after joining the study you will undergo a baseline assessment that includes a physical exam, measurement of oxygen saturation (the amount of oxygen in the blood), height measurement, a lung function test, and completion of a quality‑of‑life questionnaire.

the purpose of this visit is to record your health status before any study medication is taken.

children aged 6 to less than 18 years are randomly assigned to receive either nerandomilast or a placebo tablet; children aged 2 to less than 6 years receive nerandomilast in an open‑label manner (both you and the study team know the medicine).

randomisation ensures that the groups are comparable and that the study results are reliable.

you will take one oral film‑coated tablet each day, at the same time each day, for a period of 26 weeks.

the tablet contains nerandomilast (or, if you are in the placebo group, an inactive tablet that looks the same). the exact amount of active substance is defined by the study protocol.

at week 2 you will return for a safety visit. a small blood sample will be taken to measure the level of the study drug in your body (rich sampling for participants 6‑<18 years, sparse sampling for participants younger than 6 years).

the visit also includes a check for any side effects and a repeat of the oxygen‑saturation measurement.

throughout weeks 4, 8, 12, 16, 20 and 26 you will attend monitoring visits.

each visit includes assessment of side effects, measurement of oxygen saturation, height, and completion of the quality‑of‑life questionnaire.

these visits help the study team evaluate how well the medication is tolerated and whether it influences your health.

at week 26 a final part‑a assessment is performed. the study records any adverse events that occurred, changes in oxygen saturation, height, lung function (for participants 6 years and older), and questionnaire results.

if you received the placebo, you may be offered open‑label nerandomilast in the next phase of the study.

starting at week 27 you will continue taking the same oral tablet daily, now as an open‑label active treatment, for an additional 26 weeks (up to week 52).

the dosage remains the same as in part a.

at week 28 a blood sample is taken to evaluate drug exposure at steady state during part b.

the visit also includes safety checks and repeat measurements of oxygen saturation.

additional visits occur at week 40 and week 52.

each visit repeats the safety assessments, oxygen‑saturation measurement, height measurement, lung function test (for participants 6 years and older), and quality‑of‑life questionnaire.

the study ends with a comprehensive final visit at week 52.

all data collected during the trial are reviewed, including any adverse events that occurred at any time, changes in health parameters, and overall tolerability of nerandomilast.