United States Court of Appeals 

for the Federal Circuit ______________________

AMGEN INC., AMGEN MANUFACTURING, 

LIMITED, AMGEN USA, INC.,

Plaintiffs-Appellants

v.

SANOFI, AVENTISUB LLC, FKA AVENTIS 

PHARMACEUTICALS INC., REGENERON 

PHARMACEUTICALS INC., SANOFI-AVENTIS U.S. 

LLC,

Defendants-Appellees

______________________

2020-1074

______________________

Appeal from the United States District Court for the 

District of Delaware in Nos. 1:14-cv-01317-RGA, 1:14-cv01349-RGA, 1:14-cv-01393-RGA, 1:14-cv-01414-RGA, 

Judge Richard G. Andrews.

______________________

Decided: February 11, 2021

______________________

JEFFREY A. LAMKEN, MoloLamken LLP, Washington, 

DC, argued for plaintiffs-appellants. Also represented by 

SARAH JUSTINE NEWMAN, MICHAEL GREGORY PATTILLO, JR.; 

SARA MARGOLIS, New York, NY; ERICA S. OLSON, Amgen 

Inc., Santa Monica, CA; EMILY JOHNSON, STEVEN TANG,

STUART WATT, WENDY A. WHITEFORD, Thousand Oaks, CA; 

KEITH HUMMEL, Cravath Swaine & Moore LLP, New York, 

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2 AMGEN INC. v. SANOFI

NY; WILLIAM G. GAEDE, III, McDermott, Will & Emery 

LLP, Menlo Park, CA; CHRISTOPHER B. MEAD, Schertler 

Onorato & Mead LLP, Washington, DC; JAMES L. HIGGINS, 

MELANIE K. SHARP, Young, Conaway, Stargatt & Taylor 

LLP, Wilmington, DE. Plaintiff-appellant Amgen Inc. also 

represented by SARAH CHAPIN COLUMBIA, McDermott, Will 

& Emery LLP, Boston, MA; LAUREN MARTIN, Quinn Emanuel Urquhart & Sullivan LLP, Boston, MA.

 MATTHEW WOLF, Arnold & Porter Kaye Scholer LLP, 

Washington, DC, argued for defendants-appellees. Also 

represented by VICTORIA REINES; DAVID K. BARR, DANIEL 

REISNER, New York, NY; DEBORAH E. FISHMAN, Palo Alto, 

CA; GEORGE W. HICKS, JR., NATHAN S. MAMMEN, CALVIN 

ALEXANDER SHANK, Kirkland & Ellis LLP, Washington, 

DC. Defendants-appellees Sanofi, Aventisub LLC, SanofiAventis U.S. LLC also represented by STEPHANIE 

DONAHUE, Sanofi, Bridgewater, NJ. Defendant-appellee 

Regeneron Pharmaceuticals Inc. also represented by 

LARRY A. COURY, LYNDA NGUYEN, Regeneron Pharmaceuticals Inc., Tarrytown, NY.

 JORGE A. GOLDSTEIN, Sterne Kessler Goldstein & Fox, 

PLLC, Washington, DC, for amici curiae Bristol-Myers 

Squibb Company, Merck Sharp & Dohme Corp. Also represented by KRISTINA CAGGIANO KELLY, ELDORA ELLISON,

WILLIAM MILLIKEN.

 DUANE CHRISTOPHER MARKS, Eli Lilly and Company, 

Indianapolis, IN, for amicus curiae Eli Lilly and Company. 

Also represented by TONYA COMBS, MARK STEWART,

GILBERT VOY.

 AMIT THAKORE, White & Case LLP, New York, NY, for 

amicus curiae Pfizer Inc. Also represented by DIMITRIOS T.

DRIVAS; ELIZABETH K. CHANG, Palo Alto, CA; JEFFREY NEIL 

MYERS, Pfizer Inc., New York, NY.

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AMGEN INC. v. SANOFI 3

 STANLEY D. LIANG, Tarrytown, NY, as amicus curiae, 

pro se.

 ______________________

Before PROST, Chief Judge, LOURIE and HUGHES, Circuit 

Judges.

LOURIE, Circuit Judge.

Amgen Inc., Amgen Manufacturing, Ltd., and Amgen 

USA, Inc. (collectively, “Amgen”) appeal from a decision of 

the United States District Court for the District of Delaware granting Judgment as a Matter of Law (“JMOL”) of

lack of enablement of claims 19 and 29 of U.S. Patent 

8,829,165 (the “’165 patent”) and claim 7 of U.S. Patent

8,859,741 (the “’741 patent”). See Amgen Inc. v. Sanofi, 

No. CV 14-1317-RGA, 2019 WL 4058927, at *1–2, *13 (D. 

Del. Aug. 28, 2019) (“Decision”). For the reasons set forth 

below, we affirm.

BACKGROUND

Elevated low-density lipoprotein (“LDL”) cholesterol is 

linked to heart disease. LDL receptors remove LDL cholesterol from the blood stream, thus regulating the amount 

of circulating LDL cholesterol. The proprotein convertase 

subtilisin/kexin type 9 (“PCSK9”) enzyme regulates LDL 

receptor degradation. PCSK9 binds to LDL receptors and

mediates their degradation, thus decreasing the number of 

LDL receptors on a cell’s surface. Antibodies may bind to 

and block PCSK9, allowing LDL receptors to continue regulating the amount of circulating LDL cholesterol.

Amgen owns the ’165 and ’741 patents, which describe 

antibodies that purportedly bind to the PCSK9 protein and 

lower LDL levels by blocking PCSK9 from binding to LDL 

receptors. The ’165 and ’741 patents share a common written description. See Appellants’ Br. 10 n.2. The specification discloses amino acid sequences for twenty-six

antibodies, including the antibody (designated as “21B12”)

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4 AMGEN INC. v. SANOFI

with the generic name of evolocumab, marketed by Amgen

as Repatha®. See ’165 patent col. 85 ll. 1–43; Appellants’ 

Br. 11 n.3. As shown for example in Figure 20A of the ’165 

patent, the specification discloses three-dimensional structures for the antibodies designated 21B12 and 31H4 and

shows where those antibodies bind to PCSK9. The ’165 and 

’741 patents claim antibodies that bind to one or more of 

fifteen amino acids (i.e., “residues”) of the PCSK9 protein 

and block PCSK9 from binding to LDL receptors.

The relevant ’165 patent claims are:

1. An isolated monoclonal antibody, wherein, when 

bound to PCSK9, the monoclonal antibody binds to 

at least one of the following residues: S153, I154, 

P155, R194, D238, A239, I369, S372, D374, C375, 

T377, C378, F379, V380, or S381 of SEQ ID NO:3, 

and wherein the monoclonal antibody blocks binding of PCSK9 to LDLR.

19. The isolated monoclonal antibody of claim 1 

wherein the isolated monoclonal antibody binds to 

at least two of the following residues S153, I154, 

P155, R194, D238, A239, I369, S372, D374, C375, 

T377, C378, F379, V380, or S381 of PCSK9 listed 

in SEQ ID NO:3.

29. A pharmaceutical composition comprising an 

isolated monoclonal antibody, wherein the isolated 

monoclonal antibody binds to at least two of the following residues S153, I154, P155, R194, D238, 

A239, I369, S372, D374, C375, T377, C378, F379, 

V380, or S381 of PCSK9 listed in SEQ ID NO: 3 

and blocks the binding of PCSK9 to LDLR by at 

least 80%.

’165 patent col. 427 l. 47–col. 430 l. 23.

The relevant ’741 patent claims are:

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AMGEN INC. v. SANOFI 5

1. An isolated monoclonal antibody that binds to 

PCSK9, wherein the isolated monoclonal antibody 

binds an epitope on PCSK9 comprising at least one 

of residues 237 or 238 of SEQ ID NO: 3, and 

wherein the monoclonal antibody blocks binding of 

PCSK9 to LDLR.

2. The isolated monoclonal antibody of claim 1, 

wherein the isolated monoclonal antibody is a neutralizing antibody.

7. The isolated monoclonal antibody of claim 2, 

wherein the epitope is a functional epitope.

’741 patent col. 427 ll. 36–57. The claimed antibodies are 

defined by their function: binding to a combinations of sites 

(residues) on the PCSK9 protein, in a range from one residue to all of them; and blocking the PCSK9/LDLR interaction.

This is the second time that these patents have been on 

appeal in our court. Amgen filed suit against Sanofi, 

Aventisub LLC, Regeneron Pharmaceuticals Inc., and 

Sanofi-Aventis U.S. LLC (collectively, “Sanofi”) on October 17, 2014, alleging infringement of multiple U.S. patents, including the ’165 and ’741 patents. Decision at *1. 

Amgen and Sanofi stipulated to infringement of selected 

claims (including ’165 patent claims 19 and 29 and ’741 patent claim 7) and tried issues of validity to a jury in March 

2016. Id. During the trial, the district court granted JMOL 

of nonobviousness and of no willful infringement. Id. At 

the close of the trial, the jury determined that the patents 

were not shown to be invalid for lack of enablement and 

written description. Id.

Sanofi appealed to this court. Relevant to the current 

appeal, we held that the district court erred in its evidentiary rulings and jury instructions regarding Sanofi’s defenses that the patents lack written description and 

enablement, and we remanded for a new trial on those 

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6 AMGEN INC. v. SANOFI

issues. Amgen Inc. v. Sanofi, 872 F.3d 1367, 1381–82 

(Fed. Cir. 2017). We also vacated the permanent injunction. Id.

On remand, the parties tried the issues of written description and enablement to the jury. The jury again found

that Sanofi failed to prove that the asserted claims were 

invalid for lack of written description and enablement. 

Sanofi moved for JMOL and, in the alternative, for a new 

trial. Decision at *1; J.A. 895. The district court granted 

Sanofi’s Motion for JMOL for lack of enablement and denied the motion for lack of written description. See Decision at *17; J.A. 35. The court also conditionally denied 

Sanofi’s motion for a new trial. Id. Amgen timely appealed, and we have jurisdiction pursuant to 28 U.S.C. 

§ 1295(a)(1). See J.A. 909–10.

DISCUSSION

Whether a claim satisfies the enablement requirement 

of 35 U.S.C. § 112 is a question of law that we review without deference, although the determination may be based on 

underlying factual findings, which we review for clear error. See Alcon Research Ltd. v. Barr Labs., Inc., 745 F.3d 

1180, 1188 (Fed. Cir. 2014). The statutory basis for the enablement requirement is found in Section 112 of the patent 

statute, which provides in relevant part that a patent’s 

specification must “enable any person skilled in the art . . . 

to make and use” the patented invention. 35 U.S.C. 

§ 112(a). The purpose of the enablement requirement is to 

ensure that the public is told how to carry out the invention, i.e., to make and use it. We have held that such disclosure must be “at least commensurate with the scope of

the claims.” Crown Operations Int’l v. Solutia Inc., 289 

F.3d at 1367, 1378–79 (Fed. Cir. 2002) (citing Nat’l Recovery Techs., Inc. v. Magnetic Separation Sys., 166 F.3d 1190, 

1196 (Fed. Cir. 1999)).

“To prove that a claim is invalid for lack of enablement, 

a challenger must show by clear and convincing evidence 

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AMGEN INC. v. SANOFI 7

that a person of ordinary skill in the art would not be able 

to practice the claimed invention without ‘undue experimentation.’” Alcon Research, 745 F.3d at 1188 (quoting In 

re Wands, 858 F.2d 731, 736–37 (Fed. Cir. 1988)). 

“Whether undue experimentation is needed is not a single, 

simple factual determination, but rather is a conclusion 

reached by weighing many factual considerations.” Wands, 

858 F.2d at 737. Those factual considerations, which have 

come to be known as the “Wands factors,” are:

(1) the quantity of experimentation necessary, 

(2) the amount of direction or guidance presented, 

(3) the presence or absence of working examples, 

(4) the nature of the invention, (5) the state of the 

prior art, (6) the relative skill of those in the art, 

(7) the predictability or unpredictability of the art, 

and (8) the breadth of the claims.

Id.

As we have stated elsewhere, “[a]fter the challenger 

has put forward evidence that some experimentation is 

needed to practice the patented claim, the factors set forth 

in Wands then provide the factual considerations that a 

court may consider when determining whether the amount 

of that experimentation is either ‘undue’ or sufficiently routine such that an ordinarily skilled artisan would reasonably be expected to carry it out.” Alcon Research, 745 F.3d 

at 1188 (quoting Wands, 858 F.2d at 737). Although a specification does not need to “describe how to make and use 

every possible variant of the claimed invention, when a 

range is claimed, there must be reasonable enablement of 

the scope of the range.” McRO, Inc. v. Bandai Namco 

Games Am. Inc., 959 F.3d 1091, 1100 (Fed. Cir. 2020) (citing AK Steel Corp. v. Sollac, 344 F.3d 1234, 1244 (Fed. Cir. 

2003)) (internal citations omitted).

On appeal, Amgen asks us to reverse the district court’s 

decision holding ’165 patent claims 19 and 29 and ’741 patent claim 7 invalid for lack of enablement. Amgen 

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8 AMGEN INC. v. SANOFI

contends that, under a proper analysis of the Wands factors, the claims at issue were enabled because no undue 

experimentation is required to obtain antibodies fully 

within the scope of the claims. Amgen points to expert testimony purportedly showing that a person of skill in the art 

can make all antibodies within the scope of the claims by 

following a roadmap using anchor antibodies and wellknown screening techniques as described in the specification or by making conservative amino acid substitutions in 

the twenty-six examples. Amgen argues that the court 

erred by focusing on the effort required to discover and 

make every embodiment of the claims, see Appellants’ Br. 

32 (citing Decision at *7), while failing to recognize that 

Sanofi could not identify any antibody that cannot be made 

by following the specification’s teachings. See Reply Br. 4–

5; see also McRO, 959 F.3d at 1104 (“[A] usual requirement 

[is] that the challenger identify specifics that are or may be 

within the claim but are not enabled.”). Amgen contends 

that the embodiments in the patent are structurally representative for the purpose of fulfilling the written description requirement, and such evidence is sufficient to 

indicate a structure/function correlation establishing enablement. See Reply Br. 23–24.

Sanofi responds that the district court properly concluded based on the Wands factors that the claims are not 

enabled because they require undue experimentation. As 

support for its position, Sanofi contends that there are millions of antibody candidates within the scope of the claims, 

the disclosures do not provide sufficient guidance, antibody 

generation is unpredictable, and practicing the full scope of 

the claims requires substantial trial and error. See Appellees’ Br. 17–18, 56. According to Sanofi, the functionally 

defined claims cover a vast scope. See id. at 34–41. Sanofi 

argues that Amgen focused on “the number of antibodies 

actually known to satisfy the claims, when this court’s 

precedents require examining the number of candidates

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AMGEN INC. v. SANOFI 9

that must be made and tested to determine whether they 

satisfy the claimed function.” Id. at 18.

We begin by considering the Wands case itself, which 

has become the “go to” precedent for guidance on enablement, and which also involved claims relating to antibody 

technology. The broadest claim in Wands “involve[d] immunoassay methods for the detection of hepatitis B surface 

antigen by using high-affinity monoclonal antibodies of the 

IgM isotype.” Wands, 858 F.2d at 733. The U.S. Patent 

and Trademark Office Board of Patent Appeals and Interferences had found that undue experimentation would be 

required for one skilled in the art to make the claimed antibodies used in the methods because “production of highaffinity IgM anti-HBsAg antibodies [was] unpredictable 

and unreliable.” Id. at 735. We found, reviewing the facts, 

that the disclosure adequately taught using hybridoma 

technology to produce the needed claimed antibodies. See 

id. at 734. We stated that “no evidence was presented by 

either party on how many hybridomas would be viewed by 

those in the art as requiring undue experimentation to 

screen,” id. at 740, and we accordingly held that the specification fully enabled the claimed invention, see id. at 736.

Importantly, although Wands gave birth to its eponymous factors, Wands did not proclaim that all broad claims 

to antibodies are necessarily enabled. Facts control and, in 

this court, so does the standard of review. In considering 

the Wands factors, the district court compared the present

case to other cases in which we found lack of enablement 

due to the undue experimentation required to make and 

use the full scope of the claimed compounds that require a 

particular structure and functionality. For example, in Wyeth & Cordis Corp. v. Abbott Laboratories, we held that 

claims covering methods of preventing restenosis with 

compounds having certain functionality requirements 

were invalid for lack of enablement. See 720 F.3d 1380, 

1385–86 (Fed. Cir. 2013). Of particular significance, we 

held that due to the large number of possible candidates 

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10 AMGEN INC. v. SANOFI

within the scope of the claims and the specification’s corresponding lack of structural guidance, it would have required undue experimentation to synthesize and screen 

each candidate to determine which compounds in the 

claimed class exhibited the claimed functionality. Id.

Similarly, in Enzo Life Sciences, Inc. v. Roche Molecular Systems, Inc., we found that the claims were similar to 

those at issue in Wyeth in that they required both a particular structure and functionality, and we held that the specification failed to teach one of skill in the art whether the 

many embodiments of the broad claims would exhibit that 

required functionality. See 928 F.3d 1340, 1345–48 (Fed. 

Cir. 2019). And, in Idenix Pharmaceuticals LLC v. Gilead 

Sciences Inc., we affirmed the district court’s determination that the claims had both structural and functional limitations, and that undue experimentation would have been 

required to synthesize and screen the billions of possible 

compounds because, given a lack of guidance across that 

full scope, finding functional compounds would be akin to 

finding a “needle in a haystack.” 941 F.3d 1149, 1160–63, 

1165 (Fed. Cir. 2019); see Idenix Pharms. LLC v. Gilead 

Scis., Inc., 2018 WL 922125 (D. Del. Feb. 16, 2018). The 

district court found that Wyeth, Enzo, and Idenix all support its conclusion that the asserted claims lack enablement. See Decision at *9–13.

What emerges from our case law is that the enablement inquiry for claims that include functional requirements can be particularly focused on the breadth of those 

requirements, especially where predictability and guidance fall short. In particular, it is important to consider 

the quantity of experimentation that would be required to

make and use, not only the limited number of embodiments 

that the patent discloses, but also the full scope of the 

claim. As we recently explained:

[C]onducting the Wands analysis has routinely involved concrete identification of at least some 

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AMGEN INC. v. SANOFI 11

embodiment or embodiments asserted not to be enabled—including what particular products or processes are or may be within the claim, so that 

breadth is shown concretely and not just as an abstract possibility, and how much experimentation 

a skilled artisan would have to undertake to make 

and use those products or processes.

McRO, 959 F.3d at 1100. We then elaborated in a footnote 

that: 

In cases involving claims that state certain structural requirements and also require performance of 

some function (e.g., efficacy for a certain purpose), 

we have explained that undue experimentation can 

include undue experimentation in identifying, from 

among the many concretely identified compounds 

that meet the structural requirements, the compounds that satisfy the functional requirement.

Id. at 1100 n.2 (citations omitted).

That reasoning applies here. While functional claim 

limitations are not necessarily precluded in claims that 

meet the enablement requirement, such limitations pose 

high hurdles in fulfilling the enablement requirement for

claims with broad functional language. See, e.g., Wyeth, 

720 F.3d at 1384 (finding that practicing the full scope of 

the claims would require excessive experimentation); Enzo, 

928 F.3d at 1345 (finding that the specification failed to 

teach whether the many embodiments would be both hybridizable and detectable upon hybridization); Idenix, 941 

F.3d at 1155–56 (finding that the broad functional limitation of having efficacy against hepatitis C virus increased 

the number of nucleoside candidates that would need to be 

screened).

Each appealed claim in this case is a composition claim 

defined, not by structure, but by meeting functional limitations. We agree with the district court’s finding that the 

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12 AMGEN INC. v. SANOFI

specification here did not enable preparation of the full 

scope of these double-function claims without undue experimentation. See Decision at *13. The binding limitation is 

itself enough here to require undue experimentation.

Turning to the specific Wands factors, we agree with 

the district court that the scope of the claims is broad. 

While in and of itself this does not close the analysis, the 

district court properly considered that these claims were 

indisputably broad. The parties dispute the exact number 

of embodiments falling within the claims. However, we are 

not concerned simply with the number of embodiments but 

also with their functional breadth. Regardless of the exact 

number of embodiments, it is clear that the claims are far 

broader in functional diversity than the disclosed examples.1 If the genus is analogized to a plot of land, the disclosed species and guidance “only abide in a corner of the 

genus.” AbbVie Deutschland GmbH & Co. v. Janssen Biotech, Inc., 759 F.3d 1285, 1299–300 (Fed. Cir. 2014). Further, the use of broad functional claim limitations raises 

the bar for enablement, a bar that the district court found 

was not met.

We also agree with the district court that this invention 

is in an unpredictable field of science with respect to satisfying the full scope of the functional limitations. One of 

Amgen’s expert witnesses admitted that translating an antibody’s amino acid “sequence into a known three-dimensional structure is still not possible.” J.A. 3910; see also 

Decision at *9. Another of Amgen’s experts conceded that 

“substitutions in the amino acid sequence of an antibody 

can affect the antibody’s function, and testing would be 

1 For example, there are three claimed residues to 

which not one disclosed example binds. See J.A. 4283; Appellees’ Br. 52. And although the claims include antibodies 

that bind up to sixteen residues, none of Amgen’s examples 

binds more than nine. See id.

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AMGEN INC. v. SANOFI 13

required to ensure that a substitution does not alter the 

binding and blocking functions.” J.A. 3891; see also Decision at *9. And while some need for testing by itself might 

not indicate a lack of enablement, we note here the conspicuous absence of nonconclusory evidence that the full scope 

of the broad claims can predictably be generated by the described methods. Instead, we have evidence only that a 

small subset of examples of antibodies can predictably be 

generated.

Although the specification provides some guidance, including data regarding certain embodiments, we agree 

with the district court that “[a]fter considering the disclosed roadmap in light of the unpredictability of the art, 

any reasonable factfinder would conclude that the patent 

does not provide significant guidance or direction to a person of ordinary skill in the art for the full scope of the 

claims.” Decision at *11. Here, even assuming that the 

patent’s “roadmap” provided guidance for making antibodies with binding properties similar to those of the working 

examples, no reasonable factfinder could conclude that 

there was adequate guidance beyond the narrow scope of 

the working examples that the patent’s “roadmap” produced.

As the district court noted, the only ways for a person 

of ordinary skill to discover undisclosed claimed embodiments would be through either “trial and error, by making 

changes to the disclosed antibodies and then screening 

those antibodies for the desired binding and blocking properties,” or else “by discovering the antibodies de novo” according to a randomization-and-screening “roadmap.” Id. 

Either way, we agree with the district court that the required experimentation “would take a substantial amount 

of time and effort.” Id. at *12. We do not hold that the 

effort required to exhaust a genus is dispositive. It is appropriate, however, to look at the amount of effort needed 

to obtain embodiments outside the scope of the disclosed 

examples and guidance. The functional limitations here 

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14 AMGEN INC. v. SANOFI

are broad, the disclosed examples and guidance are narrow, and no reasonable jury could conclude under these 

facts that anything but “substantial time and effort” would 

be required to reach the full scope of claimed embodiments.

We therefore conclude that, after weighing the Wands

factors, the court did not err in concluding that undue experimentation would be required to practice the full scope 

of these claims.

Finally, Amgen is incorrect that the district court’s decision is inconsistent with Wands or that our affirmance 

here would overrule Wands. Wands, as indicated above,

does not hold that antibody screening never requires undue 

experimentation. The holding in Wands was based on the 

facts of that case and the evidence presented there. Here, 

the evidence showed that the scope of the claims encompasses millions of candidates claimed with respect to multiple specific functions, and that it would be necessary to 

first generate and then screen each candidate antibody to 

determine whether it meets the double-function claim limitations. See Decision at *7–13. The facts of this case are 

thus more analogous to those in Enzo, Wyeth, and Idenix, 

where we concluded a lack of enablement.

CONCLUSION

We have considered Amgen’s remaining arguments but 

find them unpersuasive. For the reasons above, we affirm

the district court’s determination that the asserted claims 

are invalid for lack of enablement.

AFFIRMED

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