The recent decision by the Federal Circuit Court of Appeals, University of Strathclyde v. Clear-Vu Lighting, Case 2020-2243, Nov. 4, 2021, provides useful instruction to the USPTO Patent Trial and Appeal Board and to patent practitioners regarding what must be found in the prior art to make a claimed invention legally obvious and therefore not patent-worthy.

The criteria for obviousness are whether combined items of prior art disclose all the elements of a claimed invention and provide a skilled artisan both a motive to combine those elements and a reasonable expectation of success. The Strathclyde case provides a reminder that speculation leaning toward a possibility of success is not enough to render unpatentable an inventor’s actual achievement.

University of Strathclyde inventors Anderson et al. were exploring the use of blue light to kill methicillin-resistant Gram-positive bacteria Staphylococcus aureus (MRSA) and other bacteria. They discovered, and claimed in U.S. Patent 9, 839,706, a method and system for inactivating certain pathogenic bacteria by exposing the bacteria to visible light including wavelengths in the range 400-420 nm, without using a photosensitizer. Claim 1 reads in pertinent part:

1. A method for … inactivating one or more pathogenic Gram-positive bacteria in [the] air, on [the] contact surfaces or on [the] materials, said method comprising exposing the … bacteria to visible light without using a photosensitizer, … wherein a portion of the visible light … consists of wavelengths in the range 400-420 nm….

Anderson et al. were granted their patent over prior art including two principal references: Ashkenazi et al. and Nitzan et al.

Ashkenazi et al. started with the proposition that on exposure to blue light, porphyrins damage bacterial cells and they speculated that in the case of P. acnes (a Gram-positive bacterium that causes acne) or other cells that produce porphyrins, blue light may inactivate the cells. They reported the inactivation of P. acnes by exposure to 407-420 nm light with and without the photosensitizer ALA (δ-aminolevulinic acid), but in each case in the presence of another photosensitizer (riboflavin). The photosensitizers stimulated the bacteria’s own production of porphyrins. They found that the viability of the cells on exposure to the light was more reduced by including the exogenous ALA with the riboflavin, and that the effect increased with increased exposure to the light.

Nitzan et al. shed light on the effect of providing porphyrins in the growth medium outside bacteria with and without a photosensitizer. They reported that without the photosensitizer, blue light had no effect on the bacteria, regardless of exogenous porphyrins.
Clear-Vu challenged the patent before the PTAB, which found the independent claims invalid for being obvious over Ashkenazi et al. and Nitzan et al. The PTAB had accepted Clear-Vu’s assertion that the Anderson et al. patent was obvious because Nitzan et al. disclosed exposing bacteria to blue light without a photosensitizer, while Ashkenazi et al. suggested that such exposure ‘may’ photoinactivate intact bacterial cells, and that since Anderson et al.’s claims do not require any particular degree of inactivation of the cells, the prior art rendered the claims obvious. The Federal Circuit disagreed.

The University took an appeal to the Federal Circuit, and on review the Court noted that Ashkenazi et al. disclosed no inactivation of the cells in the absence of a photosensitizer, and while Nitzan et al. demonstrated exposure of cells to blue light without a photosensitizer, they reported no effect on the cells. Clear-Vu had argued that it was sufficient to find the challenged claim limitations -apart from the claimed result of bacterial inactivation – were suggested by combining the teachings of Ashkenazi et al. and Nitzan et al. The Court concluded that in the absence of recognition of effectiveness in the prior art references, the prior art did not disclose all the claimed elements.

Moreover, the Court found that despite the hypothesis of Ashkenazi et al. that there may be some porphyrin-producing bacteria that could be inactivated by exposure to blue light without using a photosensitizer, they had not tried to demonstrate that hypothesis, and Nitzan et al. seemed to demonstrate the opposite. The PTAB had limited the negative implication of Nitzan et al. to the specific experimental conditions they reported, which involved lower intensity light than used by Ashkenazi et al., leaving the Ashkenazi hypothesis intact. However, Strathclyde had submitted expert evidence showing that extrapolation from the Nitzan et al. data would run counter to the Ashkenazi hypothesis. The Court therefore concluded that the PTAB was in error to find that these references would provide a reasonable expectation of success in deactivating bacteria by exposure to blue light without a photosensitizer.

Clear-Vu argued to the court that if the Anderson et al. inventors followed the Ashkenazi technique to the Nitzan bacteria and achieved the Ashkenazi result, that should establish the obviousness of the Anderson invention. However, the Court dismissed this approach, pointing out that “the inventor’s own path itself never leads to a conclusion of obviousness; that is hindsight.”

Thus, the Court found that the PTAB erred in finding all the claimed elements in the prior art and in finding that the prior art provided a reasonable expectation of success in deactivating bacteria without an added photosensitizer. This provides a reminder that when results are attained by a method for which the prior art does not provide a suggestion of success, patent claim to the method can be patentable if they include the surprising result.

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