We aimed to compare trough infliximab levels and the development of antidrug antibody (ADA) for 1 year between Crohn's disease (CD) and ulcerative colitis (UC) patients who were biologic-naive, and to evaluate their impact on clinical outcomes.
This was a prospective, multicenter, observational study. Biologic-naive patients with moderate to severe CD or UC who started CT-P13, an infliximab biosimilar, therapy were enrolled. Trough drug and ADA levels were measured periodically for 1 year after CT-P13 initiation.
A total of 267 patients who received CT-P13 treatment were included (CD 168, UC 99). The rates of clinical remission (72% vs. 32.3%,P<0.001) at week 54 were significantly higher in CD than in UC. The median trough drug level (μg/mL) was significantly higher in CD than in UC up to week 14 (week 2, 18.7 vs. 14.7,P<0.001; week 6, 12.5 vs. 8.6,P<0.001; week 14, 3.4 vs. 2.5,P=0.001). The median ADA level (AU/mL) was significantly lower in CD than in UC at week 2 (6.3 vs. 6.5,P=0.046), week 30 (7.9 vs. 11.8,P=0.007), and week 54 (9.3 vs. 12.3,P=0.032). Development of ADA at week 2 [adjusted odds ratio (aOR)=0.15,P=0.026], initial C-reactive protein level (aOR=0.87,P=0.032), and CD over UC (aOR=1.92,P<0.001) were independent predictors of clinical remission at week 54.
Infliximab shows more favorable pharmacokinetics, including high drug trough and low ADA levels, in CD than in UC, which might result in better clinical outcomes for 1-year infliximab treatment in CD patients.