Xolair (Omalizumab)
omalizumab — recombinant humanised anti-IgE monoclonal antibody (IgG1κ)
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Moderate-to-severe persistent allergic asthma | Adults and children ≥6 yr with positive aeroallergen test and inadequate ICS control | Add-on controller | FDA Approved |
| Chronic rhinosinusitis with nasal polyps (CRSwNP) | Adults ≥18 yr with inadequate response to nasal corticosteroids | Add-on maintenance | FDA Approved |
| IgE-mediated food allergy — reduction of allergic reactions including anaphylaxis with accidental exposure | Adults and children ≥1 yr | Adjunct to food allergen avoidance | FDA Approved (Feb 2024) |
| Chronic spontaneous urticaria (CSU) | Adults and adolescents ≥12 yr who remain symptomatic despite H1 antihistamines | Add-on to H1 antihistamine | FDA Approved |
Omalizumab was the first anti-IgE biologic and remains the only one approved across four distinct allergic/immune conditions. In allergic asthma, it reduces exacerbation rates and allows corticosteroid dose reduction in patients with elevated IgE and documented aeroallergen sensitisation. For CSU, it provides relief in patients refractory to antihistamines regardless of IgE level. The 2024 food allergy approval represents a new therapeutic paradigm, reducing the severity of allergic reactions from accidental food exposure—though it does not replace allergen avoidance or emergency epinephrine.
Omalizumab is NOT indicated for acute bronchospasm, status asthmaticus, or emergency treatment of anaphylaxis. It is not indicated for forms of urticaria other than CSU.
Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Allergic asthma — adults and adolescents ≥12 yr | 75–375 mg SC q2–4wk | Same as starting; no titration | 375 mg q2wk (750 mg per 4-wk period) | Dose and frequency determined by pre-treatment serum total IgE (30–700 IU/mL) and body weight (30–150 kg) using PI Table 1 Administer ≥0.016 mg/kg per IU IgE/mL per 4-wk period |
| Allergic asthma — children 6 to <12 yr | 75–375 mg SC q2–4wk | Same as starting | 375 mg q2wk | Dose from PI Table 2; IgE range 30–1300 IU/mL, weight 20–150 kg Adjust dose for significant weight changes during treatment |
| CRSwNP — adults ≥18 yr | 75–600 mg SC q2–4wk | Same as starting | 600 mg q2wk | Dose from PI Table 3; based on IgE and weight; add-on to nasal corticosteroids Higher doses possible than asthma due to expanded IgE/weight matrix |
| IgE-mediated food allergy — adults and children ≥1 yr | 75–600 mg SC q2–4wk | Same as starting | 600 mg q2wk | Dose from PI Table 4; IgE 30–1850 IU/mL, weight ≥10 kg; broadest dosing matrix Does NOT replace allergen avoidance or emergency epinephrine |
| CSU — adults and adolescents ≥12 yr | 150 or 300 mg SC q4wk | 150 or 300 mg SC q4wk | 300 mg q4wk | NOT based on IgE or body weight 300 mg may be given as one 300 mg/2 mL injection or two 150 mg/mL injections |
Total IgE levels rise during omalizumab treatment (due to formation of slow-clearing omalizumab-IgE complexes) and remain elevated for up to one year after discontinuation. Therefore, IgE levels measured during therapy or within one year of stopping cannot be used to recalculate doses. If treatment is interrupted for less than one year, use the original pre-treatment IgE. If interrupted for one year or more, retest IgE before restarting.
Initiate omalizumab in a healthcare setting equipped to manage anaphylaxis. Observe patients for an appropriate period after each injection. Self-administration with prefilled syringe or autoinjector may be considered after at least 3 doses without hypersensitivity, in patients with no history of anaphylaxis to omalizumab or other agents (except food for food allergy indication), who can recognise and treat anaphylaxis. The autoinjector is only for patients ≥12 years.
Pharmacology
Mechanism of Action
Omalizumab is a recombinant humanised IgG1κ monoclonal antibody that selectively binds to the Cε3 domain of human immunoglobulin E (IgE) at the same site used by the high-affinity IgE receptor (FcεRI). By capturing free circulating IgE, omalizumab prevents IgE from engaging FcεRI on mast cells and basophils, thereby blocking the initial step of the allergic cascade. This results in a marked reduction in surface FcεRI receptor density on effector cells—an effect that develops progressively over weeks of treatment. The net outcome is reduced mast cell and basophil degranulation upon allergen exposure, leading to decreased histamine, leukotriene, and cytokine release. In allergic asthma, this translates to reduced airway inflammation and exacerbation frequency. In CSU, the exact mechanism is less well characterised, but is thought to involve downregulation of FcεRI on skin mast cells and basophils. In IgE-mediated food allergy, omalizumab raises the threshold of allergen exposure needed to trigger a reaction.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Slow SC absorption; Tmax 7–8 days; bioavailability ~62% | Extended Tmax means clinical effect builds over several weeks; steady state reached by ~6 months of dosing |
| Distribution | Vd 78 ± 32 mL/kg; no specific organ uptake; does not cross BBB significantly; crosses placenta (IgG); excreted in breast milk at 0.15% of maternal serum | Distribution similar to endogenous IgG; weight-based dosing accounts for body-size variation |
| Metabolism | Degraded in hepatic reticuloendothelial system (RES) and endothelial cells; standard IgG clearance pathways plus target-mediated clearance via omalizumab-IgE complex formation | No CYP enzyme involvement; minimal drug-drug interaction potential; clearance approximately doubles with doubling of body weight |
| Elimination | Asthma: t½ ~26 days; apparent CL 2.4 ± 1.1 mL/kg/day. CSU: t½ ~24 days; apparent CL ~240 mL/day (3.0 mL/kg/day) | Long half-life supports q2–4 week dosing; total IgE rises during treatment (slower clearance of omalizumab-IgE complexes vs free IgE) |
Side Effects
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Injection site reactions (any severity) | 45% (vs 43% placebo) | Bruising, redness, warmth, pain, itching; majority within 1 h; severity decreases with subsequent doses; severe ISRs in 12% vs 9% placebo |
Headache was reported in 15% of asthma trial patients but at similar rates to placebo and is therefore not considered drug-attributable in this indication. However, in CSU trials headache was more frequent with omalizumab (150 mg: 12.0%; 300 mg: 6.1%) than placebo (2.9%).
| Adverse Effect | Incidence (Omalizumab vs Placebo) | Clinical Note |
|---|---|---|
| Arthralgia | 8% vs 6% | Most common musculoskeletal complaint; not dose-related |
| Pain (generalised) | 7% vs 5% | Non-specific; not clearly attributable to drug |
| Leg pain | 4% vs 2% | More common than arm pain |
| Fatigue | 3% vs 2% | Mild; does not typically limit activity |
| Dizziness | 3% vs 2% | Consider monitoring during initial doses |
| Fracture | 2% vs 1% | Causal relationship not established |
| Arm pain | 2% vs 1% | May relate to injection site proximity |
| Pruritus | 2% vs 1% | Evaluate for systemic hypersensitivity if widespread |
| Dermatitis | 2% vs 1% | Non-specific; usually localised |
| Earache | 2% vs 1% | Not clearly drug-related |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Anaphylaxis (BOXED WARNING) | 0.1% in trials (3/3507); ≥0.2% post-marketing | 60–70% within first 3 doses; onset usually within 2 h; can occur >1 yr into treatment | Stop omalizumab permanently; treat with epinephrine per anaphylaxis protocol; report to manufacturer and FDA |
| Malignancy | 0.5% omalizumab vs 0.2% control in trials | Variable; most patients followed <1 yr | 5-year observational study showed similar rates (12.3 vs 13.0 per 1000 patient-years); causal link not established but cannot be ruled out |
| Serum sickness-like reaction (fever, arthritis, rash, lymphadenopathy) | Rare (post-marketing) | 1–5 days after injection; may recur | Discontinue omalizumab; treat symptomatically; do not rechallenge |
| Eosinophilic conditions / Churg-Strauss syndrome (EGPA) | Rare | Often with corticosteroid reduction | Check eosinophil count; evaluate for vasculitis; causal association not established |
| Cardiovascular / cerebrovascular events | Signal in observational study | Variable | FDA-labelled warning; confounding factors present; monitor in high-risk patients |
Patients with a history of anaphylaxis to foods, medications, or other causes are at increased risk of anaphylaxis to omalizumab (OR 8.1, 95% CI 2.7–24.3). Approximately 60–70% of anaphylaxis cases occur within the first three doses. All patients should carry epinephrine autoinjectors during omalizumab therapy.
Drug Interactions
No formal drug interaction studies have been conducted with omalizumab. As a monoclonal antibody metabolised by proteolytic degradation (not CYP enzymes), omalizumab has minimal pharmacokinetic interaction potential. The following clinical considerations are relevant:
Monitoring
- Serum Total IgEBefore treatment only
RoutineRequired for dose determination in asthma, CRSwNP, and food allergy (not CSU). Do NOT retest during treatment or within 1 year of stopping—levels are falsely elevated by omalizumab-IgE complexes. If treatment is interrupted ≥1 year, retest before restarting. - Post-Injection ObservationEvery administration (especially first 3 doses)
RoutineObserve in a healthcare setting for an appropriate period after injection. Anaphylaxis is most common within first 3 doses and usually occurs within 2 hours. Even after established therapy, vigilance is needed as late-onset anaphylaxis (>1 year) has been reported. - Asthma Control / Disease ResponseEvery 3–6 months
RoutinePeriodically reassess the need for continued therapy. Evaluate exacerbation frequency, rescue inhaler use, ICS dose, and quality of life. Most patients show response by 12–16 weeks. - Eosinophil CountIf vasculitis symptoms develop
Trigger-basedBe alert to new-onset eosinophilia, vasculitic rash, worsening pulmonary symptoms, cardiac complications, or neuropathy—especially during corticosteroid taper. These may indicate unmasking of Churg-Strauss syndrome. - Helminth Infection ScreeningBaseline and periodically in high-risk patients
Trigger-basedStool examination for ova and parasites in patients from endemic areas or with occupational exposure. Treat any active infection before starting omalizumab if feasible. - Body WeightEach visit
RoutineSignificant weight changes require dose recalculation for asthma, CRSwNP, and food allergy indications (clearance approximately doubles with doubling weight).
Contraindications & Cautions
Absolute Contraindications
- Severe hypersensitivity reaction to omalizumab or any ingredient of Xolair
Relative Contraindications (Specialist Input Recommended)
- History of anaphylaxis to foods, medications, or other causes — 8-fold increased risk of anaphylaxis to omalizumab; if prescribed, enhanced monitoring is essential
- Latex allergy — the needle cap of the 75 mg/0.5 mL and 150 mg/mL prefilled syringes contains a derivative of natural rubber latex (the autoinjector does not contain latex)
Use with Caution
- Patients at high risk of geohelminth infection — IgE is part of anti-parasitic immunity; monitor and treat infections promptly
- Concurrent oral corticosteroid taper — risk of unmasking eosinophilic conditions; taper gradually
- Pregnancy — insufficient human data; IgG crosses placenta; use only if clearly needed
- Children <6 yr (asthma) or <12 yr (CSU) — not approved for these age groups in these indications
- Elderly — limited data (134 patients ≥65 yr in trials); no apparent age-related differences observed
Anaphylaxis presenting as bronchospasm, hypotension, syncope, urticaria, and/or angioedema of the throat or tongue has been reported after omalizumab administration. Anaphylaxis has occurred as early as the first dose and beyond one year of treatment. In premarketing clinical trials, anaphylaxis was reported in 3 of 3,507 (0.1%) asthma patients. Post-marketing estimates suggest a rate of at least 0.2%. Approximately 60–70% of cases occurred within the first three doses. Initiate therapy only in a healthcare setting prepared to manage anaphylaxis. Patients selected for self-administration must meet specific criteria to mitigate anaphylaxis risk.
Patient Counselling
Purpose of Therapy
Omalizumab is a biologic injection that works by blocking IgE, a key chemical that triggers allergic reactions. Depending on your condition, it helps prevent asthma attacks, reduce hives, shrink nasal polyps, or reduce the severity of allergic reactions to accidentally eaten food allergens. It is not an emergency rescue medication and does not replace your rescue inhaler, antihistamines, or epinephrine autoinjector.
How to Take
Omalizumab is given as an injection under the skin, every 2 or 4 weeks depending on your condition and the results of a blood test for IgE. Your first few injections must be given in a clinic or doctor’s office where staff can watch you for any severe reaction. After that, your doctor may approve home self-injection if it is safe for you.
Sources
- Genentech, Inc. Xolair (omalizumab) prescribing information. Revised 02/2024. Genentech PIPrimary source for all indications, dosing tables (Tables 1–4), pharmacokinetics, adverse event incidence rates (Tables 7–10), boxed warning, and contraindications cited in this monograph.
- FDA. Omalizumab (marketed as Xolair) Information. FDA.govFDA safety communications including cardiovascular risk signal and label changes.
- FDA. Omlyclo (omalizumab-noli) biosimilar prescribing information. 2025. FDA LabelFirst FDA-approved biosimilar to omalizumab; confirms biosimilar adverse event and dosing profile.
- Humbert M, Beasley R, Ayres J, et al. Benefits of omalizumab as add-on therapy in patients with severe persistent asthma who are inadequately controlled despite best available therapy (GINA 2002 step 4 treatment): INNOVATE. Allergy. 2005;60(3):309–316. doi:10.1111/j.1398-9995.2004.00772.xPivotal INNOVATE trial demonstrating reduced exacerbations and emergency visits in severe allergic asthma with omalizumab add-on therapy.
- Maurer M, Rosén K, Hsieh HJ, et al. Omalizumab for the treatment of chronic idiopathic or spontaneous urticaria. N Engl J Med. 2013;368(10):924–935. doi:10.1056/NEJMoa1215372ASTERIA I trial establishing efficacy of omalizumab 300 mg q4wk for CSU refractory to antihistamines.
- Wood RA, Togias A, Sicherer SH, et al. Omalizumab for the treatment of multiple food allergies. N Engl J Med. 2024;390(10):889–899. doi:10.1056/NEJMoa2312382OUtMATCH trial supporting the Feb 2024 food allergy approval; demonstrated increased tolerance threshold in peanut and multi-food allergic patients.
- Gevaert P, Omachi TA, Corren J, et al. Efficacy and safety of omalizumab in nasal polyposis: 2 randomized phase 3 trials. J Allergy Clin Immunol. 2020;146(3):595–605. doi:10.1016/j.jaci.2020.05.032POLYP 1 and POLYP 2 trials forming the basis for the CRSwNP indication approval.
- Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention. 2024 Update. ginasthma.orgPositions omalizumab as a Step 5 add-on biologic for severe allergic asthma with elevated IgE.
- Zuberbier T, Abdul Latiff AH, Abuzakouk M, et al. The international EAACI/GA2LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria. Allergy. 2022;77(3):734–766. doi:10.1111/all.15090International guideline recommending omalizumab as second-line therapy for CSU unresponsive to updosed H1 antihistamines.
- Holgate ST, Djukanović R, Casale T, Bousquet J. Anti-immunoglobulin E treatment with omalizumab in allergic diseases: an update on anti-inflammatory activity and clinical efficacy. Clin Exp Allergy. 2005;35(4):408–416. doi:10.1111/j.1365-2222.2005.02191.xComprehensive review of omalizumab’s mechanism including IgE binding, FcεRI downregulation, and anti-inflammatory effects.
- Lowe PJ, Tannenbaum S, Gautier A, Jimenez P. Relationship between omalizumab pharmacokinetics, IgE pharmacodynamics and symptoms in patients with severe persistent allergic (IgE-mediated) asthma. Br J Clin Pharmacol. 2009;68(1):61–76. doi:10.1111/j.1365-2125.2009.03401.xPopulation PK/PD model confirming the IgE/weight-based dosing strategy and relationship between free IgE suppression and clinical outcomes.
- StatPearls: Omalizumab. Singh AP, Neely JA. In: StatPearls [Internet]. Updated Aug 17, 2023. NCBI BookshelfClinical review covering pharmacokinetics (bioavailability 62%, t½ 24–26 days), special populations, and current indications.
- Kim HL, Leigh R, Becker A. Omalizumab: practical considerations regarding the risk of anaphylaxis. Allergy Asthma Clin Immunol. 2010;6(1):32. doi:10.1186/1710-1492-6-32Practical guidance on anaphylaxis risk assessment, monitoring protocols, and patient selection for self-administration.