The University of Minnesota discovered a compound that prevents viruses from reproducing or cancerous tumors from growing. It filed a patent application for a genus of that compound and filed a subsequent patent application expressly claiming a subgenus of that compound. During the time between filing of the two applications, Gilead Sciences, Inc. filed its own patent application directed to the subgenus.

Gilead sought cancellation of Minnesota’s patent to the subgenus based on its intervening patent application, filing an Inter Partes Review (IPR) before the Patent Trial and Appeal Board (PTAB) at the United States Patent and Trademark Office (USPTO). The PTAB found that Minnesota could not get around Gilead’s application because the original application did not either have ipse dixit support for the subgenus or sufficient “blaze marks” to identify the subgenus.

The Federal Circuit affirmed, finding substantial evidence supported the PTAB’s decision. Rejecting Minnesota’s complaint that the PTAB failed to address key aspects of its expert’s testimony explaining why a skilled artisan would have understood the original application as describing the claimed subgenus, the Federal Circuit held that it is "within the discretion of the Board to weigh the evidence of record" and that the Administrative Procedure Act (APA) does not require the PTAB to make express “credibility determination or other factfinding” concerning an expert’s testimony.

Future appellants may wish to demonstrate how consideration of its expert’s testimony establishes a lack of substantial evidence rather than presenting the issue as an APA violation per se.