Wednesday, January 6, 2021 The doctrine of obviousness-type double patenting is one of the most complicated and most confounding aspects of U.S. patent law. Although a Terminal Disclaimer can overcome most obviousness-type double patenting rejections, Terminal Disclaimers are not permitted in all circumstances where obviousness-type double patenting may arise. In a Federal Register Notice dated December 30, 2020, the USPTO published proposed rule changes that would close one gap in Terminal Disclaimer practice related to inventions made pursuant to joint research agreements. Terminal Disclaimer Practice Obviousness-type double patenting may arise when a later-expiring patent/application claims subject matter that is deemed to be an obvious variation of subject matter claimed in an earlier-expiring patent/application with the same or overlapping inventorship or ownership. To avoid an “unjust timewise extension of the right to exclude” and “the risk of multiple infringement suits by different parties,” U.S. patent law prohibits the granting (or enforcement) of the later-expiring patent/application unless a Terminal Disclaimer is filed that aligns its expiration date with that of the earlier-expiring patent/application.