Anthrax Treatment Cocktail Found Immunogenetic

A new phase 4 study has discovered that co-administration of the monoclonal antibody raxibacumab with Anthrax Vaccine Adsorbed (AVA) does not negatively affect AVA immunogenicity.

Published in The Lancet on April 22, 2020, this finding suggests that combining the two might provide added benefit in people who may have inhaled spores containing Bacillus anthracis.

These researchers found that the geometric mean concentration (GMC) of anti-protective antigen antibodies was 26.5 micrograms (μg)/mL  in the 276 participants given only AVA versus 22.5 μg/mL in the 269 given AVA plus raxibacumab.

The between-group ratio was 1.18, which met the defined noninferiority margin and supports the hypothesis that the addition of raxibacumab doesn't undermine the vaccine's efficacy.

In a related commentary by Michael Norris, Ph.D., and Jason Blackburn, Ph.D., these scientists said that raxibacumab "is an effective, safe, and valuable addition to the current AVA vaccination regimen for anthrax post-exposure prophylaxis.”

“When anthrax exposure is suspected, recommended post-exposure prophylaxis is 60 days of antibiotics (ciprofloxacin or doxycycline) combined with anthrax vaccination. 

The AVA vaccine is approved for human use in the USA, and Anthrax Vaccine Precipitated (AVP) is approved in the UK. 

The major antigen in these vaccines is the Bacillus anthracis protective antigen; this molecule is secreted by B anthracis and creates a pore in the host membrane that binds then separately translocates lethal factor and oedema factor into the cell.”

“Even with prompt antibiotic treatment, the toxins released can still overwhelm the host, leading to toxaemia and death; thus, development and testing of anti-toxin treatments is needed.”

On December 13, 2019, the US Centers for Disease Control and Prevention (CDC), revised recommendations that apply to both pre- and post-exposure prophylaxis of anthrax.

The risk of exposure to aerosolized B. anthracis spores in the United States is very low. Anthrax is only endemic in a few sparsely populated areas in the western United States, such as in southern Texas. 

Anthrax is not contagious, which means you can’t catch it like the cold or flu, says the CDC.

The study was sponsored by the US Biomedical Advanced Research and Development Authority and GlaxoSmithKline, which produced raxibacumab. The drug is now owned by Emergent BioSolutions.

Precision Vaccinations publishes anthrax vaccine development news.