How does the prior art exception affect double patenting rejections?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The prior art exception under 35 U.S.C. 102(b)(2)(C) can have implications for double patenting rejections. According to MPEP 717.02(c):

• Commonly owned applications of different inventive entities may be rejected on the ground of double patenting, even if the later filed application claims 35 U.S.C. 120 benefit to the earlier application.
• Double patenting rejections may arise as a result of the joint research agreement exception.
• For double patenting analysis, the U.S. application or patent and the subject matter excepted under 35 U.S.C. 102(b)(2)(C) and 35 U.S.C. 102(c) will be treated as if commonly owned.

The MPEP further states: Congress recognized that deeming a joint research agreement as common ownership would result in situations in which there would be double patenting rejections between applications not owned by the same party.

To overcome double patenting rejections, applicants may file a terminal disclaimer in accordance with 37 CFR 1.321.