TYK2 and psoriasis: Consequently, the clinical investigation of JAK1, 2, and 3 inhibitors for psoriasis therapy has been largely discontinued because of a low therapeutic index and increased safety concerns, including increased risk of infection, herpes zoster, neutropenia, and abnormal laboratory results; while TYK2 inhibitors, as a class of more selective JAK inhibitors, may become promising candidate for psoriasis treatment (20, 45, 47).