Maximizing Patent Term in the United States: Patent Term Adjustment, Patent Term Extension, and the Evolving Law of Obviousness-Type Double Patenting
Introduction – Background and Terminal Disclaimers
Under U.S. law, most patents are limited to a term of 20 years from the earliest nonprovisional filing date. However, Patent Term Adjustment (PTA) and Patent Term Extension (PTE) can be used in certain circumstances to gain often significant additional patent term. They serve distinct functions – PTA can mitigate the loss of term due to U.S. Patent & Trademark Office (“USPTO”) delays, while PTE can mitigate the loss of term due to other reasons, most importantly regulatory approval and/or reviewal processes.
Limitations on the application of PTA and/or PTE can arise where Terminal Disclaimers (TD) or large patent families are involved. When a patent application is allowed but an earlier related patent has issued, e.g., via a continuation application, the USPTO may require a TD, with the effect that both patents will issue on the same date. TDs can be useful because they allow applicants to patent otherwise obvious variations to an original invention. TDs usually arise during prosecution in connection with continuation applications, but they may also arise in litigation, even if the USPTO did not require a TD in the first place. Courts have even permitted retroactive TDs to fix what would otherwise be an obvious and hence invalid patent from being in force.
Patent Term Adjustment (PTA)
PTA is a term mitigation tool for delays caused by the USPTO – not the applicant – during prosecution. PTA may be applied to each patent in a family.
PTA is calculated by taking the number of days of delay caused by the USPTO less the number of days of delay caused by the applicant.[1] Days of USPTO delay are calculated as the sum of A-delays, B-delays, and C-delays less AB overlap.[2] A-delays are caused by the USPTO during patent prosecution.[3] B-delays account for USPTO accountability to conclude patent prosecution within 3 years of filing – failure of which creates delays accrued for every day beyond the stipulated period.[4] C-delays can occur as a result of, inter alia, derivation proceedings, secrecy orders, and appeals.[5] Applicant delays can occur for a variety of reasons, including omitting information from the application, failing to timely pay fees and/or respond to Office Actions, and filing an information disclosure statement (IDS) after a request for continued examination (RCE).[6]
PTA was designed to provide patent applicants an opportunity for a full 17 years of patent term, which was the law when the US was under a first to invent system.[7] Under the first to file system, term is typically capped at 20 years from the filing date – which can lead to less than 17 years of patent term for long pending applications. PTA can be limited or lost by the filing of a terminal disclaimer in response to an obviousness-type double patenting (ODP) rejection over a previously granted parent patent.[8] Further, ODP must continue to apply when (1) applications directed to two inventions with overlapping subject matter are simultaneously filed and (2) the underlying issued patents have different expiration dates.[9]
Patent Term Extension (PTE)
PTE can provide patent applicants an opportunity for additional patent term lost to regulatory delays.[10] Owners of patents on certain human and veterinary drugs, additives, and medical devices can seek to restore some of the time lost while awaiting premarket government approval from a regulatory agency.[11] PTE is available for a patent which: claims a product, a method of using a product, or a method of manufacturing a product; has not been previously extended; has issued prior to regulatory approval; and has not expired before submission of the PTE application.[12] PTE must be requested within 60 days of regulatory approval.[13] Only one PTE is granted per patent/product.[14] For drugs and medical devices, this means there is no PTE where a patent is directed to combinations of two previously approved drugs, new formulations of previously approved drug products, or new uses of previously approved medical devices.[15]
The term of a patent can be extended by the time consumed by the regulatory review period after the patent is issued, up to five years but no greater than fourteen years of product approval.[16] While PTE is reduced where there is also PTA[17], PTE is added even if the patent was subject to a TD.[18]
Obviousness-Type Double Patenting (ODP)
ODP most commonly arises during patent prosecution, but can also arise during patent litigation as a defense. Its underlying purpose is to prevent unjustified patent term adjustment using obvious variants of an invention.[19]
In Gilead Sciences, Inc. v. Natco Pharma Ltd., two patents owned by Gilead were at issue: U.S. 5,952,375, which was filed first, and U.S. 5,763,483, which was filed later but issued first.[20] These patents did not claim common priority and have different expiration dates.[21] The ‘483 patent claimed patentably indistinct subject matter and resulted in the asserted claims of ‘483 having two years of additional patent term.[22]
Natco sued Gilead for infringement of ‘483 after Natco filed an FDA request for approval to market a generic version of the disclosed drug and argued that ‘483 was invalid for ODP.[23] The Federal Circuit ruled in favor of Natco, invalidating the ‘483 patent using ‘375 as an ODP reference, holding that the patent’s expiration date is relevant to assess ODP issues.[24] The court recognized that a fundamental purpose of ODP is to prevent an inventor from securing a second, later expiring patent for the same invention.[25]
In re Cellect, LLC arose from the appeal of four related ex parte reexamination proceedings involving a family of patents for electronic image sensors.[26] TDs could not be filed because the ODP reference patents had expired.[27] The patents were on admittedly indistinct subject matter, all stemming from a common priority application (although the chains included CIP applications).[28]
Cellect brought suit for patent infringement, and invalidity based on ODP was raised as a defense.[29] Cellect argued that ODP could not negate the statutory grant of PTA.[30] The court held that when evaluating ODP on a patent with PTA, the relevant expiration date is the PTA date.[31] The court also rejected an argument that PTA and PTE should be treated the same based on different wording in their respective statutes, as the PTE statute does not reference TD.[32] Notably, the court expressly limited its holding to the circumstances of the case.
Allergan USA, Inc. v. MSN Labs. (2024) involved U.S. 7,741,356 for eluxadoline (Viberzi), for treating irritable bowel syndrome (IBS), and other continuation patents (‘011 and ‘709) that claim formulations of eluxadoline.[33] The ‘356 patent was first-filed, first-issued, and received considerable PTA (1107 days).[34] The ‘011 and ‘709 patents were both later-filed and later-issued patents, neither of which had PTA, and thus expired well before the ‘356 patent.[35] Sun Pharmaceuticals produced a generic version of eluxadoline.[36] It applied for FDA approval, including a certification statement contending that the claims of the ‘356 patent were invalid.[37] Allergan then sued Sun for infringement, particularly of claim 40 of the ‘356 patent.[38] The district court found asserted claim 40 of ‘356 invalid for ODP over claims of its child patents, noting “the ’356 patent must be invalidated by the ’011 and ’709 reference patents simply because it expires later”.[39]
The Federal Circuit disagreed, and held that “a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim having a common priority date”.[40] It noted the ‘356 patent is not a second later-expiring patent for the same invention, and further, the purpose of ODP is to prevent patentees from obtaining a second patent on a patentably indistinct invention to extend the life of a first patent.[41] The panel distinguished Allergen from Gilead as Gilead expressly limited its holding to the circumstances of that case, which involved two chains of patents that did not share priority, and the challenged claims in Gilead were filed later, and claimed a later priority date, than the claims of the ODP reference patent, resulting in an unwarranted extension of patent term for an invention that had already been the subject of an earlier-filed, earlier-expiring patent. In contrast, in Allergen, the challenged claims were the first-filed and first-issued.[42]
MSN filed a petition for rehearing en banc on September 26, 2024, arguing that the decision cannot be reconciled with Gilead, Cellect, and other relevant cases.[43] MSN argued that the case is indistinguishable from Cellect, as both invalidated a first-filed, first-issued patent based on family members with PTA.[44]
*Benjamin Bafumi, a law clerk at Baker Botts, assisted in the preparation of this article.
[1] 35 U.S.C. § 154(b); see Explanation of Patent Term Adjustment Calculation, USPTO, https://www.uspto.gov/patents/apply/checking-application-status/pair-announcements/explanation-patent-term (last visited Oct. 10, 2024).
[2] Id.
[3] 35 U.S.C. § 154(b)(1)(A).
[4] 35 U.S.C. § 154(b)(1)(B).
[5] 35 U.S.C. § 154(b)(1)(C).
[6] See CFR 1.704(c)(8). Note: filing an IDS at the same time as an RCE may not constitute an applicant delay – but can be considered failure to engage in reasonable efforts to conclude prosecution. See 1.704(c)(12); (d) (“a request for continued examination … with an information disclosure statement … will not be considered a failure to engage in reasonable efforts to conclude prosecution” … if the RCE is accompanied by a statement that each item of information contained in the IDS: “(i) Was first cited in any communication from a patent office in a counterpart foreign or international application or from the Office, and … was not received … more than thirty days prior to … filing; or (ii) Is a communication that was issued by a patent office in a counterpart foreign or international application or by the Office, and … was not received … more than thirty days prior to … filing”).
[7] See Talis Dzenitis, American Inventors Protection Act – Summary, USPTO, https://www.uspto.gov/patents/laws/american-inventors-protection-act-1999/american-inventors-protection-a-2 (last visited Oct. 22, 2024).
[8] In re Cellect, 2023 WL 5519716 (Fed. Cir. Aug. 28, 2023).
[9] Id. SCOTUS review here was denied.
[10] 35 U.S.C. § 156.
[11] Id. PTE-eligible patents: human drugs, antibiotics, biologics; food additives, color additives; medical devices; animal drug products; veterinary biological products; and methods of using and manufacturing such products.
[12] Id. Note: an interim extension is available if applicant "reasonably expects" that approval process may extend beyond expiration of patent. MPEP 2755.01.
[13] See 21 C.F.R. 60.10; MPEP 2756 See also Unimed v. Quigg, 888 F.2d 826, 828 (Fed. Cir. 1989).
[14] PTE available as long as it is a new device. See U.S. Pat 4,702,253. A new indication for same device not sufficient. See Denial of PTE for U.S. Pat 5,299,569. One can obtain extensions for multiple patents based on same family of devices. PTE can be obtained even if no clinical testing was required. See Grant of PTE for U.S. Patent No. 4,702,253.
[15] Id.
[16] 35 U.S.C. § 156(c); (g)(6).
[17] See 35 U.S.C. § 156(a) (noting that PTE “shall include any patent term adjustment granted under section 154(b)”).
[18] Merck & Co. v. Hi-Tech Pharmacal Co., 482 F.3d 1317, 1318 (Fed. Cir. 2007).
[19] See Allergan USA, Inc. v. MSN Labs. Priv. Ltd., 111 F.4th 1358, 1366-1367 (Fed. Cir. 2024).
[20] Gilead Scis., Inc. v. Natco Pharma Ltd., 753 F.3d 1208, 1209 (Fed. Cir. 2014).
[21] Id.
[22] Id.
[23] Id.
[24] Id. at 1215; 1217. The court also held ODP rejections can be overcome by filing TDs. See id. (noting that filings TDs “can preserve the validity of the later-expiring patent by aligning its expiration date with that of the earlier-expiring patent”).
[25] Id. at 1212.
[26] In re Cellect, LLC, 81 F.4th 1216, 1219 (Fed. Cir. 2023).
[27] Id. at 1219-1220.
[28] Id.
[29] Id.
[30] Id. at 1220-1221.
[31] Id. at 1231, 1226. Note: the Federal Circuit previously held that, where the patent has received PTE, its expiration date used for the ODP analysis is the patent’s expiration date before the PTE has been added. Novartis v. Ezra, 909 F.3d 1367, 1373 (Fed. Cir. 2018).
[32] Cellect, 81 F.4th at 1226.
[33] Allergan, 111 F.4th at 1362.
[34] Id. at 1364.
[35] Id.
[36] Id.
[37] Id. at 1364-1365.
[38] Id.
[39] Id. at 1369 (emphasis added). The court interpreted Gilead and Cellect as requiring it to look only at expiration dates, not filing or issue dates.
[40] Id. at 1369.
[41] Id. at 1369; 1371.
[42] See id.
[43] Combined Petition for Panel Rehearing and Rehearing en Banc, Allergen v. MSN, 111 F.4th 1358 (Fed. Cir. 2024) (No. 24-1061).
[44] Id.
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