Background: Biologic disease modifying anti-rheumatic drugs (bDMARDs) are known to be effective in controlling disease activity and reducing radiographic progression in patients with rheumatoid arthritis (RA) who have failed methotrexate (MTX). The cost-effectiveness of bDMARDs in comparison to combination conventional synthetic DMARD (csDMARD) therapy in Asian countries has not been well studied, and their place in the DMARD escalation algorithm is unclear.

Objectives: To assess the cost-effectiveness of step-up combination csDMARD versus bDMARD therapy for patients who have failed initial MTX monotherapy over one year.

Methods: We prospectively recruited all adult patients with inflammatory polyarthritis (IP) affecting ≥2 peripheral joints and symptom onset after September 1, 2012 from the only two hospitals serving Western Singapore to the Singapore Early Arthritis Cohort (SEAC). Baseline data on demographics, time of symptom onset and DMARD prescription, utility values (EQ-5D) and costs were collected by face to face interview, chart review, hospital financial records and assessment by a trained nurse. A cost-effectiveness analysis (CEA) was then performed using a decision tree comparing four sequences of DMARD therapy: MTX and infliximab, MTX and etanercept, triple therapy (TT) [MTX, sulphasalazine (SSZ) and hydroxychloroquine (HCQ)] and combination MTX and HCQ. An effective treatment was defined as achieving Disease Activity Score 28 (DAS28 (ESR)<2.6; “remission”). A treatment switch to a rescue therapy (MTX and adalimumab) was factored in case of not achieving remission or if serious adverse event was experienced. Cost and utility (using Singapore preference weights¹) information were derived from patients diagnosed with rheumatoid arthritis in the SEAC database as of June 16, 2017. Efficacy, rates of adverse events, disutility from adverse events, indirect costs and cost of serious adverse events were assumed from literature. One-way and probabilistic sensitivity analysis with 10,000 runs was performed.

Results: For the base case, the treatment with MTX and etanercept was dominated by conventional TT. The incremental cost of switching from TT to MTX and infliximab was SGD$16,118. The net gain in quality-adjusted life years (QALY) was 0.02. The incremental cost-effectiveness ratio (ICER), representing the additional cost of one unit of QALY gained by MTX and infliximab compared with TT, was $1,024,785/QALY. The probabilistic sensitivity analysis predicted that triple therapy would be the preferred treatment (89.6%) at a willingness-to-pay threshold of SGD$70,000.

Conclusions: Our model suggests that the ICER of bDMARD therapies explored do not compare favorably to csDMARD therapies. In the Singapore context, societal funding for bDMARDs can only currently be recommended after failure of combination csDMARD.

Reference:

1. Nan L, Wang P, Thumboo J, Lim YW, Vrijhoef HJM. Pharmacoeconomics 2014;32(5):495–507.

Disclosure of Interest: None declared

DOI: 10.1136/annrheumdis-2018-eular.4487