Doctrine of Equivalents Is Strong Patentee Tool, but Needs Care

The doctrine of equivalents, or DOE, provides for infringement of patent claims that aren’t literally infringed. As the US Supreme Court explained in Graver Tank & Mfg. Co. v. Linde Air Products Co. more than 75 years ago, the doctrine prevents “the unscrupulous copyist” from making “unimportant and insubstantial changes” that would otherwise place copied inventions “outside the claim, and hence outside the reach of law.”

DOE is evaluated using one of two tests. The “insubstantial differences” test assesses whether a claim limitation is insubstantially different from the accused product/process. The “function-way-result,” or FWR, test assesses whether the limitation and corresponding feature of the accused product/process perform substantially the same function, insubstantially the same way, to achieve substantially the same result.

Recent Federal Circuit and district court decisions often have rejected DOE theories for avoidable reasons. The decisions below highlight how patentees can avoid common traps.

Be true to a claim limitation’s context in the patent. The DOE inquiry is informed by “[a]n analysis of the role played by each element in the context of the specific patent claim.” Patentees often get tripped up by ignoring this maxim when formulating DOE theories or pursuing infringers’ theories untethered to the claim.

Last month, the US Court of Appeals for the Federal Circuit in Wonderland Switzerland AG v. Evenflo Co., Inc. rejected DOE that was argued based on “overall mechanism” rather than individual elements. In November, the Federal Circuit in Smartrend Mfg. v. Opti-Luxx Inc. rejected DOE under the FWR test where patentee’s expert “contradict[ed] the patent’s description of the [claim’s] function.”

Carefully select the scope of your DOE claim limitation. The success of DOE assertions often turns on how broadly the claim limitation is evaluated. In Alcon Inc. v. Padagis Israel Pharms. Ltd. last year, the US District Court for the District of Delaware rejected, for DOE purposes, treating a polyol limitation—including both composition and concentration requirements—in parts rather than as a whole.

Provide “particularized testimony and linking argument” of equivalence. In several recent Federal Circuit cases, conclusory testimony unlinked to aclaim limitation proved fatal to DOE.

For example, in Lab’y Corp. of Am. Holdings v. Qiagen Scis., LLC, the patentee’s evidence was “not exceptional” and did “not rise to the level of ‘particularized testimony and linking argument.’” In Nexstep, Inc. v. Comcast Cable Commc’n, LLC, the patentee’s expert provided “‘because I said so’ testimony” on the function prong, a “word salad” on the way prong, and a result that was “too generalized, unclear, and unconnected to the claimed invention.” And in Galderma Labs., L.P. v. Lupin Inc., the abbreviated new drug application product’s bioequivalence was insufficient for the insubstantial differences test or FWR test.

Don’t wait to raise DOE. Untimely disclosure of a DOE claim, or defenses to it, can be problematic. In Vytacera Bio, LLC v. CytomX Therapeutics, Inc., the District of Delaware ordered dismissal of the complaint, with leave to amend, that did “not plausibly allege literal or DOE infringement.” And in Bausch & Lomb Inc. v. SBH Holdings LLC, the court found untimely disclosure of disclosure-dedication defenses to DOE stricken under Rule 37(c).

Understand vitiation; it may not be what you think it is. Judge William Bryson, sitting by designation from the Federal Circuit, observed in Prolitec Inc. v. ScentAir Tech., LLC that “[v]itiation is a doctrine with a troubled history.” He noted that vitiation is a legal determination that no reasonable juror could conclude that the asserted equivalent satisfies either test for equivalence, rather than a threshold exception to the DOE.

The District of Delaware in Baxter Healthcare Corp. v. Nevakar Injectables, Inc. agreed and rejected a vitiation defense last March based simply on whether the allegedly equivalent element is the “antithesis” or “opposite ”of what is claimed. The same court, however, granted summary judgment of no DOE in XMTT, Inc. v. Intel Corp.in 2023, primarily because the accused equivalent was the “antithesis” of, and would thus vitiate, the claim limitation.

Be careful what you say during prosecution. A patentee’s words while obtaining a patent can be used against it when asserting DOE. To minimize risk, patentees should try to avoid narrowing amendments, provide focused explanations if amendments are made, and avoid broad statements about what the claims require or exclude. For example, the Federal Circuit held in Colibri Heart Valve LLC v. Medtronic CoreValve, LLC last July that prosecution history estoppel—where the patent’s scope narrowed by canceling a closely related claim—barred application of DOE.

The decisions above show that courts closely scrutinize how and when DOE is asserted and reject theories that are untethered, late, or thinly supported. But they also suggest that DOE can be a powerful tool for patentees when DOE theories are carefully tied to claim language and supported with particularized evidence.

This article does not necessarily reflect the opinion of Bloomberg Industry Group, Inc., the publisher of Bloomberg Law and Bloomberg Tax, or its owners.

Author Information

Todd L. Krause, partner in Morrison Foerster’s IP litigation group, has litigated pharmaceutical patents for nearly three decades and has represented clients asserting infringement under the doctrine of equivalents.

Alyssa B. Monsen, partner at Morrison Foerster, is an IP litigator with extensive experience representing innovator pharmaceutical companies in life sciences patent litigation.

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