Maintainability of Patent Revocation , post expiry of Patent
Introduction
This judgment, delivered on 24 February 2026 by a Division Bench of the High Court of Delhi in LPA 129/2025 (with CM APPL. 10551/2025), arises from an appeal filed by Boehringer Ingelheim Pharma GMBH and Co KG (“Boehringer”) against the judgment dated 15 January 2025 passed by a learned Single Judge of the same Court in CO (COMM IPD-PAT) 38/2022.
The Division Bench has answered both questions in the affirmative (i.e., revocation petitions remain maintainable in both scenarios), thereby upholding the Single Judge’s order dismissing Boehringer’s applications for dismissal of Macleods Pharmaceuticals Limited’s (“Macleods”) revocation petition. The judgment is noteworthy for its exhaustive statutory interpretation, reliance on international comparative law (particularly UK and European patent principles), detailed contextual analysis of the Ayyangar Committee Report, and clarification of the interplay between revocation (Section 64), invalidity defence (Section 107), and related provisions. It settles important legal concepts regarding the retrospective (ab initio) nature of revocation, the in rem effect of revocation orders, the independent nature of revocation as a standalone remedy, and the distinction between revocation and a mere defensive plea of invalidity.
Factual Background
Indian Patent No. IN 243301 (“IN’301”), granted to Boehringer on 5 October 2022 with a priority date of 21 August 2002, covers the pharmaceutical compound Linagliptin (used in diabetes treatment).
On 17 February 2022 (i.e., even before grant, but after publication), Macleods filed CO (COMM IPD-PAT) 38/2022 in the Delhi High Court under Section 64(1) seeking revocation of IN’301 on various grounds (including lack of novelty, inventive step, etc.).
Two days later, on 19 February 2022, Boehringer instituted COMS 3/2022 before the High Court of Himachal Pradesh (“the Himachal suit”) alleging that Macleods’ products infringed IN’301 and seeking permanent injunction, damages, and other reliefs. In its written statement in the Himachal suit, Macleods raised the defence of invalidity of IN’301 under Section 107(1) of the Act.
IN’301 expired by efflux of time on 18 August 2023 (20-year term from priority date). Boehringer, however, continues to press its claim for damages/account of profits in the Himachal suit for alleged past infringements during the patent’s life. Macleods’ revocation petition remained pending in Delhi.
Procedural Background
Macleods’ revocation petition (CO (COMM IPD-PAT) 38/2022) was filed in Delhi. Boehringer filed two applications in that petition:
- IA 7635/2024: Seeking dismissal on the ground that the patent had expired (Issue (ii)).
- IA 46685/2024: Seeking dismissal on the ground that Macleods had already taken a Section 107 invalidity defence in the Himachal suit (Issue (i)).
The learned Single Judge, by judgment dated 15 January 2025, dismissed both IAs, holding that the revocation petition was maintainable and could continue despite both the expiry of the patent and the raising of the Section 107 defence. Aggrieved, Boehringer preferred the present Letters Patent Appeal (LPA 129/2025). The Division Bench heard detailed arguments from Dr. Abhishek Manu Singhvi and Mr. Prashanto Chandra Sen (for Boehringer), Mr. G. Nataraj (for Macleods), and Ms. Swathi Sukumar, Sr. Adv. (Amicus Curiae). Written submissions were also filed. The appeal was reserved on 26 November 2025 and pronounced on 24 February 2026.
Dispute in Question
The core dispute crystallises into the two pure questions of law extracted in para 1 of the judgment (reproduced above). These questions are fact-agnostic but arose in the specific factual matrix of IN’301. The questions directly engage the statutory scheme of the Patents Act concerning:
- The nature and effect of revocation under Section 64 (standalone petition or counter-claim).
- The distinct character of an invalidity defence under Section 107(1) in an infringement suit.
- The continued legal existence and enforceability of a “patent” even after expiry.
- The concept of “person interested” under Section 2(1)(t) read with Section 64.
- Whether revocation operates retrospectively (ab initio) or only prospectively.
The resolution of these questions has profound implications for patent litigation strategy, multiplicity of proceedings, in rem vs in personam effects, and the survival of causes of action post-expiry (especially damages claims).
Arguments of Parties
Boehringer’s Arguments
- Revocation presupposes a “live” patent; once expired, there is nothing left to revoke (concept of revocation inherently requires the patent to be alive).
- Post-expiry, the petitioner ceases to be a “person interested” under Section 2(1)(t) because no monopoly or threat remains (relied on Dr. Reddys Laboratories Ltd v. Controller of Patents).
- Allowing revocation after expiry would be an academic exercise with no legal consequence (no retrospective effect).
- A Section 107 defence in the Himachal suit bars a parallel revocation petition because both seek the same ultimate relief (invalidity); continuing both would cause conflicting judgments across High Courts and multiplicity (relied on para 26 of Aloys Wobben v. Yogesh Mehra).
- A Section 107 defence is essentially in the nature of a counter-claim; once raised, the defendant must pursue revocation only via counter-claim in the suit (relied on Unilin Beheer B.V. v. Balaji Action Buildwell and Ramesh Chand Ardawatiya v. Anil Panjwani).
- Revocation and invalidity defence are not qualitatively different; both lead to the same practical outcome.
Macleods’ Arguments
- Section 64 uses the word “patent” (defined under Section 2(1)(m) as a patent granted under the Act) and not “patent in force”; expiry does not efface the patent’s character (no casus omissus).
- Revocation operates ab initio (retrospectively from grant date), effacing the patent as if it never existed; hence, a live cause of action survives even post-expiry (especially to defeat the patentee’s damages claim).
- Section 107 defence and revocation are fundamentally different: the former is in personam (defence in suit, at best declaratory, entered only in supplemental record under Section 151(2)), while the latter is in rem (removes patent from register entirely under Section 151(1)).
- A defendant may raise Section 107 defence and pursue revocation (via petition or counter-claim), but not both petition and counter-claim simultaneously (Aloys Wobben correctly read).
- Standalone right under Section 64 is not extinguished by expiry; patentee’s damages claim under Section 108 survives, so defendant’s right to revoke must also survive (relied on Ayyangar Committee Report paras 284–291).
- “Person interested” status continues because Macleods remains a defendant facing damages and has interest in manufacturing/sale.
Amicus Curiae
- Endorsed Macleods’ view; emphasised distinct statutory mechanisms (pre/post-grant opposition, revocation, Section 107, compulsory licensing) and retrospective effect of revocation. Relied on Ayyangar Report, Ajay Industrial Corporation, Girdhari Lal Gupta, and Section 108.
Reasoning of the Judge (Including Different Provisions of Law and Their Context)
The Division Bench’s reasoning is structured, statutory, and comparative. It first addresses the retrospective nature of revocation under Section 64.
Key Provisions and Their Contextual Interpretation
- Section 64(1): “Subject to the provisions contained in this Act, a patent … may be revoked on a petition of any person interested or of the Central Government or on a counter-claim in a suit for infringement of the patent by the High Court on any of the following grounds…”
- Context: “Patent” is not qualified by “in force”. The disjunctive “or” treats revocation petition and counter-claim at par. Grounds (lack of novelty, obviousness, insufficiency, etc.) go to the root of the grant itself → revocation must operate ab initio.
- Section 2(1)(m): Defines “patent” as “a patent for any invention granted under this Act”. Once granted, it remains a “patent” even after expiry; expiry only renders it unenforceable prospectively.
- Section 2(1)(t): “Person interested” includes a person engaged in/promoting research in the same field. Macleods, being a defendant facing damages, retains interest post-expiry.
- Section 107(1): Provides that in an infringement suit, every ground on which revocation may be sought under Section 64 is available as a defence.
- Context: Purely defensive, in personam, operates only between parties; does not remove patent from register.
- Section 151: Mandates transmission of High Court orders. Sub-section (1) (revocation) → entry in Register (effaces patent). Sub-section (2) (Section 107 finding) → entry only in supplemental record (declaratory). Clear statutory distinction.
- Section 53(4): On expiry, subject-matter not entitled to protection (affects patentee’s right to sue, not third-party right to revoke).
- Section 71: Rectification of register (separate remedy).
- Section 58 & 114: Amendment and relief for partially valid specification (available in revocation but limited in Section 107 suits).
- Ayyangar Committee Report (paras 284–291): Explains legislative intent — revocation is in rem, affects register; Section 107 is inter partes only. Supplemental record for infringement findings to inform public without effacing patent.
Core Legal Concepts Cleared
- Retrospective effect of revocation: Revocation under Section 64 operates ab initio (from date of grant), rendering the patent void as if never granted. This is not expressly stated but flows from: (a) grounds attacking the grant itself; (b) equivalence of petition and counter-claim; (c) in rem nature; (d) international alignment.
- “Patent” vs “patent in force”: Statutory definition controls; expiry does not denude the patent of its character.
- Distinction between revocation and Section 107 defence: Revocation effaces the patent entirely (in rem); Section 107 is defensive and in personam. They can co-exist.
- Survival post-expiry: Patentee’s damages claim (Section 108) survives; symmetrically, defendant’s revocation right survives to defeat that claim.
Judgements Including Their Citation and Context Relied by Judge in Reasoning
- Aloys Wobben v. Yogesh Mehra (2014) 15 SCC 360: Heavily relied upon by both sides. The Court reads it contextually — para 26 does not lay down an absolute bar on revocation petitions after suit filing; it applies only where a counter-claim has already been filed (res judicata). Where only Section 107 defence is raised (as here), revocation petition remains maintainable. Paras 25, 26, 27.2 clarify the harmonious reading of Section 64.
- Virgin Atlantic Airways Ltd v. Zodiac Seats UK Ltd [2013] UKSC 46 (UK Supreme Court): Landmark comparative authority. Held that revocation of a patent (under UKPA/EPC) operates retrospectively from grant date; patent treated as never having existed. Applied because Indian statutory scheme (Section 64 + definition of patent) mirrors UK/EPC position. Key passages (Lord Sumption & Lord Neuberger) on in rem effect and policy of Patents Act.
- Ajay Industrial Corporation v. Shiro Kanao of Ibaraki City AIR 1983 Del 496 (DB): Relied on for post-expiry revocation being permissible; transmission to Controller not futile.
- Star Textile Engineering Works Ltd v. James Mackie Holding Ltd 1977 SCC OnLine Cal 280: Cited for proposition that expiry does not bar revocation.
- Dr. Reddys Laboratories Ltd v. Controller of Patents (Single Judge): Distinguished; does not hold that “person interested” ceases post-expiry when damages claim survives.
- Unilin Beheer B.V. v. Balaji Action Buildwell (2018) 76 PTC 194: Distinguished on facts; does not equate Section 107 defence to counter-claim.
- Ramesh Chand Ardawatiya v. Anil Panjwani (2003) 7 SCC 350: Distinguished; not applicable to patent-specific statutory scheme.
- Bishwanath Prasad Radhey Shyam v. Hindustan Metal Industries (1979) 2 SCC 511: On limited nature of grant (used in rejoinder).
Final Decision
The Division Bench dismissed Boehringer’s LPA 129/2025 with no order as to costs. It fully agreed with the Single Judge. Both issues were answered in favour of maintainability of the revocation petition. The revocation petition filed by Macleods can proceed and be adjudicated on merits even after (a) raising Section 107 defence in the Himachal suit, and (b) expiry of IN’301.
Concluding Note
The judgment is a masterclass in statutory interpretation that harmonises the Patents Act’s provisions with legislative intent (Ayyangar Report), practical realities of patent litigation, and international best practices. It rejects hyper-technical attempts to extinguish revocation rights post-expiry or after a defensive plea, emphasising that revocation is a powerful in rem remedy that operates retrospectively to clear the register of invalid grants. By doing so, it safeguards public interest in invalid patents not being used to extract damages or restrain legitimate competition even after expiry.
Legal Points Settled in This Case (Key Takeaways for Patent Law)
- Revocation under Section 64 operates retrospectively (ab initio): If successful, the patent is deemed never to have been granted. It effaces the patent from the register as if the grant was void from inception.
- A “patent” continues to exist for Section 64 purposes even after expiry: The statutory definition (Section 2(1)(m)) is not limited to “patent in force”. Expiry only affects prospective enforceability.
- “Person interested” status survives patent expiry: So long as the petitioner has a real interest (e.g., facing a damages claim), it remains entitled to maintain revocation.
- Section 107 invalidity defence and Section 64 revocation are independent and co-exist: A defendant may raise both; Section 107 is merely defensive (in personam), while revocation is in rem and removes the patent entirely. Only a counter-claim and revocation petition cannot be pursued simultaneously (per Aloys Wobben).
- No multiplicity or conflict issue: The two proceedings operate in different legal spheres; a Section 107 finding does not bar revocation (different consequences under Section 151).
- Damages claim survival is symmetrical: Patentee’s right to past damages (Section 108) survives expiry; defendant’s right to revoke (to defeat that claim) also survives.
- Indian law aligns with UK/EPC on retrospective revocation: Virgin Atlantic principles are persuasive and applicable.
