Abstract Background Infliximab (IFX) is effective for inflammatory bowel disease (IBD), but treatment response varies due to differences in drug exposure and immunogenicity. Proactive therapeutic drug monitoring (TDM) may optimize outcomes. We evaluated 5-year outcomes of a proactive IFX TDM strategy on treatment discontinuation, surgery, and remission in a real-world IBD cohort. Methods Retrospective cohort study of adults with Crohn’s disease (CD) and ulcerative colitis (UC) treated with IFX at a tertiary hospital in Portugal. From week 14 and at every other infusion, trough levels and anti-drug antibodies were measured using an ELISA assay. Treatment was proactively escalated, targeting an IFX trough level ≥ 5 μg/mL. Outcomes included fecal calprotectin remission, clinical remission, steroid-free remission, treatment discontinuation, and surgery. Results A total of 359 patients (221 CD, 138 UC) were included, with 93 (25.9%) presenting with extraintestinal manifestations (EIM). Clinical remission was achieved in 67.7% of patients, and 54.3% attained steroid-free remission. Surgery was required in 10.6%, while 26.7% discontinued IFX therapy, with higher discontinuation rates in UC than CD (34.8% vs. 21.7%, p0.05). Calprotectin remission was more frequent in CD than in UC (63.8% vs 47.8%, p = 0.003). Median IFX levels did not correlate with clinical remission (p=0.472), steroid-free remission (p=0.677), or surgery (p=0.200), but were significantly lower in patients who discontinued treatment (5.86 vs. 9.14 µg/mL, p0.001). In CD, B2 phenotype predicted surgery (OR 4.373, p=0.004). Adverse events leading to drug cessation occurred in 39 patients (10.8%), most commonly psoriasis (n = 16), other cutaneous reactions (n = 7), infusion reactions (n = 6), infections (n = 4), and malignancy (n = 3). Conclusion Lower IFX trough levels were strongly associated with treatment discontinuation, supporting the value of proactive TDM in identifying patients at risk of loss of response. Trough levels did not correlate with remission or surgery. Disease-specific patterns were observed, with higher discontinuation rates in UC, and B2 phenotype independently predicted surgery in CD. Conflict of interest: Dr. Tubal Bronze, Sérgio Manuel: No conflict of interest Pinto, Carlota: No conflict of interest Pereira, Filipa: No conflict of interest Rodrigues, Inês: No conflict of interest Saraiva, Sofia: No conflict of interest Fernandes, Samuel Raimundo: No conflict of interest Gonçalves, Ana Rita: No conflict of interest Valente, Ana Isabel: No conflict of interest Correia, Luis: No conflict of interest
Bronze et al. (Thu,) studied this question.