Effectiveness and safety of ustekinumab in bio-naïve Crohn’s disease patients: a multicentre observational retrospective study oleh Valdés Delgado Teresa, Olmedo Martín Rául, Iborra Marisa, Herrera de Guisé Claudia, Fuentes-Valenzuela Esteban, Melcarne Luigi, Martín-Rodríguez Mª Mar, Kolle Casso Lilyan, De Castro Parga Luisa, Ponferrada Díaz Ángel, Vicente Lidón Raquel, Manceñido Marcos Noemí, Velayos Jiménez Benito, Lázaro Sáez Marta, López Cauce Beatriz, Mesonero Gismero Francisco, Gilabert Álvarez Pau, Argüelles-Arias Federico