Efficacy in Biologic Failure and Nonbiologic-Failure Populations in a Phase 3 Study of Ustekinumab in Moderate-Severe Ulcerative Colitis: UNIFI - Sands, BE; Peyrin-Biroulet, L; Marano, C; O'Brien, CD; Zhang, H; Johanns, J; Szapary, P; Rowbotham, D; Leong, RW; Arasaradnam, RP; Danese, S; van Assche, G; Targan, S; Sandborn, WJ (Zeitschrift für Gastroenterologie, 2019)