Methotrexate (MTX) co-medication can improve the therapeutic effect of biological therapies (e.g. TNF-inhibitors) in rheumatoid arthritis (RA), but its role in Psoriatic Arthritis (PsA) remains unclear. Differences in phenotypical manifestations between PsA and RA might influence the impact of co-medication, treatment response and treatment adherence differently.~Independent from this data, the impact of use of MTX in Ustekinumab (UST) treated patients with active PsA remains unclear: No data from Randomized Clinical Trials (RCTs) are available to address the questions whether add-on of MTX to UST monotherapy, or the other way around, a withdrawal of continuous MTX therapy in patients with newly initiated UST treatment or simultaneously induction of MTX with UST in patients will influence outcome.~There is some evidence that MTX may contribute to improved treatment persistence with anti-TNF therapy, particularly when used in combination with infliximab, but there is very little data to support a benefit in effectiveness in patients receiving concomitant MTX.~Additionally, MTX may play a role in immunogenicity: In the PSUMMIT program the patients with concomitant MTX had lower anti-drug-antibody (ADA) rates than those on UST-monotherapy, although there was no effect on efficacy and safety.~Furthermore, methotrexate treatment manifestations such as dactylitis or enthesitis seems to be ineffective.~In this study, the effect of blinded MTX-co-medication on outcome in patients treated with UST will be analysed. Differences on efficacy, safety and treatment adherence will be calculated related to MTX use in four arms of the stratified, randomized placebo-controlled clinical trial which contains a study treatment period of 52 weeks. The primary endpoint, differences in DAS28 in the treatment groups, will be measured at week 24.
Methotrexate (MTX) co-medication can improve the therapeutic effect of biological therapies (e.g. Tumor necrosis factor (TNF) -inhibitors) in rheumatoid arthritis (RA), but its role in Psoriatic Arthritis (PsA) remains unclear.~No data from Randomized Clinical Trials (RCTs) are available to address the questions whether add-on of MTX to UST monotherapy, or a withdrawal of continuous MTX therapy in patients with newly initiated Ustekinumab (UST) treatment or simultaneously induction of MTX with UST in naive active PsA-patients will influence outcome measurements.~So, the purpose of the study is to analyse the effects of blinded MTX-co-medication on outcome in patients treated with UST: Non-inferiority at week 24 of UST monotherapy compared to add-on to MTX in patients with active PsA and at least 12 weeks of MTX treatment prior to screening or who are actually not treated with MTX and do not have prior inadequate response to MTX-treatment for PsA will be demonstrated.