Federal Circuit Emphasizes Unpredictability in Overturning PTAB's Finding of Obviousness

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The Federal Circuit recently overturned a PTAB decision finding patent claims obvious as being based on “pure conjecture coupled with hindsight reliance on the teachings” of the patent under consideration. While the PTAB supported its decision on its finding of a reasonable expectation of success for the claimed invention, the Federal Circuit disagreed and found, instead, that “the only reasonable expectation at the time of the invention was failure, not success.”

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In University of Strathclyde v. Clear-Vu Lighting LLC,[i] the U.S. Court of Appeals for the Federal Circuit reversed a Patent Trial and Appeal Board’s (“PTAB”) finding that claims 1-4 of U.S. Patent No. 9,839,706 (“the ’706 patent”) were obvious. 

The ‘706 patent is directed to a method of inactivating Gram-positive bacteria, including Methicillin-resistant Staphylococcus aureus (MRSA), via irradiation with visible light comprising at least wavelengths in the range of 400-420 nm, i.e. blue light, without the use of a photosensitizer. At issue was whether the combination of Ashkenazi[ii] and Nitzan[iii] taught inactivation of bacteria without the use of a photosensitizer and whether there would have been a reasonable expectation of success at doing so. 

Ashkenazi concerns the photoinactivation of a Gram-positive bacterium (different from the claimed bacteria) in the presence of a photosensitizer to enhance porphyrin production (porphyrins being a molecule Ashkenazi proposed to cause cell damage from light exposure due to release of free radicals). Ashkenazi concluded from experimentation that higher inactivation of the bacteria was achieved in the presence of increased levels of the photosensitizer and thus porphyrins. Nitzan concerns the effect of supplementing a bacterial culture with added photosensitizer on the photoinactivation of Gram-positive bacteria. Nitzan tested bacteria cultures of MRSA both with and without photosensitizer. When an added photosensitizer was not present, Nitzan observed no inactivation of the bacteria cultures irradiated with 50 J/cm² of 407-420 nm light.

The PTAB found that the combination of references taught the claimed limitation of exposing the bacteria to light in the absence of a photosensitizer by relying on Ashkenazi’s teaching that increasing the dosage of light, number of illuminations, and increasing the duration of the illumination results in greater inactivation of the bacteria. The PTAB held that one skilled in the art would have expected at least “some” inactivation based on the MRSA bacteria comprising some endogenous photosensitizer, despite Nitzan reporting no inactivation of MRSA without an added photosensitizer.

In reversing the PTAB, the Federal Circuit found that the PTAB’s factual findings were not supported by substantial evidence. In particular, the Federal Circuit found that Ashkenazi and Nitzan would not reasonably teach inactivation of bacteria without a photosensitizer given that Ashkenazi teaches inactivation of bacteria in the presence of a photosensitizer and Nitzan in fact disclosed a photosensitizer-free embodiment and was “wholly unsuccessful in achieving inactivation.”

Further, while the references themselves did not teach inactivation without the use of a photosensitizer, the PTAB relied upon “Ashkenazi’s teaching that ‘blue light may’ inactivate ‘other bacterial cells that produce porphyrins’” to conclude that a skilled artisan would have expected that MRSA would exhibit “some amount” of inactivation by exposure to the claimed wavelength on the basis that MRSA produces “some level” of endogenous porphyrin.  Disagreeing with the PTAB, Federal Circuit found this to be “pure conjecture coupled with hindsight reliance on the teachings of the ’706 patent.”

According to the Federal Circuit, the “complete lack of evidence” that any bacteria were inactivated after exposure to blue light without a photosensitizer, coupled with the data of Nitzan, showing failure to inactivate MRSA via irradiation with blue light in the absence of a photosensitizer, undermined a finding of a reasonable expectation of success.

The Federal Circuit placed heavy emphasis on Nitzan’s failure to achieve inactivation in the absence of a photosensitizer, referring to their prior consideration of failure rate and lack of data or other reliable indicator of success, as it relates to a reasonable expectation of success in OSI Pharmaceuticals, LLC v. Apotex Inc.[iv] where the Federal Circuit found “the only reasonable expectation at the time of the invention was failure, not success.”

While Clear-Vu had argued that it defied 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, the Federal Circuit pointed to their holding in Otsuka Pharmaceutical Co. v. Sandoz, Inc.[v] stating that “[t]he inventor’s own path 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 evidenced by the prior art.”

There has never been a clear standard for what constitutes a reasonable expectation of success. However, we know from In re O’Farrell[vi] that “absolute predictability” has never been the requirement; the expectation must only be reasonable. Based on the data and failure in Nitzan, the Federal Circuit was unwilling to find such reasonable expectation of success in this case. The failure in Nitzan to achieve the claimed result distinguishes this case from others before it such as Pfizer. Inc. v. Apotex, Inc.,[vii] where the Federal Circuit was unwilling to equate unpredictability to patentability, stating that a reasonable (but not guaranteed) expectation of success could be found where it was “generally unpredictable as to whether a particular salt would form and what its exact properties would be.”

While the failure in Nitzan was a critical consideration in the Federal Circuit’s reversal of the PTAB’s obviousness determination, such data may not always be present in an asserted reference (whether in an obviousness challenge or rejection during prosecution).   However, the ruling from the CAFC indicates that patentees, at the time of drafting, would benefit from using data to tell their story. While examples according to the invention are helpful to explain detailed information of an invention; even more powerful may be comparative examples that can serve to provide the same type of evidence as Nitzan did in University of Strathclyde v. Clear-Vu Lighting. These comparative examples may be used to show that at the time of the invention, a reasonable expectation of success was not present.