## Facts

- Bristol owned U.S. Patent No. 4,504,657 claiming a particular crystalline form of cefadroxil (the Bouzard monohydrate), defined in part by a specified x-ray powder diffraction (XRPD) pattern and related crystalline characteristics.
- An earlier Bristol patent covering cefadroxil as a chemical compound expired in 1987; Zenith sought to market a generic cefadroxil product after that expiration.
- Zenith obtained FDA approval to sell “cefadroxil DC,” a different crystalline form (a hemihydrate) that, as manufactured, did not match the Bouzard monohydrate or the XRPD pattern recited in the asserted claims.
- Bristol contended that, although noninfringing as manufactured, Zenith’s product converted in the stomach after ingestion into the claimed Bouzard monohydrate, creating direct infringement by patients and physicians.
- Bristol asserted theories of literal infringement, infringement under the doctrine of equivalents, and inducement of infringement based on Zenith’s sales and labeling/instructions.
- Bristol’s proof relied largely on simulated conditions, expert testimony, and comparisons to a Bristol-generated “reference pattern,” rather than direct evidence that the in vivo material met the claim-recited XRPD pattern.

## Issues

1. Whether Bristol proved direct infringement (and thus inducement) on the theory that Zenith’s noninfringing product transiently converted in vivo into the claimed crystalline monohydrate.
2. Whether Bristol’s evidence sufficiently established that the alleged in vivo form satisfied the claim limitations, including the XRPD pattern recited in the patent.
3. Whether Bristol proved infringement under the doctrine of equivalents for the accused crystalline form.

## Decision

- The Federal Circuit reversed the district court’s judgment that Zenith induced infringement.
- The court held Bristol failed to prove, by a preponderance of the evidence, that ingestion of Zenith’s product resulted in formation of the claimed Bouzard monohydrate as defined by the patent claims.
- The court held Bristol also failed to establish infringement under the doctrine of equivalents.
- Because direct infringement was not proven, inducement under 35 U.S.C. § 271(b) could not stand.

## Legal Principles

- Patent infringement must be proven by comparing the accused product or method to the patent claims; proof tied to a patentee-selected reference, without a demonstrated match to claim limitations, is insufficient.
- When infringement depends on alleged in vivo chemical or physical changes, the patentee must prove that the accused product, at some point, meets each asserted claim limitation; speculation or indirect simulation evidence may be inadequate.
- The doctrine of equivalents requires proof that the accused and claimed subject matter perform substantially the same function, in substantially the same way, to achieve substantially the same result in the context of the claimed invention.
- Inducement requires proof of underlying direct infringement; absent direct infringement, there is no inducement liability.

## Conclusion

The Federal Circuit rejected an inducement theory based on alleged transient in vivo conversion where the patentee did not connect its proof to the claim-recited XRPD limitations and did not establish equivalence; without direct infringement, inducement failed as a matter of law.


Zenith Lab'ys, Inc. v. Bristol-Myers Squibb Co., 19 F.3d 1418 (Fed. Cir. 1994)