Reviewed by: HU Medical Review Board | Last reviewed: December 2022

Biologics are drugs derived from living sources. They are made of proteins and other substances isolated from living cells. They work as treatments by targeting a certain molecule in the body.1

A few biologics treat moderate to severe asthma. They are not usually the first option used to treat asthma. Your doctor may suggest them if other drugs do not control your asthma symptoms. Talk to your doctor about the risks and benefits of biologics.2

How do biologics work?

All biologics used to treat asthma are monoclonal antibodies. Antibodies are proteins. They are made by cells as part of our normal immune response. Antibodies recognize parts of specific germs that cause illness (pathogens). This triggers our immune system to react to infections.1,3

Monoclonal antibodies are made in the lab. They act like normal antibodies. They are designed to target or block a specific protein in the body. They are called “monoclonal” because they are created as clones (exact copies).3

Certain monoclonal antibodies treat asthma by blocking proteins that increase inflammation. These proteins activate our immune cells. Some examples of these proinflammatory proteins include:2

  • Immunoglobulin E
  • Interleukin-5
  • Interleukin-5 receptor
  • Interleukin-4 receptor
  • Thymic stromal lymphopoietin

Blocking these proteins can reduce inflammation. This helps reduce symptoms of asthma, especially asthma linked to allergies. It also can:2

  • Reduce the frequency of asthma attacks
  • Improve quality of life
  • Reduce the need for oral or inhaled corticosteroids


Biologics are used to treat moderate or severe asthma. Your doctor may suggest them if inhaled corticosteroids and long-acting beta agonists do not control your symptoms. Biologic drugs used to treat asthma include:4-7

The choice between biologic drugs depends on many factors. For example, Xolair is better for allergic asthma. Nucala, Cinqair, and Fasenra are better for people with eosinophilic asthma. Personal factors – including cost and that some are given as shots – also affect the decision.4

What are the possible side effects?

Possible side effects depend on the specific biologic you take. Some common side effects of biologics used in asthma include:4,8

  • Injection site reactions
  • Muscle or joint aches
  • Headaches
  • Back pain
  • Sore throat
  • Fatigue or weakness

Serious side effects are rare, but possible. For example, serious allergic reactions can happen after taking biologics. Talk to your doctor or get emergency help if you notice symptoms of allergic reactions.4

These are not all the possible side effects of biologics. Talk to your doctor about what to expect when taking biologics. Call your doctor if you have any changes that concern you when taking biologics.

Other things to know

Take biologics exactly as your doctor prescribes. Biologics are usually taken as an injection under the skin (subcutaneously). Some are taken as an intravenous (through the vein) infusion. You may need to take biologics every 2 to 4 weeks.4,8

You may need 4 to 6 months of treatment to see results. Your doctor will monitor you during this time for side effects. They will then see how well the biologic drug controls your symptoms. If your symptoms stay controlled for at least 3 months, your doctor may step down your treatment.2,5

Children under 6 years old should not be given any of these drugs. Benralizumab and tezepelumab should only be taken by people over 12 years old. Reslizumab should only be taken by people over 18 years old.8

Before taking biologics, tell your doctor your full health history. Other medical conditions or drugs you take can make biologics less safe. Tell your doctor about:

  • Any allergies or history of severe allergic reactions
  • History of other medical conditions, especially breathing problems and infections
  • Other medicines you take, including over-the-counter drugs and supplements
  • Pregnancy or plans to become pregnant
  • Breastfeeding or plans to breastfeed

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