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.
The unexpected properties of Plavix[R], the dextrorotatory enantiomer of clopidogrel, ultimately rendered the compound nonobvious over its racemate.
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.
161) Therefore, the unpredictable properties of the resulting enantiomers, coupled with the uncertainty of the separation, ultimately rendered the dextrorotatory enantiomer of clopidogrel nonobvious.
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.