integrin for vedolizumab and interleukin-12/23 pathways for ustekinumab) than the primary biological class, anti-tumour necrosis factor alpha (anti-TNF) agents. As the armamentarium for IBD increases in coming years, it will become important to understand factors associated with response in order to best position and personalise therapy.Aim: To summarise the current data on predictors of response to vedolizumab and ustekinumab in IBD patients. Methods:We conducted a comprehensive literature review. A PubMed search was performed using pre-defined key words and terms to identify relevant studies on predictors of response.Results: Patients with severe disease (by clinical activity and inflammatory biomarkers), or prior anti-TNF exposure are less likely to respond to vedolizumab. Ileocolonic disease, no prior surgery and uncomplicated phenotype were associated with better responses to ustekinumab in CD. Initial response seems to predict a better long-term maintenance in both therapies (P < 0.001). Contrary to anti-TNF therapies, immunogenicity appears to play less of a role in response. Conclusion:As the number of new biological therapies increase in IBD, identifying patients who are most likely to benefit from specific agents is of paramount importance to help best position IBD therapies.

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