Omalizumab

Pharmacodynamics: Targeted Effect on Immunity

Omalizumab (known under the brand name Xolair) represents recombinant humanized monoclonal antibodies. This is a classic example of targeted therapy aimed at specifically affecting the immunological link in the pathogenesis of allergic reactions. The main and only target of this drug is immunoglobulin E (IgE).

The mechanism of action of the drug is implemented in two stages and includes primary and secondary pharmacological effects.

Primary mechanism of action is based on the selective binding of the drug molecule to free human IgE circulating in blood plasma. Forming a stable complex, the drug rapidly reduces the amount of free IgE.

The consequences of this binding include:

1. A sharp decrease in the number of IgE molecules capable of attaching to high-affinity receptors (known as $Fc\epsilon RI$) on the surface of mast cell membranes.
2. Interruption of the sensitization process and subsequent mast cell activation.
3. A predictable decrease in the massive release of allergy mediators (primarily histamine and other biologically active substances).

Secondary (long-term) effect manifests with regular and prolonged use of antibodies. It consists in the development of the down-regulation phenomenon: the organism adapts to low levels of free IgE, which leads to a decrease in the number of $Fc\epsilon RI$ receptors themselves on mast cell membranes. Additionally, as a long-term consequence, the further synthesis of new IgE molecules by B-lymphocytes decreases.

Specificity, Safety, and Clinical Effects

The key pharmacological feature of omalizumab, which determines its safety profile, is its strict selectivity. The drug binds exclusively to free IgE in blood plasma and does not interact at all with immunoglobulin E already fixed on the surface of mast cells.

The consequence of such high specificity is that the drug molecules do not cause cross-linking (agglutination) of mast cells. This prevents their degranulation in response to drug administration. Thus, the risk of provoking an allergic attack by the drug itself is excluded.

In clinical practice, the use of anti-IgE therapy provides the following significant effects:

• A reliable reduction in the frequency and severity of bronchial asthma attacks.
• Restoration of glucocorticoid sensitivity. This is a critically important aspect of treatment that helps overcome the development of resistance to inhaled hormonal drugs and regain control over severe disease progression.

Indications, Dosage, and Side Effects

In modern pharmacotherapy, omalizumab is considered a second-line drug. Its main clinical indication is bronchial asthma that has proved resistant (refractory) to traditional baseline therapy.

Dosage regimen and routes of administration:

• Route of administration: the drug is administered predominantly subcutaneously, although intravenous use is also described in clinical practice.
• Dosage: a single dose ranges between 150–375 mg.
• Frequency: injections are administered once every 2–4 weeks to maintain stable suppression of free IgE.

Side effects: Despite the targeted mechanism of action, monoclonal antibody therapy may be accompanied by a number of adverse reactions, which are divided into three groups:

1. Infectious complications: against the background of the immunomodulatory effect, patients more often encounter upper respiratory tract infections (predominantly of viral origin).
2. Local reactions: transient pain, skin redness, and local itching may occur directly at the injection site.
3. General reactions: systemic manifestations include headache and the risk of allergic reactions to the administration of the recombinant protein.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Structure and functions of high-affinity FcεRI receptors
• Mechanisms of mast cell degranulation and histamine release
• Synthesis of class E immunoglobulins (IgE) by B-lymphocytes
• Causes of resistance to inhaled glucocorticoids
• Differences between targeted therapy and traditional asthma treatment methods

Other topics in the section 'Drugs acting on respiratory system functions'

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