## Facts

- A Patent and Trademark Office interference (No. 101,111) involved competing claims to a class of angiotensin-converting-enzyme (ACE) inhibitor compounds described in a single generic count.
- The count broadly covered optionally esterified carboxyalkyl substituted dipeptides in which an “indanyl” group (including 2-indanyl and 5-indanyl variants) was required, and their pharmaceutically acceptable salts.
- Oka was the senior party based on a Japanese patent filing date of October 31, 1980, asserted as an effective U.S. date under 35 U.S.C. § 119.
- Youssefyeh, as junior party, attempted to prove an earlier invention date under pre-AIA 35 U.S.C. § 102(g) by establishing earlier conception (and reduction to practice or diligence).
- On February 27, 1980, a junior party inventor’s notebook reflected a broad structural concept encompassing a large class of 2-indanyl glycines, but the record did not show an operative method to make the relevant compounds at that time.
- By October 10, 1980, a method existed for making related compounds, but the dispute centered on whether the inventors had recognized it as applicable to make the specific indanyl compounds within the count.
- During the last week of October 1980, a junior party inventor directed an assistant to apply the October 10 method to prepare a 5-indanyl species; the assistant later made a 5-indanyl compound in December 1980.
- The junior party’s asserted actual reduction to practice occurred no earlier than January 9, 1981.
- The Board of Patent Appeals and Interferences awarded priority to Youssefyeh, effectively crediting conception by October 10, 1980; Oka appealed.

## Issues

1. Whether the junior party proved conception before October 31, 1980 by showing both a definite idea of the claimed chemical structures and possession of an operative method of making them.
2. Whether the board clearly erred by treating October 10, 1980 as the conception date when the method’s applicability to the claimed indanyl compounds had not been recognized.
3. Whether proof of conception stated only as a time span (e.g., “last week of October 1980”) can establish an invention date earlier than the last day of that period for priority purposes.

## Decision

- The Federal Circuit reversed the board’s award of priority to the junior party.
- The court held the junior party failed to prove conception earlier than the senior party’s October 31, 1980 effective date.
- The February 27, 1980 notebook evidence showed, at most, a general research concept without an operative method to make the claimed compounds.
- The existence of a method on October 10, 1980 did not establish conception because the inventors had not recognized it as usable to make the specific compounds within the count.
- Evidence placing conception in the “last week of October 1980” could not be credited earlier than the last day of that period; at best it tied October 31, 1980.
- Because the junior party’s actual reduction to practice occurred after October 31, 1980, it could not establish priority over the senior party’s effective filing date.
- In a tie on the critical date, the senior party retained priority.

## Legal Principles

- In chemical invention priority disputes, conception requires both (1) a definite idea of the chemical structure of the claimed compound(s) and (2) possession of an operative method of making them.
- Possession of a synthetic method is insufficient unless the inventor recognizes and appreciates that the method can produce the particular claimed compounds.
- A party asserting conception must prove it to a specific date; if the evidence establishes only a range, the activity is not credited earlier than the last day of that range.
- In an interference, the junior party bears the burden to prove earlier invention than the senior party’s effective date; failing to antedate that date leaves priority with the senior party.

## Conclusion

The Federal Circuit held that the junior party did not carry its burden to antedate the senior party’s October 31, 1980 effective filing date because it failed to show, by a provable earlier date, simultaneous possession of the claimed compound structures and an operative, recognized method of making them; any showing confined to a late-October time span could not beat (and at most equaled) the senior party’s date, so priority remained with the senior party.


Oka v. Youssefyeh, 849 F.2d 581 (Fed. Cir. 1988)