Abstract Background Treatment of inflammatory bowel disease (IBD) with biologicals, such as adalimumab, is hampered by high non-response rates and lack of reliable response prediction tools. Therefore, patients are potentially exposed to ineffective treatment and side effects, while clinical deterioration continues. Moreover, it is unclear whether the drug reaches its target site in adequate concentrations to achieve treatment response. We aim to visualise adalimumab distribution and detect adalimumab target cells using quantified fluorescence molecular endoscopy (qFME). Methods Adalimumab was labelled with IRDye 680LT under cGMP conditions, resulting in a fluorescent tracer suitable for human use. This tracer is used in an ongoing, non-randomized, non-blinded, prospective feasibility study. A total of 21 IBD patients scheduled for an endoscopy will be included. Up until now, eight patients received adalimumab-680LT (4.5 mg: n=3, 15 mg: n=3, 25 mg: n=2), and three patients were included as a control. Two to four days after tracer administration, qFME was performed to gather in vivo fluorescence data of inflamed and non-inflamed tissue. Fluorescent signals were quantified by multi-diameter single fibre reflectance/single fibre fluorescence (MDSFR/SFF) spectroscopy. Furthermore, biopsies were taken from inflamed and non-inflamed mucosa for ex vivo analysis. Results To date, 11 patients were included. Tracer administration was well tolerated and no adverse events occurred in any dose group. Real-time in vivo macroscopic imaging showed clear uptake of adalimumab-680LT in inflamed tissue compared to non-inflamed tissue (figure 1A). Spectroscopy revealed a dose-dependent increase in fluorescent signal for adalimumab-680LT in inflamed tissue, with a significant difference between 4.5 and 15 mg (0.016 [0.011-0.021] vs 0.033 [0.021-0.043] (p=0.036)) (figure 1B). The difference between inflamed and non-inflamed tissue is most noticeable in the 25 mg group. Ex vivo Mean Fluorescent Intensity (MFI) quantification of all biopsies showed a significant increase of fluorescent signal in the 15 and 25 mg dose groups compared to control in inflamed tissue (65.0 [54.0-75.7] vs 32.4 [27.1-38.2] (p=0.0040), and 62.1 [44.1-82.8] vs 32.4 [27.1-38.2] (p=0.0286), respectively) (figure 1C). Conclusion Preliminary results show adalimumab-680LT is safe for visualising adalimumab distribution. Doses of at least 15 mg are sufficient for visualisation and quantification of fluorescent signal in vivo. Furthermore, higher MFI’s and spectroscopy results were measured in inflamed tissue compared to healthy tissue, indicating targeting of the tracer to inflamed tissue. Future ex vivo experiments are ongoing to visualise adalimumab target cells.
Read full abstract