243 F.3d 579 (D.C. Cir. 2001)
American Bioscience, Inc., Appellantv.Tommy G. Thompson, Secretary of Health and Human Services, et al., Appellees
No. 00-5350
United States Court of Appeals FOR THE DISTRICT OF COLUMBIA CIRCUIT
Argued January 18, 2001Decided March 30, 2001

Appeal from the United States District Court  for the District of Columbia (00cv02247)
Joseph F. Coyne, Jr. argued the cause for appellant. With  him on the briefs were Carlton A. Varner, Robert F. Green,  Arthur Y. Tsien, David F. Weeda and Jacqueline H. Eagle.  David L. Durkin entered an appearance.
Howard S. Scher, Attorney, U.S. Department of Justice,  argued the cause for federal appellees. with him on the brief were David W. Ogden, Assistant Attorney General, Douglas  N. Letter, Attorney, Wilma A. Lewis, U.S. Attorney, and  Annamarie Kempic, Counsel, Food and Drug Administration.
Philip A. Sechler argued the cause for appellees Baker  Norton Pharmaceuticals, Inc. and Zenith Goldline Pharmaceuticals, Inc. With him on the brief was Richard M. Cooper.
Before:  Edwards, Chief Judge, Sentelle and Randolph,  Circuit Judges.
Opinion for the Court filed by Circuit Judge Randolph.
Randolph, Circuit Judge:


1
This appeal from the district  court's judgment denying a preliminary injunction against the  Food and Drug Administration requires us to consider once  again the Supreme Court's opinion in Citizens to Preserve  Overton Park v. Volpe, 401 U.S. 402 (1971).  Although the  procedural background of the appeal is complex, our reasons  for vacating and remanding are simple:  the administrative  record was never filed in court and we cannot tell on what  basis the Food and Drug Administration took the agency  action the plaintiff seeks to enjoin.


2
The statutory framework is as follows.  A company wishing  to market a drug must seek FDA approval usually by completing a "New Drug Application" (NDA) containing data  from tests showing the drug's safety and effectiveness.  See  Mova Pharmaceutical Corp. v. Shalala, 140 F.3d 1060, 1063  (D.C. Cir. 1998).  The Hatch-Waxman Amendments to the  Food, Drug and Cosmetic Act in 1984 made it easier for drug  manufacturers to obtain approval of generic drugs.  See Drug  Price Competition and Patent Term Restoration Act, Pub. L.  No. 98-417, 98 Stat. 1585 (1984) (codified in scattered sections  of 21, 35 & 42 U.S.C.).  Under these amendments, a generic  drug producer need not undertake the complicated and timeconsuming testing process associated with an NDA and can  instead file an "Abbreviated New Drug Application" (ANDA),  relying on the NDA filed by the original manufacturer.  See  21 U.S.C. § 355(j);  Mova Pharmaceutical Corp., 140 F.3d at  1063.


3
While making it easier to bring generic drugs to market,  Congress also wanted to protect patent holders whose rights  might be infringed by the generic drugs.  The law, therefore,  requires that NDAs contain a list of any patents "which  claim[ ] the drug ... or which claim[ ] a method of using such  drug and with respect to which a claim of patent infringement  could reasonably be asserted if a person not licensed by the  owner engaged in the manufacture, use, or sale of the drug." 21 U.S.C. § 355(b)(1).  If new patents claiming the drug or a  method of using the drug are filed after the drug has been  approved, the approved applicant must inform the Food and  Drug Administration within 30 days.  See 21 U.S.C.  § 355(c)(2).  The FDA keeps all of this information in a  publication officially titled Approved Drug Products with  Therapeutic Equivalence, commonly called the Orange Book. See 21 U.S.C. § 355(j)(7)(A).


4
The statute also includes patent protections when an Abbreviated New Drug Application is filed.  For "each patent  which claims" the drug the applicant would like to distribute  in a generic version, the applicant must certify (1) that no  patent has been filed with the FDA;  or (2) that the patent  has expired;  or (3) that the patent has not expired, but will  expire on a particular date;  or (4) that the patent is either  invalid or the generic drug will not infringe it.  See 21 U.S.C.  § 355(j)(2)(A)(vii).


5
The fourth of these options, known as a Paragraph IV  certification, is central to the case as the parties have framed  it.  When a generic drug applicant certifies that a patent is  invalid or that its proposed generic drug will not infringe  upon it, it must also certify that it will give notice to the  patent holder that it has entered the Paragraph IV certification.  See 21 U.S.C. § 355(j)(2)(B).  If the patent holder has  not filed a patent infringement action within 45 days of  receiving this notice, the FDA may immediately approve the  ANDA.  See 21 U.S.C. § 355(j)(5)(B)(iii).  However, if a  patent infringement action is filed within 45 days, the FDA  may not approve the ANDA for 30 months, or until the patent  dispute has been resolved, whichever is sooner.  See 21  U.S.C. § 355(j)(5)(B)(iii).


6
Bristol Meyers-Squibb has FDA approval to manufacture  and distribute Taxol, an anti-cancer drug with the active  ingredient paclitaxel.  American Bioscience allegedly developed a new process that permits a patient to receive higher  doses of Taxol with fewer side effects.  American Bioscience  received U.S. Patent Number 6,906,331 (the '331 patent) for  this process on August 1, 2000.  Bristol Meyers refused to  inform the FDA of this new patent.  See 21 U.S.C.  § 355(c)(2).  American Bioscience then sued Bristol Meyers  in the Central District of California, asking the court to  compel Bristol Meyers to submit the patent for listing in the  FDA's Orange Book.  On August 11, the court entered a  temporary restraining order requiring Bristol Meyers to list  the drug with the FDA immediately.  The restraining order  also included a provision requiring Bristol Meyers to "take all  steps under its control to cause the delisting of the Taxol  Patent from the FDA's Orange Book" should it ultimately  lose the case.


7
Bristol Meyers sent a letter to the FDA indicating that it  was submitting information on the '331 patent for listing  "pursuant to an order of the United States District Court." On September 7, 2000, the District Court for the Central  District of California dissolved the temporary restraining  order on the ground that under the Federal Food, Drug and  Cosmetic Act, American Bioscience had no private right of  action to compel Bristol Meyers to list the patent.  The court  ordered Bristol Meyers to make its best efforts to remove the  patent listing from the Orange Book.


8
Enter Baker Norton Pharmaceuticals.  Baker Norton filed  an Abbreviated New Drug Application for a generic form of  Taxol in 1997.  That application was postponed because of  other infringement actions.  After the '331 patent was listed,  Baker Norton amended its application and included a Paragraph IV certification that its generic drug either did not  infringe on the '331 patent or that the '331 patent was not  valid.  It did not give notice either to Bristol Meyers or to  American Bioscience that it had included this certification in  its ANDA.  American Bioscience discovered Baker Norton's  Paragraph IV certification when Baker Norton intervened in the action in California.  American Bioscience then sued  Baker Norton for infringing the '331 patent.


9
Meanwhile, approval of Baker Norton's ANDA was proceeding.  On September 8 and September 14, 2000, Baker  Norton sent the FDA two letters amending its ANDA and  informing the FDA of the proceedings in California.  Because  the '331 patent was to be "de-listed" pursuant to the California court's order dissolving the temporary restraining order,  Baker Norton wished to amend its application, certifying that  there were no additional patents listed that it was required to  account for and removing its Paragraph IV certification regarding the '331 patent.  On September 15, 2000, the Food  and Drug Administration sent Baker Norton a letter approving its ANDA.  The FDA's letter referred to Baker Norton's  September 8 and 14 letters amending the application but  included no other discussion of the '331 patent.


10
American Bioscience brought this action against Baker  Norton and the FDA in the United States District Court for  the District of Columbia Circuit, seeking an injunction to  prevent the FDA from approving Baker Norton's application. Foremost among American Bioscience's many legal arguments was its claim that its patent had never been "de-listed"  because Bristol Meyers never intended to have it removed  from the Orange Book.  If the FDA had approved Baker  Norton's ANDA on this basis, reasoned American Bioscience,  it had done so contrary to fact.  Moreover, American Bioscience contended before the district court and contends here  that the Hatch-Waxman Act merely directs the FDA to "list"  patents as they are received.  Because its role is ministerial,  it is not authorized to remove patents from the listing once  they are received.


11
American Bioscience also contends that the FDA could not  have approved the application under the "late listing" regulation, which only requires an ANDA applicant to amend its  application to include a late-listed patent if the patent was  listed before the application was submitted.  See 21 C.F.R.  § 314.94(a)(12)(vi) (2000).  If the FDA could rely on the regulation to approve the ANDA, American Bioscience argues, the regulation itself is invalid.


12
The district court denied American Bioscience's motion for  a preliminary injunction, in part on the ground that it had not  shown a probability of success on the merits.  In reaching  this conclusion the court determined that the patent had been  "de-listed" by Bristol Meyers, that Baker Norton's ANDA  was protected by the FDA's late listing regulation, and that  the late listing regulation is valid.


13
As to "de-listing," there is not adequate support for the  district court's conclusion that the FDA approved Baker  Norton's ANDA on that basis.  The court referred to the  "FDA's determination that [Bristol Myers] had not listed  [American Bioscience's] patent within thirty days of the patent's issuance" and the FDA's "finding that [Bristol Myers]  did not list the '331 patent within thirty days...."  American  Bioscience v. Shalala, No. 00-2247, slip op. at 10, 13 (D.D.C.  Oct. 3, 2000).  But the FDA's approval letter contains no such  "determination" and no such "finding."


14
The district court also concluded "that the FDA's interpretation and application of the 'late listing' regulation are not  'plainly erroneous or inconsistent with the regulation.' " American Bioscience, slip op. at 19 (citation omitted).  But  there is nothing in the FDA's approval letter to indicate how  it interpreted this regulation;  in fact, the letter does not even  say whether the FDA was relying on the regulation.


15
The short of the matter is that we do not know whether the  FDA approved the application because it considered the '331  patent to have been "de-listed";  whether it considered the  court-ordered listing ineffective for purposes of the HatchWaxman Act;  whether it treated the application as one  covered by the late-listing regulation;  or whether, if it did,  why it thought the regulation applied.  For all we know, the  FDA made a clerical error in approving the application even  though it thought that the '331 patent had been continually  listed.


16
These problems and others stem partly from the fact that  in an "informal adjudication" such as this, the Administrative  Procedure Act, see 5 U.S.C. § 554, requires neither agency  findings of fact nor conclusions of law.  As Overton Park tells  us, judicial review nevertheless must proceed, but not by trial  de novo.  The review must "be based on the full administrative record that was before the [FDA] at the time [it] made  its decision."  401 U.S. at 420.  Overton Park arose on a  motion for a preliminary injunction (to halt construction of a  highway);  this case too comes to us upon the denial of a  preliminary injunction.  Here, as in Overton Park, the administrative record was never filed, despite APA § 706's direction  that judicial review shall be performed by "review[ing] the  whole record or those parts of it cited by a party...."  5  U.S.C. § 706;  see Overton Park, 401 U.S. at 419.  Rather  than calling for the administrative record, the district court  appears to have relied on the parties' written or oral representations to discern the basis on which the FDA acted. Surely that was not sufficient.  For all we know, the attorneys were merely speculating.  In any event, the Supreme  Court in Overton Park held that even sworn affidavits filed  during the litigation would not suffice to explain the action of  the Secretary of Transportation.  Id. at 419.


17
As in Overton Park, we leave to the district court the  determination of how best to proceed on remand in light of  what the administrative record reveals.  See 401 U.S. at 42021;  Camp v. Pitts, 411 U.S. 138 (1973) (per curiam);  National Nutritional Foods Ass'n v. FDA, 491 F.2d 1141 (2d Cir.  1974) (Friendly, J.).  We hold only that the court, before  assessing American Bioscience's probability of success on the  merits, should have required the FDA to file the administrative record and should have determined the grounds on which  the FDA granted Baker Norton's application.  Cf. Gordon G.  Young, Judicial Review of Informal Agency Action on the  Fiftieth Anniversary of the APA:  The Alleged Demise and  Actual Status of Overton Park's Requirement of Judicial  Review "On the Record," 10 Admin. L.J. Am. U. 179, 226  (1996).


18
The judgment of the district court is vacated and the case  is remanded for further proceedings consistent with this  opinion.


19
So ordered.

