Alopecia areata, commonly known as “spot baldness” or “ghost hair loss,” is an autoimmune disease in which individuals suddenly discover patchy hair loss on the scalp. In simple terms, the body’s immune system mistakenly identifies its own hair follicles as “enemies” and attacks them, causing the follicles to enter a resting phase and leading to hair shedding.
In the past, treatment options for alopecia areata were limited: mild cases might resolve spontaneously, while moderate to severe patients relied on glucocorticoids, topical immunotherapy, and other approaches, but the efficacy varied among individuals, and side effects were troubling. It was not until recent years that a class of oral medications called “JAK inhibitors”—originally developed for autoimmune diseases such as rheumatoid arthritis—showed promising results in the treatment of alopecia areata.
JAK (Janus kinase) is a “switch” for an important intracellular signaling pathway. When immune cells receive an attack command, they release “inflammatory” signals through the JAK-STAT pathway. JAK inhibitors act like a small lock, blocking this switch and interrupting the transmission of inflammatory signals, thereby giving hair follicles a “breathing space” to regrow hair.
Currently, two JAK inhibitors have been approved by the U.S. Food and Drug Administration (FDA) for the treatment of severe alopecia areata based on rigorous clinical trials: baricitinib and upadacitinib. These are oral JAK inhibitors taken once daily, prescribed after evaluation by a specialist.
The approval of baricitinib was based on two Phase III clinical trials, BRAVE-AA1 and BRAVE-AA2. The studies included patients with moderate to severe alopecia areata involving more than 50% scalp hair loss. Results showed that after 36 weeks of treatment with baricitinib (4 mg/day), approximately one-third to one-quarter of patients achieved 80% or more scalp hair coverage (i.e., SALT score ≤20). In contrast, this proportion was only a single-digit percentage in the placebo group.
Upadacitinib demonstrated similar efficacy in another pair of Phase III trials, Measure Up 1 and Measure Up 2. Also targeting patients with severe alopecia areata, after 24 weeks of treatment with upadacitinib (30 mg/day), more than 40% of patients achieved 80% or greater scalp hair coverage. These data have been published in top-tier medical journals, including the *New England Journal of Medicine*.
It must be emphasized that these drugs are not “miracle cures.” A considerable proportion of patients in clinical trials still showed poor response, and hair loss may recur after discontinuation. Due to the relatively short study duration, long-term efficacy and safety are still under ongoing surveillance.
JAK inhibitors also have clear side effects. The most common include upper respiratory tract infections (e.g., common cold), headache, and acne. Of greater concern is that they may increase the risk of herpes zoster (commonly known as “shingles”) reactivation, as well as lead to elevated blood lipids and thrombosis. Therefore, screening for infections such as tuberculosis and hepatitis B is required before treatment, and regular monitoring of blood counts, liver and kidney function, and blood lipids is necessary during treatment.
Moreover, not all patients with alopecia areata are suitable candidates for JAK inhibitors. Currently, the FDA approval is for the treatment of “severe” alopecia areata (i.e., ≥50% hair loss) and is limited to adult patients. Children, pregnant women, nursing mothers, and individuals with a history of serious infections or thrombosis are generally contraindicated or should use with caution.
In China, both baricitinib and upadacitinib have been approved for the treatment of severe alopecia areata, but they are prescription drugs that must be used after a comprehensive evaluation by a dermatologist. Patients should never purchase these medications on their own or through online cross-border sourcing, as dose adjustments and adverse reaction monitoring require professional guidance.
Other JAK inhibitors, such as ritlecitinib and deuruxolitinib, are still under investigation or have been approved in some countries, but the supporting evidence is not as robust as that for baricitinib and upadacitinib. In the future, as more clinical trials are completed, we can expect more precise treatment options with fewer side effects.
In summary, the emergence of JAK inhibitors provides a new, immune-based therapeutic option for patients with severe alopecia areata. They are not a cure, but they are among the most evidence-based medications currently available. Scientific progress has deepened our understanding of how “runaway immunity” leads to hair loss and has identified actionable “targets” for intervention.
(For reference only; does not constitute medical advice.)