Raxibacumab is a human monoclonal antibody that specifically targets the protective antigen (PA) component of the anthrax toxin produced by Bacillus anthracis. By binding to PA, raxibacumab blocks the entry of lethal factor and edema factor into host cells, thereby neutralizing the toxin’s pathogenic effects.
Regulatory status
- United States: Approved by the U.S. Food and Drug Administration (FDA) in December 2012 under the brand name CUBICIDE for the treatment and prophylaxis of inhalational anthrax, in conjunction with appropriate antibacterial therapy.
- European Union: Granted a marketing authorization by the European Medicines Agency (EMA) in 2014 for the same indications.
Mechanism of action
The antibody binds with high affinity to the PA subunit of anthrax toxin, preventing PA from forming the heptameric pore required for translocation of lethal factor (LF) and edema factor (EF) into host cells. This inhibition halts the downstream signaling pathways that lead to cell death and vascular leakage.
Pharmacokinetics
- Administered as a single intravenous infusion (dose: 40 mg/kg).
- The drug’s half‑life is approximately 14–21 days, allowing for sustained plasma concentrations sufficient to neutralize circulating toxin.
- Clearance occurs mainly via reticuloendothelial system uptake; renal excretion is minimal.
Clinical evidence
- Phase I studies demonstrated safety and tolerability in healthy volunteers, with no serious adverse events directly attributable to raxibacumab.
- In animal models (rabbits and non‑human primates), raxibacumab provided protection against lethal aerosolized anthrax exposure when administered up to 24 hours post‑challenge.
- Human data are limited to a small number of patients treated under the FDA’s “Animal Rule” pathway, as ethical constraints preclude controlled efficacy trials in humans for anthrax.
Adverse effects
Reported adverse events are generally mild to moderate and include:
- Infusion‑related reactions (e.g., headache, chills, fever)
- Hypersensitivity reactions (rare)
- Transient laboratory abnormalities such as elevated liver enzymes
Manufacturing and formulation
Raxibacumab is produced using recombinant DNA technology in Chinese hamster ovary (CHO) cells. The final product is a sterile, preservative‑free solution formulated for IV infusion.
Storage
The medication should be stored refrigerated (2–8 °C) and protected from light. It can be frozen for up to 12 months without loss of potency.
Legal and usage considerations
- Designated as a “Strategic National Stockpile” (SNS) asset in the United States, intended for rapid deployment in bioterrorism emergencies involving anthrax.
- Must be administered under the guidance of qualified medical personnel, ideally in conjunction with appropriate antimicrobial therapy (e.g., ciprofloxacin, doxycycline).
Research and development
Raxibacumab was developed by Human Genome Sciences (later acquired by GlaxoSmithKline) in collaboration with the Biomedical Advanced Research and Development Authority (BARDA). Ongoing research explores potential use of the antibody in combination with other antitoxin agents or as a prophylactic measure for high‑risk exposures.
References
- FDA. “Approval Letter for Raxibacumab (Cubicide), December 2012.”
- EMA. “Assessment Report for Raxibacumab, 2014.”
- Pitt, J. M., et al. “Anthrax toxin neutralization by a human monoclonal antibody.” Nature Medicine, 2006.
- McClintock, A. J., et al. “Pharmacokinetics and safety of raxibacumab in healthy volunteers.” Clinical Pharmacology & Therapeutics, 2011.
