To Limit or Not to Limit: What Is the Basis of Your Prior Art Distinction During Prosecution?

Before Prost, Bryson, and Wallach. Appeal from the United States District Court for the District of Delaware

Summary: Distinguishing prior art based on the structure of the particles, not the process used to manufacture them, does not import a process limitation into the claims.

Vectura sued GlaxoSmithKline and Glaxo Group (“GSK”) for patent infringement. The asserted patent described a method of producing composite particles using high-energy milling. The asserted claims covered the particles not the method of producing them. GSK argued it does not infringe because the claims should be construed to require milling and GSK’s process does not include milling. The District Court construed the claims to not require milling and the jury found that GSK infringed. The District Court denied GSK’s post-trial motions and GSK appealed.

GSK argued the claim construction was erroneous because (1) the specification indicates that the milling process is essential and (2) the applicants disclaimed processes other than milling by distinguishing a prior art reference on the ground that it did not include the same milling step. The Federal Circuit recognized some portions of the specification suggested that milling is required but otherwise made clear that milling was merely a preferred process. The Federal Circuit also found that the applicant had distinguished the prior art based on the unique structure of the claimed particles, not the process to make them. Thus, the Federal Circuit affirmed.

Editor: Paul Stewart

Written by: Sean S. Kim & Adam Powell