Monocytes from inflammatory arthritis patients accumulate methotrexate and their transcriptome predicts methotrexate clinical response

TL;DR

This study shows that methotrexate accumulates in monocytes from arthritis patients and that gene patterns in these cells can predict treatment response.

Contribution

The study identifies monocyte transcriptome changes and gene markers that predict methotrexate effectiveness in arthritis patients.

Findings

Methotrexate suppresses inflammation in whole blood 5 days after treatment.

Methotrexate polyglutamates accumulate in monocytes and alter their gene expression.

Non-classical monocyte genes predict better methotrexate clinical response.

Abstract

Monocytes and monocyte-derived macrophages play a key pathogenic role in inflammatory arthritis. Methotrexate (MTX) is the first-line disease-modifying antirheumatic drug (DMARD) for arthritis, yet the mechanisms and kinetics of its effects on monocyte/macrophages remain poorly understood. We have now investigated the temporal dynamics of the MTX's anti-inflammatory action by initially performing a phase I clinical trial (METOMAC) on healthy individuals following a single MTX dose, which revealed that MTX plasma levels peak at 1 h after MTX treatment, with maximal suppression of LPS-induced IL-1β and IL-6 in whole blood 5 days after MTX exposure. Building on these findings, we performed an observational clinical study (METOMAC-PAC) on 29 DMARD-naïve early arthritis patients receiving a weekly dose of MTX over a 3 month period. The METOMAC-PAC study revealed that MTX polyglutamates (MTX-PG) accumulates in peripheral blood monocytes, where MTX-PG is detected as early as 5 days post-treatment, and modulates the monocyte gene profile after 4 MTX doses, with specific enrichment of the aryl-hydrocarbon receptor (AhR)-molecular signature and genes coding for anti-inflammatory factors. Importantly, stratification of METOMAC-PAC patients according to their clinical response revealed that Good Responders exhibit increased expression of “non-classical monocyte”-specific genes (MAF, FCGR3B, ICAM4) both before and after MTX treatment, while Partial Responders patients showed a higher baseline expression of genes preferentially expressed by “classical monocytes”. Our results elucidate the kinetics of the anti-inflammatory action of MTX, demonstrate that MTX modulates the monocyte transcriptional signature in vivo, and identify “non-classical monocyte”-associated genes as predictors for an effective MTX clinical response.

The online version contains supplementary material available at 10.1007/s00018-026-06162-9.

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