Upon joining the study, you will be randomly assigned to one of two groups. This random assignment is similar to flipping a coin and determines which treatment you will receive during the first part of the study.

One group will receive tibulizumab, which is the medication being tested. The other group will receive a placebo, which looks identical but contains no active medication.

During this phase, neither you nor your doctor will know which treatment you are receiving. This is called a double-blind period and helps ensure the results are accurate and unbiased.

This first period lasts for 24 weeks (approximately 6 months).

You will receive either tibulizumab or placebo through subcutaneous injection. A subcutaneous injection means the medication is injected under the skin using a needle.

The medication is provided as a solution for injection, which is a liquid form ready to be injected.

The specific dosage and frequency of injections will be determined by the study protocol and explained to you by the study staff.

During this period, your skin thickness will be measured using the modified Rodnan Skin Score, which is a method to assess how thick and tight your skin is in different areas of your body.

Your lung function will be tested by measuring forced vital capacity, which checks how much air you can forcefully exhale after taking a deep breath.

You will have high-resolution computed tomography scans of your lungs to assess any lung tissue changes.

Your ability to perform daily activities will be evaluated using the Health Assessment Questionnaire Disability Index, which asks questions about tasks like dressing, eating, and walking.

Throughout this period, any side effects or health changes you experience will be recorded and monitored.

After completing the first 24 weeks, you will enter the second period of the study called the open-label extension.

During this phase, all participants will receive tibulizumab. Both you and your doctor will know that you are receiving the active medication.

This period continues until Week 52 (approximately 1 year from the start of the study).

You will continue to receive tibulizumab through subcutaneous injection at the same intervals as before.

Your skin thickness will continue to be measured using the modified Rodnan Skin Score.

Safety monitoring will continue throughout this period, including regular checks of your vital signs such as blood pressure, heart rate, and temperature.

You will have electrocardiograms, which are tests that record the electrical activity of your heart.

Blood and other laboratory tests will be performed regularly to monitor your overall health and check for any changes.

Any side effects or health concerns will continue to be documented and assessed.

Throughout both periods of the study, you will attend regular clinic visits for assessments and to receive your injections.

At each visit, the study staff will check your overall health and ask about any symptoms or side effects you may be experiencing.

Lung imaging with high-resolution computed tomography will be repeated at specified times to track any changes in your lung tissue.

Your lung function will be tested repeatedly by measuring how much air you can breathe out, which helps assess if your lung capacity is changing.

The thickness and tightness of your skin will be regularly measured at multiple body sites to track any improvements or changes.

You will complete questionnaires about your ability to perform everyday activities to see if the treatment affects your quality of life.

All test results, measurements, and any health changes will be carefully recorded throughout your participation in the study.