Use of Jak Inhibitors in the Treatment of Alopecia Areata

Alopecia areata (AA) is a chronic, immune-mediated autoimmune disease that affects hair follicles, nails, and occasionally the retinal pigment epithelium. The disease most commonly involves hair follicles in the anagen phase and leads to complete or partial hair loss without permanent damage to the hair follicles and without scar formation. The pathogenesis of alopecia areata is complex and includes genetic factors, immune factors, environmental influences, oxidative stress, allergy, microbiome, as well as other factors that lead to autoimmune disorders in the normal hair cycle. Current alopecia areata therapy includes topical or systemic corticosteroids, minoxidil, methotrexate, and azathioprine, which show limited efficacy, especially in more severe forms of alopecia. Advances in understanding the pathogenesis of alopecia areata have led to the development of new treatments, such as Janus kinase inhibitors. Janus kinase inhibitors are small molecules capable of blocking one or more tyrosine kinases withing the JAK-STAT (Janus kinase/signal transducer and activator of transcription pathway) signaling pathway, including JAK1, JAK2, JAK3 and tyrosine kinase 2. This way, they block various cytokine and inflammatory signaling pathways and induce immunosuppression. Current data indicates that oral Janus kinase inhibitors (baricitinib, ritlecitinib, deuruxolitinib, brepocitinib) constitute a promising new drug class. Janus kinase inhibitors can induce substantial hair regrowth with mild-to-moderate adverse effects and are therefore increasingly favored over corticosteroids.