In IPRs, secondary considerations such as unexpected results can play a determinative role in evaluating obviousness, particularly when there is a clear nexus with the claimed invention. In general, ‘differences in degree’ of a known and expected property are not as persuasive in rebutting obviousness as ‘differences in kind’ (for example, a new property dissimilar to the known property). Such was the case in Coalition for Affordable Drugs v. Pozen, Inc. (IPR2015-01718), in a decision that may leave some feeling queasy.

The patent at issue in this IPR, US 8,945,621, is directed to a method of administering a specific pharmaceutical formulation to decrease the incidence of non-steroidal anti-inflammatory drug (NSAID)-associated stomach ulcers in patients taking low-dose aspirin (LDA). Importantly, the Board found the claimed method requires administration of the composition to be “more effective at reducing incidence of NSAID-associated ulcers in patients taking LDA than in patients not taking LDA …” (claims 1, 8, 15, and 16). That limitation appeared only in a “wherein” clause, which the Board preliminarily found at institution to actually be a “whereby” clause, a critical finding to institution, but the issue was not even addressed in the final decision.

The petitioner asserted that the claimed methods would have been obvious over the combined teachings of three references. The petitioner also asserted that one of ordinary skill in the art would have expected that the claimed method would be “more effective at reducing the incidence of NSAID-associated ulcers in patients taking LDA than in patients not taking LDA,” given the teachings of a subset of the references. At trial, the petitioner demonstrated that the claimed method would have been expected to be effective in reducing the risk of gastric ulcers in patients taking both LDA and a non-aspirin NSAID.

However, the petitioner did not establish that the claimed method would have been expected to be more effective in patients taking LDA than in patients not taking LDA, as recited in the claim. As we previously discussed, the unexpected nature of this result was bolstered by the patent owner’s expert testimony and the prosecution history. Moreover, the PTAB viewed this result as a difference in kind (and thus more persuasive as to non-obviousness than a mere difference in degree) because the result is the opposite of what the ordinary artisan would have expected, in view of evidence establishing that a patient taking both LDA and a non-aspirin NSAID would have an increased risk for developing gastric ulcers compared with those taking NSAID alone. It followed that the PTAB concluded that the petitioner had not demonstrated obviousness over the three references.


Practitioners should appreciate the distinction between differences in kind and degree and recognize that differences in degree, while potentially helpful in developing an obviousness position, are generally not as strong as differences in kind. In supporting patentability (at the application drafting stage, at the prosecution stage, or in seeking to maintain an issued claim), it is advantageous for practitioners to focus, when possible, on unexpected differences in kind as secondary considerations for non-obviousness. On the flip side, challengers may bolster a case for obviousness by showing that differences (in kind or in degree) are in fact expected or not surprising to the skilled artisan.