P470 Ustekinumab Trough Levels are not Associated with Clinical Response in Inflammatory Bowel Disease Patients

Abstract

Background Ustekinumab (UST) has been shown to effectively induce and maintain remission in inflammatory bowel disease (IBD). Only a few studies thus far have focused on UST pharmacokinetics suggesting that both, trough levels after i.v. induction as well as trough levels during stable maintenance might be associated with clinical and endoscopic response to UST. Data from real-world cohorts in this setting are scarce. Therefore, the aim of our study was to assess whether clinical response to UST was associated with a specific pharmacokinetic pattern. Methods All IBD patients treated with UST in one tertiary IBD centre between January 2017 and August 2020 were retrospectively retrieved from the database. Disease activity was assessed by Harvey-Bradshaw index (HBI) and partial Mayo score in Crohn’s disease (CD) and ulcerative colitis (UC) pts; respectively. Clinical response was defined as a decrease of HBI of ≥2 points or partial Mayo score ≥3 points. Patients not responding to therapy by week 16, or loosing original response received dose escalation from 90mg s.c. every 8 weeks to 90mg every 4 weeks. UST through levels were assessed by commercially available ELISA kit (IDKmonitor®) at week 8 after i.v. induction and/or during maintenance therapy after a minimum period of 16 weeks of treatment. Results In total, 61 IBD patients were included (mean age 38 years, range 22–70; 38 women; 54 CD/6 UC/1 IBD-U). All patients were antiTNF experienced, minority (11; 18%) had also been treated with vedolizumab prior UST. Thirty-nine pts (64%) were responders, out of these 15 pts (38%) required dose escalation at some point of the treatment due to secondary loss of response. UST through levels at week 8 were significantly higher than the maintenance levels (mean 5.6±SEM 0.7µg/mL vs. 2.2±0.3µg/mL; p<0.001). There were no significant differences between responders and non-responders neither in trough levels after induction (5±0.8µg/mL vs. 6.4±1.1µg/mL, p=n.s.), nor in trough levels during maintenance therapy (2.3± 0.4µg/mL vs. 1.9 ±0.4µg/mL, p=n.s.). Patients requiring dose escalation did not differ from stable responders in maintenance trough levels (2.4±0,6 µg/mL vs. 2,3 ±0,4 µg/mL). Conclusion In this limited size real-world cohort of IBD patients, we found no difference in pharmacokinetics between reponders and non-reponders to ustekinumab.