On May 20, 2013, in Dey, LP v. Sunovion Pharmaceuticals, Inc., the US Court of Appeals for the Federal Circuit held that clinical trials of a drug that would anticipate the patented drug did not create a public use bar even though the clinical trial participants did not sign confidentiality agreements. The Federal Circuit focused on the circumstances of the clinical trial and determined that they created an expectation of secrecy. The Federal Circuit reversed the district court's grant of the alleged infringer's motion for summary judgement of invalidity and remanded the case to the district court.

During the 1990s and the 2000s, Dey and Sunovion were simultaneously developing pharmaceutical products to treat lung disease. Both parties filed patent applications and conducted clinical trials on their products. Dey sued Sunovion for patent infringement. Sunovion asserted that some of Dey's patents were invalid under 35 U.S.C § 102(b) because Sunovion's clinical trial in which Sunovion tested its product was a prior public use of Dey's patented drug. For purposes of Sunovion's motion for summary judgement, Sunovion conceded that its clinical trial product was covered by the claims of the relevant Dey patent.

The Federal Circuit reiterated that to decide whether a prior use of the patented invention is a public use that would invalidate the patent covering invention, the key question is whether the use was either:

Even though this case involves a third party use, the key determination is whether the patented invention was publicly available before the critical date. If the third party use was secret or confidential, there is no invalidating prior public use.

Here, the Federal Circuit noted that:

Based on these facts, the Federal Circuit concluded that there was no public use of the patented invention because the circumstances of the clinical trial created an expectation of secrecy. The court reached this conclusion even though: