## Facts

- AstraZeneca marketed Toprol-XL, an extended-release metoprolol succinate product for cardiovascular indications.
- Generic manufacturers filed ANDAs seeking approval to sell generic versions of Toprol-XL, prompting consolidated patent infringement actions.
- Two related patents issued in 1992 from a common priority chain originating in a Swedish application: (1) Astra’s ’154 patent claiming only the compound “metoprolol succinate,” and (2) Lejus’s ’318 patent claiming extended-release pharmaceutical preparations using metoprolol succinate as the active ingredient.
- Inventorship and ownership of the underlying application family were disputed in Sweden and resolved by settlement dividing rights: Astra obtained divided claims directed to the compound, while Lejus retained claims directed to extended-release preparations.
- In the multidistrict litigation, generic defendants sought summary judgment that Astra’s ’154 patent was invalid for obviousness-type double patenting over the earlier-issued ’318 patent, focusing on claim 8 of the ’318 patent.
- The district court granted summary judgment, finding the ’154 patent void for double patenting because its claim was not patentably distinct from claim 8 of the ’318 patent.
- Astra appealed to the Federal Circuit.

## Issues

1. Whether a later claim to the compound metoprolol succinate is invalid for obviousness-type double patenting over an earlier claim to an extended-release dosage form that releases metoprolol succinate.
2. Whether contractual division of ownership and claim rights within a common patent family affects application of obviousness-type double patenting.

## Decision

- The Federal Circuit affirmed summary judgment that the ’154 patent is invalid for obviousness-type double patenting over claim 8 of the ’318 patent.
- The court held the later compound claim was not patentably distinct from the earlier extended-release formulation claim because practicing the earlier claim necessarily required use of metoprolol succinate.
- The court rejected the argument that the parties’ settlement-based allocation of claims and ownership avoided double patenting concerns, emphasizing the doctrine’s role in preventing unjustified extension of exclusivity.

## Legal Principles

- Obviousness-type double patenting bars a later-expiring patent claim that is an obvious, patentably indistinct variation of an earlier patent’s claim, to prevent timewise extension of the right to exclude.
- The inquiry is conducted on a claim-to-claim basis, comparing the later claims against the earlier claims rather than the specifications.
- A later claim is not patentably distinct when the earlier claim’s practice inherently or necessarily requires what the later claim covers, such that upholding the later claim would prolong exclusivity for the same or an obvious variant of the invention.
- Private agreements allocating claims or ownership within related applications do not control the public-law limitations imposed by obviousness-type double patenting.

## Conclusion

The Federal Circuit held Astra’s single compound claim to metoprolol succinate invalid because an earlier patent claim covering an extended-release tablet releasing metoprolol succinate rendered the later compound claim patentably indistinct, and allowing it would improperly extend exclusivity beyond the earlier patent’s term.


In re Metoprolol Succinate Patent Litigation, 494 F.3d 1011 (Fed. Cir. 2007)