Guo X, et al. - A 24-week placebo (PBO)-controlled trial was done to clarify mechanisms of action and identify peripheral biomarkers related to therapeutic responses of granulocyte-macrophage colony-stimulating factor (GM-CSF) antagonism in rheumatoid arthritis (RA). These outcomes showed the relationship of peripheral biomarker changes with therapeutic response to mavrilimumab in RA patients. The sustained effectiveness of mavrilimumab in RA may result from both direct impacts on myeloid cells and indirect impacts on T cell activation after GM-CSFR blockade.