P439 Stability of subcutaneous serum IFX (CTP13) levels between two injections and over two successive cycles in patients with Crohn’s disease

Abstract

Abstract Background Under IFX sc, we do not know if there is a residual level of IFX. The aim of this work was to investigate this point by analyzing the intra-individual variability of the serum level of IFX sc. Methods This was an observational, prospective study that included patients with CD undergoing maintenance treatment with IFX sc (120mg every, 14 days). Patients had IFX determinations (i Track, 10; Theradiag (France) at visit, 1 (day, 4 to, 6 after SC injection), visit, 2 (day, 7 to, 9 after sc injection) and visit, 3 (day, 13 to, 14 after sc injection) on two consecutive cycles. The first determinations were made only after, 8 weeks of switching from IV to SC. All patients at inclusion were in clinical remission (CDAI <, 150) with calprotectin levels <, 250 µg/g stool. Results 20 patients (mean age:, 36 years, sex ratio M/F:, 1, mean duration of IFX IV:, 16 months) were included, i.e. meaning, 120 determinations., 8 patients were treated in combination with thiopurines. Mean residual levels before switch to sc were, 3.9 +/-1.2 µg/mL. Mean intraindividual levels between the two cycles were comparable (Visit, 1: cycle, 1:, 11.1 +/-, 4.4 µg/mL, cycle, 2:, 11.6 +/-, 4.6 µg/mL; p=0.65; Visit, 2: cycle, 1:, 12.0 +/-, 5.1 µg/mL, cycle, 2:, 11.3 +/-4.9 µg/mL; p=0.25; Visit, 3 cycle, 1:, 11.0 +/-4., 7 µg/mL, cycle, 2:, 10.9 +/-, 4.2 µg/mL; p=0.21. Serum IFX sc levels remained stable over the, 14 days between the two SC injections (p=0.36). Mean IFX levels at any dosing time were comparable in patients with and without thiopurines (IFX sc monotherapy: mean:, 11.5 +/-, 5.5 µg/mL versus IFX sc with thiopurines: mean:, 11.8 +/-, 4.6 µg/mL, p=0.54). Finally, residual IFX IV levels before switch did not influence the results of IFX sc serum concentrations (p=NS). Conclusion Measure of IFX levels for IFX SC can be proposed at any time between two injections. No residual levels were found. These data are important for our clinical practice.