IP Law Essentials

Introduction to Patent Term Extensions (PTE)


Patent holders have the right to exclude others from making, using, selling, or offering to sell an invention but only during the time a patent is in force.[1] This right disappears upon patent expiration, making the "monopoly" period that a patent is in force an important issue. Patents filed and granted on or after June 8, 1995 typically expire twenty years from the date of the first filing of the patent application ("patent term").[2] However, the patent term may be modified. Here, we discuss one way of extending patent term called "Patent Term Extension" or "PTE."[3]

PTE is only available for certain types of patents, most commonly patents related to drug products and medical devices. Patent holders of such patents typically benefit most after the drug or device is commercially launched and competition is excluded. However, because drugs and devices must undergo a lengthy review process at the Federal Drug Administration (FDA) prior to commercial use or launch, related patents are usually filed (thereby starting the 20-year clock) long before FDA approval. PTE is designed to restore some of the patent term "lost" during the FDA's review process.

Congress provided for PTE as part of the Drug Price Competition and Patent Term Restoration Act of 1984, PL 98-417, S 1538 98 Stat. 1585 (the "Hatch-Waxman Act").[4] Congressional records show that PTE was one piece of a carefully calibrated scheme to weigh incentives for innovation and market competition for drugs. Congress enacted PTE in part to:

"restore . . . some of the incentive for innovation which has weakened as Federal pre-market approval requirements have become more expensive and time-consuming. That incentive will produce both the investment and commitment to research [sic] and development that will again place the United States in unquestioned leadership in the field. And it will generate an increase in the number of important new drugs, among the most vital causes for this century's dramatic increase in the length and quality of life."[5]

The statute enables the owners of patents on human drug products, medical devices, food additives, or color additives, and animal drug products to obtain patent term extension for delays at the regulatory agency.[6]

PTE rights, however, are limited. For example, for a patent that claims the product, PTE only extends exclusive patent rights to any FDA-approved use for the product.[7] Thus, if the patent claims other products (let's call them products B and C) in addition to the approved product (product A), the exclusive patent rights to the other products (products B and C) expire with the original expiration date of the patent.

The specific rules and regulations governing PTE are complex. Here, we provide a brief, high-level overview of the requirements for obtaining PTE and the PTE process. For simplicity, we focus on patents related to human drug products.

Patent Term Extension Requirements

For drug-related patents, the following criteria must be met for a patent to be eligible for PTE:[8]

  1. The patent must claim the product, a method of using the product, or a method of manufacturing the product.[9]
  2. The term of the patent has not yet expired.[10]
  3. The term of the patent has not previously been extended.[11]
  4. The application for patent term extension is submitted by the patent owner or its agent.[12]
  5. The product was subject to a regulatory review period prior to its permitted commercial marketing or use.[13]
  6. The product received FDA permission for commercial marketing or use, and the permission for the commercial marketing or use of the product is the first such permission received under the provision of law under which the applicable regulatory review period occurred (e.g., Federal Food, Drug and Cosmetic Act).[14]
  7. No other patent term has been extended for the same regulatory review period for the product.[15]

To apply for PTE, the owner of the patent or its agent ("the applicant"), has to submit an application under 35 U.S.C. 156 to the United States Patent and Trademark Office ("USPTO") within the sixty-day period beginning on the same date the product received permission for commercial marketing or use from the FDA.[16] The sixty-day deadline is non-extendable, and a patent holder may lose its right to PTE if the deadline is missed.

Determining PTE Eligibility and Length

The USPTO and FDA share responsibilities for determining PTE eligibility and length.[17]

First, the USPTO determines whether the application meets all the formality requirements and whether the patent in question is eligible for extension.[18] Then, the USPTO forwards the application to the FDA to confirm whether: (1) the product was subject to a regulatory review period prior to approval, (2) the FDA's approval was the first permitted commercial marketing or use of the product, and (3) the PTE application was filed within the required sixty-day period.[19] The USPTO waits to hear back from FDA before proceeding with formal review.

After receiving the FDA's eligibility determinations, the USPTO provides the FDA with notice and a copy of the application and requests a determination of the length of the regulatory review period of the product. The FDA calculates the regulatory review period, notifies the USPTO, and publishes the calculation in the Federal Register.[20]

At this point, other parties can intervene in the process. Any person may request a revision of the regulatory review period calculation within sixty days from publication in the Federal Register.[21] Third parties also have a 180-day period to file any due diligence petitions.[22] A due diligence petition alleges that the PTE applicant did not act with due diligence in seeking FDA approval of the product during the regulatory review period (i.e., that the PTE applicant is responsible for some of the lost patent term).[23] The due diligence petition thus argues that the PTE applicant is eligible for less PTE resulting in a shorter patent term. The FDA is responsible for due diligence determinations and conducting due diligence hearings.[24] The regulatory review period determination is not final until requests for revision, due diligence petitions, and informal hearings, if any, have been resolved.

After the 180-day notice period expires, and once any due diligence petitions or hearings are resolved, the FDA sends a letter to the USPTO with its final regulatory review period determination.[25]

Patent Term Extension Calculation

Based on the information FDA published in the Federal Register and after receiving the FDA's final regulatory review period determination, the USPTO calculates the length of PTE according to a complex formula derived from the language in the statute:[26]

Patent Term Extension = RRP - PGRRP - DD - ½(TP-PGTP)


    • "RRP" is the total number of days in the regulatory review period, as determined by the FDA;
    • "PGRRP" is the number of days of the RRP that were on and before the date the patent issued;
    • "DD" is the number of days of the RRP that the applicant did not act with due diligence (typically zero if there is no due diligence petition);
    • "TP" is the drug testing phase period described in 35 U.S.C. 156(g) (which typically starts on the date an Investigational New Drug Application (IND) becomes effective and ends on the date a marketing application (e.g., a New Drug Application (NDA) or Biologics License Application (BLA) is submitted to the FDA);[27] and
    • "PGTP" is the number of days of the TP that were on and before the date the patent issued.[28]

The length of PTE resulting from the above calculation is subject to two limitations: the maximum extension that can be obtained for a patent is limited to five years;[29] and the total remaining patent term (with PTE) is limited to fourteen years from the date of product approval by the FDA.[30]

The USPTO issues its final determination and, in the event that the patent is determined to be eligible, usually provides the applicant with one month to request reconsideration of the calculated term. In the absence of a request for reconsideration, the USPTO issues the certificate of patent term extension, which becomes part of the patent's file history. The USPTO also publishes a list of patent terms extended at: https://www.uspto.gov/patent/laws-and-regulations/patent-term-extension/patent-terms-extended-under-35-usc-156. No new patent is issued to reflect the grant of PTE or the newly extended patent expiration date.

If the USPTO determines that the patent is ineligible for extension, the applicant is usually provided with two months (with available extensions) to request reconsideration of the determination. If the applicant fails to respond within two months or obtain an extension, the USPTO takes no further action. The applicant is provided only a single request for reconsideration. If the USPTO again finds the patent ineligible upon reconsideration, it is a final agency action. The applicant may pursue judicial review via a court action.[31]


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[1] See 35 U.S.C. 271(a).

[2] See 35 U.S.C. 154(a)(2). Before the Uruguay Round Agreements Act (Public Law 103-465, 108 Stat. 4809 (1994)), which became effective on June 8, 1995, patents typically had 17 years of patent life from the date the patent was issued.

[3] Another method of extending patent term, Patent Term Adjustment (PTA), which can compensate a patent applicant for delays during patent prosecution, is outside the scope of this discussion. Likewise, terminal disclaimers, which can shorten patent term, are not discussed here.

[4] 35 U.S.C. 156.

[5] See Congressman Hatch remarks, S. 2926, 130 Cong. Rec. S10503, S10504 (daily ed. August 10, 1984).

[6] See 35 U.S.C. 156(a) and (f)(1).

[7] See 35 U.S.C. 156(b). For a patent that claims a method of using the product, PTE extends the exclusive patent rights to any use claimed by the patent and FDA-approved for the product (including later approved uses that are claimed in the patent, such as different indications for the approved product). The language of the statute is slightly different for manufacturing patents, and allows PTE to apply to both the method of manufacturing used to make the approved product and to make other (human or animal drug or biologic) products if they have been subject to a regulatory review period.

[8] See 35 U.S.C. 156(a) and 37 C.F.R. 1.710. The patent owner or its agent, their attorneys or agents, and every other individual who is substantively involved on behalf of the patent owner in a patent term extension proceeding are also subjects to a duty of disclosure in patent term extension proceedings. See 37 C.F.R. 1.765.

[9] See 35 U.S.C. 156(a) and 37 C.F.R. 1.720(a).

[10] See 35 U.S.C. 156(a)(1) and 37 C.F.R. 1.720(g). The statute allows the applicant to request an interim patent term extension under 35 U.S.C. 156(d)(5), if the term of the patent is going to expire prior to product approval. Furthermore, an applicant may request an interim patent term extension under 35 U.S.C. 156(e)(2), if the term of the patent, for which an application for patent term extension is pending, is going to expire.

[11] Except in limited situations where the patent received an interim patent term extension pursuant to 35 U.S.C. 156(d)(5) and 35 U.S.C. 156(e)(2). See 35 U.S.C. 156(a)(2) and 37 C.F.R. 1.720(b).

[12] See 35 U.S.C. 156(a)(3) and 37 C.F.R. 1.720(c).

[13] See 35 U.S.C. 156(a)(4) and 37 C.F.R. 1.720(d). The regulatory review period for a new drug product is defined in 35 U.S.C. 156(g)(1)(B).

[14] See 35 U.S.C. 156(a)(5)(A) and 37 C.F.R. 1.720(e)(1).

[15] See 35 U.S.C. 156(c)(4) and 37 C.F.R. 1.720(h).

[16] See 35 U.S.C. 156(d)(1) and 37 C.F.R. 1.720(f). The PTE application should include all the information required by 37 C.F.R. 1.710 through 1.785.

[17] See Memorandum of Understanding between the Patent and Trademark Office and the Food and Drug Administration, 52 FR 17830 (May 12, 1987).

[18] See 37 C.F.R. 1.750.

[19] See 21 C.F.R. 60.10 and MPEP Section 2756.

[20] See 35 U.S.C. 156(d)(2)(A)(ii) and 21 C.F.R. 60.20.

[21] See 21 C.F.R. 60.24.

[22] See 35 U.S.C. 156(d)(2).

[23] See 21 C.F.R. 60.30.

[24] See 21 C.F.R. Part 60, Subparts D and E. Any person may file a request for informal hearing, within the prescribed period, on the due diligence determination published by the FDA.

[25] See 21 C.F.R. 60.26.

[26] 37 C.F.R. 1.775 and 35 U.S.C. 156(c)

[27] See 21 C.F.R. 60.22(a).

[28] See 37 C.F.R. 1.775 and 35 U.S.C. 156(c).

[29] 35 U.S.C. 156(g)(6).

[30] 35 U.S.C. 156(c)(3).

[31] 5 U.S.C. 704.