Thalidomide is a
chiral compound.
Tests on mice indicated that one
enantiomer is
theraputic, the other
teratogenic. Unfortunately, a process in the
human body racemizes the compound, meaning that, even if you're given a
pure dose of the ``
safe'' version, you'll end up with the
teratogen in your
system. Further
tests using rabbits showed that both forms of the compound had both effects--
teratogenic and
theraputic.
It was first synthesised in 1953 and was widely prescribed for morning sickness from 1957 to 1962, but not in the USA, because the Food and Drug Administration had refused to approve it.
In 1992 the FDA urged drug manufacturers to evaluate racemates and enantiomers for new drugs. Patent protection means that if one enantiomer is protected, another might not be, so companies will try to see if they can market a racemate or an enantiomer of an existing product.