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Study of Daily Oral Ibutamoren Mesilate in Treatment‑Naïve Prepubertal Children with Growth Hormone Deficiency

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What is this trial about?

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

The study focuses on children who have Growth Hormone Deficiency (GHD), a condition where the body does not make enough growth hormone, leading to slower growth. The medication being tested is an oral capsule called LUM 201, which contains the active substance ibutamoren mesilate. The purpose of the study is to evaluate the effect of LUM 201 on growth rates over 12 months in prepubertal children with GHD.

Participants will be randomly assigned to receive either the LUM 201 capsule or a matching placebo capsule once each day for one year. The study is double‑blind, meaning neither the participants nor the researchers will know which treatment is being given until the study is completed. Throughout the 12‑month period, growth measurements and related health checks will be performed at regular visits to monitor safety and how well the medication works.

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

    Enrollment and Randomization

    On the first day of the study you are assigned to receive either ibutamoren mesilate or a matched placebo capsule. The assignment is done by a computer program so that neither you nor the study staff know which treatment you receive.

  2. Step 2

    Baseline Assessments

    Before starting the medication, a series of measurements are taken to record your initial condition. These include height measurement, blood tests for IGF-1 and IGFBP-3 levels, and a review of your medical history related to Growth Hormone Deficiency (GHD).

  3. Step 3

    Start Daily Medication

    You begin taking one oral capsule each day. The capsule contains ibutamoren mesilate at a dose of 1.6 mg per kilogram of body weight per day, or it contains a matching placebo if you were assigned to that group. The capsule is taken once daily at the same time each day for the entire 12‑month period.

  4. Step 4

    Monthly Clinic Visits

    You attend a clinic visit approximately every month for 12 months. At each visit the study staff measure your height, review any side effects, and collect blood samples to monitor IGF-1, IGFBP-3, and other safety parameters.

    The visit also includes a brief questionnaire about how you are feeling and any new health issues that have arisen since the previous visit.

  5. Step 5

    Safety Laboratory Tests

    During each monthly visit a small blood sample is taken to check liver function, kidney function, and hormone levels. These tests help ensure that the medication is not causing harmful effects.

  6. Step 6

    Growth Measurements

    Your height is measured at every monthly visit using a calibrated stadiometer. The measurements are used to calculate the annualized height velocity, which shows how quickly you are growing over time.

  7. Step 7

    Final Assessment at Month 12

    At the end of the 12‑month period a comprehensive evaluation is performed. Height, blood hormone levels, and safety laboratory results are compared with the baseline values to determine the overall effect of the treatment.

    You receive a summary of the study findings related to your participation.

  8. Step 8

    Study Completion

    After the final assessment you stop taking the study medication. No further study‑related procedures are required unless you choose to continue follow‑up care with your regular physician.

Who can join the trial?

12 criteria

  • Parents or legal guardians must sign a written informed consent form, and the child must agree to take part if they are old enough; everyone must be willing and able to follow all study steps.
  • The child must not have received any previous growth‑hormone treatment and must be prepubertal (stage I: no breast development in girls and testicular size less than 4 mL in boys).
  • In the past year the child must have had two growth‑hormone (GH) stimulation tests that showed a maximum GH level lower than 10 ng/mL; these tests check how the pituitary gland releases growth hormone.
  • The child’s height must be at least 2 standard deviations (about 2 × the average variation) below the normal height for their age and sex, according to World Health Organization growth charts.
  • The child must have a morning or random cortisol level of 7 µg/dL or higher; if it is lower, a special test that stimulates cortisol must be done and must reach at least 18 µg/dL.
  • The child’s age must be between 3 years and 10 years for girls, or between 3 years and 11 years for boys.
  • There must be a record of the child’s growth over at least 6 months showing a height‑growth speed (height velocity) that is below the 25th percentile for children of the same age and sex.
  • A bone age exam (X‑ray of the hand and wrist) must show that the child’s bone development is at least 12 months behind their actual age.
  • Girls must have genetic testing that rules out Turner syndrome and negative results for the SHOX gene test.
  • The child must have normal thyroid function (normal TSH and free T4 blood levels); if the child previously had hypothyroidism, the thyroid must have been normal for at least 3 months before the first study visit.
  • The child’s IGF‑1 (a hormone that reflects growth‑hormone activity) standard‑deviation score must be –1.0 or lower compared with normal values for their age and sex.
  • The child’s IGF‑1 level must be greater than 30 ng/mL and they must show a peak GH response of at least 5 ng/mL during the screening PEM test (a specific stimulation test).

Who cannot join the trial?

30 criteria

  • Any other medical or genetic problem that could cause short height on its own or make growth hormone treatment work less well, such as diabetes, unexplained short stature, SHOX gene deficiency, bone growth disorders, or other named syndromes.
  • Arm length compared to height that is much shorter than normal (more than 2 standard deviations below the average), which could indicate a hidden bone growth disorder called hypochondroplasia.
  • Having a medical or genetic condition that the doctor believes adds extra risk to using LUM-201.
  • Taking any medicine that the doctor thinks could cause short height by itself or reduce the effect of growth factors.
  • Current inflammatory diseases that required strong steroid pills (systemic corticosteroids) for more than 2 weeks in the last 3 months, or inhaled steroid use (like budesonide) at high doses for more than 4 weeks in the last year.
  • Using hormone replacement therapy for any hormone problem, except for a stable thyroid hormone deficiency.
  • Having an electrocardiogram (ECG) at screening that shows a significant heart rhythm problem, as confirmed by the medical monitor.
  • Any situation that would likely stop you from finishing the study.
  • Evidence of a past or present brain tumor, based on brain imaging before the first study visit.
  • Signs of increased pressure inside the skull (intracranial hypertension) confirmed by eye exam (fundoscopy) or other tests.
  • Blood tests showing liver enzymes (ALT, AST) or total bilirubin higher than the normal upper limit.
  • Having more than one hormone deficiency from the pituitary gland.
  • Having previously received growth hormones, IGF‑1, or other growth‑stimulating medicines (except for a short diagnostic test).
  • Evidence that the pituitary gland cannot produce enough growth hormone (stimulated level ≤ 3.0 ng/mL) or other pituitary hormone problems.
  • Severe malnutrition judged by the doctor from clinical exam, medical history, and lab results.
  • Body weight of 14 kg or less.
  • Body‑mass index (BMI) that is more than 2 standard deviations below or above the average for age and sex.
  • Birth weight that was below the 3rd percentile for the baby's age in the womb, according to WHO or local standards.
  • Having taken part in any other drug trial within the 6 months before the screening visit.
  • Known or suspected allergy to LUM-201, the placebo, or any of their inactive ingredients.
  • Not willing to accept being placed randomly into the study groups.
  • Taking medicines that strongly block or strongly increase the activity of liver enzymes called cytochrome P450 (CYP) 3A/4.
  • Taking medicines that are mainly broken down by specific liver enzymes (CYP3A/4, 2C8, 2C9, or 2C19) with little help from other enzymes.
  • Taking medicines that can lengthen the heart’s QT interval (a part of the heartbeat) or increase the risk of a dangerous rhythm called torsades de pointes.
  • Taking medicines that strongly inhibit the protein P‑glycoprotein (P‑gp), are strong substrates of P‑gp, or affect the multidrug and toxin extrusion protein 1.
  • History of radiation treatment to the spine, head, or whole body.
  • History of cancer or any current evidence that a tumor is growing.
  • Short height caused mainly by emotional or social factors (psychosocial short stature).
  • Having fully closed growth plates (epiphyses) in the bones.
  • Diagnosis of attention‑deficit/hyperactivity disorder (ADHD), no matter what treatment is used.
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Investigated drugs

Ibutamoren Mesylate is an oral capsule taken once each day. It is being studied as a potential treatment for children who have growth hormone deficiency. The medicine works by stimulating the body’s own growth‑hormone production, which may help children grow taller over time. In this study, children who have never been treated before will receive the medicine for 12 months, and researchers will check how quickly they grow and whether the medicine is safe to use. The drug is considered an orphan drug, meaning it is intended for a rare condition.

What is already known about the treatment

Ibutamoren Mesylate - This medication is taken as an oral capsule once a day, with the dose calculated by the child’s weight (about 1.6 mg per kilogram). It is still an investigational drug being studied in Phase 3 trials and is not yet approved for general medical use. The main purpose is to treat children who have growth hormone deficiency by helping them grow faster. It works by binding to the ghrelin (growth‑hormone‑secretagogue) receptor, which signals the pituitary gland to release more natural growth hormone, and it is classified as a growth‑hormone secretagogue or selective ghrelin receptor agonist.

Investigated diseases

Growth Hormone Deficiency - A condition in which the pituitary gland produces insufficient growth hormone, resulting in slower growth in children. In prepubertal patients, the rate of height increase is reduced and they fall further behind their peers. As the deficiency continues, height remains below expected levels and bone maturation may be delayed. The disorder can be present from birth or develop later in childhood. Without intervention, the short stature tends to persist.
Trial detailsLast updated 2 Nov 2026
Age0-17PhasePhase IIITrial ID2025-523820-26-01Protocol codeLUM-201-10Estimated enrolment144 patientsSponsorLumos Pharma LLC

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