Background/Purpose: A large proportion of psoriatic arthritis (PsA) patients are prescribed a tumour necrosis factor inhibitor (TNFi) in combination with methotrexate (MTX), however the value of combination therapy in PsA remains unresolved. This study aimed to investigate whether TNFi combination therapy with conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) is more effective 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). Adults (≥18 years) with a clinical diagnosis of PsA who were new (first line) users of TNFi during the study period and registered in their respective database from TNFi initiation were eligible for inclusion. Exposure treatment groups at baseline included TNFi monotherapy, TNFi combination therapy with any csDMARD and a subgroup of TNFi combination therapy with MTX. 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 and 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: There were 2294 eligible patients identified from the contributing databases, of which 34% started TNFi in monotherapy and 66% in combination therapy. Patient characteristics and baseline disease activity and severity were generally similar across treatment groups within the databases. The majority of patients (82% monotherapy and 66% combination therapy) did not have changes to their baseline treatment regimen before discontinuing their first TNFi. In the Swiss (p=0.002), Greek (p=0.021) and Bath (p=0.014) databases, patients starting treatment on TNFi in combination with MTX had longer drug survival compared to monotherapy, whilst in Italy patients starting on monotherapy persisted longer (p=0.030) (Table 1). In all but the Czech database, men persisted significantly longer on their first TNFi than women (Table 1). In the combined Italian/Swiss dataset (n=1066) there was no significant difference in the rate of change of DAS28 between those on TNFi monotherapy versus TNFi combination with any csDMARD (combined Relative Risk (RR_adj) 0.98 CI₉₅ 0.95-1.03) or when compared to those on TNFi+MTX (RR_adj 0.98 CI₉₅ 0.95-1.02). Similarly, when also including the Bath cohort (n=1205), there was a comparable rate of change of HAQ in patients on TNFi monotherapy compared with combination with any csDMARD (RR_adj 1.01 CI₉₅ 0.99-1.04) and when compared to those on TNFi+MTX combination (RR_adj 1.02 CI₉₅ 0.99-1.05).

Conclusion: Combination therapy of a TNFi with a csDMARD does not appear to affect improvement of disease activity or HAQ. Combination therapy may, however, improve TNFi drug survival. Gender appears to be a major risk factor in determining TNFi survival, with males persisting on treatment for longer.

Table 1_Thomas et al.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tumour-necrosis-factor-inhibitor-monotherapy-versus-combination-therapy-with-conventional-synthetic-disease-modifying-anti-rheumatic-drugs-for-the-treatment-of-psoriatic-arthritis-a-combined-analysis/