Stabilized biodegradable neurotoxin implants

#The present invention relates to biodegradable implants. More particularly, the invention relates to biodegradable implants including a neurotoxin that is effective to provide a therapeutic effect to a human or animal patient.

#Botulinum toxin type A is the most lethal natural biological agent known to man. Botulinum toxin type A is a polypeptide neurotoxin produced by the anaerobic, gram positive bacterium Clostridium botulinum and causes a neuroparalytic illness in humans and animals referred to as botulism. About 50 picograms of a commercially available botulinum toxin type A (available from Allergan, Inc., Irvine, Calif. under the tradename BOTOX® (purified neurotoxin complex) in 100 unit vials) is a LD50 in mice (i.e. 1 unit). Thus, one unit of BOTOX contains about 50 picograms (about 56 attomoles) of botulinum toxin type A complex. Interestingly, on a molar basis, botulinum toxin type A is about 1.8 billion times more lethal than diphtheria, about 600 million times more lethal than sodium cyanide, about 30 million times more lethal than cobra toxin and about 12 million times more lethal than cholera. Singh, Critical Aspects of Bacterial Protein Toxins, pages 63-84 (chapter 4) of Natural Toxins II, edited by B. R. Singh et al., Plenum Press, New York (1996) (where the stated LD50 of botulinum toxin type A of 0.3 ng equals 1 U is corrected for the fact that about 0.05 ng of BOTOX equals 1 unit). One unit (U) of botulinum toxin is defined as the LD50 upon intraperitoneal injection into female Swiss Webster mice weighing 18 to 20 grams each.

#Neurotransmitters are packaged in synaptic vesicles within the cytoplasm of neurons and are then transported to the inner plasma membrane where the vesicles dock and fuse with the plasma membrane. Studies of nerve cells employing clostridial neurotoxins as probes of membrane fusion have revealed that fusion of synaptic vesicles with the cell membrane in nerve cells depends upon the presence of specific proteins that are associated with either the vesicle or the target membrane. These proteins have been termed SNAREs. A protein alternatively termed synaptobrevin or VAMP (vesicle-associated membrane protein) is a vesicle-associated SNARE (v-SNARE). There are at least two isoforms of synaptobrevin; these two isoforms are differentially expressed in the mammalian central nervous system, and are selectively associated with synaptic vesicles in neurons and secretory organelles in neuroendocrine cells. The target membrane-associated SNAREs (t-SNARES) include syntaxin and SNAP-25. Following docking, the VAMP protein forms a core complex with syntaxin and SNAP-25; the formation of the core complex appears to be an essential step to membrane fusion. See Neimann et al., Trends in Cell Biol. 4:179-185:1994.

#The following definitions apply herein.

#“About” means plus or minus ten percent of the value so qualified.

#“Biocompatible” means that there is an insignificant or clinically acceptable inflammatory response at the site of implantation from use of the implant.