A Research Study of How Well Macimorelin Works to Find Out if Children Have a Lack of Growth Hormone and How Safe it is

Each study participant (patient) will have 5 to 6 visits in total with the study doctor.

The study will last for about 1 to 4 months, dependent on how close the visits are done. At the visits 2, 3, 4 and 5, the patient will get a stimulation test done and blood samples will be taken. At those 4 visits, the patient will have either to drink a macimorelin drink, take some clonidine tablets or get an arginine infusion. In total, the patient will get 2 macimorelin, 1 clonidine and 1 arginine test done. The level of growth hormone (GH) will be measured 4 times during the clonidine and during the arginine test and 5 times during the macimorelin test. After the test, questions on the test tolerability will be captured from patients and parents. After the arginine test, a urine dipstick test is to be done by the patient at home.

Inclusion criteria

• Informed consent of subject, parent(s) or legally acceptable representative (LAR) of subject and child assent, if appropriate, must be obtained before any trial-related activities. Trial-related activities are any procedures that are carried out as part of the trial, including activities to determine suitability for the trial.
• Male and female pediatric subjects from 2 to less than 18 years of age at the time of signing informed consent.
• Indication for the performance of growth hormone stimulation test.
• Presence of a height measurement minimum 6 and maximum 18 months prior to screening.

Exclusion criteria

• Established diagnosis of a disease that is sufficient to explain growth deficiency or metabolic disorders that are also associated with short stature (e.g., Turner syndrome, skeletal dysplasia's, celiac disease, etc.).
• Ongoing growth hormone therapy.
• Presence of hypothyroidism and/or adrenal insufficiency without adequate and stable replacement therapy treatment for at least 30 days prior to first GHST.
• Treatment with drugs directly affecting the pituitary secretion of somatotropin (e.g., somatostatin analogues, clonidine, levodopa and dopamine agonists) or provoking the release of somatostatin (antimuscarinic agents e.g., atropine).
• Medical history of ongoing clinically symptomatic psychiatric disorders.
• 2nd or 3rd degree atrioventricular-block, prolongation of the QRS complex over 120 milliseconds, prolongation of the QTc interval over 450 milliseconds, or any other clinically significant abnormal electrocardiogram results at the V2 pre-dose electrocardiogram (ECG) as judged by the investigator.
• Previous participation in this trial. Participation is defined as signed informed consent.
• Participation in any clinical trial of an approved or non-approved investigational medicinal product within 30 days before screening.
• Known or suspected hypersensitivity to trial product(s) or related products;
• Any disorder, which in the investigator's opinion might jeopardize subject's safety or compliance with the protocol.
• Concomitant treatment with any drugs that might prolong QT/QTc Note: A subject who receives such treatment will not be a candidate for this study, if his/her condition does not allow for a treatment-free period of at least 5 elimination half-lives of the drug that might prolong QT/QTc before the GHST;
• Elevation of laboratory parameters indicating hepatic or renal dysfunction or damage (aspartate amino transferase (AST), alkaline phosphatase (ALT), gamma-glutamyl transferase (GGT) > 2.5 x upper limit of normal (ULN); creatinine or bilirubin > 1.5x ULN);
• Current active malignancy other than non-melanoma skin cancer;
• Female of child-bearing potential and not using an adequate contraceptive method (adequate contraceptive measures as required by local regulation or practice).
• Male of reproductive age who or whose partner(s) is not using an adequate contraceptive method (adequate contraceptive measures as required by local regulation or practice).
• Lack of ability or willingness to give informed consent by the subject and/or his/her legal representative;
• Anticipated non-availability for trial visits/procedures.