4CPS-157 Study of serum concentrations of subcutaneous infliximab in inflamatory bowel desease and their correlation with analytic response

<h3>Background and Importance</h3> Subcutaneous infliximab(SC-IFX) serum concentrations(Css-IFX) needed for a response in patients with inflammatory bowel disease(IBD) are not yet well defined. <h3>Aim and Objectives</h3> Describing our patients population with IBD treated with SC-IFX and relate Css-IFX to analytic response. <h3>Material and Methods</h3> A three-year observational retrospective study was carried out(09/2021–09/2024) that included IBD patients treated with SC-IFX and with Css-IFX analysed. Variables: age, sex, weight, diagnosis[Chron´s disease (EC) or ulcerative colitis (CU)]; Css-IFX, antibodies against infliximab(AC-IFX), faecal calprotectin(FC), reactive-C-protein(RCP), and analytic response in the first three laboratory tests(LT). Analytic response was defined as FC&lt;100µg/g and RCP&lt;5mg/L. Three groups were stablished according to Css-IFX[G1(&lt;10 µg/mL),G2(10–20 µg/mL),G3(&gt;20µg/mL)]. Quantitative variables were expressed as mean±standard deviation or median/interquartile range (depending on distribution) and qualitative as frequencies. For the estimation of differences between groups Student´s t or Fisher´s exact test was used. Mantel-Haenszel test for trend was used to estimate linear correlation. <h3>Results</h3> 63 patients were included. Age 47(39–55)years, feminine sex 27(42.9%), weight 75.4±17.8kg, diagnosis CU 19(30.2%) vs EC 44(69.8%). Laboratory tests were taken at 13.3(9.8–16.4)(LT1), 28.1(24.6–35.6)(LT2) and 54.6(48.6–59.4) weeks(LT3). LT1: N=63. Css-IFX 16.9±8.4µg/mL, AC-IFX 2(3.2%), FC 1148.0±3785.7µg/g, RCP 6.1±10.8mg/L, analytic response 23(40.4%). Analytic response by groups: G1 2/13(15.4%), G2 6/16(27.3%) and G3 15/22(68.2%). Missing: 6. There are statistically significant differences between groups(p=0.003), and linear correlation(p=0,001). LT2: N=49. Css-IFX 17.6±8.5µg/mL, AC-IFX 1(2.0%), FC 12886.3±76766.0µg/g, RCP 5.2±6.7mg/L, analytic response 17(38.6%). Analytic response by groups: G1 3/8(37.5%), G2 6/21(28.6%) and G3 8/15(53.3%). Missing: 5. There are no statistically significant differences(p=0.359) or linear correlation(p=0.319). LT3: N=39. Css-IFX 15.8±8.6µg/mL, AC-IFX 2(5.1%), FC 567.5±1353.3µg/g, RCP 5.3±9.5mg/L, analytic response 16(45.7%). Analytic response by groups: G1 2/7(28.6%), G2 10/19(52.6%) and G3 4/9(44.4%). Missing: 4. There are no statistically significant differences(p=0.602) or linear correlation(p=0.590). <h3>Conclusion and Relevance</h3> Our study shows that a higher proportion of patients present analytic response with levels above 10µg/mL. In the first measurement there were significant differences in the response between groups, with a greater proportion of patients with analytic response at levels above 20µg/mL. However, these differences are not maintained thereafter. Further patients should be studied and the clinical and/or endoscopic response, as well as other variables influencing, should be evaluated in order to draw conclusions applicable to clinical practice. <h3>References and/or Acknowledgements</h3> Rodríguez-Moranta F, <i>et al</i>. Therapeutic drug monitoring in inflammatory bowel diseases. <i>Gastroenterol Hepatol</i>. 2024 May;<b>4</b>/(5):522–552. doi: 10.1016/j.gastrohep.2024.01.007. <h3>Conflict of Interest</h3> No conflict of interest