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.
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) have approved three types of IL-23 inhibitor for the treatment of moderate-to-severe psoriasis in adults.
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 area and severity of their condition.
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 two injections at the start of treatment, two injections at week four of treatment, and two injections every 12 weeks from then on.
According to a study that 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.
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 week four of treatment, and once every 12 weeks from then on.
Research that The Lancet published 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
- herpes simplex infection
- infectious diarrhea
Other potential side effects include:
- joint pain
- injection-site reactions
Injection-site reactions may cause symptoms such as redness, swelling, pain, and itching.
In rare cases, people may experience serious allergic reactions after taking IL-23 inhibitors. Taking Tremfya has also increased liver enzyme levels in some people.
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 cancer.
“Given that it suppresses the immune system, there is a theoretical concern for increased risk of malignancy — or cancer,” Dr. Saakshi Khattri, M.D., an assistant professor of dermatology and rheumatology at Icahn School of Medicine at Mount Sinai in New York, NY, 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 have 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, which is 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 have 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 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.
IL-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 the risk of infection. In rare cases, they can cause a serious allergic reaction.
To learn more about the potential benefits and risks of different treatments for psoriasis, a person can speak to their doctor.