The US Food and Drug Administration (FDA) has approved GlaxoSmithKline's raxibacumab for the treatment of adult and paediatric patients with inhalational anthrax due to Bacillus anthracis in combination with appropriate antibacterial drugs and for prophylaxis of inhalational anthrax when alternative therapies are not available or are not appropriate.

The effectiveness of raxibacumab is based solely on efficacy studies in animal models as it is not ethical or feasible to conduct controlled clinical trials with intentional exposure of humans to anthrax. The safety of raxibacumab has been studied in healthy adult volunteers, however, there have been no studies of raxibacumab in the paediatric population. Dosing in paediatric patients was derived using modelling based on data in adults. Raxibacumab does not have direct antibacterial activity. Raxibacumab does not cross into the brain and does not prevent or treat anthrax meningitis. Raxibacumab should be used in combination with appropriate antibacterial drugs.

“Raxibacumab is an important part of an ongoing collaboration between GSK and the US government to address a range of public health concerns,” said Zhi Hong, senior vice president and head of Infectious Diseases, GlaxoSmithKline. “It will be an important addition to the new approaches required to address our critical bio-defense needs.”

“Human Genome Science began work on raxibacumab in 2001 in response to the anthrax attacks in the United States. Our development programme charted new territory in terms of the science and the regulatory pathway and was a result of our successful collaboration with the Biomedical Advanced Research and Development Authority (BARDA) and FDA,” said Sally Bolmer, senior vice president of Development and Regulatory Affairs at HGS, where the drug was discovered and developed. HGS was recently acquired by GSK.

Raxibacumab is the first monoclonal anti-toxin to be approved for inhalational anthrax. Anthrax is a rare and lethal disease, caused by a toxin producing bacterium. While antibiotics target the anthrax bacteria, raxibacumab offers an additional mechanism by blocking the activity of the anthrax toxin, which plays a key role in the progression of the disease. Raxibacumab demonstrated an improved survival rate over  control in two relevant animal models both in combination with antibiotics and alone.

The safety of raxibacumab has been evaluated in 326 healthy adult volunteers treated with the recommended dose. Infusion reactions were reported in clinical trials including reports of rash, urticaria (hives) and pruritus (itching). If these reactions occur, slow or interrupt raxibacumab infusion and administer appropriate treatment based on the severity of the reaction. Patients should be premedicated with diphenhydramine (an antihistamine) before treatment. The most frequently reported adverse reactions (= 1.5%) were rash, pain in an extremity (arms and legs), pruritus (itching) and somnolence.

The recommended adult dosage of raxibacumab is a single dose of 40 mg/kg given intravenously over a period of two hours and 15 minutes. Administer diphenhydramine within an hour of treatment to reduce the risk of infusion reactions. The recommended dose for children is based on weight.

Raxibacumab is not approved or licensed in Europe and currently is not approved in other parts of the world for the treatment or prophylaxis of patients with inhalational anthrax.

Raxibacumab was discovered and developed by Human Genome Sciences (HGS) in conjunction with the Biomedical Advanced Research and Development Authority (BARDA) of the Office of the Assistant Secretary for Preparedness and Response (ASPR), US Department of Health and Human Services (HHS) under contract number HHS010020050006C. It is now part of GSK’s portfolio, following GSK’s acquisition of HGS in July 2012. The development of raxibacumab is the result of a coordinated response to a recognised public health threat and the US government’s request for new medical countermeasures in the event of an anthrax attack against the civilian population. The US Government is currently the sole recipient of raxibacumab supplies.