Dupilumab

Mechanism

Pharmacological Class and Group

Fully human recombinant IgG4 monoclonal antibody directed against the IL-4Rα subunit.

Mechanism of Action

Severe atopic dermatitis is characterized immunologically by a deviation and pathological activation of the immune response of the Th2 pathway, with local hyperproduction of the key inflammatory cytokines Interleukin-4 (IL-4) and Interleukin-13 (IL-13). These cytokines directly damage the synthesis of filaggrin and loricrin in keratinocytes, breaking the protective function of the epidermal barrier and stimulating chronic itch by activating sensory itch receptors.

Dual Blocking Mechanism for IL-4 and IL-13 Signaling

1. Selective Binding to the Receptor Alpha Subunit (IL-4Rα): Dupilumab selectively and specifically binds to the soluble and membrane-bound subunit of the IL-4Rα receptor.

2. Blocking receptor heterodimerization: Docking physically prevents the formation of Type I (IL-4Rα / common γ chain) and Type II (IL-4Rα / IL-13Rα1) active receptor complexes:

Dupilumab IL-4Rα STAT6 Cascade Blockade ↓ IgE Synthesis and Eosinophil Infiltration

3. Stopping the Th2 Immune Cascade: By simultaneously blocking the common pathway, the phosphorylation of the tyrosine kinases JAK1 and Tyk2 is stopped, interrupting the nuclear translocation of the transcription factor STAT6. This dramatically suppresses cutaneous recruitment of eosinophils, decreases the expression of lymphocyte-attracting chemokines (TARC/CCL17), and decreases circulating levels of immunoglobulin E (IgE).

Pharmacokinetics

High Resolution Pharmacokinetics

• Routes and Bioavailability: Exclusively subcutaneous (SC) administration. Absolute bioavailability of 64% after initial loading dose, reaching stable concentrations in plasma after 4-6 weeks.
• Distribution: Low tissue distribution volume of approximately 0.05-0.08 L/kg, preferentially confined to the dermis and local lymphatic tissues.
• Metabolism: Non-linear clearance mediated primarily by the internalization and cellular degradation of the antibody after saturating the binding with the target subunit IL-4Rα.
• Half-life (t_1/2): Biological elimination half-life dependent on receptor saturation, estimated between 1 and 4 weeks depending on the patient's body weight and administered dose.

Indicators and dose

Clinical Indications and Off-Label Uses

• Moderate to Severe Atopic Dermatitis: Indicated in adults, adolescents and pediatric patients over 6 months of age who are candidates for systemic therapy due to lack of adequate control with local corticosteroids.
• Nodular Pruritus (Hyde's): Recently approved, achieving a reduction in chronic destructive pruritus and a reduction in nodular keratotic lesions on the body.
• Th2 type / Severe Eosinophilic Asthma and Chronic Rhinosinusitis with Nasal Polyposis: Priority clinical co-indications.
• Eosinophilic Esophagitis: Control of esophageal inflammatory infiltration.

Dosage and Clinical Adjustment

Moderate to Severe Atopic Dermatitis (Adults):

• Initial Loading Dose (Day 1): 600 mg subcutaneously (administered via two consecutive 300 mg syringes or autoinjectors at separate anatomic sites).
• Maintenance Dose: 300 mg subcutaneously administered once every two weeks (starting 14 days after the loading dose).

Adjustment in Renal/Hepatic Insufficiency: No dose adjustment is required in patients with renal or hepatic insufficiency, since biological proteins are not eliminated by direct glomerular filtration nor do they undergo CYP450 enzymatic hepatic degradation.

Security

Absolute and Relative Contraindications

Absolute Contraindications

• Known severe hypersensitivity to dupilumab or excipients of the liquid formulation.

Relative Contraindications

• Active parasitic infections due to helminths (the Th2 pathway is responsible for the host's defense against parasites; it is suggested to eradicate the worm infection before starting).

Adverse Effects (ADR) and Specific Toxicity

• Very common (>10%): Reactions of erythema or transient pain at the subcutaneous injection site, benign nasopharyngitis.
• Frequent (1%-10%): Mild localized cold sores, punctate superficial corneal keratitis, Non-infectious conjunctivitis (characterized by conjunctival hyperemia, ocular pruritus, lacrimation and dryness, of paradoxical origin related to the blockage of the differentiation of mucin-producing goblet cells in the conjunctiva facilitated by depletion of the IL-4Rα receptor).
• Rare (<0.1%): Severe generalized hypersensitivity reactions (anaphylaxis), paradoxically induced alopecia areata.

Drug Interactions of Clinical Relevance

• Live Attenuated Vaccines: Avoid concomitant administration of live virus vaccines during the course of biological treatment.
• No hepatic clearance interactions mediated by CYP450 cytochromes are described.

Safety in Pregnancy and Breastfeeding

• Pregnancy: Compatible with precautions. Being a recombinant IgG4, it does not cross the placenta in a clinically significant way during the first trimester, but its active transport increases as gestation progresses. No direct embryotoxic effects or teratogenicity have been reported in observational registry epidemiological studies.
• Breastfeeding: Compatible. It is excreted at minimal, non-measurable levels and is harmlessly degraded in the infant's digestive tract.

Clinical

Perla Clínica: Management of Conjunctivitis due to Dupilumab

Dupilumab-associated conjunctivitis occurs in approximately 10-20% of patients treated for atopic dermatitis (interestingly, it is very rare in patients treated for asthma or polyposis). It is associated with the temporary decrease in conjunctival protective mucus. Dupilumab should not be suspended when faced with this symptom:

• First Line Management: Lubricating artificial tears without preservatives applied 4 to 6 times a day, accompanied by eye drops of Fluorometholone or ophthalmic Dexamethasone at low doses for 7-10 days under strict ophthalmological monitoring.
• Alternatives: In recalcitrant cases, the topical ophthalmic eye drops of tacrolimus 0.03% prepared in a masterful way offers high resolving efficacy.