Subcutaneous infliximab in pediatric inflammatory bowel disease: Sustained remission, predictable pharmacokinetics, and real‐world US implementation

Abstract Objectives Subcutaneous infliximab (IFX‐SC) offers a convenient alternative to intravenous infliximab (IFX‐IV) in inflammatory bowel disease (IBD) with more stable concentrations. Pediatric experience remains limited. We evaluated sustained clinical remission, pharmacokinetics, and safety/tolerability after transition from IFX‐IV to IFX‐SC in children with IBD. Methods Prospective, single‐US‐center cohort of patients <18 in clinical remission on maintenance IFX‐IV who transitioned to IFX‐SC (2022–2025). Demographic, clinical, and pharmacokinetic data were collected. The primary outcome was sustained clinical remission (defined: Harvey–Bradshaw Index ≤ 4 or partial Mayo Score ≤ 2) ≥ 12 weeks (T1) after transition with no corticosteroids/hospitalization/surgery/therapy‐cessation. Secondary outcomes were change in IFX concentrations, sustained remission at last follow‐up, and safety/tolerability. Results Of 36 prescribed, 22 (61%) initiated therapy (median age 15 14–17 years; 73% Crohn's disease; 82% 120 mg q2 weeks); age‐related insurance denial stopped 12/14 from starting. Sustained clinical remission at T1 and last follow‐up (median 215 162–273 days) was achieved in 20/22 (91%). Median IFX concentrations increased from 14.1 9.7–22.4 µg/mL (IV trough) to 29.5 23.1–35.0 µg/mL (SC steady‐state)—a median 1.9 1.5–2.9‐fold increase in paired samples. Two with prior anti‐drug antibodies cleared them after switching. Adverse events were mild: injection‐site pain ( n = 4, one discontinued), transient pruritus ( n = 1), device misfire ( n = 1), worsening psoriasiform dermatitis ( n = 1, discontinued); no serious adverse events or anaphylaxis occurred. Conclusions Transition to IFX‐SC maintained remission with an excellent safety profile. Steady‐state IFX‐SC levels approximated twice prior therapeutic IV troughs. Expanded labeling should be considered to ensure access reflects clinical necessity rather than administrative barriers.