Court Opinion

ID: 5132250
Source: CourtListenerOpinion
Date Created: 2021-12-07 00:02:16.988906+00
Date Added: 2024-06-11T08:23:29.088127
License: Public Domain

Case: 20-2243     Document: 28   Page: 1     Filed: 11/04/2021

   United States Court of Appeals
       for the Federal Circuit
                  ______________________

          UNIVERSITY OF STRATHCLYDE,
                    Appellant

                            v.

                CLEAR-VU LIGHTING LLC,
                         Appellee
                  ______________________

                        2020-2243
                  ______________________

     Appeal from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in No. IPR2019-
 00431.
                  ______________________

                 Decided: November 4, 2021
                  ______________________

     CHRISTOPHER BRANTLEY KELLY, Alston & Bird LLP, At-
 lanta, GA, argued for appellant. Also represented by
 JASON P. COOPER; KIRK T. BRADLEY, Charlotte, NC;
 NATALIE CHRISTINE CLAYTON, New York, NY.

     BRIAN J. EMFINGER, Banner & Witcoff, Ltd., Chicago,
 IL, argued for appellee. Also represented by MATTHEW
 PAUL BECKER, BINAL J. PATEL.
                 ______________________

   Before REYNA, CLEVENGER, and STOLL, Circuit Judges.
Case: 20-2243     Document: 28      Page: 2    Filed: 11/04/2021

 2       UNIVERSITY OF STRATHCLYDE    v. CLEAR-VU LIGHTING LLC

 STOLL, Circuit Judge.
     University of Strathclyde appeals from a final written
 decision of the Patent Trial and Appeal Board holding
 claims 1–4 of U.S. Patent No. 9,839,706 unpatentable as
 obvious. Because neither the Board’s finding that the prior
 art disclosed all claim limitations nor its finding of a rea-
 sonable expectation of success is supported by substantial
 evidence, we reverse the Board’s obviousness determina-
 tion.
                         BACKGROUND
                               I
      Methicillin-resistant Staphylococcus aureus (MRSA),
 and other Gram-positive bacteria 1 that have developed re-
 sistance to antibiotics, are “known to cause health prob-
 lems, particularly in the hospital environment.”
 ’706 patent col. 1 ll. 38–58. The specification of the ’706 pa-
 tent explains that effective methods of controlling trans-
 mission of and rising infection rates from antibiotic-
 resistant bacteria is “becoming one of the most significant
 problems within the healthcare industry.” Id. at col. 1
 ll. 30–33. This is due, in part, to the “availability of few
 effective sterili[z]ation methods for environmental decon-
 tamination” of air and surfaces. Id. at col. 1 ll. 26–30.
     The specification discloses that photoinactivation is a
 method that has emerged for killing harmful bacteria like
 MRSA.     Previous photoinactivation methods involved
 treating an infection by applying a photosensitizing agent
 and activating the photosensitizing agent using light

     1   Gram-positive refers to the results of a “Gram”
 stain, which is a test for determining what type of cell wall
 structure a given bacterium has. Whether a bacterium is
 Gram-positive or -negative determines which antibiotics
 can be used in a treatment plan.
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC       3

 energy, e.g., visible light having a wavelength in the region
 of 450–850 nm. Id. at col. 1 l. 59–col. 2 l. 9. While this
 technique has been shown to damage or kill certain bacte-
 ria such that their ability to grow is reduced or eliminated
 altogether, it suffers from “the significant practical disad-
 vantage that photosensiti[z]ing agents must be applied to
 the bacteria that are to be inactivated.” Id. at col. 2
 ll. 11–15.
      Scientists at the University of Strathclyde, recognizing
 this practical disadvantage, developed a method for pho-
 toinactivating antibiotic-resistant bacteria like MRSA
 without using a photosensitizing agent. Through numer-
 ous experiments, the inventors found that “[e]xposing [cer-
 tain] bacteria to blue light, or white light containing blue
 light” having a wavelength in the region of 400–500 nm,
 “stimulate[s] an inactivation process.”         Id. at col. 2
 ll. 50–52, 63–64. Specifically, the inventors experimented
 with different filters that allowed certain wavelengths of
 light to reach the bacteria, finding that wavelengths in the
 400–500 nm region “provide[d] a high rate of [MRSA] inac-
 tivation.” Id. at col. 5 ll. 11–13. These experiments led the
 inventors to conclude that “visible-light exposure over the
 wavelength range 400–450 nm is the major inducing factor
 for Staphylococcal [e.g., MRSA] inactivation, with in-
 creased inactivation occurring over the range 400–420 nm
 and optimum inactivation occurring at 405 nm.” Id.
 at col. 5 ll. 36–40. The inventors also discovered that ex-
 posing bacteria such as MRSA to 405 nm blue light re-
 quired a lower dose of light energy for inactivation
 compared to exposing bacteria to a broader wavelength
 range. For example, the inventors reported that a light
 dose of 945 J/cm2 was required to inactivate MRSA when it
 was exposed to a broad spectrum of visible light greater
 than 400 nm, whereas a light dose of only 45 J/cm2 was re-
 quired for the cultures exposed to only 405 nm blue light.
 See id. at col. 6 ll. 37–49.
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 4       UNIVERSITY OF STRATHCLYDE        v. CLEAR-VU LIGHTING LLC

     Based on their discoveries, the inventors developed a
 method of disinfection, which they claimed in the ’706 pa-
 tent. Claim 1 is illustrative of the claims on appeal and
 recites:
     1. A method for disinfecting air, contact surfaces
     or materials by inactivating one or more patho-
     genic Gram-positive bacteria in the air, on the con-
     tact surfaces or on the materials, said method
     comprising exposing the one or more pathogenic
     Gram-positive bacteria to visible light without us-
     ing a photosensitizer, wherein the one or more
     pathogenic Gram-positive bacteria are selected
     from the group consisting of Methicillin-resistant
     Staphylococcus aureus (MRSA), Coagulase-Nega-
     tive Staphylococcus (CONS), Streptococcus, Enter-
     ococcus, and Clostridium species, and wherein a
     portion of the visible light that inactivates the one
     or more pathogenic Gram-positive bacteria consists
     of wavelengths in the range 400-420 nm, and
     wherein the method is performed outside of the hu-
     man body and the contact surfaces or the materials
     are non-living.
 Id. at col. 7 l. 17–col. 8 l. 5.
                                    II
     The Board determined that claims 1 and 3 of the
 ’706 patent would have been obvious over Ashkenazi 2 in
 view of Nitzan, 3 and that claims 2 and 4 would have been

     2   Helena Ashkenazi et al., Eradication of Propioni-
 bacterium acnes by its endogenic porphyrins after illumina-
 tion with high intensity blue light, 35 J. FEMS Immunology
 & Med. Microbiology 17, 17–24 (2003).
     3   Yeshayahu Nitzan et al., ALA induced photody-
 namic effects on Gram positive and negative bacteria,
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC        5

 obvious in further view of Jones. 4 Because Strathclyde’s
 appeal is focused on the Board’s findings regarding Ashke-
 nazi and Nitzan, we discuss each of those references below.
                               A
     Ashkenazi is an article that discusses photoeradication
 of Propionibacterium acnes (P. acnes), a Gram-positive bac-
 terium that is the leading cause of acne. Ashkenazi at 17.
 “In the case of P. acnes or other bacterial cells that produce
 porphyrins,” Ashkenazi hypothesized, “blue light may pho-
 toinactivate the intact bacterial cells.” Id. at 21; see also
 id. at 18 (“It has also been shown that when illuminated
 with blue light, porphyrins damage the cells very effi-
 ciently.”). Ashkenazi suggested that light-activated por-
 phyrin molecules contribute to bacterial cell death through
 release of free radicals.
     Ashkenazi provides a method for photosensitizing
 P. acnes, which naturally produces high amounts of por-
 phyrins, using δ-aminolevulinic acid (ALA), a photosensi-
 tizer 5 that enhances porphyrin production inside cells (i.e.,
 endogenous porphyrins). To study the effects of ALA on
 inactivation, P. acnes was grown on a reinforced clostridial
 agar media supplemented with ALA and an unsupple-
 mented media (i.e., without ALA) was used as a control. It
 is undisputed that clostridial agar would have contained

 3 Photochemical & Photobiological Scis. 430, 430–35
 (2004).
     4   U.S. Pat. App. Pub. No. 2005/00550070.
     5   The Board construed the term “photosensitizer” to
 mean “a substance that, when applied to a target sub-
 stance, makes the target substance more sensitive to light.”
 Clear-Vu Lighting LLC v. Univ. of Strathclyde,
 No. IPR2019-00431, 2020 WL 3848045, at *7 (P.T.A.B.
 July 8, 2020) (Final Decision). Neither party challenges
 the Board’s construction on appeal.
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 6      UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC

 the vitamin riboflavin which, like ALA, is a photosensi-
 tizer. Thus, both of Ashkenazi’s methods involved growing
 P. acnes in the presence of a photosensitizer—either ribo-
 flavin alone or together with ALA.
      The cultures grew for up to 96 hours and were illumi-
 nated with 407–420 nm blue light at various light doses ei-
 ther once after 24 hours of growth or at consecutive 24-hour
 intervals. Both the ALA and non-ALA P. acnes cultures
 that were exposed to multiple, consecutive illuminations
 showed a decrease in viability of several orders of magni-
 tude compared to cultures illuminated only once, and “[t]he
 decrease in viability of the cultures grown with ALA and
 illuminated with blue light was far more significant than
 that of cultures grown without ALA.” Id. at 20. Ashkenazi
 also observed that increasing the light dose, e.g., from
 75 J/cm2 to 100 J/cm2, likewise resulted in decreased via-
 bility for both the ALA and non-ALA P. acnes. Noting that
 “[t]he increase in the amounts of porphyrins in P. acnes as
 a result of ALA induction was significantly above the nat-
 ural production of this bacterium,” Ashkenazi concluded
 from these experiments that “the greater the intracellular
 amount of the porphyrin the better are the eradication re-
 sults.” Id. at 22.
                              B
     Nitzan’s authors, two of whom co-authored the Ashke-
 nazi article, continued studying the effects of ALA on
 Gram-positive bacteria, including MRSA; the results were
 published just over a year after Ashkenazi’s. Part of
 Nitzan’s study focused on how exogenous porphyrins—i.e.,
 a culture media supplemented with porphyrins—would af-
 fect inactivation. To do so, four different categories of
 MRSA cultures were prepared for the various bacteria, two
 of which were exposed to ALA, and two of which were not.
 Nitzan at 433 (Tbl. 5). For all of the non-ALA MRSA cul-
 tures, only some of which were grown on a media supple-
 mented with exogenous porphyrins, Nitzan reported a
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC        7

 1.0 survival fraction, meaning there was “no decrease in vi-
 ability . . . after illumination” with 50 J/cm2 of 407–420 nm
 blue light. Id. at 433.
                              III
      Clear-Vu Lighting LLC petitioned for inter partes re-
 view of claims 1–4 of the ’706 patent on four separate
 grounds: (1) claims 1 and 3 are anticipated by Nitzan;
 (2) claims 2 and 4 would have been obvious over Nitzan in
 view of Jones; (3) claims 1 and 3 would have been obvious
 over Ashkenazi in view of Nitzan; and (4) claims 2 and 4
 would have been obvious over Ashkenazi in view of Nitzan
 and Jones. Final Decision, 2020 WL 3848045, at *1–2. The
 Board instituted review. See id.
     In its final written decision, the Board determined that
 Clear-Vu failed to prove by a preponderance of the evidence
 that claims 1 and 3 were anticipated by Nitzan, and that
 claims 2 and 4 would have been obvious over Nitzan in view
 of Jones. Id. at *22. Specifically, the Board found that
 Clear-Vu failed to demonstrate “that a 1.0 survival fraction
 measured for Nitzan’s non-ALA induced MRSA demon-
 strates ‘inactivation,’” which the parties agreed means, in
 the context of the ’706 patent, that the “bacteria are killed,
 or damaged so as to reduce or inhibit bacterial replication.”
 Id. at *10, 16; see also ’706 patent col. 2 ll. 44–46.
     The Board, however, agreed with Clear-Vu that
 claims 1 and 3 would have been obvious over Ashkenazi in
 view of Nitzan, and that claims 2 and 4 would likewise have
 been obvious over Ashkenazi in view of Nitzan and Jones.
 Final Decision, 2020 WL 3848045, at *22. Specifically, it
 found “Ashkenazi and Nitzan teach or suggest all the limi-
 tations of claims 1 and 3,” and that a person of ordinary
 skill in the art would have been motivated to combine these
 two references and “would have had a reasonable expecta-
 tion of successfully doing so.” Id. at *20.
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 8      UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC

     Regarding the scope and content of the prior art, the
 Board concluded that the only dispute was whether the
 prior art taught exposing bacteria to light without using a
 photosensitizer, finding that the “combined teachings of
 Nitzan and Ashkenazi” disclosed this limitation. Id.
 at *12–13 (emphasis added). In doing so, the Board sum-
 marily dismissed Strathclyde’s arguments that neither ref-
 erence taught this limitation, reasoning that Strathclyde
 “focus[ed] on Ashkenazi individually,” not the combined
 teachings of Ashkenazi and Nitzan. Id. at *13.
     The Board then found that a person of ordinary skill
 would have had a reasonable expectation of “inactivating
 MRSA using 407–420 nm light without applying a photo-
 sensitizer based on the combined teachings of Ashkenazi
 and Nitzan.” Id. at *16. Although neither Ashkenazi nor
 Nitzan achieved inactivation of any bacteria without using
 a photosensitizer and, as the Board found, Nitzan failed to
 achieve any inactivation when it exposed MRSA to
 407–420 nm light without applying a photosensitizer, id.
 at *10, the Board nonetheless found that a skilled artisan
 would have reasonably expected “some” amount of inacti-
 vation because the claims “do not require any specific
 amount of inactivation,” id. at *16, 18. In doing so, the
 Board relied largely on Ashkenazi’s teachings that increas-
 ing the light doses, the number of illuminations, and the
 length of time the bacteria are cultured resulted in greater
 inactivation for both the ALA and non-ALA P. acnes to sup-
 port its finding that a skilled artisan applying Ashkenazi’s
 teachings would expect at least “some” inactivation for non-
 ALA MRSA. Id. at *18. The Board ultimately concluded
 that claims 1 and 3 were unpatentable as obvious over Ash-
 kenazi and Nitzan. Id. at *20. Because Strathclyde did not
 substantively address Clear-Vu’s arguments with respect
 to claims 2 and 4, instead relying on the same arguments
 it made with respect to claims 1 and 3, the Board deter-
 mined that claims 2 and 4 were unpatentable as obvious
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC       9

 over Ashkenazi, Nitzan, and Jones for the same reasons as
 claims 1 and 3. Id. at *21.
    Strathclyde appeals, and we have jurisdiction under
 28 U.S.C. § 1295(a)(4)(A).
                         DISCUSSION
     We review the Board’s legal conclusions de novo and its
 factual findings for substantial evidence. Pers. Web Techs.
 v. Apple, Inc., 848 F.3d 987, 991 (Fed. Cir. 2017). “The sub-
 stantial evidence standard asks ‘whether a reasonable fact
 finder could have arrived at the agency’s decision,’ and ‘in-
 volves examination of the record as a whole, taking into ac-
 count evidence that both justifies and detracts from an
 agency’s decision.’” OSI Pharms., LLC v. Apotex Inc.,
 939 F.3d 1375, 1381–82 (Fed. Cir. 2019) (quoting In re
 Gartside, 203 F.3d 1305, 1312 (Fed. Cir. 2000)).
      “Obviousness is a question of law based on underlying
 findings of fact.” OSI Pharms., 939 F.3d at 1382 (quoting
 In re Kubin, 561 F.3d 1351, 1355 (Fed. Cir. 2009)). An ob-
 viousness determination generally requires a finding that
 “all claimed limitations are disclosed in the prior art,” PAR
 Pharm., Inc. v. TWI Pharms., Inc., 773 F.3d 1186, 1194
 (Fed. Cir. 2014); cf. Koninklijke Philips N.V. v. Google LLC,
 948 F.3d 1330, 1337–38 (Fed. Cir. 2020) (explaining that
 the common knowledge of a skilled artisan can be used to
 supply a missing limitation in some circumstances), and
 “that a person of ordinary skill in the art would have been
 motivated to combine or modify the teachings in the prior
 art and would have had a reasonable expectation of success
 in doing so,” OSI Pharms., 939 F.3d at 1382 (quoting Re-
 gents of Univ. of Cal. v. Broad Inst., Inc., 903 F.3d 1286,
 1291 (Fed. Cir. 2018)). Whether the prior art discloses a
 claim limitation, whether a skilled artisan would have
 been motivated to modify or combine teachings in the prior
 art, and whether she would have had a reasonable expec-
 tation of success in doing so are questions of fact. Tech.
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 10     UNIVERSITY OF STRATHCLYDE    v. CLEAR-VU LIGHTING LLC

 Consumer Prods., Inc. v. Lighting Sci. Grp. Corp., 955 F.3d
 16, 22 (Fed. Cir. 2020); OSI Pharm., 939 F.3d at 1382.
     On appeal, Strathclyde challenges the Board’s obvious-
 ness determination, arguing that the Board erred in find-
 ing that the combination of Ashkenazi and Nitzan teaches
 inactivating one or more Gram-positive bacteria without
 using a photosensitizer. It also asserts that the Board’s
 finding of a reasonable expectation of success is not sup-
 ported by substantial evidence. We address each issue in
 turn.
                               I
     We begin by addressing the Board’s erroneous finding
 that the prior art disclosed all claim limitations. Both par-
 ties appear to agree that most of the limitations found in
 claims 1 and 3 are disclosed by Ashkenazi or Nitzan; the
 only dispute is whether these references teach inactivating
 one of the claimed Gram-positive bacteria without using a
 photosensitizer. The Board’s finding that this was taught
 by the combination of Ashkenazi and Nitzan is not sup-
 ported by substantial evidence.
      Claims 1 and 3 require both exposing the claimed
 Gram-positive bacteria to 400–420 nm blue light without
 using a photosensitizer and that the bacteria are inacti-
 vated as a result. While Ashkenazi discloses culturing
 P. acnes both with and without ALA such that it achieves
 inactivation after exposure to 407–420 nm blue light for
 (1) ALA P. acnes and (2) non-ALA P. acnes, the parties
 agree that the media Ashkenazi used to culture P. acnes
 contained the vitamin riboflavin, a photosensitizer. See Fi-
 nal Decision, 2020 WL 3848045, at *12; see also
 J.A. 2139–40 (Goodrich Decl. ¶ 121). It follows, then, that
 all of Ashkenazi’s P. acnes cultures were grown in the pres-
 ence of a photosensitizer—either riboflavin alone, or ribo-
 flavin together with ALA. We see nothing in Ashkenazi
 that discloses or suggests inactivating P. acnes, or any
 other bacteria, without using a photosensitizer.
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC       11

      In addition, although Nitzan provides an example in
 which MRSA and other bacteria were exposed to
 407–420 nm blue light without ALA or any other photosen-
 sitizer, there is no evidence that Nitzan successfully
 achieved inactivation under this condition. Indeed, in find-
 ing that Nitzan did not anticipate claims 1 and 3, the Board
 found Clear-Vu failed to establish that Nitzan’s non-ALA
 MRSA demonstrated “inactivation” as required by the
 claims. See Final Decision, 2020 WL 3848045, at *10.
      In making its contrary finding that the combination of
 references disclosed this limitation, the Board credited
 Clear-Vu’s argument that a skilled artisan would have pre-
 pared a MRSA culture according to the method described
 in Nitzan—which, unlike the media used to culture P. ac-
 nes in Ashkenazi’s experiments, would not have contained
 riboflavin—and applied Ashkenazi’s teaching that increas-
 ing the light energy, number of illuminations, and length
 of time the bacteria are cultured may result in greater in-
 activation for both ALA and non-ALA bacteria, as was
 shown for P. acnes. Id. at *13. The Board found that this
 combination, therefore, “disclose[d] exposing bacteria to
 light without using a photosensitizer.” Id. Given neither
 Ashkenazi nor Nitzan teaches or suggests inactivation of
 any bacteria without using a photosensitizer, we fail to see
 why a skilled artisan would opt to entirely omit a photo-
 sensitizer when combining these references. Indeed, the
 Board articulated no rational basis6—and we discern

     6    Although the Board relied on and found persuasive
 the testimony of Clear-Vu’s expert, Dr. Sulzinski, discuss-
 ing this modification to Nitzan’s non-ALA MRSA, see id.
 at *13 (citing J.A. 2336 (Sulzinski Decl. ¶ 77)), the Board
 discredited testimony from this same paragraph in Dr. Sul-
 zinski’s declaration in its anticipation analysis because he
 “merely state[d] . . . his opinion, and offer[ed] no evidence”
 to support his statements, id. at *10 (citing J.A. 2336
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 12     UNIVERSITY OF STRATHCLYDE    v. CLEAR-VU LIGHTING LLC

 none—for combining Ashkenazi’s P. acnes experiments,
 which at all times used a photosensitizer, with Nitzan’s
 non-ALA MRSA experiment, which did not achieve inacti-
 vation, to arrive at an embodiment in which MRSA is inac-
 tivated by exposing it to 407–420 nm blue light without
 using a photosensitizer. We find it particularly relevant
 that Nitzan itself disclosed such a photosensitizer-free em-
 bodiment and was wholly unsuccessful in achieving inacti-
 vation.
     Nor are we persuaded that Ashkenazi and Nitzan, ei-
 ther individually or in combination, “disclose[] the particu-
 lar ‘inactivating’ and ‘inactivates’ language” found in
 claims 1 and 3 as Clear-Vu suggests. Appellee’s Br. 57.
 Importantly, the claims require that the inactivation is a
 result of exposing bacteria to 400–420 nm light without us-
 ing a photosensitizer, which is neither taught nor suggested
 by the prior art of record. We decline Clear-Vu’s invitation
 to read the inactivation limitation in isolation, divorced
 from the claim as a whole. Cf. ATD Corp. v. Lydall, Inc.,
 159 F.3d 534, 546 (Fed. Cir. 1998) (“Obviousness cannot be
 based on the hindsight combination of components selec-
 tively culled from the prior art to fit the parameters of the
 patented invention.” (cleaned up)).
     On this record, we conclude that no reasonable fact
 finder could have found that the combination of Ashkenazi
 and Nitzan discloses inactivating one or more Gram-posi-
 tive bacteria without using a photosensitizer. The Board’s
 finding to the contrary is not supported by substantial evi-
 dence.
                              II
     We turn next to the Board’s findings on reasonable ex-
 pectation of success. The Board found that a skilled artisan

 (Sulzinski Decl. ¶ 77)). This inconsistency in the Board’s
 credibility findings further undermines its findings here.
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC     13

 would have expected that MRSA could be inactivated by
 blue light without using a photosensitizer due to the pres-
 ence of at least some amount of naturally produced porphy-
 rin in the bacteria. We disagree. The only support for such
 a finding is pure conjecture coupled with hindsight reliance
 on the teachings in the ’706 patent.
     Starting with the references themselves, neither Ash-
 kenazi nor Nitzan provides a skilled artisan with any evi-
 dence or data or other promising information showing
 successful inactivation of P. acnes, MRSA, or any other bac-
 teria without using a photosensitizer. These references
 thus contain no suggestion that a skilled artisan would rea-
 sonably expect that MRSA or one of the other claimed
 Gram-positive bacteria could be inactivated upon exposure
 to 407–420 nm blue light without using a photosensitizer.
 The Board nevertheless found that a skilled artisan would
 have expected that MRSA could be inactivated by
 407–420 nm blue light without using a photosensitizer be-
 cause, as both parties agree, MRSA naturally produces “at
 least some” amount of endogenous porphyrins. Final Deci-
 sion, 2020 WL 3848045, at *17. The Board, relying on Ash-
 kenazi’s teaching that “blue light may” inactivate “other
 bacterial cells that produce porphyrins,” Ashkenazi at 21
 (emphases added), reasoned that because light-activated
 porphyrin molecules were shown in Ashkenazi to cause in-
 activation for P. acnes (even though Ashkenazi’s experi-
 ments applied a photosensitizer), the fact that MRSA has
 some level of endogenous porphyrin suggests to a skilled
 artisan that MRSA, too, would exhibit some amount of in-
 activation after exposure to 407–420 nm blue light. But
 there is simply no evidence of record at the time of the
 ’706 patent to support this assumption. In fact, the evi-
 dence of record—Nitzan and an earlier publication
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 14       UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC

 authored by Dr. Nitzan in 1999 (Nitzan 1999 7)—shows the
 opposite, illuminating the error in the Board’s finding.
      In the late 1990s, Dr. Nitzan and his colleagues “exam-
 ined the effects of the accumulation of endogenous porphy-
 rins on” MRSA. Nitzan 1999, Abstract; see also id. at 270
 (explaining that the tested S. aureus strain was methicil-
 lin-resistant). As with the later studies described in Ash-
 kenazi and Nitzan, Dr. Nitzan exposed both the ALA and
 non-ALA MRSA to doses of 400–450 nm blue light ranging
 from 0–50 J/cm2. The survival fraction at each light dose
 for the non-ALA MRSA was 1.0, id. at 274 (Fig. 3(a)), mean-
 ing there was no decrease in viability and thus no inactiva-
 tion, whereas the viability of the ALA MRSA decreased by
 “3–4 orders of magnitude,” id. at 273. Dr. Nitzan reported
 the same results for the non-ALA MRSA only a couple of
 years later. See Nitzan at 433 & Tbl. 5 (reporting a 1.0 sur-
 vival fraction for non-ALA MRSA after illumination with
 50 J/cm2 blue light, meaning “no decrease in viability”).
     Dr. Nitzan’s experiments thus are directly contrary to
 the Board’s rationale for why a skilled artisan would have
 expected success in inactivating MRSA in the absence of a
 photosensitizer. Even accepting as true that MRSA natu-
 rally has “at least some” amount of endogenous porphyrins,
 the data Dr. Nitzan reported would have indicated to a per-
 son of ordinary skill in the art that those natural levels are
 insufficient to inactivate MRSA using 407–420 nm blue
 light without also using a photosensitizer.
     In finding that Clear-Vu had established a reasonable
 expectation of success, the Board dismissed the data re-
 ported in Nitzan and Nitzan 1999 because, in its view, it

      7 Y. Nitzan & M. Kauffman, Endogenous Porphyrin
 Production in Bacteria by δ-Aminoleavulinic Acid and Sub-
 sequent Bacterial Photoeradication, 14 Lasers Med. Sci.
 269 (1999).
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC     15

 would lead a skilled artisan to the “limited conclusion that
 non-ALA-treated MRSA incubated for 4 hours and treated
 with a single dose of 50 J/cm2 light showed no decrease in
 activity.” Final Decision, 2020 WL 3848045, at *18 (em-
 phasis added); id. (“We reach a similar conclusion for the
 data reported in Nitzan 1999, which only shows data up to
 a light intensity of 50 J/cm2, the same intensity used in
 Nitzan.”). The Board based its finding largely on the fact
 that neither Nitzan nor Nitzan 1999 tested light doses
 above 50 J/cm2, reasoning that using an increased light
 dose, such as the 75 J/cm2 dose used in Ashkenazi’s exper-
 iments, would cause inactivation of MRSA based on Ash-
 kenazi’s finding that increased light doses resulted in
 greater inactivation for both ALA and non-ALA P. acnes.
 Id. at *17–18.
     The Board’s reasoning finds no support in the record.
 The only evidence before the Board on this issue was the
 unrebutted     testimony     of    Strathclyde’s    expert,
 Dr. Goodrich, who testified the opposite. See Oral Arg.
 at 12:22–15:05, http://oralarguments.cafc.uscourts.gov/de-
 fault.aspx?fl=20-2243_05032021.mp3 (Clear-Vu conceding
 it did not provide rebuttal testimony on this point).
 Dr. Goodrich explained that a skilled artisan “viewing th[e]
 graphical representation of Nitzan 1999’s data would have
 clearly expected the curve of the ALA-absent S. aureus
 [MRSA] data to remain flat as dosage increased to
 75 J/cm2,” J.A. 2133 (Goodrich Decl. ¶ 107) (emphases
 added), as shown below in his annotated version of Nitzan
 1999’s Figure 3(a):
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 16     UNIVERSITY OF STRATHCLYDE    v. CLEAR-VU LIGHTING LLC

 J.A. 2132–33 (Goodrich Decl. ¶ 106). Dr. Goodrich then
 concluded that, to a skilled artisan, “the data in Nitzan
 1999 would have indicated that the response of MRSA
 without ALA to blue light at 75 J/cm2 would have been the
 same as 50 J/cm2—no bacteria would have been killed.”
 J.A. 2133 (Goodrich Decl. ¶ 107) (emphasis added).
      The Board gave no weight to Dr. Goodrich’s testimony
 because, in its view, Dr. Goodrich did not provide the un-
 derlying facts forming the basis for his opinions. See Final
 Decision, 2020 WL 3848045, at *18 (citing 37 C.F.R.
 § 42.65(a)). We disagree. In his declaration, Dr. Goodrich
 specifically relied on and analyzed Nitzan 1999’s data in
 forming his opinions. Given that the Board’s stated reason
 for discrediting this written testimony is unsupported by
 the record before us, we see no reason to “defer[] to the spe-
 cial province of the Board to exercise its discretion concern-
 ing the credibility of expert witnesses” as Clear-Vu
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 UNIVERSITY OF STRATHCLYDE    v. CLEAR-VU LIGHTING LLC        17

 suggests we do here. Appellee’s Br. 49 (citing Yorkey
 v. Diab, 601 F.3d 1279, 1284 (Fed. Cir. 2010)).
      Thus, not only is there a complete lack of evidence in
 the record that any bacteria were inactivated after expo-
 sure to 407–420 nm blue light without using a photosensi-
 tizer, there is also evidence showing that others had failed
 to inactivate MRSA—one of the claimed Gram-positive bac-
 teria—without using a photosensitizer, despite experi-
 menting with different light doses and different
 wavelength ranges of blue light. We have found that such
 failures undermine a finding of a reasonable expectation of
 success.
      For example, in OSI Pharmaceuticals, we reversed the
 Board’s obviousness determination because its finding of a
 reasonable expectation of success was not supported by
 substantial evidence. 939 F.3d at 1384–85. The claims at
 issue in OSI were directed to a method of treating
 non-small cell lung cancer (NSCLC) using a therapeuti-
 cally effective amount of a drug known as erlotinib. Id.
 at 1378–79, 1384. The Board found that two different prior
 art combinations would have provided a skilled artisan
 with a reasonable expectation of success in using erlotinib
 to treat NSCLC in a mammal. Id. at 1384. We disagreed,
 explaining that none of these references contained “data or
 other promising information regarding erlotinib’s efficacy
 in treating NSCLC.” Id. at 1384; see also id. at 1385. We
 also found it significant that, during the time of the inven-
 tion, there was a 99.5% failure rate for other drugs entering
 Phase II clinical trials that, like erlotinib, were targeted for
 the treatment of NSCLC. Id. at 1385. Thus, given the “fail-
 ure rate” and lack of “data or any other reliable indicator
 of success,” we found that “the only reasonable expectation
 at the time of the invention was failure, not success.” Id.
     Such is the case here. In view of Dr. Nitzan’s reported
 failures for MRSA and lack of any “reliable indicator of suc-
 cess,” we fail to see how Ashkenazi’s prophetic statement
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 18     UNIVERSITY OF STRATHCLYDE     v. CLEAR-VU LIGHTING LLC

 about what “may” happen when “other bacterial cells” are
 exposed to blue light would lead a skilled artisan to reason-
 ably expect that MRSA could be inactivated when exposed
 to 407–420 nm blue light without using a photosensitizer.
 The Board’s finding that a skilled artisan would expect at
 least “some” inactivation for non-ALA MRSA—in view of
 Ashkenazi’s teaching that increasing the light doses, the
 number of illuminations, and the length of time the bacte-
 ria are cultured can result in greater inactivation based on
 experiments that were conducted using a photosensitizer—
 is not supported by substantial evidence.
     In attempting to support the Board’s findings,
 Clear-Vu argues that support can be found in the ’706 pa-
 tent itself. See Appellee’s Br. 58 (“It defies logic to conclude
 that inactivating MRSA by applying Ashkenazi’s technique
 to Nitzan’s MRSA would not result in inactivating MRSA
 when the patentee obtained that very result using the
 same technique.” (emphasis added)). But “[t]he inventor’s
 own path itself never leads to a conclusion of obviousness;
 that is hindsight. What matters is the path that the person
 of ordinary skill in the art would have followed, as evi-
 denced by the pertinent prior art.” Otsuka Pharm. Co.,
 v. Sandoz, Inc., 678 F.3d 1280, 1296 (Fed. Cir. 2012).
 Given the record on appeal, as with OSI, we are left to con-
 clude that “[i]t is only with the benefit of hindsight that a
 person of skill in the art would have had a reasonable ex-
 pectation of success in view of the asserted references.”
 OSI Pharms., 939 F.3d at 1385.
      Contrary to Clear-Vu’s arguments, we do not hold that
 “absolute predictability” or “guaranteed success” is re-
 quired to find a reasonable expectation of success. Appel-
 lee’s Br. 43, 45 (emphasis omitted). To be sure, we have
 repeatedly rejected that notion. See, e.g., Acorda Thera-
 peutics, Inc. v. Roxane Lab’ys, Inc., 903 F.3d 1310, 1333
 (Fed. Cir. 2018) (“This court has long rejected a require-
 ment of ‘[c]onclusive proof of efficacy’ for obviousness.” (al-
 teration in original) (quoting Hoffmann-La Roche Inc.
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 UNIVERSITY OF STRATHCLYDE   v. CLEAR-VU LIGHTING LLC     19

 v. Apotex Inc., 748 F.3d 1326, 1331 (Fed. Cir. 2014))); OSI
 Pharms., 939 F.3d at 1385; PAR Pharm., 773 F.3d at 1198.
 We reaffirm today that absolute predictability of success is
 not required, only a reasonable expectation. In this case,
 where the prior art evidences only failures to achieve that
 at which the inventors succeeded, no reasonable fact finder
 could find an expectation of success based on the teachings
 of that same prior art. The Board’s finding is not supported
 by substantial evidence, and we therefore reverse its obvi-
 ousness determination.
                        CONCLUSION
     We have considered the parties’ remaining arguments
 but find them unpersuasive. For the foregoing reasons, we
 reverse the Board’s obviousness determination.
                        REVERSED