after joining the study you are assigned by the study system to receive either nemolizumab or placebo. the assignment is double‑blind, meaning you will not know which product you receive.

before the first injection a series of measurements is performed. these include the thickness of the skin (modified roddan skin score), lung capacity (forced vital capacity), vital signs, blood laboratory tests, and an electrocardiogram. the results serve as the reference point for later comparisons.

the study medication is given by subcutaneous injection (under the skin) using a pre‑filled pen. the exact amount of nemolizumab or the inert placebo is defined by the study protocol and is administered according to the scheduled visits.

you attend scheduled clinic visits throughout a 52‑week main treatment period. at each visit you receive the next injection, and the study team repeats the skin score, lung function test, vital signs, laboratory tests, and records any side effects.

after completing 52 weeks of injections, the main outcome (change in the modified roddan skin score) is measured and compared with the baseline value.

if you choose to continue, you enter a 156‑week extension phase. the same injection schedule continues, and safety assessments are performed regularly.

throughout the 156‑week extension you continue to receive the subcutaneous injection, and the study records any adverse events, changes in vital signs, laboratory results, weight, and electrocardiogram findings.

at the conclusion of the 156‑week extension a final set of measurements is performed, including skin thickness, lung capacity, blood tests for drug levels, and tests for antibodies that might have formed against nemolizumab.