An orally bioavailable inhibitor of the tyrosine kinase Janus kinase 1 (JAK1), with potential anti-inflammatory and immunomodulating activities. Upon oral administration, filgotinib specifically targets, binds to, and inhibits the phosphorylation of JAK1, which interferes with JAK/STAT (signal transducer and activator of transcription)-dependent signaling. As JAK1 mediates signaling of many pro-inflammatory cytokines, JAK1 inhibition prevents cytokine signaling and activity in many inflammatory and immune-mediated processes and leads to a decrease in inflammation and activation of certain immune cells. JAK1 plays a key role in the signaling and activity of many cytokines and growth factors and is often dysregulated in a variety of autoimmune and inflammatory diseases, as well as some malignancies.