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P526 Impact of postinduction infliximab trough level and disease activity on primary response in Crohn's Disease

A. Echarri*1, R. Ferreiro2, R. Fraga1, J. Cid3, M. Barreiro2, D. Carpio4, S. Pereira5, L. De Castro5, S. Soto6, A. Fernandez-Villaverde7, B. Gonzalez8, E. Santos9

1Complejo Hospitalario Ferrol, Gastroenterology, Ferrol, Spain, 2Complejo Hospitalario Universitario Santiago, Gastroenterology, Santiago, Spain, 3Complejo Hospitalario Coruña, Immunology, Coruña, Spain, 4Complejo Hospitalario Pontevedra, Gastroenterology, Pontevedra, Spain, 5Complejo Hospitalario Vigo, Gastroenterology, Vigo, Spain, 6Complejo Hospitalario Orense, Gastroenterology, Orense, Spain, 7Povisa, Gastroenterology, Vigo, Spain, 8Complejo Hospitalario Coruña, Gastroenterology, Coruña, Spain, 9Complejo Hospitalario Lugo, Gastroenterology, Lugo, Spain

Background

Primary non-response to infliximab (IFX) induction therapy occurs in 10-20% of cases in clinical series. Few data have been reported on the clinical impact of low serum IFX trough levels after the induction treatment and their relation with clinical response, disease activity or the development of immunogenicity.

Methods

There are two primary aims of this study: 1. To assess the clinical relevance of a low serum IFX level during induction therapy. 2. To identify possible risk factors associated with reduced serum levels of IFX.

We included 36 Crohn´s disease patients with moderate to severe disease under infliximab induction treatment. Patients were treated

with IFX 5mg/kg at 0,2 and 6 weeks as induction dose, followed by 5mg/kg every 8w. Blood samples were drawn at standardized time points before and after induction therapy ( at 0,6,14 and 30w) just before IFX

treatment. Serum IFX trough levels and anti-Infliximab antibodies (ATI) were measured using an enzyme-linked immunosorbent

assay (ELISA). Disease activity was assessed at the same time points by means of the Harvey-Bradshaw Index (HBI; remission< 3, mild-moderate disease 4-14, and severe disease >15) and CRP/calprotectin levels.

Results

After IFX induction therapy, the median serum IFX trough level was significantly higher in patients in clinical remission (IFX: 7,62ug/ml) than in patients with active disease (IFX 0,032 ug/ml P< 0,01).

Receiver operating characteristic curve analysis indicated a cut-off value of 3ug/ml at week 6. The positive predictive value of high

postinduction IFX trough level (IFX >3 ug/ml at 6w) for prediciting good response and sustained remission after IFX induction was >90%

ATI levels were detected in 26% of IFX treated patients and were significantly related to low trough levels and infusional IFX

reactions. Low postinduction IFX trough levels were related to primary failure in 80% of patients. The cumulative number of patients

with low IFX trough levels were significantly higher in patients with severe disease activity and ATI detection

Conclusion

1. Low post-induction IFX trough levesl are associated with primary failure.

2. Optimal predictors of postinduction clinical remission to IFX were week 6 trough level>3ug/ml and a low disease activity before

treatment.