Claim Drafting Tip: Written Description and Obviousness of Claims with Functional Features — Two Sides of the Same Coin

A recent precedential decision by the United States Federal Circuit (Nuvo Pharmaceuticals v DR. Reddy’s Laboratories (Fed Cir, No 17-2473, 15 May 2019) has provided valuable advice on the balance between obviousness and written description.  The decision reversed a final judgement of a District Court Bench Trial that found function-limited claims in US 6,926,907 and US 8,557,285 to be non‑obvious and to satisfy the written description requirements.


The claims at issue related to a tablet containing a nonsteroidal anti-inflammatory drug (NSAID) core and an enteric coating containing an acid inhibitor (such as a protein pump inhibitor (PPI)) in an amount effective to increase the pH of the gastrointestinal tract to at least 3.5 and prevent NSAID-related gastric injury.  Importantly, neither patent specification provided any experimental data indicating that the result specified by the functional limitation was achieved.

The lower Court found that the written description requirement was satisfied and that it was non-obvious to use a PPI to prevent NSAID-related gastric injury, and that persons of ordinary skill in the art were discouraged by the prior art from using uncoated PPI and would not have reasonably expected it to work. However, in the absence of experimental data, this reasoning was detrimental to the issue of written description before the Federal Circuit, which stated:

In light of the fact that the specification provides nothing more than the mere claim that uncoated PPI might work, even though persons of ordinary skill in the art would not have thought it would work, the specification is fatally flawed. It does not demonstrate that the inventor possessed more than a mere wish or hope that uncoated PPI would work, and thus it does not demonstrate that he actually invented what he claimed. (emphasis added)

In reaching the decision, the Federal Circuit confirmed that complying with the written description requirement, while not requiring experimental data ‘demonstrating effectiveness’, requires more than a mere statement in the specification.  Rather, the specification must demonstrate that the inventor was in possession of the claimed invention.  The Federal Circuit carefully explained that even in cases where written description has been found to be inherently established by way of the enablement of the claim (i.e. the specification described the making and using of an invention), there was some experimental evidence in the specification supporting written description.

In the case at issue, in view of the lack of experimental data and the lack of expectation of the person of ordinary skill in the art, written description could not be established.  As stated by the Federal Circuit:

Based on the specific facts of certain cases, it is unnecessary to prove that a claimed pharmaceutical compound actually achieves a certain result. But when the inventor expressly claims that result, our case law provides that that result must be supported by adequate disclosure in the specification. In this case, the inventor chose to claim the therapeutic effectiveness of uncoated PPI, but he did not adequately describe the efficacy of uncoated PPI so as to demonstrate to ordinarily skilled artisans that he possessed and actually invented what he claimed. (emphasis added)

Thus, Patent Practitioners should carefully consider the inclusion of functional features in a claim if there is insufficient relevant experimental evidence included in the specification (or provided by the inventor at the time of drafting).

Best Practice Tip:  Claims reciting functional features upon which the non-obviousness of the subject could ultimately turn should be supported by at least some experimental evidence related to achieving the result claimed.  In other words, a functional feature in a claim should be drafted in consideration of supporting experimental evidence.