PTAB Obviousness Ruling Reversed by CAFC, Clarifying ‘Reasonable Expectation of Success’ Standard

On November 4, the U.S. Court of Appeals for the Federal Circuit (CAFC) reversed a decision by the U.S. Patent and Trademark Office’s Patent Trial and Appeal Board (PTAB) that University of Strathclyde’s patent claims for a method for photoinactivating antibiotic-resistant bacteria without using a photosensitizing agent were unpatentable. The PTAB held claims one, two, three, and four of U.S. Patent No. 9,839,706 (‘706 patent) were obvious based on the prior art. The court held the PTAB’s findings were not based on substantial evidence.

The inventors found that exposing certain bacteria to blue or white light with a wavelength between 400-500 nm stimulated an inactivation process through numerous experiments. By experimenting with different filters that only allowed certain wavelengths through, the inventors came to the conclusion that visible-light exposure over certain wavelengths was a major inducing factor for inactivation. The inventors additionally concluded that exposing the bacteria to 405 nm blue light required less light energy for inactivation.

Inter Partes Review

Strathclyde filed for the ‘706 patent which claimed a method of disinfecting the air and other surfaces. Clear-Vu Lighting LLC (Clear-Vu) petitioned for inter partes review of claims one to four of the ’706 patent on four separate grounds. 1) claims one and three were anticipated by Nitzan; 2) claims two and four were obvious over Nitzan in view of Jones; 3) claims one and three were obvious over Ashkenazi in view of Nitzan; and 4) claims two and four were obvious over Ashkenazi in view of Nitzan and Jones. Since Strathclyde’s appeal focused on the finding regarding Ashkenazi and Nitzan, the CAFC focused on these references specifically.

Ashkenazi is an article that hypothesized that blue light may photoinactivate bacterial cells on a person’s body. Ashkenazi provided a method for photosensitizing Propionibacterium acnes (P. acnes). Ashkenazi was able to conclude from described experiments that “the greater the intracellular amount of the porphyrin the better are the eradication results.”

Nitzan is an article about the continued study of the effects of certain photosentizers on bacteria. The study found “a 1.0 survival fraction which means there was ‘no decrease in viability . . . after illumination’ with 50 J/cm² of 407-420 nm blue light.”

The PTAB determined that Clear-Vu did not prove that claims one and three were anticipated and claims two and four were obvious over Nitzan in view of Jones. The PTAB found that Clear-Vu failed to demonstrate how the results of the Nitzan demonstration showed inactivation of the bacteria.

The Board however did determine that Clear-Vu showed enough evidence that claims one and three were obvious over Ashkenazi in view of Nitzan and claims two and four were obvious over Ashkenazi in view of Nitzan and Jones. The PTAB held that Nitzan and Ashkenazi teach or suggest all of the limitations of claims one and three, and the reasonable expectation of success would motivate a person of ordinary skill in the art to combine Nitzan and Ashkenazi.

Review of the PTAB

Strathclyde challenged the PTAB’s obviousness determination by arguing the Board erred in finding that Ashkenazi and Nitzan in combination teach not using a photosensitizer to inactivate bacteria. Strathclyde further argued the PTAB’s determination that there was a reasonable expectation of success was not supported by substantial evidence.

The CAFC concluded that the finding regarding combining Ashkenazi and Nitzan to teach the limitations of claims one and three of the ‘706 patent were not supported by substantial evidence. Claims one and three require that the claimed bacteria be exposed to blue light without using a photosensitizer and the bacteria are inactivated as a result. Ashkenazi teaches that exposing bacteria to blue light achieves inactivation, but a photosensitizer was used. Nitzan teaches exposing bacteria to a blue light without any photosensitizer but no evidence was provided that inactivation was achieved.

Clear-Vu argued that a person skilled in the art would have prepared a culture according to Nitzan and applied the teachings of Ashkenazi that changing the light energy could result in greater inactivation. The PTAB agreed with this argument, highlighting that combining these two references would “disclose exposing bacteria to light without using a photosensitizer.”

The CAFC concluded neither Ashkenazi nor Nitzan teach inactivation of any bacteria without using a photosensitizer and failed to see why a skilled artisan would not opt to use a photosensitizer when examining these two references together. The court found it particularly relevant that in Nitzan the photosensitizer-free embodiment was unable to achieve inactivation of the bacteria.

Additionally, the court was not persuaded that Ashkenazi and Nitzan disclose the “inactivating” language found in claims one and three as Clear-Vu argues. The claims require exposing the bacteria to blue light within the 400-420 nm light without the use of a photosensitizer.

Reasonable Expectation of Success

The PTAB found that a skilled artisan would have expected that exposing bacteria to blue light without a photosensitizer could inactivate the bacteria because of the presence of naturally produced porphyrin in bacteria. The CAFC found that the only support for such a claim is purely conjecture coupled with hindsight bias of the teachings of the ‘706 patent.

The PTAB relied on Ashkenazi’s teaching that blue light may inactivate other bacterial cells that produce porphyrins. However, there is no indication of record at the time of the ‘706 patent to support this assumption according to the CAFC. The only evidence available was to the contrary in both Nitzan and an earlier publication. The PTAB dismissed the data reported in Nitzan because it viewed that a skilled artisan would have been led to the limited conclusion that increased light energy would lead to inactivation.

The CAFC concluded that this reasoning has no support in the record. The only evidence before the PTAB regarding this issue was the testimony of Strathclyde’s expert witness, who testified to the opposite of the PTAB’s findings. The PTAB gave no weight to the expert testimony because they felt the underlying facts of the expert’s opinion were not provided. The court held that the stated reasons that the PTAB gave for disregarding the expert’s testimony were unsupported meaning the CAFC gave no deference to the PTAB’s discretion concerning expert credibility.

The court continued:

Thus, not only is there a complete lack of evidence in the record that any bacteria were inactivated after exposure to 407–420 nm blue light without using a photosensitizer, there is also evidence showing that others had failed . . . We have found that such failures undermine a finding of a reasonable expectation of success.

Clear-Vu’s final argument was that support for the PTAB’s findings could be found in the ‘706 patent itself for reasonable success. The court found this to be the very definition of hindsight bias. When analyzing an inventor’s path, the path of a person with ordinary skill in the art should be followed by the relevant prior art and not the inventor’s own path. The CAFC does not require “absolute predictability” or “guaranteed success” to find a reasonable expectation of success, but 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,” wrote the court.