Background
Ablynx N.V. and Sanofi sought patent protection for fusion proteins containing immunoglobulin single-variable domains. The technology is intended to help predict and reduce unwanted protein interference in anti-drug-antibody assays. The pending claims were in U.S. Patent Application No. 17/409,019, a continuation filed in 2021 that traced its patent-term filing date to a 2012 international application.
The examiner rejected claims 51 and 54-56 for nonstatutory, or obviousness-type, double patenting. That judge-made doctrine prevents an applicant from obtaining claims that are not patentably distinct from claims it already owns unless the applicant files a terminal disclaimer. The examiner relied on six Ablynx/Sanofi patents. Each reference patent had a later patent-term filing date and would expire later than any patent issuing from the application under review.
Ablynx argued that those patents could not serve as double-patenting references because they could not extend the term of the earlier-expiring application. It also argued that the Board should apply the more demanding two-way obviousness test and that using later-developed patents against an earlier-developed invention would discourage follow-on research and restrict the ability to transfer patent rights.
The Board’s Holding
The Patent Trial and Appeal Board affirmed every rejection. Writing for the three-judge panel, Administrative Patent Judge Zhenyu Yang concluded that In re Fallaux controlled. In Fallaux, the Federal Circuit allowed later-filed, later-expiring patents to support a double-patenting rejection because the doctrine serves a second purpose beyond preventing an unjustified extension of patent term: protecting accused infringers from multiple lawsuits by different owners of patents claiming obvious variants of the same invention.
The panel distinguished decisions such as Allergan USA, Inc. v. MSN Laboratories Private Ltd. and In re Cellect, LLC as addressing narrower and materially different patent-term questions. It emphasized that Fallaux remained binding precedent and had recently been cited by the Federal Circuit. Consequently, the fact that all six reference patents were filed later and would expire later did not disqualify them as double-patenting references.
The Board also applied the ordinary one-way test, which asks whether the pending application claims would have been obvious over the issued patent claims. The two-way test is a narrow exception available when the Patent Office is solely responsible for the sequence in which related applications issue. Here, the applicants waited more than nine years after the 2012 priority application before filing the continuation containing the disputed claims. The panel therefore concluded that the Patent Office was not solely responsible for the delay. Ablynx did not separately challenge the examiner’s detailed findings that the pending claims were not patentably distinct under the one-way test.
Finally, the Board rejected the equitable and policy objections. It explained that the applicants could amend the pending claims to make them patentably distinct or file a terminal disclaimer requiring common ownership. In the panel’s view, that common-ownership condition is the quid pro quo for obtaining claims that are not patentably distinct and directly addresses the risk of separate owners bringing multiple suits. The anti-harassment rationale therefore supported the rejections even if issuing the claims would not lengthen the practical patent term.
Key Takeaways
- A later-filed, later-expiring patent can still serve as an obviousness-type double-patenting reference when the claims are not patentably distinct.
- The risk of multiple suits by different assignees can independently justify a terminal disclaimer, even without an unjustified extension of patent term.
- The two-way obviousness test remains exceptional and generally is unavailable when the applicant could have presented the claims earlier.
- Continuation strategy can create double-patenting exposure across patents covering both foundational and follow-on biotechnology.
Why It Matters
Baumeister exposes a difficult consequence of modern patent-family practice: a company may obtain patents on later-developed improvements and then find those patents used against an earlier-expiring continuation covering broader technology. A terminal disclaimer may avoid the rejection, but its common-ownership requirement can limit licensing, assignment, and portfolio-separation options.
The panel declined to follow the original 2024 decision in Ex parte Baurin because that ruling was then nonprecedential and rehearing remained pending. The USPTO’s Appeals Review Panel later issued a precedential rehearing decision in Baurin that reinstated the rejections under existing precedent while openly questioning whether anti-harassment should remain an independent basis for the doctrine. Baumeister is now on appeal as In re Ablynx N.V., Federal Circuit No. 26-1333. The Federal Circuit has not yet ruled, so the scope of the anti-harassment rationale remains unsettled.