Treating Psoriatic Arthritis With JAK Inhibitors

What's Available and What's on the Horizon

In This Article

Woman taking a pill - JAK inhibitors for psoriatic arthritis

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If you have psoriatic arthritis (PsA), your doctor may suggest Janus kinase inhibitors, also known as JAK inhibitors, to ease joint pain and swelling, and skin symptoms associated with PsA. JAK inhibitors are a type of medication that inhibits the activity of one or more of the Janus kinase family of enzymes, such as JAK1, JAK2, JAK 3, and TYK2. By inhibiting these processes, JAK inhibitors interact with the signal of JAK pathways.

JAK inhibitors are often used to treat various autoimmune diseases, diseases where the immune system malfunctions. JAK inhibitors can help to taper down your overactive immune system to prevent joint damage and disease progression. 

How JAK Inhibitors Work

In people with PsA, the body makes too many proteins called cytokines, which play a role in causing inflammation. When cytokines attach to immune system cells, they send a message to the cells to produce more cytokines, which means more inflammation. JAK inhibitors block this process, calming down the immune system and easing PsA inflammation, pain, and other PsA symptoms.

Older biologics, such as Humira (adalimumab), may not help some people in managing PsA symptoms. For these people, a JAK inhibitor may help to manage symptoms and improve quality of life.

A major advantage of JAK inhibitors is that they are available in pill form, whereas biologics must be given by injection or intravenous (IV) infusion.

PsA Treatment

As of 2019 in the United States, there are currently five available JAK inhibitor drugs that have been approved for use by the U.S. Food and Drug Administration (FDA). Of those five medications, Xeljanz (tofacitinib) is the only one approved by the FDA for treating PsA.

Xeljanz (Tofacitinib)

Xeljanz (tofacitinib) was approved for the treatment of PsA in 2012 by the FDA. It has been proven to work alone or with methotrexate, an immunosuppressive drug.

Studies have shown that 5 milligrams twice daily of Xaljanz can offer significant improvement of skin symptoms and reduction of inflammation in the fingers, toes, and other parts of the body where tendons or ligaments insert into bone.

One 2017 PsA study reported in the New England Journal of Medicine finds five milligrams of Xaljanz twice daily was superior to a placebo in achieving a 20 percent improvement response in just three months. Improvement was noted as a 3 out of 5 criteria, including self-assessment, doctor assessment, pain scale, a functionality questionnaire, and blood work.

Another study from 2016 examined the effect of Xaljanz on the pro-inflammatory mechanisms of PsA. The results showed Xaljanz was effective in inhibiting inflammatory markers and reducing pain and other symptoms associated with PsA.

Up-and-Coming Treatments

There are currently no other JAK inhibitors that have been approved by the FDA for the treatment of psoriatic arthritis. As of 2019, Olumiant (baricitinib) is in its final study phases for testing in people with PsA. It was previously approved for the treatment of rheumatoid arthritis, an autoimmune disease known for causing systemic (all over) inflammation of the joints and organs.

Previous studies have found Olumiant to be promising for PsA, showing “good efficacy and an acceptable safety profile.”

Risks and Side Effects

Because JAK inhibitors suppress the actions of the immune system, taking them puts you at risk for different kinds of infections.

In clinical trials of tofacitinib and Olumiant, some study participants developed tuberculosis (TB), a serious lung infection. JAK inhibitors will also put you at risk common viral diseases, including shingles.

These drugs lose their effect once you stop taking them. This means your immune system will get back its full ability to fight infection once the drug is fully out of your system, which is usually only a matter of days.

The most serious side effects of JAK inhibitors include:

  • Liver damage
  • Neutropenia: A condition that causes an abnormally low count of a type of white blood cells
  • Lymphopenia: A condition that causes abnormally low level of lymphocytes (a type of white blood cell) in the blood

Research also shows that JAK inhibitors may interact with DMARDs (disease modifying anti-rheumatic drugs) and other immunosuppressant drugs (drugs that inhibit or prevent activity of the immune system). These interactions include:

  • Decreases in hemoglobin (a protein molecule in red blood cell)
  • Decreases in neutrophil (a type of white blood cell) counts
  • Increase of LDL (bad cholesterol)
  • High creatinine levels (a sign of impaired kidney function or kidney disease)

Common side effects with JAK inhibitor use include:

A Word From Verywell                               

Drugs in the pipeline for treating psoriatic arthritis are being developed and tested, including JAK inhibitors. These drugs must be tested in three phases of clinical trials before the FDA can approve them.

There are a number of JAK inhibitors being testing currently for the treatment of PsA, including Filgotinib (GLPG0634), Olumiant, and Upadacitinib (ABT-494), and more are likely on the horizon.

Newer JAK inhibitor options may be safer than the current ones available, with less serious side effects, which means more options for treating PsA successfully and improving quality of life for the many affected by this condition.

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