The inexorable increase of biological exposure in paediatric Inflammatory Bowel Disease: a Scottish, population-based, longitudinal study

Background: The use of biologics in paediatric-onset inflammatory bowel disease (PIBD) is rapidly changing. Aims: To identify the incidence and prevalence of biologic use within Scottish PIBD services, and to describe patient demographics and outcomes for those patients who required escalation of therapy beyond anti-tumour necrosis factor alpha (anti-TNFα) agents. Methods: We captured a nationwide cohort of prospectively identified patients less than 18 years of age with PIBD (A1 phenotype; diagnosed <17 years of age) within paediatric services over a 4.5-year period (1 January 2015–30 June 2019). All patients who received infliximab, adalimumab, vedolizumab or ustekinumab during the study period and/or received their first dose of these biologics were audited retrospectively. Results: Scotland-wide PIBD-prevalence cases increased from 554 to 644 over the study period. A total of 495 incident new-start biological therapies were commenced on 403 PIBD patients: 295 infliximab (60%), 161 adalimumab (32%), 24 vedolizumab (5%) and 15 ustekunumab (3%). The proportion of new-start biologics changed with infliximab initiation rates decreasing (87%–54%) while adalimumab (13%–31%), vedolizumab (0%–9%) and ustekinumab (0%–6%) all increased. The incidence rate (first dose of new biologic not including biosimilar switch) increased from 6.9% to 8.1% over the study period and point prevalence rates (any biologic use) increased from 20.2% to 43.5% - an average annual percentage increase of 20%. Biosimilar penetration of new-start anti-TNFα agents increased from 3% to 91%. Demographics and outcomes of those patients receiving vedolizumab and ustekinumab were similar. Conclusions: Complete accrual of Scottish nationwide biologic usage within paediatric services demonstrates a rapidly changing, inexorably increasing PIBD biologics landscape.