Objectives: To investigate the extent antibodies to adalimumab are formed in patients with plaque psoriasis and whether these antibodies have clinical consequences. Also, to examine the relationship between antibodies to adalimumab and adalimumab trough titers.
Design: Prospective observational cohort study.
Setting: Two Dutch dermatology departments in university hospitals.
Patients: All consecutive patients starting a regimen of adalimumab for chronic plaque psoriasis. Patients were screened and fulfilled the Dutch reimbursement criteria for adalimumab to treat psoriasis.
Intervention: Adalimumab treatment (per label).
Main outcome measures: The titer of antibodies to adalimumab, the adalimumab trough concentration, and the Psoriasis Area and Severity Index at weeks 12 and 24.
Results: Antibodies to adalimumab were detected in 13 of 29 patients (45%) during 24 weeks of treatment. Differences in response rates among patients with low, high, and no titers of antibodies to adalimumab were significant at weeks 12 and 24 (P = .04 and P < .001, respectively). The median adalimumab trough concentrations varied significantly among patients with low, high, and no titers of antibodies to adalimumab (1.30 [range, 0.01-5.50], 0.0 [range, 0.0-0.0], and 9.6 [range, 0.0-22.6] mg/L, respectively; P < .001). At week 24, the median adalimumab trough concentrations also differed significantly among good responders, moderate responders, and nonresponders (9.7 [range, 0.0-22.6], 8.9 [range, 3.2-12.6], and 0.0 [range, 0.0-13.3] mg/L, respectively; P = .01).
Conclusion: Antibodies to adalimumab are associated with lower serum adalimumab trough concentrations and with nonresponse or loss of response to adalimumab in patients with plaque psoriasis.