Tumour Necrosis Factor Inhibitor monotherapy versus combination therapy for the treatment of psoriatic arthritis: combined analysis of European biologics databases.

OBJECTIVE: To investigate whether tumour necrosis factor inhibitor (TNFi) combination therapy with conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) is more effective for psoriatic arthritis (PsA) and/or improves TNFi drug survival compared to TNFi monotherapy. METHODS: Five PsA biologics cohorts were investigated between 2000 and 2015; the ATTRA registry (Czech Republic), the Swiss Clinical Quality Management PsA registry, the Hellenic Registry of Biologics Therapies (Greece), the University of Bari PsA biologics database (Italy) and the Bath PsA cohort (UK). Drug persistence was analysed using Kaplan-Meier and equality of survival using Log-Rank tests. Comparative effectiveness was investigated using logistic regression with propensity scores. Separate analyses were performed on: (a) the combined Italian/Swiss cohorts for change in rate of DAS-28; and (b) the combined Italian, Swiss and Bath cohorts for change in rate of HAQ. RESULTS: In total, 2294 patients were eligible for the drug survival analysis. In the Swiss (p=0.002), Greek (p=0.021) and Bath (p=0.014) databases patients starting TNFi in combination with MTX had longer drug survival compared to monotherapy, whilst in Italy the monotherapy group persisted longer (p=0.030). In patients from the combined Italian/Swiss dataset (n=1066) there was no significant difference between treatment arms in rate of change of DAS28. Similarly, when also including the Bath cohort (n=1205) there was no significant difference in rate of change of HAQ. CONCLUSION: Combination therapy of a TNFi with a csDMARD does not appear to affect improvement of disease activity or HAQ versus TNFi monotherapy but may improve TNFi drug survival.