STAT4 and rheumatoid arthritis: Signal transducers and activators of transcription (STATs) are transcription factors that convey signals from the cell surface to the nucleus.[1] The family member STAT4 plays key roles in autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, and type 1 diabetes.[2] Upon interleukin‐12 stimulation, STAT4 is phosphorylated at tyrosine 693,[3] leading to differentiation of T‐helper cells of the Th1 subgroup.[4] Small‐molecule inhibitors of the STAT4 Src homology 2 (SH2) domain have the potential to serve as new therapeutic modalities for these unmet medical challenges.