IP Law Daily, PATENT—PTAB: Appeals Review Panel reinstates double-patenting rejections of Sanofi antibody claims in precedential decision, (Aug 10, 2026)

By Saurabh Kashyap, B.A., M.A., LL.B., LL.M.

Established precedent required consideration of the risk that separate owners could bring multiple infringement suits even when the challenged claims would expire before the reference patent.

In a precedential decision, the Patent Trial and Appeal Board’s Appeals Review Panel (ARP) has reversed earlier Board decisions and reinstated an examiner’s obviousness-type double patenting (OTDP) rejections of claims 1–18 of a Sanofi patent application covering an antibody-like binding protein. On sua sponte rehearing, the ARP held that the Board erred by treating the absence of an improper patent-term extension as dispositive. Binding Federal Circuit precedent recognized a second, independent justification for OTDP—preventing potential harassment through infringement suits brought by separate owners of patents covering the same invention or obvious variants. The ARP also held that the Federal Circuit’s Allergan exception did not apply because the application was neither the first actually filed nor first issued in its patent family and had a different patent-term filing date from the principal reference patent (Ex parte Baurin, No. 2024-002920 (PTAB Aug. 6, 2026)).

Background. Sanofi, the applicant and current owner of the relevant application and principal reference patent, is a pharmaceutical company engaged in developing and commercializing medicines and biologic therapies. The application and reference patent share four inventors—Christian Beil, Ercole Rao, Christian Lange, and Carsten Corvey—and are presently commonly owned by Sanofi.

The dispute primarily concerned U.S. Patent Application No. 17/135,529 (the ’529 Application) and U.S. Patent No. 10,882,922 B2 (the ’922 patent). The ’529 Application was filed December 28, 2020, and, through continuation applications, claimed priority benefit from a nonprovisional application filed March 28, 2012. Any patent issuing from it would therefore ordinarily expire March 28, 2032. The ’922 patent was filed on April 13, 2017, issued on January 5, 2021, and has a twenty-year term ending on April 13, 2037, plus 70 days of patent-term adjustment. The appealed claims covered an antibody-like binding protein having specified characteristics.

The examiner rejected claims 1–18 for OTDP based principally on the ’922 patent in combination with U.S. Patent Application Publication No. 2009/0162359 A1 (“Klein”), and entered five additional OTDP rejections involving other patents or an application together with Klein. Sanofi did not dispute the examiner’s finding that the pending claims would have been obvious over the ’922 patent claims in view of Klein. Instead, it challenged whether the later-expiring ’922 patent could serve as an OTDP reference against claims that, if granted, would expire years earlier. The Board agreed and reversed the rejections in November 2024. After the examiner sought rehearing, the Board adhered to its position in December 2025. The ARP then granted sua sponte rehearing in March 2026 and requested additional briefing, including on the effect of Allergan USA, Inc. v. MSN Laboratories Private Ltd., the relevance of projected expiration dates, and whether the anti-harassment rationale independently supported an OTDP rejection.

Allergan exception did not apply. The ARP rejected Sanofi’s argument that Allergan USA, Inc. v. MSN Laboratories Private Ltd., 111 F.4th 1358 (Fed. Cir. 2024) controlled the appeal. Allergan held that a first-filed, first-issued, later-expiring claim could not be invalidated by a later-filed, later-issued, earlier-expiring reference claim sharing a common priority date. The ARP construed “first-filed” to mean the actual filing date. It found that Allergan did not apply because the ’529 Application failed the decision’s first-filed, first-issued, and common-priority requirements. It was not the first application actually filed in its family, remained pending, and had a different patent-term filing date from the ’922 patent. Thus, the ARP concluded that none of the relevant Allergan conditions was satisfied.

Anti-harassment rationale supported OTDP rejection. The ARP found that the Board committed its central legal error by treating prevention of unjustified patent-term extension as the only independently sufficient basis for OTDP. It relied on In re Hubbell, 709 F.3d 1140, 1145 (Fed. Cir. 2013), which recognized two justifications for OTDP: preventing an unjustified time-based extension of patent exclusivity and preventing multiple infringement suits by different assignees asserting essentially the same patented invention. USPTO rules similarly require a terminal disclaimer used to overcome OTDP to preserve common ownership, thereby addressing the latter concern.

The ARP found the anti-harassment rationale independently controlling under existing Federal Circuit law. In In re Fallaux, 564 F.3d 1313, 1318–19 (Fed. Cir. 2009), the Federal Circuit acknowledged that the patent-term-extension rationale had “limited force” but nevertheless affirmed OTDP rejections based on the danger of harassment by multiple assignees. The ARP found Fallaux particularly significant because, as here, the appealed claims had an earlier patent-term filing date and would expire before the reference patent. It rejected the Board’s characterization of the anti-harassment discussion in Fallaux and related cases as immaterial or dicta.

Potential future approach to double patenting. Although bound by existing precedent, the ARP expressed reservations about using hypothetical future harassment as a freestanding basis for OTDP during examination. It said that, absent evidence of actual ownership splitting and multiple lawsuits, such concerns could amount to speculation and could force applicants to accept terminal disclaimers based on events that might never occur. The panel also recognized concerns raised by amici that applying the doctrine in this manner could discourage follow-on research and collaboration by allowing later-developed improvements to create double-patenting problems for earlier foundational inventions.

The ARP proposed a possible future framework, contingent on further Federal Circuit guidance, that would focus principally on preventing unjustified extensions of patent exclusivity. For patents from different families, examiners could generally use patent term filing dates as surrogates for expiration dates. Within the same family, actual filing dates would assume greater importance under Allergan. The panel nevertheless emphasized that, unless the Federal Circuit changes or clarifies the law, USPTO examiners must continue applying the anti-harassment rationale under existing OTDP precedent.

Guidance to USPTO personnel. The ARP separately directed USPTO personnel to continue following pre-Allergan OTDP practice under MPEP § 804 unless Allergan applies. That exception requires the application or patent and the OTDP reference to belong to the same family and have the same patent-term filing date. At the same time, the claims under examination must be first-filed, first-issued, and later-expiring. The ARP explained that the exception would rarely arise during original examination because an examiner ordinarily could not know whether pending claims would ultimately satisfy those conditions.

The ARP accordingly reversed the Board’s Appeal Decision and Rehearing Decision and affirmed the examiner’s OTDP rejections of claims 1–18.

The Case is No. 2024-002920.

Judge: Squires, J.

Attorneys: (Wolf, Greenfield & Sacks, P.C.) for Sanofi, Jessica Hope Roark for the USPTO.

Cases: Patent USPTO