Natalizumab (Tysabri and Tyruko)

Natalizumab is a disease modifying therapy (DMT) used to treat rapidly evolving severe relapsing remitting multiple sclerosis (RRMS) and highly active RRMS.

DMTs are treatments for people with multiple sclerosis (MS) that can help change the course of your MS by reducing the number of relapses and slowing down the buildup of disability in the long term.

You can be given natalizumab as a drip into a vein (intravenous infusion) or as an injection under the skin (subcutaneous injection) once every 4 weeks. It reduces the number of relapses by about 70% and slows down disability progression.

The brands available on the NHS are called Tysabri and Tyruko. Tysabri is available as an infusion and an injection. Tyruko is currently only available as an infusion.

On this page we cover who can take natalizumab, how it works, its benefits and possible side effects.

Disease modifying therapies (DMTs) are offered to people with active relapsing multiple sclerosis.

Natalizumab is used for treating adults with rapidly evolving severe relapsing remitting multiple sclerosis (RRMS) and highly active RRMS.

• Rapidly evolving severe RRMS is when you have had two or more relapses in the previous year and an MRI scan shows evidence of disease activity (new, active or enlarging lesions).
• Highly active RRMS is when you continue to experience disease activity (relapses and/or new, active or enlarging lesions on an MRI scan) despite treatment with another DMT.

In England, Wales and Northern Ireland, you can only be offered natalizumab for highly active RRMS if cladribine (Cladribine Merck, also known as Mavenclad) isn't suitable for you. For example, this may be the case if you’re trying for a baby or you’re pregnant.

Your MS team will assess whether natalizumab is suitable for you and whether you meet the NHS criteria for treatment (NHS England).

Natalizumab can only be prescribed by a neurologist.

We have information about other DMTs for treating relapsing remitting MS and progressive MS.

In MS, immune cells mistakenly enter the brain and spinal cord (central nervous system) and attack the protective covering around your nerves (myelin). Natalizumab works by attaching to immune cells in your bloodstream. This stops them from being able to pass into the central nervous system and cause damage to your nerves. This reduces inflammation, helps prevent new lesions forming, and slows MS disease activity.

Tysabri and Tyruko contain the same active ingredient (natalizumab). Tyruko is a similar biological medicine (biosimilar) to Tysabri. They are equal in terms of effectiveness and safety.

Natalizumab weakens some parts of your immune system and increases your risk of infections. Because of the way it works on your immune system, it may be harder for your body to deal with certain infections.

The disease modifying therapies (DMTs) for treating relapsing remitting MS (RRMS) are grouped according to how effective they are (efficacy) at reducing the number of relapses you may have. 
The therapies are described as:

• moderately effective – reduce relapses by up to 50%
• highly effective – reduce relapses by more than 50%.

Natalizumab is considered a highly effective therapy. In clinical trials, people taking natalizumab had 68% fewer relapses than people taking placebo (a dummy medicine). MRI scans showed people taking natalizumab had fewer new or enlarging lesions than those in the placebo group. Natalizumab also slowed down the build-up of disability associated with MS.

Read more about how medicines are developed.

Before you start taking natalizumab, your MS team will discuss the benefits and possible risks of the therapy with you. Together, you will decide if the benefits outweigh any potential risks based on your circumstances. We have more information about starting a disease modifying therapy (DMT) and things to consider.

It is important that you tell your MS team if you have any other health problems or are taking other medicines. Your neurologist will need to know if you have previously taken other medicines which suppress the immune system (for example mitoxantrone, azathioprine, cyclophosphamide or methotrexate).

You cannot be given natalizumab if:

• you are allergic to natalizumab or any of the other ingredients in the medicine
• you have been diagnosed with a serious brain infection called progressive multifocal leukoencephalopathy (PML)
• you are taking medicines that affect your immune system
• you have a condition that weakens your immune system, for example HIV (NHS.UK)
• you have cancer, unless it is a type of skin cancer called basal cell carcinoma (Cancer Research UK).

If you're considering treatment with natalizumab or any other disease modifying therapy (DMT), your MS team will proactively discuss family planning and the possibility of pregnancy with you where appropriate.

Natalizumab should only be used during pregnancy if it's recommended by your neurologist. Current research suggests that taking natalizumab during pregnancy does not affect pregnancy outcomes such as live birth, miscarriage and stillbirth rates.

Exposure to natalizumab during late pregnancy can increase your baby's risk of a low red blood cell count (anaemia) and low platelet count (thrombocytopenia) when they’re born. However, cases are usually mild to moderate and do not require treatment. Your baby will be monitored until their counts return to normal. Apart from these blood conditions, exposure to natalizumab during pregnancy has not been found to affect the health of the baby.

If you continue natalizumab through pregnancy, your neurologist, obstetrician or midwife may recommend an ultrasound during your third trimester to check your baby for signs of anaemia, and a blood test to check your baby’s blood count when they're born.

Natalizumab transfers into breastmilk but only in small amounts. This means that little to none of the medicine would be passed to your baby through breastfeeding. You should speak to your MS team if you'd like to continue breastfeeding while taking natalizumab.

If you're considering or currently receiving natalizumab while trying for a baby, your MS team should discuss the risks and benefits of stopping versus continuing treatment during pregnancy. Ideally this should be discussed before you get pregnant. Your MS team may consider and discuss the following with you.

• Your risk of significant relapses if natalizumab is stopped (known as rebound activity). While women tend to experience fewer relapses during pregnancy, this may not be enough to control MS disease activity and rebound activity if you stop treatment with natalizumab.
• The possibility of switching to an alternative highly effective DMT before you become pregnant. It is not recommended that you switch from natalizumab to another DMT during pregnancy.
• The increased risk of anaemia and thrombocytopenia in your baby if you continue natalizumab during pregnancy and how this will be monitored.

If you continue receiving natalizumab during pregnancy, it is recommended that you have the dose every 6 to 8 weeks (rather than every 4). This is to reduce your baby's exposure to natalizumab. Your last dose during pregnancy should be given no later than 34 weeks. After your baby is born, natalizumab should be restarted within 6 to 8 weeks of your last dose.

If you continue natalizumab throughout your pregnancy, check with your MS team and maternity team before your baby receives any live vaccines, such as the rotavirus vaccine (NHS.UK), in their first 6 months. This is because your baby has been exposed to natalizumab, and their immune system may be affected during this time.

Before starting natalizumab, you will have:

• blood tests to measure blood cell counts (NHS.UK) and to check your liver and kidney function.
• an MRI scan (up to 3 months before)
• a blood test to work out if you have previously been infected by the JC virus.

The JC virus test helps to assess your risk of a serious brain infection called progressive multifocal leukoencephalopathy (PML) if you take natalizumab.

You can be given natalizumab through a drip into your vein (intravenous infusion) or as pre-filled, ready-to-use injections (subcutaneous injection) once every 4 weeks.

Natalizumab infusion

An infusion of natalizumab is generally done in a hospital infusion clinic. It is given through a drip into a vein, usually in your arm. Before each infusion, your blood pressure, temperature and pulse rate will be taken. The infusion itself takes about 1 hour. You will be monitored by a health professional during the infusion and for 1 hour after for any signs of a reaction. You may be in the hospital for up to 3 hours for an infusion.

Natalizumab injections

The injections are given under the skin, in your thigh, tummy (abdomen) or the back of your arm. Each dose is given as 2 pre-filled injections that are ready to use. Both injections should be administered one after the other, with no more than 30 minutes between them. The injections can be done by a healthcare professional in a clinic. If suitable, you may be given the option to have the injections at home, administered either by a nurse, yourself or a caregiver.

Your neurologist will assess whether administration of natalizumab at home is suitable for you. This may be considered for people who have had at least 6 doses of natalizumab in a clinical setting and have not had any serious reactions. If you can take it yourself at home, you will be supervised by a healthcare professional when you take the first 2 doses. You must review the pre-administration checklist (PDF, 33.5KB) before each dose.

Your MS nurse will show you how to do the injections, discuss the practicalities and offer advice or training and ongoing support if you need it.

The injections will be delivered to your home by a homecare company.

Natalizumab injections should be stored in the fridge.

Stopping natalizumab

You should not stop natalizumab without discussing your ongoing treatment with your neurologist, as your MS may become more active after stopping this therapy.

Your MS team will continue monitoring you for 6 months after you stop taking natalizumab. This is because the risk of PML continues during this time. If you notice any symptoms of PML you should contact your MS team immediately.

All medicines, including disease modifying therapies (DMTs), can potentially cause side effects.

Some people may not experience side effects from taking natalizumab. Some may find that any side effects ease after the first month or two as their body adapts to the medicine. For others, side effects may persist.

Your MS team will discuss potential side effects of the treatment with you and help you understand your risk. They will also tell you how to manage and report any side effects.

Very common side effects (may affect more than 1 in 10 people) of natalizumab include:

• urinary tract infections
• sore throat and runny or blocked nose
• headache
• dizziness
• feeling sick (nausea)
• tiredness.

Common side effects (may affect up to 1 in 10 people) of natalizumab include:

• bruising, redness, pain, itching or swelling around the place you've had your infusion or injection
• decrease in red blood cells (anaemia) – symptoms are pale skin, feeling breathless or lacking energy
• allergic reaction (hypersensitivity)
• itchy rash (hives) (NHS.UK)
• dormant herpes infections becoming active again – for example the varicella-zoster virus that causes chickenpox and shingles, and the herpes simplex virus that causes blisters or ulcers around the mouth (cold sores) or genitals
• reddening of the face or body (flushing).

Serious allergic reactions (anaphylactic reactions) are uncommon, affecting up to 1 in 100 people. You will be monitored for signs of an allergic reaction for 1 hour after your infusion or injection.

Treatment with natalizumab can cause certain herpes viruses to become active again. There have been cases where the reactivation of the virus has led to other serious, life-threatening brain infections – encephalitis (NHS.UK) or meningitis (NHS.UK).

Natalizumab may affect liver function, but this generally recovers when treatment is stopped.

Progressive multifocal leukoencephalopathy (PML) is an uncommon but serious brain infection that can cause severe disability and, in some cases, death. Treatment with natalizumab can increase your risk of PML.

PML is caused by the JC virus, a common infection completely unrelated to MS. The JC virus is normally kept under control by your immune system and does not cause any symptoms. However, natalizumab can weaken the immune system, making it harder for your body to fight infections. This can lead to the JC virus becoming active and causing inflammation and damage in the brain.

When you start taking natalizumab you will be informed of the early signs of PML. Symptoms of PML can be similar to an MS relapse.

If PML is suspected at any point during treatment, natalizumab will be stopped immediately.

As natalizumab has been used for many years, neurologists have a good understanding of the risks associated with treatment and how to reduce the chance of serious side effects like PML.

PML risk is individual to each person. If you have not been infected with the JC virus before, your risk of PML is likely to be very small with around 1 in 10,000 people affected. However, various factors can increase your risk of PML with natalizumab. You may be at higher risk if:

• you have antibodies to the JC virus in your blood
• you've been on natalizumab for more than 2 years
• you've taken medicines in the past that suppress your immune system.

Depending on the factors that apply to you, the risk of PML can increase to around 1 in 100.

Your neurologist will explain your personal risk of PML. If you choose to be treated with natalizumab, your risk of PML will continue to be reviewed while on treatment. You will also have regular monitoring for early signs of PML.

After two years of treatment with natalizumab, your neurologist will review your risk of PML and remind you of the early signs and symptoms to look out for.

Your neurologist may recommend treatment with natalizumab every 6 weeks if you are at higher risk of PML. Research has found this can significantly reduce your risk.

You can estimate your risk of developing PML by using this risk calculator (ClinicSpeak) which was developed by the Barts MS Research team at Queen Mary University of London.

Due to the potential risk of side effects, you should be given a patient alert card when you start natalizumab. This contains important safety information needed before and during treatment.

For a full list of side effects, see the Patient Information Leaflets for natalizumab (Tysabri or Tyruko).

• Patient Information Leaflet for Tysabri (EMC)
• Patient Information Leaflet for Tyruko (MHRA)

You can report side effects through the Yellow Card scheme. Reporting side effects can make a big difference to other people using the same medicine as you.

People with MS are generally encouraged to have vaccinations which are part of the national vaccinations programme (NHS.UK). Where possible, your MS team will advise you to get relevant vaccinations before you start taking a disease modifying therapy (DMT).

If you've not started treatment with natalizumab yet, it’s recommended that inactivated (non-live) vaccines are given at least 2 weeks before treatment starts. Live vaccines should be given at least 4 weeks before starting natalizumab. This is to make sure your immune system builds up a good response to the vaccines.

If you're already on natalizumab, inactivated (non-live) vaccines are considered safe for you to have. Your body's response to vaccines may be slightly reduced but they still provide a good level of protection.

Live vaccines are not recommended for people on natalizumab. This is because there is a small potential risk of developing vaccine-related infections.

In a small number of cases, such as when there is a high risk of catching a serious infection, a live vaccine may be considered. Your healthcare team would carefully assess whether the benefits of vaccination are greater than the potential risks.

You will have blood tests to check your blood cell counts, liver function and kidney function, usually every 3 to 6 months.

You should have an MRI scan at least once a year while on treatment with natalizumab to monitor for signs of progressive multifocal leukoencephalopathy (PML). If you’re at higher risk of PML, you should have an MRI scan every 3 to 6 months. An MRI scan will also be done if you have any symptoms of PML.

If a previous blood test found you have not been exposed to the JC virus, you should have another blood test every 6 months. This is because it is possible to be infected by the JC virus at any time.

If a previous blood test found low levels of JC virus antibodies and you’ve been on natalizumab for 2 years, it’s recommended that your blood is retested every 6 months.

A small number of people taking natalizumab may develop antibodies that reduce how well the treatment works. If your MS team suspects this, they can do a blood test to check for these antibodies (known as neutralising antibodies). If they are found, your MS team may recommend switching to a different disease modifying therapy (DMT).

• Patient Information Leaflet – Tysabri intravenous infusion (EMC)
• Patient Information Leaflet – Tysabri subcutaneous injection (EMC)
• Patient Information Leaflet – Tyruko intravenous infusion (MHRA)
• Patient Alert Card – Tysabri (EMC)
• Patient Alert Card – Tyruko (EMC)
• Understanding your risk of PML with natalizumab (ClinicSpeak) – a PML risk calculator developed by the Barts MS Research team at Queen Mary University of London.

This information has been developed by the MS Trust Health Information team. Our team produces accurate evidence-based information to help you navigate your every day – working alongside health professionals. We would like to thank the following health professionals for checking the clinical accuracy of this information:

• Stavroula Charisi, MS Specialist Pharmacist, University Hospital Southampton NHS Foundation Trust
• Chammi Karunathilaka, MS Nurse Specialist, Royal Free London NHS Foundation Trust
• Nicholas Cunniffe, Consultant Neurologist, Cambridge University Hospitals NHS Foundation Trust.