Mepact (Mifamurtide)

Mepact (mifamurtide) is used as an immunostimulant in the treatment of osteosarcoma.

• High‑grade non‑metastatic osteosarcoma (post‑surgical resection): improves event‑free survival when added to standard adjuvant chemotherapy.

• Mifamurtide binds to intracellular NOD2 receptors on monocytes and macrophages, triggering a signaling cascade that leads to the release of pro‑inflammatory cytokines such as TNF‑α, IL‑1β and IL‑6. This activation enhances the innate immune response and promotes the recruitment and activation of cytotoxic immune cells that target residual osteosarcoma cells after surgery.

Mepact may cause a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Fever: transient elevation of body temperature during or after infusion.
• Chills and rigors: shaking sensations often accompanying fever.
• Nausea or vomiting: gastrointestinal discomfort during treatment.
• Fatigue: general tiredness reported by many patients.
• Hypotension: mild drop in blood pressure during infusion.
• Injection site reactions: redness or discomfort at the infusion site.

Serious or Rare Side Effects

• Severe allergic reactions: anaphylaxis or bronchospasm requiring immediate medical attention.
• Hepatotoxicity: significant elevation of liver enzymes or hepatic dysfunction.
• Cytokine release syndrome: systemic inflammatory response with fever, hypotension and organ dysfunction.
• Cardiac arrhythmias: irregular heart rhythms observed in rare cases.
• Neutropenia: marked reduction in neutrophil count increasing infection risk.

Prior to initiating therapy, clinicians should assess patient suitability and monitor for potential complications.

• Monitor liver function: assess transaminases before and during treatment.
• Assess cardiac status: watch for hypotension or arrhythmias during infusion.
• Avoid use in active infections: risk of worsening infection due to immune modulation.
• Pregnancy and breastfeeding: safety unknown; use only if potential benefit justifies risk.
• Administration under medical supervision: infusion should be monitored for acute reactions.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Mepact may interact with other agents that affect immune function or cardiovascular stability.

Major Interactions (Avoid)

• Live vaccines: concurrent administration may alter vaccine efficacy or increase adverse events.
• High‑dose immunosuppressants (e.g., systemic steroids): may diminish the immunostimulatory effect of mifamurtide.

Moderate Interactions (Monitor Closely)

• Cytotoxic chemotherapy agents: overlapping toxicities such as myelosuppression should be monitored.
• Hepatically metabolised antibiotics (e.g., macrolides): may affect liver enzyme levels.
• Antihypertensive drugs causing hypotension (e.g., ACE inhibitors): monitor blood pressure during infusion.