The OTDP Havoc Continues: Ex parte Baurin, Baumeister, and the Doctrine That Refuses to Make Sense
I first fell in love with the doctrine of obviousness-type double patenting (kind of a sad admission) when working on Lilly Prozac[1]. I knew it was a weird doctrine. But certainly, I naively believed, there is some sort of subtle unifying theory. Not so much.
Obviousness-type double patenting (“OTDP”)—the doctrine that patent practitioners love to hate—is back in the spotlight, and this time it's brought friends, enemies, and an audience of confused onlookers. The Patent Trial and Appeal Board's (“PTAB”) decision in Ex parte Baurin[2] has kicked off what may be the next seismic shift in OTDP law, and the USPTO Director has convened the rarely used Appeals Review Panel (“ARP”) to sort out the mess.
The Baurin Decision: What Happened
In November 2024, the PTAB reversed five OTDP rejections in U.S. Application No. 17/135,529 (a Sanofi antibody application), finding that later-filed, later-expiring unrelated patents cannot serve as proper OTDP references. The Board relied on the Federal Circuit's 2024 Allergan v. MSN Labs. decision[3], which held that "a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim having a common priority date." Here's the twist: Allergan involved patents within the same priority chain; Baurin does not. The Board acknowledged this but found Allergan's "reasoning compelling" anyway.
The Examiner—gutsy move—filed a Request for Rehearing. A reconstituted panel denied it 2-1, with the majority dismissing the Examiner's reliance on the MPEP, noting that the MPEP "cannot create new law or ignore the law."
Enter Baumeister: The PTAB Disagrees with Itself
Another PTAB panel in Ex parte Baumeister[4] confronted overlapping facts and somehow reached the opposite conclusion, finding that the anti-harassment rationale independently supports OTDP rejections even where reference patents have later filing and expiration dates—a conclusion that confuses a secondary policy concern with the doctrine's core purpose. The Baumeister panel distinguished Baurin because Baumeister involved patents with different ownership, but that doesn't change the fundamental absurdity of using a later-filed, later-expiring patent to invalidate an earlier-filed, earlier-expiring one. The applicant appealed to the Federal Circuit in January 2026, and rightfully so.
Two PTAB panels, overlapping facts, opposite outcomes. Can both panels be right?
The Tension: Can These Decisions Be Reconciled?
In a word? Barely. The Baurin panel treats Allergan as a broad principle: the earlier-filed instrument "sets the maximum period of exclusivity" and cannot be attacked by a later-filed reference. The Baumeister panel treats Allergan as a narrow exception and defers to Fallaux[5] and Hubbell[6] for cross-family situations. Professors Lemley and Ouellette characterize Baurin's broader reading as "irreconcilable with Fallaux and Hubbell." But perhaps it is Fallaux and Hubbell—decided in 2009 and 2013 under very different doctrinal conditions—that are overdue for reconsideration, not Allergan.
The Baurin panel correctly identified the Federal Circuit's anti-harassment rationale as "dicta at best,” noting that Fallaux and Hubbell never squarely addressed whether later-filed patents were proper OTDP references. Lemley and Ouellette protest that treating this rationale as dicta "would require concluding that the Federal Circuit affirmed these OTDP rejections on no ground at all," but that may say more about the weakness of those holdings than about Baurin's reasoning. Amicus Anthony Prosser bolsters the point, noting that "[o]ver a dozen judges" since Allergan have reached the same conclusion as Baurin, calling it "a consensus interpretation of the Allergan decision."
In Defense of Sanofi
Sanofi has crafted an eminently reasonable position: the purpose of OTDP is to prevent companies from using new patents to extend the life of existing ones. If your applied-for patent expires before its so-called reference, exactly what "extension" are you pulling off? Is a time machine involved? It’s a weird world where a doctrine designed to prevent an “unjustified timewise extension of the right to exclude granted by a patent” is used where there is, in fact, no extension.
Sanofi and its industry allies put it more diplomatically: "The Examiner's argument to the contrary asks this panel to turn the OTDP doctrine on its head, wielding a tool designed to prevent extensions of patent term as a weapon to destroy lawfully earned patents." This is less turning a shield into a sword than turning it into a boomerang that hits the patent owner in the face. The amici added that "investment uncertainty" from a patent possibly being invalidated by a newer one "far outweigh[s] the Examiner's hypothetical harassment concern."
The Statutory Forest for the Trees
Jeremy Lowe offers a different lens, arguing the current debate misses the statutory elephant in the room: Sections 101, 154, and 253 mandate "one invention, one patent, one term." Under this framework, all three ARP questions "collapse into one fundamental question: Does OTDP permit duplicative patents with different expiration dates and independent rights?"
The statutory-unity framework has intellectual elegance but a fatal flaw: it would require terminal disclaimers in every case involving patentably indistinct claims, regardless of whether any actual extension or harm exists. That's a recipe for forcing applicants to disclaim patent term they lawfully earned—exactly the outcome Allergan rejected. Simplifying the Examiner's task is a worthy goal, but not at the expense of punishing innovators for the USPTO's own prosecution delays.
The Lemley/Ouellette Counter-Punch
Professors Lemley and Ouellette filed an amicus brief supporting the Examiner, arguing Allergan is narrow and inapplicable to Baurin's cross-family facts. Their empirical work notes that terminal disclaimers are filed for over 15% of all patents, over 50% of litigated patents, and over 60% of FDA-approved drug patents. The specter of pharmaceutical patent thickets looms large in their brief, though "patent thicket" is doing a lot of rhetorical heavy lifting. Multiple patents in a portfolio are not evidence of abuse—they're evidence that someone invested billions in R&D. If generic companies face too many patents, the answer lies in patent quality and prior art, not in weaponizing OTDP to strip innovators of lawfully obtained rights.
Bob Armitage's Perspective
No discussion of OTDP reform is complete without Bob Armitage, the former General Counsel of Eli Lilly & Company and architect of the America Invents Act. In an amicus brief during the In re Cellect en banc petition in 2023, Armitage called for a "ground-up rethinking" of OTDP, comparing the opportunity to the Federal Circuit's wholesale reconsideration of inequitable conduct in Therasense. He argued that Cellect "could represent an ideal vehicle—for reasons detailed below—for this Court to undertake a similar policy-focused reconstruction of the law on obviousness-type double patenting." Armitage wasn't asking the court to tinker—he was asking it to tear down the edifice and rebuild.
His critique resonates powerfully here. If two PTAB panels can reach opposite conclusions on the same facts, and the ARP must be convened to sort it out, perhaps the problem is the doctrine itself. A "policy-focused reconstruction" would be a welcome alternative to stacking case-specific holdings like a Jenga tower and hoping nothing collapses.
Where Things Stand Now: Baurin Before the ARP and In re Ablynx Before the Federal Circuit
The OTDP conflict is now playing out on two parallel tracks, and the interplay between them is as important as either proceeding on its own.
Track One: Ex parte Baurin before the ARP. Director Squires convened the Appeals Review Panel to address Allergan's applicability, projected expiration dates, and whether separate-ownership risk independently supports OTDP rejections.
Track Two: In re Ablynx before the Federal Circuit. The Baumeister decision has been appealed under the name In re Ablynx (Ablynx N.V. and Sanofi are the real parties in interest). The appeal addresses "very similar facts as Ex Parte Baurin" but relies on Fallaux and Hubbell—old case law dealing with fact patterns that, as commentators have argued, "largely cease to exist in modern patent practice."
The Conflict in a Nutshell: Baurin correctly holds that later-filed, later-expiring patents from unrelated families cannot serve as OTDP references—full stop—because invalidating an earlier-filed, earlier-expiring application serves no anti-extension purpose and turns the doctrine against the very innovators it was never designed to punish. Baumeister/Ablynx says they can, leaning on the anti-harassment rationale as a standalone basis for OTDP rejections regardless of which patent expires first—a position that elevates a secondary policy concern over the doctrine's fundamental purpose. Same doctrine, same fundamental question, but only one answer that makes sense.
The Coordination Problem. The USPTO sought a 65-day extension in Ablynx, moving the Director's brief due date to August 7, 2026. The proceedings address nearly identical facts, so the USPTO's position in one should directly influence the other. If the ARP upholds Baurin, it would be awkward for the Director to then vigorously argue for expanded OTDP in Ablynx. Some observers have noted the ARP's question-framing may telegraph a reversal of Baurin—one commentator suggested "the intent appears to be for the ARP to find that the Baurin decision is distinguishable from Allergan." If so, Sanofi may have won the battle only to lose the war at the ARP—an ironic twist worthy of a doctrine this convoluted.
The outcome across both proceedings will shape prosecution strategy for years. If Baurin's broader reading of Allergan prevails at the ARP and the Federal Circuit reverses Baumeister in Ablynx, the patent system takes a long-overdue step toward rationality—and Examiners lose a tool they've wielded indiscriminately for far too long.
If the ARP reverses Baurin and the Federal Circuit affirms Baumeister, the anti-harassment rationale lives to fight another day, and innovators who invested billions in R&D will continue to watch lawfully earned patent rights evaporate under a doctrine being applied in ways its creators never intended.
Either way, one thing is clear: OTDP remains one of the most complicated aspects of U.S. patent law. And it's only getting more complicated. Sanofi has the better argument, the better reading of Allergan, and the better policy position. Here's hoping the ARP and the Federal Circuit agree.
Stay tuned for the ARP's decision. We'll be here, terminal disclaimers in hand, rooting for common sense.
This publication and/or any linked publications herein do not constitute legal, accounting, or other professional advice or opinions on specific facts or matters and, accordingly, the author(s) and PierFerd assume no liability whatsoever in connection with its use. Pursuant to applicable rules of professional conduct, this publication may constitute Attorney Advertising. © 2026 Pierson Ferdinand LLP.
[1] Eli Lilly & Co. v. Barr Labs., Inc., 251 F.3d 955 (Fed. Cir. 2001).
[2] Ex Parte Baurin, Appeal 2024-002920, Appl. No. 17/135,529 (PTAB Nov. 6, 2024).
[3] Allergan USA, Inc. v. MSN Labs. Priv. Ltd., 111 F. 4th 1358 (Fed. Cir. 2024).
[4] Ex Parte Baumeister, Appeal 2026-000193, Application 17/409,019 (PTAB Nov. 21, 2025).
[5] In re Fallaux, 564 F.3d 1313 (Fed. Cir. 2009).
[6] In re Hubbell, 709 F.3d 1140 (Fed. Cir. 2013).
[7] In re Cellect, LLC, 81 F.3d 1216 (Fed. Cir. 2023).
