ABT-594 was synthesised
from epibatidine, and initial testing was extremely
promising, with the compound binding many hundreds
of times more strongly to nicotinic receptors
of the pain pathways in the central nervous system
than those of the neuromuscular junction.
Epibatidine bound only 57 times
more strongly to receptors on the CNS.
The tests also indicated that
ABT-594 was not addictive, even though nicotine
itself is. Epibatidine is effective in combating
both inflammatory pain and neuropathic pain. (Inflammatory
is caused by direct cell damage and receptors
detecting, whereas neuropathic is caused by a
range of syndromes and pain persists without direct
stimuli from tissues), and ABT-594 showed promise
in both areas in the Phase I safety trials.
These involve a small number
of healthy volunteers, (20-100), usually under
constant observation, e.g. in a hospital, where
the side effects are noted.
ABT-594 had moved onto Phase
II testing in Europe a few years ago, after the
safety tests had demonstrated low toxicity levels.
These involve patients who actually require drug
relief. Half the patients are given a placebo
in this phase.
ABT-594 has completed this phase,
yet Abbott labs have not released results.