An interleukin (IL-23) inhibitor biologic
Guselkumab
An injected biologic that blocks the IL-23 immune signal, used for psoriasis and psoriatic arthritis.
What is Guselkumab?
Guselkumab is a biologic medicine that calms an overactive immune system by blocking interleukin-23 (IL-23), a messenger protein that drives inflammation. It is used for moderate to severe plaque psoriasis and psoriatic arthritis. It is given by injection under the skin, which many people learn to do themselves, with doses spaced weeks apart once established. Because it dampens part of the immune system, infection is the main caution, so you are usually screened for tuberculosis and hepatitis first and should avoid live vaccines during treatment.
Education and reference only. This is a plain-language guide to Guselkumab — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Guselkumab is a biologic medicine, made from living cells, that targets a specific immune signal called interleukin-23. IL-23 is one of the key messengers that drives the inflammation behind psoriasis. Guselkumab is used for moderate to severe plaque psoriasis and for psoriatic arthritis, usually when other treatments have not controlled things well enough. It is given by injection under the skin, and many people are trained to give it themselves at home using a pre-filled pen.
How it works
In psoriasis, the immune system over-produces signals that fuel inflammation in the skin and joints. Guselkumab attaches to interleukin-23, an early signal that drives this process, so the immune system stops being pushed to produce the thickened, scaly skin and joint swelling. Because it blocks one specific upstream signal rather than suppressing the whole immune system, it is a focused treatment, although it still leaves you somewhat more prone to infection.
Company & origin
Originated / developed by: Janssen.
A biologic medicine developed to treat moderate to severe plaque psoriasis and psoriatic arthritis by blocking the immune signal IL-23.
Practical use
How to take Guselkumab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given by injection under the skin, often with a pre-filled pen that many people learn to use themselves at home.
- Before starting, expect screening for tuberculosis and hepatitis so a hidden infection does not flare during treatment.
- Avoid live vaccines while being treated, and aim to be up to date with recommended non-live vaccinations beforehand.
- Once treatment is established, injections are usually spaced weeks apart, so keep track of your schedule.
- Tell your team promptly about any fever, persistent cough or infection that will not settle, and keep your review appointments.
Weighing it up
Advantages & disadvantages of Guselkumab
Advantages
- Often very effective at clearing moderate to severe plaque psoriasis and easing psoriatic arthritis.
- Targets one specific upstream immune signal, so it is more focused than older, broad immunosuppressants.
- Generally well tolerated, can be self-injected at home after training, with doses spaced weeks apart.
Disadvantages
- It dampens part of the immune system, so it can make infections more likely and may let a hidden tuberculosis or hepatitis infection flare.
- Live vaccines must be avoided during treatment.
- It is a biologic given by injection and needs screening before starting and ongoing monitoring.
Practical use
Good to know
The main thing to understand is that guselkumab works by quietening part of the immune system, so infection is the key caution, even though it is more focused than older broad immunosuppressants. Before you start, you are usually screened for tuberculosis and hepatitis so a hidden infection does not flare, and you should avoid live vaccines while being treated. It helps to be up to date with recommended non-live vaccinations beforehand. Tell your team promptly about any fever, persistent cough or infection that will not settle. IL-23 blockers like this are generally well tolerated, and after training most people give the injections themselves at home, with doses spaced weeks apart once established.
Who should not take it / use with caution
- People with a serious active infection should not start it until the infection is treated.
- It is used only after assessment in those with untreated tuberculosis or active hepatitis.
- Live vaccines should be avoided during treatment, so this needs planning around any immunisations.
Monitoring
- Screening for tuberculosis and hepatitis before starting, and watching for infection throughout treatment.
- Reviewing how well the skin and joints are responding so treatment can be adjusted.
- Checking vaccination status and planning any immunisations around the treatment.
Side effects
- More frequent infections, such as colds and chest or sinus infections, are the most important effect to watch for.
- Headache, and redness or soreness where the injection is given, which are usually mild.
- Rarely, more serious infections or allergic reactions, which need urgent medical attention.
Key interactions
- Combining it with other medicines that suppress the immune system adds to the infection risk and is done only with specialist advice.
- Live vaccines should not be given during treatment.
- Tell your team about all your medicines and any long-term conditions, as some affect how it is used.
Available as: Injection under the skin, often with a pre-filled pen for self-injection after training.
Answers
Guselkumab: frequently asked questions
How does guselkumab work?
It blocks interleukin-23 (IL-23), an early immune signal that drives the inflammation behind psoriasis, which calms the overactivity causing the skin and joint symptoms.
Do I need tests before starting?
Yes, you are usually screened for tuberculosis and hepatitis first, because calming part of the immune system can let a hidden infection flare.
Can I have my usual vaccinations?
You should avoid live vaccines during treatment; it is best to be up to date with recommended non-live vaccinations before you start, and your team can advise.
Does it make infections more likely?
It can, because it dampens part of the immune system, so tell your team promptly about any fever, persistent cough or infection that will not settle.
How often will I need the injection?
Once treatment is established, injections are usually spaced weeks apart, which many people find convenient, and most can self-inject at home after training.
The wider class
About Interleukin (IL-23) inhibitor biologic
Guselkumab belongs to the interleukin (il-23) inhibitor biologic class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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