Tezepelumab

Most approved asthma biologics target a single downstream cytokine in the type 2 inflammatory pathway. For example, mepolizumab and benralizumab block IL-5 (which drives eosinophil production), omalizumab targets IgE (relevant only in allergic asthma), and dupilumab blocks the IL-4/IL-13 receptor. These approaches are effective but mainly benefit patients with a specific eosinophilic or allergic phenotype. Tezepelumab is different because it targets TSLP — a cytokine released by the airway epithelium before the inflammatory cascade even begins. By blocking TSLP, it simultaneously suppresses eosinophilic inflammation, allergic sensitization, mast cell activation, and non-type-2 neutrophilic inflammation. This means tezepelumab can work in a much broader range of patients, including those with low blood eosinophil counts who may not respond to other biologics. In the pivotal NAVIGATOR trial, tezepelumab reduced exacerbations by approximately 70% overall and showed significant benefit even in the subgroup with eosinophil counts below 300 cells/µL — a population that historically had fewer biologic options.

Tezepelumab is FDA-approved for adults and adolescents aged 12 years and older with severe uncontrolled asthma as an add-on maintenance treatment. 'Severe uncontrolled asthma' generally means that despite being on a medium-to-high dose inhaled corticosteroid plus at least one additional controller medication (such as a long-acting beta-agonist), you are still experiencing frequent exacerbations, significant symptoms, or are dependent on oral corticosteroids. Unlike some other biologics, tezepelumab does not have a minimum blood eosinophil count or IgE level requirement — it is indicated regardless of your asthma phenotype. Your healthcare professional will assess your eligibility based on your symptom burden, exacerbation history, current medications, and overall health condition. It is not appropriate for mild or moderate asthma, and it is never used as a rescue inhaler. If you think you may be a candidate, talk to your doctor or an asthma specialist (pulmonologist or allergist) for a thorough evaluation.

Tezepelumab is given as a subcutaneous (under the skin) injection once every four weeks (monthly). The recommended dose is 210 mg, which comes prefilled in either a single-dose syringe or an autoinjector pen. Injections can be given in the abdomen, upper thigh, or upper arm. Your first injection will typically be given in a clinical setting so that a healthcare professional can observe you for any allergic reaction. After proper training, many patients are able to self-inject at home using the autoinjector pen. Your care team will walk you through the injection technique, including how to inspect the solution before use (it should be clear to opalescent with no visible particles), how to rotate injection sites to avoid skin irritation, and how to safely dispose of used devices. You should never skip a dose without speaking to your doctor, as consistent monthly dosing is important for maintaining asthma control.

The most common side effects of tezepelumab are generally mild and include injection site reactions such as redness, swelling, or pain where the shot was given, pharyngitis (sore throat), arthralgia (joint pain), back pain, headache, and upper respiratory tract infections. These occurred at slightly higher rates than placebo in clinical trials but were rarely severe enough to stop treatment. The most important serious side effect to be aware of is an allergic reaction (hypersensitivity). Although rare, tezepelumab can cause anaphylaxis — a potentially life-threatening allergic reaction that may include hives, difficulty breathing, swelling of the face or throat, rapid heartbeat, and dizziness. This most commonly occurs shortly after injection but can be delayed by hours or days. If you experience these symptoms, seek emergency medical care immediately. There is also a theoretical risk of increased susceptibility to parasitic infections, since TSLP is part of the immune defense against intestinal worms. Your overall risk of side effects is considered low relative to the benefits in eligible patients, but your healthcare professional will monitor you regularly.

Tezepelumab has a low risk of traditional drug-drug interactions because, unlike small-molecule drugs, it is not processed by the liver's cytochrome P450 enzyme system. However, there are important clinical considerations. You should continue taking your inhaled corticosteroids and other prescribed controller medications — tezepelumab works alongside these, not instead of them. If your asthma improves significantly, your doctor may gradually taper oral corticosteroids if you are taking them; this must never be done abruptly because of the risk of adrenal insufficiency. Regarding vaccines, inactivated and recombinant vaccines (including flu shots and COVID-19 vaccines) are safe to receive while on tezepelumab. Live attenuated vaccines — such as the live nasal flu vaccine, oral typhoid vaccine, or yellow fever vaccine — are not recommended during therapy because the immunomodulatory effects of tezepelumab may reduce their effectiveness or cause problems. Always remind any healthcare provider, pharmacist, or travel medicine clinic that you are on a biologic medication before receiving any vaccination.

The safety of tezepelumab during pregnancy and breastfeeding has not been fully established in human studies. It falls under the new FDA Pregnancy and Lactation Labeling Rule (PLLR) system, which replaced the old letter categories (A, B, C, D, X) with more detailed descriptive information. Like all IgG monoclonal antibodies, tezepelumab is expected to cross the placenta, with fetal exposure increasing as pregnancy progresses — particularly in the second and third trimesters. Animal studies did not demonstrate direct fetal harm, but animal data do not always predict human outcomes. It is currently unknown whether tezepelumab passes into human breast milk, though most large IgG antibodies are present in low concentrations in milk and have poor oral bioavailability in infants. If you are pregnant, planning to become pregnant, or breastfeeding, talk to your doctor before starting or continuing tezepelumab. Uncontrolled severe asthma itself poses significant risks to both mother and baby, so the decision should be made carefully weighing potential risks against the benefits of asthma control.