In re Papesch
United States Court of Customs and Patent Appeals
315 F.2d 381 (1963)
Papesch (Papesch) applied for a patent claiming a class of chemical compounds admittedly obvious in their structure compared to prior-art compounds — differing only by replacing three CH3 groups. Papesch supported the application with specification text and an expert affidavit showing the compounds had unexpected pharmacological properties. The examiner rejected the claims anyway, suggesting Papesch instead claim the compounds' use for their unexpected medical purpose rather than their chemical structure, and the Board of Patent Appeals affirmed, disregarding the affidavit evidence of unexpected results. Papesch appealed.
Whether unexpected physical properties of otherwise obvious chemical compounds can serve as grounds for patentability.