Psoriasis is a chronic autoimmune condition that affects the skin, typically causing red, scaly patches to develop. These patches may be itchy and painful.

Doctors can treat most cases of mild to moderate psoriasis with light therapy or topical medications, such as creams or ointments.

However, people with moderate to severe psoriasis often need other treatments. These individuals may benefit from taking a type of medication known as a biologic.

Interleukin-23 (IL-23) inhibitors are one of several types of biologics that can treat moderate to severe psoriasis.

In this article, we provide an overview of IL-23 inhibitors and explain how they work to treat this condition.

a pharmacist picking out IL-23 inhibitors for psoriasisShare on Pinterest
A doctor may prescribe IL-23 inhibitors for moderate to severe psoriasis.

Biologics are protein-based medications that target specific parts of the immune system.

IL-23 inhibitors target a type of cytokine called IL-23. Cytokines are a class of proteins that help transmit signals from one cell to another. IL-23 plays a role in a signaling pathway that triggers inflammation.

IL-23 inhibitors block the action of IL-23, which can help limit the inflammation that causes psoriasis symptoms.

Treatment with IL-23 inhibitors may help reduce the amount of skin that psoriasis affects. It may also relieve symptoms, such as itching, pain, and skin tightness.

The Food and Drug Administration (FDA) has approved three types of IL-23 inhibitors for the treatment of moderate to severe psoriasis in adults.

Guselkumab (Tremfya)

Tremfya is a type of self-injectable IL-23 inhibitor. People who take this medication can inject it under their skin with a prefilled syringe or auto-injector.

The standard dosage is one injection at the start of treatment, one injection in the fourth week of treatment, and one injection every 8 weeks afterward.

According to clinical trial results in the Journal of the American Academy of Dermatology, Tremfya is an effective treatment for moderate to severe psoriasis. After 16 weeks, 70% of people who took this medication had an improvement of at least 90% in the affected area and the severity of their condition.

Risankizumab-rzaa (Skyrizi)

Skyrizi is another type of self-injectable IL-23 inhibitor. People who take Skyrizi can administer it using a prefilled syringe.

The standard dosage is an injection of 150 milligrams at the start of treatment, at 4 weeks, and every 12 weeks thereafter.

According to a study featured in The New England Journal of Medicine, 77% of people with moderate to severe psoriasis, who took Skyrizi for 12 weeks, experienced improvements of 90% or more in their symptoms.

Tildrakizumab-asmn (Ilumya)

Ilumya is an IL-23 inhibitor that a doctor will need to inject.

They will inject the drug under the individual’s skin once at the start of treatment, once at 4 weeks, and once every 12 weeks from then on.

Research published in The Lancet found that after 12 weeks of treatment, 62–64% of people with moderate to severe psoriasis, who received Ilumya, showed improvements of at least 75%.

IL-23 inhibitors tend to cause few side effects, and severe adverse effects are very rare.

However, taking IL-23 inhibitors may increase the risk of infections, such as:

  • upper respiratory infections
  • certain fungal infections
  • a herpes simplex infection
  • infectious diarrhea

Other potential side effects include:

Injection-site reactions may cause symptoms, such as redness, swelling, pain, or itching.

In rare cases, people may experience serious allergic reactions after taking IL-23 inhibitors. Those taking Tremfya may experience increased liver enzyme levels.

More research is necessary to confirm whether IL-23 inhibitors are safe for women, who are pregnant or breastfeeding.

Researchers also need to evaluate the long-term safety of IL-23 inhibitors further. For example, scientists want to learn whether these medications affect the risk of cancers.

“Given that it suppresses the immune system, there is a theoretical concern for increased risk of malignancy — or cancer,” Dr. Saakshi Khattri, M.D., the director of the Center for Connective Tissue Diseases at Mount Sinai in New York, told Medical News Today.

“[But] in animal models, blocking IL-23 does not appear to cause cancer,” Dr. Khattri added.

Before prescribing an IL-23 inhibitor, the American Academy of Dermatology and the National Psoriasis Foundation advise doctors to:

  • evaluate the person’s metabolic health
  • check the individual’s complete blood count
  • test for latent tuberculosis, hepatitis B, and hepatitis C
  • treat any active infections

While people are taking IL-23 inhibitors, doctors should monitor them for side effects.

“Patients on these medications come for periodic check-ins with their dermatologists, where questions related to any side effects are asked or any new symptoms are discussed and addressed,” Dr. Khattri told MNT.

IL-23 inhibitors are not the only biologics that treat moderate to severe psoriasis.

The FDA has also approved the following biologics to treat this condition:

  • Tumor necrosis factor (TNF)-alpha inhibitors: adalimumab (Humira), certolizumab pegol (Cimzia), etanercept (Enbrel), and infliximab (Remicade)
  • IL-17 inhibitors: secukinumab (Cosentyx), ixekizumab (Taltz), and brodalumab (Siliq)
  • IL-12/IL-23 inhibitor: ustekinumab (Stelara)

Doctors may also prescribe one or more of the following treatments:

  • light therapy, also known as phototherapy
  • topical treatments, such as topical steroids, vitamin D or vitamin A products, or a medication called anthralin (Zithranol-RR)
  • traditional systemic treatments, such as acitretin (Soriatane), cyclosporine, or methotrexate
  • a phosphodiesterase 4 (PDE4) inhibitor called apremilast (Otezla)

If one treatment does not work, doctors may prescribe another treatment. They may also recommend changes to a treatment plan if the person experiences side effects that are hard to tolerate.

When deciding which treatment to try, doctors and individuals may take the following into account:

  • how well previous treatments worked
  • whether the person has a history of certain health conditions, such as psoriatic arthritis, inflammatory bowel disease, multiple sclerosis, certain types of cancer, or heart disease
  • the individual’s preferences for how to administer the treatment or how often they need to take it
  • the out-of-pocket costs of the treatment

“I think the decision is a complex one,” Dr. Bruce Brod, M.D., a clinical professor of dermatology at the University of Pennsylvania Perelman School of Medicine in Philadelphia, told MNT.

“I think it’s a decision that’s made on a case-by-case basis, depending on the patient’s comorbidities, the patient’s personal risk tolerance, the patient’s insurance, the patient’s exposure to other prior biologics, and other factors,” he said.

What drugs are IL-23 inhibitors?

IL-23 inhibitors include:

  • Guselkumab (Tremfya) is a self-injectable form of an IL-23 approved to treat plaque psoriasis and psoriatic arthritis.
  • Risankizumab-rzaa (Skyrizi) is a self-injectable IL-23 approved to treat plaque psoriasis, psoriatic arthritis, and Crohn’s disease.
  • Tildrakizumab-asmn (Ilumya) is an IL-23 administered by a doctor and approved to treat plaque psoriasis.

What is the difference between Skyrizi and Ilumya?

Skyrizi is the brand name for risankizumab-rzaa, a self-injectible IL-23 inhibitor approved to treat plaque psoriasis in adults, who are candidates for systemic therapy or phototherapy, as well as psoriatic arthritis and Crohn’s disease.
Ilumya is the brand name for tildrakizumab-asmn, which a doctor must administer for the treatment of plaque psoriasis in adults, who are candidates for systemic therapy or phototherapy.

Is Cosentyx an IL-23 inhibitor?

Cosentyx is not an IL-23 inhibitor.

Cosentyx is an IL-17 inhibitor approved to treat plaque psoriasis, psoriatic arthritis, ankylosing spondylitis, non-radiographic axial spondyloarthritis, and enthesitis-related arthritis.

What is the difference between IL-17 and IL-23 inhibitors?

IL-17 and IL-23 inhibitors are both types of cytokines that can contribute to the development of psoriasis. However, the production of IL-17 depends on the action of IL-23 in the body.

Interleukin-23 inhibitors are among the many medications that doctors can use to treat moderate to severe psoriasis.

Most people who take IL-23 inhibitors experience few side effects. However, these medications may sometimes increase a person’s risk of infection. In some people, they can rarely cause a serious allergic reaction.

To learn more about the potential benefits and risks of different treatments for psoriasis, a person can speak with a doctor.