Clifford W. Bassett, MD, is an allergy and clinical immunology specialist at Schweiger Dermatology and Allergy Group in New York City. He is a clinical associate professor of medicine at NYU Grossman School of Medicine, a teaching faculty member at Weill Cornell Medical College, and serves on the Medical Scientific Council of the Allergy and Asthma Foundation of America. The information here reflects his knowledge and experience as a medical professional.
Mepolizumab (Nucala) is a biologic drug in the class of drugs known as interleukin-5 (IL-5) antagonist monoclonal antibodies. These drugs treat specific inflammatory conditions driven by high levels of eosinophils (a type of white blood cell). They work by binding to interleukin-5 — a key immune system protein — in your bloodstream and tissues. Once IL-5 proteins have the drug attached to them, they can no longer lock onto eosinophils and signal them to start the inflammation response.
Your doctor may prescribe Nucala as a maintenance drug for you if you have an eosinophilic disorder that causes inflammation in your body. The FDA first approved it in 2015 for the treatment of severe asthma, and in 2017 for the treatment of EGPA (eosinophilic granulomatosis with polyangiitis). Then, the FDA approved Nucala to treat hypereosinophilic syndrome (HES) in 20202, then as a treatment of nasal polyps in 2021, and most recently, for treatment of chronic obstructive pulmonary disease (COPD).
We spoke to Clifford W. Bassett, MD, an allergist and immunologist at Schweiger Dermatology and Allergy in Gramercy, New York, and a clinical associate professor at NYU Grossman School of Medicine, about how Nucala works, who it's for, and how to know if it's right for you.
Who is this treatment for?
Nucala is FDA-approved for people age 6 and older with severe eosinophilic asthma, meaning asthma that stays hard to control even with regular treatment. It is also approved for adults with chronic sinus disease with nasal polyps.
Asthma is different from person to person. Some people have symptoms now and then, while others have regular symptoms or flare-ups and need ongoing treatment. This is often called intermittent or persistent asthma, and persistent asthma may be mild, moderate, or more severe.
Asthma can also be sorted by the type of inflammation. In eosinophilic asthma, eosinophils, a type of white blood cell, contribute to the inflammation, and a simple blood test can show this. In non-eosinophilic asthma, they are not a major part of the problem. Both are asthma, but the treatment choices may differ. Nucala is one option for reducing asthma flare-ups over time.
Nasal polyps are soft, benign (noncancerous) growths in the nose and sinuses, often linked with chronic sinus disease. Most are the eosinophilic or "allergic" type. They can cause stuffiness, mucus, pressure, and loss of smell. Nasal polyps and asthma often go together, because both can come from the same kind of inflammation. Nucala is also approved to treat adults with chronic rhinosinusitis with nasal polyps.
How does this treatment work?
Nucala is a biologic. A biologic is a prescription medicine that works on one specific part of the inflammation. It is different from usual asthma or sinus medicines like inhalers, nasal sprays, and allergy pills. Biologics are usually added when regular treatment is not working well enough, and they do not simply replace the medicines already in use. If a biologic is helping, some people may later need fewer medicines or lower doses, especially oral steroids. Changes should only be made with your prescribing healthcare professional.
Nucala is a biologic that blocks IL-5, a signal that helps eosinophils grow and stay active. By lowering eosinophils, it may reduce inflammation in the lungs and sinuses.
How is this treatment different from other biologics?
Biologics for asthma include Nucala (mepolizumab), Xolair (omalizumab), Fasenra (benralizumab), Dupixent (dupilumab), Tezspire (tezepelumab), and Cinqair (reslizumab). They do not all work the same way or suit the same people. Fewer are approved for nasal polyps; Nucala, Dupixent, and Xolair are options for adults with chronic sinus disease with nasal polyps. Nucala is also approved for certain adults with chronic obstructive pulmonary disease (COPD), a long-term lung condition that can cause coughing, mucus, and shortness of breath.
How do you take it?
Nucala is a shot you take under the skin using a prefilled syringe or autoinjector, typically in the thigh or belly. You take a dose every four weeks. The dose depends on the condition being treated. Your doctor will determine the length of your treatment based on your condition and how well you respond to the medication.
Do not stop or change asthma medicines, inhalers, or other prescribed medicines unless your treating provider or specialist specifically advises you to do so.
How quickly will I know if it is working?
It may take time to see the full benefit. Eosinophil levels in the blood may fall quickly, but feeling better can take longer. For asthma, useful signs are fewer flare-ups, fewer urgent visits, less need for oral steroids, and better breathing. For nasal polyps, signs include less stuffiness, better smell, and fewer sinus problems. The Asthma Control Test, or ACT, is a short questionnaire that helps track control, and a peak flow meter is a simple way to follow breathing over time.
How do I know if this treatment is right for me?
For the right person, Nucala can work. In studies of severe eosinophilic asthma, people taking Nucala had fewer flare-ups than those given a placebo, along with better control and quality of life, and some were able to lower their daily oral steroid dose over time. For some adults with nasal polyps, it may reduce blockage, improve sense of smell, and lower the need for sinus surgery. Results differ from person to person.
The care team can review symptoms, flare-ups, inhaler use, ACT scores, breathing tests, blood work, side effects, and nasal polyp symptoms to decide whether to continue, change other treatments, or try a different biologic.
The choice of a biologic should be made with your specialist or treating provider. It depends on your asthma or nasal polyp symptoms, prior treatment, blood tests, other health conditions, and personal preferences.
Who can help me choose the right treatment?
For asthma of any level, an allergy and immunology specialist or a pulmonary medicine doctor is the healthcare professional most likely to discuss and prescribe these medicines. They are prescribed by specialists most of the time, but primary care providers can prescribe them too, especially those who treat many patients with persistent asthma.
For nasal polyps, an ear, nose, and throat specialist leads care and performs any needed surgery. The best choice depends on the type of disease, what has been tried, test results, other health conditions, safety, insurance coverage, and what you prefer. The point is not to request a medicine after seeing an ad, but to know there are options and have a good talk about whether a biologic may help.
Where can I learn more?
There's a great deal happening in allergy, asthma, hives, epinephrine options, and the impact of climate change on allergic and respiratory conditions. For general health information on asthma, I recommend the Asthma and Allergy Foundation of America, a patient organization for people with asthma and allergies, as well as the Global Initiative for Asthma, which has resources such as evidence-based strategy documents for asthma management.
Remember that this and other information sources are for general education only. They are not medical advice and do not replace an individualized discussion with your treating healthcare professional. As you decide on treatment, make sure you talk to your own doctor about every possible benefit or risk. Please also read the information that comes with your prescription.
Related Links 
