Delhi High Court Clarifies Maintainability of Revocation Petitions Beyond Patent Expiry

Introduction

The instant commentary examines the Delhi High Court’s Judgment in the case of Macleods Pharmaceuticals Ltd. v. The Controller of Patents & Anr. (C.O.(COMM.IPD-PAT) 38/2022), pronounced on January 15, 2025. The dispute centers on whether a petition for revocation of a patent (filed under Section 64 of the Indian Patents Act, 1970) can be pursued even after the patent has expired and while a separate infringement suit, filed by the patentee seeking damages, remains pending.

The action was triggered when Macleods Pharmaceuticals Ltd. (“Petitioner”) sought to revoke the patent belonging to Boehringer Ingelheim Pharma GmbH & Co. KG (“Respondent No.2”). The patent in question, Indian Patent No. IN 243301 concerning “LINAGLIPTIN” (an anti-diabetic drug), expired during the pendency of the revocation proceedings, leading the respondent to challenge the maintainability of the revocation petition post-expiry.

This Judgment is significant because it clarifies the extent to which revocation petitions can be maintained after patent expiry, shedding light on important distinctions between a defense of invalidity in an infringement suit under Section 107 and a stand-alone petition for revocation under Section 64 of the Patents Act, 1970.

Summary of the Judgment

The Court dealt with two applications filed by Respondent No.2—both seeking dismissal of the petitioner’s revocation plea. The primary contentions were:

  1. The revocation petition allegedly became infructuous due to the expiry of the patent on August 18, 2023.
  2. The petitioner had already taken a defense of invalidity under Section 107 of the Patents Act in a patent infringement suit pending before the High Court of Himachal Pradesh.

The Delhi High Court, in a detailed analysis, rejected the applications and held that the revocation proceeding was maintainable even after patent expiry. Crucially, the Court found that the relief sought in a Section 64 revocation petition is different from a Section 107 invalidity defense. The Court also observed that, because the patentee may still have a live claim for damages, the alleged infringer retains a cognizable stake in obtaining a full revocation to eliminate liability and remove the patent from the register.

Consequently, the Court dismissed both applications by Respondent No.2 and allowed the revocation petition to proceed. The matter was listed for further proceedings in February 2025.

Analysis

Precedents Cited

The Judgment referenced the case of Dr. Reddys Laboratories Limited & Anr. v. Controller of Patents & Ors., 2022 SCC OnLine Del 1040, highlighting the meaning of “person interested” under Section 2(1)(t) of the Patents Act. While Respondent No.2 sought to rely on this precedent to argue that revocation petitions must be filed only during the life of the patent, the Delhi High Court clarified that the question of limitation in revocation proceedings is distinct from the timing of the attempt to revoke a patent.

The Court noted that once a party is deemed a “person interested”—for instance, by virtue of manufacturing a potentially infringing product—it preserves the right to seek revocation, regardless of the patent’s remaining term. Moreover, the Court distinguished these circumstances from scenarios that do not involve a pending infringement case or potential damages claim.

Legal Reasoning

The Court’s detailed reasoning flowed from a meticulous reading of Sections 64, 107, and 151 of the Patents Act:

  • Section 64 (Revocation of Patent): This provision allows a “person interested” to revoke a patent or, alternatively, invoke it by way of a counterclaim in an infringement suit. Revocation is entirely within the purview of the High Court, and if granted, the patent is “effaced” from the register as if it never existed.
  • Section 107 (Defenses in Infringement Suits): The invalidity defense can be taken up even in a District Court, unlike a revocation petition, which must necessarily be pursued before a High Court. A successful invalidity defense in an infringement action paves the way for follow-up proceedings under Section 71 to remove the patent from the register, making the effect of Section 107 conceptually narrower compared to a direct revocation order under Section 64.
  • Section 151 (Transmission of Orders): The Court carefully distinguished the transmission of a High Court’s revocation order to the Controller (which results in an immediate and complete removal of the patent from the register) from the transmission of an adverse finding on validity in an infringement suit (for which further rectification steps are required).

Since both infringement and revocation had already been initiated in separate fora, the Court reasoned that the petitioner was fully entitled to maintain the standalone revocation petition under Section 64. Even if the patent term lapsed, the patentee’s claims for damages in the separate infringement suit remained live, preserving the petitioner’s interest in revoking the patent.

Impact

The Judgment clarifies that defendants accused of infringing an expired patent—where a claim for past damages persists—can continue or institute revocation proceedings, ensuring the possibility of complete invalidation of the patent. This outcome:

  1. Eliminates any remaining damages liability if the patent is ultimately revoked.
  2. Avoids procedural inefficiencies by confirming that a revocation petition can run parallel to or outlive an infringement defense, if substantive grounds exist.
  3. Reinforces that no statutory deadline bars filing revocation petitions under Section 64, as recognized in prior precedents and reiterated here.

For practitioners, the Judgment serves as an authoritative statement on pursuing revocation past patent expiry—emphasizing the distinct legal consequences of Section 64 (revocation) and Section 107 (invalidity) in the patent enforcement and defense regime.

Complex Concepts Simplified

Below is a simpler explanation of the key concepts addressed in this Judgment:

  • “Person Interested” (Section 2(1)(t)): Anyone who is involved in or contemplates making or selling something that could infringe a patent can be regarded as a “person interested.” This legal status grants them the right to file or maintain a revocation petition.
  • Revocation vs. Invalidity Defense: A revocation under Section 64 immediately removes the patent from the register (acting “in rem”), while an invalidity defense under Section 107 is a personal defense in an infringement action (acting “in personam”) and requires additional steps under Section 71 before the patent is formally removed from the register.
  • Effect of Patent Expiry: While a patent typically cannot be enforced for prospective relief (injunction) after expiration, monetary claims (like damages or accounts of profits) for past infringement remain viable. Hence, a revocation petition can still be relevant, as it can negate those claims if the patent is judicially declared invalid.
  • Parallel or Subsequent Actions: Even if an infringement suit is filed in one High Court or District Court, a separate petition for revocation under Section 64 can be filed—and remain maintainable—in another High Court, because the law confers a choice upon the alleged infringer.

Conclusion

The Delhi High Court’s Judgment underscores the autonomy and distinct legal consequences of revocation (Section 64) versus invalidity defenses (Section 107) and reconfirms that patent expiry does not extinguish the right to seek revocation—especially where the patentee asserts post-expiry damages. It clarifies that an invalidity finding in an infringement proceeding does not automatically remove the patent from the register, whereas a revocation order from the High Court does.

Hence, Macleods Pharmaceuticals Ltd. v. The Controller of Patents & Anr. is an instructive precedent on how courts may treat parallel or sequential proceedings related to the same patent, and it ensures that valid defences and counter-claims remain open even if the patent’s term has ended. In a broader legal context, it provides robust guidance for parties seeking to protect or challenge patent rights under the Indian Patents Act and confirms the continuing importance of revocation paths irrespective of patent expiry.