P316 Human neutrophil elastase derived fragment of calprotectin (S100a9) is a serum biomarker (CPa9-HNE) for monitoring of anti-TNFα treatment response in Crohn’s disease

Abstract Background In patients with inflammatory bowel disease (IBD), up to 30% do not achieve response, 66% do not achieve remission, and 40% experience loss of response to anti-TNFα treatment. In Crohn’s disease (CD), fecal calprotectin is the most widely used fecal biomarker for diagnosis and monitoring of disease activity. Fecal sampling and processing are tedious compared to serum sampling, and biomarker quantification in serum is more efficient, convenient, and also more acceptable for patients. Therefore, there is a need for a robust and reliable serum calprotectin biomarker that performs better than conventional serum biomarkers. The aim of this study was to investigate the performance of a novel serum calprotectin assay, which quantifies a specific human neutrophil elastase (HNE) generated calprotectin (S100a9) fragment (CPa9-HNE), as a measure of true neutrophil granulocyte activity, for monitoring treatment responses in patients with CD. Methods We included 30 CD patients with clinically active (Harvey-Bradshaw Index (HBI)≥5) luminal inflammation scheduled for anti-TNF treatment (adalimumab or infliximab). Serum samples where obtained at baseline (n=30), week 1 (n=29), week 8 (n=28), week 26 (n=15), and week 56 (n=7). CPa9-HNE (Calprotectin, S100a9, specific fragment generated by human neutrophil elastase), CRP and fecal calprotectin were quantified. Remitters (n=11) were defined as patients in clinical remission (HBI<5) at week 8 with no flares at week 26 or week 56. Non-remitters (n=19) were defined by having clinical active disease (HBI≥5) at week 8 or having a flare at week 26 or week 56. Results Patients with severe disease activity (HBI>16) had significantly elevated serum levels of CPa9-HNE compared with patients in remission (p<0.05), with mild (p<0.05) or moderate (p<0.01) disease activity. CPa9-HNE serum levels were significantly suppressed in remitters compared with non-remitters at week 8 (p<0.001), week 26 (p<0.01) and week 56 (p<0.05) (Figure 1). Fecal calprotectin and CRP were significantly suppressed at week 8, week 26 and week 56 compared with baseline levels for remitters and non-remitters, but there was no significant difference between remitters and non-remitters (Figure 1). Non-remitters were more likely to have high levels of CPa9-HNE at baseline (tertile 1,2 vs tertile 3; OR: 6.8 (CI:1.22-36.5), p=0.027) and week 8 (tertile 1,2 vs tertile 3; OR: 24 (CI:2.56-279), p=0.0014). Conclusion CPa9-HNE is a novel non-invasive biomarker for monitoring treatment response to anti-TNFα for CD patients and may be used as a surrogate marker for assessing disease activity and to predict outcome of anti-TNFα treatment.