The Federal Circuit Court of Appeals reversed a decision of the U.S. Patent Trial and Appeal Board (“Board”), finding a patent on a method of disinfection obvious. The reversal was based in part on a finding that the Board’s determination of a “reasonable expectation of success” in combining the teachings of two prior art references was not supported by substantial evidence. See Univ. of Strathclyde v. Clear-Vu Lighting LLC , No. 2020-2243, 2021 U.S. App. LEXIS 32872, *1 (Fed. Cir. Nov. 4, 2021). In litigating obviousness in court or before the Board, remember that it is not enough to identify all of the claim limitations in the cited prior art references. The facts (which may include expert testimony) must demonstrate that “that a person of ordinary skill in the art would have been motivated to combine or modify the teachings in the prior art and would have had a reasonable expectation of success in doing so.” Id. at *11.

Patented Method for Photoinactivating Antibiotic-Resistant Bacteria

The patent, owned by the University of Strathclyde, had claims directed to a method for photoinactivating antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (“MRSA”) and other Gram-positive bacteria, using a photosensitizing agent. The inventors had found that wavelengths in the 400–500 nm region provided a high rate of MRSA inactivation. The inventors concluded that “visible-light exposure over the wavelength range 400–450 nm is the major inducing factor for Staphylococcal [e.g., MRSA] inactivation, with increased inactivation occurring over the range 400–420 nm and optimum inactivation occurring at 405 nm.” Id. at *3. Illustrative claim 1 disclosed a method for disinfecting air, contact surfaces, or materials by exposing the Gram-positive bacteria to visible light without using a photosensitizer where a portion of the visible light is in the range 400-420 nm.

The Federal Circuit Reversed the Board’s Determination of Obviousness

The Board found the illustrative claim obvious over two prior art references. The primary dispute was whether the prior art taught exposing bacteria to light without using a photosensitizer. The Federal Circuit concluded that the Board erred in finding that the two references taught or suggested all of the limitations of the illustrative claim, and specifically that the “combined teachings” of the references disclosed exposing bacteria to light without using a photosensitizer. The Federal Circuit held that the Board’s finding that the combined references taught this limitation was not supported by substantial evidence. Because neither reference taught or suggested “inactivation of any bacteria without using a photo-sensitizer,” the court failed “to see why a skilled artisan would opt to entirely omit a photo-sensitizer when combining these references.” Id. at *14 (emphasis added). In fact, the Board, having relied on a conclusory expert opinion, articulated no rational basis for its finding.

Further, the Federal Circuit also disagreed with the Board’s conclusion that a person of ordinary skill in the art would have had a reasonable expectation of successfully combining the references. The Board had determined that a person of ordinary skill would have had a reasonable expectation of “inactivating MRSA using 407–420 nm light without applying a photo-sensitizer based on the combined teachings” of the references. Id. at *16. Neither reference, however, achieved inactivation of any bacteria without using a photosensitizer and one of the references detailed a failed attempt to inactivate bacteria under that condition. The Federal Circuit found that the references lacked evidence, data or “other promising information” showing successful inactivation of any bacteria without using a photosensitizer. The references therefore lacked a suggestion “that a skilled artisan would reasonably expect that MRSA or one of the other claimed Gram-positive bacteria could be inactivated upon exposure to 407–420 nm blue light without using a photosensitizer.” Id. The Board’s finding of likelihood of success therefore was not supported by substantial evidence.