after joining the study, the patient is assigned to receive either rituximab or sodium chloride (placebo).

the assigned product is given as an intravenous infusion. rituximab is provided as a 500 mg solution for infusion, while the placebo is 250 ml of sodium chloride solution.

the infusion is administered during a clinic visit that lasts several hours, during which vital signs are monitored.

immediately after the first infusion, the patient undergoes baseline measurements that include lung function tests such as forced vital capacity (fvc) and diffusing capacity for carbon monoxide (dlco), a 6‑minute walk test, and imaging of the chest.

questionnaires about health-related quality of life and disease activity are also completed.

the patient returns to the clinic at month 6 for safety checks and repeat assessments.

lung function tests (fvc and dlco), the 6‑minute walk test, and chest imaging are repeated.

any adverse events are recorded, and the patient completes the same quality‑of‑life questionnaires.

at the month 6 visit, the patient receives a second intravenous infusion of the same product assigned at randomization (either rituximab 500 mg or sodium chloride 250 ml).

the infusion procedure is identical to the first infusion.

the patient attends a clinic visit at month 12 for the same set of safety evaluations and lung function measurements as at month 6.

questionnaires and imaging are repeated.

at the month 12 visit, a third intravenous infusion of the assigned product is given.

the patient completes the last study visit at month 18.

all primary and secondary measurements are performed, including change in fvc from baseline, safety evaluation, disease‑related mortality, progression‑free survival, and health‑related quality‑of‑life scores.

the study concludes for the patient after these assessments.