One Missing Link Can Break an Obviousness Argument

IPRs are often filed to challenge important patents – the same patents likely to be tested in litigation. In such circumstances, parties should pay careful attention when asserting arguments in the IPR that were addressed in the litigation. Several generic drug makers faced this circumstance in relation to obviousness arguments made in a series of IPRs against Eli Lilly & Co. (IPR2016-00318, IPR2016-00237 and IPR2016-00240), in which similar arguments made in a co-pending appeal before the Federal Circuit were found to be lacking. While the PTAB is not required to agree with courts on all issues, particularly in view of the fact that the standards of review between the two venues are different, these IPRs illustrate that petitioners and patent owners would be wise to carefully address what courts have said about the arguments at issue.

The challenged claims in Eli Lilly’s U.S. Patent No. 7,772,209 are directed to a method for co-administering the antifolate pemetrexed disodium (Alimta®) with a combination of folic acid and vitamin B12 for the treatment of cancer. Antifolates like Alimta block the action of folic acid, halting the growth of cancer cells as well as normal cells. The petitioners pointed to several prior art references for their purported teachings that pretreatment with both vitamin B12 and folic acid reduces drug toxicity and side effects.  

However, the petitioners faced an uphill battle, because a district court had previously evaluated a similar argument and affirmed the finding that the principal references relied on in the petition did not suggest pre-treatment with vitamin B12. By the oral hearing, the Federal Circuit had already affirmed the district court, calling this insufficiency in the prior art the “missing link” in the prior challengers’ argument. The Federal Circuit’s decision was not lost on the PTAB, and during the hearing, the petitioner was specifically asked to explain how the challenge in the IPR was any different than the one that failed in the courts.

Although the petitioners emphasized their additional evidence, the PTAB was not persuaded. It commented that the petitioners “did not overcome the gaps in the prior art, including the ‘missing link between vitamin B12 deficiency and pemetrexed toxicity.’” Bolstered by evidence that secondary considerations favored non-obviousness, including skepticism of the FDA, the PTAB, as the district court previously had, concluded that the challenged claims were not unpatentable. 


Whether you find yourself on the petitioner or patent owner side of an IPR obviousness challenge, deficiencies in an obviousness argument unearthed during prior litigation can illuminate your path forward. For petitioners, filling the gaps in the prior art before petitioning for IPR could strengthen an obviousness argument. For patent owners, emphasizing these gaps could be a cornerstone in a defense to save your claims.