What U.S. Patent Holders Need to Know About Inequitable Conduct Right Now

If a court finds that a patent applicant intentionally misrepresented or withheld material information from the USPTO with the intent to deceive, the consequences are severe, leading to unenforceability of the entire patent (and likely any later patents claiming priority to the unenforceable patent).

What Is Inequitable Conduct?

As the U.S. Court of Appeals for the Federal Circuit famously said in its landmark en banc decision in Therasense, Inc., v. Becton Dickinson and Co., 649 F.3d 1276 (Fed. Cir. 2011), the inequitable conduct defense is ”the ‘atomic bomb’ of patent law.” To establish inequitable conduct, an accused infringer must prove by clear and convincing evidence that the applicant misrepresented or omitted material information with the specific intent to deceive the USPTO.

In Therasense, the Federal Circuit tightened both the materiality and intent requirements, aiming to curb overuse.

Consequences of Inequitable Conduct Finding

A finding of inequitable conduct can have wide-ranging effects on a patent portfolio:

• Entire patent unenforceability: Inequitable conduct renders all claims of a patent unenforceable, even if the conduct related to only one claim. Id.
• Portfolio-wide exposure: The taint of inequitable conduct can spread to related patents in the same family. Id.
• Attorneys’ fees: A finding of inequitable conduct can contribute to a case’s being deemed “exceptional,” potentially supporting an award of attorneys’ fees under 35 U.S.C. § 285. Id.
• Impact on licensing agreements: A patent rendered unenforceable due to inequitable conduct cannot serve as the basis for a valid license. Existing licensees may seek to terminate or renegotiate agreements.
• Diminished portfolio value: Because inequitable conduct can render related patents unenforceable and invite scrutiny of an applicant’s prosecution practices more broadly, a finding of inequitable conduct may reduce the value of an organization’s patent portfolio.

The Two Required Elements

To establish inequitable conduct, a defendant must prove two required elements: (1) but-for materiality and (2) specific intent to deceive.

1. But-For Materiality

A prior art reference or withheld information is but-for material if the U.S. Patent and Trademark Office (USPTO) would not have allowed a claim had it been aware of the undisclosed information. Aventis Pharma S.A. v. Hospira, Inc., 675 F.3d 1324, 1334 (Fed. Cir. 2012). But-for materiality is the standard for evaluating the materiality prong of the inequitable conduct analysis, unless there is affirmative egregious misconduct. Id. In making this patentability determination, i.e., whether the USPTO would have allowed the claim had it been aware of a withheld reference, for example, the court applies a preponderance of the evidence standard and gives claims their broadest reasonable construction, consistent with the standards the USPTO itself applies during prosecution. Therasense, 649 F.3d at 1292-93.

When the conduct rises to the level of affirmative egregious misconduct, such as filing a false affidavit, the misconduct itself is treated as material, regardless of but-for materiality. Id. 

2. Specific Intent to Deceive 

Intent to deceive is an independent element of inequitable conduct and must be independently established by clear and convincing evidence. Astrazeneca Pharms. LP v. Teva Pharms. USA, Inc., 583 F.3d 766, 776 (Fed. Cir. 2009). Evidence of mistake or negligence, even gross negligence, is not sufficient to establish the requisite intent. Id. Intent and materiality are separate requirements; courts may not apply a “sliding scale” or infer intent solely from a high degree of materiality. Therasense, 649 F.3d at 1290.

This last point, the prohibition on a sliding scale, was among the most significant changes Therasense introduced, and it explains why the defense, while potent, may be difficult to establish. Because direct evidence is rare, intent may be inferred from circumstantial evidence; but to meet the clear and convincing standard, deceptive intent must be “the single most reasonable inference” that can be drawn from the evidence; if multiple reasonable inferences exist, the required intent cannot be found. Therasense, 649 F.3d at 1290-91.

Recent Case Examples

Three recent decisions confirm that notwithstanding the Federal Circuit’s attempt in Therasense to rein in assertions of the defense, inequitable conduct remains a viable and very powerful defense given the right factsz

Inline Plastics Corp. v. Lacerta Grp., Inc., 810 F. Supp. 3d 148 (D. Mass. 2025)

After a bench trial, the court held that the defendant proved by clear and convincing evidence that the patentee’s failure to name joint inventors was material, that the patentee acted with specific intent to deceive the USPTO by omitting its collaborators as inventors, and that the patents were therefore unenforceable. The court’s conclusion on specific intent, as “the single most reasonable inference,” rested on the overall record, including the timing of events, the patentee’s cessation of contact with the collaborators before filing, and credibility findings against key witnesses.

However, the court rejected a separate theory that the patentee’s statements about a prior art reference during prosecution constituted inequitable conduct, finding the defendant failed to prove but-for materiality and failed to identify a specific individual who acted with the requisite intent to deceive.

The split outcome underscores both sides of the post-Therasense picture: the doctrine is rigorous, but when intentional inventorship misconduct can be proven on the record, it remains capable of rendering patents unenforceable.

Glob. Tubing LLC v. Tenaris Coiled Tubes LLC, 167 F.4th 1357 (Fed. Cir. 2026)

The Federal Circuit vacated the district court’s grant of summary judgment of inequitable conduct and remanded, holding that genuine disputes of material fact precluded summary judgment on both elements. The court found that the district court failed to view the record in the light most favorable to the nonmovant and that a genuine dispute existed as to whether deceptive intent was “the single most reasonable inference” from the evidence. The Federal Circuit also found a genuine dispute on whether the withheld documents were independently material or instead cumulative of already-cited prior art, further precluding summary judgment.

This decision is a reminder of how difficult inequitable conduct is to resolve at summary judgment when intent turns on disputed inferences and credibility, and of how carefully courts apply the Therasense framework at every stage of litigation.

Equil IP Holdings LLC v. Akamai Techs., Inc., 722 F. Supp. 3d 450 (D. Del. 2024)

The court dismissed the inequitable conduct defense at the pleading stage, finding that the defendant’s allegations were insufficient to plead either the materiality of the applicant’s conduct before the USPTO or that the applicant had the intent to deceive. To survive a motion to dismiss, a pleading of inequitable conduct must identify the specific “who, what, when, where, and how” of the material misrepresentation or omission committed before the USPTO, and must include sufficient underlying facts from which a court may reasonably infer that a specific individual knew of the withheld material information and withheld it with a specific intent to deceive.

Together, Global Tubing and Equil IP Holdings confirm the high threshold Therasense imposes, but neither diminishes the significance of Inline Plastics, which shows the doctrine very much alive and operative when the record supports it.

Key Takeaways

For patent holders, these cases underscore the importance of:

• Thorough and candid disclosure during prosecution, including complete inventorship identification and timely submission of all material prior art.
• Careful litigation strategy, when inventorship or prior art disclosure issues exist in the prosecution history, inequitable conduct is a defense that should be taken seriously, both in asserting patents and in evaluating exposure when adverse parties are involved.
• Analysis of an entire patent family when litigation is contemplated, not just the patent(s) identified for assertion, since a finding of inequitable conduct in one patent can affect related patents and applications.