Real-world implementation and outcomes of adalimumab therapeutic drug monitoring in psoriasis: a national specialised centre experience.

Serum adalimumab concentration is a biomarker of treatment response but therapeutic drug monitoring (TDM) is yet to be implemented in routine psoriasis care. We incorporated adalimumab TDM in a national specialised psoriasis service and evaluated it using the RE-AIM implementation science framework. We undertook pre-implementation planning (validating local assays) and implementation interventions targeted to patients (pragmatic sampling at routine reviews), clinicians (introduction of TDM protocol) and healthcare systems (adalimumab TDM as a key performance indicator). Over 5-months, 170 of 229 (74%) individuals treated with adalimumab received TDM. Clinical improvement following TDM-guided dose escalation occurred in 13 of 15 (87%) non-responders with serum drug concentrations <8.3μg/ml (median PASI reduction 3.2 [IQR 2.2-8.2] after 23.4 weeks), and in all non-responders who had TDM-guided switch in biologic due to supratherapeutic drug concentrations (>8.3μg/mL; n=2) or positive anti-drug antibody (n=2) (PASI reduction 7.8 [7.5-12.9] after 20.0 weeks). Proactive TDM led to dose reduction in 5 individuals with clear skin and sub- or supra-therapeutic drug concentrations; 4 (80%) sustained clear skin after 50 [42-52] weeks. Adalimumab TDM based on pragmatic serum sampling is clinically viable and may lead to patient benefit. Context-specific implementation interventions and systematic implementation assessment may bridge the biomarker research-to-practice gap.