Before 1995, the term of a U.S. utility patent was 17 years from the day the patent issued. In 1994, the federal statutes were changed to make the patent term 20 years from the effective filing date of the patent application. This change was part of the Uruguay Round Agreements Act and was intended to make U.S. patents comparable to foreign patents, which, in most countries, expire 20 years from their filing dates.
However, in order to address the problem of delays caused by the Patent and Trademark Office during the prosecution of a patent, Congress enacted statutes providing for the addition of specific numbers of days to a patent's term. See 35 U.S.C. section 154(b).
The statutes provide that time is added to a patent's 20-year term in three types of situations: if the PTO fails to meet required deadlines in the prosecution of a patent application; if the prosecution takes longer than three years; or if the patent application is involved in an interference (a proceeding to determine ownership) or a successful appeal. In all three situations, the number of days to be added is reduced by any time in which the patent applicant is not reasonably pushing the prosecution forward. The three-year rule is also subject to several exclusions: for time taken up in a continued examination requested by the applicant, for time while the application is under an interference or appeal, and for any delay requested by the applicant.
The calculation of the number of added days is the "patent term adjustment." Calculating the patent term adjustment is not necessarily easy to do in all cases. In Mayo Foundation for Medical Education and Research v. Iancu, 938 F.3d 1343 (Fed. Cir. September 16, 2019), the patent owner disagreed with the PTO's calculation and took the matter all the way to the Federal Circuit Court of Appeals.
Mayo obtained a patent for antibodies used to combat immune system diseases. The application had an effective filing date in 1999 and issued in 2015. When the patent issued, the PTO determined that the patent term adjustment was 621 days. Mayo contended that it was 685 days. The PTO denied Mayo's request. Mayo then appealed the PTO's decision to the U.S. district court for the Eastern District of Virginia. At some point, both parties changed their calculation of the patent term adjustment: the PTO calculated it at 604 days and Mayo contended it was 723 days. The district court ruled in favor of the PTO.
Mayo appealed to the Federal Circuit. The issue before the court was how to determine the exclusions under the three-year rule. Mayo claimed that the PTO incorrectly calculated the number of days to be excluded for the time the application had been under continued examination and in an interference.
The appellate court ruled for the PTO. The court said that Mayo's arguments were "strained" or incorrect. The court held that:
"We are also persuaded by the PTO's point that Mayo's rule could require an unduly burdensome, fact-intensive inquiry into when the PTO actually conceded the allowability of the claims."
So, it turns out that determining a patent's term is not so easy. However, it isn't likely that the issue will be critical or even arise in most cases. In this case, the appeal was fought over 119 days. Given that the patent only had four years of life left when it issued, the 119 days was a significant period of time.
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