An antibody injection for ulcerative colitis and Crohn's
Mirikizumab
A specialist antibody medicine used to treat inflammatory bowel disease such as ulcerative colitis and Crohn's disease.
What is Mirikizumab?
Mirikizumab is a specialist biologic medicine used to treat inflammatory bowel disease, including ulcerative colitis and Crohn's disease, in people whose condition has not responded well enough to other treatments. It is an antibody that blocks a chemical messenger (interleukin-23) that drives the inflammation. It is given by a drip into a vein to start and then by injection under the skin. Because it dampens part of the immune system, it can raise the risk of infections, so people are screened for infections such as tuberculosis first and live vaccines are avoided. Liver blood tests are also checked.
Education and reference only. This is a plain-language guide to Mirikizumab — 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
Mirikizumab is a biologic medicine — an antibody — used to treat inflammatory bowel disease, particularly ulcerative colitis and Crohn's disease. It is used in people with moderate to severe disease that has not responded well enough to other treatments. It works by blocking interleukin-23, one of the immune signals that drives the gut inflammation in these conditions. Treatment usually starts with a drip into a vein and is then continued as injections under the skin, often given by the person themselves after training. It is prescribed and supervised by a specialist gut team.
How it works
In ulcerative colitis and Crohn's disease, the immune system becomes overactive in the gut, causing inflammation, ulcers and symptoms such as diarrhoea, bleeding and pain. Mirikizumab is an antibody that blocks interleukin-23, a chemical messenger that helps drive this inflammation. By quietening this signal, it reduces the inflammation, helps the gut lining heal and lowers symptoms. Because it works on a specific part of the immune system, it can also slightly weaken the body's defences against infection, which is why screening and monitoring are part of treatment.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist biologic medicine used in the UK to treat inflammatory bowel disease such as ulcerative colitis and Crohn's disease.
Practical use
How to take Mirikizumab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Treatment usually starts with a drip into a vein and then continues as injections under the skin, often given by yourself after training.
- Keep to the schedule your specialist team sets, as it works gradually to control the disease over time.
- Report any signs of infection, such as fever, cough or feeling generally unwell, to your team promptly.
- Tell your team before having any vaccinations, as live vaccines are avoided while on this medicine.
- Attend for the blood tests you are asked to have, including liver checks, while on treatment.
Weighing it up
Advantages & disadvantages of Mirikizumab
Advantages
- An effective option for moderate to severe ulcerative colitis or Crohn's disease that has not responded to other treatments.
- Targets a specific immune signal that drives gut inflammation.
- After the starting drips, it can be given as injections under the skin at home.
Disadvantages
- Can raise the risk of infections, so screening and monitoring are needed.
- Live vaccines must be avoided, and infections must be reported promptly.
- Needs specialist supervision, regular injections and blood tests, and works gradually.
Practical use
Good to know
The most important things to know about mirikizumab relate to the immune system. Because it dampens part of the body's defences, it can make infections more likely, so people are checked for hidden infections — including tuberculosis (TB) — before starting, and any signs of infection during treatment, such as fever, should be reported. Live vaccines are avoided while on it, so it is worth getting vaccinations up to date beforehand where possible. The specialist team also checks liver blood tests, as the medicine can occasionally affect the liver. Treatment starts with a drip into a vein and then continues as injections under the skin, often self-given after training. It is a long-term treatment that works gradually, and keeping to the schedule helps keep the disease under control.
Who should not take it / use with caution
- People who have had a serious allergic reaction to mirikizumab should not use it.
- It should not be started in people with an active serious infection, including untreated tuberculosis.
- It is used with care in pregnancy and under specialist guidance, weighing the benefits and risks.
Monitoring
- Screening for infections, including tuberculosis, before starting.
- Watching for signs of infection during treatment and reviewing how well symptoms respond.
- Checking liver blood tests, as the medicine can occasionally affect the liver.
Side effects
- Infections such as colds, throat or sinus infections, which can occasionally be more serious.
- Reactions where the injection is given, or during the drip.
- Headache, joint pain, or changes in liver blood tests in some people.
Key interactions
- Live vaccines should be avoided while on mirikizumab because the immune response is dampened.
- Using it with other medicines that suppress the immune system may add to the infection risk.
- Tell your team about all your medicines and any planned vaccinations.
Available as: A drip into a vein to start, then a solution for injection under the skin.
Answers
Mirikizumab: frequently asked questions
What is mirikizumab used for?
It is a biologic medicine used to treat inflammatory bowel disease, including ulcerative colitis and Crohn's disease, by blocking an immune signal that drives gut inflammation.
Why am I screened for tuberculosis first?
Because the medicine dampens part of the immune system, hidden infections such as tuberculosis can flare up, so people are checked and treated before starting.
Can I have my usual vaccinations?
Live vaccines are avoided while on mirikizumab, so it is best to get vaccinations up to date beforehand and tell your team before any new vaccine.
How is it given?
Treatment usually starts with a drip into a vein and then continues as injections under the skin, often given by the person themselves after training.
Why are my liver tests checked?
The medicine can occasionally affect the liver, so the specialist team checks liver blood tests during treatment to keep it safe.
The wider class
About Biologic (anti-IL-23 antibody)
Mirikizumab belongs to the biologic (anti-il-23 antibody) 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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