## Facts

- Eli Lilly owned patents relating to fluoxetine hydrochloride, the active ingredient in Prozac.
- The asserted patents included a method-of-treatment claim in U.S. Patent No. 4,314,081 and a method claim in U.S. Patent No. 4,626,549, claim 7, directed to blocking serotonin uptake in the brain using fluoxetine hydrochloride.
- Generic manufacturers (including Barr) filed ANDAs seeking FDA approval to market generic fluoxetine hydrochloride.
- Lilly sued under 35 U.S.C. § 271(e)(2)(A), alleging that the ANDA filings infringed Lilly’s asserted claims.
- Defendants argued invalidity based on failure to disclose the best mode under 35 U.S.C. § 112 and obviousness-type double patenting as to claim 7 of the later patent.
- The district court granted summary judgment for Lilly on best mode and double patenting, and also held defendants were entitled to a jury trial on invalidity counterclaims.
- On appeal after rehearing-related modification, the Federal Circuit affirmed the best-mode rulings, reversed on double patenting as to claim 7, and affirmed the jury-trial ruling.

## Issues

1. Whether the asserted claims were invalid for failure to disclose the best mode, including alleged preferences for a precursor synthesis route and a recrystallization solvent.
2. Whether claim 7 of the later patent was invalid for obviousness-type double patenting over the earlier patent’s method-of-use claims.
3. Whether defendants were entitled to a jury trial on patent invalidity counterclaims.

## Decision

- The court affirmed that the asserted claims complied with the best mode requirement.
- The court held claim 7 of the later patent invalid for obviousness-type double patenting over the earlier patent and reversed the district court on that issue.
- The court affirmed that defendants were entitled to a jury trial on their invalidity counterclaims.
- Disposition: affirmed in part and reversed in part.

## Legal Principles

- Best mode requires (1) determining whether the inventor had a preferred mode of practicing the claimed invention at filing, and (2) whether the specification adequately disclosed that mode so a skilled artisan could practice it; invalidity turns on concealment of the preferred mode.
- The best mode obligation does not require disclosure of every operational preference; the focus is whether a truly preferred mode of practicing the claimed invention was withheld.
- Obviousness-type double patenting bars a later-expiring claim that is not patentably distinct from an earlier claim, preventing unjustified term extension through obvious variations.
- In assessing obviousness-type double patenting, courts compare claims to determine whether the later claim merely restates or makes an obvious variation of the earlier claimed invention, even if framed in different physiological or mechanistic terms.
- Patent invalidity counterclaims may carry a Seventh Amendment jury-trial right when they are legal in nature.

## Conclusion

The Federal Circuit upheld Lilly’s patents against best-mode challenges but invalidated the later patent’s claim covering serotonin-uptake blocking as an impermissible extension of exclusivity because it was not patentably distinct from the earlier fluoxetine method claims, while also confirming defendants’ right to a jury trial on invalidity counterclaims.


Eli Lilly & Co. v. Barr Labs., Inc., 251 F.3d 955 (Fed. Cir. 2001)