Janus kinase (JAK) inhibitors are oral medications that interfere with an overactive immune pathway called JAK-STAT, which normally helps regulate inflammation throughout the body. In alopecia areata, this pathway becomes dysregulated, causing your immune system to mistakenly attack hair follicles. By blocking JAK signaling, these drugs break that feedback loop, allowing hair to regrow.
“The JAK-STAT pathway acts like an on-switch for the immune system. When we block it, we prevent the immune system from recruiting more inflammatory cells to attack the hair,” says Mostaghimi.
Right now, there are three FDA-approved JAK inhibitors to treat moderate-to-severe alopecia areata:
Baricitinib (Olumiant)
Baricitinib had already been approved for rheumatoid arthritis and atopic dermatitis, which means doctors had long-term safety data even before its alopecia indication.
“It’s a well-studied medication — if a patient or clinician is concerned about long-term risks, baricitinib has the most-established safety record of the three,” says Mostaghimi.
Ritlecitinib (Litfulo)
This medication targets proteins called JAK3 and TEC kinases, a slightly different way of working that may influence the side effects it can cause. “It may have less impact on cholesterol than some other JAK inhibitors,” says Mostaghimi.
Ritlecitinib is the only approved treatment for adolescents right now, he adds.
Deuruxolitinib (Leqselvi)
Deuruxolitinib is metabolized differently from the other approved JAK inhibitors, and you need to have a genetic test before starting treatment to ensure safe metabolism, says Mostaghimi.
Deuruxolitinib and baricitinib target the same pathways, but some people respond better to one than the other, he says. It’s a reminder that “switching between drugs in the same class can still work,” he adds.