Mepsevii (Vestronidase Alfa)

Mepsevii provides enzyme replacement therapy for the lysosomal storage disorder mucopolysaccharidosis type VII.

• Mucopolysaccharidosis type VII (Sly syndrome): reduces glycosaminoglycan storage in tissues.
• Mucopolysaccharidosis type VII (Sly syndrome): improves organ function and growth parameters.
• Mucopolysaccharidosis type VII (Sly syndrome): decreases progression of skeletal abnormalities.

• Vestronidase alfa is a recombinant human beta‑glucuronidase that replaces the deficient lysosomal enzyme in patients with MPS VII. After intravenous infusion, the enzyme is taken up by cells via mannose‑6‑phosphate receptors and delivered to lysosomes, where it hydrolyzes accumulated glycosaminoglycans, thereby reducing substrate storage and mitigating disease pathology. The restored enzymatic activity normalizes cellular turnover of dermatan and chondroitin sulfates.

Mepsevii may be associated with infusion‑related reactions and other adverse events.

Common Side Effects

• Fever: transient elevation of body temperature during or after infusion.
• Chills: shaking sensation commonly reported.
• Rash: mild skin erythema at infusion site.
• Headache: mild to moderate intensity.
• Nausea: occasional upset stomach.

Serious or Rare Side Effects

• Anaphylaxis: severe allergic reaction requiring immediate medical attention.
• Hypotension: significant drop in blood pressure during infusion.
• Elevated liver enzymes: increase in ALT/AST indicating hepatic stress.
• Antibody formation: development of anti‑drug antibodies that may reduce efficacy.

Before initiating Mepsevii therapy, clinicians should consider several precautionary measures.

• Infusion monitoring: observe patients closely for reactions during and after administration.
• Premedication: consider antihistamines or antipyretics to reduce infusion‑related symptoms.
• Liver function: assess baseline hepatic enzymes and monitor periodically.
• Immunogenicity: test for anti‑drug antibodies if clinical response diminishes.
• Hypersensitivity: avoid use in patients with known allergy to the product or its excipients.
• Pregnancy and lactation: use only if potential benefit justifies potential risk, as data are limited.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Mepsevii can interact with other medicines, primarily through immune modulation or overlapping safety profiles.

Major Interactions (Avoid)

• Live vaccines: concurrent administration may increase risk of infection; avoid during therapy.
• Concomitant enzyme replacement products: may lead to additive immune responses.

Moderate Interactions (Monitor Closely)

• Immunosuppressants (e.g., azathioprine, methotrexate): may increase infection susceptibility; monitor patient.
• Antipyretics (e.g., acetaminophen): may mask fever, a key infusion reaction sign; observe closely.
• Drugs affecting liver enzymes (e.g., strong CYP inducers): may alter hepatic monitoring parameters; adjust labs accordingly.