Patent Revocation After Expiry: What the Boehringer Judgment Settles

Issues

Two questions arose for determination:

First, whether a revocation petition under Section 64 of the Patents Act 1970 can be instituted or can survive after the petitioner has pleaded invalidity of the same patent as a defence under Section 107(1) in an infringement suit.

Second, whether a revocation petition can be instituted or continued after the patent of which revocation is sought has expired by efflux of time.

Both questions were answered in the affirmative. In resolving the second, the Division Bench also settled a point that Indian courts had not previously addressed: whether revocation under Section 64 operates retrospectively from the date of grant.

Facts

Indian Patent IN 243301 was granted to Boehringer Ingelheim on 5 October 2022 for the pharmaceutical product Linagliptin, with a priority date of 21 August 2002. On 17 February 2022, Macleods Pharmaceuticals filed a revocation petition under Section 64(1) before the Delhi High Court. Two days later, on 19 February 2022, Boehringer filed an infringement suit against Macleods in the High Court of Himachal Pradesh, seeking an injunction and damages. In its written statement, Macleods pleaded invalidity of IN 243301 under Section 107(1).

IN 243301 expired by efflux of time on 18 August 2023.

Boehringer filed two interlocutory applications seeking dismissal of the Delhi revocation petition: the first on the ground that the petition could not survive patent expiry; the second on the ground that Macleods’ Section 107 plea extinguished its right to maintain a separate revocation action. A Single Judge dismissed both on 15 January 2025. Boehringer appealed. The Division Bench heard the matter on 26 November 2025 and pronounced judgment on 24 February 2026.

Holdings

The Division Bench, comprising Justice C. Hari Shankar and Justice Om Prakash Shukla, dismissed the appeal and held that:

(i) A revocation petition under Section 64 remains maintainable and continues to survive even after the patent of which revocation is sought expires by efflux of time; and

(ii) A revocation petition can be instituted or continued even after the defendant in an infringement suit has taken an invalidity defence under Section 107(1).

Retrospective Effect of Revocation

The Patents Act 1970 does not expressly state whether a successful revocation order takes effect from the date of the order or from the date of original grant. The Division Bench resolved this gap through three lines of reasoning.

Section 64 parity. Section 64(1) places a standalone revocation petition and a counter-claim in an infringement suit on identical footing: both operate under the provision and both produce revocation. A counter-claim must seek invalidity from the date of grant, because the infringement damages claimed in the suit pre-date the suit itself. If both remedies lead to the same outcome, revocation must in either case invalidate the grant from its origin.

Nature of revocation grounds. Every ground on which revocation may be sought under Section 64 (lack of novelty, obviousness, prior secret use, misrepresentation in the application, non-disclosure under Section 8, and the others), if established, demonstrates that the original grant was itself invalid. There is no ground for revocation that operates only prospectively.

International authority. The court drew on Virgin Atlantic Airways Ltd v. Zodiac Seats UK Ltd [2013] UKSC 46 (UK Supreme Court, 3 July 2013). Article 68 of the European Patent Convention provides that a revoked European patent shall be deemed not to have had, from the outset, the effects it conferred. The Division Bench found the statutory position under the Indian Patents Act to be materially analogous and applied the principle: revocation acts in rem and retrospectively from the date of grant.

Note: The Delhi High Court’s footnote cited [2009] EWCA Civ 1062, the Court of Appeal stage of the same litigation. The landmark authority on retrospective revocation is the UK Supreme Court decision at [2013] UKSC 46, which reversed the Court of Appeal on the damages question.

Maintainability Post-Expiry

Boehringer contended that revoking an expired patent was, in the words of its Senior Counsel, characterised as redundant (“flogging a dead horse”). The court rejected this on statutory and practical grounds.

Statutory construction. Section 2(m) defines “patent” as “a patent for any invention granted under this Act.” The operative word is “granted.” Expiry renders a patent unenforceable going forward; it does not deprive it of the character of a granted patent. Section 64 uses “a patent,” not “a patent in force.” The legislature knew the distinction: Section 2(o) uses “in respect of which a patent is in force” when defining “patented article.” Parliament’s deliberate choice of a broader formulation in Section 64 cannot be overridden by judicial implication. A court cannot supply casus omissus.

Mootness rejected. Ordinary civil law treats a proceeding as infructuous where the subject matter no longer exists and no enforceable legal consequence can follow. Patent law departs from this principle where revocation operates retrospectively. Because a successful revocation invalidates the patent from the date of grant, it extinguishes the patentee’s right to claim damages for infringement during the patent’s lifetime. The legal consequence is not historical but live: it directly defeats a pending damages claim. The proceeding is therefore not moot.

Continuing locus standi. Section 64(1) limits petitioners to a “person interested.” Section 2(1)(t) defines the expression to include a person engaged in, or promoting, research in the same field. The court gave the provision its natural breadth: the test is whether the petitioner has a real and live interest in the revocation succeeding. A defendant in a pending infringement suit where the plaintiff presses for damages and an account of profits has exactly that interest. Macleods’ exposure to monetary liability in the Himachal suit was directly contingent on the patent’s validity from the date of grant. That continuing exposure sustained its locus standi regardless of the patent’s expiry.

Section 64 and Section 107: Distinct Remedies

The court identified three structural differences that preclude any overlap between a revocation petition and an invalidity defence.

Effect on the Register. A successful revocation petition removes the patent entirely from the Register of Patents and invalidates it ab initio. It operates in rem, against the world. A successful Section 107 invalidity defence results only in dismissal of the infringement suit. The patent remains on the Register. The patentee retains the right to assert it against third parties who were not party to that suit.

Administrative consequence. Section 151(1) requires every revocation order to be transmitted to the Controller for entry in the Register of Patents. Section 151(2) requires the court hearing an invalidity defence to transmit its decision to the Controller for entry only in a supplemental record. The patent’s entry in the Register of Patents is unaffected by a Section 107 finding.

Juridical character. A revocation under Section 64 operates in rem, binding the world. A finding under Section 107 operates in personam, binding only the parties to the suit. The Ayyangar Committee Report that preceded the Patents Act explicitly recommended this bifurcated architecture: invalidity defences in suits were to have inter-partes effect only, while revocation petitions before the High Court were to produce a result “beyond the immediate parties.”

No principle of civil procedure permits a written statement defence to extinguish a party’s independent right to pursue a broader remedy in separate proceedings. A defendant who may file a counter-claim may equally file a revocation petition in its place. Both lie under Section 64. The Section 107 defence, being neither, leaves both options intact.

Interpretation of Aloys Wobben v. Yogesh Mehra

Boehringer placed significant reliance on paragraph 26 of the Supreme Court’s decision in Aloys Wobben v. Yogesh Mehra (2014) 15 SCC 360, which states that revocation petitions filed after the institution of an infringement suit “would be unsustainable in law.” The Division Bench confined that observation to its actual context.

In Aloys Wobben, Enercon had filed twenty-three revocation petitions before the Intellectual Property Appellate Board (the tribunal with jurisdiction at that time) and had simultaneously prosecuted a counter-claim in the infringement suit seeking revocation of the same patents on identical grounds. The Supreme Court applied the principle against res judicata: a party may not pursue the same relief in two simultaneous proceedings before different fora. The words “as such” in paragraph 26 expressly link the prohibition to that specific antecedent scenario: a defendant who had already filed a counter-claim in the suit. Paragraph 26 is not a free-standing rule barring all revocation petitions after an infringement suit is instituted.

In the present case, Macleods had not filed a counter-claim. Its revocation petition was filed two days before Boehringer’s infringement suit. Under paragraph 27.2 of Aloys Wobben, Macleods was in fact precluded from filing a counter-claim in the Himachal suit. That is precisely why the revocation petition before the Delhi High Court had to proceed.

Structural significance. This judgment addresses a tactical risk that previously threatened the integrity of patent revocation as a remedy. A patentee facing revocation proceedings could, by pressing an infringement suit to its natural end and allowing the patent to lapse, have argued that the revocation petition was extinguished. The court’s ruling eliminates that possibility. Validity is the foundation of a damages claim; revocation proceedings that defeat validity therefore remain live for as long as a damages claim is asserted. The judgment also resolves the procedural independence of the three available remedies: Section 64 revocation petition, Section 64 counter-claim, and Section 107 invalidity defence. They are not substitutes for each other and do not exhaust each other.

Practical Implications

Three operational consequences follow for defendants in patent infringement suits.

A defendant who filed a standalone revocation petition before the infringement suit was instituted cannot file a counter-claim in the suit seeking the same relief. Aloys Wobben is clear on this. The revocation petition must proceed. A Section 107 invalidity defence in the infringement suit may run alongside the revocation petition. The two are not mutually exclusive.

A defendant served with an infringement suit after having already filed a revocation petition does not need to convert it into a counter-claim. The revocation petition runs independently. The Section 107 plea in the suit does not displace it.

Patent expiry does not close the revocation route where the patentee’s damages claim remains alive. A defendant who obtains revocation ab initio eliminates the legal foundation for those monetary claims entirely. The revocation petition becomes more consequential after expiry, not less.

Citation: Boehringer Ingelheim Pharma GmbH & Co. KG v. The Controller of Patents & Anr., LPA 129/2025, CM APPL. 10551/2025, High Court of Delhi (Division Bench), pronounced 24 February 2026.