In Novo Nordisk v. Caraco Pharmaceutical, the Federal Circuit affirmed in part and reversed in part a ruling by the District Court for the Eastern District of Michigan determining a combination therapy patent was invalid as obvious and unenforceable due to inequitable conduct. The patented drug combined the most common insulin secretagogue and insulin sensitizer and claimed an unexpected synergy from the combination.

Novo filed a patent application for the combination therapy, which the examiner rejected four times on obviousness grounds. Novo filed a fifth response presenting additional study results of scientist Dr. Sturis via a declaration that also included assertions from Novo's counsel Dr. Bork that the combination resulted in unexpected synergistic results in the treatment of diabetes. The examiner then withdrew her rejection based on the declaration.

On appeal, the Federal Circuit affirmed the district court's ruling in regards to obviousness stating Caraco proved by clear and convincing evidence that an artisan would have expected the level of synergy Novo found in its combination therapy. The Federal Circuit rejected Novo's argument asserting the district court misallocated the burden of persuasion by forcing Novo to "overcome" Caraco's "prima facie" case of obviousness. The CAFC reasoned that the burden of persuasion never shifts to the patentee during the course of a district court obviousness challenge, however the patentee still needs to provide some rebuttal in order to overcome challenger's prima facie case.

Furthermore, the Federal Circuit reversed the district court ruling in regards to inequitable conduct. The CAFC found that Dr. Sturis' omissions of an original test protocol and Dr. Bork's statement that test results were "clear evidence of synergy" were troubling, but did not rise to the level 'but-for' materiality under the Therasense standard.

Author: Aiyda Ghahramani (summer law clerk)