# The Metabolite Problem: Schering v. Geneva and Inherent Anticipation of What the Body Makes

> The Federal Circuit held that a prior patent on a drug inherently anticipated a later patent on the metabolite the body inevitably produces, even though no one knew the metabolite existed.

Topic: Patents  |  Author: Lidiia Levitska  |  Source: Intellectual Property Law (outsideipcounsel.com)
Canonical: https://outsideipcounsel.com/blog/schering-v-geneva-inherent-anticipation-metabolite/


When a patient swallows a drug, the body often transforms it into other compounds. *Schering Corp. v. Geneva Pharmaceuticals, Inc.*, 339 F.3d 1373 (Fed. Cir. 2003), confronted the patent consequences of that biological fact. Schering had patented loratadine, the antihistamine sold as Claritin, and years later patented a compound the body produces when it processes loratadine. The Federal Circuit, in an opinion by Judge Randall Rader, held that the earlier loratadine patent inherently anticipated the later metabolite patent, even though no one knew the metabolite existed when the first patent issued. The case stands as the canonical statement that inherent anticipation does not require anyone to have recognized the inherent feature.

## At a glance

- **Case:** *Schering Corp. v. Geneva Pharmaceuticals, Inc.*, 339 F.3d 1373 (Fed. Cir. 2003).
- **Court:** U.S. Court of Appeals for the Federal Circuit; opinion by Circuit Judge Rader.
- **Posture:** Appeal from the District of New Jersey, which on summary judgment held the asserted claims invalid as inherently anticipated; rehearing en banc was later denied.
- **Holding:** A prior-art patent on loratadine (the '233 patent) inherently anticipated claims to its metabolite descarboethoxyloratadine (DCL) in a later patent (the '716 patent) under 35 U.S.C. § 102, because ingesting loratadine necessarily and inevitably produces DCL in the body.
- **Significance:** Confirmed that inherent anticipation requires only that the missing feature be the natural result of the prior art, not that it have been appreciated or recognized at the time.

## The two patents and the generic challenge

Schering held U.S. Patent No. 4,282,233 (the '233 patent), which covered loratadine, and later obtained U.S. Patent No. 4,659,716 (the '716 patent), claims 1 and 3 of which covered descarboethoxyloratadine, or DCL, a metabolite of loratadine. DCL is not something a manufacturer adds; it forms in the human body as a natural consequence of metabolizing loratadine. The '233 patent had expired, opening loratadine to generic competition, but the '716 patent on the metabolite would not expire for years.

Geneva and other generic makers sought to market loratadine and argued that the later metabolite patent was invalid. Their theory was straightforward: the '233 patent already disclosed loratadine, and since taking loratadine inevitably generates DCL, the earlier patent inherently disclosed the metabolite too. If so, the '716 claims to DCL lacked novelty. Schering countered that the '233 patent never mentioned DCL, that DCL had not even been identified when the '233 patent issued, and that a feature no one knew about could not anticipate anything.

## Inherent anticipation without recognition

The court sided with the generics, and in doing so clarified the law of inherent anticipation. A reference anticipates a claim when it discloses, expressly or inherently, every limitation of the claim. The inherent variety reaches features that are not stated but are "necessarily present" in the prior art. The decisive question, Judge Rader explained, is not whether anyone perceived the feature but whether it is the natural and inevitable result of what the reference describes. Because the human body necessarily produces DCL whenever it metabolizes loratadine, the formation of DCL was an inevitable consequence of practicing the '233 patent's disclosure.

That meant the lack of contemporaneous knowledge was irrelevant. Inherent anticipation, the court held, "does not require that a person of ordinary skill in the art at the time would have recognized the inherent disclosure." A hidden but inevitable property is no less anticipated for being hidden. The opinion acknowledged the apparent oddity of holding that a reference can disclose a compound nobody knew about, but reasoned that the alternative would let patentees claim, and effectively extend protection over, the unavoidable byproducts of compounds already in the public domain.

## The narrow path that survives: isolated and formulated claims

The decision is often read as a death sentence for metabolite patents, but the court was careful to leave a path open. The problem with Schering's claims was their breadth: they covered DCL in any form, including the DCL that simply appears in the bloodstream of a patient taking the old, now-public loratadine. Such claims read directly onto the inevitable consequence of the prior art.

A more careful drafter, the court suggested, could avoid that fate. The metabolite "may be claimed in its pure and isolated form" or "as a pharmaceutical composition," and a method of administering the metabolite directly might also be patentable. The '233 patent would not anticipate those narrower claims, because it never disclosed isolating DCL or formulating it as a drug; mere in-body formation does not enable a purified or compounded version. The lesson for innovators is that discovering a metabolite can still yield valuable, valid patents, but only if the claims are tethered to forms the prior art neither discloses nor enables.

## Open questions

- **Where is the line between inherent and merely possible?** *Schering* requires the feature to be necessary and inevitable, but later cases continue to debate how certain an outcome must be before it counts as inherent rather than probable.
- **How enabling must the prior art be?** The opinion distinguishes the bare formation of DCL from an enabling disclosure of isolated DCL, yet the enablement boundary for inherent anticipation remains fact-specific.
- **What about new and useful uses?** The court left room for method and formulation claims, but how far a metabolite discovery can reach into treatment methods is still litigated.

## Implications

- **Recognition is irrelevant.** A prior-art reference can anticipate a feature no one knew about, so long as the feature is the inevitable result of practicing the reference.
- **Broad metabolite claims are perilous.** Claims that cover a metabolite in any form, including as it appears in the body after taking an old drug, are vulnerable to inherent anticipation.
- **Draft narrowly and concretely.** Claim the metabolite in pure and isolated form, as a formulation, or through a specific method to escape the prior art's inherent disclosure.
- **Prior-art screening must look downstream.** Patent owners and challengers alike should ask what compounds, byproducts, or properties an old reference inevitably produces, even if unstated.
- **Public-domain compounds carry their consequences.** Once a compound enters the public domain, the inevitable products of using it generally come with it.

## Frequently asked questions

**What is inherent anticipation?**
Inherent anticipation occurs when a prior-art reference does not expressly describe a feature but that feature is necessarily present, the natural and inevitable result of what the reference discloses. The hidden feature defeats novelty even if no one recognized it at the time.

**Why was Schering's metabolite patent anticipated by the earlier loratadine patent?**
Because taking loratadine, the drug covered by the earlier '233 patent, necessarily and inevitably produces the metabolite DCL in the human body. Since the earlier patent's disclosure inherently included the formation of DCL, it anticipated the later claims covering DCL itself.

**How can an inventor still patent a newly discovered metabolite?**
By claiming it in a form that the prior art does not inherently disclose, such as the metabolite in pure and isolated form or as a pharmaceutical composition. The court noted the earlier patent did not enable those narrower claims because it never disclosed isolating the metabolite.

## Authorities and sources

- Full opinion, *Schering Corp. v. Geneva Pharmaceuticals, Inc.*, 339 F.3d 1373 (Fed. Cir. 2003) (Justia): https://law.justia.com/cases/federal/appellate-courts/F3/339/1373/603414/
- CourtListener opinion page: https://www.courtlistener.com/opinion/783157/schering-corporation-v-geneva-pharmaceuticals-inc-and-novartis/
- 35 U.S.C. § 102 (novelty) (Cornell LII): https://www.law.cornell.edu/uscode/text/35/102
- Practitioner analysis, Ropes & Gray, "Schering v. Geneva: Drug Discovery Implications": https://www.ropesgray.com/en/insights/alerts/2003/09/schering-v-geneva-drug-discovery-implications