Background
The University of Strathclyde, a Scottish research university, holds patents covering methods of inactivating antibiotic-resistant bacteria — specifically, using blue light to kill bacteria like methicillin-resistant Staphylococcus aureus (MRSA) without the use of photosensitizing agents (chemical compounds that are typically added to enhance light-based antibacterial treatments). The invention is significant because it achieves antibacterial photoinactivation without introducing the additional chemical agents that can complicate clinical use.
Clear-Vu Lighting LLC filed inter partes review petitions challenging the validity of Strathclyde’s patents as obvious. Clear-Vu argued that prior art references, taken together, would have led a person of ordinary skill to combine the teachings and arrive at the claimed invention with a reasonable expectation of success. The PTAB agreed and found the claims unpatentable. Strathclyde appealed.
The Court’s Holding
The Federal Circuit reversed, holding that the PTAB’s obviousness finding was not supported by substantial evidence. The court focused on the “reasonable expectation of success” element of the obviousness analysis — the requirement that a person of ordinary skill in the art, at the time of the invention, would have had reason to believe that combining the prior art references would produce the claimed result.
The court found that the prior art references cited by Clear-Vu did not actually demonstrate that blue light could inactivate antibiotic-resistant bacteria without photosensitizing agents. Rather, the prior art either used photosensitizing agents or addressed different bacterial strains under different conditions. Because the cited references did not themselves achieve the claimed result, a skilled artisan looking at that prior art would have had no basis to expect success in attempting the claimed combination. The PTAB’s finding that a skilled artisan would have had a reasonable expectation of success was not supported by the record evidence, and the court vacated the Board’s unpatentability findings and remanded.
Key Takeaways
- Obviousness requires not just that prior art references can be combined, but that a person of ordinary skill would have had a “reasonable expectation of success” in achieving the claimed result from that combination — and that expectation must be grounded in what the prior art actually teaches.
- Prior art references that do not themselves achieve the claimed result cannot supply the necessary evidentiary foundation for a finding that a skilled artisan would expect success in combining those references to reach that result.
- PTAB obviousness findings are reviewed for substantial evidence, and where the record does not show that the prior art supports the expectation of success, the Federal Circuit will reverse even if the prior art generally addresses related problems.
- For patents covering unexpected biological or chemical outcomes — such as achieving antibacterial activity without photosensitizers — the reasonable expectation of success analysis can be a powerful validity defense if the prior art failed to predict or achieve the claimed result.
Why It Matters
The Strathclyde decision is an important reminder that obviousness is not just about whether prior art references can be combined in hindsight — it is about whether a skilled artisan at the time of the invention would have expected the combination to work. This distinction is especially important in life sciences and materials science patents, where unexpected results are common and where prior art in adjacent fields may not provide a reliable guide to success in a new application.
For university and research institution patent owners, the case reinforces that patents covering genuinely novel scientific discoveries — particularly those that achieve results the prior art suggested would be difficult or impossible — can survive IPR challenges if the petitioner cannot point to prior art that actually supports an expectation of success. The reasonable expectation of success requirement is a meaningful limitation on the reach of obviousness as an invalidity ground.