# Wyeth v. Abbott: One Species, Tens of Thousands of Claims, and Undue Experimentation

> A specification that disclosed a single rapamycin compound could not support claims reaching tens of thousands of structurally diverse molecules, the Federal Circuit held, because finding the active ones required excessive screening.

Topic: Patents  |  Author: Lidiia Levitska  |  Source: Intellectual Property Law (outsideipcounsel.com)
Canonical: https://outsideipcounsel.com/blog/wyeth-v-abbott-rapamycin-genus-undue-experimentation/


*Wyeth and Cordis Corp. v. Abbott Laboratories*, Nos. 2012-1223, -1224 (Fed. Cir. June 26, 2013), is a foundational modern application of the undue-experimentation doctrine to a functional genus claim. Writing for the panel, Judge Moore affirmed summary judgment that claims 1 and 2 of the '781 patent and claim 1 of the '146 patent were not enabled: the specification disclosed a single working compound, sirolimus, yet the claims reached every "rapamycin" with the desired biological effects (a class the court put at "at least tens of thousands" of candidates). Decided a decade before *Amgen v. Sanofi*, *Wyeth* anticipated the Supreme Court's reasoning and remains a clean, frequently cited template for how courts measure experimental burden against claim breadth.

## At a glance

- **Case:** *Wyeth and Cordis Corp. v. Abbott Laboratories*, Nos. 2012-1223, -1224
- **Court and date:** U.S. Court of Appeals for the Federal Circuit; decided June 26, 2013 (precedential)
- **Panel:** Judges Moore (author), Bryson, and Wallach
- **Patents:** U.S. Patent Nos. 5,516,781 and 5,563,146
- **Holding:** The asserted claims are invalid for lack of enablement under 35 U.S.C. § 112; the experimentation required to practice the full claim scope was undue
- **Status:** Final

## The invention and the claims

Wyeth's patents described a discovery of real therapeutic importance: that rapamycin can treat or prevent restenosis (the renarrowing of an artery after a procedure such as angioplasty). The independent claims recited a method of treating or preventing restenosis by administering "an antirestenosis effective amount of rapamycin."

The decisive question was what "rapamycin" meant. The breadth was Wyeth's own doing: the accused stents eluted everolimus and zotarolimus, analogs that share sirolimus's macrocyclic ring but carry a different substituent at the C-42 position, so a narrow construction would not have reached them. The district court adopted *Wyeth's* proposed construction of "rapamycin" as "a compound containing a macrocyclic triene ring structure produced by Streptomyces hygroscopicus, having immunosuppressive and anti-restenotic effects." Wyeth did not challenge that construction on appeal, and the Federal Circuit called it unchallenged. Under it, the claims covered not one molecule but a functionally defined genus: any compound with the core ring and the desired biological effects. The specification, by contrast, disclosed only sirolimus. It described how to make and use that one species and said essentially nothing about which structural variations would preserve the activity.

## The enablement framework

Enablement under § 112(a) requires that the specification teach a skilled artisan to make and use the *full scope* of the claimed invention without undue experimentation. Whether experimentation is "undue" is conventionally assessed under the eight *In re Wands* factors: the quantity of experimentation needed, the amount of guidance presented, the presence or absence of working examples, the nature of the invention, the state of the prior art, the relative skill of those in the art, the predictability of the art, and the breadth of the claims.

Worth noting, because *Wyeth* is often described as a *Wands* case: the panel never cited *Wands* by name and did not walk the factors one by one. It framed undue experimentation as "a matter of degree," reasoning instead from *Chiron*, *Johns Hopkins*, *Cephalon*, *ALZA Corp. v. Andrx Pharmaceuticals*, and *In re Vaeck*. The analysis nonetheless tracks the same considerations, and two dominated: the extraordinary breadth of the claims (a genus of at least tens of thousands of candidates) and the unpredictability of the relationship between a rapamycin analog's structure and its biological activity.

## Why the experimentation was "undue"

The scale of the problem survived even on Wyeth's own version of the facts. Because this came up on summary judgment, the panel accepted Wyeth's assertions as true, including its expert's view that a workable rapamycin candidate would have to be permeable across cell membranes and so weigh under about 1,200 Daltons. Wyeth's own expert had acknowledged that varying the substituents outside the macrocyclic ring could yield millions of compounds; even after the molecular-weight filter, at least tens of thousands of candidates remained. To know which of them actually possessed the claimed immunosuppressive and antirestenotic effects, a researcher would have to *make* each candidate and then *assay* it. Wyeth's own expert conceded that running the relevant assays would take a skilled technician weeks per compound.

Crucially, the specification offered no shortcut. It gave no guidance about which substitutions on the macrocyclic ring would tend to preserve activity and which would destroy it, and no predictive principle that would let a researcher narrow the field before synthesizing and testing. The art was unpredictable, so a skilled artisan could not reason from sirolimus to the rest of the genus; each member had to be confirmed empirically.

The court drew a careful distinction that has become a fixture of enablement law. The mere existence of *routine* screening assays does not save a claim. Even if each individual experiment is conventional, the *aggregate* burden can be undue when the number of compounds to be made and tested is vast and the specification supplies no way to predict which will work. Synthesizing and screening tens of thousands of candidates, with weeks of assay work apiece and no predictive guidance, was the paradigm of excessive experimentation. The claims were therefore not enabled.

## A precursor to Amgen

*Wyeth* reads, in retrospect, like a chemical-arts rehearsal for *Amgen v. Sanofi*. Both cases involve a functional genus (antibodies defined by what they bind in *Amgen*, rapamycin compounds defined by their effects here), and both fail because the specification offered a method of trial-and-error discovery rather than a teaching of the full claimed class. The Supreme Court's phrase in *Amgen*, that "[t]he more one claims, the more one must enable," is simply a compact statement of what the *Wyeth* panel had already done. For practitioners, *Wyeth* remains valuable precisely because its facts are so concrete: a single disclosed species, a clearly quantified genus, and an expert's own admission about how long the screening would take.

## Open questions

*Wyeth* does not tell us how much structural guidance would have been enough to carry the genus, nor how predictable the structure-activity relationship must be before a representative disclosure suffices. It also leaves open the role of claim construction as a release valve: had "rapamycin" been construed to mean only sirolimus, the enablement problem would have largely evaporated, which is a reminder that the breadth a patentee fights for in construction is the breadth its disclosure must then support. And while the district court had also held the claims invalid for lack of written description, the panel expressly declined to reach that ground once nonenablement disposed of the appeal, so the Federal Circuit's own view of the written-description question remains unstated.

## Implications

- **Quantify before you claim broadly.** If a functional genus encompasses tens of thousands of compounds and activity must be confirmed one at a time, the claim is exposed to an undue-experimentation defense.
- **Routine does not mean sufficient.** Disclosing a standard assay protocol does not enable a genus when the number of candidates is enormous; courts weigh the total experimental burden, not the difficulty of any single test.
- **Sell structure-activity guidance, not just a species.** Teaching which substitutions preserve the desired activity is what converts a single working example into support for a class.
- **Construction is destiny.** The broader the meaning a patentee secures for a genus term, the heavier the disclosure burden it assumes; narrow, well-supported claims survive.

## Frequently asked questions

**What did the claims cover that the specification did not teach?** The claims covered a genus of rapamycin compounds (on the order of tens of thousands) sharing a macrocyclic triene ring and the claimed biological activity. The specification disclosed and taught only one of them, sirolimus, with no guidance on which other compounds would work.

**If the assays were routine, why was the experimentation "undue"?** Because undueness turns on the total burden. Even routine assays become excessive when a researcher must synthesize and test tens of thousands of compounds (weeks per assay) with no way to predict in advance which will have the desired effect.

**How is Wyeth still relevant after Amgen v. Sanofi?** *Wyeth* (2013) invalidated a functional genus for lack of full-scope enablement on the same logic the Supreme Court later embraced in *Amgen* (2023). It offers a concrete, citable example of undue-experimentation analysis in the small-molecule and chemical context.

## Authorities and sources

- *Wyeth and Cordis Corp. v. Abbott Laboratories*, 720 F.3d 1380, Nos. 2012-1223, -1224 (Fed. Cir. June 26, 2013). Slip opinion (Moore, J., joined by Bryson and Wallach) via [govinfo](https://www.govinfo.gov/content/pkg/USCOURTS-ca13-12-01223/pdf/USCOURTS-ca13-12-01223-0.pdf); case record at [govinfo](https://www.govinfo.gov/app/details/USCOURTS-ca13-12-01223). Source of the "rapamycin" construction, the "at least tens of thousands" figure, the expert's weeks-per-assay concession, and the nonenablement holding.
- *Amgen Inc. v. Sanofi*, 598 U.S. 594 (2023). Quotation verified against the [slip opinion](https://www.supremecourt.gov/opinions/22pdf/21-757_k5g1.pdf).
- 35 U.S.C. § 112, via [Cornell LII](https://www.law.cornell.edu/uscode/text/35/112).
- *In re Wands*, 858 F.2d 731 (Fed. Cir. 1988), the source of the eight-factor framework the *Wyeth* panel did not expressly invoke.