Biologics can provide an effective, generally safe treatment for ankylosing spondylitis (AS). Doctors may prescribe them if a person does not respond to first-line therapies or their symptoms worsen.

Biologics are a type of medication made from living organisms. They typically include proteins designed to replicate the functions of naturally occurring ones that play a role in the immune system.

There is currently no cure for AS, but biologics can help a person better manage their symptoms.

Some people may refer to these drugs as biopharmaceuticals or biologic medical products. Although they are often expensive, they can help reduce symptom severity and prevent disease progression.

This article explains biologics in more detail, including how they work and who should potentially avoid them.

The immune system is a complex structure comprising cells, proteins, and organs that work together to help keep the body healthy.

When a person has AS, the immune system mistakenly attacks healthy cells, causing inflammation. The proteins interleukin (IL) and tumor necrosis factor (TNF) play a role in producing inflammation in the body.

Biologics block receptors for these two protein types, preventing the immune system’s inflammatory response.

This helps reduce AS symptoms, prevent damage to the joints, and lessen the likelihood of further complications associated with AS.

There are currently three main types of biologics that doctors use in AS management:

  • TNF inhibitors
  • IL-17 inhibitors
  • IL-12/23 inhibitors

TNF inhibitors

According to the Spondylitis Association of America, TNF inhibitors were the first type of biologics approved by the Food and Drug Administration (FDA) for treating AS.

TNF inhibitors have shown effectiveness in treating inflammation in several areas of the body, including the:

  • joints
  • gut
  • eyes

There are currently five different TNF inhibitors that a doctor may recommend:

  • infliximab (Remicade)
  • adalimumab (Humira)
  • etanercept (Enbrel)
  • certolizumab pegol (Cimzia)
  • golimumab (Simponi)

Although all TNF inhibitors target TNF — a cytokine responsible for signaling the immune system’s inflammatory response — they operate slightly differently.

If a person develops resistance to one type, their doctor can switch them to another option.

Some biologics now have one or several similar biosimilar products available, which a doctor may offer instead of the biologic. Biosimilars are medications that have a very similar structure and function to biologics.

IL-17 and IL-12/23 inhibitors

IL-17 and IL-12/23 inhibitors operate similarly to block cytokines, which prevents the immune system from producing an inflammatory response. IL-17 inhibitors block the IL-17 cytokine, and IL-12/23 inhibitors block both the IL-12 and IL-23 cytokines.

There are currently two types of IL-17 inhibitors: ixekizumab (Taltz) and secukinumab (Cosentyx).

However, the FDA has only approved one type of IL-12/23 inhibitor — ustekinumab (Stelara) — for treating AS.

Dr. Robert Koval, a board certified rheumatologist with Texas Orthopedics in Austin, TX, told Medical News Today that he recommends biologics when people do not respond well to initial treatment options or start developing new symptoms despite treatment.

Dr. Koval’s goal when using biologics is for the person to achieve “complete resolution of symptoms.”

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a first-line treatment for AS. Before trying biologics, treatment may also involve steps such as:

  • physical therapy
  • postural training
  • regular exercise

Healthcare professionals may recommend a person continue these nonpharmacological steps while taking biologics.

It is possible to administer biologics as an injection or intravenous infusion. The delivery method will depend on the specific medication that the doctor prescribes.

If the drug is available as an injection, a doctor can prescribe it for the person to self-administer at home. However, a person will need to visit the doctor’s office, infusion center, or hospital for an infusion.

According to a 2019 systematic review and meta-analysis, people generally tolerate biologics well. However, this line of treatment can sometimes cause unpleasant side effects.

The Arthritis Foundation notes that common side effects of biologics may include:

  • an increased risk of infection
  • a reaction at the injection site, which may involve site-specific symptoms such as:
    • swelling
    • itching
    • pain
  • a reaction to the infusion, which can produce symptoms such as:
    • headaches
    • nausea
    • general pain

A person should watch for new and changing symptoms that may indicate the development of an infection or another side effect. If they experience a side effect, they should inform the doctor.

Biologics can cause complications in some people, and certain medications may interact with them. As a result, biologics may only be suitable for some people.

Certain groups of people should avoid taking biologics or take extra care when doing so due to possible complications or adverse reactions. Some considerations or general guidelines include:

  • People who are pregnant or nursing should check with a doctor before using biologics. A doctor may prescribe certolizumab, as it does not cross the placenta.
  • Anyone using biologics should avoid immunizations that use live vaccines.
  • Individuals receiving cancer, diabetes, heart, or nervous system treatment should talk with a doctor before using biologics.
  • People with an active infection or who live where fungal infections are common should consult a doctor before using biologics.

The use of biologics also comes with an increased risk of developing or having a recurrence of infections, including hepatitis B or C, tuberculosis, and fungal infections.

In addition, some evidence suggests that TNF inhibitors can lead to an increased risk of a person developing non-melanoma skin cancer. However, research suggests biologics have an overall good safety record and that most people tolerate them well.

For example, a 2021 report analyzing 48 studies on the adverse effects of anti-IL-23 treatments did not identify any significant links between these medications and increased cancer risk.

A person can talk with a doctor if they are concerned they have a higher risk of complications. Likewise, a person using biologics to treat their AS should inform a doctor about any adverse reactions.

Biologics are an effective and often well-tolerated treatment option for people living with moderate to severe AS. Biologics target the protein receptors in the immune system to prevent the immune response that creates inflammation.

A doctor may prescribe biologics to treat AS when first-line treatments, such as physical therapy and NSAIDs, do not work or a person’s symptoms worsen.

Although biologics are generally safe, a person should let a doctor know if they experience adverse reactions. Anyone concerned about their risk factors for developing complications while taking biologics can also discuss these points with a doctor.