute myeloid leukemia that is only outside the bone marrow (no marrow or blood involvement), you cannot join.
  • Active central nervous system (CNS) disease: Any current disease in the brain or spinal cord, shown by lab tests or imaging, is an exclusion.
  • Unresolved side effects from prior treatment: You must have recovered from earlier treatment toxicities to a mild level (grade 1). Ongoing moderate neuropathy or hair loss (grade 2) is allowed.
  • Recent major surgery: Any major operation performed within the last four weeks excludes you.
  • Recent anticancer therapy: No cancer treatments are allowed within two weeks before starting the study (or five drug half‑lives, which is about 28 days for biologic medicines). Certain low‑dose cytoreduction drugs are permitted.
  • Previous experimental KRAS/BRAF/MEK/ERK inhibitors: If you have taken these investigational drugs before, you cannot participate (previous FLT3 inhibitors are allowed).
  • Uncontrolled infections: Ongoing infections that are not under control exclude you, except for HIV, hepatitis B, or hepatitis C if the virus is undetectable and your immune cell count (CD4) meets specific criteria.
  • Malabsorption, Crohn’s disease, or chronic vomiting: Conditions that prevent the oral study drug from being absorbed properly make you ineligible.
  • History or risk of retinal vein occlusion, glaucoma, or hyper‑viscosity syndromes: Past eye blood‑vessel blockage, eye pressure disease, or blood that is too thick exclude participation.
  • Other active cancers: Any other cancer that needs systemic treatment within the past two years disqualifies you, except for non‑melanoma skin cancers or tumors that have been cured locally.
  • Recent serious heart problems: Stroke, heart attack, unstable chest pain (unstable angina), or acute coronary syndrome within the last six months are exclusions.
  • Moderate to severe heart failure: Congestive heart failure classified as New York Heart Association (NYHA) stage II or higher (moderate to severe) excludes you.
  • Significant heart rhythm disorders: Serious arrhythmias (abnormal heartbeats) such as ventricular tachycardia, complete left bundle branch block, high‑grade atrioventricular block (including Mobitz type II and third‑degree block) are not allowed.
  • Prolonged QT interval: A corrected QT interval (QTcF) longer than 470 milliseconds or a past episode of Torsades de pointes (a dangerous rapid heart rhythm) excludes participation.
  • Blood clotting problems: Disseminated intravascular coagulation (DIC), significant coagulopathy as judged by the investigator, or uncontrolled bleeding disqualify you.
  • Prohibited medications: Certain drugs must be stopped 7–14 days before the first dose of the study drug. This includes proton pump inhibitors and potassium‑competitive acid blockers, which must be stopped at least 7 days before.
  • Drugs that affect the study medication: Medicines that are sensitive to breast cancer resistance protein (BCRP) or P‑glycoprotein (P‑gp) transporters, especially those with a narrow therapeutic index (NTI), cannot be taken during the study.
  • Herbal supplements: All herbal preparations and dietary supplements are prohibited while participating.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

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

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not yet recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

  • S241656

    is an experimental oral tablet that is being tested as a single treatment for certain blood cancers, such as acute myeloid leukemia (AML), myelodysplastic syndrome that has turned into AML (MDS/AML), and chronic myelomonocytic leukemia (CMML). In the study, researchers are looking at how safe it is for patients to take this medicine on its own and how well their bodies tolerate it. The drug is taken by mouth and is being evaluated in different strengths, but the specific dose is not shown here.

  • Posaconazole

    is a medication that is normally used to prevent or treat fungal infections. In this trial, it is used not as a treatment for the cancer, but to see how a strong blocker of the enzyme CYP3A4 (which helps process many medicines) affects the way the body handles S241656. By giving participants posaconazole together with S241656, the study aims to understand whether the two drugs interact, whether the levels of S241656 change, and whether this combination remains safe for patients.

What is already known about the treatment

  • S241656

    This investigational drug is taken by mouth as a film‑coated tablet (available in 25 mg and 50 mg strengths). It is currently in early clinical testing and has not yet been approved or widely described in medical literature. The medication is being studied for the treatment of acute myeloid leukemia, myelodysplastic syndrome that has turned into AML, and chronic myelomonocytic leukemia, which are serious blood cancers. It works by blocking a key protein inside leukemia cells that helps them grow and survive, placing it in the class of experimental small‑molecule kinase inhibitors.

  • Posaconazole

    Posaconazole is an oral tablet (or liquid) that is swallowed and absorbed through the digestive system. It is an approved antifungal medicine used to prevent and treat serious fungal infections, and it is well known in medical references. In this trial it is used as a strong inhibitor of the enzyme CYP3A4 to see how it changes the levels of S241656 in the blood. The drug blocks a fungal enzyme called lanosterol 14α‑demethylase, stopping the production of ergosterol, a building block of fungal cell membranes, and it belongs to the triazole antifungal class.

Investigated diseases

  • Acute Myeloid Leukemia

    A cancer that starts in the bone marrow where blood cells are made. It causes a rapid increase of immature white blood cells that do not work properly. These abnormal cells crowd out normal blood cells, leading to low red cells, low platelets, and reduced immune function. The disease spreads from the marrow into the bloodstream and can involve other organs as it progresses.

  • Myelodysplastic Syndrome/Acute Myeloid Leukemia

    A disorder in which the bone marrow produces abnormal cells that fail to mature (myelodysplastic syndrome). Over time, the number of immature cells (blasts) can rise, transforming the condition into acute myeloid leukemia. As the disease advances, blood counts worsen and more immature cells appear in the blood. This progression reflects a shift from a chronic, low‑grade problem to a fast‑growing leukemia.

  • Chronic Myelomonocytic Leukemia

    A blood disorder characterized by an excess of monocytes, a type of white blood cell, produced in the bone marrow. The disease usually develops slowly, with increasing monocyte counts and mild changes in other blood cells. Over months or years it can evolve into a more aggressive leukemia, showing higher numbers of immature cells and broader marrow involvement. The condition therefore moves from a chronic phase to a potentially acute phase if the clone expands.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2025-525128-88-00Protocol codeS241656-292Estimated enrolment64 patientsSponsorInstitut De Recherches Internationales Servier IRIS

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.