Construction of a Claim Term by the PTAB Does Not Negate Indefiniteness

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. 

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