Ethyl, methyl, butyl…futile – the running joke in grad school. Just try a different substituent until you find an active compound – or not. But while tweaking an alkyl substituent might seem “obvious” in the lab, when it comes to patent protection of small molecules, is it necessarily obvious? When examining a patent application with claims directed to novel chemical compounds, an examiner may reject those claims under 35 U.S.C. § 103 as obvious over structurally similar compounds in the prior art. Likewise, an accused infringer will often allege that the asserted claims to chemical compounds are “obvious” when challenging the validity of a patent. Successfully overcoming a charge of obviousness can be critical where the compound(s) in question are clinical candidates or are already highly successful commercial therapeutics. So how can you defeat those assertions?

Obviousness Before KSR

While the concept of obviousness seems intuitive, it is not easily defined. Fortunately, the Supreme Court provided some guidance in the form of a framework that can be used when considering the obviousness of a claim. The seminal case of Graham v. John Deere Co. of Kansas City1 counsels that the following factors be considered in any obvious analysis: 1) the scope and content of the prior art, 2) the differences between the claimed subject matter and the prior art, 3) the level of ordinary skill in the art, and 4) any secondary considerations such as commercial success, long-felt but unresolved need, failure of others, etc.