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* = Presenting author

P506 Serum infliximab and antibodies to infliximab levels in Crohn’s disease and ulcerative colitis patients on long-term maintenance therapy

M. Waterman*1, H. Bar Yoseph1, B. Ungar2, S. Ben - Horin2, Y. Chowers1

1Rambam Health Care Campus, Department of Gastroenterology, Haifa, Israel, 2Sheba Medical Centre, Department of Gastroenterology, Ramat Gan, Israel

Background

Infliximab (IFX) is effective in maintaining remission in ulcerative colitis (UC) and Crohn’s disease (CD). However, it is unknown if serum drug levels (SDL) and predisposition for ATI formation differ between CD and UC.

Aim: to assess whether the pharmacokinetics and clinical effect of IFX for maintenance of remission differ between UC and CD.

Methods

Serum drug levels and ATI concentrations were prospectively determined in CD and UC patients with clinical response or remission on IFX maintenance therapy. Clinical parameters were collected using retrospective chart review. Patients with UC and CD (1:2 ratio) were matched for IFX dose and interval, concurrent immunomodulator therapy, and type of therapeutic response. Clinical parameters and mean SDL and ATI levels were compared using the Chi-square test and Mann–Whitney tests for categorical and continuous variables, respectively.

Results

In total, 77 responding patients (28 UC and 49 CD) were assessed. The UC and CD groups were similar in gender ratio, ethnicity, disease duration before IFX, smoking status, IFX dosing and duration, mean serum albumin, and C-reactive protein (CRP). The mean duration of IFX maintenance was 12 months. Patients with UC had higher rates of BMI ≥ 25 (48% vs 23%, respectively, p = 0.03) and were older at diagnosis (28.6 vs 20 years, respectively p = 0.01) compared with the CD. The UC group had significantly lower mean SDL (3.6 and 5.1 mcg/mL, respectively p = 0.022) and higher mean ATI (7.9 vs 3 mcg/mL, respectively p = 0.024) compared with the CD group. 32% of UC patients had a combination of SDL ≤ 1 mcg/ml and ATI≥4 mcg/mL compared with only 10% of CD patients.

Conclusion

Long-term clinical response to IFX is associated with more ATI formation and lower serum IFX in UC compared with CD. A third of UC patients who maintain response or remission do so in the absence of serum IFX. Larger cohorts are required to investigate the role of IFX in UC patients in maintaining long-term remission.