The doctrine of definiteness requires a patent to clearly state
what the inventor considers to be their invention. Of course, the
PTAB interprets various claim terms when determining whether a
prior art reference anticipates or renders obvious a particular
claim. So what happens when an accused infringer challenges a claim
before the PTAB, and after a PTAB claim interpretation, then
challenges the definiteness of that same claim term in district
court?
The case of Depomed, Inc. v. Purdue Pharma, L.P., Civil
Action No. 13-571 (MLC) (D. NJ) considered this very issue. Depomed
sought to preclude Purdue Pharma from amending their invalidity
contentions to assert indefiniteness after the 2014 Supreme Court
Nautilus decision changed the standard for definiteness.
Among other things, Depomed argued the PTAB had already construed
the term "substantially all of said drug" so any such
assertion of indefiniteness would have been futile.
