In Wyeth & Cordis Corp. v. Abbot Labs., the Federal Circuit affirmed a ruling by the District Court for the District of New Jersey granting summary judgment of invalidity as to certain claims of Wyeth’s patents (5,516,781 and 5,563,146) due to nonenablement and lack of written description. The issue on appeal was whether practicing the full scope of Wyeth’s claims would require undue experimentation based on, in part, the number of claimed species and the level of unpredictability in the art.

The claims at issue were concerned with the treatment of restenosis using rapamycin. Although Wyeth only disclosed one species of rapamycin, sirolimus, the claims covered any species of rapamycin having a macrocyclic triene ring and demonstrating immunosuppressive and antirestenotic effects. Experts for Wyeth limited the number of candidate rapamycin compounds to significantly less than a million, but conceded that any substitution of sirolimus could alter the immunosuppressive and antirestenotic effects, i.e. any candidate rapamycin would need to be tested for the desired effects.

After considering the expert testimony from both parties, the Federal Circuit agreed with the district court’s conclusion that practicing the full scope of Wyeth’s claims would require synthesizing and testing tens of thousands of candidate rapamycin compounds. Accordingly, because Wyeth had not disclosed any instruction on how a candidate rapamycin might be synthesized and testing a single candidate rapamycin according to Wyeth’s assays would take several weeks, the Federal Circuit upheld the district court’s ruling that Wyeth’s claims were invalid on the grounds that practicing the claims would require undue experimentation. In so doing, The Federal Circuit focused on Wyeth’s lack of guidance towards preferred substitutions, or the synthesis thereof.