Indigo naturalis is effective even in treatment-refractory patients with ulcerative colitis: a post hoc analysis from the INDIGO study

Background We recently reported the efficacy of indigo naturalis (IN) in patients with active ulcerative colitis (UC) in a randomized controlled trial (INDIGO study). However, few studies have been conducted to investigate whether IN is effective even in treatment-refractory cases, such as in those with steroid dependency and anti-TNF refractoriness.