Of course, it won't do anything...
Of course NGF is not going to make it past the BBB, but I wonder if it couldn't yet have a beneficial peripheral effect or two. Maybe someone would like to try injecting some into his penis to see if it can increase sensitivity?

Sounds crazy, but if injecting chocolate or nicotine is a sensible thing in the minds of some... people, why not NGF?
Edit: Forgot to mention: You can buy velvet antler extract over the internet and even certain health food stores. One such extract supposedly contains all of the following:
Nerve growth factor, neurotrophin 3, insulin-like growth factor I & II, transforming growth factor alpha & beta, epidermal growth factor, vascular endothelial growth factor, fibroblast growth factor, bone morphogenetic protein 4, interleukins
There exists the distinct possibility of contracting some form of transmissible spongiform encephalopathy, though, so one should tread with caution (it's also entirely possible that the supplement contains none or few of the specified ingredients, so that's another point of concern). Although there are no known cases of a human developing creutzfeldt-jakob disease as a result of exposure to elements of the central nervous system of a deer infected with prions, and no known cases of chronic wasting disease in New Zealand (where most velvet antler extract is produced), it's still perhaps something you shouldn't mess around with.