#ACR21 Abs#1224. ⬇️ CD39 expression on B cell predicts occurrence of anti-drug Ab in RA on RTX ⭐️13/23 pts on RTX became ADAb+. No diff in concomitant MTX usage ⭐️Baseline CD73 similar, but lower CD39 predictive of ADAb https://t.co/QzbAmXtTmZ @Rheumnow https://t.co/CLtEev69YD