The Delhi High Court has clarified a critical ambiguity in Indian patent law by holding that a revocation petition under Section 64 of the Patents Act remains maintainable even after the patent in question has expired and even when the petitioner has already raised an invalidity defence under Section 107 in a parallel infringement suit. This judgment resolves long-standing doctrinal uncertainty and redefines the interplay between revocation proceedings and infringement litigation.
Background & Facts
The Dispute
The dispute arose between Boehringer Ingelheim Pharma GmbH & Co KG, the patentee of Indian Patent IN’301 for the drug Linagliptin, and Macleods Pharmaceuticals Limited, a generic manufacturer. Boehringer filed a suit for patent infringement against Macleods in the High Court of Himachal Pradesh. In response, Macleods pleaded invalidity of the patent under Section 107(1) of the Patents Act. Simultaneously, Macleods filed a standalone revocation petition under Section 64 before the Delhi High Court, seeking complete removal of the patent from the register.
Procedural History
- 20 February 2022: Macleods filed the revocation petition under Section 64.
- 17 February 2022: Boehringer filed the infringement suit (Himachal suit) against Macleods.
- 2022 - 2023: Macleods raised Section 107 invalidity defence in the Himachal suit.
- 18 August 2023: Patent IN’301 expired by efflux of time.
- 2024: Boehringer moved applications to dismiss the revocation petition on grounds of patent expiry and Section 107 defence.
- 15 January 2025: A Single Judge of the Delhi High Court dismissed both applications, upholding the maintainability of the revocation petition.
Relief Sought
Boehringer sought dismissal of the revocation petition on two grounds: (1) that revocation cannot be sought after patent expiry, and (2) that a Section 107 defence bars a separate revocation petition. Macleods sought continuation of the revocation petition to obtain a declaration of invalidity ab initio and removal of the patent from the register.
The Legal Issue
The central questions were: (1) Whether a revocation petition under Section 64 of the Patents Act can be maintained after the patent has expired by efflux of time, and (2) Whether the filing of a Section 107 invalidity defence in an infringement suit precludes a separate revocation petition.
Arguments Presented
For the Appellant
Boehringer argued that revocation presupposes a live patent and that once a patent expires, it ceases to be a subject of revocation. It relied on Dr. Reddy’s Laboratories v. Controller of Patents to assert that a "person interested" loses standing post-expiry. It further contended that Section 107 defence and revocation petition are mutually exclusive remedies, citing Aloys Wobben v. Yogesh Mehra to argue that allowing both would lead to multiplicity of proceedings and conflicting outcomes.
For the Respondent
Macleods countered that Section 64 uses the term "patent" without qualification, and the definition in Section 2(m) includes expired patents. It emphasized that revocation operates in rem and ab initio, making it distinct from the in personam effect of a Section 107 defence. It relied on the Ayyangar Committee Report and Virgin Atlantic Airways v. Zodiac Seats to show that revocation annuls the patent from its grant date, and that damages claims survive expiry, preserving the petitioner’s interest. It also distinguished Aloys Wobben as inapplicable since no counter-claim was filed.
The Court's Analysis
The Court undertook a detailed statutory interpretation of Section 64, Section 107, and Section 151 of the Patents Act. It held that the term "patent" in Section 64 must be read in light of its definition in Section 2(m) as "a patent for any invention granted under this Act," which continues to exist even after expiry. The Court rejected the notion that revocation requires a patent to be "in force," noting that the legislature deliberately omitted such a qualification.
"Revocation, if granted, takes effect from the grant of the patent being revoked. It is, therefore, rendered ineffective and incapable of assertion ab initio."
The Court further held that revocation under Section 64 operates in rem and retrospectively, aligning with the European Patent Convention and the UK Patents Act as interpreted in Virgin Atlantic Airways. This retrospective effect means that even an expired patent can be revoked because its validity is challenged from inception.
The Court distinguished Section 107 defence from revocation petition on three key grounds: (1) revocation removes the patent from the register entirely, while Section 107 only defeats the specific infringement claim; (2) revocation triggers an entry in the main Register under Section 151(1), while Section 107 results in a supplemental record under Section 151(2); and (3) revocation has in rem effect, while Section 107 is in personam.
The Court explicitly rejected the argument that Section 107 defence bars a revocation petition, stating that a defence in a written statement cannot extinguish an independent statutory right. It clarified that Aloys Wobben only prohibits simultaneous counter-claim and revocation petition, not Section 107 defence and revocation petition.
The Verdict
The appeal was dismissed. The Court held that a revocation petition under Section 64 of the Patents Act remains maintainable even after the patent has expired and even when a Section 107 invalidity defence has been raised in a parallel infringement suit. The revocation petition may proceed to determine the patent’s validity ab initio, with full in rem effect.
What This Means For Similar Cases
Revocation Is Not Time-Bound by Patent Expiry
- Practitioners may file or continue revocation petitions even after a patent’s term has ended.
- Damages claims in infringement suits survive expiry, preserving the petitioner’s interest as a "person interested" under Section 2(1)(t).
- Patentees cannot use expiry as a shield against revocation challenges.
Section 107 Defence Does Not Preclude Revocation
- A defendant may plead invalidity under Section 107 and simultaneously file a revocation petition.
- The two remedies serve distinct purposes: Section 107 defends against a specific suit; revocation erases the patent from the register entirely.
- Courts must not conflate declaratory defences with statutory revocation.
Revocation Has Retrospective, In Rem Effect
- A successful revocation invalidates the patent from its grant date, not merely from the date of order.
- This affects all past and future infringement claims, including damages and licensing.
- Patent portfolios must be assessed for revocation risk even for expired patents if litigation is pending.
