UNITED STATES DISTRICT COURT 

FOR THE DISTRICT OF COLUMBIA

AMGEN INC.,

Plaintiff,

v.

ERIC D. HARGAN, Acting Secretary, 

Department of Health and Human Services, et 

al.,

Defendants,

and

TEVA PHARMACEUTICALS USA, INC., 

et al.,

Intervenor-Defendants.

Civil Action No. 17-1006 (RDM)

MEMORANDUM OPINION AND ORDER

To encourage pharmaceutical companies to study the safety and effectiveness of pediatric 

uses of drugs approved for adults, the Federal Food, Drug, and Cosmetic Act (“FFDCA”) grants 

six months of “pediatric exclusivity” to the sponsor of a brand-name drug if the sponsor conducts 

studies that “fairly respond” to a “written request” from the Food and Drug Administration 

(“FDA”). 21 U.S.C. § 355a(d)(4). At the urging of Plaintiff Amgen Inc., the FDA issued a 

written request asking that Amgen conduct pediatric studies of its drug Sensipar (cinacalcet 

hydrochloride), and Amgen endeavored to fulfill the request. Ultimately, however, the FDA 

found that Amgen had failed to complete a study on the safety of cinacalcet hydrochloride in 

children ages 28 days to < 6 years and concluded that Amgen’s studies did not “fairly respond” 

to the written request. The FDA, accordingly, denied Amgen’s request for pediatric exclusivity. 
2

Subsequently, the FDA denied both Amgen’s request for reconsideration and its appeal of that 

decision.

Amgen challenges the FDA’s decision as well as the agency’s underlying interpretation 

of the “fairly respond” requirement. The matter is now before the Court on Amgen’s motion for 

summary judgment, Dkt. 60, and cross-motions for summary judgment filed by the FDA, Dkt. 

65, and four intervenor-defendants, Dkt. 63. For the reasons that follow, the Court will DENY 

in part and GRANT in part Amgen’s motion and will DENY in part and GRANT in part the 

FDA’s and the intervenor-defendants’ cross-motions for summary judgment.

I. BACKGROUND

A. Statutory Background

A manufacturer seeking to market a new drug in the United States must first obtain 

approval from the FDA. The approval process is both time-consuming and expensive. Among 

other things, the applicant—or “sponsor”—must submit a new drug application (“NDA”) 

containing the extensive data and information necessary to demonstrate that the new—or 

“pioneer”—drug is “safe” and “effective,” 21 U.S.C. § 355(b)(1), as well as a “certification” 

relating to each patent that claims the drug or a use of the drug, 21 U.S.C. § 355(b)(2). 

The Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98–

417, 98 Stat. 1585—popularly known as the Hatch-Waxman Act—created an alternative path for 

manufacturers of generic drugs. Instead of submitting its own clinical data on safety and 

efficacy, a generic manufacturer may submit an abbreviated new drug application (“ANDA”)

showing that the generic version of the drug contains the same active ingredient as the pioneer 

drug and is “bioequivalent” to that drug. 21 U.S.C. § 355(j); see AstraZeneca Pharm. LP v. 

FDA, 713 F.3d 1134, 1136 (D.C. Cir. 2013) (“ANDAs need not include new clinical studies 
3

demonstrating . . . safety or efficacy, but must propose the same basic labeling as approved for 

the pioneer drug.”). In creating this shortcut, Congress sought to encourage “the development of 

generic drugs to increase competition and lower prices.” Amarin Pharm. Ireland Ltd. v. FDA, 

106 F. Supp. 3d 196, 198 (D.D.C. 2015). But, at the same time, Congress recognized that it 

needed to maintain “incentives for pharmaceutical companies to invest in innovation and the 

creation of new drugs.” Id. Accordingly, Congress “provided increased intellectual property 

rights and periods of market exclusivity for those pioneer manufacturers that invent new drugs.” 

Id.; see also 21 U.S.C. § 355(j)(5)(F); AstraZeneca, 713 F.3d at 1136. After the period of 

marketing exclusivity ends, however, the FDA may ordinarily approve ANDAs, thus authorizing 

the marketing of competing, generic versions of the pioneer drug. AstraZeneca, 713 F.3d at 

1136; see 21 U.S.C. § 355(j).

Although this statutory scheme proved successful in encouraging generic competition 

while maintaining the impetus to innovate, it failed to provide sufficient incentives for drug 

companies to conduct research on the effects of new drugs on children. In 1997, Congress found 

that the pharmaceutical industry had “studied and labeled for use in children” only a small 

portion of the drugs on the market, even though “children suffer from many of the same diseases 

as adults and are often treated with the same medicines.” S. Rep. No. 107–79, at 3–4 (2001). 

After looking for the cause of this lack of pediatric research, Congress concluded that “there 

[was] little incentive for drug sponsors to perform studies for medications which they intend to 

market primarily for adults and [the] use [of which] in children is expected to generate little 

additional revenue.” Id. at 4 (quoting S. Rep. No. 104–284 (1996)). The absence of information 

on pediatric drug safety and efficacy, moreover, exposed children to a number of unique risks:

Dosing children based merely on their lower weight is often imprecise, since their 

bodies can metabolize medicines differently than adults. Some drugs may have 
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different adverse side effects or toxicities in children than in adults, so estimating 

dosages for children from dosages found to be safe and effective in adults may not 

be appropriate. The lack of pediatric studies and labeling information may lead to 

unintended medical errors and place children at risk of being under-dosed or overdosed with medication. The lack of age-appropriate formulations (e.g., liquid form) 

can also make it difficult to give children and infants prescribed amounts of a 

needed medication.

Id. at 3. 

To address this problem, Congress enacted a “pediatric exclusivity” statute. See Food 

and Drug Administration Modernization Act of 1997, Pub. L. No. 105–115, § 111, 111 Stat. 

2296, 2305–09; Best Pharmaceuticals for Children Act, Pub. L. No. 107–109, 115 Stat. 1408 

(2002); see also Mylan Labs., Inc. v. Thompson, 389 F.3d 1272, 1276 (D.C. Cir. 2004). Under 

that law, a drug sponsor that receives “pediatric exclusivity” is entitled to an additional six 

months of market exclusivity. AR 1390. This protection, moreover, is sweeping; it applies to all 

“products containing the active moiety that has existing patent protection or exclusivity,”1 and it 

applies both to patent rights and to the FDA’s authority to approve ANDAs for competing 

products. Id.

Five events must occur for a sponsor to qualify for pediatric exclusivity: (1) the FDA 

must determine “that information relating to the use of [the] drug in the pediatric population may 

produce health benefits in that population;” (2) the FDA must make a “written request for 

pediatric studies;” (3) the applicant must agree to that request; (4) the studies must be 

“completed using appropriate formulations for each age group for which the study is requested 

within [the specified] timeframe;” and—most importantly for present purposes—(5) the reports 

from those studies must be “submitted [to] and accepted” by the FDA. 21 U.S.C. § 355a(b)(1) 

 1

 An “active moiety” is “the molecule or ion . . . responsible for the physiological or 

pharmacological action of the drug substance.” 21 C.F.R. § 314.3(b); see Amarin Pharm., 106 F. 

Supp. 3d at 199.
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(emphasis added). A sponsor may ask the FDA to issue a written request by filing “a proposed 

pediatric study request” (“PPSR”). 21 U.S.C. § 355a(d)(3). Before issuing the written request, 

the FDA must consult with the sponsor, 21 U.S.C. § 355a(d)(1)(A), and submit the request for 

review by the Pediatric Review Committee, 21 U.S.C. § 355a(f)(1), (2). That committee 

includes experts in, among other fields, pediatrics, biopharmacology, chemistry, and “the 

appropriate expertise pertaining to the pediatric product under review.” 21 U.S.C. § 355d. 

When issued, the written request asks the sponsor to “conduct pediatric studies” within a certain 

timeframe and to “propose pediatric labeling resulting from such studies.” 21 U.S.C. 

§ 355a(d)(1)(A).

The written request “serves as a yardstick against which the sponsor’s eligibility for 

pediatric exclusivity is later measured.” Dkt. 65-1 at 16. As the FDA explains, “[g]iven the 

breadth of the benefit available to sponsors who qualify for pediatric exclusivity, the agency 

generally asks for a full range of studies designed to provide meaningful information regarding 

use of the drug in all of the pediatric populations in which the drug is likely to be used.” Id. at 

15–16. The written request also includes “specific details regarding study design and endpoints, 

[the] number of patients to be studied, and study duration.” Id. at 16.

After the sponsor completes the studies and submits its reports, the FDA is required to 

decide within 180 days whether to “accept or reject such reports.” 21 U.S.C. § 355a(d)(4). The 

FDA must accept the reports if the sponsor’s studies satisfy the three exclusive conditions set 

forth in the statute. In the words of the statute:

The Secretary’s only responsibility in accepting or rejecting the reports shall be to 

determine, within the 180-day period, whether the studies [1] fairly respond to the 

written request, [2] have been conducted in accordance with commonly accepted 

scientific principles and protocols, and [3] have been reported in accordance with 

the requirements of the Secretary for filing.
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Id. (emphasis added). The Pediatric Review Committee may review the studies for purposes of 

making a recommendation on whether the FDA should accept or reject the reports, but it is not 

required to do so. 21 U.S.C. § 355a(f)(3).

B. Regulatory Background

This case turns on the meaning of the “fairly respond” requirement, and, it is fair to say, 

the FDA’s approach to this statutory language has “[e]volv[ed]” over the years. Dkt. 60-1 at 13. 

Prior to 2001, the FDA apparently required that the sponsor satisfy each and every term of the 

written request. In Merck & Co. v. FDA, 148 F. Supp. 2d 27 (D.D.C. 2001), a drug sponsor 

challenged that interpretation after the FDA denied its request for pediatric exclusivity. Id. at 30. 

Judge Robertson concluded that denying pediatric exclusivity “for failure to meet a single term 

of a written request would not be in accordance” with the statute. Id. The statute, he explained, 

“plainly does not require compliance with every single provision of a written request, but 

requires only that a pediatric study ‘fairly respond’ to a written request.” Id. The Court, 

accordingly, extended its earlier temporary restraining order, which had “stayed the effectiveness 

. . . of the FDA’s refusal” of pediatric exclusivity. Id. at 31.

The FDA’s most recent interpretation of the statute is set forth in a letter decision issued 

by the Deputy Director for Clinical Science, Center for Drug Evaluation and Research on August 

2, 2017, resolving Amgen’s administrative appeal. See AR 1632–50. Under the interpretation

set forth in that letter, the “fairly respond” requirement can be satisfied in two ways. First, 

“[w]hen a sponsor meets the terms” of the written request, “the resulting studies” will “fairly 

respond” to the request because “studies that are carried out in accordance with the trial’s plans 

and objectives, as expressed in the [written request], will generally satisfy the statutory goal of 

obtaining pediatric use information.” AR 1637. Neither party disputes this aspect of the FDA’s 

interpretation. The parties’ disagreement, instead, centers on the second prong of the test. Under 
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that prong, even where “specific terms” of the written request are not met, the FDA will 

nonetheless “generally consider the sponsor’s studies to have ‘fairly responded’” to the written 

request if the agency, “apply[ing] its scientific expertise,” determines that the underlying 

“objectives of the [written request] have . . . been met.” Id. That is, the studies will be accepted 

if the FDA determines that the studies yielded information that is “clinically meaningful across 

all age groups and uses cited in the” written request. Id.

C. Factual Background

In March 2004, the FDA approved Amgen’s drug Sensipar, or cinacalcet hydrochloride,

for secondary hyperparathyroidism (“HPT”) in adult patients with chronic kidney disease on 

dialysis, hypercalcemia in adult patients with parathyroid carcinoma, and hypercalcemia in adult 

patients with primary HPT who are unable to undergo parathyroidectomy. AR 1403. Several of 

Amgen’s patents claim Sensipar, one of which expires on March 8, 2018. Dkt. 65-1 at 17.

Amgen, believing that there was “an unmet medical need for the treatment of secondary 

HPT” in children, submitted a Proposed Pediatric Study Request to the FDA in May 2007. AR 

18, 38–42. At that time, cinacalcet’s “safety [and] effectiveness in pediatric patients had not 

been established.” Dkt. 65-1 at 17 (citing AR 14). Amgen, then, submitted a new Proposed 

Pediatric Study Request in December 2009, stressing that there was a need for pediatric studies 

because cinacalcet was “already being used off-label in a significant portion of the pediatric 

dialysis patient population.” AR 1633–34. In May 2010, after “several years of discussions and 

a pre-clinical study,” Dkt. 60-1 at 14, the FDA issued a written request to Amgen, see AR 647. 

As the agency explained, pediatric studies on cinacalcet were necessary because its efficacy in 

adults “cannot be extrapolated to the pediatric population”: secondary HPT progresses 

differently in children, and cinacalcet poses unique risks to pediatric patients, whose “skeletal 
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and vascular system[s]” are still developing. AR 648. The written request, accordingly, 

proposed that Amgen conduct two pediatric studies on “the potential use of cinacalcet 

hydrochloride in the treatment of secondary hyperparathyroidism” in children “with chronic 

kidney disease . . . receiving dialysis.” AR 647. The objective of the written request was to 

obtain information on cinacalcet’s efficacy, safety, and tolerability in pediatric patients, 

including “pediatric patients ages 28 days to < 6 years.” AR 647–48.

Over the next several years, the written request was amended five times to relax the study 

parameters, reduce the scope of the studies, or expand the ways in which the requested 

information could be obtained. See AR 730–48, 755–68, 990–1007, 1035–51, 1076–90; see also 

Dkt. 60-1 at 14–15; Dkt. 65-1 at 18–19. The final—and operative—version of the written 

request asked Amgen to complete four clinical studies:

Study 1: A single dose [pharmacokinetics/pharmacodynamics (“PK/PD”)] study in 

pediatric patients ages 28 days to < 6 years with chronic kidney disease and 

secondary hyperparathyroidism receiving dialysis.

Study 2: A 30-week, randomized, double-blind, placebo-controlled, safety and 

efficacy study with a 30-week, open-label, safety extension in pediatric patients 

ages 6 years to < 18 years with chronic kidney disease and secondary 

hyperparathyroidism receiving dialysis. This study will include an assessment of 

pharmacokinetic (PK) parameters using a sparse sampling design. Study 2 has been 

terminated early and will be analyzed with available data.

Study 3: A 26-week or time-until-transplantation (whichever comes first), openlabel, safety study in pediatric patients ages 28 days to < 6 years. . . .

Study 4: A 20-week, randomized, open-label, controlled study in pediatric subjects 

between the ages of 6 and < 18 years, with secondary hyperparathyroidism and 

chronic kidney disease who are receiving either hemodialysis or peritoneal dialysis.

AR 1080 (emphasis added). Although Study 1 and Study 3 both involved pediatric patients ages 

28 days to < 6 years, they focused on different questions. Study 1 examined cinacalcet’s 

pharmacokinetics (the drug’s “movement . . . within the body” such as “absorption, distribution, 

[and] metabolism”) and pharmacodynamics (“the characteristics of the action of” the drug). Dkt. 
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60-1 at 15 n.4 (internal quotation marks and citation omitted). Study 3, in contrast, focused on 

the drug’s safety in the youngest pediatric patients. Compared to Study 2, which also examined 

safety but in older pediatric patients, Study 3 was “shorter, smaller[,] [and] of limited scope” 

with a minimum of only 15 completers. Dkt. 65-1 at 19–20; see AR 1063. For a variety of 

reasons, Amgen struggled to locate an adequate number of patients for Study 3, AR 664–66, but 

eventually enrolled 18, AR 1159.

In December 2012, a patient enrolled in Study 2 died. AR 840. Following standard 

protocol, the FDA issued a partial clinical hold, or a temporary suspension, on further testing on 

pediatric patients with secondary HPT. Id. While the hold was in effect, Amgen and the agency 

discussed potential next steps. See AR 858–64. Amgen opted to continue the studies, AR 862, 

and the FDA replaced Study 2 with Study 4, AR 991–92. The hold, however, affected Amgen’s 

ability to complete Study 3. As Amgen explains, “enrolled patients were not receiving 

treatment, and five of the eight patients then[-]enrolled in Study 3 discontinued their 

participation.” Dkt. 60-1 at 17. Amgen and the FDA continued to correspond regarding 

Amgen’s efforts to complete Study 3. See AR 1391–95.

In late 2015, the FDA rejected Amgen’s request for a sixth amendment, which would 

have lowered the minimum number of completers in Study 3 from fifteen patients to four 

patients—“the number of completers in the study available at the time.” AR 1338. The agency 

“did not agree that [four] completers . . . would allow for an adequate characterization of safety 

for the intended use” and “was not willing to further amend” the written request to lower the 

study parameters to fit “the amount of data collected.” AR 1138–39. Amgen also sought a 

meeting with the FDA to discuss Study 3 and the submission of Amgen’s supplemental NDA. 

AR 1099. The FDA denied Amgen’s request, asserting that it would “not have any more 
10

discussion on” Study 3 and indicating that Amgen’s request to meet regarding Amgen’s 

supplemental NDA was premature. AR 1102. The agency eventually met with Amgen on 

September 21, 2016, “to discuss the overall cinacalcet pediatric development program.” AR 

1116.

On November 23, 2016, Amgen submitted its study reports to the FDA, requested 

pediatric exclusivity, and sought approval for a pediatric indication for Sensipar. AR 1152. The 

“only discrepancy” between Amgen’s studies and the written request was “the number of 

completers” for Study 3. AR 1159. The written request required a minimum of 15 patients; 

Amgen enrolled 18. Id. But only 11 patients exceeded 12 weeks of treatment, and even fewer—

just 4 patients—completed the full 26-week study. Id. Nevertheless, Amgen reported, it had 

collected “sufficient data” to “satisfy the primary objectives” of Study 3, which were to 

“evaluate the safety and tolerability” of cinacalcet in pediatric patients ages 28 days to < 6 years. 

AR 1160. In Amgen’s opinion, its data was “sufficient . . . to support an indication” in that 

pediatric population. Id.

On May 22, 2017, the FDA denied Amgen’s request for pediatric exclusivity in a letter 

decision. AR 1389–98. The agency explained that, in issuing the written request, it sought to

“characterize the risks” of using cinacalcet to treat secondary HPT in children with chronic 

kidney disease on dialysis. AR 1391. But the FDA found that it could not draw “any 

conclusions about the safety” of the drug in a key age group—patients ages 28 days to < 6 

years—because of “Amgen’s failure to provide sufficient safety data.” AR 1398. This 

conclusion was based on the “totality of safety information” Amgen provided, not merely the 

data generated in Study 3. Id. As the FDA explained, Amgen’s reports “could [have] be[en] 

considered a fair response to the [written request] as a whole” if the company’s findings in the 
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aggregate “provided an appropriate safety assessment in younger children.” Id. Instead, the 

“lack of sufficient safety data” on pediatric patients ages 28 days to < 6 years “led to the inability 

to clearly establish the safety profile of the drug . . . in accordance with [the] objectives of the 

amended [written request].” Id.

D. Procedural History

Three days after the FDA issued its decision, Amgen filed this action “to compel the 

FDA” to accept Amgen’s reports and to grant pediatric exclusivity for Sensipar. Dkt. 1 at 2

(Compl. ¶ 1). Amgen claimed that the FDA’s interpretation of “fairly respond” was contrary to 

the pediatric exclusivity statute under the Administrative Procedure Act (“APA”), 5 U.S.C. § 701

et seq., Dkt. 1 at 21–23 (Compl. ¶¶ 50–56); that its denial of pediatric exclusivity for Sensipar 

was arbitrary and capricious, id. at 29–31 (Compl. ¶¶ 76–88); and that its application of its 

standard violated Amgen’s due process rights, id. at 31 (Compl. ¶¶ 89–90). On the same day, 

Amgen moved for a temporary restraining order or preliminary injunction, arguing that it might 

“lose the full benefit of its pediatric exclusivity” absent injunctive relief. Dkt. 3 at 10. The 

Court held a hearing on Amgen’s motion on June 2, 2017. Minute Entry (June 2, 2017). 

After the hearing, however, the parties agreed that Amgen would seek reconsideration and 

administrative dispute resolution before the FDA and that the proceedings before the Court 

would be stayed. Dkt. 14. Based on the parties’ stipulation, the Court denied Amgen’s motion 

for preliminary relief as moot and stayed the case pending completion of the renewed 

administrative process. Dkt. 15.

On remand, the FDA denied both Amgen’s request for reconsideration, AR 1484, as well 

as its appeal of that decision in the FDA’s administrative dispute resolution process, AR 1632. 

During those proceedings, Amgen “pressed the same arguments it makes here”—that the FDA’s 
12

interpretation of “fairly respond” is foreclosed by the statute and that FDA’s application of that 

standard to Amgen “violated foundational principles of administrative law and due process.” 

Dkt. 60-1 at 22. In a final letter decision denying Amgen’s administrative appeal, the agency set 

forth the interpretation of “fairly respond” described above. See supra Part I.B. Applying that

standard, the FDA affirmed its earlier conclusions that Amgen’s studies did not “fairly respond”

to the written request because (1) Amgen “fail[ed] to carry out Study 3 in accordance with the 

[written request]” and (2) Amgen failed to provide “meaningful pediatric use information in 

children 28 days to < 6 years of age.” AR 1648.

The dispute then returned to this Court, where the parties jointly proposed an expedited 

briefing schedule. Dkt. 24. Before either side moved for summary judgment, four generic drug 

companies—Teva Pharmaceuticals USA, Inc., Barr Laboratories, Inc., Watson Laboratories, 

Inc., and Amneal Pharmaceuticals LLC—moved to intervene as defendants, Dkt. 26; Dkt. 33, 

and the Court granted their motions, see Minute Order (Aug. 15, 2017); Dkt. 61. In addition, 

Amgen moved to complete or supplement the administrative record with several sets of 

documents that Amgen asserted were considered by the FDA in denying Amgen pediatric 

exclusivity. Dkt. 38. The Court denied Amgen’s motion in part from the bench at a hearing held 

on September 20, 2017, and directed that the parties meet and confer regarding the remaining 

portion of Amgen’s motion. See Minute Entry (Sept. 20, 2017). After the parties were unable to 

reach an agreement, they set forth their respective positions in a further filing, Dkt. 53, and the 

Court denied the remainder of Amgen’s request, see Minute Order (Oct. 11, 2017); Dkt. 61.

Three motions are now before the Court: Amgen’s motion for summary judgment, Dkt. 

60, the FDA’s cross-motion, Dkt. 65, and the intervenor-defendants’ joint cross-motion, Dkt. 63. 

The Court held a hearing on those motions on January 11, 2018. See Minute Entry (Jan. 11, 
13

2018). Because Amgen has represented that a “key patent[] covering Sensipar” is due to expire 

on March 8, 2018, Dkt. 1 at 4–5 (Compl. ¶ 9), the Court has expedited its resolution of the 

pending motions.

II. LEGAL STANDARD

Under Federal Rule of Civil Procedure 56, summary judgment is ordinarily available if 

the movant demonstrates “that there is no genuine dispute as to any material fact” and that, based 

on the uncontested facts, “the movant is entitled to judgment as a matter of law.” Fed. R. Civ. P. 

56(a). In the unique context of a case brought under the APA, however, the district court “sit[s] 

as an appellate tribunal,” Marshall Cty. Health Care Auth. v. Shalala, 988 F.2d 1221, 1222–23 

(D.C. Cir. 1993), to decide “as a matter of law [whether] the agency action is supported by the 

administrative record and is otherwise consistent with the APA standard of review,” Coal. for 

Common Sense in Gov’t Procurement v. United States, 821 F. Supp. 2d 275, 280 (D.D.C. 2011); 

see also Citizens to Preserve Overton Park, Inc. v. Volpe, 401 U.S. 402, 415 (1971); Sw. Merch. 

Corp. v. NLRB, 53 F.3d 1334, 1341 (D.C. Cir. 1995). In short, it is the role of the administrative 

agency to “resolve factual issues” and to “arrive at a decision that is supported by the 

administrative record,” while it is the role of the district court “to determine whether or not as a 

matter of law the evidence in the administrative record permitted the agency to make the 

decision it did.” Hi-Tech Pharmacal Co. v. FDA, 587 F. Supp. 2d 13, 18 (D.D.C. 2008).

III. ANALYSIS

Amgen argues that the FDA’s decision denying it pediatric exclusivity for Sensipar is 

unlawful and must be set aside for three reasons. First, Amgen contends that the FDA’s 

interpretation of “fairly respond” “violate[s] the pediatric exclusivity statute.” Dkt. 60-1 at 25. 

Second, it argues that the FDA’s denial was arbitrary and capricious because the agency treated 
14

Amgen differently from similarly situated entities and refused to consider evidence on the 

challenges of enrolling participants in Study 3. Id. Finally, Amgen contends that the FDA’s 

application of its “fairly respond” standard to Amgen “without any notice” contravened both 

“due process and APA principles.” Id. The FDA responds that its interpretation of “fairly 

respond” is entitled to deference under Chevron, U.S.A., Inc. v. Natural Resources Defense 

Council, Inc., 467 U.S. 837 (1984); that it correctly and fairly applied the standard in rejecting 

Amgen’s studies; and that Amgen was fully aware of the FDA’s interpretation. Dkt. 65-1 at 11–

12. The Court will consider each argument in turn.

A. Statutory Claim

According to Amgen, the FDA’s interpretation of “fairly respond” is incompatible with 

the text of the pediatric exclusivity statute. Dkt. 60-1 at 25. As explained above, that 

interpretation recognizes two ways in which a sponsor’s studies may “fairly respond” to the 

written request. First, if the sponsor’s studies meet the “specific terms” of the written request, 

the studies “fairly respond” to the written request. AR 1637. Second, even if the studies deviate 

from the “specific terms” of the written request, the FDA will nonetheless conclude that they 

“fairly respond” to the written request if they yield “clinically meaningful” information “across 

all age groups and uses cited in the” written request. Id. Because all agree that Study 3 did not 

meet the “specific terms” of the FDA’s written request, the first prong of the test has no bearing 

on this case. Instead, the focus is on the second prong. It is this prong of the test that Amgen 

contends is both narrower than the statute mandates and “incompatible” with the “limited role” 

Congress accorded the FDA. Dkt. 60-1 at 26.

To determine “whether an agency’s construction of its authorizing statute is permissible,” 

the Court looks to the two-step inquiry set forth in Chevron. Safari Club Int’l v. Zinke, 878 F.3d 
15

316, 326 (D.C. Cir. 2017). The Court must first ascertain “‘whether Congress has directly 

spoken to the precise question at issue,’” and, in doing so, must employ “the ordinary tools of 

statutory construction.” City of Arlington v. FCC, 569 U.S. 290, 296 (2013) (quoting Chevron, 

467 U.S. at 842). If Congress has spoken directly to the question, that is “the end of the matter” 

because the Court—and the agency—“must give effect to the unambiguously expressed intent of 

Congress.” Chevron, 467 U.S. at 842–43. But if, instead, the statute is ambiguous, the Court 

must “defer to the agency construction so long as it is reasonable.” Safari Club, 878 F.3d at 326.

1. Chevron Step Zero

As an initial matter, Amgen disputes that the Chevron framework applies to the FDA’s 

“fairly respond” interpretation. Dkt. 60-1 at 26–30. For Chevron to govern, the agency must 

have “acted pursuant to congressionally delegated authority to make law and with the intent to 

act with the force of law.” Safari Club, 878 F.3d at 326 (citing United States v. Mead Corp., 533 

U.S. 218, 226–27, 229 (2001)); see Menkes v. U.S. Dep’t of Homeland Sec., 637 F.3d 319, 331 

(D.C. Cir. 2011). Often referred to as Chevron “step zero,” this threshold inquiry delimits the 

types of agency actions that qualify for Chevron deference. Amgen offers a number of 

arguments why the FDA’s interpretation of “fairly respond” falls outside Chevron’s ambit, but 

none are persuasive.

First, Amgen argues that Congress’s use of the adjective “only” to describe the FDA’s 

“responsibility in accepting or rejecting” a sponsor’s reports, 21 U.S.C. § 355a(d)(4), signals that 

Congress “did not intend to delegate rulemaking authority” concerning the meaning of “fairly 

respond” to the FDA, Dkt. 60-1 at 27. The statute, in relevant part, reads as follows: “[t]he 

[FDA’s] only responsibility in accepting or rejecting the reports shall be to determine . . . 

whether the studies fairly respond to the written request” and fulfill the other two statutory 
16

criteria. 21 U.S.C. § 355a(d)(4) (emphasis added). Amgen is partly correct—but only partly. It 

is correct that the word “only” “narrow[s] . . . the agency’s discretion” by “expressly limit[ing] 

what the agency can and cannot do.” Dkt. 60-1 at 27. But it is incorrect that this limitation has 

anything to do with the FDA’s authority to interpret the phrase “fairly respond.” Indeed, just the 

opposite is true. The statute accords the agency the “responsibility . . . to determine . . . whether 

the studies fairly respond to the written request.” 21 U.S.C. § 355a(d)(4) (emphasis added). 

Without construing the meaning of “fairly respond,” the FDA cannot discharge that statutory 

responsibility. It follows, moreover, that—to the extent “fairly respond” is ambiguous, which is 

the sole question presented at Chevron step one—Congress must have intended to confer 

interpretative authority on the FDA.

Second, Amgen asserts that “a court does not defer to an agency’s interpretation under 

Chevron” if the matter does not “implicate[] the agency’s unique technical or scientific 

expertise.” Dkt. 60-1 at 27. This misunderstands the relevance of expertise to the Chevron

framework. Expertise can come into play at two levels. First, Congress might opt to delegate 

interpretive power to an agency because, in Congress’s judgment, the agency possesses valuable 

expertise. But, if it does so, the justification for judicial deference to an agency’s interpretation 

is the congressional delegation itself, not the Court’s assessment of the agency’s expertise. As 

the Supreme Court explained in City of Arlington v. FCC, 569 U.S. 290 (2013):

Chevron is rooted in a background presumption of congressional intent: namely, 

“that Congress, when it left ambiguity in a statute” administered by an agency, 

“understood that the ambiguity would be resolved, first and foremost, by the 

agency, and desired the agency (rather than the courts) to possess whatever degree 

of discretion the ambiguity allows.”

Id. at 296 (quoting Smiley v. Citibank (South Dakota), N.A., 517 U.S. 735, 740–41 (1996)); see 

also Mead, 533 U.S. at 229 (explaining that when “circumstances” indicate that Congress 

“expect[ed] the agency” to “speak with the force of law” in addressing a statutory ambiguity, “a 
17

reviewing court has no business rejecting an agency’s exercise of its generally conferred 

authority to resolve [that] statutory ambiguity”); AKM LLC v. Sec’y of Labor, 675 F.3d 752, 765 

(D.C. Cir. 2012) (Brown, J., concurring) (“It is by Congress’s ‘delegation of authority to the 

agency to elucidate a specific provision of the statute’ that an agency’s interpretation is deserving 

of the court’s deference.” (quoting Chevron, 467 U.S. at 843–44)); Antonin Scalia, Judicial 

Deference to Administrative Interpretations of Law, 1989 Duke L.J. 511, 514 (“If it is . . . the 

constitutional duty of the courts to say what the law is, we must search for something beyond 

relative competence as a basis for ignoring that principle when agency action is at issue.”). In 

short, the Chevron framework “is premised on the theory that a statute’s ambiguity constitutes an 

implicit delegation from Congress to the agency to fill in the statutory gaps,” FDA v. Brown & 

Williamson Tobacco Corp., 529 U.S. 120, 159 (2000), and that rationale stands regardless of 

whether filling the relevant gap requires a PhD. Second, courts may at times accord heightened

deference to the scientific or technical expertise of an agency. See A.L. Pharma, Inc. v. Shalala, 

62 F.3d 1484, 1490 (D.C. Cir. 1995); Sanofi-Agentis U.S. LLC v. FDA, 842 F. Supp. 2d 195, 211 

(D.D.C. 2012). But that does not mean that Chevron is inapplicable in other cases. Amgen cites 

no authority for its sweeping contention that Chevron applies only in cases that require 

specialized expertise, nor is the Court aware of any. To the contrary, Chevron is commonly 

applied in cases involving no greater call for expertise than at issue here. See, e.g., City of 

Arlington, 569 U.S. at 294, 301.

Amgen relies on King v. Burwell, 135 S. Ct. 2480 (2015), but that case is fully consistent 

with the delegation-based justification for Chevron. In King, Chevron did not apply because the 

“extraordinary” nature of the case, which implicated “billions of dollars” in government 

spending and “millions of people,” suggested that Congress did not intend to delegate 
18

interpretive authority to the agency. Id. at 2488–89. Although the Court noted that it was 

“especially unlikely” that Congress “would have delegated” the power to decide such “a question 

of deep ‘economic and political significance’ that [was] central to th[e] statutory scheme,” id.

(citation omitted), to an agency that lacked any “expertise” in crafting the relevant type of policy, 

this reasoning serves only to reaffirm that delegation—not expertise—is what matters. Here, in 

contrast to King, Amgen offers no plausible reason to doubt that Congress intended to delegate 

interpretive authority to the FDA.

Third, Amgen argues that the FDA’s interpretation of “fairly respond” lacks “the 

traditional hallmarks of deference.” Dkt. 60-1 at 28; see Mead, 533 U.S. at 227. According to 

Amgen, the FDA’s pediatric exclusivity determinations have been “ad hoc,” “freewheeling,” and 

non-public. Dkt. 60-1 at 28. As a result, Amgen concludes, Chevron does not cover the 

agency’s decision in this case, which was set forth in the letter decisions denying Amgen 

pediatric exclusivity. Id. The Court is, once again, unpersuaded. The D.C. Circuit has expressly 

held that “the FDA’s interpretations of the [Federal] Food, Drug, and Cosmetic Act adopted in 

letter rulings” are to be “evaluate[d] . . . under the familiar two-part Chevron framework.” Teva 

Pharm. USA, Inc. v. Sebelius, 595 F.3d 1303, 1315 (D.C. Cir. 2010); see also Mylan Labs., 389 

F.3d at 1279–80; Abbott Labs. v. Young, 920 F.2d 984, 986–89 (D.C. Cir. 1990); Mylan Pharm., 

Inc. v. Sebelius, 856 F. Supp. 2d 196, 208 (D.D.C. 2012); Hi-Tech Pharmacal, 587 F. Supp. 2d 

at 19. As the FDA explains, pediatric exclusivity decisions “are generally unpublished” because 

they “often contain confidential commercial . . . information.” Dkt. 65-1 at 34. But their nonpublic nature does not deprive these determinations of “those ‘relatively formal administrative 

procedure[s]’ that ‘tend[] to foster the fairness and deliberation that should underlie a 

pronouncement’ of legal interpretation.” Fogo De Chao (Holdings) Inc. v. U.S. Dep’t of 
19

Homeland Sec., 769 F.3d 1127, 1137 (D.C. Cir. 2014) (quoting Mead, 533 U.S. at 230). This 

case, moreover, highlights the “relative formal[ity]” of the FDA’s “administrative procedure[s],” 

id.; the FDA issued three detailed letter decisions setting forth its analysis of the statute and the 

relevant facts, and it allowed Amgen to be heard before the agency issued its original decision, 

its reconsideration decision, and its appeal decision, see AR 1389–99; AR 1483–96; AR 1632–

50.

Finally, Amgen invokes Encino Motorcars, LLC v. Navarro, 136 S. Ct. 2117 (2016), for 

the proposition that “Chevron deference is not warranted where the regulation is ‘procedurally 

defective’—that is, where the agency errs by failing to follow the correct procedures in issuing 

the regulation.” Id. at 2125 (quoting Mead, 553 U.S. at 227); see Dkt. 60-1 at 28–29. Amgen 

argues that the FDA’s construction of the statute is “procedurally unsound” because it was not 

announced publicly and because the agency did not provide a “reasoned explanation” for its 

“unexplained about-face” from its pre-Merck interpretation. Dkt. 60-1 at 28–29. The Court is 

unpersuaded.

The holding in Encino Motorcars was premised on the concern that “longstanding 

policies may have ‘engendered serious reliance interests that must be taken into account.’” 

Encino Motorcars, 136 S. Ct. at 2126 (quoting FCC v. Fox Television Studios, Inc., 556 U.S. 

502, 515 (2009)). But Amgen cannot claim such reliance interests. The “flip-flop” that Amgen 

apparently targets was the FDA’s change in position following this Court’s decision in Merck & 

Co. v. FDA, 148 F. Supp. 2d 27 (D.D.C. 2001). That change, however, expanded the agency’s 

interpretation of “fairly respond.” Before Merck, the FDA required sponsors to meet all the 

terms of the written requests to qualify for pediatric exclusivity, while, after Merck, the FDA has 

accepted imperfect reports of studies that nonetheless met the objectives of the written requests. 
20

See AR 1643. It is difficult to see how the FDA’s relaxation of the standard could have 

frustrated any serious reliance interest that Amgen may have had. 

The FDA’s change in position, moreover, hardly came out of the blue; it followed a 

judicial decision concluding that the FDA’s prior reading of the “fairly respond” requirement 

was “[in]consistent with the statutory standard.” Merck, 148 F. Supp. 2d at 30. And, although 

Amgen correctly notes that the FDA’s intervening decisions were not released publicly, there is 

nothing surprising in the FDA’s conclusion that studies “fairly respond” to a written request if 

they comply with its terms or meet its goals by providing “clinically meaningful” information 

across the relevant uses and age groups. Finally, Amgen’s contention that the FDA’s current 

reading of the statute constitutes “an unexplained about-face from [its] prior understanding,” 

Dkt. 60-1 at 29, is belied by the administrative record. In addressing Amgen’s arguments, the 

FDA explained the basis for its reading of the statute, and it explained that the test that it has now 

adopted is “consistent with the holding in Merck,” which requires the agency to consider the 

results of a sponsor’s studies “as a whole.” AR 1485; see also AR 1636–38.

2. Chevron Step One

Under Chevron step one, the Court “must first determine whether . . . ‘Congress has 

directly spoken to the precise question at issue.’” Vill. of Barrington v. Surface Transp. Bd., 636 

F.3d 650, 659 (D.C. Cir. 2011) (quoting Chevron, 467 U.S. at 842). This inquiry requires that 

the Court ask “whether Congress has ‘unambiguously foreclosed the agency’s statutory 

interpretation.” Id. (quoting Catawba Cty. v. EPA, 571 F.3d 20, 35 (D.C. Cir. 2009)); see also 

Animal Legal Def. Fund, Inc. v. Perdue, 872 F.3d 602, 616 (D.C. Cir. 2017) [hereinafter ALDF] 

(“We thus must determine whether the agency’s [interpretation] is unambiguously foreclosed by 

the statute.” (citation omitted)); Otsuka Pharm. Co. v. Price, 869 F.3d 987, 995 (D.C. Cir. 2017) 
21

(same). If the agency’s interpretation “violate[s] Congress’s precise instructions or exceed[s] the 

statute’s clear boundaries,” then “the agency’s interpretation is unlawful.” Vill. of Barrington, 

636 F.3d at 660.

The Court “begin[s], of course, with the statutory text.” ALDF, 872 F.3d at 616 (citing 

Maslenjak v. United States, 137 S. Ct. 1918, 1924 (2017)). The pediatric exclusivity provision

sets forth an intricate, multi-step process for determining when a sponsor’s pediatric research 

justifies a valuable, six-month extension of the sponsor’s market exclusivities and patent rights. 

The FDA, tasked with effectuating this process, occupies center stage in the statutory scheme. 

Among other duties, the agency is charged with deciding whether to “accept or reject” the 

sponsor’s “reports of [its] studies.” 21 U.S.C. § 355a(d)(4). Fulfilling this “responsibility” 

requires the FDA “to determine . . . whether the studies fairly respond to the written request.” Id. 

As noted, the agency has found that a sponsor’s study reports constitute a “fair response” if they 

either meet the specific terms of the written request or meet its objectives by yielding

“information [that] is clinically meaningful across all age groups and uses.” AR 1637.

The statute provides important guidance by specifying that the requirement can be 

satisfied by something short of perfect compliance: the sponsor need only “fairly” respond to the 

written request. See Merck, 148 F. Supp. 2d at 30–31. If perfect compliance were required, the 

adverb “fairly” would serve no purpose, and that result “would risk running headlong into the 

rule against superfluity.” Lockhart v. United States, 136 S. Ct. 958, 966 (2016). But this is 

where the text runs out. The statute does not define what constitutes a “fair” response, and, as 

the FDA argues, “fairly respond” is “an inherently ambiguous term.” Dkt. 65-1 at 30. To take 

just one source, the Oxford English Dictionary suggests that the term “fairly” has two different 
22

senses. Fairly, adv., Oxford English Dictionary (2018) [hereinafter OED].

2

 The first “relat[es] 

to amount, extent, or degree,” suggesting a more quantitative assessment. Id. Amgen’s 

preferred definitions—“moderately,” “passably,” and “reasonably well”— fall within this 

category. Dkt. 60-1 at 31; see also Fairly, Merriam-Webster Dictionary (2018) (“to a full degree 

or extent”);3 Fairly, Collins English Dictionary (2018) (“to quite a large degree”).4 The second 

sense, however, draws on a more substantive conception of the term: “[i]n a fair manner, so as to 

be fair.” OED. This sense of the word “fairly” includes definitions such as “[b]y proper or legal 

means; legitimately,” “[i]n accordance with what is right or just[;] . . . with good reason, 

rightfully,” and—perhaps most relevant here—“[i]n a proper or suitable manner; appropriately, 

fittingly.” Id. The FDA interprets the word “fairly” in a manner that draws on both senses: 

“how much of a response there was” as well as “the quality of the response.” Dkt. 65-1 at 31. 

The statute does not dictate one sense of the word “fairly” over the other, nor does it indicate 

which of the competing meanings within each sense (for instance, “moderately” versus “to a full 

degree”) Congress intended. What is clear, however, is that the FDA’s “clinically meaningful 

information” interpretation is not “unambiguously foreclosed” by the statutory text. There is no 

textual or other evidence that the statute prohibits the agency from considering the extent to 

which the data responds to the goals of the study.

Amgen offers a number of counterarguments, none of which compels a different 

conclusion. First, Amgen contends that “fairly respond” necessarily means “answer reasonably 

well,” Dkt. 60-1 at 31, and that—when combined with the limiting term “only”—this shows that 

 2

 Available at http://www.oed.com/view/Entry/67727.

3

 Available at https://www.merriam-webster.com/dictionary/fairly.

4

 Available at https://www.collinsdictionary.com/us/dictionary/english/fairly.
23

Congress unambiguously foreclosed the FDA from adopting a “results[-]oriented” standard, Dkt. 

74 at 33 (Tr. 33:10–11, :21–23). But, for the reasons explained above, the word “only” does not 

modify the phrase “fairly respond;” it merely means that the FDA should not add requirements to 

those that Congress specified. Reading the phrase “fairly respond” to mean “answer reasonably 

well,” moreover, does nothing to clarify the standard; “answer reasonably well” is just as 

ambiguous as “fairly respond.” For purposes of Chevron step one, the question is whether 

Congress left a gap for the agency to fill, and substituting the phrase “answer reasonably well” 

for “fairly respond” neither fills the existing gap nor demonstrates that the FDA’s reading of the 

statute is unambiguously foreclosed.

When asked at oral argument to describe how the FDA should “decide whether [a] 

response was reasonable,” Dkt. 74 at 21 (Tr. 21:12–14), Amgen offered that the agency must

assess reasonableness in light of “the volume of what . . . [was] put in front of the agency” as 

well as “what the sponsor did in order to achieve that data,” id. at 24 (Tr. 24:17–19). In other 

words, Amgen explained, “reasonableness includes both the extent of the data [provided] and the 

amount of the effort [undertaken].” Id. at 27 (Tr. 27:10–12). Amgen concludes that, under that

standard, it “did everything it could . . . to satisfy the terms of the [written] request,” id. at 24 (Tr. 

24:23–25), and it is therefore entitled to pediatric exclusivity. An effort-based interpretation of 

“fairly respond,” however, finds no warrant in the statutory text. The question is whether the 

study reports—not the sponsor—“fairly respond” to the written request. In other words, the 

statute focuses on the studies themselves, not the length of time the studies took, nor the number 

of attempts needed to complete the studies, nor the expenses incurred in carrying out the studies. 

An effort-based interpretation of “fairly respond” is untenable.
24

Amgen offers an additional reading of the statute, which includes a textual anchor and 

builds on the FDA’s goal-focused approach. Under this interpretation, a sponsor’s studies 

suffice if they generate any information that results in a labeling change mandated by 21 U.S.C. 

§ 355a(j). That provision provides: 

If . . . the [FDA] determines that a pediatric study . . . does or does not demonstrate 

that the drug [in question] is safe and effective, including whether such study results 

are inconclusive, in pediatric populations or subpopulations, the [FDA] shall order 

the labeling of such product to include information about the results of the study 

and a statement of the [FDA’s] determination.

Id. According to Amgen, because the results of its studies were added to the Sensipar label 

pursuant to § 355a(j), the FDA was not free to second-guess the congressional determination that 

the results were meaningful. Dkt. 60-1 at 32.

Amgen’s argument suffers from a number of flaws. First, § 355a(j)’s labeling 

requirement was enacted ten years after Congress imposed the “fairly respond” requirement, 

compare Food and Drug Administration Amendments Act, Pub. L. No. 110–85, § 502, 121 Stat. 

823, 876–90 (2007) (adding 21 U.S.C. § 355a(j)), with Food and Drug Administration 

Modernization Act, Pub. L. No. 105–115, § 111, 111 Stat. 2296, 2305–09 (1997) (adding “fairly 

respond” requirement), and there is no evidence that Congress intended § 355a(j) to amend or 

clarify the meaning of its earlier enactment. Second, the FDA has explained that it has 

interpreted § 355a(j) to require labeling changes regardless of whether the studies yielded any 

clinically meaningful results; rather, according to the FDA, § 355a(j) applies mechanically to all 

such studies. Understood in this light, Amgen’s argument proves too much. It would mean, 

among other things, that the “fairly respond” requirement is meaningless and that the FDA must 

grant pediatric exclusivity to a sponsor that is utterly unsuccessful in responding to a written 

request. At oral argument, for example, Amgen acknowledged that this argument would mean 
25

that it would have “fairly responded” to the FDA’s written request even if only “one patient” had 

completed Study 3. Dkt. 74 at 90 (Tr. 90:10–15). 

Finally, Amgen asserts that the FDA’s “clinically meaningful information” standard 

would undermine the incentive structure Congress envisioned when it provided for pediatric 

exclusivity. See Dkt. 60-1 at 34–36. This contention, however, bears more on the 

reasonableness of the FDA’s interpretation than on whether the statute “unambiguously 

forecloses” the FDA’s approach. The Court will therefore consider Amgen’s purposive 

argument at Chevron’s second step.

Because the phrase “fairly respond” is ambiguous, Chevron teaches that Congress “has 

implicitly delegated the authority” to interpret this term to the FDA. ALDF, 872 F.3d at 617. 

That conclusion is particularly apt, moreover, because—as this case demonstrates—the meaning 

attached to that phrase implicates the type of policy-laden judgment that is better left to the 

politically accountable executive branch than to the unelected judiciary. See Chevron, 467 U.S. 

at 864 (“[P]olicy arguments are more properly addressed to legislators or administrators, not to 

judges.”). Construing “fairly respond” is, in short, “precisely the type of statutory gap-filling 

that ‘involves difficult policy choices that agencies are better equipped to make than courts.’” 

ALDF, 872 F.3d at 617 (quoting Nat’l Cable & Telecomms. Ass’n v. Brand X Internet Servs., 545 

U.S. 967, 980 (2005)).

3. Chevron Step Two

The next question is whether the FDA “has reasonably explained how the permissible 

interpretation it chose is ‘rationally related to the goals of’ the statute.” Vill. of Barrington, 636 

F.3d at 665 (quoting AT&T Corp. v. Iowa Utils. Bd., 525 U.S. 366, 388 (1999)). The Court’s 

review “at this stage is ‘highly deferential.’” Id. (quoting Nat’l Rifle Ass’n of Am. v. Reno, 216 
26

F.3d 122, 137 (D.C. Cir. 2000)). But this deference is “not absolute,” Mylan Labs. Ltd. v. FDA, 

910 F. Supp. 2d 299, 306 (D.D.C. 2012), and it must give way in the absence of “reasoned 

decisionmaking,” Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 52 

(1983); see also Fox v. Clinton, 684 F.3d 67, 74–75 (D.C. Cir. 2012); Tripoli Rocketry Ass’n v. 

Bureau of Alcohol, Tobacco, Firearms, & Explosives, 437 F.3d 75, 77 (D.C. Cir. 2006).

The FDA’s explication of its “clinically meaningful information” standard expressly links

that standard to the underlying goal of the pediatric exclusivity statute. The agency’s final 

decision on Sensipar describes both the purpose of the pediatric exclusivity statute and how the 

FDA’s interpretation furthers that goal: the statute’s purpose is “to encourage [sponsors to] 

conduct . . . clinical studies that would result in a public health benefit for pediatric patients,” 

and, in particular, “to address the lack of meaningful information about pediatric uses of drugs, 

which impairs the ability of health care practitioners and pediatric patients to appropriately use 

such drugs.” AR 1636. The FDA works to achieve this goal by drafting each written request, 

with input from the Pediatric Review Committee, “to maximize the potential to elicit such 

information.” AR 1637. The FDA then assesses the study reports against the objectives of the 

written request. Id. Accordingly, even if the “specific terms of the [written request] are not 

met,” the FDA will “apply its scientific expertise to determine [whether] the objectives of the 

[written request] have nevertheless been met,” and, if so—“consistent with the goals of the . . . 

statute”—the FDA “will generally consider the sponsor’s studies to have ‘fairly responded’ to 

the [written request].” Id. (emphasis omitted).

All three of the FDA’s decisions in this matter note the significance of meaningful

labeling changes as indicia of whether the sponsor’s studies provided clinically meaningful 

information. The agency’s initial decision observed, for example, that the FDA “considers 
27

whether the submission” enables the agency “to approve pediatric labeling (including negative 

pediatric labeling) for all of the age groups and indications” cited in the written request. AR 

1391. The FDA’s reconsideration decision elaborated on this standard. See AR 1485. Because 

the FDA “draft[s] each [written request] to elicit all of the information needed for use in all 

relevant pediatric populations,” those objectives will be served where a sponsor’s studies comply 

perfectly with the written request or where the information “suffic[es] to enable the [FDA] to 

approve meaningful labeling.” Id. Finally, the FDA’s appeal decision reiterated “that the 

purpose of a [written request] is to elicit information that would . . . lead to the addition of 

pediatric use information to the drug’s labeling.” AR 1639; see also AR 1637 (noting that the 

“FDA drafts each [written request] to maximize the potential to elicit” clinically meaningful 

information, “as expressed in the drug’s labeling”). Indeed, Amgen itself stressed in its PPSR 

that “[t]he overall objective of [its] proposed program [was] inclusion of data in the Pediatric 

Use section of the label.” AR 24. 

In other words, the goal of the pediatric exclusivity statute is to elicit “information” that 

“may produce health benefits” in children. 21 U.S.C. § 355a(b)(1). The agency has determined 

that this objective is best served by an interpretation of “fairly respond” that allows the agency to 

accept a sponsor’s reports when (1) there is perfect compliance or (2) the studies generate 

“information” that “is clinically meaningful,” i.e., information that practitioners would find 

useful. AR 1637. Although this interpretation may not be the best one, it is eminently 

reasonable in light of the “the goals of the [statute]” and is “rationally related” to those 

objectives. AT&T Corp., 525 U.S. at 388.

Amgen offers three counterarguments. It first contends that the FDA’s “clinically 

meaningful information” standard goes beyond “the limited assessment Congress empowered the 
28

agency to make.” Dkt. 60-1 at 37. But, for the reasons discussed at the first step of the Chevron 

inquiry, Amgen has not offered a persuasive account of “the limited assessment” that it believes 

Congress contemplated. It is true that Congress limited the FDA to considering the requirements 

identified in the statute, but it did not limit the FDA’s authority to consider whether those

requirements were satisfied. See supra Part III.A.1. 

Second, Amgen notes that the FDA initially had only 90 days to decide whether to accept 

or reject a sponsor’s reports, and it argues that the original allotment of 90 days would not have 

afforded the FDA enough time to conduct its “clinically meaningful information” inquiry. Dkt. 

60-1 at 37 (citing 21 U.S.C. § 355a(d)(3) (2003)). Given the fact that the FDA participates in the 

ongoing process—and, indeed, formulates the written request and any amendments to it—that 

contention is far from convincing. And, the fact that Congress subsequently extended the time 

allowed for the FDA’s review, if anything, supports the conclusion that Congress did not intend 

for the decision whether to accept or reject a sponsor’s reports to be a mechanical one. 

Finally, as noted above, Amgen contends that the FDA’s interpretation is at odds with 

congressional intent because it injects “deep uncertainty into the process” and thus “radically 

undermines the terms of Congress’s bargain.” Dkt. 60-1 at 34–35. Even assuming that Amgen 

is correct that “[t]he central feature of this statutory bargain is that the sponsor knows the terms 

of th[e] bargain before it . . . decide[s] whether to conduct the pediatric studies,” Dkt. 60-1 at 34

(emphasis omitted), it is far from clear that Amgen’s reading of the statute provides greater 

certainty or predictability than the FDA’s. Under the FDA’s construction of the statute, a 

sponsor can earn six months of additional exclusivity if its studies either (1) meet the terms of

the written request or (2) yield clinically meaningful information that achieves the specified 

objectives of the written request. Either way, the sponsor’s success can be measured against the 
29

prescribed terms and goals of the written request. Under Amgen’s proposed construction of the 

statute, in contrast, the FDA would be required to assess the quantity of information provided 

and the sponsor’s effort without any specified benchmark or standard. Similarly, it is not 

obvious that Amgen’s reading of the statute is likely to yield more information about pediatric 

uses of drugs. Although Amgen might be correct that sponsors may be more likely to submit 

PPSRs to the FDA with a more forgiving interpretation of the statute, they may also be less 

likely to complete their studies in the manner contemplated by the written requests. It is not, of 

course, the Court’s role to decide whether Amgen’s account of the relevant incentives is more or 

less compelling than the FDA’s, but only to determine whether the FDA’s understanding of the 

statutory scheme is a reasonable one. For the reasons explained above, the Court concludes that 

it is.

Because the term “fairly respond” is ambiguous and because the FDA’s interpretation of 

that term is reasonable, the Court must defer to the FDA’s statutory construction.

B. Arbitrary and Capricious Claim

Under the Administrative Procedure Act, the Court must “set aside” the FDA’s denial of 

pediatric exclusivity if that decision is “arbitrary, capricious, an abuse of discretion, or otherwise 

not in accordance with law.” 5 U.S.C. § 706(2)(A). In applying this standard, the Court must 

consider whether the FDA “relied on factors which Congress has not intended it to consider, 

entirely failed to consider an important aspect of the problem, [or] offered an explanation for its 

decision that runs counter to the evidence before the agency.” State Farm, 463 U.S. at 43. 

Although the Court must assess whether the FDA “examine[d] the relevant data and articulate[d] 

a . . . rational connection between the facts found and the choice made,” it may not “substitute its 

[own] judgment for that of the [FDA].” Id. Deference to the agency’s determination, moreover, 

“is especially warranted where,” as here, “the decision at issue ‘requires a high level of technical 
30

expertise.’” Safari Club, 878 F.3d at 325–26 (quoting Marsh v. Or. Nat. Res. Council, 490 U.S. 

360, 377 (1989)).

The FDA concluded that Amgen’s reports did not “fairly respond” to the written request 

because the data from Study 3 and the other sources did not yield “clinically meaningful” 

information on cinacalcet’s safety—an objective of the written request—in one of the specified 

age groups, pediatric patients ages 28 days to < 6 years. AR 1647–48. The agency looked both 

to the results of Study 3 and the rest of Amgen’s data before concluding that Amgen had “failed 

to obtain the safety data called for in the [written request]” and, thus, the “needed information” 

on cinacalcet’s use in children. AR 1638. With respect to Study 3, the FDA explained that 

“[t]he choice of a minimum of 15 patients reflect[ed] a reasonable balance between study 

feasibility and data sufficiency.” AR 1645. But the data that Amgen generated was “not 

sufficient to evaluate the primary endpoint of safety in the younger population” because there 

were “only 4 completers.” Id. Another problem was that “almost no participants provid[ed] 

safety data at effective dose levels;” by the twenty-fourth week of the twenty-six-week study, 

data on a key metric of cinacalcet’s efficacy was not available for 95% of the participants. Id. In 

addition, the FDA concluded that it could not rely on “additional safety data gathered” in other 

studies “to inform safety in the intended use for the youngest pediatric population.” AR 1647. 

As the foregoing discussion demonstrates, the FDA drew on its expertise and articulated a 

“rational connection between the facts” and its decision to deny pediatric exclusivity for 

Sensipar.

Amgen offers three reasons why, in its view, the FDA’s denial of pediatric exclusivity 

was arbitrary and capricious: (1) its studies satisfied the “fairly respond” requirement, even under 

the FDA’s reading of the statute; (2) the FDA arbitrarily refused to consider evidence of 
31

Amgen’s efforts to enroll additional patients in Study 3; and (3) the FDA treated Amgen 

differently than two similarly situated entities, without offering a reasoned basis for doing so. 

The first two arguments fail, but the third—Amgen’s claim of inconsistent treatment—warrants 

further consideration from the agency.

1. Satisfaction of the FDA’s Standard

Amgen contends that it “achieved ‘meaningful labeling,’” Dkt. 60-1 at 38, because, 

pursuant to 21 U.S.C. § 355a(j)’s labeling requirement, Sensipar’s label was updated with 

information from Amgen’s studies, Dkt. 60-1 at 38–39. For the reasons discussed above, the 

Court is unpersuaded that § 355a(j) is coterminous with the FDA’s “clinically meaningful 

information” standard, see supra Part III.A.2; see also Dkt. 65-1 at 42, and more to the point for 

present purposes, the FDA has rejected the linkage that Amgen posits, and the FDA’s reading of 

the relevant provisions is eminently reasonable. As the FDA has explained, § 355a(j) mandates 

the inclusion of all results of studies undertaken in response to a written request, regardless of 

whether those results are clinically meaningful. The agency’s decision to require labeling 

changes for Sensipar pursuant to § 355a(j), accordingly, does not mean that Amgen’s studies 

“achieved ‘meaningful labeling’” for purposes of the “fairly respond” requirement.

2. The FDA’s Refusal To Consider Evidence of Amgen’s Effort

According to Amgen, the FDA “acted arbitrarily” by “refusing” to accept and consider a 

“‘briefing document . . . describ[ing] the efforts Amgen . . . made enrolling pediatric patients’” 

for Study 3. Dkt. 60-1 at 50 (quoting AR 1096). Amgen further asserts that the FDA erred in 

claiming that Amgen “could have” achieved the minimum number of patients for Study 3 with 

“greater effort.” AR 1646; see Dkt. 60-1 at 51. Although it is true, as Amgen argues, that an 

agency acts arbitrarily by “fail[ing] to consider an important aspect of the problem,” State Farm, 

463 U.S. at 43, that did not occur here. For the reasons already discussed, the FDA has 
32

reasonably interpreted the “fairly respond” requirement in a manner that does not encompass a

sponsor’s efforts. Thus, information on Amgen’s work on enrollment is not an “important 

aspect” of the “fairly respond” determination because the FDA did not deny pediatric exclusivity 

based on Amgen’s efforts (or lack thereof).

3. Inconsistent Treatment

Amgen also argues that the FDA’s decision should be set aside because it is inconsistent 

with the approach the FDA has taken in similar cases. Dkt. 60-1 at 45–50. When an agency 

“treat[s] similarly situated parties differently,” it must provide an “adequate explanation to 

justify” the disparate outcomes. Burlington N. & Santa Fe Ry. Co. v. Surface Transp. Bd., 403

F.3d 771, 776 (D.C. Cir. 2005); see also Cty. of Los Angeles v. Shalala, 192 F.3d 1005, 1022 

(D.C. Cir. 1999); Transactive Corp. v. United States, 91 F.3d 232, 237 (D.C. Cir. 1996); 

Petroleum Commc’ns, Inc. v. FCC, 22 F.3d 1164, 1172 (D.C. Cir. 1994); New Orleans Channel 

20, Inc. v. FCC, 830 F.2d 361, 366 (D.C. Cir. 1987). Without such a “reasoned explanation,” the 

agency’s “action is arbitrary and capricious and cannot be upheld.” Burlington N. & Santa Fe, 

403 F.3d at 777. Relying on this rule, Amgen contends that the FDA’s decisions granting

pediatric exclusivity for Orencia (abatacept) and Ortho Tri-Cyclen (ethinyl estradiol; 

norgestimate) are inconsistent with its denial for Sensipar, and that the agency has failed to 

“provide a legitimate reason” for treating Sensipar differently. Dkt. 60-1 at 45 (quoting Bracco 

Diagnostics, Inc. v. Shalala, 963 F. Supp. 20, 27 (D.D.C. 1997)). As explained below, the Court 

agrees with Amgen about one of these precedents, but not the other.

As an initial matter, the Court is unconvinced that the FDA, without explanation, applied 

a more onerous standard in rejecting Amgen’s studies than it applied in accepting the studies 

submitted by Orencia’s sponsor, Bristol-Myers Squibb (“BMS”). Amgen is correct that the FDA 

granted pediatric exclusivity for Orencia even though one of BMS’s studies—involving the 
33

intravenous use of Orencia in patients ages 6 to 17 years, AR 1727—did not meet the terms of 

the written request. AR 1492. As the FDA explained to Amgen in its reconsideration decision, 

however, it granted pediatric exclusivity because the “overall data” from the studies BMS 

conducted “provided a sufficient safety database to draw supportable conclusions about the 

drug’s safety in the relevant pediatric age groups” and “was sufficient to label the product for 

pediatric use.” Id. The difference between the BMS and Amgen studies, moreover, was marked: 

BMS submitted data from 164 of the required 180 patients, whereas Amgen submitted data from 

only 4 of the required 15 patients in Study 3. Id. In the FDA’s expert opinion, BMS’s studies 

produced “robust clinical trial data,” while Amgen’s studies, in contrast, “did not yield an 

interpretable evaluation of product safety.” Id.

Notwithstanding these “important” differences, id., Amgen contends that the FDA’s 

Orencia decision is inconsistent with its Sensipar decision for two reasons. First, Amgen argues 

that the FDA considered the “overall data” from the two Orencia studies to assess whether they 

yielded “clinically meaningful information,” but for Sensipar the FDA restricted itself to 

“analyzing Study 3 in isolation.” Dkt. 60-1 at 50. The record, however, contradicts that 

characterization of the FDA’s approach to Sensipar. The agency found that “[d]ata from Study 3 

were not sufficient to evaluate . . . safety in the younger population,” AR 1645, and that this 

“shortage” was “not compensated by additional safety data gathered in children < 6 years old in 

Study 1 (single dose study), a retrospective observational study, and a prospective cohort registry 

study,” AR 1647. The FDA thus considered overall data in both cases. 

Second, Amgen contends that the FDA rejected its study reports because they did not 

result in meaningful labeling changes but accepted BMS’s reports even though BMS’s studies 

did not result in a labeling change. Dkt. 60-1 at 48. The fact that the FDA did not require a 
34

labeling change for Orencia, however, does not mean that the BMS’s studies did not yield 

meaningful labeling information or, indeed, “information . . . sufficient to label the product for 

pediatric use.” AR 1492. Rather, as all agree, the FDA had previously approved labeling

information regarding the intravenous use of the drug in pediatric patients. See AR 1736, 1773–

74. The FDA reasonably concluded that an additional study was nonetheless warranted, and it 

reasonably concluded that the results of that study and the overall data confirmed that “the 

product was safe for use” by patients ages 6 to 17 years. AR 1491–92. Although Amgen 

suggests that this confirmation must not have been “clinically meaningful” because the FDA, 

under its own regulations, required “substantial evidence” to approve the prior label, Dkt. 67 at 

27–28, that argument asks that the Court tread on the agency’s expert assessment of whether a 

further study was warranted in the first place.

For Ortho Tri-Cyclen, however, Amgen has a point. In its reconsideration decision for 

Sensipar, the FDA distinguished the agency’s grant of exclusivity for Ortho Tri-Cyclen on the 

ground that the studies conducted by Ortho Tri-Cyclen’s sponsor, Johnson & Johnson, AR 1888,

met all of the terms of the written request. AR 1493; cf. AR 1485. As Amgen argues, however, 

it is—at best—unclear from the administrative record whether that premise is correct. 

The written request asked Johnson & Johnson to conduct two studies:

Study 1: A randomized, double-blind, placebo-controlled study to examine the 

efficacy and safety of Ortho Tri-Cyclen® in the treatment of adolescent patients 

with anorexia nervosa (AN).

Study 2: A pharmacokinetics (PK) study to assess the single-dose and steady-state 

or alternatively, population PK of ethinyl estradiol (EE), norgestrel (NG), and 

norelgestromin (NGMN) in pediatric patients with [anorexia].

AR 1871. The objective of Study 1 was to “assess the effect” of Ortho Tri-Cyclen “on bone 

mineral density (BMD) of the lumbar spine and hip in patients with anorexia.” Id. The objective 
35

of Study 2 was to “assess the single-dose and steady-state or, alternatively, population 

[pharmacokinetics] of [norelgestromin], [norgestrel], and [ethinyl estradiol] in pediatric patients 

with [anorexia].” Id. The written request set forth more detailed requirements for both studies. 

As relevant here, Study 1 specified the following design parameters: one year in duration and 

“approximately 120 adolescent women” ages “12 through 17 years” with anorexia as defined by 

the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (“DSM-IV”). AR 

1872. Amgen contends that many of the women enrolled in Study 1 “did not meet . . . the DSMIV diagnostic criteria for anorexia.” Dkt. 60-1 at 47 (quoting AR 1916).

In its Sensipar reconsideration decision, the FDA offers little support for its conclusion 

that Johnson & Johnson satisfied the terms of Study 1. The agency acknowledges that it was 

“unable to locate the Board’s decision granting exclusivity” to Johnson & Johnson, and asserts, 

without explanation, that the deciding official “reviewed other relevant documents and 

determined that the sponsor’s studies met the terms” of the written request. AR 1493. In its 

brief before this Court, moreover, the FDA identifies only one possible source supporting its 

conclusion: in a clinical review prepared after the FDA had granted Johnson & Johnson’s request 

for pediatric exclusivity, a medical reviewer noted that he had previously “recommended that 

[Johnson & Johnson] receive pediatric exclusivity, since the requested study was conducted in 

agreement with the [w]ritten [r]request.” AR 1885. This document reflects the reviewer’s 

recommendation on exclusivity, but not the analysis or conclusions of the deciding official. And 

the reviewer did not explain what he meant by “conducted in agreement with the [w]ritten 

[r]equest.” Given the deferential standard of review, however, this might ordinarily suffice to 

sustain the FDA’s decision. See, e.g., Envtl. Def. Fund, Inc. v. Costle, 657 F.2d 275, 283 (D.C. 
36

Cir. 1981). But other material in the administrative record casts doubt on whether Johnson & 

Johnson, in fact, met the terms of the written request with respect to Study 1. 

From what the Court can glean from the record, Johnson & Johnson enrolled “146 

randomized and 123 treated subjects,” all of whom were “female and aged 10 to 17 years at 

screening.”5

 AR 1918. Following a May 2005 clinical review, however, the FDA found that 

“the majority of the 123 subjects treated . . . did not meet either the DSM-IV diagnostic criteria 

for anorexia nervosa or the DSM-IV diagnostic criteria modified by the sponsor for anorexia 

nervosa.”6 AR 1916; see also AR 1921 (noting that only 77 of the 123 patients “had the word 

‘anorexia’ listed” in their medical histories). In particular, 76 patients “had a baseline Body 

Mass Index (BMI) at or above the 10th percentile for age and [therefore] should not have been 

enrolled into the study.” AR 1948. And, at least in part because “a significant number” of 

treated patients “did not me[e]t the DSM-IV criteria,” the FDA “reviewer consider[ed] the data 

. . . insufficient to address safety concerns regarding the use of Ortho Tri-Cyclen in subjects with 

anorexia.” AR 1937.

Based on this record, Amgen argues that the FDA granted pediatric exclusivity even 

though the sponsor’s study reports “neither met the terms of the written request nor generated 

meaningful labeling.” Dkt. 60-1 at 45. Although the FDA addresses some of Amgen’s 

arguments, it has not responded to Amgen’s contention that the majority of the 123 patients 

treated in Study 1 did not meet the DSM-IV diagnostic criteria for anorexia nervosa, as required 

by the written request. There may be an answer to Amgen’s contention. It is possible, for 

 5

 Two of these patients were 10 or 11, yielding a total of 121 treated subjects ages 12 through 17 

years. See AR 1951.

6

 Of the 123 treated patients with anorexia nervosa, 61 received active treatment and 62 received 

placebos. AR 1907.
37

instance, that the FDA granted Johnson & Johnson’s pediatric exclusivity based on the mistaken 

belief that Study 1 was conducted in full compliance with the terms of the written request, and 

that the failure to enroll patients meeting the DSM-IV criteria was discovered only after the fact. 

Or it may be that Johnson & Johnson’s study did, in fact, comply with the requirement. Or the 

FDA may have some other basis for distinguishing, disregarding, or abandoning the Ortho TriCyclen precedent. If so, however, the agency must explain that rationale and identify the 

relevant evidence for its conclusions in the administrative record. Because the FDA has yet to 

do so, the Court concludes that the agency’s decision is—at least in this one respect—arbitrary 

and capricious and that a limited remand is necessary. See Lilliputian Sys., Inc. v. Pipeline & 

Hazardous Materials Safety Admin., 741 F.3d 1309, 1313 (D.C. Cir. 2014) (“[A]n agency cannot 

treat similarly situated entities differently unless it ‘support[s] th[e] disparate treatment with a 

reasoned explanation and substantial evidence in the record.’” (quoting Burlington N. & Santa 

Fe, 403 F.3d at 777)).

This disposition raises one final question: whether to remand the matter with or without 

vacatur of the FDA’s denial of pediatric exclusivity. The Court must consider “two factors: the 

likelihood that [the] ‘deficiencies’ . . . can be redressed on remand, even if the agency reaches 

the same result, and the ‘disruptive consequences’ of vacatur.” Black Oak Energy, LLC v. 

FERC, 725 F.3d 230, 244 (D.C. Cir. 2013) (quoting Allied-Signal v. Nuclear Regulatory 

Comm’n, 988 F.2d 146, 150–51 (D.C. Cir. 1993)). The parties, however, have not addressed the 

question of vacatur—nor is it obvious what practical consequences, if any, turn on the question 

given that the FDA denied Amgen’s request for pediatric exclusivity and that setting aside that

decision would not accord Amgen the ultimate relief that it seeks. Rather than decide the issue 

without input from the parties, the Court will order the parties to appear for a status conference
38

(1) to address whether the limited remand required by this decision should be with or without 

vacatur, and (2) to develop a schedule for the FDA promptly to address the Ortho Tri-Cyclen 

precedent on remand.

With respect to Amgen’s arbitrary and capricious claim, the Court, accordingly, will 

grant summary judgment to the FDA in part and to Amgen in part, and will remand the matter to 

the FDA for further consideration of its Ortho Tri-Cyclen decision.

C. Notice Claims

Amgen argues that the “FDA’s application of its previously unannounced” interpretation 

of “fairly respond” to Amgen’s request for pediatric exclusivity violated the “fair notice” 

principle of the APA and the due process clause and constituted impermissible retroactive 

rulemaking. Although these contentions overlap in substantial part, the Court will address each 

in turn.

1. Fair Notice

With respect to its “fair notice” claim, Amgen asserts that it lacked “[a]dvance 

knowledge” of the FDA’s interpretation of “fairly respond” and that it “had no way to predict at 

the time it agreed” to the written request that the agency would adopt such an interpretation. 

Dkt. 60-1 at 42. This lack of notice, Amgen continues, “had real consequences for Amgen” 

because the company “spent vast time and resources undertaking pediatric testing.” Id. at 42–43. 

As explained below, Amgen’s argument fails on both the law and the facts.

As to the law, Amgen’s contention that the APA (or due process) precludes an agency 

from applying an interpretation of a statute or regulation that cannot be discerned in advance 

with “ascertainable certainty,” Dkt. 60-1 at 41 (citing Gen. Elec. Co. v. EPA, 53 F.3d 1324, 

1328–29 (D.C. Cir. 1995)), overstates the law. The “ascertainable certainty” standard “applies 

where . . . a party is deprived of ‘property,’ or where ‘sanctions are drastic.’” Darrell Andrews 
39

Trucking, Inc. v. Fed. Motor Carrier Safety Admin., 296 F.3d 1120, 1130 n.8 (D.C. Cir. 2002) 

(quoting Gen. Elec., 296 F.3d at 1328–29). It precludes an agency from imposing a criminal or 

civil penalty or sanction on a regulated party without fair notice. See, e.g., Darrell Andrews 

Trucking, 296 F.3d at 1130; Gen. Elec., 53 F.3d at 1328–29. And, it precludes an agency from 

rejecting a filing as untimely or for failing to comply with some other filing requirement if the 

agency has not provided fair notice of the time limit or filing requirement. See, e.g., PMD 

Produce Brokerage Co. v. USDA, 234 F.3d 48, 52–53 (D.C. Cir. 2000). But Amgen has failed to 

identify any precedent beyond those contexts in which the courts have applied the “ascertainable 

certainty” requirement to agency adjudicative actions involving questions of statutory or 

regulatory interpretation. It is common, moreover, for agencies to set forth their statutory 

interpretations in the adjudicative process. Against that backdrop, the implication of Amgen’s 

argument—that the “ascertainable certainty” standard applies to all adjudications in which a 

party has a substantial stake or a reliance interest—would substantially rework the regulatory 

process. And it would do so for no good reason: Chevron and the overarching arbitrary and 

capricious standard already prevent agencies from engaging in the type of “Kafkaesque” 

endeavors that Amgen fears. See Dkt. 60-1 at 41.

Amgen’s argument also fails on the facts. The “ascertainable certainty” rule prevents 

agencies from taking regulated parties by surprise. See Gen. Elec., 53 F.3d at 1329–30 (citing 

Rollins Envtl. Servs., Inc. v. EPA, 937 F.2d 649, 651 (D.C. Cir. 1991); Satellite Broad. Co. v. 

FCC, 824 F.2d 1, 2 (D.C. Cir. 1987); Gates & Fox Co. v. OSHRC, 790 F.2d 154, 155 (D.C. Cir. 

1986)). Here, however, Amgen knew that its reports would need to “fairly respond” to the 

written request, see 21 U.S.C. § 355a(d)(4), Amgen knew what the written request required, and 

Amgen knew what the written request sought to attain, AR 1076–89. Amgen was aware, 
40

moreover, that the FDA had previously required that the requested studies “meet [every] single 

term of [the] written request.” Merck, 148 F. Supp. 2d at 30. And, Amgen knew that one district 

court had held that perfect compliance was not required and that, instead, it was sufficient “if the 

stud[ies] as a whole [provide] a fair response to the written request.” Id. The fact that the FDA 

subsequently adopted a more generous reading of the statute—and expanded the universe of 

study responses that it considered sufficient—does not constitute unfair surprise.

 The administrative record, moreover, confirms that Amgen was not blind to the relevant 

requirements. Among other things, when Amgen realized that it would be unable to meet the 

terms of the written request, it sought to amend that request—it did not simply rest on the 

assumption that its best efforts or the limited results that it did obtain would suffice. AR 1091–

92. In addition, when Amgen submitted its study report and requested pediatric exclusivity, AR 

1152, it argued that pediatric exclusivity was warranted because

sufficient data has been collected in the overall cinacalcet pediatric development 

program . . . to satisfy the primary objectives of this study, which were to evaluate 

the safety and tolerability of cinacalcet in pediatric patients ages 28 days to < 6 

years and to characterize the PK profile in pediatric patients.

AR 1160 (emphasis added). Although not a perfect match, Amgen’s argument for why it 

deserved pediatric exclusivity closely reflects the FDA’s understanding that the studies must 

produce results sufficient to meet “the objectives of the” written request. AR 1637.

Finally, Amgen relies on the following statement from the FDA’s website, which it 

argues is inconsistent with the FDA’s interpretation: “Pediatric exclusivity is not tied to approval 

of labeling containing information on pediatric use based on the studies conducted.” Dkt. 60-1 at 

40 (quoting Dkt. 60-2 at 3 (emphasis omitted)). The website, however, goes on to explain that 

the FDA’s decision whether to grant pediatric exclusivity is based on the agency’s assessment of 

whether “the [sponsor’s] studies were conducted in accordance with the terms of the [w]ritten 
41

[r]equest.” Dkt. 60-2 at 3. That statement is entirely consistent with the first prong of the test 

that the FDA now espouses: the FDA will grant pediatric exclusivity to a sponsor that “properly 

execute[s]” the requested studies, even if the sponsor’s studies fail to “result in pediatric use 

information”—i.e., information useful in labeling. AR 1637. The statement that Amgen 

identifies from the FDA website, accordingly, can be faulted—if at all—for addressing only the 

first prong of the current test, and not adding that a sponsor can also qualify for pediatric 

exclusivity if it fails to “properly execute[]” the studies but, nonetheless, achieves results that 

satisfy the objectives of the studies. That omission does nothing to advance Amgen’s “fair 

notice” argument. The fact that the FDA subsequently applied a more generous test than the one 

articulated on its website could not have unfairly surprised Amgen. Amgen would hardly be 

better off if the FDA had relied solely on the test alluded to on its website.

The Court, accordingly, will grant the FDA summary judgment on Amgen’s APA claim 

and due process claim based on a purported lack of “fair notice.”

2. Retroactivity

Amgen’s contention that the FDA’s determination violated “the principles of retroactive 

rulemaking,” Dkt. 60-1 at 43, fares no better. According to Amgen, those principles “protect 

regulated entities from the surprise of having newly developed standards applied to them in the 

course of an adjudication,” id., and the FDA’s current reading of “fairly respond” constitutes “an 

abrupt departure from the previously announced rule and from the reasonably ascertainable 

meaning of the statute,” id. at 44. This argument misunderstands how principles of retroactivity 

apply to agency adjudications.

Unlike the rules applicable to notice-and-comment rulemaking, see Bowen v. Georgetown 

Univ. Hosp., 488 U.S. 204, 208–09 (1988), “[r]etroactivity is the norm in agency adjudications 

no less than in judicial adjudications,” Am. Tel. & Tel. Co. v. FCC, 454 F.3d 329, 332 (D.C. Cir. 
42

2006). To be sure, “‘judicial hackles’ are raised when ‘an agency alters an established rule 

defining permissible conduct which has been generally recognized and relied on throughout the 

industry that it regulates.” Id. (quoting NLRB v. Majestic Weaving Co., 355 F.2d 854, 860 (2d. 

Cir. 1966) (Friendly, J.)). Beyond those limited circumstances, however, courts will set aside 

new interpretations of existing law adopted in agency adjudications only if retroactive 

application of the new interpretation “would work a ‘manifest injustice.’” Verizon Tel. Cos. v. 

FCC, 269 F.3d 1098, 1109 (D.C. Cir. 2001) (citation omitted); see also Qwest Servs. Corp. v. 

FCC, 509 F.3d 531, 539 (D.C. Cir. 2007); Am. Tel., 454 F.3d at 332; Clark-Cowlitz Joint 

Operating Agency v. FERC, 826 F.2d 1074, 1081 (D.C. Cir. 1987) (en banc).

In determining that Amgen’s studies did not “fairly respond” to the written request, the 

FDA did not jettison a “generally recognized” rule that Amgen—or any other regulated entity—

relied upon. Indeed, the only earlier articulation of the governing rule that Amgen has identified 

is the perfect compliance rule discussed—and rejected—in the Merck case. 148 F. Supp. 2d at 

30. After Merck was decided, there may have been some uncertainty regarding the relevant 

standard, but Amgen cannot plausibly contend that the FDA altered an “established” and 

“generally recognized” rule when, in relevant respects, it adopted the rule suggested by the 

Merck decision. Id. (holding that the key question is whether “the study as a whole is a fair 

response to the written request”). Even more to the point, Amgen cannot plausibly contend that 

it relied on the FDA’s earlier, more restrictive reading of the statute. If there was some other 

“established” and “generally recognized” prior articulation of the standard that, if applied here, 

would have required the FDA to accept Amgen’s studies, Amgen has yet to identify it.

This leaves the question whether retroactive application of the test recognized in the 

FDA’s decisions in this matter would result in a “manifest injustice.” As the D.C. Circuit has 
43

explained, it “has not been entirely consistent in enunciating a standard to determine when to 

deny retroactive effect in cases involving ‘new applications of existing law, clarifications, and 

additions’ resulting from adjudicatory actions.” Verizon, 269 F.3d at 1109–10 (citing a fivefactor balancing test adopted in Clark-Cowlitz, 826 F.2d at 1081–86, a three-factor test set forth 

in Dist. Lodge 64 v. NLRB, 949 F.2d 441, 447–49 (D.C. Cir. 1991), and “other cases . . . 

jettison[ing] the multi-pronged balancing approaches altogether”). The most recent cases from 

the D.C. Circuit have eschewed a formal application of a five- or three-factor test in favor of a 

more flexible inquiry. See Qwest Servs., 509 F.3d at 539–40; Consol. Edison Co. of N.Y. v. 

FERC, 315 F.3d 316, 323–24 (D.C. Cir. 2003). Two principles, however, are clear—and 

dispositive here. First, “a mere lack of clarity in the law does not make it manifestly unjust to 

apply a subsequent clarification of that law to past conduct.” Qwest Servs., 509 F.3d at 540. 

Indeed, “[c]larifying the law and applying that clarification to past behavior are routine functions 

of adjudication.” Id. Second, the manifest injustice standard is satisfied only if the affected 

party has “detrimentally relied on the established legal regime.” Consol. Edison, 315 F.3d at 323 

(citing Clark-Cowlitz, 826 F.2d at 1081; Hatch v. FERC, 654 F.2d 825, 835 (D.C. Cir. 1981)). It 

is not enough to show that the affected party might have relied on an assumption regarding the 

state of law; the relevant question is whether it reasonably relied “on settled law contrary to the 

rule established in the adjudication.” Qwest Servs., 509 F.3d at 540.

For the reasons discussed above, the FDA’s retroactive application of its “clinically 

meaningful information” standard did not work a manifest injustice. Indeed, if anything, it is 

Amgen’s proposed standard that lacks any precedential pedigree. The truth is, the FDA relied on 

an overly restrictive test before Merck; the district court in that case correctly observed that the 

FDA’s prior test could not be squared with the statutory text; and, in this case, the FDA 
44

articulated a standard that is consistent with the statutory text and the Merck decision. There is 

nothing unfair, much less “manifestly unjust,” about the FDA’s application of that standard to 

Amgen.

Accordingly, the Court will grant summary judgment to the FDA with respect to 

Amgen’s retroactivity claim.

CONCLUSION

For the reasons stated above, it is hereby ORDERED that Amgen’s motion for summary 

judgment, Dkt. 60, is DENIED in part and GRANTED in part; and it is further

ORDERED that the FDA’s motion for summary judgment, Dkt. 65, and the intervenordefendants’ motion for summary judgment, Dkt. 63, are DENIED in part and GRANTED in 

part; and it is further

ORDERED that the case is remanded to the FDA for the limited purpose of addressing 

whether the agency’s prior decision granting pediatric exclusivity for Ortho Tri-Cyclen is 

consistent with its decision denying pediatric exclusivity for Sensipar and, if not, whether there is 

a reasoned explanation for the disparate outcomes.

SO ORDERED.

 /s/ Randolph D. Moss 

 RANDOLPH D. MOSS 

 United States District Judge 

Date: January 26, 2018