In re Metoprolol Succinate Patent Litigation (Fed. Cir. 2007).
Astra holds the patent on Toprol-XL (Metoprolol succinate) and sued several generic ANDA filers. On summary judgment, a Missouri Federal court held Astra’s patent invalid for improper obvious-type double patenting and unenforceable. Astra appealed for inequitable conduct during prosecution.
Double-Patenting: A later patent claim will be invalid for obviousness-type double patenting if it is not patentably distinct from an earlier claim from a commonly-owned patent. This analysis involves construction of both sets of patent claims.
[T]he critical inquiry remains whether the claims in the [prior] application define an obvious variation of the invention claimed in the … patent [at issue].
Normally, obviousness-type double patenting is avoided by filing a terminal disclaimer. Here, however, a secret inventorship and ownership dispute prevented such action.
Inequitable Conduct: On summary judgment, the district court also found the patent unenforceable based on Astra’s failure to notify the PTO of the inventorship dispute during prosecution. Inequitable conduct, however, is rarely found on summary judgment. Here, the CAFC saw potential holes in proof of intent — finding that the “district court erred in equating the presence of an incentive with an intent to deceive on summary judgment.”
Dissent: Judge Schall dissented