The validity of a United States patent can be challenged in federal court litigation.  Patents can also be challenged in the U.S. Patent and Trademark Office, which, in most cases, is a quicker and less costly process.

The PTO provides three procedures by which a patent can be challenged: inter partes review (IPR), post grant review (PGR), and ex parte reexamination.  In IPRs and PGRs, the challenger and the patent owner both participate, and the proceedings are handled by the Patent Trial and Appeal Board (PTAB).  In an ex parte reexamination, the challenger is not involved after the request for reexamination has been filed, and the proceeding is handled by the PTO examiners.

In IPRs and PGRs, anyone except the patent owner may file a petition to challenge the patent.  The filing fees are high, $41,500 for an IPR and $47,500 for a PGR, with additional fees depending on the number of claims challenged.  The proceedings are handled by a three-judge panel of administrative judges with technical background in the field of the patent.  There are two phases in these proceedings.  The first phase consists of the filing of the petition by the challenger, the filing of a response by the patent owner, and the decision whether to institute the IPR or PGR by the PTAB.  If the PTAB institutes the IPR or PGR, then the second phase (the trial phase) begins.  The second phase consists of discovery (more limited than in litigation), briefing, an oral hearing, and a final written decision by the panel.  The entire process from institution to the final decision should take no more than 12 months.  The parties may appeal the decision to the Federal Circuit Court of Appeals.
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