BACKGROUND:Mirikizumab, a humanised immunoglobulin G4 monoclonal antibody, targets the p19 subunit of IL-23, with demonstrated efficacy and safety in adults with ulcerative colitis and Crohn's disease. This study evaluated the pharmacokinetics, efficacy, and safety of mirikizumab in paediatric participants with moderately-to-severely active ulcerative colitis.
METHODS:This 52-week, multicentre, open-label, non-randomised, phase 2 study enrolled paediatric participants (2 to <18 years) with moderately-to-severely active ulcerative colitis with inadequate or loss of response or intolerance to corticosteroids, immunomodulators, biologics, or JAK inhibitors from 19 centres in Canada, Israel, Japan, South Korea, and the USA. Participants received induction doses of intravenous mirikizumab 5 mg/kg or 10 mg/kg (for bodyweight ≤40 kg) or 300 mg (bodyweight >40 kg) at weeks 0, 4, and 8. Clinical response was determined by the modified Mayo score (mMS). Responders at week 12 entered the maintenance period and received subcutaneous doses of mirikizumab 50 mg (bodyweight ≤20 kg), 100 mg (bodyweight >20 to ≤40 kg), or 200 mg (bodyweight >40 kg) every 4 weeks through week 48. Non-responders at week 12 received three additional intravenous induction doses (10 mg/kg [bodyweight ≤40 kg] or 300 mg [bodyweight >40 kg] every 4 weeks), before continuing to subcutaneous maintenance dosing. Here we present the secondary outcomes of safety and efficacy; pharmacokinetics (primary endpoint) data have been reported previously. The modified intention-to-treat and safety populations included participants who received at least one dose of treatment, regardless of adherence to the protocol or treatment. This study is registered with ClinicalTrials.gov, NCT04004611.
FINDINGS:26 participants were enrolled between May 18, 2020, and March 15, 2023; mean age was 11·8 years (SD 3·4) and mean weight was 40·5 kg (SD 16·0). 15 (58%) participants were female and 11 (42%) were male. At week 12, 18 (69·2%, 95% CI 50·0-83·5) participants had a clinical response by mMS, ten (38·5%, 95% CI 22·4-57·5) achieved clinical remission by mMS, 14 (53·8%, 95% CI 35·5-71·2) achieved endoscopic remission, four (15·4%, 6·2-33·5) had histologic-endoscopic mucosal improvement (HEMI), one (3·8%, 0·7-18·9) had histologic-endoscopic mucosal remission (HEMR), and 12 (46·2%, 28·8-64·5) achieved symptomatic remission. When assessed by Pediatric Ulcerative Colitis Activity Index (PUCAI), 20 (76·9%, 57·9-89·0) of the 26 participants had a clinical response, and ten (38·5%, 22·4-57·5) achieved clinical remission at week 12. At week 52, 14 (53·8%, 35·5-71·2) of 26 participants achieved mMS-based clinical response, ten (38·5%, 22·4-57·5) were in mMS-based clinical remission, 14 (53·8%, 35·5-71·2) had a PUCAI-based clinical response and 13 (50·0%, 32·1-67·9) were in PUCAI-based clinical remission. At week 52, ten (38·5%, 95% CI 22·4-57·5) of 26 patients were in endoscopic remission, nine (34·6%, 19·4-53·8) had HEMI, nine (34·6%, 19·4-53·8) had HEMR, and 12 (46·2%, 28·8-64·5) were in symptomatic remission. At week 52, ten (38·5%, 95% CI 22·4-57·5) of the 26 participants had achieved clinical remission without corticosteroid use or ulcerative colitis-related surgery for at least 12 weeks leading up to week 52. Three (12%) participants experienced serious adverse events across induction and maintenance periods (non-infective appendicitis, worsening of ulcerative colitis, and pseudarthrosis), of which one (4%; worsening of ulcerative colitis) led to study discontinuation. The most common adverse events were COVID-19 (in six [23%] of 26 participants); injection site pain (six [23%]); headache (five [19%]); pyrexia (four [15%]); and viral upper respiratory tract infection (four [15%]).
INTERPRETATION:Mirikizumab exhibited safety and efficacy in paediatric participants with moderately-to-severely active ulcerative colitis. These results support further evaluation of mirikizumab in the paediatric population.