Safety and Clinical Outcomes of an Equine-derived Heptavalent Botulinum Antitoxin Treatment for Confirmed or Suspected Botulism in the United States

Abstract Background Botulism is a rare, life-threatening paralytic illness. Botulism Antitoxin Heptavalent (A,B,C,D,E,F,G)-(Equine) (BAT) manufactured by Emergent BioSolutions Canada Inc is an equine-derived heptavalent botulinum antitoxin product indicated for the treatment of symptomatic botulism following documented or suspected exposure to botulinum neurotoxin serotypes A-G in adults and pediatric patients. BAT product was US-licensed in 2013. Methods In the United States, from October 2014 through July 2017, safety and clinical outcomes data were collected under a registry for patients treated with BAT product. Results Registry patients had a median age of 51 years (range, 32 days to 92 years). Among 162 patients, 7 (4.3%) experienced BAT product–related serious adverse events, including 1 (0.6%) report each of pneumonia, pneumonia aspiration, ventricular tachycardia, upper gastrointestinal hemorrhage, anaphylactic reaction, acute kidney injury, and acute myocardial infarction. Thirty-one (19.1%) patients had 41 BAT product–related adverse events. Six (3.7%) deaths were reported in the registry. All deaths were attributed to the underlying illness and were assessed as unlikely related to BAT product. Among 113 (69.8%) patients with a final diagnosis of botulism, those treated early (≤2 days) spent fewer days in the hospital (5 vs 15.5 days), in the intensive care unit (ICU) (4 vs 12 days), and on mechanical ventilation (6 vs 14.5 days) than those treated late (>2 days), respectively. Conclusions BAT product was well tolerated in patients. Treatment with BAT product at ≤2 days of symptom onset was associated with shorter hospital and ICU stays, and shorter duration and need for mechanical ventilation, showing clinical benefit associated with early treatment. The effectiveness of Botulinum Antitoxin Treatment drug product is based on efficacy studies conducted in animal models. An observational patient registry was conducted in the United States to enroll patients treated with BAT product to further assess safety and clinical outcomes.