74 Am. U. L. Rev. 1013 (2025).

Abstract

The U.S. patent doctrine of “double patenting” allows an inventor to obtain many patents on obvious variants of the same invention as long as they file a “terminal disclaimer” agreeing that all of these patents will expire simultaneously. Two recent limitations on double patenting practice have led to vigorous protest from the patent bar. First, the Federal Circuit held in In re Cellect that patents tied by double patenting must expire on the same day even if one of the patents has received a patent term adjustment giving it a more-than-twenty-year term. Second, the USPTO proposed a rule (since withdrawn) that would have required a new terminal disclaimer to include a commitment to not enforce the patent if any claims in the patent to which it is tied are found to be obvious or not novel.

In this Article, we argue that the outcry over these decisions is unwarranted. We empirically show that double patenting is growing, with terminal disclaimers now being filed for over 15% of all patents, over 50% of litigated patents, and over 60% of patents covering FDA-approved drugs. The proliferation of patents on slight variations of the same invention has increased the burden on patent examiners and the costs to innovative firms of evaluating, licensing, and litigating existing patents. Reducing abuses associated with double patenting by preventing unjustified term extensions and lowering the costs of challenging invalid patents makes good policy sense.

Indeed, the USPTO and the courts could do more to restrict double patenting, including banning the practice altogether. Doing so would allow inventors and the USPTO to focus on important new inventions rather than trivial variants of existing ones.

* William H. Neukom Professor of Law, Stanford Law School, Of Counsel, Lex Lumina PLLC.
** Deane F. Johnson Professor of Law, Stanford Law School. © 2025 Mark A. Lemley & Lisa Larrimore Ouellette.

For helpful comments, thanks to Jonas Anderson, Bernard Chao, Laura Dolbow, Maya Durvasula, Jordana Goodman, Paul Gugliuzza, Rose Hagan, Tim Holbrook, Mark Janis, Lidiya Mishchenko, Amy Motomura, Laura Pedraza-Fariña, Nicholson Price, Arti Rai, Jason Reinecke, Michael Risch, Sean Seymore, Jake Sherkow, Sean Tu, and participants in the Advanced Patent Law Institute and Patent Scholars Roundtable at Stanford Law School. The authors declare that they have no relevant or material conflicts of interest related to the research described in this paper.