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Failures of “prior art” undermine obviousness challenge to patent

April / May 2022 IP Newsletter

Previous research that failed couldn’t defeat a patent for an invention that succeeded. So says the U.S. Court of Appeals for the Federal Circuit, which hears all appeals of patent cases, in University of Strathclyde v. Clear-Vu Lighting, LLC.

PTAB kills patent

The patent covered a method of killing antibiotic-resistant bacteria using only visible light. Such bacteria, including Methicillin-resistant Staphylococcus aureus (MRSA), are known to cause health problems — especially in hospitals.

Photoinactivation is a method that has emerged as an effective way to kill resistant bacteria. An infection generally is treated by applying a photosensitizing agent and activating it with light energy. But the need to apply photosensitizing agents to bacteria can be a “significant practical disadvantage.”

Scientists at the University of Strathclyde in Scotland (University) discovered that application of visible light in a specific range of wavelengths was effective at inactivating bacteria without a photosensitizing agent. When their patent was challenged, the Patent Trial and Appeal Board (PTAB) found it invalid because of “prior art” — two papers published in journals — that made the method obvious and therefore unpatentable. The University appealed to the Federal Circuit.

Failures infect finding

An obviousness determination generally requires a finding that:

  1. Prior art disclosed the claimed invention, typically in two or more prior art references,
  2. Someone with ordinary skill in the field (a “skilled artisan”) would have been motivated to combine or modify the teachings in the prior art, and
  3. That person would have a reasonable expectation of success in doing so.

On appeal, the University disputed the PTAB’s findings on the first and third prongs. The Federal Circuit ruled in the University’s favor.

The court began by holding that the combination of the two papers didn’t teach the method of inactivating bacteria without using a photosensitizer. One of the papers described a method that achieved inactivation but used a photosensitizer. While the method disclosed in the other paper didn’t employ a photosensitizer, it also didn’t successfully achieve inactivation.

Because neither paper teaches nor suggests inactivation of any bacteria without using a photosensitizer, the court found no reason why a skilled artisan would choose to entirely omit a photosensitizer when combining the prior art. It then turned to the third obviousness prong.

The PTAB found that a skilled artisan would have expected that MRSA could be inactivated without a photosensitizer. The Federal Circuit, however, said that the only support for this finding was “pure conjecture coupled with hindsight reliance” on the teachings of the patent itself.

Neither of the papers, it said, provided any evidence, data or other promising information showing successful inactivation of bacteria without using a photosensitizer. Further, the court did find evidence showing that others had failed to inactivate MRSA without using a photosensitizer, despite experimenting with different light doses and wavelength ranges. Such failures, the Federal Circuit found, undermine a finding of a reasonable expectation of success.

The court also rejected the patent challenger’s argument that support for the PTAB’s finding can be found in the patent. It explained that an inventor’s “own path itself” never supports a conclusion of obviousness — what matters is the path a skilled artisan would have followed, as evidenced by the relevant prior art.

Court sheds more light

Notably, despite finding no reasonable expectation of success here, the Federal Circuit emphasized that “absolute predictability” or “guaranteed success” isn’t required to find such an expectation. But, where the prior art shows only failures to achieve what the inventor accomplished, the court couldn’t find an expectation of success based on that prior art.

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