TREM-1, the ideal predictive biomarker for endoscopic healing in anti-TNF-treated Crohn’s disease patients?

We read with great interest the study by Gaujoux et al , who described a whole blood marker for anti-tumour necrosis factor (TNF) responsiveness in patients with Crohn’s disease (CD). The availability of anti-TNF agents dramatically changed therapeutic strategies for patients with CD. However, an overall non-response rate of 30% has been observed, and, together with the approval of new classes of biological agents with a different mode of action, clearly indicates the need for predictive biomarkers. Gaujoux et al identified triggering receptor expressed on myeloid cells 1 ( TREM1) expression in whole blood as a biomarker for anti-TNF (non)response (higher expression in responders).1 In inflamed colonic tissue, TREM1 expression is also decreased in future infliximab responders.1 2 TREM-1 is known to amplify inflammation, whereas TREM-1 inhibition in vivo attenuates colitis by modulating autophagy and endoplasmic reticulum (ER) stress.3 We first measured serum TREM-1 (sTREM-1) (Human sTREM-1 ELISA (HK348), Hycult Biotech, Uden, the Netherlands) in 85 patients with CD with active disease prior to anti-TNF therapy (table 1). To reduce the risk of including treatment failures secondary to immunogenicity (and not drug mechanistic failure) or non-drug-related healers, all included patients had to have a good drug exposure, defined as a maintenance trough level >3.0 µg/mL for infliximab or >5.0 µg/mL for adalimumab. Interestingly, patients who achieved mucosal healing (complete absence of ulcerations and erosions4) after 6 months of anti-TNF therapy (adalimumab and infliximab) had significantly lower baseline sTREM-1 levels compared with non-responders (50.8 pg/mL …