Patent litigation has shifted to the U.S. Patent and Trademark Office (USPTO) through inter partes review (IPR) and post grant review (PGR) proceedings as well as derivation proceedings. These adversarial procedures for challenging the validity of a patent differ significantly from the prior reexamination proceedings and include characteristics of a district court bench trial on the issue of patent validity, albeit before the USPTO. These proceedings feature discovery between the parties and, in many cases, a “trial” before the USPTO Patent Trial and Appeal Board (PTAB).