Considering that filgotinib inhibits IFN-γ signaling pathway to a lesser extent compared with other JAK inhibitors including upadacitinib, it is suggested that filgotinib may effectively inhibit joint erosion in RA patients with IFN-γ-abundant synovium and that it may be appropriate for RA patients with a high risk of viral infection. This evidence concerns the gene IFNG and viral infectious disease.