## Facts

- Schering owned U.S. Patent No. 4,282,233, claiming the antihistamine loratadine, and marketed it as Claritin.
- Schering later obtained U.S. Patent No. 4,659,716, claiming descarboethoxyloratadine (DCL), a metabolite formed in the body after loratadine ingestion.
- After the loratadine patent expired, multiple generic manufacturers sought to market generic loratadine.
- Schering sued, alleging that marketing and use of generic loratadine infringed the later DCL patent because loratadine administration results in in vivo formation of DCL.
- The generic defendants contended that the DCL claims were invalid because the earlier loratadine patent inherently anticipated them.

## Issues

1. Whether a prior patent that discloses a drug and its administration inherently anticipates later claims directed to a metabolite necessarily produced in vivo by practicing the earlier disclosure.
2. Whether inherent anticipation requires that persons skilled in the art at the time of the earlier reference recognized the inherent metabolite.

## Decision

- The Federal Circuit affirmed summary judgment that claims 1 and 3 of the DCL patent were invalid for inherent anticipation by the loratadine patent.
- The court held that inherency applies when the claimed feature necessarily and inevitably results from practicing the prior art under normal conditions.
- The court held that inherent anticipation does not require contemporaneous recognition or appreciation of the inherent feature.
- Because ingestion of loratadine as taught in the earlier patent necessarily produces DCL, the earlier patent inherently disclosed the later-claimed metabolite.

## Legal Principles

- A claim is anticipated when a single prior-art reference discloses every claim limitation, either expressly or inherently.
- A limitation is inherent only if it is necessarily present; possibility or probability is insufficient.
- Inherent anticipation does not depend on whether the inherent characteristic was known, recognized, or appreciated at the time of the anticipating reference.
- Anticipation requires an enabling disclosure; it does not require actual reduction to practice by the prior-art reference.
- Where a prior-art drug disclosure necessarily results in a metabolite upon ordinary administration, broad compound claims to that metabolite may be inherently anticipated.

## Conclusion

The court held that claims to a drug metabolite are anticipated when practicing a prior patent’s teaching of administering the parent drug necessarily and inevitably produces the metabolite, and this is true even if the metabolite was not identified or understood when the earlier patent issued.


Schering Corp. v. Geneva Pharms., Inc., 339 F.3d 1373 (Fed. Cir. 2003)