Botulinum toxin type B: An overview of its biochemistry and preclinical pharmacology

Produced by Clostridium botulinum, botulinum toxins are high molecular weig ht protein complexes consisting of the neurotoxin and additional nontoxic p roteins that function to protect the toxin molecule. The neurotoxin acts to inhibit the release of acetylcholine at the neuromuscular junction, causin g muscle paralysis. Purified toxin complexes have found a niche in the trea tment of clinical disorders involving muscle hyperactivity. The different s erotypes ore structurally and functionally similar; however, specific diffe rences in neuronal acceptor binding sites, intracellular enzymatic sites, a nd species sensitivities suggest that each serotype is its own unique pharm acologic entity. Recently, botulinum toxin type B has been developed as a l iquid formulation to avoid the lyophilization (vacuum-drying) and reconstit ution processes associated with decreasing the potency and stability of cur rent type A toxin preparations. Biochemical tests were conducted to evaluat e the quality of toxin in this formulation. In 3 consecutive manufacturing lots, the botulinum toxin type B complex was found to be highly purified, i ntact, uniform, and consistent from lot to lot. Also, It showed long-term s tability at refrigerator and room temperatures (2 to 25 degreesC), Electrop hysiologic studies in cynomolgus monkeys showed that botulinum toxin type B is effective in paralyzing injected muscle groups, with minimal spread to relatively distant noninjected muscles. Copyright (C) 2001 by W.B. Saunders company.