The main types of IBD, ulcerative colitis (UC) and Crohn’s disease (CD), are serious chronic conditions negatively affecting life, usually from a young age. A well-established hypothesis is that environmental and microbial triggers lead to an inappropriate immunological response in genetically susceptible individuals. There is great variation in symptoms, disease course and responses to treatments. Medications used for IBD vary from classic anti-inflammatory agents to antibodies and small molecules that more specifically target parts of the immune system. However, these interventions offer no cure and have unpredictable effects. Today, the aim of treatment is to reduce the inflammation, provide relief of symptoms and prevent relapse. Because UC and CD manifest as inflammatory diseases, most IBD research has focused on immune cell-mediated mechanisms. Intestinal epithelial cells (IECs) are probably significantly more central in gut inflammation than previously acknowledged. Still, there are few drugs directly targeting IECs in IBD, and we do not know whether drugs that have been developed to affect immune cells have negative or positive effects on epithelial functions. In this project, we use advanced 3D organoid technology to gain mechanistic understanding of the mode of action of approved and emerging IBD drugs on IECs, identify whether drugs designed against immune cell show adverse effects in IEC, and identify novel epithelial-targeted therapies. Organoids from patient-derived intestinal biopsies ("mini-guts") can be kept in long-term 3D cultures (colonoids from the large intestine and enteroids from the small intestine). Such ex vivo models are closer to actual disease biology than animal models and cancer cell lines that have been used previously in IBD research. The ambition for the project is to provide insights into IBD pathobiology and bring forward detailed mechanistic knowledge about the role of IECs in IBD that can facilitate precision medicine in IBD.