This is a study to see if a medication called efgartigimod is safe to use for a long time in adults with a condition called primary Sjögren's Syndrome (pSS). pSS is a disease where the immune system attacks parts of the body, and efgartigimod might help by lowering certain antibodies (proteins) that cause problems. This study will last 48 weeks and is for people who have already been in a related study and finished their treatments there. Participants will receive efgartigimod even if they were taking a placebo (a "fake" treatment) before. They won't know if they had the real treatment or placebo in the earlier study. To join, participants must be adults, agree to use birth control, and have already completed the earlier study. They cannot join if they have certain health issues or if they are pregnant or planning to get pregnant during the study.

• Study duration is 48 weeks.
• Participants receive efgartigimod even if they had a placebo before.
• Eligibility requires completion of a previous related study.