Devices and the doctrine

The role of the doctrine of equivalents in assessing the value of, and risks associated with, US medtech patents is often overlooked. Christopher Bright and Nathan Smith of Morgan Lewis report.

Medtech—and its resultant impact on global healthcare—could not be more urgently needed than now. Benefiting from the convergence of medical and technological advances, medtech promises not only new medical devices, diagnostics and treatments, but also new channels for more effectively delivering healthcare, all with better outcomes.

But the promise of medtech can be realised only if there is sufficient incentive to develop medtech, which requires a clear understanding of the extent of the exclusivity and value of the medtech patent portfolio landscape. 

To gain that clear understanding medtech innovators assessing the value of their patent portfolios, and medtech implementers assessing their patent infringement risk, must consider the role that the doctrine of equivalents (DoE) plays in assessing medtech patents in the US.

Beyond the wording of the claims, medtech patents may, or may not, cover substantially the same technology under the DoE. Understanding the nuanced DoE framework is therefore crucial to assessing the value of medtech patents to innovators and the risks of medtech patents to implementers.

With the renewed visibility of the DoE at the US Supreme Court through a number of petitions, which will be discussed later, it is important to consider the issues raised by DoE for medtech patents.

For the purposes of this article, “medtech” is used in a broader sense than just the incorporation of technology into medical devices. The issues addressed in this article also apply to other medical applications as well.

New competition, patent valuation and risk

The future of medtech will bring substantial growth in demand, innovation and sales. The compound annual growth rate for medical device sales could be as much as 5.2% through 2030, with almost $800 billion in forecast global sales and about $300 billion forecast sales in the US alone, according to KPMG.

As more technologies converge with medical devices to become medtech implementations, medtech faces new issues of competition, patent valuation and risk assessment not historically faced by medical devices alone. Historically, medical devices occupied about 7% of patent cases, while computer hardware/electronics, software and telecoms occupied collectively about 28% of patent cases.

By incorporating technology, medtech can be expected to increase in patent valuation and risk assessment issues. With many active-technology patent owners, both large and small, medtech implementers can expect to face increased patent assertion activity and litigation risks due to the incorporation of technology already applied in other industries.

For example, utilising the technology of the internet of things (IoT), medtech can expect to experience patent litigation-related issues like other industries that are now incorporating IoT technology including cellular standards, such as the automotive industry.

Although on their own, technology patents may not have performed historically as well as medical device patents in terms of damages awards and patent owner success rates, medtech patents may provide greater appeal for patent owner assertions of higher valuations due to the synergistic combination of medical devices and technology.

”Utilising the technology of the internet of things (IoT), medtech can expect to experience patent litigation-related issues like other industries that are now incorporating IoT technology.”
Christopher Bright
Nathan Smith

A vital role

Perhaps too often overlooked is the role of the DoE in assessing the value of and risks associated with medtech patents. In addition to the literal scope of the patent (as determined by the exact wording of its claims), when applicable, the DoE operates to expand the patent coverage to encompass “substantially the same” subject matter, ie, “insubstantial differences” will not avoid the patent’s coverage (Mylan v Aurobindo Pharma, 2017).

Assessing the value of medtech patents for innovators or the risk of medtech patents to implementers thus requires assessing the availability of the DoE. This is especially true as the DoE plays a larger role due to the increased pace of medtech development and the need to determine whether those developments are substantially the same as what is patented. 

First, it is foundational that the DoE must be assessed at the claim element level (not the claim overall) so that no claim element is entirely vitiated by application of the DoE to that element.

Second, during interactions with the US Patent and Trademark Office (USPTO) when applying for the patent (the so-called prosecution history, contained in the file wrapper), the patent applicant may have surrendered the alleged equivalent to the public, either by amending the claim, or by arguing why the claim should be granted over prior art. Third, the DoE cannot be asserted to “encompass, or ensnare, the prior art”. These are the most often applied limitations, but there are yet other limitations on the DoE.


In practice, limitations on the application of the DoE to medtech patents will be determined by the patent itself including the wording of the claims, the nature of the alleged equivalent, and the USPTO file wrapper that gave rise to the patent.

For example, in a case concerning a cancer drug, a claim amendment narrowing an “antifolate” to a “pemetrexed disodium” surrendered only certain antifolates (ie, those other than pemetrexed) because the amendment was trying to avoid only non-pemetrexed antifolates in the prior art (Eli Lilly v Hospira, 2019).

In that case, as in other pending cases, the alleged infringer is seeking Supreme Court review to hold that the DoE is inapplicable when the patent owner never explains its rationale for narrowing the claim language during prosecution in the USPTO.

The alleged infringers argue that the Supreme Court should hold that a lack of explanation by the patent owner undermines the public notice function of the patent’s prosecution history and discourages innovation because the scope of the DoE is unclear without such explanation. Those pending cases could have a substantial impact on the scope of the DoE for all patents.

”Medtech implementers interested in lowering the risk profile for their medtech implementation should be mindful of the DoE when conducting due diligence and patent clearance.”

Medtech patent strategy

Whether a medtech innovator or implementer, there are a number of questions that should be asked and answered in assessing the DoE for medtech patents. These questions are merely exemplary and certainly not exclusive.

First, concerning the patent’s teachings for equivalents, one should ask whether the patent specification discloses examples with a substantially similar functionality or result? Second, concerning the patent’s prosecution history, does any prosecution history amendment or argument surrender the alleged equivalent?

Third, concerning ensnarement, does the proposed equivalent as a whole read on the prior art? Fourth, concerning the disclosure-dedication doctrine, does the claim limitation have an alternative that is disclosed in the patent’s specification but unclaimed and therefore which is dedicated to the public?

Fifth, concerning vitiation, does application of the DoE to the proposed equivalent effectively eliminate the claim limitation?

Medtech implementers interested in lowering the risk profile for their medtech implementation should be mindful of the DoE when conducting due diligence and patent clearance, and especially when obtaining an opinion from outside counsel on known patents of substantial concern. Those opinions should address the DoE to reduce the risk of a finding of wilful infringement and enhancement of damages.

After the Supreme Court’s Halo Electronics v Pulse Electronics (2016) decision—indicating that wilful infringement is based on the totality of circumstances but is reserved for egregious case—infringement findings by juries have increased, but the damages enhancement by judges has somewhat decreased. The opinion should be timely, competent, and rendered by qualified patent counsel.

The DoE for medtech patents presents both opportunities to add value to medtech innovators’ patent portfolios and aid in enforcement efforts, and risks to medtech implementers as they strive to navigate the medtech patent landscape.

As the pace of medtech development picks up and the medtech patent landscape increases, we can expect to see a larger role for the DoE in balancing the interests of medtech innovators who would like to get value from insubstantial changes to their innovations, while medtech implementers actively seek to reduce their risk presented by the DoE.

The DoE thus presents opportunities and risks for those in medtech, and now is the time for innovators and implementers to thoughtfully incorporate the DoE into their IP strategy.

Christopher Bright is a partner at Morgan Lewis. He can be contacted at:

Nathan Smith is a partner at Morgan Lewis. He can be contacted at:

Image: Envato Elements / sfam_photo

Autumn 2020

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