- with readers working within the Insurance industries
In our January Newsletter (here) we reported on the non-precedential Federal Circuit decision in Daiichi Sankyo Co. v. Seagen Inc., Fed. Cir. Dec 02, 2025, appeal 2023-2424, holding that Seagen’s U.S. Patent 10,808,039 (‘039) was invalid for lack of written description and enablement, over turning a jury verdict and JMOL to the contrary. This was the second time in a two-week period that the Court had overturned jury verdicts in favor of the patentee on written description. As the Court recognized in the earlier decision Duke Univ. et al. v Sandoz, Inc., 160 F.4th 1305 (2025) “a district court’s refusal to grant judgment as a matter of law may be reversed only if the evidence is such that without weighing the credibility of the witnesses the only reasonable conclusion is in the moving party’s favor.” This is a high burden to meet.
In Daiichi the defenses were lack of written description and enablement, both fact-based defenses where high burden exists to overturn a denial of JMOL. Neither Federal Circuit nor the district court provided a claim construction for the patent. Had a proper claim construction been performed, the Court would have recognized that the claims were invalid as a matter of law, since the claim defined the drug solely in functional language is a question for the court only. The claim in part read:
wherein the drug moiety is intracellularly cleaved in a patient from the antibody of the antibody-drug conjugate
There was no description in the patent specification describing the drug’s properties, how the drug is to be cleaved such as lysosomal protease cleavage, acid-labile cleavage, reduction-sensitive cleavage, enzymatically, metal-dependent oxidative cleavage, or biorthogonal. There is no description of how to select the linker to accomplish the linking of the drug and antibody without premature release or a failure to release the drug or bind to the target; nor is there any description of the substituents which provide the cleavability in vivo but allow the drug to remain effective and stable until it delivers the drug to the target. All are dependent on the target tissue/disease, drug, and linker. Further the scope of the claim effectively preempted activity from later developers being able to employ future developments without fear of infringement no matter how different the development was from those taught and claimed in the ‘039 patent. Such preemption has long been held by the Supreme Court to be impermissible in U.S. patent law.
Functional claiming was prohibited beginning with Whittemore v. Cutter, 29F. Cas. 1120, 1122 (No. 17,600) (CC Mass. 1813) (Story, J.) where Justice Story sitting as a circuit court judge, held that “[A] patent can, in no case, be for an effect only, but for an effect produced in a given manner, or by a peculiar operation.” Further the Court has held that the Constitution’s patent provision prohibits patents which claim an invention by function only:
A patent is not good for an effect, or the result of a certain process, as that would prohibit all other persons from making the same thing by any means whatsoever. This, by creating monopolies, would discourage arts and manufactures, against the avowed policy of the patent laws. Le Roy v. Tatham, 55 U.S. 156, 175 (1852) [Emphasis added]
The constitution provided for patents “To further the progress of the useful arts.” This same concept was used to invalidate claims in the Morse patent, O'Reilly v. Morse, 56 U.S. 62, 112 (1853) to the telegraph with repeater units where the claim had only a single means claim:
And if he can secure the exclusive use by his present patent, he may vary it with every new discovery and development of the science, and need place no description of the new manner, process, or machinery, upon the records of the patent office. [Emphasis added]
A similar effect was set forth in the Incandescent Lamp Patent, 159 U.S. 465 (1895) where the claims were to “an illuminating loop “consisting of carbon made from a fibrous or textile material” where the patentee enabled carbonized paper only. The Supreme Court held:
[to] shut out any further efforts to discover a better specimen of that class than the patentee had employed, would be an unwarranted extension of his monopoly, and operate rather to discourage than to promote invention.[Emphasis added]
Morse and Incandescent Lamp were cited as recently as 2023 by Justice Gorsuch in Amgen v. Sanofi.
Congress added the means plus function provision in the 1952 patent act to provide a way for functional claiming to survive the Halliburton Oil Well Cementing Co. v. Walker, 329 U.S. 1 (1946) decision by requiring the specification to provide a description of the means for performing the function. The ‘039 patent omitted any discussion of the means for achieving the drug’s function of intracellular cleavage in a patient. Thus, the ‘039 as matter of law was invalid which would have avoided the controversy created by overruling a jury verdict on a factual dispute. Had the Court performed a proper claim construction the invalidation would have been as a matter of law which is the sole province of a court where the jury with limited exceptions has no role. See Berkheimer v. HP Inc., 881 F.3d 1360 (2018).
The controversy created by the decision could have been avoided had a proper claim construction been performed and the court decided the threshold question of whether the claim was patent eligible. For those preparing patent applications, review your claims carefully so that they do not improperly define the invention by relying on function only.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
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