Just because your issued patent was examined by the USPTO does not mean that it is free from challenge. Your competitors may, of course, scrutinize your patent and use IPR to challenge its validity—potentially turning your patent shield into a roadmap to their next product. This was the case in a recent IPR.
In IPR 2017-02131, Merck alleged that Pfizer’s patent covering vaccines against the bacteria responsible for respiratory diseases like pneumonia would have been obvious to an ordinary artisan. During prosecution, Pfizer had introduced a limitation that restricted the size range of the particles in the vaccine in response to art cited by the examiner that didn’t disclose the specific size range claimed by Pfizer.
While Merck’s IPR references did not disclose the specific claimed size range, they did disclose a range which overlapped with Pfizer’s and disclosed methods of manipulating the size of the vaccine particles. Merck argued that in light of the references, someone skilled in the art would have been able and motivated to find optimal sizes without undue experimentation.
The PTAB agreed with Merck and found the challenged claims unpatentable. The PTAB noted that while Pfizer’s patent claims compositions within a specific range not expressly shown in the references, “size,” in the context of the invention, “is a results effective variable associated with improved stability of conjugates and good immune response, limited only by filter size, thereby rendering optimization within the grasp of one of ordinary skill in the art.” The claims would have, therefore, been obvious.
While the obviousness of optimizing so-called “result effective variables”—variables that are recognized to have an effect on the efficacy of the invention—is a legal principle that predates IPR, it is evaluated by different audiences during an IPR. Unlike juries in district court proceedings, PTAB judges often have technical experience in the relevant field, and so may be more willing to accept that certain methods and subject matter would have been routine to a person of ordinary skill in the art.
This decision also highlights that during prosecution, a limitation that distinguishes the claim from the prior art may not be enough to protect from a challenge if the limitation is “obvious to try” or can be ascertained through “optimization.”