Accession Number

Omalizumab, manufactured by Genentech, was first FDA approved in 2003 to treat adults and children 12 years of age and older with moderate to severe persistent allergic asthma which is not controlled by inhaled steroids 6. Since its U.S. approval, more than 200,000 patients older than 12 with allergic asthma have been treated 6. In September 2018, a new prefilled syringe formulation of this drug was approved by the FDA 7.

Approved, Investigational
Biologic Classification
Protein Based Therapies
Monoclonal antibody (mAb)
Protein Structure
Protein Chemical Formula
Protein Average Weight
149000.0 Da
>Omalizumab heavy chain
>Omalizumab light chain
Download FASTA Format
Not Available



This drug is an anti-IgE antibody indicated for:

  1. Moderate to severe persistent asthma in patients 6 years of age and older with a positive skin test or in vitro reactivity to a perennial aeroallergen and symptoms that are inadequately controlled with inhaled corticosteroids Label

  2. Chronic idiopathic urticaria in adults and adolescents 12 years of age and older who remain symptomatic despite H1 antihistamine treatment Label

Associated Conditions
Contraindications & Blackbox Warnings
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Omalizumab is a recombinant, humanized, monoclonal antibody against human immunoglobulin E (IgE) which treats the symptoms of asthma and chronic idiopathic urticaria by limiting the allergic response Label, 3. It inhibits the binding of IgE to receptors on mast cells and basophils, blocking the IgE-mediated secretion of inflammatory mediators from these cells 1.

Mast cell activation and the release of mediators, in response to allergen exposure and IgE, results in a cascade of events. This cascade culminates in the activation of B-lymphocytes, T-lymphocytes, eosinophils, fibroblasts, smooth muscle cells, and the endothelium. This cellular interaction, as well as the release of cytokines, chemokines and growth factors and inflammatory remodeling of the airway results in chronic asthma 2.

After 4 weeks of use of this medication in patients with chronic urticaria, it was found that rescue medication use was reduced significantly and quality of life improved 4.

Mechanism of action

When an environmental allergen first enters the body, is taken up by antigen-presenting cells (APCs). It is then processed, and presented to T and B immune cells. This is followed by the activation of B-lymphocyte and production of allergen-specific IgE. This IgE is then released by plasma cells (converted B lymphocytes) and is therefore available to bind to IgE receptors on several other cells 3.

IgE binds to high-affinity (Fc€RI) and low-affinity (Fc€RII) receptors on multiple cells of the immune system. Following subsequent antigen exposure, cross-linking of the antigen occurs by several Fc€RI-bound IgE molecules on the surface of both basophils and mast cells. This leads to the activation of mast cells and histamine release, producing a wheal and other symptoms of urticaria 3.

The following are explanations of the mechanism of action for both indications of this drug:


Omalizumab inhibits the binding of IgE to the high-affinity IgE receptor (FcεRI) on the surface of both mast cells and basophils. The reduction in surface-bound IgE on FcεRI-bearing cells limits the degree of release of mediators of the typical allergic response. Treatment with omalizumab also reduces the number of FcεRI receptors on basophils in atopic patients Label.

Omalizumab binds to free IgE with a higher affinity than IgE itself binds to the high-affinity Fc€RI receptors found on basophils. Therefore, it decreases the availability of free IgE for binding 3. Omalizumab by itself does not bind to the Fc€RI receptors, nor does the drug bind to receptor-bound IgE. These binding characteristics allow omalizumab to neutralize the typical IgE-mediated responses without causing the degranulation of basophils or cross-linking with basophil-bound IgE 3.

Chronic Idiopathic Urticaria Omalizumab binds to IgE and decreases free IgE levels. Subsequently, IgE receptors (FcεRI) on cells are down-regulated. The mechanism by which these effects of omalizumab result in an improvement of CIU symptoms is unclearLabel.

AHigh affinity immunoglobulin epsilon receptor subunit alpha
AHigh affinity immunoglobulin epsilon receptor subunit beta

After subcutaneous administration in pharmacokinetic studies, omalizumab was absorbed with a mean absolute bioavailability of 62% Label. After the administration of a single subcutanous dose in adult and adolescent patients with asthma, omalizumab was absorbed slowly. The peak serum concentrations peaked after an average of 7­-8 days. In patients with CIU, the peak serum concentration was reached at a similar time after a single SC dose. The pharmacokinetics of omalizumab was linear at doses which were higher than 0.5 mg/kg. In patients with asthma, after several doses of omalizumab, areas under the serum concentration-time curve from Day 0 to Day 14 at steady state were up to 6-fold of those after one dose. In patients with CIU, omalizumab showed linear pharmacokinetics in the dose range of 75 mg to 600 mg administered as a single subcutaneous dose. After repeated dosing from 75mg-300 mg every 4 weeks, trough serum concentrations of omalizumab increased proportionally with the dose Label.

Volume of distribution

The apparent volume of distribution of omalizumab in patients with asthma after subcutaneous administration was 78 ± 32 mL/kg. In patients with CIU, the distribution of omalizumab was similar to that in asthmatic patients Label.

Protein binding

Monoclonal antibodies are usually not required to have protein binding studies.


Monoclonal antibodies, in general, are believed to be internalized in endothelial cells bound to the Fc receptor and rescued from metabolism by recycling. At a later time, they are degraded in the reticuloendothelial system to smaller peptides and amino acids, which can then be used for de-novo protein synthesis 5. Several factors may influence this process, however. These include factors related to the target antigen, antibody, and patient 5.

The metabolism of omalizumab is determined by its IgG1 framework, and by its specific binding to IgE. The elimination of omalizumab is dose-dependent. The reticuloendothelial system and the liver are two sites of elimination for IgG (including degradation in the liver reticuloendothelial system and endothelial cells) 9, 5. The omalizumab:IgE complexes are thought to be to cleared via interactions with Fc- gamma-Rs (Fc gamma RI, Fc gamma RII, and Fc gamma RIII) at rates that are more rapid than that of IgG clearance. The relative clearance of free omalizumab, free IgE, and complexes is summarized as: free IgE clearance > > omalizumab:IgE clearance > omalizumab clearance 9.

Route of elimination

Liver elimination of IgG includes degradation in the liver reticuloendothelial system (RES) and endothelial cells. Intact IgG was also shown to be excreted in bile, in pharmacokinetic studies Label.


In chronic idiopathic urticaria (CIU) patients, at steady state, based on population pharmacokinetics, omalizumab serum elimination half-life averaged 24 days Label.

In asthmatic patients omalizumab serum elimination half-life averaged 26 days Label.


In pharmacokinetic studies, the clearance of omalizumab involved IgG clearance as well as clearance by specific binding and complex formation with its target ligand, IgE Label, 9.

The apparent clearance averaging 2.4 ± 1.1 mL/kg/day was measured in asthmatic patients Label.

In chronic idiopathic urticaria (CIU) patients, at steady state, based on population pharmacokinetics, omalizumab apparent clearance averaged 240 mL/day (corresponding to 3.0 mL/kg/day for an 80 kg patient)Label.

Adverse Effects
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Anaphylaxis may occur rarely with this agent, either after the first dose or multiple doses Label, 2. Anaphylaxis presenting clinically as bronchospasm, hypotension, syncope, urticaria, and/or angioedema of the throat or tongue, has been reported during and after this use of this drug. Therefore, close clinical monitoring should be performed during and shortly after administration Label.

Maximum Dosage

The maximum tolerated dosage of omalizumab has not yet been determined. Single intravenous (IV) doses of up to 4000 mg have been administered to patients without evidence of dose-limiting toxicity. The highest cumulative dose administered to patients was 44,000 mg over a 20 week time period, which was not associated with any toxicities Label.

The use in Pregnancy

The data with omalizumab use in pregnant women are insufficient to inform on drug-associated risk. Monoclonal antibodies, such as omalizumab, are transported across the placenta in a linear fashion as a pregnancy progresses; therefore, potential effects on a fetus are likely to be greater in frequency during the second and third trimesters Label.

In women with inadequately or moderately controlled asthma, the current evidence suggests that there is an increased risk of preeclampsia in the mother and prematurity, low birth weight, and small fetal size Label.

The use During Breastfeeding

There is no information regarding the presence of omalizumab in human milk, the effects on the breastfed infant, or the effects on milk production Label. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for omalizumab and any potential adverse effects on the breastfed child from omalizumab or from the underlying maternal condition Label.

Affected organisms
  • Humans and other mammals
Not Available
Pharmacogenomic Effects/ADRs
Not Available


Drug Interactions
This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
AbciximabThe risk or severity of adverse effects can be increased when Omalizumab is combined with Abciximab.
AdalimumabThe risk or severity of adverse effects can be increased when Omalizumab is combined with Adalimumab.
AlemtuzumabThe risk or severity of adverse effects can be increased when Omalizumab is combined with Alemtuzumab.
AlirocumabThe risk or severity of adverse effects can be increased when Omalizumab is combined with Alirocumab.
Anthrax immune globulin humanThe risk or severity of adverse effects can be increased when Omalizumab is combined with Anthrax immune globulin human.
Antilymphocyte immunoglobulin (horse)The risk or severity of adverse effects can be increased when Omalizumab is combined with Antilymphocyte immunoglobulin (horse).
Antithymocyte immunoglobulin (rabbit)The risk or severity of adverse effects can be increased when Omalizumab is combined with Antithymocyte immunoglobulin (rabbit).
Asfotase alfaThe risk or severity of adverse effects can be increased when Omalizumab is combined with Asfotase alfa.
AtezolizumabThe risk or severity of adverse effects can be increased when Omalizumab is combined with Atezolizumab.
AtoltivimabThe risk or severity of adverse effects can be increased when Omalizumab is combined with Atoltivimab.
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Food Interactions
Not Available


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Brand Name Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
XolairSolution75 mgSubcutaneousNovartis2017-06-28Not applicableCanada flag
XolairPowder, for solution150 mgSubcutaneousNovartis2005-02-03Not applicableCanada flag
XolairInjection, solution202.5 mg/1.4mLSubcutaneousGenentech, Inc.2003-06-20Not applicableUS flag
XolairSolution150 mgSubcutaneousNovartis2017-07-06Not applicableCanada flag
Xolair PFSInjection, solution150 mg/1mLSubcutaneousGenentech, Inc.2018-09-28Not applicableUS flag
Xolair PFSInjection, solution75 mg/0.5mLSubcutaneousGenentech, Inc.2018-09-28Not applicableUS flag
Additional Data Available
  • Application Number
    Application Number
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    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code
    Product Code
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    A governmentally-recognized ID which uniquely identifies the product within its regulatory market.

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ATC Codes
R03DX05 — Omalizumab
Drug Categories
Chemical TaxonomyProvided by Classyfire
Not Available
Organic Compounds
Super Class
Organic Acids
Carboxylic Acids and Derivatives
Sub Class
Amino Acids, Peptides, and Analogues
Direct Parent
Alternative Parents
Not Available
Not Available
Molecular Framework
Not Available
External Descriptors
Not Available

Chemical Identifiers

CAS number


General References
  1. Jensen RK, Plum M, Tjerrild L, Jakob T, Spillner E, Andersen GR: Structure of the omalizumab Fab. Acta Crystallogr F Struct Biol Commun. 2015 Apr;71(Pt 4):419-26. doi: 10.1107/S2053230X15004100. Epub 2015 Mar 20. [PubMed:25849503]
  2. Miller CW, Krishnaswamy N, Johnston C, Krishnaswamy G: Severe asthma and the omalizumab option. Clin Mol Allergy. 2008 May 20;6:4. doi: 10.1186/1476-7961-6-4. [PubMed:18489791]
  3. Godse K, Mehta A, Patil S, Gautam M, Nadkarni N: Omalizumab-A Review. Indian J Dermatol. 2015 Jul-Aug;60(4):381-4. doi: 10.4103/0019-5154.160490. [PubMed:26288408]
  4. Kaplan AP, Joseph K, Maykut RJ, Geba GP, Zeldin RK: Treatment of chronic autoimmune urticaria with omalizumab. J Allergy Clin Immunol. 2008 Sep;122(3):569-73. doi: 10.1016/j.jaci.2008.07.006. [PubMed:18774392]
  5. Tabrizi MA, Tseng CM, Roskos LK: Elimination mechanisms of therapeutic monoclonal antibodies. Drug Discov Today. 2006 Jan;11(1-2):81-8. doi: 10.1016/S1359-6446(05)03638-X. [PubMed:16478695]
  6. FDA Approves Genentech’s Xolair® (omalizumab) for Allergic Asthma in Children [Link]
  7. FDA Approves Genentech's Xolair (omalizumab) Prefilled Syringe Formulation [Link]
  8. Omalizumab properties, THPdb Database [Link]
  9. Xolair EMA label [File]
PubChem Substance
Therapeutic Targets Database
RxList Drug Page Drug Page
AHFS Codes
  • 48:92.00 — Respiratory Agents, Miscellaneous
Download (582 KB)

Clinical Trials

Clinical Trials
4CompletedNot AvailableAtopic Dermatitis (AD)1
4CompletedBasic ScienceAsthma1
4CompletedDiagnosticAsthma, Allergic1
4CompletedTreatmentAllergic Rhinitis (AR) / Asthma / Atopic Dermatitis (AD)1
4CompletedTreatmentAspirin Sensitivity1
4CompletedTreatmentAsthma, Allergic4
4CompletedTreatmentAtopic Dermatitis (AD) / Children1
4CompletedTreatmentBullous Pemphigoid (BP)1
4CompletedTreatmentChonic Spontaneous Urticaria1


Not Available
  • Genentech Inc.
  • Novartis AG
Dosage Forms
InjectionSubcutaneous150 MG
Injection, powder, for solution
Injection, powder, for solution150 mg
Injection, powder, for solutionCutaneous150 MG
Injection, powder, for solutionCutaneous75 MG
Injection, solutionCutaneous; Parenteral150 MG
Injection, solutionCutaneous; Parenteral75 MG
Injection, solutionSubcutaneous202.5 mg/1.4mL
Powder, for solutionSubcutaneous150 mg
Injection, powder, for solutionSubcutaneous150 mg
SolutionSubcutaneous150 mg
SolutionSubcutaneous75 mg
Injection, solutionSubcutaneous150 mg
InjectionSubcutaneous150 mg/ml
InjectionSubcutaneous75 mg/0.5ml
Injection, solutionSubcutaneous150 mg/1mL
Injection, solutionSubcutaneous75 mg/0.5mL
Unit descriptionCostUnit
Xolair 150 mg vial715.42USD vial
DrugBank does not sell nor buy drugs. Pricing information is supplied for informational purposes only.
Patent NumberPediatric ExtensionApprovedExpires (estimated)Region
CA2113813No2005-04-122012-08-14Canada flag
CA1340233No1998-12-152015-12-15Canada flag
Additional Data Available
  • Filed On
    Filed On
    Available for Purchase

    The date on which a patent was filed with the relevant government.

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Experimental Properties
melting point (°C)61 °C (FAB fragment)
boiling point (°C)Fab and Fc domains denaturates at 60 and 70 ºC respectivelyArnoldus W. et al. (2000). Biophysical Journal. Vol 78. 394-404
hydrophobicity-0.432Not Available
isoelectric point6.6 - 7.2Jin, et al. Electrophoresis. Sep;23(19):3385-91. (2002).


Pharmacological action
General Function
Ige receptor activity
Specific Function
Binds to the Fc region of immunoglobulins epsilon. High affinity receptor. Responsible for initiating the allergic response. Binding of allergen to receptor-bound IgE leads to cell activation and t...
Gene Name
Uniprot ID
Uniprot Name
High affinity immunoglobulin epsilon receptor subunit alpha
Molecular Weight
29595.67 Da
  1. Beck LA, Marcotte GV, MacGlashan D, Togias A, Saini S: Omalizumab-induced reductions in mast cell Fce psilon RI expression and function. J Allergy Clin Immunol. 2004 Sep;114(3):527-30. [PubMed:15356552]
  2. Mirkina I, Schweighoffer T, Kricek F: Inhibition of human cord blood-derived mast cell responses by anti-Fc epsilon RI mAb 15/1 versus anti-IgE Omalizumab. Immunol Lett. 2007 Apr 15;109(2):120-8. Epub 2007 Mar 1. [PubMed:17368811]
  3. Godse K, Mehta A, Patil S, Gautam M, Nadkarni N: Omalizumab-A Review. Indian J Dermatol. 2015 Jul-Aug;60(4):381-4. doi: 10.4103/0019-5154.160490. [PubMed:26288408]
Pharmacological action
General Function
Ige receptor activity
Specific Function
High affinity receptor that binds to the Fc region of immunoglobulins epsilon. Aggregation of FCER1 by multivalent antigens is required for the full mast cell response, including the release of pre...
Gene Name
Uniprot ID
Uniprot Name
High affinity immunoglobulin epsilon receptor subunit beta
Molecular Weight
26533.365 Da
  1. Overington JP, Al-Lazikani B, Hopkins AL: How many drug targets are there? Nat Rev Drug Discov. 2006 Dec;5(12):993-6. [PubMed:17139284]
  2. Imming P, Sinning C, Meyer A: Drugs, their targets and the nature and number of drug targets. Nat Rev Drug Discov. 2006 Oct;5(10):821-34. [PubMed:17016423]
  3. DuBuske LM: IgE, allergic diseases, and omalizumab. Curr Pharm Des. 2006;12(30):3929-44. [PubMed:17073688]
  4. Raunio H, Rautio A, Gullsten H, Pelkonen O: Polymorphisms of CYP2A6 and its practical consequences. Br J Clin Pharmacol. 2001 Oct;52(4):357-63. [PubMed:11678779]

Drug created on June 13, 2005 07:24 / Updated on November 23, 2020 09:08

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