Upon joining the study, you will be randomly assigned to one of two treatment groups. This process is called randomization and ensures fairness in the study.

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

Neither you nor your doctor will know which treatment you are receiving. This is called a double-blind study and helps ensure accurate results.

You will receive injections of either tulisokibart or placebo under your skin. This type of injection is called subcutaneous.

The medication comes in a pre-filled injector, which is a ready-to-use device containing the solution for injection.

The frequency and duration of injections will be determined by the study schedule provided to you by the study staff.

You will attend regular study visits where various assessments will be performed to monitor your condition and safety.

At Week 16, several important evaluations will be conducted to measure how well the treatment is working.

During these visits, you will be asked questions about your back pain, including pain during the day and at night.

Your ability to perform daily activities and your overall function will be assessed using standardized questionnaires.

If you have enthesitis, which is inflammation where tendons or ligaments attach to bone, this will be evaluated at your visits.

Your spine and joint flexibility will be measured through physical examinations.

You will undergo magnetic resonance imaging (MRI) scans of your spine and sacroiliac joints (the joints at the base of your spine connecting to your pelvis).

These scans will be performed at baseline before treatment starts and again at Week 16.

The MRI scans help doctors see inflammation in your spine and joints that cannot be detected through physical examination alone.

You will complete several questionnaires throughout the study to assess how your condition affects your daily life.

These questionnaires evaluate your disease activity, physical function, fatigue levels, and overall health status.

The assessments help measure whether the treatment improves your quality of life and ability to perform everyday tasks.

Throughout the study, you will be monitored for any adverse events, which are any unwanted or unexpected medical occurrences.

You should report any new symptoms, health changes, or concerns to the study staff at each visit.

Safety assessments will continue throughout your participation in the study.

The study continues beyond Week 16, with ongoing treatment and monitoring.

You will continue to attend regular study visits for assessments and to receive study medication.

The total duration of your participation will be determined by the study protocol and explained to you by the study staff.