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Biologic Immunogenicity — SCE Rheumatology MCQ

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ModerateRheumatoid ArthritisBiologic ImmunogenicitySCE Rheumatology

A 45-year-old woman with seropositive rheumatoid arthritis achieved sustained low disease activity after starting adalimumab. Five years later, she develops recurrent objective synovitis despite confirmed adherence and correct injection technique. A pre-dose sample shows an undetectable adalimumab concentration, and a validated assay detects high-titre antibodies that bind adalimumab. Which mechanism best explains this secondary loss of response?

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Correct answer: D — Anti-adalimumab antibodies neutralising drug and accelerating immune-mediated clearance

Explanation lettering: D = shown as A · A = shown as B · B = shown as C · E = shown as D · C = shown as E

E is correct. Initial disease control followed by recurrence is secondary treatment failure. The combination of an undetectable trough concentration despite confirmed adherence and high-titre anti-adalimumab antibodies identifies immunogenic pharmacokinetic failure. These antibodies can neutralise adalimumab and promote its clearance, reducing bioavailable drug. Altered signalling or increased TNF production would not specifically explain the antibodies and absent trough level. CYP induction is incorrect because monoclonal antibodies are not cleared through conventional hepatic CYP metabolism. TNF-independent disease activity represents pharmacodynamic or mechanistic failure and is more likely when active disease persists despite an adequate adalimumab concentration. The UK SmPC directly associates anti-adalimumab antibodies with increased clearance and reduced efficacy.

Reference: Electronic Medicines Compendium. Humira 40 mg solution for injection in pre-filled pen, Summary of Product Characteristics, sections 4.5 and 5.1 (Immunogenicity), revised 2026. https://www.medicines.org.uk/emc/product/7986/smpc