(87) Thus, "a person of ordinary skill in this field would not reasonably have predicted that the dextrorotatory enantiomer
would provide all of the antiplatelet activity and none of the adverse neurotoxicity.
(154) Once separated, it was determined that the dextrorotatory enantiomer imparted all of the beneficial antiplatelet activity, while the levorotatory enantiomer imparted all of the neurotoxicity of the racemate.
(159) The district court, with the Federal Circuit affirming, rejected this construction of the law, stating that the evidence overwhelmingly pointed to the unexpected characteristics of the dextrorotatory enantiomer, which was held to be nonobvious over the racemate.
Forest, the owner of a patent covering the racemic antidepressant citalopram, was granted a patent on the dextrorotatory enantiomer of citalopram.
The district court, with the Federal Circuit affirming, held that the difficulty of the separation and the unexpected properties of the dextrorotatory enantiomer rendered the enantiomer nonobvious in spite of the racemate.