Therapeutic Drug Monitoring — SCE Rheumatology MCQ

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HardRheumatology PharmacologyTherapeutic Drug MonitoringSCE Rheumatology

A 55-year-old man with RA on Adalimumab and Methotrexate has therapeutic drug monitoring performed. His Adalimumab trough level is very low (<0.1 mg/L) and anti-drug antibodies are strongly positive. What is the most appropriate management?

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Correct answer: B — Switch to a different biologic (same or different mechanism)

Very low trough levels with high anti-drug antibody (ADA) titres indicate neutralising immunogenicity. The biologic is being rendered ineffective by the patient's immune response. BSR biologic safety guidelines and emerging therapeutic drug monitoring evidence suggest that switching biologic (either within class or to a different mechanism) is more appropriate than dose escalation which simply provides more drug to be neutralised. Optimising concomitant Methotrexate (which reduces immunogenicity) is important for the next biologic. TDM-guided management is increasingly used to personalise biologic therapy.

Reference: BSR 2019 biologic safety guidelines; Krieckaert CL et al 2012 TDM in RA biologics