MK-2420

MK-2420 is an investigational small-molecule inhibitor of Bruton's tyrosine kinase (BTK) that was developed by Merck Sharp & Dohme (MSD) for the treatment of autoimmune diseases, primarily rheumatoid arthritis. BTK is a non-receptor tyrosine kinase that plays a pivotal role in the B-cell receptor (BCR) signaling pathway, which is essential for B-cell activation, proliferation, and the production of autoantibodies. Additionally, BTK is involved in the activation of myeloid cells, such as macrophages and mast cells, which contribute to the inflammatory milieu in rheumatoid arthritis. By reversibly inhibiting BTK, MK-2420 aimed to modulate these immune responses to reduce joint inflammation and damage. Clinical development of MK-2420 reached Phase 2 (notably in trial NCT02531932); however, Merck discontinued the program in 2017, likely due to strategic portfolio prioritization or insufficient competitive efficacy compared to emerging standards of care.