What did They do Differently? Functional Claim Language Overcomes Obviousness finding at PTAB

Written By: Andrew Berks

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Univ. Strathclyde v. Clear-Vu Lighting LLC, No. Case: 20-2243 (Fed. Cir. Nov. 4, 2021)

A rejection based on obviousness can be a difficult rejection for patent applicants to overcome. In patent prosecution, an examiner who can find a reference or combination of references that supposedly incorporates the claimed invention can result in a stubborn obviousness rejection. The patent practitioner will, in turn, argue that one or more features of the combination of references distinguishes the prior art. However, it is often frustrating when the practitioner articulates differences over the combination of references, and the patent examiner discounts these differences.

Here, the Federal Circuit agreed with the patentee that this invention was distinguished from the prior art and reversed a PTAB decision invalidating the patent. This case shows that certain prosecution strategies, to wit, functional claim language can be a valuable tool for applicants.

The inventors of U.S. Patent No. 9,839,706 discovered that Methicillin-resistant Staphylococcus aureus (MRSA) can be inactivated by exposure to light at an optimum wavelength of 405 nm without the use of a photosensitizer. Slip op. at 3. Claim 1 of the ‘706 patent recites:

1. A method for disinfecting air, contact surfaces or materials by inactivating one or more pathogenic Gram-positive bacteria in the air, on the contact surfaces or on the materials, [by] exposing the one or more pathogenic Gram-positive bacteria to visible light without using a photosensitizer, ... and wherein a portion of the visible light that inactivates the one or more pathogenic Gram-positive bacteria consists of wavelengths in the range 400-420 nm ...

Slip. Op. at 4. More specifically, the Strathclyde inventors found that at 405 nm, MRSA was inactivated at 45 J/cm2.

Patent challenger Clear-Vu filed an Inter Partes Review and obtained a Final Written Decision finding the claims obvious over Ashkenazi in view of Nitzan, which are both journal papers. Strathclyde appealed this PTAB decision.

Ashkenazi reported that inactivation of Gram-positive P. acnes was inactivated at the same wavelengths claimed by the ‘706 patent but found that a photosensitizer, δ-aminolevulinic acid (ALA), was much more effective than treatment without the ALA.

The Nitzan paper continued the study of the Ashkenazi paper, and found that MRSA cultures (a different bacteria than P. acnes) were inactivated efficiently where ALA was in the culture at 407–420 nm, but were not inactivated in cultures without ALA.

In the Final Written Decision of the Inter Partes Review, the Board found that Ashkenazi and Nitzan taught or suggested all limitations of claims 1 and 3, and that a person of ordinary skill in the art (POSA) would have been motivated to combine these two references and “would have had a reasonable expectation of successfully doing so.” Even though neither Ashkenazi nor Nitzan achieved inactivation of any bacteria without using a photosensitizer and, as the Board found, Nitzan failed to achieve any inactivation when it exposed MRSA to 407–420 nm light without applying a photosensitizer, the Board nonetheless found that a skilled artisan would have reasonably expected “some” amount of inactivation because the claims “do not require any specific amount of inactivation.” Slip op. at 8.

On appeal, the Federal Circuit panel (Judges Reyna, Clevenger, and Stoll) addressed whether (1) the combination of Ashkenazi and Nitzan teaches inactivating one or more Gram-positive bacteria without using a photosensitizer, and (2), whether there is a reasonable expectation of success.

The Combination of References Does Not Disclose the Invention
The panel notes that in Ashkenazi, all cultures had a photosensitizer, either ALA or riboflavin. Nothing in Ashkenazi disclosed or suggested inactivating bacteria without using a photosensitizer. Nitzan had an example in which MRSA and other bacteria were exposed to 407–420 nm blue light without a photosensitizer, but Nitzan did not achieve inactivation of bacteria in these conditions.
Since neither Ashkenazi nor Nitzan teach or suggest inactivation of any bacteria without using a photosensitizer, the panel failed to see why a skilled artisan would opt to entirely omit a photosensitizer when combining these references. The panel complained that the Board articulated no rational basis for combining Ashkenazi’s P. acnes experiments, which at all times used a photosensitizer, with Nitzan’s non-ALA MRSA experiment, which did not achieve inactivation, to arrive at an embodiment in which MRSA is inactivated by exposing it to 407–420 nm blue light without using a photosensitizer. Nitzan disclosed such a photosensitizer-free embodiment and was unsuccessful in achieving inactivation.

The panel therefore found that Clear-Vu’s arguments were not supported by substantial evidence. No reasonable fact-finder would find that the combination of Ashkenazi and Nitzan discloses inactivating one or more Gram-positive bacteria without using a photosensitizer.

Reasonable Expectation of Success Fails to Cure
The panel complained that the Board’s finding that a POSA would have a reasonable expectation of success is hindsight. The argument from Clear-Vu relied on the presence of endogenous porphyrins in Gram-positive bacteria, and a statement in Ashkenazi that “blue light may inactivate other bacterial cells that produce porphyrins,” (slip op at 13, cleaned up). But, the panel found there was no evidence to support this assumption. Rather, the evidence pointed to the opposite. The Board dismissed evidence from Nitzan because that paper used lower energy levels than Ashkenazi, reasoning that a POSA would increase the energy levels to those used in Ashenazi and could achieve inactivation of bacteria.

The panel found there was a lack of evidence in the record that the prior art references show any bacteria were inactivated after exposure to 407–420 nm blue light without using a photosensitizer, despite experimenting with different light doses and different wavelength ranges of blue light. “The inventor’s own path itself 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 pertinent prior art.” Otsuka Pharm. Co., v. Sandoz, Inc., 678 F.3d 1280, 1296 (Fed. Cir. 2012) (slip op. at 18). Thus, there was no reasonable expectation of success, and the panel reversed the PTAB on both grounds.

One point of concern is that the differences between Nitzan and the ‘706 invention are unclear. The ‘706 patent discloses inactivation of MRSA with 405 nm blue light at 45 J/cm2, yet data recited in the opinion suggests that Nitzan looked at this energy level and found no inactivation. The panel opinion does not specifically articulate what the ‘706 patent did differently, however, it seems that the ‘706 patent focused specifically on light at 405 nm. Using modern tuned LED light sources, this may be possible, and it may have been more difficult with Ashkenazi and Nitzan if they were older studies using light filters and less focused light sources. But, it is not clear from the opinion if the ‘706 patent has a claim to the 405 nm wavelength specifically.

Prof. Dennis Crouch in Patently-O believes that the “inactivating” language in claim 1 should not be given patentable weight because it does not add any specific structure or acts over the prior art. As noted in the foregoing paragraph, the ‘706 inventors must have done something different than Nitzan, but from the opinion we don’t know what that is, and the differences (if any) are not in the representative claim recited in the opinion. So Prof. Crouch makes a good point. Incidentally, this point was not raised (apparently) by the PTAB, the Federal Circuit panel, or Clear-Vu.

However, the Federal Circuit panel focused on the combination of references and found that Ashkenazi and Nitzan did not teach the claimed invention, and if anything, taught away from the claims. The PTAB opinion did not articulate substantial evidence that the combination of references gave the claimed results, so the functional language here was key—the ‘706 patent achieved inactivation where Nitzan without a photosensitizer did not.

about the authors

Andrew Berks


Andrew Berks is a partner in the firm's Intellectual Property Law practice, where he focuses on patent law, intellectual property transactions, and patent prosecution. In addition to his Ph.D. in chemistry, Andrew has significant work experience in the pharmaceutical and biotechnology sectors. He counsels clients in securing and defending their intellectual property in the areas of chemistry, biotechnology, pharmaceuticals, medical devices, engineering, electronics, and software.

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