Targeting TL1A in inflammatory bowel disease: a novel mechanism of action

Tumour necrosis factor-like cytokine 1A (TL1A), encoded by TNFSF15, plays a key role in both mucosal immune activation and stromal remodelling and is the first target in inflammatory bowel diseases (IBD) that has advanced through drug development programmes with a dual anti-inflammatory and anti-fibrotic rationale, although the anti-fibrotic effect remains putative and has not been demonstrated in any randomised clinical trial. Genome-wide association studies, tissue expression data and promising findings from animal models have highlighted the likely importance of the TL1A-DR3 axis, and to date three first-generation monoclonal antibodies have promising controlled clinical trial data, with more than 10 further molecules in earlier development (trial registry and pipeline literature searched to 1 September 2026). TL1A represents one of the most compelling examples of genetically informed drug development in IBD, where initial human genetic studies targeted further downstream work to focus on TNFSF15 pathways in inflammation and fibrosis—providing a rationale for therapeutic inhibition. In this review, we discuss TL1A biology, its roles as a potential master immune regulator, the evidence linking TL1A to fibrogenesis, headline findings from clinical trials and the questions that will determine whether this class delivers on its promise.