Prolongation of the per label biologic dosing interval was feasible in approximately 30% of patients with psoriasis with stable minimal disease activity and can reduce costs in clinical practice. Baseline serum trough concentrations were not predictive for successful dosing interval prolongation.

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All 3 commercially available assays seem suitable for therapeutic drug monitoring of anti-TNFα drugs, allowing sensitive and comparable detection of infliximab, adalimumab, and etanercept concentrations, however with differences in specificity and recovery.

BackgroundThe introduction of anti-tumor necrosis factor medications has revolutionized the treatment of psoriasis with achievement of treatment goals (Psoriasis Area and Severity Index score 75, remission) that are not usually met with conventional systemics. Nevertheless, some patients continue to experience persistent disease activity or treatment failure over time. Strategies to optimize treatment outcomes include the use of concomitant methotrexate, which has demonstrated beneficial effects on pharmacokinetics and treatment efficacy in psoriasis and other inflammatory diseases.MethodsThis is an investigator-initiated, multicenter randomized controlled trial (RCT) designed to compare the combination treatment of adalimumab and methotrexate with adalimumab monotherapy in patients with psoriasis. The primary outcome is adalimumab drug survival at week 49. Other outcomes include improvement in disease severity and quality of life, tolerability, and safety. Moreover, anti-adalimumab antibodies and adalimumab serum concentrations will be measured and correlations between genotypes and clinical outcomes will be assessed. Patient recruitment started in March 2014. Up to now, 36 patients have been randomized. Many more patients have been (pre)screened. A total of 93 patients is desired to meet an adequate sample size. In our experience, the main limitation for recruitment is prior adalimumab therapy and intolerability or toxicity for methotrexate in the past.DiscussionOPTIMAP is the first RCT to examine combination therapy with adalimumab and methotrexate in a psoriasis population. With data derived from this study we expect to provide valuable clinical data on long-term treatment outcomes. These data will be supported by assessment of the impact of concomitant methotrexate on adalimumab pharmacokinetics. Furthermore, the influence of several single nucleotide polymorphisms on adalimumab response will be analyzed in order to support the development of a more personalized approach for this targeted therapy.Trial registration NTR4499. Registered on 7 April 2014.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-017-1777-y) contains supplementary material, which is available to authorized users.