Measuring Methotrexate Monotherapy Response in Early Rheumatoid Arthritis

In patients with early rheumatoid arthritis (RA), higher levels of baseline global DNA methylation has been linked to decreased clinical response to methotrexate (MTX) therapy, according to research published in Arthritis Research and Therapy.

Using blood samples collected from the multicenter, stratified, single-blind Treatment in the Rotterdam Early Arthritis Cohort, researchers assessed whether the presence of higher baseline global DNA (hydroxy)methylation was associated with clinical nonresponse to MTX therapy in the first 3 months of treatment in patients with early RA.

From the total cohort, genomic DNA was available for 294 patients (249 treatment-naïve patients and 257 patients at month 3 of MTX therapy). Mean age was 53.4±14.2 years, and 70.4% of the cohort were women. At baseline, the mean Disease Activity Score in 28 joints (DAS28) was 4.7±1.2, which decreased to 3.0±1.2 over 3 months.

The mean global DNA methylation did not change significantly (P =.454) over the first 3 months of therapy; conversely, global DNA hydroxymethylation did significantly increase, at a rate of 0.0008% over the first 3 months. Using a crude univariate linear regression model, investigators found that baseline global DNA methylation was associated with ΔDAS28 over 3 months (beta coefficient [B]=1.36; P =.044). In a crude univariate model, baseline global DNA hydroxymethylation was not significantly associated with ΔDAS28; this finding held following adjustment for baseline DAS28, erythrocyte folate, body mass index, age, and sex (B=6.90; P =.664).

At 3 months of therapy, both global DNA methylation and global DNA hydroxymethylation were associated with ΔDAS28 (B=.40; P =.471 and B=12.52; P=.517, respectively). In addition, after 3 months of therapy, differences between baseline and DNA (hydroxy)methylation were not associated with changes in DAS28 (Δmethylation B=−0.68, P=.182; Δhydroxymethylation B=−1.55, P=.925).

Finally, patients were stratified by therapy type, and univariate linear regression analyses were performed to determine if the baseline global DNA methylation and disease activity responses were specific to MTX, not a result of combination therapy. Investigators found that the effect size was 1.8-fold higher in the MTX monotherapy group vs the triple therapy group (B=2.06, P=.074 and B=1.12, P=.173, respectively); these associations were not significant.

Limitations of the study were that a majority of patients were treated with MTX-combination therapy, and the study’s replication into larger MTX monotherapy studies should be performed.

“These results show that higher baseline global DNA methylation in treatment-naïve [patients with early RA] is associated with decreased clinical response after 3 months of treatment,” the researchers of the study concluded. “[T]he underlying pathway, as well as the potential added value of global DNA methylation in a prediction model for MTX response requires further exploration.”

Reference

Gosselt HR, van Zelst BD, de Rotte MCFJ, Hazes JMW, de Jonge R, Heil SG. Higher baseline global leukocyte DNA methylation is associated with MTX non-response in early RA patients. Arthritis Res Ther. 2019;21:157.