Methotrexate and leflunomide combination therapy in psoriatic arthritis

INTERVENTION: Patients will be randomised 1:1 into two groups. Arm 1: methotrexate monotherapy (methotrexate 25 mg once weekly plus 2 placebo tablets daily) Arm 2: methotrexate and leflunomide combination therapy (methotrexate 25 mg once weekly plus 2 leflunomide 10 mg tablets daily) CONDITION: Psoriatic arthritis Artritis psoriatica PRIMARY OUTCOME: Primary endpoint is the difference in efficacy between monotherapy MTX and combination therapy MTX plus LEF on the Psoriatic Arthritis Disease Activity Score (PASDAS) at 16 weeks. SECONDARY OUTCOME: Key secondary parameters are: change in skin score, enthesitis score, dactylitis score and swollen/tender joint count. Furthermore, the difference in immunoprofile, treatment failure, and the percentage of (S)AE’s between the two groups will be assessed. INCLUSION CRITERIA: ‐Adult male or female ‐Age ≥16 years ‐Clinical diagnoses of Psoriatic arthritis ‐Evidence of active disease defined as ≥2 swollen joints, dactylitis counts as 1 swollen joint ‐Subjects that have used cDMARDs and/or bDMARDs before, must have discontinued this treatment for at least 6 months prior to baseline visit ‐Subjects who are already taking NSAIDs/COX‐2 inhibitors may participate in the study but the dose has to be stable for at least one week prior to first dose of study drug ‐Oral or injected corticosteroids (intramuscular, intravenous and intra‐articular) have to be discontinued 8 weeks prior to first dose of study drug ‐If fumaric acid is used at baseline, this will be discontinued and switched to study medication (according to usual care)