GPLG0634

Filgotinib (GLPG0634) is a selective JAK1 inhibitor with IC50 of 10 nM, 28 nM, 810 nM, and 116 nM for JAK1, JAK2, JAK3, and TYK2, respectively. Phase 2.
Rheumatoid arthritis (RA) is a chronic, autoimmune, systemic, and inflammatory disease that causes synovial joint symptoms and can limit range of motion in severe cases. The disease is associated with extra-articular manifestations, progressive disability, and comorbidities including cardiovascular disease and mental disorders. 50-70% of patients with RA are unable to achieve sustained clinical remission despite the availability of several treatments including disease-modifying anti-rheumatic drugs (DMARDS) like [methotrexate], interleukin-6 (IL-6) blockers, and tumor necrosis factor (TNF) inhibitors. New therapeutic developments target other inflammatory pathways implicated in RA including the Janus kinase (JAK) signaling pathway as seen with filgotinib. There are four JAK subtypes which include JAK1, JAK2, JAK3, and tyrosine kinase 2. Non-selective JAK inhibitors like [tofacitinib] target JAK1 and JAK3 subtypes with minimal activity at JAK2. In contrast, the newly approved filgotinib is a highly selective JAK1 inhibitor. JAK2 and JAK3 play important roles in both immune and hematologic functions; therefore, selectivity for JAK1 aims to improve the safety profile of filgotinib while maintaining clinical efficacy. Filgotinib is currently reserved for patients who cannot tolerate DMARDs, or who have been unable to achieve remission in response to one or more DMARDs.|Filgotinib is 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.