Document ID: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-ca13-23-02220/USCOURTS-ca13-23-02220-0/pdf.json

Parties Involved:
Alembic Pharmaceuticals Inc.
Not party
Alembic Pharmaceuticals Limited
Not party
Novartis Pharmaceuticals Corporation
Appellant

Document Text:

United States Court of Appeals 

for the Federal Circuit

______________________

IN RE: ENTRESTO (SACUBITRIL/VALSARTAN)

--------------------------------------------------

NOVARTIS PHARMACEUTICALS CORPORATION,

Plaintiff-Appellant

v.

TORRENT PHARMA INC., TORRENT 

PHARMACEUTICALS LTD.

Defendants

--------------------------------------------------

NOVARTIS PHARMACEUTICALS CORPORATION,

Plaintiff-Appellant

v.

ALEMBIC PHARMACEUTICALS LIMITED, 

ALEMBIC PHARMACEUTICALS INC.,

Defendants

--------------------------------------------------

NOVARTIS PHARMACEUTICALS CORPORATION,

Plaintiff-Appellant

v.

MSN PHARMACEUTICALS, INC., MSN 

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LABORATORIES PRIVATE LTD., MSN LIFE 

SCIENCES PRIVATE LTD.,

Defendants-Appellees

HETERO USA, INC., HETERO LABS LIMITED, 

HETERO LABS LIMITED UNIT-III,

Defendants

______________________

2023-2218, 2023-2220, 2023-2221

______________________

Appeals from the United States District Court for the 

District of Delaware in Nos. 1:19-cv-01979-RGA, 1:19-cv02021-RGA, 1:19-cv-02053-RGA, 1:19-cv-02053-RGA, 1:20-

md-02930-RGA, Judge Richard G. Andrews.

______________________

Decided: January 10, 2025

______________________

DEANNE MAYNARD, Morrison & Foerster LLP, 

Washington, DC, argued for plaintiff-appellant. Also 

represented by SETH W. LLOYD; NICHOLAS NICK KALLAS,

CHRISTINA A. L. SCHWARZ, Venable LLP, New York, NY. 

 WILLIAM A. RAKOCZY, Rakoczy Molino Mazzochi Siwik 

LLP, Chicago, IL, argued for defendants-appellees. Also 

represented by KEVIN E. WARNER; RONALD M. DAIGNAULT,

RICHARD JUANG, Daignault Iyer LLP, Vienna, VA. 

 ______________________

Before LOURIE, PROST, and REYNA, Circuit Judges.

LOURIE, Circuit Judge.

Following a three-day bench trial, the United States 

District Court for the District of Delaware determined that 

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claims 1–4 of U.S. Patent 8,101,659 (“the ’659 patent”) were 

not shown to be invalid for obviousness, lack of 

enablement, or indefiniteness, but were shown to be 

invalid for lack of written description. In re Entresto 

(Sacubitril/Valsartan) Pat. Litig., No. 20-md-2930, 

2023 WL 4405464, at *13, *21, *22 (D. Del. July 7, 2023) 

(“Decision”). Judgment was entered on those grounds. 

Appellant Novartis Pharmaceuticals Corporation 

(“Novartis”) challenges the district court’s written 

description determination. Appellees MSN

Pharmaceuticals, Inc., MSN Laboratories Private Ltd., and

MSN Life Sciences Private Ltd. (collectively, “MSN”)1

argue that the judgment of invalidity should be affirmed, 

either by affirming the district court’s written description 

determination or, alternatively, by reversing the district 

court’s obviousness or enablement determinations.

For the following reasons, we reverse the district 

court’s determination that the claims lack an adequate 

written description, and we affirm its determinations that 

the claims were not shown to be invalid as either nonenabled or obvious.

1 Of the presently named defendants, only MSN 

participates in this appeal. Each of Hetero USA Inc., 

Hetero Labs Limited, Hetero Labs Limited Unit-III 

(collectively, “Hetero”), Torrent Pharma Inc., Torrent 

Pharmaceuticals Ltd. (collectively, “Torrent”) have since 

settled their disputes with Novartis. See ECF Nos. 57, 58, 

61, 78. Moreover, Novartis indicated that it noted an 

appeal in its case against Alembic Pharmaceuticals, Ltd. 

and Alembic Pharmaceuticals, Inc. (collectively, “Alembic”) 

only “[o]ut of an abundance of caution.” ECF No. 15 at 2 

n.1. But because the case against Alembic is stayed and 

because Alembic did not participate in the trial on the 

merits, “Alembic is not an appellee here.” Id.

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BACKGROUND

I

In 2015, the U.S. Food and Drug Administration 

(“FDA”) approved the New Drug Application (“NDA”) for a 

combination therapy of valsartan and sacubitril, which 

Novartis markets and sells under the brand name 

Entresto®. Entresto includes valsartan and sacubitril in a 

specific form known as a “complex,” which combines the 

two drugs into a single unit-dose-form through weak, noncovalent bonds. Valsartan is an angiotensin receptor 

blocker (“ARB”) that prevents angiotensin II from binding 

to its receptor, thereby reducing the blood-vesselconstricting effects of angiotensin II, a naturally occurring 

hormone. Sacubitril is a neutral endopeptidase (“NEP”) 

inhibitor that, like valsartan, reduces blood vessel 

constriction, but does so through a mechanism-of-action 

not involving angiotensin. At the time of its initial 

approval, Entresto was indicated to treat heart failure with 

reduced ejection fraction. In 2019, Entresto was 

additionally approved for the treatment of heart failure in 

children, and, in 2021, it was approved for the treatment of 

heart failure with a preserved ejection fraction. In 2023

alone, sales of Entresto in the United States totaled more 

than $3 billion.

Entresto is protected by a number of patents, including 

the ’659 patent, which was timely listed in the Orange 

Book. The ’659 patent has a priority date of January 17, 

2002, and will expire on January 15, 2025, due to the grant

of Patent Term Extension (“PTE”). The ’659 patent 

explains that, at the time of the invention, “the most widely 

studied” drugs to treat hypertension and heart failure were 

a class of drugs called angiotensin converting enzyme 

(“ACE”) inhibitors. ’659 patent, col. 1 ll. 55–61. Like 

valsartan and other ARBs, ACE inhibitors’ function 

involves angiotensin. But instead of preventing 

angiotensin II from binding to its receptor, ACE inhibitors 

reduce vasoconstriction by blocking the initial formation of

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angiotensin II. See Decision, at *4. The ’659 patent 

explains that, although ACE inhibitors prevent the 

formation of vasoconstrictive angiotensin II, research 

showed that the effects of those drugs may be attributed to 

other pathways. ’659 patent, col. 2 ll. 6–9. The patent also

sets forth that, at the time of the invention, research 

showed that NEPs, like sacubitril, can lower blood pressure

and exert effects such as diuresis. Id. col. 2 ll. 39–41. 

Sacubitril had been discovered and patented by a 

predecessor to Novartis in 1992, but as of the time of the 

invention, it “had never been administered to humans or 

tested in an animal model of hypertension and heart 

failure.” Decision, at *7.

The patent explains that, because “the nature of 

hypertensive vascular diseases is 

multifactorial[,] . . . drugs with different mechanisms of 

action have been combined.” ’659 patent, col. 2 ll. 65–67. 

But “just considering any combination of drugs having 

different modes of action does not necessarily lead to 

combinations with advantageous effects.” Id. col. 2 l. 67–

col. 3 l. 3. Accordingly, the inventors of the ’659 patent 

sought to discover a “more efficacious combination therapy 

which has less deleterious side effects.” Id. col. 3 ll. 3–5. 

And as the specification explains, it was “surprisingly [] 

found that[] a combination of valsartan and a NEP 

inhibitor achieves greater therapeutic effect than the 

administration of valsartan, ACE inhibitors or NEP 

inhibitors alone.” Id. col. 6 ll. 41–44.

The ’659 patent has four claims, all of which are 

asserted here. Claim 1, the sole independent claim, recites:

1. A pharmaceutical composition comprising:

(i) the AT 1-antagonist valsartan or a 

pharmaceutically acceptable salt thereof;

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(ii) the NEP inhibitor [sacubitril] or 

[sacubitrilat]2 or a pharmaceutically acceptable 

salt thereof; and

(iii) a pharmaceutically acceptable carrier;

wherein said (i) AT 1-antagonist valsartan or 

pharmaceutically acceptable salt thereof and said 

(ii) NEP inhibitor [sacubitril] or [sacubitrilat] or a 

pharmaceutically acceptable salt thereof, are 

administered in combination in about a 1:1 ratio.

’659 patent, col. 16 ll. 17–33. Claim 2 recites that the 

valsartan and the NEP inhibitor “are administered in 

amounts effective to treat hypertension or heart failure,” 

id. col. 16 ll. 34–41; claim 3 recites that the NEP inhibitor 

is sacubitril, id. col. 16 ll. 42–45; and claim 4, which 

depends from claim 3, recites that the composition is in the 

form of a capsule or tablet, id. col. 16 ll. 46–47. On appeal, 

the validity of all of the claims rests on the same bases, so 

we will not treat them separately.

II

In 2019, MSN, among other generic manufacturers,

submitted an Abbreviated New Drug Application 

(“ANDA”) seeking FDA approval to market and sell a 

generic version of Entresto. Novartis sued MSN and the 

other generic manufacturers, alleging that the filing of the 

ANDA directly infringed claims 1–4 of the ’659 patent. 

2 Sacubitrilat is the active metabolite of the prodrug 

sacubitril, which means that, when sacubitril is ingested 

into the body, it is metabolized to sacubitrilat. Decision, 

at *1 n.3. The parties and district court used the term 

“sacubitril” to refer collectively to sacubitril, sacubitrilat, 

and their pharmaceutically acceptable salts. Id. Unless it 

is otherwise clear from context, we follow that convention 

here. 

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Those cases were consolidated in multidistrict litigation in 

Delaware and proceeded to discovery.

A. Claim Construction

At claim construction, the parties disputed only a 

single term of the ’659 patent: “wherein said [valsartan and 

sacubitril] are administered in combination.” See In re 

Entresto (Sacubitril/Valsartan) Pat. Litig., No. 20-md2930, 2021 WL 2856683, at *3 (D. Del. July 8, 2021)

(“Claim Construction Decision”) (emphasis added). MSN 

argued that the term limited the claim to administration of 

the active agents valsartan and sacubitril “as two separate 

components.” Id. As context for that position, according to 

MSN, the accused generic product, like Entresto, comprises 

a complex of non-covalently bonded valsartan and 

sacubitril. MSN Br. 1. Accordingly, if the claims were read 

to require the valsartan and sacubitril to be administered 

as separate components (i.e., in a non-complexed form, 

such as a physical mixture), then MSN’s generic product 

would not infringe the ’659 patent. For its part, Novartis 

argued that the claim was not so limited, and that the term 

should be given its plain and ordinary meaning. See Claim 

Construction Decision, at *3.

The district court agreed with Novartis and gave the 

term its plain and ordinary meaning: “wherein said 

[valsartan and sacubitril] are administered in 

combination.” Id. In rejecting MSN’s proposal, the court 

observed that the intrinsic record “is silent on whether 

sacubitril and valsartan must be separate (and not 

complexed).” Id. It explained that “the absence of any 

indication in the written description that the patentee 

limited its invention solely to separate compounds means, 

in context, that a person of ordinary skill in the art [] would 

not read the claims as so limited.” Id. The court found that 

the representations Novartis had made to the U.S. Patent 

and Trademark Office (“the Patent Office”) to obtain PTE

further bolstered that conclusion. Id. Specifically, 

Novartis told the Patent Office that the claims of the ’659 

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patent recite compositions that include Entresto, a drug 

that includes “non-separate, complexed valsartan and 

sacubitril.” Id.; see Novartis Br. 16. The court found that 

a person of ordinary skill in the art would have given that 

evidence at least some weight in understanding the 

meaning of the disputed term. Claim Construction 

Decision, at *3.

Based in part on those representations to the Patent

Office, MSN argued that Novartis’s position—that the 

plain and ordinary meaning of the claim scope 

encompasses valsartan-sacubitril complexes—would 

render the claims invalid for lack of written description and 

enablement because the specification nowhere describes 

such complexes. Id. at *4. The court rejected this 

argument, finding “no basis to believe that the construction 

[the court] adopt[ed was] necessarily consigning the 

asserted claims to a judgment of invalidity.” Id. After 

claim construction, MSN stipulated to infringement of the 

asserted claims. Decision, at *1.

B. Bench Trial

The case proceeded to a three-day bench trial on the 

issues of obviousness, lack of written description, and nonenablement.

3 Id.

1. Obviousness

At trial, MSN set forth two theories of obviousness. 

First, it argued that a person of ordinary skill in the art 

would have been motivated to modify a prior art ARB-NEP 

inhibitor combination therapy—specifically, one using the 

3 MSN also argued the claims were invalid as 

indefinite. Finding that MSN raised that argument only in 

a footnote of its opening post-trial brief, the district court 

deemed the argument forfeited. Id. at *22. Neither party 

addresses indefiniteness on appeal, so we too do not 

consider it.

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ARB irbesartan and an NEP inhibitor named

“SQ 28,603”—with valsartan and sacubitril to arrive at the 

claimed invention. Id. at *10. Alternatively, MSN argued 

that a person of ordinary skill in the art would have been 

motivated to individually select and combine sacubitril and 

valsartan from two different prior-art references to arrive 

at the claimed invention. Id. The court was unpersuaded 

by both theories.

Although the court found persuasive MSN’s argument 

that a person of ordinary skill in the art would have 

understood “that the combination of an ARB (irbesartan) 

and a NEP[ inhibitor] (SQ 28,603) achieved synergistic 

results,” the court ultimately concluded that, even if a 

person of ordinary skill in the art would have been 

motivated to pursue an ARB-NEP inhibitor combination, 

MSN “fail[ed] to provide clear and convincing evidence that 

a [person of ordinary skill in the art] would have been 

motivated to select the ARB valsartan and the 

NEP[ inhibitor] sacubitril specifically.” Id. Indeed, the 

court found that, as of 2002, sacubitril “had never been 

administered to humans or tested in an animal model of 

hypertension and heart failure,” and that, of the NEP 

inhibitors that had been so tested, the results had been 

“discouraging.” Id.

In rejecting MSN’s challenges, the court further noted 

that none of the prior art “combined valsartan with 

sacubitril, sacubitril with an ARB, or valsartan with a[n] 

NEP[ inhibitor].” Id. at *12. It also observed that neither 

valsartan nor sacubitril were considered promising 

treatments for cardiac conditions in 2002. Id. Most 

importantly, in the court’s view, was “the fact that a large 

number of hypertension and heart failure drugs and drug 

classes were known in 2002—including multiple ARBs and 

a myriad of NEP[ inhibitors]—with no clear hierarchy 

within the ARB and NEP[ inhibitor] classes and no 

available information pointing directly at the claimed 

valsartan-sacubitril combination.” Id. The court further 

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rejected MSN’s “obvious-to-try” theory on the grounds that 

there was a “surfeit of potentialities with respect to drug 

combinations for heart failure and hypertension 

treatment,” such that MSN’s obviousness theory hinged on 

impermissible hindsight. Id. at *13.

Accordingly, the court determined that MSN had not 

shown by clear and convincing evidence that the claims of 

the ’659 patent were invalid as obvious. Id.

2. Written Description and Enablement

The court then turned to the issues of written 

description and enablement. Guided by the understanding 

that the court had “construed the asserted claims to cover 

valsartan and sacubitril as a physical combination and as 

a complex,” id. at *17, the parties’ dispute centered on 

whether the ’659 patent was required to enable and 

describe such complexes. MSN argued that it was, since a 

patent must enable and describe the full scope of the 

claims. E.g., id. at *17, *21. Novartis disagreed, arguing 

that a complex of valsartan and sacubitril was an afterarising invention that need not have been enabled or 

described. E.g., id. at *18–19. More specifically, Novartis 

contended that its “later, nonobvious discovery of valsartan 

and sacubitril in the form of a complex should not 

invalidate the ’659 patent claims to Novartis’s earlier 

invention: the novel combination of valsartan and 

sacubitril.” J.A. 4219. The court agreed with Novartis on 

the issue of enablement, but with MSN on the issue of 

written description.

With respect to enablement, the court determined that, 

because enablement is judged as of the priority date, laterexisting state of the art may not be properly considered in 

the enablement analysis. Decision, at *19 (relying on In re 

Hogan, 559 F.2d 595 (CCPA 1977); Plant Genetic Sys., N.V. 

v. DeKalb Genetics Corp., 315 F.3d 1335 (Fed. Cir. 2003);

Chiron Corp. v. Genentech, Inc., 363 F.3d 1247 (Fed. Cir. 

2004)). And because complexes of valsartan and sacubitril 

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were unknown in the art in 2002, the court determined that 

they need not have been enabled in the ’659 patent. Id. at 

*20. The court further found that MSN had failed to 

establish that pharmaceutical complexes, more generally,

were known or were nascent technology as of the 2002 

priority date. Id. at *20–21. Accordingly, the court

determined that MSN had failed to establish that the 

claims of the ’659 patent were invalid for lack of 

enablement.

The court reached the opposite conclusion with respect 

to written description. Relying primarily on Chiron, the 

court found that “the facts that helped [Novartis] with 

respect to enablement proved fatal for written description.” 

Id. at *21. Specifically, because it was undisputed that 

complexes were unknown to a person of ordinary skill in 

the art, “‘[Novartis] scientists, by definition, could not have 

possession of, and disclose, the subject matter of [such 

complexes]’ in 2002, and therefore, ‘axiomatically, 

[Novartis] cannot satisfy the written description 

requirement’ for such complexes.” Id. at *22 (quoting 

Chiron, 363 F.3d at 1255 (first and second alteration in 

original)). Thus, the court found the claims invalid for lack 

of written description and entered judgment on that basis.

Novartis timely appealed. We have jurisdiction under 

28 U.S.C. § 1295(a)(1).

DISCUSSION

Novartis challenges the district court’s findings on 

written description. MSN counters that, even if the claims 

are supported by adequate written description, the 

judgment of invalidity should be affirmed by reversing the 

district court’s determinations on obviousness and 

enablement. We address each issue in turn.

I

We begin with written description. The issue on appeal 

is whether the ’659 patent describes what is claimed, viz.,

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a pharmaceutical composition comprising valsartan and 

sacubitril administered “in combination.” The issue is not 

whether the ’659 patent describes valsartan-sacubitril 

complexes. Because the ’659 patent does not claim 

valsartan-sacubitril complexes, those complexes need not 

have been described.

As we have long recognized, “[t]he invention is, for 

purposes of the ‘written description’ inquiry, whatever is 

now claimed.” Vas-Cath Inc. v. Mahurkar, 935 F.2d 1555, 

1564 (Fed. Cir. 1991). “A specification adequately describes 

an invention when it ‘reasonably conveys to those skilled 

in the art that the inventor had possession of the claimed 

subject matter as of the filing date.’” Juno Therapeutics, 

Inc. v. Kite Pharma, Inc., 10 F.4th 1330, 1335 (Fed. Cir. 

2021) (quoting Ariad Pharms. Inc. v. Eli Lilly & Co.,

598 F.3d 1336, 1351 (Fed. Cir. 2010) (en banc)). The scope 

of what is claimed (and must be adequately described) is, 

in turn, determined through claim construction. Phillips 

v. AWH Corp., 415 F.3d 1303, 1312 (Fed. Cir. 2005) (en 

banc) (“It is a bedrock principle of patent law that the 

claims of a patent define the invention to which the 

patentee is entitled a right to exclude.” (internal quotation 

marks and citation omitted)).

Recall that, at claim construction, MSN sought—as 

accused infringers often do—a construction that would 

exclude from infringement the accused product: 

a valsartan-sacubitril complex. The court ultimately 

rejected MSN’s proposed construction because the ’659 

patent “is silent on whether sacubitril and valsartan must 

be separate (and not complexed).” Claim Construction 

Decision, at *3. The term was therefore given its plain and 

ordinary meaning: “wherein said [valsartan and sacubitril] 

are administered in combination.” Id.

That invention is plainly described throughout the 

specification. For example, the opening sentence of the 

detailed description provides that “the present invention 

relates to pharmaceutical combinations comprising 

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valsartan . . . and a NEP inhibitor . . . and pharmaceutical 

compositions comprising them.” ’659 patent col. 3 ll. 20–25

(emphases added); see also id. col. 6 ll. 65–67 (“It can be 

shown that combination therapy with valsartan and a NEP 

inhibitor results in a more effective anti-hypertensive 

therapy[.]” (emphasis added)). The patent further specifies 

that the NEP inhibitor used in combination with valsartan 

can be sacubitril. Id. col. 7 ll. 33–36 (“Representative 

studies are carried out with a combination of valsartan and 

[sacubitril.]” (emphasis added)). And it further teaches 

that “[a] therapeutically effective amount of each of the 

component[s] of the combination of the present invention

may be administered simultaneously or sequentially in any 

order.” Id. col. 10 ll. 57–59 (emphasis added). Those 

disclosures (and more) plainly show that the inventors had 

possession of a pharmaceutical composition comprising 

valsartan and sacubitril administered “in combination.” 

Indeed, even MSN’s expert conceded that the ’659 patent 

adequately discloses administration of valsartan and 

sacubitril in combination as a physical mixture. See J.A. 

3322. Thus, the claims are supported by an adequate 

written description.4

The fact that the ’659 patent does not describe a 

complexed form of valsartan and sacubitril does not affect 

the validity of the patent. That complex—not 

discovered until four years after the priority date of the ’659 

patent—is not what is claimed. By stating that the claims 

were “construed to cover complexes of valsartan and 

sacubitril,” the district court erroneously conflated the 

distinct issues of patentability and infringement, which led 

it astray in evaluating written description. Decision, at *15 

(emphasis added). Written description asks whether that 

4 MSN does not argue that the other limitations of 

the asserted claims are not adequately described. 

Accordingly, we focus our inquiry on only the disputed 

claim term: “in combination.”

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which is claimed is adequately described. As we have 

explained:

[C]laims are not construed “to cover” or “not to 

cover” the accused [product]. That procedure 

would make infringement a matter of judicial 

whim. It is only after the claims have been 

construed without reference to the accused device

that the claims, as so construed, are applied to the 

accused device to determine infringement.

SRI Int’l, 775 F.2d at 1118. 

Here, after claim construction, MSN stipulated to 

infringement of the as-construed claims.5 In light of that 

stipulation and the fact that the ’659 patent does not claim 

valsartan-sacubitril complexes, any further issue 

regarding such complexes is not before us.

For those reasons, we hold that the district court 

clearly erred in finding that claims 1–4 of the ’659 patent 

are invalid for lack of written description. The patent has 

an adequate written description of what is claimed.

5 To the extent MSN maintains that the claims were 

construed to claim valsartan-sacubitril complexes (i.e., to 

the extent MSN alleges that its stipulation of infringement 

was made on that basis), that construction would have 

been error. “Claim interpretation requires the court to 

ascertain the meaning of the claim to one of ordinary skill 

in the art at the time of invention.” SmithKline Beecham 

Corp. v. Apotex Corp., 403 F.3d 1331, 1338 (Fed. Cir. 2005) 

(emphasis added); see Phillips, 415 F.3d at 1313. Because 

valsartan-sacubitril complexes were undisputedly 

unknown at the time of the invention, see Decision, at *20,

the ’659 patent could not have been construed as claiming 

those complexes as a matter of law.

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II

We affirm the district court’s enablement 

determination for reasons similar to those that led us to 

reverse its written description determination: a 

specification must only enable the claimed invention. See 

Amgen v. Sanofi, 598 U.S. 594, 610 (2023). 

The invention of the ’659 patent, as construed by the 

district court, is a composition in which valsartan and 

sacubitril are administered “in combination.” As explained

above, the patent does not claim as its invention valsartansacubitril complexes. Indeed, Novartis obtained separate, 

later patents to such complexes. See Claim Construction 

Decision, at *1 (noting that “[s]everal years” after filing the 

’659 patent, “Novartis developed a novel compound 

comprising non-covalently bound valsartan and sacubitril

salts,” which are disclosed in U.S. Patents 8,877,938 and 

9,388,134).

The district court correctly recognized that valsartansacubitril complexes, which include the claimed invention 

along with additional unclaimed features, are part of a 

“later-existing state of the art” that “may not be properly 

considered in the enablement analysis.” Decision, at *19; 

see In re Hogan, 559 F.2d 595, 606 (CCPA 1977) (holding 

that enablement must be judged in light of the state of the 

art at the time of filing); Plant Genetic, 315 F.3d at 1340 

(“[O]ne [can]not use a later-existing state of the art to 

invalidate a patent that was enabled for what it claimed at 

the time of filing.”). As our predecessor court explained:

The use of a subsequently-existing improvement to 

show lack of enablement in an earlier-filed 

application on the basic invention would preclude 

issuance of a patent to the inventor of the thing 

improved, and in the case of issued patents, would 

invalidate all claims (even some “picture claims”) 

therein. Patents are and should be granted to later 

inventors upon unobvious improvements. Indeed, 

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encouragement of improvements on prior 

inventions is a major contribution of the patent 

system and the vast majority of patents are issued 

on improvements. It is quite another thing, 

however, to utilize the patenting or publication of 

later existing improvements to “reach back” and 

preclude or invalidate a patent on the underlying 

invention.

Hogan, 559 F.2d at 606. That is precisely the case here. 

The later-discovered valsartan-sacubitril complexes, which 

arguably may have improved upon the “basic” or 

“underlying” invention claimed in the ’659 patent, cannot

be used to “reach back” and invalidate the asserted claims.

Thus, because the ’659 patent does not expressly claim 

complexes, and because the parties do not otherwise 

dispute that the ’659 patent enables that which it does 

claim, we affirm the district court’s determination that 

MSN failed to show that the claims are invalid for lack of 

enablement.

III

Finally, we turn to obviousness. “Obviousness is a 

question of law based on underlying findings of fact.” 

Adapt Pharma Operations Ltd. v. Teva Pharms. USA, Inc., 

25 F.4th 1354, 1364 (Fed. Cir. 2022) (citations omitted). 

Whether a person of ordinary skill in the art would have 

been motivated to combine the prior-art references to 

arrive at the claimed invention is a factual question we 

review for clear error. Id.

We see no clear error warranting reversal of the district 

court’s obviousness analysis. The district court found that, 

even if a person of ordinary skill in the art had been 

motivated to provide an ARB-NEP inhibitor combination 

therapy, there was no motivation in the relied-upon prior 

art to combine valsartan and sacubitril, let alone with any 

reasonable expectation of success. As of 2002, sacubitril 

was one of over 100 known NEP inhibitors, it had never 

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been administered to humans or animals, and the clinical 

results of other NEP inhibitors in hypertension and heart 

failure patients had been “discouraging.” See Decision, at 

*7.

Those facts, as the district court acknowledged, 

distinguish this case from Nalproprion Pharmaceuticals, 

Inc. v. Actavis Laboratories FL, Inc., 934 F.3d 1344 (Fed. 

Cir. 2019), and BTG International Ltd. v. Amneal 

Pharmaceuticals LLC, 923 F.3d 1063 (Fed. Cir. 2019), on 

which MSN relies. In each of those cases, the prior art 

showed that the claimed drugs “were both together and 

individually considered promising . . . treatments at the 

time [of the invention].” BTG, 923 F.3d at 1074; see 

Nalproprion Pharms., 934 F.3d at 1354 (concluding that,

because the prior art taught that each drug could cause 

weight loss effects, “a person of ordinary skill would have 

been motivated to combine them” to promote weight loss). 

That is not the case here, at least with respect to sacubitril. 

We therefore agree with the district court that MSN’s 

obviousness theories impermissibly use valsartan and 

sacubitril as a starting point and “retrace[] the path of the 

inventor with hindsight.” Decision, at *13 (citation 

omitted).

Accordingly, because we see no errors in the district 

court’s factual findings or application of the law, we affirm 

the district court’s determination that MSN failed to 

establish that the claims would have been obvious.

CONCLUSION

We have considered the parties’ remaining arguments 

and find them unpersuasive. For the foregoing reasons, we 

reverse the district court’s finding that the claims lack 

adequate written description, and we affirm its 

determinations that the claims were not shown to have 

been obvious or non-enabled.

AFFIRMED IN PART, REVERSED IN PART

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COSTS

Costs to Novartis.

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