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Should a PHOSITA be defined by the specification or by the claims?

Pu-Cheng (Leo) Huang

Editors: Bob Yoches & Amanda Murphy


I. Introduction

An inventor cannot obtain a patent for an invention that is obvious to a “person having ordinary skill in the art” (“PHOSITA”) but courts continue to struggle with the question of whether the relevant person should be identified in light of the invention disclosed in the specification or the invention claimed. In a recent IPR decision, the PTAB adopted the former approach. Axonics Modulation Technologies, Inc. v. Medtronic, Inc., IPR2020-00715, (PTAB Sep. 13, 2021). This article considers the PTAB’s analysis and suggests that the claims should be the proper measure for determining who is a PHOSITA.

II. The Medtronic IPR

After Drs. Schmidt and Tanagho observed that stimulation of the sacral nerves could alleviate various pelvic floor disorders, they obtained U.S. Patent No. 8,036,756, relating “to an implantable medical electrical lead […] for stimulation of a bundle of sacral nerve fibers.”[1]

Axionics filed a petition for inter partes review (IPR) asserting that certain claims of the ’756 patent were obvious over Young, Gerber, and two other references.[2] Patent Owner argued in response that a properly-defined PHOSITA would have had no motivation to combine Young with Gerber or with the other references.[3]

Petitioner contended that a PHOSITA would have had experience in implantable medical devices (a bachelor’s degree in biomedical engineering (or similar) and experience researching implantable medical devices), [4] but Patent Owner proposed a definition of a PHOSITA as having experience in sacral neuromodulation (a physician with specialist experience in sacral neuromodulation), or in implantable medical lead design with experience in sacral neuromodulation and who would have worked closely with a physician in sacral neuromodulation.[5] Patent Owner criticized Petitioner’s proposed level of skill because it required no understanding of the sacral anatomy or sacral neuromodulation, which the Patent Owner argued was required based on the context of the ’756 patent.[6] Petitioner responded that the challenged claims do not recite sacral anatomy or sacral neuromodulation, and so a PHOSITA would not have required such experience to understand and practice the claimed invention.[7]

The Board agreed with Patent Owner’s definition of PHOSITA.[8] It reasoned that the specification of the ’756 patent defined the field of the invention as medical electrical leads for sacral neuromodulation, and the specification described the invention with respect to the sacral anatomy.[9] The Board found “the claims’ lack of a recitation of sacral anatomy or sacral neuromodulation does not override the specification’s express description of the field of the invention.”[10] According to the Board, “the claims’ purpose is not to describe the subject matter of the patent but rather to define the boundary of the patent monopoly.”[11] Because the Board determined that a PHOSITA would have had experience researching and developing medical leads for sacral neuromodulation,[12] it agreed with Patent Owner that a PHOSITA would have had no reason to combine Young with Gerber, so the claims of the ’756 patent were not unpatentable.[13]

III. Discussion

A. The Board’s Holding

In a typical case, the patent owner advocates for a less knowledgeable PHOSITA because “the higher the level of skill that a [PHOSITA] possesses, the more likely that a given variation from the prior art could be achieved by that [PHOSITA].”[14] In this case, however, Patent Owner asked the Board to use a higher standard for the PHOSITA than what Petitioner proposed.[15] Petitioner sought to define the PHOSITA as a generalist while Patent Owner proposed to define the PHOSITA as a specialist.[16]

The reason for this departure from the typical case was the content of the cited references. Young was an article about electrical stimulation for facial pain published in the Journal of Neurosurgery.[17] It disclosed a stimulating electrode that “prevent[s] the electrode from becoming dislodged after implantation.”[18] Young related to general neurosurgery rather than sacral neuromodulation. And while Gerber mentioned sacral nerves, the other references did not.[19]

The Board conceded that Young, Gerber, and the additional references, taken together,  disclosed every limitation of independent claim 1.[20] But Patent Owner convinced the Board that there would have been no motivation to combine the references because skilled artisans in the sacral neuromodulation field would not have looked to general neurosurgery for a solution.[21] The Board agreed, finding that none of the cited references solved the problem the ’756 patent did.[22] The Board posited that, though a PHOSITA might have found it obvious to combine the references had the ’756 patent disclosed simpler mechanical technologies, the disclosed technologies involved complex medical devices implanted in the body for neurostimulation.[23]

In defining the PHOSITA, the Board declined to focus solely on the claimed invention.[24] Petitioner had argued that the challenged claims did not recite sacral anatomy or sacral neuromodulation and the ’756 patent described uses of the invention outside of sacral anatomy.[25] But the Board found “the claims’ lack of a recitation of sacral anatomy or sacral neuromodulation does not override the Specification’s express description of the field of the invention because the claims’ purpose is not to describe the subject matter of the patent but rather to define the boundary of the patent monopoly.”[26]

B. Problems with the Holding

The Board’s reasoning raises a host of troubling issues. Ignoring patent claims in defining the PHOSITA could allow an inventor to describe the field of invention narrowly, perhaps defining it as a field having a lower level of technological sophistication, yet claim the invention broadly so as to cover fields of use having greater sophistication. This could result in the issuance of claims preventing companies operating in the more sophisticated fields from using technologies that may have been obvious to a PHOSITA working in that field.

Considering the claim language in defining the PHOSITA would prevent this problem. If a patent owner claimed the invention broadly, then the PHOSITA’s credentials should reflect that breadth. Then, if a challenger could prove that the invention would have been obvious to a PHOSITA working in any of the fields covered by the claims, the claims would not be patentable.[27]

Using the claims to define the relevant art accords with how the United States Patent and Trademark Office examines patent applications. The MPEP (Manual of Patent Examining Procedure) directs examiners as follows:

The first search should cover the invention as described and claimed, including the inventive concepts toward which the claims appear to be directed.[28]

The search should cover the claimed subject matter and should also cover the disclosed features which might reasonably be expected to be claimed.[29]

The MPEP tells examiners to determine the scope of the claims, taking the specification onto consideration only to consider possible amended claims.[30]

In examining an application for obviousness, the examiner must compare the prior art to the claims, not the specification.[31] MPEP §2141.01(a) also explains, “In order for a reference to be proper for use in an obviousness rejection under 35 U.S.C. 103, the reference must be analogous art to the claimed invention,” citing In re Bigio, 381 F.3d 1320, 1325 (Fed. Cir. 2004).[32] There is no mention of the specification.[33]

Although the MPEP does not instruct examiners whether the PHOSITA should reflect the specification or the claims, it always points the examiners to the claims in performing obviousness analyses.

The Board’s justification for choosing the specification is that it defined a narrow field of invention, but the MPEP explains that the Field of Invention is “[a] statement of the field of art to which the invention pertains . . . . The statement should be directed to the subject matter of the claimed invention.”[34] In the patent challenged in Medtronic, the statement was not directed to the subject matter of the claimed invention, yet the Board accepted it uncritically. The decision admits the purpose of the claims is “to define the boundary of the patent monopoly,”[35] but obviousness is a test of those boundaries. It makes no sense to test those boundaries from the perspective of PHOSITA having a level of skill that may have little to do with the claimed invention.



[1] Axonics Modulation Technologies, Inc. v. Medtronic, Inc., IPR2020-00715, at 3 (PTAB Sep. 13, 2021) [hereinafter Final Written Decision].

[2] Final Written Decision at 18.

[3] Id.

[4] Id. at 12.

[5] Id.

[6] Id. at 13.

[7] Id.

[8] Id. at 14.

[9] Id.

[10] Id.

[11] Id.

[12] Id. at 16.

[13] Id. at 43-45.

[14] Jonathan J. Darrow, The Neglected Dimension of Patent Law’s PHOSITA Standard, 23 Harv. J.L. & Tech. 227, 237 (2009).

[15] Final Written Decision at 15.

[16] Id. at 12.

[17] Pet. at 22.

[18] Id. at 23.

[19] Final Written Decision at 20-39.

[20] Id. at 43.

[21] Id. at 43-44.

[22] Id. at 39.

[23] Id. at 39-40.

[24] Id. at 13-14.

[25] Id. at 13.

[26] Id. at 14.

[27] See, e.g., In re Cortright, 165 F.3d 1353 (Fed. Cir. 1999).

[28] MPEP §904.

[29] MPEP §904.02.

[30] See MPEP §904.01.

[31] MPEP §2141.

[32] MPEP §2141.01(a).

[33] Id.

[34] MPEP §608.01(c).

[35] Final Written Decision at 14.


Pu-Cheng (Leo) Huang is a 3L at UCLA Law, specializing in Intellectual Property. Upon graduation, he will be joining Finnegan, Henderson, Farabow, Garrett & Dunner LLP’s D.C. Office. Before law school, Leo worked as a technical specialist at Finnegan, focusing on patent drafting and prosecution, and received a B.S. in Electrical Engineering.



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