Biologics for asthma are injectable medications that target specific molecules driving airway inflammation, rather than suppressing the immune system broadly the way steroids do. There are currently seven FDA-approved biologics for asthma, and they’re reserved for people with severe asthma that isn’t controlled by standard inhalers and oral medications. Each one works differently, and choosing the right biologic depends on blood tests and the specific type of inflammation behind your symptoms.
How Biologics Differ From Standard Treatments
Most asthma medications, like inhaled corticosteroids and bronchodilators, work broadly. They reduce inflammation and open airways regardless of what’s causing the problem. Biologics take a precision approach. They’re lab-engineered antibodies designed to latch onto one specific protein or receptor in your immune system, interrupting a particular chain of inflammation before it spirals into an asthma attack.
This targeted design means biologics tend to cause fewer widespread side effects than long-term oral steroids, but it also means they only help if your asthma is actually driven by the pathway that biologic targets. That’s why biomarker testing is so important before starting one.
The Seven Approved Biologics
Each biologic falls into a category based on which inflammatory signal it blocks. Here’s how they break down:
Anti-IgE: Omalizumab (Xolair)
Omalizumab was the first biologic approved for asthma and targets IgE, the antibody your body produces during allergic reactions. By binding to IgE before it can attach to immune cells, omalizumab dampens the allergic cascade that triggers airway inflammation. Over time, it also reduces the number of IgE receptors on your immune cells, making them less reactive. It’s specifically for allergic asthma, so you need a confirmed allergy to a year-round trigger (like dust mites, pet dander, or mold) to qualify. It’s approved for patients as young as 6.
Anti-IL-5 Pathway: Mepolizumab, Reslizumab, Benralizumab, and Depemokimab
These four biologics all reduce eosinophils, a type of white blood cell that drives inflammation in many people with severe asthma. They do it in slightly different ways. Mepolizumab (Nucala) and reslizumab (Cinqair) both block IL-5, a signaling molecule that eosinophils depend on to mature, survive, and migrate to the airways. Without IL-5, eosinophil numbers drop significantly.
Benralizumab (Fasenra) takes a more aggressive approach. Instead of just blocking the IL-5 signal, it binds directly to the IL-5 receptor on eosinophils and then recruits natural killer cells to destroy them. This leads to near-complete eosinophil depletion rather than just a reduction.
Depemokimab is the newest in this group and also targets eosinophils, with the practical advantage of dosing only once every six months instead of every few weeks.
Reslizumab is the only one in this group restricted to adults 18 and older. Mepolizumab, benralizumab, and depemokimab are approved down to age 12.
Anti-IL-4/IL-13: Dupilumab (Dupixent)
Dupilumab blocks a receptor shared by two inflammatory molecules, IL-4 and IL-13. Shutting down both at once is significant because they handle different parts of the problem. IL-4 drives the production of allergy-related antibodies, promotes eosinophil migration, and pushes immune cells toward an allergic response. IL-13 is more directly responsible for mucus overproduction and the tightening and thickening of airway smooth muscle. By blocking both, dupilumab addresses a wider range of symptoms. It has a broader indication than the anti-IL-5 biologics and is approved for patients as young as 6. In the U.S., it’s also approved for people dependent on oral corticosteroids regardless of their eosinophil levels.
Anti-TSLP: Tezepelumab (Tezspire)
Tezepelumab stands apart because it works at the very top of the inflammatory cascade. It blocks TSLP, a signaling molecule released by the cells lining your airways that kicks off multiple inflammatory pathways at once. Because TSLP sits upstream of IL-5, IL-13, IL-4, and IgE, blocking it reduces all of these downstream signals. This gives tezepelumab the broadest reach of any asthma biologic. It’s the first biologic approved for severe asthma without any biomarker or phenotype restrictions, meaning it can help people whose inflammation doesn’t fit neatly into the “allergic” or “eosinophilic” categories where other biologics are ineffective. The benefit is somewhat smaller in people with low type 2 inflammation, but it still reduces flare-ups across all subgroups in clinical trials.
How Doctors Match You to a Biologic
The selection process starts with blood tests and a breathing test called FeNO, which measures nitric oxide in your exhaled breath as a marker of airway inflammation. These two biomarkers, blood eosinophil count and FeNO level, form the core of the decision.
If your eosinophils are the dominant signal (typically 300 cells per microliter or higher), the anti-IL-5 biologics tend to be most effective. If your FeNO is elevated (above 25 parts per billion) but eosinophils are relatively low, dupilumab or tezepelumab are better matched. For allergic asthma with confirmed IgE-driven triggers, omalizumab is the classic first choice.
The threshold details vary depending on which biologic is being considered. Mepolizumab typically requires at least 150 eosinophils per microliter at screening or 300 in the past year, along with two or more flare-ups requiring oral steroids in the previous year. Reslizumab generally requires 400 or more. Tezepelumab has no biomarker cutoff, making it an option when results are ambiguous or when other biologics haven’t worked.
Who Qualifies for Biologic Therapy
Biologics aren’t a first-line treatment. They’re reserved for severe asthma, which means your symptoms persist or your flare-ups continue despite being on high-dose inhaled corticosteroids plus at least one additional controller medication. Most prescribing guidelines also require a history of multiple exacerbations in the past year, typically two to four episodes that needed oral steroids, or ongoing dependence on daily oral steroids to stay stable.
Before a biologic is considered, your doctor will usually confirm that your inhaler technique is correct, that you’re actually taking your medications consistently, and that other conditions like acid reflux or chronic sinus disease aren’t making your asthma worse. Roughly 5 to 10 percent of people with asthma have the severe form that might warrant a biologic.
What Treatment Looks Like
Most asthma biologics are given as subcutaneous injections, either in a clinic or at home with a prefilled syringe or autoinjector. Dosing schedules range from every two weeks to every eight weeks depending on the medication. Depemokimab is the exception at once every six months. Reslizumab is the only one given as an intravenous infusion, which always requires a clinical setting.
For your first few doses, your healthcare provider will typically monitor you for up to two hours afterward to watch for allergic reactions. Once you’ve tolerated the medication, several of these biologics (including mepolizumab, benralizumab, dupilumab, and tezepelumab) can be self-administered at home.
You should not expect overnight results. Some people notice improvement within the first few weeks, but the full effect on reducing flare-ups often takes several months to become clear. Most guidelines suggest evaluating whether a biologic is working after about four months of consistent use.
Side Effects and Risks
Biologics are generally well tolerated compared to long-term oral steroids. The most common side effects across all of them are mild: soreness or swelling at the injection site, headaches, sore throat, fatigue, and joint or back pain. These tend to be temporary and manageable.
The more serious concern is anaphylaxis, a severe allergic reaction that can cause difficulty breathing, swelling, and a dangerous drop in blood pressure. This is rare, but it’s the reason for the post-injection monitoring period during early treatments. Omalizumab carries the most established warning for anaphylaxis among asthma biologics, though it can occur with any of them.
Biologics that reduce eosinophil counts also carry a slightly increased risk of parasitic infections. Eosinophils play a role in fighting parasites, so lowering their numbers can make you more vulnerable if you’re exposed. This is mainly a concern for people who travel to or live in areas where parasitic infections are common. Your doctor may recommend testing for existing parasitic infections before starting an anti-IL-5 biologic.