Maarten Cozijnsen

101 Chapter 5 Adalimumab therapy in children with infliximab-refractory CD Previous treatment Thirty-two patients (60%) had received at least 1 course of exclusive enteral nutrition, 50 (94%) had been treated with steroids, 27 (51%) with mesalazine, 52 (98%) with purine antimetabolites (azathioprine and/or mercaptopurine) and 26 (49%) with methotrexate. The median duration of infliximab treatment was 15.6 months (IQR 10.8-25.8). Reasons to stop with infliximab were non-response (n=3, 6%), loss of response (n=34, 64%), allergic reactions (n=11, 21%) or side effects (n=5, 9%). In a large subgroup (n= 38, 72%) antibodies to infliximab (ATI) had been tested prior to adalimumab commencement. Twenty-one of those had tested positive (ATI concentration > 15 AE/ml), 16 of whom (76%) had lost response to infliximab, 3 (14%) had developed an allergic reaction and 2 (10%) had suffered side effects. The other 17 patients had tested negative for ATI (2 with non-response, 11 who lost response, 3 with allergic reactions and 1 with side effects). Twelve patients (23%) had undergone partial or total bowel resection prior to adalimumab commencement, at a median age of 14 years (IQR 11-14), a median of 21 months before the start of adalimumab therapy (IQR 11-33). Adalimumab treatment Adalimumab induction regimens differed. Thirty-nine patients (74%) started with a double dosage prior to maintenance treatment, the remainder received the maintenance dosage straight from the start. Initial maintenance dose were based on body weight (20-40 mg for patients less than 40 kg, 40-80 mg for patients above 40 kg). Treatment escalation was needed in 13 patients (25%), performed by either increasing the dose, shortening the dose interval, or both. At the start of adalimumab 41 patients (77%) were using concomitant CD related medication, including immunomodulators (thiopurines (n=21) or methotrexate (n=11)), steroids (n=7) or exclusive enteral nutrition (n=2). Response to adalimumab We followed the children and teenagers in our cohort for a total of 66 patient-years, i.e. for a median of 12 months per patient (IQR 5-23). In 95% of the follow-up visits disease activity was assessed by either the wPCDAI (45%) or the PGA (50%). For the remainder this was not possible. The timing of the follow-up visits differed by a median of 14% (IQR 5-27) from the presented time-points.