Biologic therapies for severe asthma

Find out how specialist biologic treatments called monoclonal antibodies (mAbs) can help people with severe asthma, which ones are available in the UK, and who can access them.

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What are biologic treatments for asthma?

Biologic treatments used for asthma are also known as monoclonal antibodies or mAbs. These are specialist treatments using antibodies produced from cells in a laboratory which can target specific cells in the body.

Monoclonal antibodies can treat some types of severe asthma by helping to stop body processes that cause lung inflammation. This is inflammation that may be caused by allergies or by high levels of a cell in the body called an eosinophil.

What is an eosinophil?

Eosinophils are a type of white blood cell linked to inflammation. People with severe asthma sometimes have high levels of eosinophils in the blood. This can be shown with a blood test called an ‘eosinophil count’ which calculates the number of eosinophils in your blood.

Eosinophil levels are important to help specialist asthma clinics decide what type of asthma you have, and what treatments, including biologics, will work for you best.

Dr Andy Whittamore, Asthma and Lung UK's GP

Some medicines, including oral corticosteroids, can reduce the eosinophil count result, but don’t stop taking your usual asthma medicines as prescribed - your specialist should take this into account when reviewing your test results.

Which biologic treatments are available for asthma?

There are currently sixbiological treatments approved for use in the UK and available on the NHS to treat severe asthma.

These are:

  • mepolizumab (Nucala)
  • reslizumab (Cinqaero)
  • benralizumab (Fasenra)
  • omalizumab (Xolair)
  • dupilumab (Dupixent)
  • tezepelumab (Tezspire)

Monoclonal antibodies are a very specialist, targeted treatment. They are also expensive, and there are strict criteria for who can access them.

Most monoclonal antibodies are given as an injection, either in clinic, or using pre-filled syringes at home. Reslizumab is given through an intravenous drip.

How do they treat asthma?

Biologic treatments are only available for certain types of severe asthma which are not well controlled with high doses of steroid inhalers. If you’re eligible, your specialist will work out the best biologic treatment for you.

  • Severe allergic asthma where severe symptoms are triggered by allergies. This type of asthma mostly starts in childhood. Omalizumab is a biologic that targets severe allergic asthma, reducing the allergic response.
  • Eosinophilic asthma where severe symptoms are triggered by higher levels of cells called eosinophils. This type of asthma is usually associated with adult-onset asthma. Mepolizumab, reslizumab and benralizumab are all biologics that target severe eosinophilic asthma, by reducing eosinophils.
  • Severe asthma with type 2 inflammation where severe asthma symptoms are driven by both allergies and high levels of eosinophils. Dupilumab is a biologic targeting severe type 2 inflammatory asthma. It works by damping down the inflammatory response.
  • All types of severe and uncontrolled asthma. Tezepelumab has been found to work across all types of severe and uncontrolled asthma.  It works on inflammation and reduces ‘airway responsiveness’ or ‘twitchiness’ which means it can stop airways reacting so much to triggers. Unlike other biologics, people with severe asthma can access Tezepelumab without the need for specific biomarkers, like eosinophil count, or allergy status.  

What are the benefits of biologics?

Biologic treatments can:

  • lower the risk from eosinophilic asthma or severe allergic asthma
  • allow some people to stop or reduce the dose of their oral steroids and lower the risk of side effects from these.
  • help people with severe asthma manage their symptoms and reduce asthma attacks.

Keep taking your usual asthma medicines

Never reduce or stop taking steroid medicine for asthma without speaking to your doctor. If you’ve been told to reduce your steroid tablets after starting biologics, this must always be done gradually with support and guidance from your doctor.

Risks and side effects of biologics

As with all medicines, biologic treatments can have risks and side effects.

Common side effects

The patient information leaflet for your biologic treatment will list all the possible risks and side effects. Read the leaflet carefully before starting your treatment.

Some common side effects (affecting up to 1 in 10 people) include:

  • headache
  • sinus pain
  • sore throat
  • soreness at the injection site (this should pass in a few days and may improve after you’ve had the injection a few times).

Always talk to your doctor or specialist team if you’re worried about any of these risks or side effects.

Severe allergic reactions

Biologic treatments for asthma have an increased risk of a severe allergic reaction (anaphylaxis). The risk is rare (1 in 1000) and more likely if you have a history of allergic reactions or anaphylaxis.

You may be asked to stay in the clinic for a short time after your first few treatments, so your healthcare team can make sure you’re not at risk of an extreme allergic reaction.

If you’ve been told you can self-treat at home, it’s important to know the signs of an allergic reaction, such as difficulty breathing, swelling, or feeling dizzy or unwell.

Parasitic infections

Taking biologics can, rarely, make you less resistant to parasitic infections such as cyclospora, intestinal worms, or malaria.

This means your body cannot fight off infections like this so well. Get advice from your doctor if you’re travelling to regions in the world where parasitic infections are more common than they are in the UK.

How do people get access to biologic treatments?

Biologic treatments for asthma are only available to people who have been diagnosed with severe asthma. You need to be referred to a severe asthma service before you can be considered for one.

Your specialist will only recommend biologic treatment if you meet the necessary criteria for accessing these treatments and if you’ve been taking all your medicines as prescribed.

To start the assessment for biologic treatments you’ll need an appointment at a specialist asthma clinic. This is for tests to assess:

  • your symptoms
  • your inhaler technique
  • how far you’ve been able to stick to your medicine routine
  • what type of severe asthma you have.

A specialist team will talk through your test results and discuss the most appropriate biologic for you to try.

Individual biologic treatments have their own criteria for who can access them too.

If you’re eligible for more than one biologic you should be offered a choice, and your specialist should involve you in deciding which one to try.

How soon can you start using biologics?

It’s not always easy to access biologic treatments. On average it takes about a year from being referred to a severe asthma service to getting a biologic. But that can vary.

A lot depends on how well you’ve been sticking to your current medicines, any other conditions you have, and how well matched you are to a biologic treatment (how closely your type of asthma meets the criteria).

Starting and reviewing treatment with biologics

Going to a clinic

You’ll usually need to attend a specialist asthma clinic to start treatment.

If the clinic is not nearby, this can involve travelling so you’ll need to allow for the cost and time around that, which may include costs for childcare or time off work.

You may also need to stay in the clinic for a couple of hours after your first few treatments.

This is to make sure you do not have a severe reaction. For the first few it may be better if someone can take you to the clinic, so you don’t have to drive afterwards.

Attending clinic every other week can be time-consuming and expensive. But after you’ve been for treatment three or four times at the clinic, you may be allowed to self-treat at home.

Self-injecting at home

You’ll need to go to the specialist clinic for your injection, but after a few weeks you may be told you can self-inject at home.

  • If you have a history of anaphylaxis your injections should always be given to you by a healthcare professional in the specialist clinic.
  • If you have no history of anaphylaxis you may be able to self-inject at home after your third or fourth dose, if this is something you are happy to do. But you will need to be trained how to do this, and how to recognise the signs of an allergic reaction.

The specialist team will continue to provide you with the medication to do this. These will be pre-filled syringes in multi-packs. Your dose will depend on body weight. Being allowed to self-treat at home will depend on which biologic you’re taking, and your medical history.

The Oxford Academic Health Science Network have a leaflet called Having my asthma biologic injections at home. You can download it from their website.  

How to store biologics

If you’re using biologics yourself at home, you need to store them safely. Follow all instructions given to you by your healthcare team.

You must:

  • store them in the fridge
  • keep them in their original packaging
  • keep them away from light
  • store them out of reach of children
  • use by the expiry date.

Reviewing treatment

Whatever biologic you are prescribed, you will need to review your treatment regularly. This could be every six months, and at least yearly.

It may take three to four months to see any improvement. Your specialist may use tests to see how you’re getting on, such as spirometry, FeNO, and blood tests. You may also be asked to complete a quality-of-life questionnaire.

If your treatment's not working for you, or you’re getting difficult side effects, your specialist may stop treatment and look at other options.

Contact your healthcare team if your asthma symptoms are not improving or are getting worse.

Do not stop taking either your usual asthma medicines or your biologic treatment unless your doctor tells you to. Stopping or interrupting treatment could make your symptoms come back

  • If your asthma improves with the biologic treatment, you can continue it, and review again in 12 months. You may be able to reduce the long-term steroid tablets you’re taking for your asthma.
  • If your asthma does not improve with the biologic treatment, you will need to stop the treatment and look at other options. You may need further investigations to confirm which type of asthma you have.

Criteria for biologic treatments used for asthma

Mepolizumab (Nucala) targets inflammation caused by eosinophils. It does this by lowering the number of eosinophil cells in your blood (your blood eosinophil count).

Mepolizumab may be suitable for ages six years and above. Only children aged 12 years or above can be given treatments to use at home.

It is given as an injection every four weeks. This is usually into the upper arm if someone else is doing it for you, or you’re being treated in clinic. If you’re doing it yourself at home, you self-inject into your thigh or abdomen.

You will only be offered mepolizumab if:

  • your blood eosinophil count has reached 300 cells or more 

    and 

  • you’ve had four or more asthma attacks needing steroid tablets or injections in the past 12 months  

    or

  • you have been taking steroid tablets continuously, at least equivalent to 5mg of prednisolone  per day, over the previous six months .

Reslizumab targets inflammation caused by eosinophils. It does this by lowering the number of eosinphils in your blood (your blood eosinophil count).  

Reslizumab is suitable for adults aged 18 and over. It is given as an intravenous infusion. This means you’ll be put onto a drip so the medicine can go slowly into a vein. 

You will need to go to the hospital to have this done every four weeks. 

You will only be offered reslizumab if:

  • your blood eosinophil count has reached 400 cells or more and you’ve had at least three or more asthma attacks needing steroid tablets or injections in the past 12 months  
  • you’re based in England, Wales or Northern Ireland. It’s not available in Scotland. 

Benralizumab targets inflammation caused by eosinophils. It does this by lowering the number of eosinophil cells in your blood (your blood eosinophil count).  

Benralizumab is suitable for adults aged 18 and over. It is given as an injection every four weeks for the first three doses. Once you’ve had your first three doses you only need an injection every eight weeks.

You may be offered benralizumab if:

  • your blood eosinophil count has reached 300 cells or more

and

  • you’ve had four or more asthma attacks needing steroid tablets or injections in the past 12 months.

or

  • your blood eosinophil count has reached 400 cells or more

and

  • you’ve had three or more asthma attacks needing steroid tablets or injections in the past 12 months.

or

  • you have been taking steroid tablets continuously, at least equivalent to 5mg of prednisolone per day, over the previous six months.

At 12 months, if you have responded well to benralizumab, you can continue on it, with a review each year. 

Omalizumab works by reducing the amount of a chemical called IgE in the body. IgE is produced when you have an allergic reaction. When the body produces too much IgE it can cause inflammation in the lungs.

Omalizumab can also treat rhinosinusitis with nasal polyps, a condition often seen with asthma. It is safe to use alongside antihistamines and other treatments for rhinosinusitis.

Omalizumab can be suitable for ages six and over. It is given as an injection every two weeks, or every four weeks, depending on your weight and the levels of IgE in your blood.

You will only be offered omalizumab if:

  • you’ve been on a continuous steroid tablet in the previous year or needed at least four courses of steroids in the past 12 months  

    and

  • you have an air flow obstruction, frequent daytime symptoms, and wake up at night with your asthma, and have had a positive skin prick test for allergies.


It can take 12-16 weeks for omalizumab to show benefits. If after 16 weeks there has been a good improvement to your symptoms, you’ll be able to continue with it.

Dupilumab is a treatment for severe asthma which is allergy driven. It is also used as a treatment for atopic dermatitis (eczema) and chronic rhinosinusitis with nasal polyps.

Dupilumab is suitable for ages 12 and over. It is given as an injection every two weeks. You may be able to self-inject dupilumab at home.

You will only be offered Dupilumab if:

  • you have had two or more courses of oral steroid tablets, or stayed overnight in hospital for your asthma, in the last year

    and 

  • you have a blood eosinophil count of 150 cells or more and fractional exhaled nitric oxide (FeNO) of 25 parts per billion or more, 

    and 

  • you have had four or more asthma attacks in the previous 12 months

    and

  • you are not eligible for other biologics or your asthma has not responded well enough to other biologic treatments.

Tezepelumab is a treatment for people with severe asthma which is not well controlled with high doses of inhaled steroid and another add on medicine.  

Tezepelumab is suitable for ages 12 and over.  It is given as an injection every four weeks.  You may be able to self-inject tezepelumab at home.  

You will only be offered tezepelumab if:

  • you’ve had 3 or more exacerbations in the last year
  • you’re taking maintenance oral steroids.

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