Background Dactylitis is a hallmark manifestation of psoriatic arthritis (PsA) and a key feature for PsA diagnosis. Active dactylitis is associated with a higher risk of erosions and can severely impact function. The therapeutic strategies for dactylitis are however largely empirical, with a profound absence of knowledge regarding efficacy, as primary endpoint, and impact on disease progression. The use of biologic DMARDs in patients with dactylitis, refractory to NSAIDs or local corticosteroids, is recommended by EULAR guidelines, over the use of conventional DMARDs, based in the scarcity of evidence and properly designed studies in this field.

Methods GO-DACT is an ongoing multicentric trial, involving 13 national Rheumatology departments. Patients older than 18 years, with the diagnosis of PsA and active dactylitis (tenderness score ≥1), refractory to NSAIDs, for 3 months, were included. Patients were randomised on a 1:1 ratio, to either MTX in combination with golimumab or placebo, for a period of 24 weeks. The primary aim of this trial is to determine differences of efficacy between the two treatment arms, in improving dactylitis (and enthesitis), as assessed by the Dactylitis Severity Score (DSS) at 24 weeks. Key secondary outcomes include: LDI, LEI, joint counts, PASI and NAPSI, HAQ, DLQI and composite indexes for disease activity. The effect of treatment arms, on different tissue compartments, will be analysed by contrast-enhanced MRI, with high resolution images for dactylitis, at baseline and 24 weeks.

Conclusions The results from GO-DACT are expected to have implications in clinical practice, bringing robust and valid data for the definition of dactylitis treatment stratification and algorithm. GO-DACT will also contribute to understand dactylitis pathogenesis through the assessment of treatment efficacy, namely in distinct tissue compartments as defined by MRI. https://www.clinicaltrials.gov (NCT02065713)