This study looks at two treatments for psoriatic arthritis (PsA), a condition that causes joint pain and swelling. The study compares two medicines: **guselkumab** (a selective IL23 inhibitor) and **golimumab** (a TNF inhibitor). TNF inhibitors are drugs that reduce inflammation caused by a protein called tumor necrosis factor (TNF). IL23 inhibitors work differently by targeting a specific part of the immune system. The study aims to find out if switching to guselkumab helps more than switching to another TNF inhibitor when the first TNF treatment does not work well enough.

Eligibility for the study includes having active PsA, being on a stable dose of certain medications, and using or having used one TNF inhibitor before. People who have used golimumab or other specific biologic drugs before cannot join.

• The study involves switching medications to see which works better.
• Participants must have PsA that isn't responding well to current TNF treatment.
• Some people may not qualify if they have used certain medications or have specific health conditions.