Efficacy of Upadacitinib as an Induction Therapy in Severe and Refractory Ulcerative Colitis: Sub‐Group Analysis of the Phase 2b Study U‐ACHIEVE: 678. (October 2019) - D'Haens, Geert R.; Lindsay, James O.; Loftus, Edward V.; Zhou, Wen; Cataldi, Fabio; Xie, Wangang; Pugatch, David; Panaccione, Remo