after joining the extension study, a consent form is signed and basic health information is recorded.

baseline measurements are taken, including an examination of the nasal passages and a blood sample.

the participant is assigned, without knowing which one, to receive either itepekimab or a matched placebo for test product.

the study is double‑blinded, meaning neither the participant nor the investigator knows which medication is given.

the assigned medication is given as a subcutaneous injection (injection under the skin).

the dose is 00 mg of the study product.

the injection is performed by qualified study staff in a clinical setting.

at each scheduled visit, the participant receives another injection according to the study schedule.

the visit includes checking for any adverse events (unwanted health changes), measuring vital signs, and collecting blood samples to assess the level of itepekimab in the serum and to test for anti‑drug antibodies.

any serious health problems are reported to the study safety team.

the injection schedule continues for the entire duration of the extension study, which runs until the estimated end date of 2028‑12‑12.

the participant remains under observation for the long‑term safety and tolerability of the assigned product.

at the conclusion of the study, a final evaluation is performed, including an endoscopic examination of the nasal passages and a summary of any adverse events that occurred.

all collected data are used to evaluate the long‑term safety of the medication.