Omalizumab

• Allergic Asthma
• Chronic Spontaneous Urticaria
• Chronic Rhinosinusitis with Nasal Polyps

Omalizumab is a humanized monoclonal antibody that targets immunoglobulin E (IgE), making it effective for moderate-to-severe allergic asthma and chronic spontaneous urticaria. As the first anti-IgE therapy approved, it represents a breakthrough in treating allergic diseases.

Mechanism of Action

Omalizumab works by:

• Binding to free IgE in the blood and interstitial fluid
• Preventing IgE from attaching to high-affinity IgE receptors (FcεRI) on mast cells and basophils
• Reducing surface-bound IgE on mast cells and basophils
• Decreasing FcεRI receptor expression over time
• Reducing release of allergic mediators (histamine, leukotrienes, prostaglandins)

This cascade of effects results in decreased allergic inflammation and clinical improvement.

Available Formulations

Omalizumab is available as:

• Prefilled syringe: 75 mg/0.5 mL, 150 mg/mL
• Lyophilized powder for reconstitution: 150 mg vial

Administered subcutaneously, either in healthcare settings or at home after training.

Medical Uses

FDA-Approved Indications:

• Moderate-to-severe persistent allergic asthma in patients ≥6 years with positive skin test or in vitro reactivity to perennial aeroallergens inadequately controlled with inhaled corticosteroids
• Chronic spontaneous urticaria (chronic idiopathic urticaria) in adults and adolescents ≥12 years who remain symptomatic despite H1 antihistamine treatment
• Chronic rhinosinusitis with nasal polyps in adults inadequately controlled with intranasal corticosteroids

Dosing Guidelines

Allergic Asthma:

• Dose based on pretreatment serum total IgE level and body weight
• Range: 75-375 mg every 2-4 weeks
• Maximum: 375 mg every 2 weeks
• Consult dosing tables in prescribing information

Chronic Spontaneous Urticaria:

• 150 mg or 300 mg subcutaneously every 4 weeks
• Dosing not dependent on IgE level or body weight
• Assess response periodically; discontinue if no improvement after 6 months

Chronic Rhinosinusitis with Nasal Polyps:

• Dose based on IgE level and body weight (same as asthma dosing)

Important Safety Information

Black Box Warning:

• Anaphylaxis can occur with any dose, even after years of treatment
• Observe patients for appropriate time after each injection
• Be prepared to treat anaphylaxis
• Patients should carry autoinjectable epinephrine

Contraindications:

• Severe hypersensitivity reaction to omalizumab

Warnings and Precautions:

• Anaphylaxis: Occurs in 0.1-0.2% of patients
• Malignancy: Slightly higher rates observed in clinical trials (unclear if related)
• Helminth infections: May increase infection risk
• Fever, arthralgia, rash (serum sickness-like reactions)
• Do not use for acute asthma exacerbations

Drug Interactions

No formal drug interaction studies conducted. As a biologic, omalizumab is not metabolized by cytochrome P450 enzymes.

• Immunosuppressants: Theoretical concern for additive immunosuppression
• Allergen immunotherapy: Can be used concurrently

Special Populations

• Pregnancy: Limited data; use only if benefit outweighs risk
• Lactation: Unknown if excreted in milk
• Pediatric: Approved for asthma in children ≥6 years; urticaria in ≥12 years
• Elderly: No dose adjustment; use with caution