P671 Ustekinumab in paediatric patients with moderately to severely active Crohn's disease: Results from the UniStar study long-term extension

Abstract Background Ustekinumab (UST) is an approved biologic for the treatment of adults with Crohn’s disease (CD). Through 16 weeks (wks), UST demonstrated high rates efficacy, low immunogenicity, and safety in paediatric patients (pts) similar to that observed adults.1 Here, we evaluated CD pts through 268 wks. Methods UniStar was a phase 1, multicentre, double-blind study (2-18 years old; body weight ≥10kg) moderately severely active CD. Pts (n=45) were randomised 1:1 stratified by (<40kg or ≥40kg) (3 mg/kg [<40kg]; 130 mg [≥40kg]) (9 390 dose intravenous UST. At wk 8, received 1 subcutaneous maintenance (2 90 [≥40kg]). responding at eligible enter long-term extension (LTE) continued dosing every 8 wks up 268. This reports safety, pharmacokinetics (PK), immunogenicity 16, 24, 48, 224, 240 wks, as applicable. The primary visit representing outcomes after ~1 year treatment. Results Of 44 treated UST, 34 (77%) responded entered LTE; number receiving 104, 152, 208 26 (77%), (47%), 12 (35%), (24%), respectively. Among LTE (n=34), baseline median age (range) 13.0 (6.0-17.0) years, 62% female, 47% weighed <40kg, 18% <30kg, 94% previously failed anti-tumor necrosis factor therapy. 41% (14/34) achieved clinical remission, 59% (20/34) response. proportion abnormal C-reactive protein (CRP) levels 71% (24/34), (16/27) normalization CRP (<3mg/L) 48. By final 240, 91% reported ≥1 adverse event (AE), 15% discontinued due AEs, worsening most frequent reason. Infections occurred 74% pts, 32% had serious AEs. majority AEs gastrointestinal disorders associated No injection-site reactions, infections, malignancies, deaths reported. Median serum concentrations tended be lower weighing <40kg compared ≥40kg, but generally consistent from remained detectable 200 (Figure). Incidence antibodies (1/34; 3%). Conclusion In LTE, PK, adult long 4 Reference: 1. Rosh JR et al. J Crohns Colitis. 2021;15(11):1931.