Population pharmacokinetic and exposure–efficacy analysis of ixekizumab in paediatric patients with moderate‐to‐severe plaque psoriasis (IXORA‐PEDS)

AIMS: Ixekizumab is a high‐affinity monoclonal antibody that selectively targets interleukin‐17A used in the treatment of adult and paediatric patients with moderate‐to‐severe psoriasis. This analysis evaluated the pharmacokinetics (PK) of ixekizumab and the exposure–efficacy relationship in paediatric patients aged 6 to <18 years with psoriasis. METHODS: Population PK and exposure–efficacy models were developed. The models used data from paediatric patients with psoriasis participating in the Phase 3 IXORA‐PEDS trial in which patients were dosed according to weight categories. The exposure–efficacy model is a Psoriasis Area and Severity Index (PASI) time course model using data up to Week 12, a co‐primary efficacy endpoint. RESULTS: A 2‐compartment population PK model describes the PK of ixekizumab in paediatric patients with the effect of body weight incorporated on clearance and volume terms using an allometric relationship. The weight category‐based dosing ensured that ixekizumab mean trough serum concentrations in paediatric patients with psoriasis (3.20–3.33 μg/mL) were within the range of concentrations observed in adult patients with psoriasis (mean [standard deviation]: 3.48 [2.16] μg/mL) administered an efficacious dosing regimen. The observed PASI response rates at Week 12 in paediatric patients (91.9/81.8/52.5% for PASI75/90/100) are well predicted by the final exposure–efficacy model and response rates are similar or higher than those achieved in adults (86.2/66.6/35.0% for PASI75/90/100). CONCLUSION: This analysis is the first to describe the PK and exposure–efficacy relationship of ixekizumab in paediatric patients with psoriasis. The analyses support the selection of the weight category‐based ixekizumab dosing regimens approved for use in paediatric patients with psoriasis.