Patients with rheumatoid arthritis (RA) usually receive triple therapy with methotrexate (MTX), leflunomide (LEF) and infliximab (IFX), but nearly one-third of them do not respond to triple therapy. This study aimed to identify biomarkers for predicting the efficacy of triple therapy to optimize personalized treatment of RA.

All 20 enrolled patients met 2010 ACR/EULAR criteria for RA and were classified into good, moderate and non-responders (GR, MR, NR) for triple therapy. The Responders (R) were defined as the sum of GR and MR. Protein profiles of 4 responders and 4 non-responders were investigated via isobaric tags for relative and absolute quantification (iTRAQ), and differentially expressed proteins (DEPs) with high-confidence peptides were validated in 15 responders and 5 non-responders by parallel response monitoring (PRM).

iTRAQ identified 51 DEPs between responders and non-responders (p < 0.05, fold change >±1.2). The top five up-regulated DEPs were B7Z7M2, A0A087WZR4, Q53FL1, P08254 and G3V2V8, while the top five down-regulated proteins were Q6MZX9, B3KP77, P0DJI9, P0DJI8 and P02787. Targeted mass spectrometry by PRM identified 10 candidate biomarkers, and 3 DEPs including fibrinogen beta chain, epididymal secretory protein Li 282 and testicular tissue protein Li 70 were confirmed as predictive biomarkers.

This study demonstrated the feasibility of exploring biomarkers by applying iTRAQ and PRM mass spectrometry techniques, and a panel of biomarkers were identified to predict clinical response of IFX + MTX + LEF treatment in active RA patients.