JAK inhibitors

Janus kinase (JAK) inhibitors are a class of medication that modulate the activity of the Janus kinase family of enzymes. These enzymes play a critical role in the signalling pathways of various cytokines involved in immune function and inflammation. JAK inhibitor medications aim to block the activity of the JAK enzymes, interfering with the signalling pathways and decreasing inflammation.

Baricitinib (brand name Olumiant) and ritlecitinib (brand name LITFULO) are the only licensed treatments for severe alopecia areata (more than 50% hair loss). Baricitinib is only licensed for those aged over 18 whilst ritlecitinib is licensed for patients aged 12 and over.

Currently baricitinib has not been recommended for routine NHS commissioning by NICE (England, Wales and NI) or SMC (Scotland). This means baricitinib is only available to patients with severe alopecia areata via a private prescription.

Ritlecitinib was recommended by NICE and SMC in Spring 2024 meaning that patients with severe alopecia areata should be able to access this treatment via NHS pathways. We have a separate FAQs webpage about ritlecitinib designed to help people understand more about the NICE recommendation and NHS pathways.

Before starting a JAK inhibitor, a number of baseline tests are usually required. These tests are generally undertaken for patients before starting any medications that act on the immune system. These tests may include blood samples to check liver & kidney function, blood count, blood fats, for evidence of serious viral infections (hepatitis & HIV) and tuberculosis (TB). Evidence that you are immune to the chickenpox virus is also checked. A chest X-ray may also be carried out. As there is an increased risk of developing shingles while taking JAK inhibitors, those aged over 50 may be recommended for shingles vaccination. You are likely to be advised to have a vaccination for pneumococcal infection, annual flu vaccines and covid vaccines. 

Women who can become pregnant must be on an effective form of contraception if sexually active, as JAK inhibitors should not be taken during pregnancy or breast-feeding.

Not all patients will be suitable for JAK inhibitors due to other health issues.

Not all patients will develop an adequate response to JAK inhibitor treatment and the treatment may be stopped.

JAK inhibitors are a long-term treatment, and patients need regular blood tests to monitor for side effects.

JAK inhibitors might be prescribed to patients with the following alopecia types:

severe alopecia areata (hair loss of greater than 50%, including totalis and universalis).

Clinical trials are currently ongoing to explore new JAK inhibitor medications for alopecia areata. There are also clinical trials exploring JAK inhibitors for the treatment of some scarring alopecias such as frontal fibrosing alopecia and lichen planopilaris.