JAK inhibitors for alopecia areata: a new class of treatment

For many years, people with severe alopecia areata had few reliable treatment options. That has changed with a group of medicines called Janus kinase (JAK) inhibitors. One expert review described them as having "ushered in a new era" for the condition ¹. Here is what they are, what the trials found, and what to consider.

A quick reminder: what is alopecia areata?

Alopecia areata is an autoimmune condition. The immune system attacks hair follicles, causing round or oval patches of hair loss on the scalp, and sometimes loss of eyebrows, eyelashes or body hair ². The follicles are usually not destroyed, which is why hair can grow back. Some people have a few small patches that settle on their own, while others lose most or all of their scalp hair. See can alopecia areata go away on its own?.

How JAK inhibitors work

Inside immune cells, signals from inflammatory messengers (cytokines) pass through enzymes called Janus kinases. In alopecia areata, some of these signals drive the immune attack on the follicle. JAK inhibitors block these enzymes and interrupt the signalling ³. With the attack reduced, follicles can return to normal growth.

What the big trials found

Baricitinib. Two phase 3 trials, BRAVE-AA1 and BRAVE-AA2, enrolled 654 and 546 adults with severe alopecia areata (at least 50% scalp hair loss) ³. The main goal was hair loss covering 20% or less of the scalp at week 36. This was reached by:

• about 39% and 36% of people taking 4 mg daily
• about 23% and 19% of people taking 2 mg daily
• about 6% and 3% of people taking placebo

Ritlecitinib. A phase 2b-3 trial at 118 sites in 18 countries included 718 people aged 12 and older with at least 50% scalp hair loss ⁴. At week 24, 23% of people taking 50 mg reached 20% or less scalp hair loss, compared with 2% on placebo. The authors described it as effective and well tolerated in patients who are candidates for systemic treatment.

Cochrane review. A 2023 Cochrane review of 63 trials of alopecia areata treatments concluded that baricitinib increases hair growth in both the short and long term compared with placebo, based on high-certainty evidence ⁵. The effect of most other treatments was very uncertain.

What this means in practice

• JAK inhibitors are tablets taken daily under specialist care.
• They are mainly used for moderate to severe alopecia areata, not for a single small patch.
• Not everyone responds. In the trials, a meaningful share of people did not reach the main target.
• Hair growth takes months. Trials measured results at 24 to 36 weeks.
• Hair loss may come back if treatment is stopped, so the decision is often about longer-term use.
• JAK inhibitors do not treat pattern hair loss.

Side effects and monitoring

In the baricitinib trials, acne, raised creatine kinase (a muscle enzyme) and raised cholesterol levels were more common than with placebo ³. In the ritlecitinib trial, the rate of side effects was similar between groups and there were no deaths ⁴.

Because JAK inhibitors affect the immune system, doctors consider risks such as infections and review each person's medical history before starting. Blood tests are usually needed before and during treatment. Your doctor will explain the specific warnings for the medicine prescribed. The choice of drug depends on age, other health conditions and patient selection factors ¹.

Tell your doctor if you:

• have had serious or repeated infections, tuberculosis or hepatitis
• have had blood clots, heart disease or cancer
• smoke
• are pregnant, planning pregnancy or breastfeeding
• take other medicines that affect the immune system

Other treatments for alopecia areata

JAK inhibitors are one option among several. Others include steroid injections into patches, steroid creams, contact immunotherapy and other immune-modulating medicines ⁶. For small patches, a doctor may suggest watching and waiting or local treatment. The right choice depends on how much hair is affected, how long it has been present, age and personal preference.

Getting assessed

If you have patchy hair loss, see a doctor or dermatologist for a diagnosis. Other conditions, such as fungal infection or hair pulling, can look similar. A specialist can examine your scalp, sometimes with trichoscopy, and discuss whether systemic treatment is appropriate. See when to see a dermatologist and scalp analysis and trichoscopy.

Coping matters too

Alopecia areata can affect confidence and mood ⁷. Wigs, hairpieces and support groups can help, whatever treatment you choose.

The bottom line

JAK inhibitors are the first treatments with strong trial evidence for severe alopecia areata. They help many, but not all, people, take months to work and require medical supervision. Talk to a dermatologist about whether they suit your situation.

Frequently asked questions

What are JAK inhibitors?

Tablets that block Janus kinase enzymes involved in the immune signals behind alopecia areata ³.

How well do JAK inhibitors work for alopecia areata?

In the baricitinib trials, about 36-39% of people on 4 mg had 20% or less scalp hair loss at 36 weeks, compared with 3-6% on placebo ³.

What are the side effects?

Trials reported acne, raised creatine kinase and raised cholesterol among others. Doctors also assess infection and other risks and arrange blood tests ³.

Do JAK inhibitors help pattern baldness?

No. They are used for alopecia areata, an autoimmune condition, not for pattern hair loss.

Educational content. Not medical advice.