NOTE: This disposition is nonprecedential.

United States Court of Appeals 

for the Federal Circuit ______________________

IMMUNOGEN, INC.,

Plaintiff-Appellant

v.

ANDREW HIRSHFELD, PERFORMING THE 

FUNCTIONS AND DUTIES OF THE UNDER 

SECRETARY OF COMMERCE FOR 

INTELLECTUAL PROPERTY AND DIRECTOR OF 

THE UNITED STATES PATENT AND TRADEMARK 

OFFICE,

Defendant-Appellee

______________________

2021-1939

______________________

Appeal from the United States District Court for the 

Eastern District of Virginia in No. 1:20-cv-00274-TSE-IDD, 

Judge T. S. Ellis, III.

______________________

Decided: March 25, 2022

______________________

MICHAEL E. JOFFRE, Sterne Kessler Goldstein & Fox, 

PLLC, Washington, DC, argued for plaintiff-appellant. 

Also represented by PAULINE PELLETIER, ERIC STEFFE.

 DANIEL KAZHDAN, Office of the Solicitor, United States

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2 IMMUNOGEN, INC. v. HIRSHFELD

Patent and Trademark Office, Alexandria, VA, argued for 

defendant-appellee. Also represented by MARY L. KELLY,

THOMAS W. KRAUSE, FARHEENA YASMEEN RASHEED;

MATTHEW JAMES MEZGER, RAJ PAREKH, Office of the United 

States Attorney for the Eastern District of Virginia, United 

States Department of Justice, Alexandria, VA.

______________________

Before NEWMAN, CLEVENGER, and STOLL, Circuit Judges.

CLEVENGER, Circuit Judge.

This case involves a civil action to obtain a patent under 35 U.S.C. § 145. Appellee ImmunoGen, Inc.’s (“ImmunoGen”) U.S. Application No. 14/509,809 (“the ’809 

Application”) describes methods of administering the immunoconjugate mirvetuximab for the treatment of cancer. 

After the Patent Trial and Appeal Board (“Board”) of the 

United States Patent and Trademark Office (“USPTO”) affirmed the examiner’s rejection of the pending claims for 

obviousness and obviousness-type double patenting, ImmunoGen filed its § 145 suit in the Eastern District of Virginia.

The district court determined on summary judgment 

that the claims of the ’809 Application are “fatally indefinite and fatally obvious” as a matter of law. ImmunoGen, 

Inc. v. Iancu, 523 F. Supp. 3d 773, 799 (E.D. Va. 2021). ImmunoGen appeals from the summary judgment. We have 

jurisdiction under 28 U.S.C. § 1295(a)(1).

In its analysis, the district court resolved numerous 

factual disputes against non-movant ImmunoGen, an error 

that is fatal to its ultimate ruling. We therefore vacate the 

grant of summary judgment and remand for proceedings 

consistent with this opinion.

THE ’809 APPLICATION

Immunoconjugates, such as mirvetuximab, are composed of an antibody coupled to a drug via a chemical 

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IMMUNOGEN, INC. v. HIRSHFELD 3

linker. The antibody portion allows the immunoconjugate 

to bind to a cell of interest, thereby permitting selective 

targeting of cancer cells for treatment. Mirvetuximab specifically targets Folate Receptor 1 (“FOLR1”), which is 

overexpressed in ovarian and peritoneal cancer cells.

Although mirvetuximab showed promise as a cancer 

treatment, Phase 1 clinical trials revealed it can have severe ocular side effects when administered at a dose of 

7 mg per kg of the patient’s total body weight (“TBW”). ImmunoGen determined that a dose of 6 mg per kg of the patient’s adjusted ideal body weight (“AIBW”) successfully 

maintains exposure of the drug at the therapeutically effective level while keeping it below the ocular toxicity 

threshold. It is undisputed that AIBW dosing had not previously been used for mirvetuximab, let alone any other immunoconjugate.1

ImmunoGen filed the ’809 Application to claim this 

AIBW dosing method. Claim 1 is representative:

1. A method for treating a human patient having 

an FOLR1-expressing ovarian cancer or cancer of 

the peritoneum comprising administering to the 

patient an immunoconjugate which binds to 

FOLR1 polypeptide,

wherein the immunoconjugate comprises an antibody or antigen-binding fragment thereof that comprises the variable light chain (VL) 

complementarity determining region (CDR)-1, VL 

CDR-2, VL CDR-3, variable heavy chain (VH) 

CDR-1, VH CDR-2, and VH CDR-3 of SEQ ID NOs: 

1 See, e.g., J.A. 9916–17, 9919 (Resps. to Request for 

Admission (“RFA”) Nos. 3 & 8–9); J.A. 10445 (Shah Dep. 

Tr. at 41:1–12); J.A.10655 (Tolcher Dep. Tr. at 55:4–19); 

J.A. 9992, 10043 (Figg Dep. Tr. at 36:7–21, 87:5–9).

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4 IMMUNOGEN, INC. v. HIRSHFELD

6-9, 11, and 12,[2] respectively, and a maytansinoid, 

and 

wherein the immunoconjugate is administered at a 

dose of 6 milligrams (mg) per kilogram (kg) of adjusted ideal body weight (AIBW) of the patient.

The ’809 Application defines AIBW as “a size descriptor 

that accounts for sex, total body weight, and height.” ’809 

Application at [0071]. It defines ideal body weight (“IBW”), 

which is used to calculate AIBW, as “a size descriptor that 

is unrelated to total body weight,” as it is “an estimate of 

weight corrected for sex and height, and optionally frame 

size.” Id. at [0069]. The application further discloses that 

IBW and AIBW “are discussed in more detail in Green and 

Duffull, British Journal of Clinical Pharmacology 58: 119-

133 (2004)” (“Green”), which it incorporates by reference. 

Id. at [0072]. Green discloses several methods for calculating IBW and lists correction factors, each specific to a different drug, that can be used to adjust IBW to AIBW.

The AIBW and IBW definitions each includes a formula, introduced by the phrase “for example,” for calculating the respective values. These “example” formulas are 

reproduced in Example 4, which relates to dosing 

IMGN853, i.e., mirvetuximab. As described in both the definitions and Example 4, AIBW is calculated as the patient’s 

IBW plus 0.4 times their total (actual) body weight in kg 

minus their IBW. Id. at [0069], [0200]. For males, IBW is 

calculated as 0.9 times their height in centimeters minus 

88; for females, IBW is calculated as 0.9 times their height 

in centimeters minus 92. Id. at [0071], [0200]. The equations are reproduced below:

2 The claimed “SEQ ID Nos” and other recited features identify the immunoconjugate as IMGN853, which is 

also known as mirvetuximab.

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IMMUNOGEN, INC. v. HIRSHFELD 5

AIBW = IBW + 0.4(Actual weight in kg – IBW)

IBW (male) = 0.9H – 88

IBW (female) = 0.9H – 92

The ’809 Application does not identify any other formulas for calculating AIBW or IBW. The “0.4” value in the 

AIBW formula is a specific correction factor for mirvetuximab, and is the only one presented in the ’809 Application.

DISCUSSION

Summary judgment is appropriate when, drawing all 

justifiable inferences in favor of the non-moving party, 

there exists no genuine issue of material fact and the moving party is entitled to judgment as a matter of law. See

Fed. R. Civ. P. 56(c); Anderson v. Liberty Lobby, Inc., 477 

U.S. 242, 247–48 (1986). We review a district court’s summary judgment determination under the law of the regional circuit, see Syngenta Crop Prot., LLC v. Willowood, 

LLC, 944 F.3d 1344, 1355 (Fed. Cir. 2019), which, here, is 

the Fourth Circuit. “The Fourth Circuit reviews the grant 

of a motion for summary judgment de novo, viewing all evidence in the light most favorable to the non-moving party.” 

Id. (citing cases).

Indefiniteness and obviousness are both issues of law 

that may rely on underlying factual findings, such as the 

knowledge, level, or understanding of those skilled in the 

art. See BASF Corp. v. Johnson Matthey Inc., 875 F.3d 

1360, 1365 (Fed. Cir. 2017) (indefiniteness); Teva Pharms. 

USA, Inc. v. Sandoz, Inc., 789 F.3d 1335, 1342 (Fed. Cir. 

2015) (same); Acorda Therapeutics, Inc. v. Roxane Lab’ys, 

Inc., 903 F.3d 1310, 1328 (Fed. Cir. 2018) (obviousness). 

Obviousness may also rely on factual findings regarding 

motivation to combine, reasonable expectation of success, 

and secondary considerations of nonobviousness. Acorda, 

903 F.3d at 1328.

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6 IMMUNOGEN, INC. v. HIRSHFELD

I

Although neither the examiner nor the Board rejected 

the claims of the ’809 Application for indefiniteness, the 

USPTO (as permitted by statute) argued in the § 145 action 

that the term “AIBW” is indefinite. The district court 

agreed, concluding that the ’809 Application fails to define 

IBW or AIBW in such a way that a skilled artisan would be 

informed, with reasonable certainty, as to the scope of the 

invention.3 ImmunoGen, 523 F. Supp. 3d at 787, 799.

For support, the district court relies mainly on the definitions section of the ’809 Application. In the district 

court’s view, the “for example” language preceding the 

AIBW formula “makes clear that there are multiple ways 

to calculate AIBW,” thereby “leav[ing] a skilled artisan to 

wonder or to guess whether the formula provided is the 

only one covered by the ’809 Application.” Id. at 787. This 

supposed uncertainty is compounded by the “for example” 

accompanying the IBW formula; the disclosure that IBW 

corrects “for sex and height, and optionally frame size”;

and the incorporation of Green. Id. Although Example 4 of 

the ’809 Application discloses dosing mirvetuximab using 

the same IBW and AIBW formulas provided in the definitions section, the district court declined to read Example 4 

as “limit[ing] the scope of the claims.” Id. at 788. The district court likewise declined to consider expert testimony 

as to whether a skilled artisan reviewing the ’809 Application would understand which AIBW formula to use, 

3 As dictated by the Supreme Court, “a patent is invalid for indefiniteness if its claims, read in light of the 

specification delineating the patent, and the prosecution 

history, fail to inform, with reasonable certainty, those 

skilled in the art about the scope of the invention.” Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 901 

(2014). The district court applied this standard in its analysis. See, e.g., ImmunoGen, 523 F. Supp. 3d at 786, 787. 

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IMMUNOGEN, INC. v. HIRSHFELD 7

characterizing the experts’ disagreement as nothing more 

than an “attempt[] to create a factual dispute” in a situation where “[t]he undisputed, intrinsic evidence demonstrates that the term AIBW . . . is indefinite.” Id.

Our review of the evidence, however, reveals that the 

underlying material factual findings are far from undisputed. For example, the district court found that the ’809 

Application “provides no limiting or defining guidance [to a 

skilled artisan] on the calculation of AIBW.” ImmunoGen, 

523 F. Supp. 3d at 787. Similarly, the district court found 

that the ’809 Application discloses multiple formulas for 

calculating AIBW. Id. at 787–88. While the district court is 

correct that the definition section incorporates Green in its 

entirety and identifies the recited AIBW and IBW formulas 

as “example[s],” ImmunoGen identified other intrinsic evidence a skilled artisan would consider in determining the 

scope of the claims, including that: (1) the claims and specification are drawn to a specific dosing regimen for a specific immunoconjugate, which is significant in light of 

expert testimony that the correction factor used to calculate AIBW is drug-specific;4 (2) Example 4 describes dosing 

mirvetuximab in accordance with the claimed method and 

uses the same AIBW and IBW formulas disclosed in the 

definitions section;5 and (3) during the prosecution of the 

4 See, e.g., J.A. 9985–86, 10059 (Figg Dep. Tr. at 

29:17–30:4, 103:2–6); J.A. 10225–26 (Figg Opening Rpt., 

¶ 146); J.A. 10368–69, 10370 (Shah Reply Rpt., ¶¶ 11–12, 

15).

5 The district court incorrectly concluded that Example 4 plays no role in the indefiniteness inquiry. See, e.g., 

Interval Licensing LLC v. AOL, Inc., 766 F.3d 1364, 1373 

(Fed. Cir. 2014) (“We recognize that a patent which defines 

a claim phrase through examples may satisfy the definiteness requirement.”); Enzo Biochem, Inc. v. Applera Corp., 

599 F.3d 1325, 1336 (Fed. Cir. 2010) (holding that the 

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8 IMMUNOGEN, INC. v. HIRSHFELD

’809 Application, the USPTO never disputed the definiteness, or gave any indication it failed to understand the 

meaning, of the now-allegedly indefinite term.6 ImmunoGen also presented extrinsic evidence regarding the 

knowledge of a skilled artisan. For instance, both parties’ 

experts testified that AIBW dosing involves drug-specific 

formulas and correction factors.7 This is confirmed by 

Green, which is incorporated into the ’809 Application and 

identifies drug-specific correction factors for use in calculating AIBW.8 When we view this evidence in the light 

most favorable to ImmunoGen—as we must in our review—we conclude that there are still disputed questions 

of material fact and summary judgment is therefore inappropriate.

II

The district court also held that the pending claims 

would have been obvious, concluding that the prior art 

taught every element of the pending claims, ImmunoGen, 

523 F. Supp. 3d at 792–93; that a skilled artisan would 

have been motivated to use AIBW dosing to address the 

ocular toxicity problems associated with mirvetuximab 

with a reasonable expectation of success, id. at 793–95; and 

phrase “not interfering substantially” is sufficiently definite because a skilled artisan could use “the examples in 

the specification to determine whether interference with 

hybridization is substantial”). 6 See, e.g., J.A. 11007 (Shah Opening Rpt., ¶¶ 197–

200); J.A. 10369–70 (Shah Reply Rpt., ¶¶ 13–14); see also 

J.A. 10899–900.

7 See, e.g., J.A. 9985–86, 10059 (Figg Dep. Tr. at 

29:17–30:4, 103:2–6); J.A. 10225–26 (Figg Opening Rpt., 

¶¶ 144, 146); J.A. 10368–69 (Shah Reply Rpt., ¶¶ 11–12).

8 J.A. 4445; see also J.A. 10225–26 (Figg Opening 

Rpt., ¶ 146).

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IMMUNOGEN, INC. v. HIRSHFELD 9

that ImmunoGen’s secondary considerations were unpersuasive, id. at 795–798.

In reaching this conclusion, the district court improperly resolved a number of factual findings against ImmunoGen. For example, the district court found that “ocular 

toxicity was a known negative effect of [immunoconjugates]

like IMGN853.” Id. at 793. But the expert testimony on 

which the district court relies does not directly support that 

statement. See id. at 793, n.40. Further, ImmunoGen presented evidence that (1) ocular toxicity is not well-understood;9 (2) immunoconjugates have unique 

pharmacokinetic characteristics, making it difficult to generalize pharmacological effects;10 (3) it was not known that 

mirvetuximab would cause ocular toxicity;11 and (4) published results for Phase 1 testing of mirvetuximab reported 

no study drug-related serious adverse events or dose-limiting toxicity.12 As another example, the district court concluded, based on statements made in International 

Published Application Nos. WO 2011/106528 (“Ab ’528”) 

and WO 2012/135675 (“Carrigan ’675”), that “dosing of 

IMGN853 could ‘easily’ be determined.” ImmunoGen, 523 

F. Supp. 3d at 795 (quoting Carrigan ’675); see also id. at 

781 (quoting Ab ’528). ImmunoGen’s experts, however, testified that the contested statements relate to dosing in the 

context of treating patients, not in the context of determining a safe and effective dose in drug development, and that 

9 See, e.g., J.A. 10095–96 (Figg Dep. Tr. at 139:7–

140:5); J.A. 11028 (Shah Opening Rpt., ¶ 235); J.A. 9595, 

9597 (Tolcher Opening Rpt., ¶¶ 34, 39).

10 See, e.g., J.A. 9595 (Tolcher Opening Rpt., ¶ 34); 

J.A. 10980–81 (Shah Opening Rpt., ¶ 50).

11 See, e.g., J.A. 9995, 10021, 10024 (Figg Dep. Tr. at 

39:6–14, 65:16–20, 68:13–22); J.A. 9941–45 (Resps. to RFA 

Nos. 64–74). 12 See, e.g., J.A. 9541.

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10 IMMUNOGEN, INC. v. HIRSHFELD

determining a safe and effective dose for immunoconjugates is difficult.13 Similarly, the district court found that 

switching “from 6 mg/kg of [TBW] dosing to 6 mg/kg AIBW 

dosing does not significantly change the dose for patients 

who are not significantly overweight or underweight,” id.

at 792–93, even though the ’809 Application and other evidence show that this switch to AIBW dosing reduced adverse ocular events in Phase 1 clinical trials.14

For each of these examples, the district court erred in 

concluding that there is no disputed question of material 

fact. This error repeats across its other factual findings, including those relating to motivation to combine, reasonable 

expectation of success, and secondary considerations.

CONCLUSION

For the reasons stated above, we hold that the district 

court erred in granting summary judgment. We therefore 

vacate the district court’s determination that the pending 

claims of the ’809 Application are indefinite and would 

have been obvious, and remand for proceedings consistent 

with this opinion.

VACATED AND REMANDED

COSTS

No costs.

13 See, e.g., J.A. 9612 (Tolcher Opening Rpt., ¶ 106); 

J.A. 10521–25 (Shah Dep. Tr. at 117:15–121:19); J.A. 

10980–81 (Shah Opening Rpt., ¶ 50); J.A. 9595 (Tolcher 

Opening Rpt., ¶ 34). 14 See, e.g., ’809 Application, Example 4; J.A. 11030–

31 (Shah Opening Rpt., ¶ 239).

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