after you sign the consent form, you receive a study identification number.

baseline measurements are taken, including medical history, lung function tests, height, weight, oxygen saturation on room air, and a quality‑of‑life questionnaire.

if you are between 6 and less than 18 years old, you enter a double‑blind phase where you will receive either nerandomilast or a placebo tablet, and you will not know which one you are taking.

if you are between 2 and less than 6 years old, you are placed directly in an open‑label phase and will receive nerandomilast from the start.

you take an oral film‑coated tablet once daily as instructed by the study team.

the tablet contains nerandomilast (or placebo for the double‑blind group) at a dose of 00 mg.

the tablet is swallowed with water and should be taken at the same time each day.

at week 2 you attend a study visit for blood sampling.

participants aged 6 years and older provide a rich sampling set, while younger participants provide a sparse sampling set.

the visit also includes a check for any treatment‑emergent adverse events and a review of your oxygen saturation and height.

throughout part a you attend scheduled visits to report any side effects, have your oxygen saturation measured, and confirm that you are taking the tablet as directed.

the study team may also assess the acceptability of the tablet size and the use of a dispenser at week 2 and week 26.

at week 26 a comprehensive evaluation is performed.

measurements include oxygen saturation on room air, height, a quality‑of‑life questionnaire, and a review of any adverse events that occurred up to this point.

for participants 6 years and older, lung function (forced vital capacity) and a 6‑minute walk distance may also be measured.

after week 26 all participants, regardless of previous group, receive open‑label nerandomilast tablets.

the same daily dose of 00 mg is continued.

the purpose of part b is to collect additional safety and exposure data up to week 52.

at week 28 a blood sampling visit is performed for participants 6 years and older to assess drug exposure at steady state.

at week 52 a final evaluation is conducted.

the same measurements as at week 26 are repeated: oxygen saturation, height, quality‑of‑life questionnaire, and for eligible participants lung function and 6‑minute walk distance.

all adverse events that occurred during the entire trial are recorded.

after the week 52 visit, study medication is stopped and data collection is finished.

you are thanked for your contribution and any remaining study supplies are returned as instructed.