In Colibri Heart Valve, LLC v. Medtronic CoreValve, LLC, No. 2023-2153 (Fed. Cir. July 18, 2025), the Federal Circuit reversed a jury verdict of over $106 million, holding that cancellation of one independent claim during prosecution can create a threshold presumption of prosecution history estoppel (“PHE”) even for another independent claim with no formal relation to the canceled claim where those claims have “close linkage of subject matter” as shown by “intertwined terminology.” The decision highlights the importance of sophisticated patent prosecution strategy and could significantly impact litigation in cases involving the doctrine of equivalents (“DOE”).
Background
Colibri’s asserted patent recites a method for implanting a replacement heart valve that permits the installer to retract a partially deployed valve to correct a problem with its initial positioning. During prosecution, Colibri presented one independent claim requiring partially deploying the valve by “pushing” it out of a sheath of the delivery device. It also presented a separate independent claim describing partial deployment by “retracting” the sheath. The patent examiner rejected the “retracting” claim for lack of written description, and Colibri canceled it. The patent thus issued with the “pushing” claim as its sole independent claim.
Colibri sued Medtronic, a manufacturer of replacement heart valves, alleging that Medtronic induced surgeons to perform its claimed method. Medtronic argued that it did not infringe because its products retract the sheath rather than pushing the valve out. Colibri replied that even if retracting did not infringe literally, it at least infringed under the DOE.
Before trial, Medtronic sought summary judgment that PHE barred Colibri’s DOE theory. Medtronic contended that PHE presumptively applied to bar this DOE theory based on the cancellation of the “retracting” claim during prosecution in response to a patentability rejection. The District Court rejected Medtronic’s PHE argument on two grounds. First, it reasoned that there was no narrowing amendment because the issued claim was separate and distinct from the canceled claim. Second, it ruled that Colibri’s DOE theory was distinguishable from the canceled claim because Colibri’s theory contemplated a combination of pushing and retracting, whereas the canceled claim recited only retracting.
At trial, Colibri abandoned literal infringement and instead pursued infringement solely under the DOE. Colibri contended Medtronic’s method of partially deploying the valve by “retracting” the outer sheath necessarily required a countervailing “pushing” force as a matter of “basic physics,” and that this blend of opposing forces was equivalent to the “pushing” claimed in Colibri’s patent. The jury found induced infringement under this theory and the District Court denied judgment as a matter of law.
The Federal Circuit’s decision
The Federal Circuit disagreed with both reasons the District Court adopted for finding the presumption of PHE inapplicable.
Colibri’s own equivalence theory undercut its argument against PHE
First, the Federal Circuit rejected the argument that the alleged equivalent (retracting and pushing) was distinctly different from the canceled “retracting” claim. Focusing on Colibri’s own equivalence theory at trial, the court reasoned that if “retracting” necessarily required pushing as a matter of “basic physics,” then this combination necessarily also would have been contemplated by the canceled claim.
The independent claims’ formal separateness did not negate estoppel
The Court also rejected the District Court’s reasoning that the two independent claims in prosecution were “separate and distinct,” instead finding that “a relevant artisan would understand the close basic-physics relationship of the cancelled and retained claims” and that “a skilled artisan reading the prosecution history would understand that some narrowing had occurred.” The court held that the cancellation of the “retracting” claim communicated that the scope of the “pushing” claim that ultimately issued had narrowed, presumptively giving rise to PHE. The Federal Circuit thus reversed the District Court, holding that PHE barred the DOE theory underlying the jury’s verdict.
The Federal Circuit explained this result as a natural outgrowth of prior cases focusing the PHE inquiry on what subject matter the patent applicant had in substance abandoned during prosecution, not on the “formalities” of claim relationships. See Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 733 (2002) (“Estoppel is a ‘rule of patent construction’ that ensures that claims are interpreted by reference to those ‘that have been cancelled or rejected.”). For example:
- Honeywell International, Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131 (Fed. Cir. 2004) established that formal narrowing or “amendment” of a claim itself was not required for the presumption of PHE. Cancellation of an independent claim and rewriting a dependent as independent can create PHE because it is functionally equivalent to amending the independent claim to add the limitation from the dependent claim.
- Deering Precision Instruments, LLC v. Vector Distribution System, Inc., 347 F.3d 1314 (Fed. Cir. 2003) applied the same reasoning to find the presumption of PHE applicable where, rather than rewrite a dependent claim as independent, the applicant canceled both and presented a new independent claim substantively identical to the canceled dependent claim.
In light of these cases, the Court observed that “narrowing” was not a purely formal matter involving amendments to a single claim’s terms but instead could exist “as a substantive matter based on cancelling a closely related claim involving such intertwined terminology that cancelling one claim necessarily communicated that the scope of the other claim had narrowed.” This decision goes beyond Honeywell and Deering by applying that underlying “substance-over-form” principle to a claim that was not only never itself amended but was not — in substance or form — a dependent claim being rewritten in independent form.
Possible limits on the court’s holding
- The court’s holding relies on the two independent claims in prosecution being closely related in subject matter, as the patent owner’s own equivalence arguments showed. Had there been greater differences between the canceled “retracting” claim and the issued “pushing” claim — or had the patent owner not itself showed that “pushing” was implicit in “retracting” — the presumption may not have applied.
- The patent owner did not argue that an exception to PHE applied or that the scope of the particular narrowing did not justify estoppel.
- The “retracting” claim was canceled in response to a § 112 written description rejection; there was no dispute that the cancellation was for patentability. Thus, the decision may not apply to claims canceled before examination or for other reasons unrelated to patentability.
Unresolved questions
- How broadly will the “intertwined terminology” standard be applied in future cases? It is common for unrelated independent claims in a single patent (or even in continuation patents) to have similar subject matter and terminology, so a broad reading of Colibri could lead to a significant increase in instances where PHE is raised. The particular facts of this case are fairly narrow, however, with the alleged equivalent being found substantively identical to what was given up in the canceled claim.
- How far will Colibri’s rejection of formalism be extended to other factual contexts? For example, if the “retracting” claim were amended rather than canceled, and supposing the amendment resolved the written description rejection, would the PHE implications have been different? This uncertainty raises the possibility that any claim amendment or cancellation in prosecution could later be scrutinized to determine if “a skilled artisan reading the prosecution history would understand that some narrowing had occurred.”
Takeaways
For patent applicants
- Because a cancellation or amendment for patentability could potentially create PHE even between independent claims with no formal relationship, applicants must be cognizant of what they are giving up whenever they cancel or amend a claim in response to a rejection. Applicants should not assume that PHE will not apply based on the lack of a formal relationship between claims.
- Colibri has mixed implications for continuation practice. On the one hand, because PHE can apply to other patents in the same family, it could limit the ability to rely on the DOE when later asserting claims from a continuation patent. Ultimately, however, Colibri makes continuation practice more important as a way to obtain claims that literally cover the technology’s commercialization and avoid the need to rely on the DOE.
For litigants
- For infringement plaintiffs, Colibri further complicates the ability to rely on the DOE by extending the risk of PHE even to claims that were not themselves ever amended or rewritten. Litigating exceptions to PHE may be a way to avoid this pitfall in some cases, but cases finding those exceptions applicable are rare. This increases the importance of claim construction to avoid the need to rely on DOE, as the patent owner unsuccessfully sought to do in this case.
- These facts illustrate the tension between establishing equivalence as a factual matter and avoiding a presumption of PHE in cases involving cancellation of claims similar to the accused product. Litigants relying on the DOE should take care to frame the alleged equivalent in a way that is distinguishable from any canceled claims.
- For infringement defendants, Colibri provides greater opportunities to credibly raise PHE in response to an assertion of DOE. This necessitates a deep dive into the prosecution history of both the asserted patent and its family, and analysis of all potentially relevant claim amendments or cancellations.
