Subcutaneous infliximab in pediatric inflammatory bowel disease: Sustained remission, predictable pharmacokinetics,...

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.

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.

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.

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.