Addressing the issue of prosecution disclaimer in the context of a predecessor patent, the U.S. Court of Appeals for the Federal Circuit affirmed a summary judgment of invalidity by anticipation, finding that a possible disclaimer made during prosecution of the application for a predecessor patent did not apply to the patent-in-suit because the pertinent claim limitations were not substantially similar.  Regents of the Univ. of Minn. v. AGA Med. Corp., Case No. 12-1167 (Fed. Cir., June 3, 2013) (Dyk, J.).

Regents of the University of Minnesota owns patents directed to medical devices for repairing heart defects and sued AGA Medical for infringement of those patents.  Following a claim construction hearing, the district court granted summary judgment that the patents were invalid as anticipated.  The university appealed.

The university argued that it had previously disclaimed the structure of the prior art reference during the prosecution of a predecessor patent.  The Federal Circuit disagreed.  The Federal Circuit found that the scope of the claim language was not substantially the same as that in the earlier pending application and therefore the previous disclaimer was not applicable. 

During claim construction, the district court determined the asserted claims of the patent should be treated as means-plus-function claims under § 112(f).  After claim construction, the district court found that asserted claims were invalid because the structure of the prior art reference was equivalent to the structure claimed in the asserted patent.  On appeal, the University argued that the structure of the prior art reference had been disclaimed during the prosecution of a predecessor patent. 

The Federal Circuit determined that the previous disclaimer was associated with a claim that did not include a means-plus-function element.  The Federal Circuit further explained that the proper inquiry is whether the scope of the claim limitation is substantially the same in the subsequent application as it was in the earlier application and the appropriate focus is on the scope of the claim element, not the meaning of particular words in isolation. 

The Federal Circuit evaluated the similarity between the earlier and later claim limitations and would only carry the disclaimer forward if there are only immaterial differences.  Applying this reasoning, the Federal Circuit found that the basis for distinguishing the prior art in the asserted patent was not the same as the predecessor application and the asserted patent contained a different claim limitation.  Thus, the original disclaimer did not carry over to limit the range of equivalents for the asserted patent and did not negate the district court’s anticipation finding.