Methotrexate Enhances Apoptosis of Transmembrane TNF-Expressing Cells Treated With Anti-TNF Agents

Anti-inflammatory effects of infliximab and methotrexate on peripheral blood and synovial fluid mononuclear cells: ex vivo study

OBJECTIVE

To investigate the effects of methotrexate (MTX) and the tumour necrosis factor inhibitor infliximab (IFX) on immune cells derived from peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) of inflammatory arthritis patients.

METHOD

Phytohaemagglutinin (PHA)-induced proliferation of healthy donors' PBMCs and synovial intermediate monocytes (CD14+CD16+ cells) in SFMCs derived from psoriatic arthritis (PsA) and rheumatoid arthritis (RA) patients was determined by flow cytometry following co-culture with IFX and MTX. PHA-induced interferon-γ (IFN-γ) production in PBMCs was measured by enzyme-linked immunosorbent assay. The drugs' effect on mRNA expression in SFMCs was determined by quantitative polymerase chain reaction.

RESULTS

The combination of IFX 10 μg/mL + MTX 0.1 μg/mL had the strongest inhibitory effect on PBMC proliferation (91%), followed by MTX 0.1 μg/mL (86%) and IFX 10 μg/mL (49%). In PHA-stimulated PBMCs, IFN-γ production was reduced by IFX 10 μg/mL, MTX 0.1 μg/mL, and IFX 10 μg/mL + MTX 0.1 μg/mL by 68%, 90%, and 85%, respectively. In SFMCs, IFX 10 µg/mL significantly reduced CD14+CD16+ cells compared to medium (PsA 54%, p < 0.01; RA 46%, p < 0.05), while MTX had no effect on this population. IFX + MTX led to a similar suppression of CD14+CD16+ cells as achieved by IFX alone. The drugs had different impacts on SFMC gene expression.

CONCLUSION

Both IFX and MTX effectively inhibited PBMC proliferation and IFN-γ production, but only IFX reduced synovial monocytes and pro-inflammatory gene expression in SFMCs, suggesting a differential impact of IFX and MTX on critical inflammatory cell populations ex vivo.

Quantifying the Effect of Methotrexate on Adalimumab Response in Psoriasis by Pharmacokinetic-Pharmacodynamic Modeling

Previously, we showed that the combination of methotrexate and adalimumab treatment leads to less antidrug antibody development. In this study, we quantify the pharmacokinetics/pharmacodynamics (PK/PD) of adalimumab and evaluate the influence of methotrexate cotreatment. A population PK-PD model was developed using prospective data from 59 patients with psoriasis (baseline PASI = 12.6) receiving adalimumab over 49 weeks. Typical PK and PD parameters and their corresponding interpatient variability were estimated. We performed a covariate analysis to assess whether interpatient variability could be explained by addition of methotrexate and other covariates. In total, 330 PASIs, 252 adalimumab serum concentrations, and 247 antidrug antibody titers were available. Presence of antidrug antibodies (adalimumab group = 46.7%, adalimumab + methotrexate group = 38.7%; P = .031) was correlated with increased adalimumab apparent clearance (P < .001). In the PD model, the use of concomitant methotrexate was borderline to significantly correlated with a decreased half-maximal inhibitory concentration (adalimumab concentration for which clinical response score is reduced by half; P < .10). On the basis of our PK-PD model, concomitant use of methotrexate indirectly increases adalimumab concentration, partially through less antidrug antibodies formation, which may result in better efficacy.