United States: CAFC Affirmed PTAB's Decision On Obviousness Of Method Claims

Last Updated: November 9 2016
Article by King L. Wong

There are a number of statutory requirements for patentability of inventions. One of the requirements is that the invention is not obvious over the prior art to one of ordinary skill in the art. Whether a claimed invention would have been obvious over the prior art is one of the most common challenges made against patents. This post discusses a recent opinion of the U.S. Court of Appeals for the Federal Circuit (CAFC) concerning whether the method claims in a patent application were unpatentable due to obviousness. The case is In re: Efthymiopoulos, a decision rendered by CAFC on October 18, 2016.

The claims were directed toward methods for treating influenza infections. The representative claim is summarized below.

14. A method for treating a human suffering from flu, comprising administering zanamivir by inhalation through the mouth alone.

The claims were rejected by the Examiner as obvious over the prior art, and the rejection was affirmed by the PTAB. The claims were rejected as obvious over prior art Reference I, in view of prior art Reference II and a number of other prior art references. Reference I discloses a method of treating flu by administering a chemical via inhalation such as inhalation through the nose, wherein the chemical has a chemical structure almost identical to zanamivir (the chemical differing from zanamivir only in having a methyl group instead of hydrogen). Reference II discloses using zanamivir for treating flu via inhalation through the nose. The prior art differs from the claims in not teaching administering zanamivir via inhalation through the mouth only to treat flu. The Examiner asserted that it is known that the flu is an infection of the lungs, and compared with inhalation via the nose, inhalation via the mouth delivers a higher dose of a drug to the lungs. The Examiner therefore rejected the claims as obvious over the prior art. The PTAB took the position that the disclosure by Reference I in administering the chemical via inhalation "is reasonably understood to disclose inhalation by either the nose alone, mouth alone, or both." The obviousness rejections were affirmed by PTAB.

The CAFC agreed with PTAB that there was substantial evidence to support the conclusion that, when the prior art teaches administration of the drug through "inhalation," that includes inhalation through the mouth. The court pointed out that, as noted by PTAB, because the prior art does not limit the administration via inhalation through the nose only, and inhalation is known to take place via the mouth or the nose, the disclosure of "inhalation" by the prior art would not exclude inhalation via the mouth. Both References I and II disclose that the drugs could be administered in a dry powder form via an inhaler.

There was evidence that drugs in dry powder form were commonly administered through inhalation via the mouth. The CAFC also pointed out that there was reasonable expectation that administering zanamivir by inhalation through the mouth only would succeed in treating the flu because some of the strains of the flu virus were known to attack the lower respiratory tract and inhalation via the mouth would deliver a higher dose of the drug to the lungs. The CAFC therefore concluded that the prior art would have rendered the claimed method prima facie obvious.

The applicant also argued that they had submitted experimental evidence to show that the claimed method produced unexpected results, which should overcome any prima facie case of obviousness. However, the CAFC was not persuaded, and agreed with the PTAB's conclusion that the applicant's data allegedly supporting an "unexpected result" were not convincing because the data were not generated in comparison with the closest prior art. In view of the failure of the experimental evidence to rebut the prima facie obviousness, the CAFC affirmed the decision of the PTAB in holding that the claims were unpatentable as obvious over the prior art.


This case illustrates the importance of proper evidence of secondary considerations such as unexpected results. If any experimental studies are performed in an attempt to gather data to show unexpected results, the studies must compare the claimed invention with the relevant disclosures of the closest prior art. Any experimental comparison with the prior art that is not the prior art closest to the claimed invention would very likely not be accepted by PTAB and CAFC as persuasive to overcome any prima facie obviousness.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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King L. Wong
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