Background Methotrexate (MTX) is a first-line therapy in early Rheumatoid Arthritis (RA). However, ∼30% of treated patients do not respond to the medicine or need to abrogate treatment because of severe adverse events. Since MTX interferes with the folate cycle and thereby influences the methylation cycle, we hypothesize that methylation status at start therapy is associated with response and adverse events after three months of MTX treatment enabling personalized medicine.

Objectives Examine global methylation status of early Rheumatoid Arhtritis patients before and after 3 months of MTX use between responders and non-responders and patients that do or do not experience adverse events.

Methods To assess global methylation status, DNA was isolated at baseline from whole blood of 120 patients from the Treatment in the Rotterdam Early Arthritis Cohort (tREACH), a multicenter, stratified single-blind clinical trial of patients with early RA. Methylation status of 7 CpG sites within Long-interspersed nuclear elements (LINE-1) were analyzed and quantified by Matrix Assisted Laser Desorption Ionization time of flight Mass Spectrometry (MALDI-TOF MS). Results were compared between MTX responders and non-responders based on a low disease activity (DAS28 <3.2) at three months of treatment and patients experiencing ≤2 or ≥3 adverse events. Gastrointestinal adverse events were assessed separately.

Results No statistical differences in the mean of 7 LINE-1 CpGs were observed between responders and non-responders, nor in patients experiencing ≤2 or ≥3 adverse events. However, methylation status of specific CpG sites within LINE-1 did show significant changes. Baseline CpG_2 methylation levels were positively correlated with the DAS28 score at t3 (p=0.018) and baseline methylation levels in CpG_5 and CpG_8.9 were significantly higher in patients experiencing ≥3 adverse events (p=0.018 and p=0.034, respectively). Besides, CpG_5 methylation levels were particularly increased in patients experiencing gastrointestinal adverse events (p=0.038).

Conclusions Global methylation status is associated with non-response and adverse events to MTX in early RA patients and can therefore be implemented in future prediction models.

Disclosure of Interest None declared