The U.S. Food and Drug Administration (FDA) has approved Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)-(Equine) to treat patients showing signs of botulism following documented or suspected exposure to botulinum neurotoxin. The product, which will be stored in Strategic National Stockpile for emergency preparedness and responses, is derived from horse plasma and contains a mixture of antibody fragments that neutralize all of the seven botulinum nerve toxin serotypes known to cause botulism.
Botulism is a rare but serious paralytic illness caused by a nerve toxin produced by the bacterium Clostridium botulinum and sometimes by strains of Clostridium butyricum and Clostridium baratii. In the United States, an average of 145 cases are reported each year, and of these, approximately 15% are foodborne, 65% are infant botulism and 20% are wound. In foodborne botulism, symptoms generally begin 18 to 36 hours after eating a contaminated food, but they can occur as early as 6 hours or as late as 10 days.
This heptavalent antitoxin is the only product available for the treatment of botulism in adults, and for cases of infant botulism caused by nerve toxins other than types A and B.
The effectiveness of the product was studied in animals because it was not feasible or ethical to conduct efficacy studies in humans. The results provided substantial evidence that the antitoxin is reasonably likely to benefit humans with botulism. Under the FDA’s Animal Rule, the agency may approve a biological product when the results of well-controlled animal studies demonstrate that the product is reasonably likely to be effective, in addition to establishing safety in humans. This is the first approval of a plasma derivative using the Animal Rule.
The safety of the product was tested in 40 healthy human volunteers and also monitored in 228 patients who received the antitoxin experimentally under a botulism treatment program administered by the Centers for Disease Control and Prevention (CDC). The most commonly observed side effects were headache, fever, chills, rash, itching and nausea. Since the product is manufactured from horse plasma it may cause allergic reactions and a delayed hypersensitivity reaction (serum sickness) in people sensitive to horse proteins.
