United States Court of Appeals 

for the Federal Circuit ______________________ 

RICHARD STORER, GILLES GOSSELIN, JEANPIERRE SOMMADOSSI, PAOLA LACOLLA,

Appellants

v.

JEREMY CLARK,

Appellee

UNITED STATES,

Intervenor

______________________ 

2015-1802

______________________ 

Appeal from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in No. 105,981.

______________________ 

Decided: June 21, 2017

______________________ 

GREGORY A. CASTANIAS, Jones Day, Washington, DC, 

argued for appellants. Also represented by JENNIFER 

LORAINE SWIZE; ANTHONY M. INSOGNA, JOHN DAVID 

KINTON, San Diego, CA; THOMAS EUGENE FRIEBEL, New 

York, NY; CALVIN GRIFFITH, Cleveland, OH.

 

FRANK SCHERKENBACH, Fish & Richardson PC, Boston, MA argued for appellee. Also represented by 
2 STORER v. CLARK

JONATHAN ELLIOT SINGER, CRAIG E. COUNTRYMAN, W.

CHAD SHEAR, San Diego, CA. 

JOSEPH FORREST BUSA, Appellate Staff, Civil Division, 

United States Department of Justice, Washington, DC, 

argued for intervenor. Also represented BY MARK R.

FREEMAN, BENJAMIN C. MIZER; THOMAS W. KRAUSE, Office 

of the Solicitor, United States Patent and Trademark 

Office, Alexandria, VA.

______________________ 

Before PROST, Chief Judge, NEWMAN, and DYK, Circuit 

Judges.

NEWMAN, Circuit Judge. 

This patent interference contest involves methods of 

treating hepatitis C by administering compounds having 

a specific chemical and stereochemical structure, based on 

the following foundation formula of a five-membered ring 

having the fluorine substituent in the 2 ́(down) position:

Storer Br. at 8. The priority decision was based on enablement of this product. The interference was declared

between an issued patent (Storer et al.) and a pending 

application (Clark), both of which were filed before the 

effective date of the America Invents Act, the statute that 

abolished the first-to-invent interference rule in favor of a 
STORER v. CLARK 3

first-to-file rule. By the terms of the Act, § 3(n)(2), the 

prior, first-to-invent, law applies to this interference.

To establish priority, Storer relied on the disclosure in 

the provisional specification from which priority was 

claimed for conception and constructive reduction to 

practice. In its joint decision on Clark’s motion to deny 

Storer the benefit of the provisional application and on 

Clark’s motion to invalidate Storer’s claims on the 

grounds of lack of enablement and written description,1

the Patent Trial and Appeal Board (PTAB or “Board”) 

held that Storer’s provisional application was not enabling for the count of the interference, and on that ground 

the PTAB entered judgment granting priority to Clark.2 

Storer appeals that judgment and the underlying decision 

on Clark’s motions. 

We take note that Storer initially filed in the District 

of Delaware, seeking review of the Board’s decision under 

35 U.S.C. § 146. The district court dismissed the case, 

Idenix Pharmaceuticals. LLC v. Gilead Pharmasset LLC, 

2016 WL 6804915, at *1 (D. Del. Nov. 16, 2016), based on 

this court’s ruling in Biogen MA, Inc. v. Japanese Foundation for Cancer Research, 785 F.3d 648 (Fed. Cir. 2015), 

that the America Invents Act eliminated the option of 

district court review under Section 146 for interferences 

declared after September 15, 2012. Although Storer says 

that Biogen was incorrectly decided, that decision is 

binding on this panel. Storer’s appeal of the district 

court’s dismissal has been stayed pending the outcome of 

1 Decision on Motions – Bd.R. 125, Clark v. Storer, 

Interference No. 105,981, (P.T.A.B. Jan. 16, 2015), Doc 

No. 687 (“Bd. Op.”).

2 Clark v. Storer, Interference No. 105,981, 2015 

WL 1325503 (P.T.A.B. Mar. 23, 2015).

 
4 STORER v. CLARK

this appeal. Order, Idenix Pharm. LLC v. Gilead Pharmasset LLC, No. 17-1369 (Fed. Cir. Feb. 16, 2017).

BACKGROUND

Inventors Richard Storer et al. were issued U.S. Patent No. 7,608,600 (“the ‘600 Patent”), on a final application filed on June 27, 2003. The patent is assigned to

Idenix Pharmaceuticals. In the interference proceeding, 

Storer was initially declared the senior party based on the 

June 28, 2002 filing date of provisional application No. 

60/392,350 (called “the S1 application” by the Board). 

Clark’s Application No. 11/854,218, assigned to Gilead 

Pharmasset, was filed September 12, 2007, with priority 

claimed to a provisional application filed on May 30, 2003.

Clark moved to deny Storer the priority date of the S1

application and to invalidate Storer’s claims, arguing that 

the S1 application did not enable compounds having the 

2 ́F(down) substituent. Storer argued that these compounds were generically disclosed in the S1 application, 

and were readily obtained based on the disclosure in the 

S1 provisional and the prior art. The Board did not agree, 

and by withdrawing entitlement to the provisional’s filing 

date, the Board awarded priority to Clark. Storer now 

appeals that decision.

DISCUSSION

The Interfering Claims

Storer and Clark were investigating the treatment of

hepatitis C using modified nucleoside compounds, including certain heterocyclic compounds having a fluorine

substituent in the 2 ́ position. The PTAB identified the 

interfering subject matter, and selected claims for purposes of determining priority. From the Storer patent, the 

Board selected claim 1:

1. A method for the treatment of a host infected 

with a hepatitis C virus, comprising administer-
STORER v. CLARK 5

ing to the host infected with a hepatitis C virus an 

effective amount of a compound having the formula:

or a pharmaceutically acceptable salt thereof, 

wherein:

R1 is H; mono-, di- or triphosphate; acyl; an amino 

acid ester; a carbohydrate; a peptide;

or a pharmaceutically acceptable leaving group 

which when administered in vivo provides a compound wherein R1 is H or phosphate;

R2 is H; acyl; an amino acid ester; a carbohydrate; 

a peptide; or a pharmaceutically acceptable leaving group which when administered in vivo provides a compound wherein R2 is H;

Base* is selected from the group consisting of adenine, N6-alkylpurine, N6-acylpurine, N6-

benzylpurine, N6-halopurine, N6-vinylpurine, N6-

acetylenic purine, N6-acyl purine, N6-

hydroxyalkylpurine, N6-alkylamino-purine, N6-

thioalkyl purine, N2-alkylpurine, N2-alkyl-6-

thiopurine, thymine, cytosine, 5-fluorocytosine, 5-

methylcytosine, 6-azapyrimidine, 6-azacytosine, 2- 

and/or 4-mercaptopyrimidine, uracil, 5-halouracil, 

5-fluorouracil, C5-alkylpyrimidine, C5-

benzylpyrimidine, C5-halopyrimidine, C5-

vinylpyrimidine, C5-acetylenic pyrimidine, C5-acyl 
6 STORER v. CLARK

pyrimidine, C5-hydroxyalkyl purine, C5-

amidopyrimidine, C5-cyanopyrimidine, C5-

iodopyrimidine, C6-iodo-pyrimidine, C5-Br-vinyl 

pyrimidine, C6-Br-vinylpyrimidine, C5-

nitropyrimidine, C6-amino-pyrimidine, N2-

alkylpurine, N2-alkyl-6-thiopurine, 5-azacytidinyl, 

5-azauracilyl, triazolopyridinyl, imidazolopyridinyl, pyrrolopyrimidinyl, pyrazolopyrimidinyl, 

guanine, hypoxanthine, 2,6-diaminopurine, and 6-

choropurine;

R12 is C(Y3)3; and

Y3 is independently H or F.

From the Clark application, the Board selected claim 164:

164. A method for the treatment of hepatitis C infection, which comprises:

administering to a mammal in need thereof an antivirally effective amount of a (2ˊR)-2ˊ-deoxy-2ˊfluoro-2ˊ-C-methyl nucleoside (β-D or β-L) or its 

pharmaceutically acceptable salt of the structure:

wherein R1 and R7 are independently H, a monophosphate, a diphosphate, a triphosphate, a Hphosphonate, an alkyl, an alkyl sulfonyl, or an arylalkyl sulfonyl; and R4 is NH2 or OH.
STORER v. CLARK 7

The parties agree that the only question focuses on 

whether the Storer S1 provisional together with the prior 

art enabled compounds having a 2 ́F(down) substituent. 

Enablement

Enablement is relevant for validity and to the issue of 

whether the provisional application is a constructive 

reduction to practice. “Constructive reduction to practice 

means a described and enabled anticipation under 35 

U.S.C. 102(g)(1), in a patent application of the subject 

matter of a count.” 37 C.F.R. § 41.201. “When a party to 

an interference seeks the benefit of an earlier-filed United 

States patent application, the earlier application must 

meet the requirements of 35 U.S.C. § 120 and 35 U.S.C. § 

112 ¶ 1 for the subject matter of the count.” Hyatt v. 

Boone, 146 F.3d 1348, 1352 (Fed. Cir. 1998) (footnotes 

omitted). Section 112 ¶ 1 requires:

The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, 

concise, and exact terms as to enable any person 

skilled in the art to which it pertains, or with 

which it is most nearly connected, to make and 

use the same, and shall set forth the best mode 

contemplated by the inventor of carrying out his 

invention.

35 U.S.C. § 112, para. 1.3 Therefore, when the issue is 

priority based on the content of the specification, “[t]he 

earlier application must contain a written description of 

the subject matter of the interference count, and must 

meet the enablement requirement.” Hyatt, 146 F.3d at 

1352.

3 This section is now § 112(a).

 
8 STORER v. CLARK

Enablement is a matter of law, and is reviewed without deference; however, the factual underpinnings of 

enablement are reviewed for support by substantial 

evidence on the entirety of the PTO record. Microsoft 

Corp. v. Proxyconn, Inc., 789 F.3d 1292, 1297 (Fed. Cir. 

2015). To establish enablement of a claim whereby new 

chemical compounds are provided for use to treat disease, 

the application must enable production or synthesis of the 

new compounds. See In re Brebner, 455 F.2d 1402, 1404 

(C.C.P.A. 1972) (“A method of making starting materials 

not known in the art must be set forth in order to comply 

with the enablement requirement.”).

The Board held that the S1 provisional, taken together with the prior art, did not enable the specific compounds having the identified structure. Storer argued, 

and repeats on appeal, that a person of ordinary skill 

would have been able to make this class of compounds, 

having the requisite stereochemistry, based on information in the S1 provisional application and the prior art. 

“The enablement requirement is met where one skilled in 

the art, having read the specification, could practice the 

invention without ‘undue experimentation.’” Streck, Inc. 

v. Research & Diagnostic Sys., Inc., 665 F.3d 1269, 1288 

(Fed. Cir. 2012) (quoting ALZA Corp. v. Andrx Pharm., 

LLC, 603 F.3d 935, 940 (Fed. Cir. 2010)). 

“Whether undue experimentation is required ‘is not a 

single, simple factual determination, but rather is a 

conclusion reached by weighing many factual considerations.’” Id. As summarized in In re Wands, 858 F.2d 731, 

737 (Fed. Cir. 1988), relevant factors may “include (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.”
STORER v. CLARK 9

The Board determined that the claimed compounds 

having a 2 ́F(down) substituent were not enabled in 

Storer’s S1 provisional application, in that undue experimentation would be required to produce this structure. 

The Board analyzed the disclosure in terms of the evidentiary factors set forth in Wands. 

Storer does not dispute the Board’s findings as to the 

third, fourth, fifth, sixth, and eighth Wands factors, but 

argues that these factors are not dispositive of enablement. For the third Wands factor—the presence or absence of working examples—Storer does not dispute that 

the S1 provisional contains no specific examples of synthesis of compounds having the fluoro substituent in the 

2 ́(down) position. Bd. Op. at 24.

For the fourth Wands factor—the nature of the invention—the Board found that:

Count 1 is best characterized as the administration of a genus of nucleosides used in the treatment of viruses, particularly those of the family 

Flaviviridae (which includes HBV and HCV). We 

also find that, as of the time of filing of the S1 application, although organic fluoridation mechanisms were generally well-known in the art a 2ˊfluoro-2ˊ-methyl nucleoside with the fluoro substituent in the “down” position had not yet been 

synthesized.

Id. at 25 (footnote omitted). Storer does not dispute this 

finding.

For the fifth Wands factor—the state of the prior 

art—the Board found that:

although DAST [N,N-diethylamino-sulfur trifluoride] was well-known in the prior art as fluoridating agent for nucleosides and nucleoside analogs, 

the prior art did not teach, or explicitly suggest, 

the use of DAST in the fluoridation of a tertiary 
10 STORER v. CLARK

alcohol to convert a tertiary alcohol at a nucleoside 2ˊ position to a tertiary fluorine at the nucleoside 2ˊ “down” position. We further find that, 

although organic fluoridation techniques were 

well-known in the art at the time the S1 application was filed, fluoridation of tertiary alcohols to 

produce a 2ˊ “down” tertiary fluorine was not 

taught or suggested by the prior art.

Id. at 29. Storer does not dispute this finding.

With respect to the sixth Wands factor, the Board particularly relied on Wands factors 1, 2, 3, 4, and 7 and 

found that “the parties largely agree that the level of skill 

in the art is very high” and that

a person possessing the ordinary level of skill in 

this art, as of the time of the invention, would 

hold a doctoral degree in the field of organic, synthetic, or medicinal chemistry with at least a 

year’s experience in the field of nucleoside synthesis or relevant drug discovery.

Id. at 29–30. The Board also found that neither party 

argued the eighth Wands factor regarding the breadth of 

the claims. Id. at 34 n.64. These findings are not disputed.

The Board summarized the evidence and findings on 

which it concluded that undue experimentation would be 

needed to produce the designated molecule: 

(1) synthesis of a 2ˊ-fluoro-2ˊ-methyl nucleoside 

with the fluoro moiety in the “down” position required at least two years of a high-priority experimentation by persons skilled in the art, including 

multiple consultations with experts at the top of 

their fields and additional formal training; 
STORER v. CLARK 11

(2) the S1 application provides little in the way of 

direction or guidance as to how to synthesize such 

a compound; 

(3) the S1 application provides no explicit example 

of a 2ˊ-fluoro-2ˊ-methyl nucleoside, nor was an example provided by the relevant art as of the S1

application’s filing date; 

(4) the invention is characterized as the administration of a genus of nucleosides used in the 

treatment of viruses, particularly those of the 

family Flaviviridae (which includes HBV and 

HCV) and an embodiment of the count requires a 

2ˊ-fluoro(“down”) 2ˊ-methyl nucleoside; 

(5) although organic fluoridation techniques were 

well-known in the art at the time the S1 application was filed, fluoridation of tertiary alcohols to 

produce a 2ˊ “down” tertiary fluorine was not 

taught or suggested by the prior art; 

(6) the level of skill in the art was highly sophisticated: a person possessing the ordinary level of 

skill in this art, as of the time of invention, would 

hold a doctoral degree in the field of organic, synthetic, or medicinal chemistry with at least a 

year’s experience in the field of nucleoside synthesis or relevant drug discovery; and 

(7) the art, at least with respect to fluoridation of 

tertiary alcohols to produce a tertiary fluorine in 

the 2ˊ “down” position, was highly unpredictable.

We therefore find that Wands factors 1, 2, 3, 5, 

and 7 strongly indicate that a person skilled in the 

art would not arrive at the claimed invention 

without undue experimentation.

Id. at 34–35.
12 STORER v. CLARK

Based on these findings, the Board concluded that the 

interference subject matter was not enabled by Storer’s 

S1 provisional application.

Argument on Appeal

Storer argues that the S1 provisional application “performed the substantial step of disclosing the precise 

chemical structure of the target compound.” Storer Br. at 

47. Storer does not, however, identify any specific structure having the 2 ́F(down) substituent. The pages of the 

S1 provisional cited by Storer include generic structures, 

and Clark does not dispute that the “target compounds,”

as the Board calls the 2 ́F(down) compounds, are generically included in the S1 provisional application’s generic 

formulas.

Storer states that the prior art contains “a well-known 

precursor compound that is only one step away from the 

target compound.” Id. at 8. Storer states that this precursor is “Matsuda Compound 17,” citing Akira Matsuda 

et al., Alkyl Addition Reaction of Pyrimidine 2 ́-

Ketonucleosides: Synthesis of 2 ́-Branched-Chain Sugar 

Pyrimidine Nucleosides (Nucleosides and Nucleotides 

LXXXI), 36 CHEMICAL & PHARMACEUTICAL BULL., no. 3, 

Mar. 1988, at 945.

Matsuda Compound 17 is presented in Storer’s brief

as
STORER v. CLARK 13

Storer Br. at 12. Matsuda Compound 17 contains a 

methyl group in the 2 ́(down) position, and Storer states 

that Matsuda Compound 17 is readily converted into the 

target compound by known methods to produce the desired stereochemistry. Matsuda Compound 17 is not 

mentioned in the S1 provisional, but Storer argues that 

the precursor to Matsuda Compound 17 is in the S1 

provisional, “as is that precursor’s conversion to the 

Matsuda compound,” Id. at 48 n.16. Storer states that the 

precursor “is only two steps away from the desired 2 ́-

methyl ‘up’, 2 ́-fluoro ‘down’ configuration,” and “each 

scheme discloses how to modify the 2 ́-keto precursor to 

obtain” Matsuda Compound 17. Id. at 9.

Thus Storer argues that the Matsuda reference, together with the information in the S1 provisional, enable 

synthesis of 2 ́F(down) compounds. Storer states that 

Schemes 3, 4 and 8 in the S1 provisional each describes a 

“2 ́-keto precursor, i.e., a compound with ‘=O’ at the 2 ́ 

position,” and that this is the path to the 2 ́F(down) 

molecule. Id. at 9. The three schemes from the S1 provisional are: 
14 STORER v. CLARK

Storer Prov. Appl. at 119.
STORER v. CLARK 15

Id. at 120. 

Id. at 1948.

These three schemes indeed show a compound with 

=O at the 2 ́ position, but none shows conversion to

Matsuda Compound 17 or further conversion to the

2 ́F(down) analog. Clark points out that each scheme 

produces compounds with the opposite spatial arrangement from Matsuda Compound 17, for in Matsuda Compound 17 the 2 ́-OH is “up,” whereas in Scheme 4 the 2 ́-

OH is “down.” Clark Br. at 5.

Storer does not dispute the chemical facts, but argues

that the difference between Matsuda 17 and the provisional synthesis schemes does not negate enablement 

because

if the alkylation reagent is methyl lithium (MeLi) 

or methyl Grignard (MeMgBr) for methylation as 

taught by the specification, one of ordinary skill in 

the art will obtain products with the orientation 

(i.e., “stereochemistry”) of the OH and methyl 

groups needed to synthesize the target compound 

using DAST or Deoxo-Fluor. Furthermore, the 

prior art teaches how to control the stereochemistry of these groups.
16 STORER v. CLARK

Storer Br. at 9-10 n.5. Although the S1 provisional 

schemes show products with the opposite stereochemistry, 

Storer argues that a person of ordinary skill could make 

Matsuda Compound 17 employing these schemes. Storer 

argues that “a skilled artisan would have recognized that 

Matsuda Compound 17 was a viable precursor,” id. at 48, 

and that: “With knowledge of those structures, the hypothetical person would have known to use a common, onestep synthesis to modify the well-known precursor to 

obtain the target compound.” Id. Storer states that 

“simply by looking at the chemical structure of the target 

compound disclosed by Idenix, a person of ordinary skill 

would know to use a fluorination reagent,” id., and “DAST 

and Deoxo-Fluor were the most well-known fluorinating 

reagents at the time for one-step fluorination reactions.” 

Id. at 49. Storer argues that Matsuda provides any 

necessary information not in the S1 provisional.

Clark responds that these are overstatements, for neither Matsuda Compound 17 nor any compound with the 

2 ́F(down) structure is mentioned in the Storer S1 provisional. Clark points out that none of the several synthetic 

schemes in Storer’s provisional application shows conversion of any precursor into Matsuda Compound 17. Clark 

states that Storer’s synthetic schemes only disclose compounds with the “wrong stereochemistry.” Clark Br. at 

37.

The Board agreed with Clark’s position, and held that 

the S1 provisional’s description of the 2 ́-keto precursor, in 

combination with the Matsuda reference, was insufficient 

to enable and thereby to establish possession of the

2 ́F(down) methyl(up) compound of claim 1 before Clark’s 

priority date. The Board stated, correctly, that for new 

chemical compounds the specification must provide sufficient guidance that undue experimentation is not required to obtain the new compounds.
STORER v. CLARK 17

ANALYSIS

The boundary between a teaching sufficient to enable 

a person of ordinary skill in the field, and the need for 

undue experimentation, varies with the complexity of the 

science. Knowledge of the prior art is presumed, as well 

as skill in the field of the invention. The specification

need not recite textbook science, but it must be more than 

an invitation for further research. Genentech, Inc. v. Novo 

Nordisk A/S, 108 F.3d 1361, 1366 (Fed. Cir. 1997).

In Genentech the patentee argued that the prior art 

taught a method that could be used to produce a claimed 

human growth hormone product, compensating for lack of 

detail in the specification. The patentee argued that it 

did not need to include information in the prior art. This 

court agreed, but stressed the need to assure enablement 

of the novel aspects of the invention: 

It is true . . . that a specification need not disclose 

what is well known in the art. See, e.g., Hybritech 

Inc. v. Monoclonal Antibodies, Inc., 802 F.2d 1367, 

1385 (Fed. Cir. 1986). However, . . . . [i]t is the 

specification, not the knowledge of one skilled in 

the art, that must supply the novel aspects of an 

invention in order to constitute adequate enablement.

Genentech, 108 F.3d at 1366.

The Storer provisional specification does not describe 

synthesis of the 2 ́F(down) target compounds. The question devolves to the adequacy of the disclosure in the 

provisional of general schemes for synthesizing these 

general classes of modified nucleosides, taken with the

knowledge of the art. The S1 provisional discloses two 

general approaches. Provisional schemes 3 and 8 modify 

the sugar portion of the target compound and then add 

the base portion, as the provisional application calls the
18 STORER v. CLARK

“Glycosylation of the nucleobase with an appropriately 

modified sugar.” Storer Prov. Appl. at 117.

Provisional scheme 4 shows modifying a compound 

with the base already attached, to achieve the desired 

structure. The provisional calls this “Modification of a 

pre-formed nucleoside.” Id. at 119. The Board observed 

that none of the approaches in the provisional proceeds 

through a compound like Matsuda Compound 17, or 

suggests how Matsuda 17 may be converted into the

target 2 ́F(down) compounds. The Board found that the 

Storer provisional does not exemplify such a reaction, or 

lead a person of ordinary skill to perform it. The Board 

also observed that the S1 provisional schemes produce 

compounds with opposite spatial arrangement from 

Matsuda Compound 17.

On review, we conclude that substantial evidence 

supports the Board’s findings that the synthetic schemes 

in Storer’s provisional application do not teach or suggest 

conversion of any precursor into the 2 ́F(down) structure, 

and that the Matsuda synthesis of a corresponding 2 ́-

methyl (down), 2 ́-hydroxyl (up) structure does not enable 

a person of ordinary skill to produce the target compounds 

without undue experimentation.

Wands factor 7, the predictability or unpredictability 

of the art, appears to be particularly relevant. Although 

Storer states that this is predictable chemistry, and 

therefore that detailed specific examples are not necessary, the Board’s findings are in accord with the record. 

The Board found: 

Having reviewed the parties’ arguments, and the 

proffered evidence, we find that the art, with respect to fluoridation of tertiary alcohols, was highly unpredictable, as evidenced by Idenix’s 

repeatedly unsuccessful attempts to synthesize its 

high-priority target nucleoside, and as further 
STORER v. CLARK 19

evinced by the statements of Dr. Coe and Dr. 

Storer. 

Bd. Op. at 33–34. Regarding Dr. Coe’s and Dr. Storer’s 

statements, the Board stated:

Dr. Paul Coe, an expert in organofluorines, expressed skepticism regarding the use of DAST; 

and Dr. Richard Storer stated that “[a] lot of 

things which look simple on paper in related systems have been tried and don’t work in this series. 

Having to make the tertiary fluoride is very different to [sic] having to make secondary.” 

Id. at 31 (quoting from the record). The Board also referred to evidence presented on behalf of Clark that 

“attempted fluorination reactions (including those involving DAST) could fail, resulting in unfluorinated elimination and/or rearrangement products, or products with 

incorrect stereochemistry.” Id. at 30. 

Even on Storer’s position that a person skilled in this 

science would have started with Matsuda Compound 17, 

Storer has not shown that the critical stereochemical 

result would predictably ensue, although the reaction had 

never been performed. The Board received evidence of 

side reactions and the skepticism of experts. The Board 

received evidence that Storer and his team had difficulty

and failures in synthesizing the target compound, as well 

as evidence that Clark and his team were more readily 

successful using apparently the same method. The 

Board’s finding that the chemistry was unpredictable is in 

accord with the evidence. 

The first Wands factor is concerned with “undue” experimentation, and recognizes that what is “undue” of 

itself depends on the subject matter and skill. The Board 

discussed the amount of experimentation needed to 

produce the claimed compounds, and found that: 
20 STORER v. CLARK

a high amount of experimentation is necessary to 

synthesize a 2 ́-fluoro-2 ́-methyl nucleoside with 

the fluoro moiety in the “down” position, requiring 

at least two years of a high priority experimentation by persons skilled in the art, including multiple consultations with experts at the top of the 

fields and additional formal training.

Id. at 19. The Board discussed the evidence showing 

Storer’s continuing research after the S1 provisional was 

filed, including the following findings: 

• “Idenix’s research team in Montpellier, 

France, repeatedly attempted without success 

to synthesize a 2 ́-methyl(“up”) 2 ́-

fluoro(“down”) nucleoside during the interval 

between December 2002 and September 

2004.” Id. at 14.

• “Idenix scientists also corresponded with consultants Dr. George Fleet and Dr. Paul Coe in 

an attempt to effect a synthesis of the desired 

compound.” Id. at 14.

• “Idenix personnel also attended a ‘Scientific 

Update Course’ entitled ‘Making and Using 

Fluoroorganic Molecules’ in April, 2003, and 

submitted a report summarizing the course 

content.” Id. at 15.

• “Dr. Jean-François Griffon, leader of the 

Montpellier group, testified that he attempted 

at least seven different synthetic schemes, including several suggested by Dr. Coe, and in 

some cases employing DAST, without success.” Id. at 15.

• “[A]ttempts by the Montpellier team to use 

DAST in the synthesis of a 2 ́-fluoro-2 ́-methyl 

nucleoside produced similar failures.” Id. at 

16.
STORER v. CLARK 21

• “With respect to the testimony of Jingyang 

Wang who allegedly synthesized the desired 

compound in a single attempt in January, 

2015, at Idenix’s research facility in Cambridge, Massachusetts, we note that, prior to 

beginning her synthesis, Ms. Wang had received the reports from the Montpellier group 

as well as intermediate compositions synthesized at Montpellier. Consequently, Ms. Wang 

was not, as Storer seems to suggest, attempting synthesis of a 2 ́-fluoro-2 ́methyl nucleoside ab initio, but rather had the hindsight 

benefit of the Montpellier group’s efforts.” Id.

at 17 (citations to the record omitted). 

Storer argues that the Board failed to address the fact 

that Clark readily synthesized a target compound in a 

single step from Matsuda Compound 17. The Board 

acknowledged Storer’s argument that it was “informative 

that Clark, a chemist without a Ph.D., was allegedly able 

to make a 2ˊ-methyl (up) 2ˊ-fluoro (down) nucleoside in 

just a few months using DAST.” Id. at 13. Storer states 

that “Clark’s experiments directly contradict the Board’s 

reliance on the allegedly failed attempts of Griffon.” 

Storer Br. at 55. There was evidence that Clark used a 

method similar to that attempted by Griffon on the Storer 

team, and that Clark succeeded where Griffon apparently

failed. Storer stated to the Board that Griffon actually 

produced the target compound, but was not able to purify 

it from the reaction mixture.

The Board found, on consideration of the entire record, that a person of ordinary skill, with the disclosure in 

the provisional application and knowledge of the prior art, 

would not have been led to make the target compound, 

and could not do so without undue experimentation. The 

Board received evidence that successful fluorination 

reactions of the desired stereochemistry had not been 

reported for structurally similar compounds.
22 STORER v. CLARK

We conclude that substantial evidence supports the 

Board’s finding that “a high amount of experimentation is 

necessary to synthesize” the target compound. The record 

before the Board showed sufficient variability and unpredictability to support the Board’s conclusion that Storer’s 

provisional application did not enable the interference

subject matter. The Board’s decision is affirmed.

AFFIRMED