Another mechanism for challenging an issued patent is inter partes review.  Inter partes review essentially picks up where post grant review ends.  Inter partes reviews can only be filed after the later of either nine months after the granting of the patent or the date of the termination of a post grant review if a post grant review has been instituted.  Similar to a post grant review, an inter partes review must identify all real parties in interest as well as identify each claim that is challenged, the grounds for the challenge, and submit evidence that supports the grounds for the challenge.  Unlike post grant review, the grounds for challenging claims can only be raised under 35 U.S.C. §§ 102 (novelty) or 103 (obviousness) and can only be based on prior art consisting of patents (U.S. and foreign) or printed publications.  After filing a petition for inter partes review, a patent owner has the opportunity to file a preliminary response setting forth reasons as to why an inter partes review is not necessary.  The Director applies the threshold of whether there is a “reasonable likelihood that the petitioner would prevail with respect to at least one of the claims challenged in the petition” to decide whether to institute an inter partes review.  This decision may not be appealed.

Similar to a post grant review, inter partes review can still create estoppel.  Estoppel for inter partes review attaches with a written Patent Trial and Appeal Board (PTAB) decision and applies to any ground that the petitioner raised or reasonably could have raised.  This creates a narrower scope of estoppel than in post grant reviews because the grounds for challenging claims are limited to those raised under 35 U.S.C. §§ 102 or 103 instead of 35 U.S.C. § 282.  Therefore, a petitioner would not be prevented from raising invalidity defenses based on other grounds in other forums. Nonetheless, estoppel can still be avoided if the parties choose to settle.

Inter partes reviews are affected by other proceedings in the same way that post grant reviews are affected.  To ensure the inter partes review may be instituted, the petitioner should file an inter partes review on or before filing a civil action.  However, if a party is served with an infringement complaint by a patentee, an inter partes review must be filed within one year of being served.  Inter partes review also creates the same burden of proof for the petitioner, which is still lower than during litigation.  Unpatentability must be proven by a preponderance of the evidence.  During the review, the patent owner is allowed one motion to amend the challenged claims by cancellation or by proposing a reasonably number of substitute claims.  The review is statutorily required to be completed within one year of institution, however this time may be extended up to an additional six months with good cause.  Once the proceeding has come to a final decision, the final decision may be appealed.



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