Inter partes review (IPR), post-grant review (PGR), and covered business method review (CBM) are procedures for challenging the validity of issued U.S. patents before the Patent Trial and Appeal Board (PTAB). In China, patent invalidations are brought before the Patent Re-examination Board (PRB) in the form of a patent invalidation action. We have experience in these proceedings and can assist you in defending an invalidity challenge against a patent or bringing a validity challenge against an issued patent.