Abrocitinib, a potent JAK1 inhibitor (IC50 = 0.029 µM), selectively targets JAK1 over JAK2, JAK3, and TYK2 (IC50s = 0.803, >10, and 1.253 µM respectively), and a panel of 40 kinases at 1 µM. It inhibits IFN-α-, IL-21-, or IL-27-induced STAT3 phosphorylation (IC50s = 0.189, 0.511, and 0.271 µM respectively) and IFN-γ-induced STAT1 phosphorylation (IC50 = 0.163 µM) in isolated human whole blood. In a rat model of adjuvant-induced arthritis, it reduces paw edema at doses of 1, 5, and 15 mg/kg. Abrocitinib formulations have been employed in atopic dermatitis treatment.