Epistemis

Biologicals Anti-IL5 (Mepolizumab, Reslizumab), Anti-IL5R$\alpha$ (Benralizumab) and Anti-IL4R$\alpha$ (Dupilumab)

  • Directed Biological Therapies (Part II)

Second-generation monoclonal antibodies in severe asthma are directed ultra-specifically against the effector cytokines of the Th2 or eosinophilic inflammatory phenotype, achieving persistent clinical remissions without steroid effects.

Mechanism

🩸 Mepolizumab / Reslizumab
  • Class: Humanized monoclonal antibodies IgG1 and IgG4.
  • Molecular Target: They bind directly to the circulating soluble cytokine IL-5.
  • They prevent the binding of IL-5 to the α subunit of its receptor on the membrane of eosinophils.
🧬 Benralizumab
  • Class: High-affinity afucosylated humanized IgG1 antibody.
  • Molecular Target: Binds directly to the α subunit of the IL-5 receptor (IL-5Rα).
  • Induces immediate destruction of eosinophils mediated by NK cells (ADCC cellular cytotoxicity).

Molecular mechanisms of action

Mepolizumab and Reslizumab: Interleukin 5 is the main cytokine involved in the growth, differentiation, recruitment, activation and tissue survival of eosinophils. By selectively sequestering soluble IL-5, these drugs block its biological signal transduction through the cellular JAK-STAT pathway, drastically decreasing tissue eosinophilia in the airway.

Benralizumab: Its molecular target is the cellular IL-5Rα receptor. Additionally, it has a critical structural modification in its constant fraction (Fc): it lacks fructose sugars (afucosylation).

Indicators and dose

Approved clinical indications

  • Severe persistent eosinophilic asthma: In patients with frequent exacerbations who have high peripheral blood eosinophil counts (typically 150 or 300 cells/µL).
  • Dupilumab (Additional indications): Moderate to severe atopic dermatitis, chronic rhinosinusitis with severe nasal polyposis and refractory eosinophilic esophagitis.

Pharmacokinetics and Administration Intervals

Drug Via Standard Adult Dose Frequency Half-life (t1/2)
Mepolizumab SC 100 mg (injectable solution) Every 4 weeks ~16 - 22 days
Reslizumab IV 3 mg/kg (adjusted by body weight) Every 4 weeks ~24 days
Benralizumab SC 30 mg Every 4 weeks (first 3 doses) and then every 8 weeks ~15.5 days
Dupilumab SC 200 mg or 300 mg (after loading dose of 400/600 mg) Every 2 weeks ~14 days

Security

Benralizumab-Induced Cellular Cytotoxicity (ADCC)

The afucosylated structure of benralizumab gives it up to 50 times greater affinity for the immune activation receptor FcγRIIIa exposed on the surface of natural killer (NK) cells. By simultaneously binding to the eosinophil receptor (IL-5Rα) and the NK cell receptor, it acts as a molecular bridge that activates the immediate release of granzyme and perforin granules by the NK cell. This causes apoptosis and subsequent cellular clearance of local and systemic eosinophils within 24 hours after the first injection.

Dupilumab: It is a human IgG4 monoclonal antibody directed against the α subunit of the interleukin 4 receptor (IL-4Rα). This subunit is part of a heterodimeric receptor shared by IL-4 and IL-13 (the Type I and Type II receptors).

By blocking the IL-4Rα subunit, dupilumab simultaneously interrupts the molecular signaling of both cytokines. This inhibits the Type 2 immune inflammatory cascade, significantly reducing:

  • The differentiation of naïve T lymphocytes towards the Th2 phenotype.
  • The production of immunoglobulin E (IgE) by epithelial B cells.
  • The secretion of chemokines that recruit eosinophils (such as eotaxin-3) and the abnormal clearance of mucus.

Adverse effects (ADRs)

  • Common (All): Headache, skin reactions at the injection site, arthralgia and mild pharyngitis.
  • Specific to Dupilumab: Transient allergic or bacterial conjunctivitis (of unknown cause, occurs in ≈ 10% of patients with atopic dermatitis but is less common in asthmatic patients), and transient peripheral eosinophilia due to sequestration of the extravasation of circulating eosinophils.

Epistemis is educational review material. It is not a medical device, does not diagnose or prescribe treatment, and does not replace formal medical training, current clinical guidelines, or professional clinical judgment.

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