USA Trends and Developments Contributed by: Matthew D Powers, Samantha Jameson, Azra Hadzimehmedovic and Aaron Nathan, Tensegrity Law Group LLP
claims covered 81). In both cases, juries found the written description requirement met, and the district court denied a motion for judgment as a matter of law that the patents were invalid for an insufficient written description. Duke , 2025 LX 578815, at *4; Sea- gen , 2025 LX 511083, at *1-2. Despite the “doubly high” burden of showing “no reasonable jury could have failed to conclude that” invalidity was shown “by clear and convincing evidence,” the Federal Cir ‑ cuit reversed in both cases and concluded the claims were invalid based on lack of written description. Duke , 2025 LX 578815, at *6, *22; Seagen , 2025 LX 511083, at *2. In both cases, the specific members of the claimed subgenus were not listed in the patents’ specifications. Duke , 2025 LX 578815, at *9; Seagen , 2025 LX 511083, at *6-7. In both cases, the court con ‑ sidered whether there were sufficient “blaze marks” in the specification to single out the claimed subgenus within the broad disclosed chemical genus analogous to the way “blaze marks” had been used to “mark trails” and single out “particular trees” in a forest. Sea- gen , 2025 LX 511083, at *19 (emphasis omitted); Duke , 2025 LX 578815, at *10. But the reasons there were no sufficient blaze marks differed in the two cases. Duke focused on the importance of preferred embodi ‑ ments in the written description analysis and the com ‑ binatorial effect of having chemical structures with multiple positions at which various chemical groups may be selected. The patent owner argued that there were only “13 options” for one of the variable posi ‑ tions in the specification’s disclosed chemical struc ‑ ture in an effort to narrow the scope of the disclosure. The court rejected that argument and noted that there was instead a “path with 13 branches” with “most of those branches lead[ing] to additional branches, yield ‑ ing in the end a vast number of options.” Duke , 2025 LX 578815, at *13. The claimed subgenus was one of those 13 branches with the selection of a specific sub- branch within it. Id. at *3, *13-14. The claimed main branch of the 13 was not one of the preferred embodi ‑ ments, even though the claimed sub-branch within it was identified as preferred. Id. at *3, *16-17. The court concluded that the non-selection of the claimed main branch as a preferred embodiment affirmatively “direct[s] a skilled artisan away from” the claimed sub ‑ genus and would thus lead those of ordinary skill to conclude the inventors “did not actually possess what
they claimed.” Id. (emphasis original). The patentee did not identify “any persuasive reason” why one of ordinary skill would “ignore[]” the blaze marks “direct ‑ ing her away from” the claimed branch and then “fol ‑ low the blaze marks” within the “non-preferred group” (the branch) to select the sub-branch within the main branch. Id. at *3, *17. This was also not the only time the issue arose. There was a second variable posi ‑ tion at which one could select from “eight categories” of chemical structures, and even though the claimed selection was the “most preferred” option within one of the eight categories, there was neither direction to select the claimed one of the eight categories nor to include both this claimed structure and the structure described above in the same molecule. Id. at *3, *19- 20. In Seagen , a different fact pattern proved critical and confirmed the importance of inventor and expert tes ‑ timony. There, the plaintiff’s application with the broad genus was filed in 2004, the defendant’s drug disclosed a specific structure in 2015, and then the plaintiff’s con ‑ tinuation application claiming the subgenus including the structure in the defendant’s drug was filed in 2019. Seagen , 2025 LX 511083, at *8-9. The court noted that “[o]ne cannot avoid the suspicion” that the 2019 application was “filed specifically to encompass” the defendant’s drug, “which of course is permissible if it was entitled to a filing date antedating any public disclosure” of that drug. Id. at *7. But that was found not to be the case, and that result was supported by key inventor and expert testimony. The lead inventor “admitted” that the “first time he ever saw” the claimed structure was in the defendant’s drug, and the testi ‑ mony of the other inventors was “similar.” Id. at *17- 18 (internal quotation marks omitted). The patentee’s expert testified that it was a “straightforward leap” from the structures in the specification to the claimed structure, but this testimony was “self-defeating” and “doom[ed]” the patentee’s case because “[t]hat which one must leap to is obviously not there.” Id. at *19-20. The Regeneron case also focused on the importance of key testimony regarding what one of ordinary skill would understand but reached a very different result based on very different testimony. Regeneron affirmed a district court’s determination that there was no substantial question of invalidity based on lack of
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