• Ankylosing spondylitis (AS) causes inflammation in the spine.
  • A new kind of treatment, JAK inhibitors, has been approved to treat AS.
  • JAK inhibitors alter your body’s immune response and can reduce the symptoms of AS.

Ankylosing spondylitis (AS) is a type of inflammatory arthritis that primarily affects your spine. In severe cases, it can limit your mobility, and parts of your spine may fuse together.

Treatments for ankylosing spondylitis have traditionally involved the use of nonsteroidal anti-inflammatory drugs (NSAIDs) and biologics. A newer form of treatment, known as JAK inhibitors, is approved for use in treating AS, following successful clinical trials.

Studies have shown that JAK inhibitors are both safe and effective for treating ankylosing spondylitis. This article covers everything you need to know about this newer class of medication.

Janus kinase inhibitors (JAK inhibitors) are a type of small molecule, disease-modifying medication. They’re not a form of biologic drug.

They typically come in pill form, which means that you can take them at home without having to go to a doctor’s office for an infusion or injecting yourself at home.

JAK inhibitors work by blocking your immune system’s ability to make specific enzymes that are responsible for your AS symptoms. Your doctor may prescribe them when your AS is active or not in remission.

Your doctor may decide to prescribe JAK inhibitors with or without a disease-modifying agent, like methotrexate. If your doctor believes that they’d work well for you, they may prescribe JAK inhibitors before prescribing biologics.

JAK inhibitors have had quite a bit of success in clinical studies and broader studies as well. People who take them often notice improved symptoms within 2 weeks, but it can take 6 or more months before a person notices full effects.

In a 2020 study, researchers noted that JAK inhibitors provide:

  • results comparable to biologics
  • similar results to tumor necrosis factor (TNF) inhibitors in terms of disease response

In addition, the researchers found JAK inhibitors have a similar safety profile to TNF inhibitors.

Another study from 2021 looked at the safety and effectiveness of upadacitinib, a type of JAK inhibitor. They found that users of the medication showed consistent and sustained results over the course of 1 year of treatment. They also noted that people who started after 14 weeks of placebo showed similar effectiveness to the other group.

A study from 2022 found similar results. They noted that people who experienced inadequate results from two or more NSAIDs had good results when they switched to JAK inhibitors. In addition, they noted that the participants had a limited risk of experiencing serious adverse effects from the switch in medication.

JAK inhibitors are generally safe with minimal risk for major side effects.

Some minor side effects you may experience when taking JAK inhibitors include:

  • diarrhea
  • nausea
  • headaches
  • indigestion
  • increased cholesterol levels
  • upper respiratory tract infection

In rare cases, you may experience more serious side effects, such as:

  • decreased kidney function
  • infection
  • abnormal liver function tests
  • increased risk of bowel perforation
  • abnormal blood counts

You can reduce your risk of mild or severe side effects by:

  • taking your medication as prescribed
  • monitoring your condition with your doctor
  • getting regular blood tests

The blood and other tests your doctor may use include:

  • liver functions test
  • lymphocyte count (needed before you start to establish your base levels and then monitor your response)
  • hemoglobin (requiring a baseline measure and then regular monitoring)
  • neutrophil/platelet counts (tested once before starting and then monitored for changes)
  • viral hepatitis (often checked before starting the medication)
  • lipids level

Though JAK inhibitors may work well with minimal side effects, not everyone is a good candidate for JAK inhibitors. If one of the following factors applies to you, you should talk with your doctor before starting them:

  • liver disease
  • certain kidney diseases
  • pregnancy
  • history of active tuberculosis
  • blood disorders
  • previous reaction to other JAK inhibitors
  • active infection
  • cancer

You should also let your doctor know if you have other underlying health conditions. Some medications used to treat them may interact with JAK inhibitors. The conditions include:

  • diabetes
  • stroke
  • heart disease
  • chronic respiratory infections

JAK inhibitors aren’t always the first line of treatment. Instead, a doctor may prescribe them to you if:

JAK inhibitors come in pill or tablet form. The first approved JAK inhibitor for use with ankylosing spondylitis received Food and Drug Administration (FDA) approval in the latter half of 2021 in the form of tofacitinib (Xeljanz). Upadacitinib (Rinvoq) has also been approved.

Additional JAK inhibitors are currently under investigation and clinical trials for effectiveness and safety.

JAK inhibitors present a newer treatment option for people living with active ankylosing spondylitis. They are a type of disease-modifying drug that lowers your immune system’s response, which helps to reduce the symptoms you experience as a result of ankylosing spondylitis.

The first to receive approval was tofacitinib, but others should join it shortly.

Studies have shown that several different JAK inhibitors provide effective therapy with minimal risks and side effects to users.