Douglas Barker

Botulism neurotoxins are highly toxic and are potential agents for bioterrorism. The development of effective therapy is essential to counter the possible use of these toxins in military and bioterrorism scenarios, and to provide treatment in cases of natural intoxication. Guinea pigs were intoxicated with a lethal dose of botulinum neurotoxin serotypes A, B, C, D, E, F or G, and at onset of the clinical disease intoxicated animals were treated with either BAT^® [Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)–(Equine)] or placebo. BAT product treatment significantly (p<0.0001) enhanced survival compared to placebo for all botulinum neurotoxin serotypes and arrested or mitigated the progression of clinical signs of botulism intoxication. These results demonstrated the therapeutic efficacy of BAT product in guinea pigs and provided supporting evidence of effectiveness for licensure of BAT product under FDA 21 CFR Part 601 (Subpart H Animal Rule) as a therapeutic for botulism intoxication to serotypes A, B, C, D, E, F or G in adults and pediatric patients.

Botulism is a disease caused by neurogenic toxins that block acetylcholine release, resulting in potentially life threatening neuroparalysis. Seven distinct serotypes of botulinum neurotoxins (BoNTs) have been described and are found in nature world-wide. This, combined with ease of production, make BoNTs a significant bioweapon threat. An essential countermeasure to this threat is an antitoxin to remove circulating toxin. An antitoxin, tradename BAT (Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)–(Equine)), has been developed and its efficacy evaluated against all seven serotypes in guinea pigs. Studies were conducted to establish the lethal dose and clinical course of intoxication for all seven toxins, and post-exposure prophylactic efficacy of BAT product. Animals were monitored for signs of intoxication and mortality for 14 days. Guinea pig intramuscular LD_50s (GPIMLD₅₀) for all BoNTs ranged from 2.0 (serotype C) to 73.2 (serotype E) of mouse intraperitoneal LD₅₀ units. A dose of 4x GPIMLD₅₀ was identified as the appropriate toxin dose for use in subsequent efficacy and post-exposure prophylaxis studies. The main clinical signs observed included hind limb paralysis, weak limb, change in breathing rate/pattern, and forced abdominal respiration. Mean time to onset of clinical signs ranged from 12 hours (serotype E) to 39 hours (serotype G). Twelve hours post-intoxication was selected as the appropriate time point for intervention for all serotypes apart from E where 6 hours was selected because of the rapid onset and progression of clinical signs. Post-exposure treatment with BAT product resulted in a significantly (p0.008 scaled human dose for serotypes A, B, C, F and G, at >0.2x for serotype D and >0.04x for serotype E. These studies confirm the efficacy of BAT as a post-exposure prophylactic therapy against all seven known BoNT serotypes.