By Jigyasa Pareek

The Delhi High Court, on January 15, 2025, delivered a judgment in the case of Macleods Pharmaceuticals Ltd. vs The Controller of Patents & Anr. [C.O.(COMM.IPD-PAT) 38/2022] addressing two key issues: (i) maintainability of a revocation petition when the petitioner has already raised a defence of invalidity (in an infringement suit) under Section 107 of the Patents Act, 1970, in a pending patent infringement suit, and (ii) sustainability of a revocation petition filed after the patent’s term has expired.

In the instant case, Macleods Pharmaceuticals Ltd. filed a revocation petition under Section 64(1) of the Patents Act, seeking revocation of Indian patent number 243301, owned by Boehringer Ingelheim Pharma GmbH & Co. KG. The contested patent related to Linagliptin, a drug for treating diabetes. The subject patent expired on August 18, 2023.

The revocation petition was filed by Macleods before the Delhi High Court on February 17, 2022, just before launching their generic version of Linagliptin. Following this, on February 19, 2022, Boehringer filed an infringement suit against Macleods before the Himachal Pradesh High Court, alleging infringement of the subject patent. Thereafter, Macleods filed a transfer petition before the Supreme Court seeking transfer of the infringement suit pending before the Himachal Pradesh High Court to the Delhi High Court. The transfer petition is currently pending.

Boehringer filed two applications before the Delhi High Court seeking dismissal of the revocation petition, arguing (i) that the revocation petition had become irrelevant after the expiry of the subject patent, and (ii) that Macleods had already raised a defence of invalidity under Section 107 in the ongoing infringement suit before the Himachal Pradesh High Court. These arguments were centred on the following points:

• Duplicate and potentially conflicting proceedings: Boehringer argued that the defence of invalidity raised by Macleods in the infringement suit was substantially similar to the revocation petition, and pursuing both could result in conflicting judgments from two different Courts.
• Effect of invalidity finding in infringement suit: Boehringer contended that a finding of invalidity in an infringement suit is legally binding on the patentee and prevents the enforcement of the patent, regardless of whether a revocation petition had been filed. They argued that a decision on the validity or invalidity of a patent—whether in a revocation petition, counterclaim, or infringement suit—is a decision in rem, which applies universally to all persons and conclusively resolves the rights and obligations related to the patent.
• Comprehensive nature of infringement suit: Boehringer argued that the infringement suit, being more comprehensive and involving evidence from both parties, would render the revocation petition redundant.
• Not a ‘person interested’ after patent’s expiry: Boehringer claimed that since the patent had expired, Macleods could no longer be considered a ‘person interested’ under Section 2(1)(t) of the Patents Act.

Macleods countered Boehringer’s arguments with the following points:

• Effect of revocation vs invalidity defence: Macleods differentiated between the proceedings under Section 64 and the defence of invalidity under Section 107, emphasising that the issue of revocation falls under the jurisdiction of the High Court, while invalidity can be decided by any competent District Court since the ground of invalidity is raised as a defense under Section 107 in an infringement suit, which can be instituted before a competent District Court as per Section 104.
• Independent nature of revocation petition: Macleods argued that a revocation petition under Section 64 has a different consequence from the defence of invalidity under Section 107 in an infringement suit because Section 107 does not entitle a defendant to seek revocation, it only enables the defendant to seek a declaration that one or more claims of a patent are invalid and the patent is liable to be revoked.
• Scope of a revocation petition: Macleods argued that a revocation petition leads to removal of the patent from the Register of Patents, as if it never existed, impacting the entire patent. In contrast, a defence of invalidity may be raised in respect of individual claims of a patent. 
• Validity of claims in an infringement suit: Macleods argued that despite the fact that certain claims may be invalidated in a patent infringement suit, the valid claims could still be asserted against third parties under Section 114 of the Patents Act.
• Right to file a revocation petition independently: Macleods argued that Section 64 provides an independent right which can be exercised regardless of whether an infringement suit has been filed. Furthermore, they pointed out that there is no prescribed time limit for availing the rights under Section 64, meaning the rights can be exercised at any time, even if the patent has expired.
• ‘Person interested’ status after patent expiry: Macleods argued that revocation petition could be pursued even after the patent for which revocation is sought has expired, similar to an infringement proceeding, as the cause of action is not extinguished by the expiration of the patent.

The key findings of the Delhi High Court are as follows: 

• On the maintainability of the revocation petition

The Court clarified that the scope of a revocation petition under Section 64 is different from a defence of invalidity under Section 107 in an infringement suit. The Court reasoned that:

• A revocation petition can be filed either as a stand-alone petition or as a counter-claim in a patent infringement suit.
• The authority to hear a revocation petition is vested exclusively in the High Court. In contrast, under Section 104 of the Patents Act, a patent infringement suit can be adjudicated by a District Court. Therefore, the defence under Section 107 can also be adjudicated by a District Court. However, if a counter-claim for revocation of the patent is raised by the defendant in an infringement suit, the proviso to Section 104 mandates that the suit, along with the counter-claim, must be transferred to the High Court for adjudication.
• A finding of invalidity of a patent by itself does not result in removal of the patent from the Register of patents and requires the defendant to take additional steps under Section 71(1) of the Patents Act for rectification of the Register. On the other hand, once a revocation petition is allowed, the patent is effaced from the Register as if it never existed.
• Under Section 58(1) of the Patents Act, if the High Court determines that a patent is invalid in a revocation proceeding, it has the option to allow the patentee to amend the complete specification of the patent instead of revoking the patent. However, when a defence of invalidity is raised under Section 107, the Court does not have the authority to direct the patentee to amend the claims of the patent.
• A revocation petition under Section 64, when successful, has an “in rem” effect. This means that the decision applies universally, irrespective of the parties involved. In contrast, a finding of invalidity in a patent infringement suit is “in personam”, binding only the parties to the suit. A ruling of invalidity does not automatically remove the patent from the Register or prevent the patentee from asserting it against other parties.
• It is the prerogative of a party to choose whether to file a stand-alone revocation petition under Section 64 or to file a counter-claim in an ongoing infringement suit. The Patents Act does not impose any limitation on this choice. Therefore, the petitioner retains an independent right under Section 64 to file a revocation petition.

The Court noted that, in the instant case, Macleods had filed the revocation petition before the infringement suit was instituted, and the fact that Macleods had raised a defence of invalidity in the infringement suit did not bar the filing of the revocation petition. Regarding the possibility of conflicting judgments from two different High Courts, the Court observed that the transfer petition filed by Macleods was under consideration by the Supreme Court. The Court, therefore, concluded that the revocation petition was maintainable and there was no legal basis to dismiss it on the ground of a pending infringement suit.

• On the sustainability of the petition after the patent’s expiry

The Court highlighted that, as per Section 64, a revocation petition can be filed either by (i) a person interested or (ii) the Central Government. Regarding “person interested” under Section 2(1)(t) of the Patents Act, the Court reaffirmed the interpretation by a co-ordinate Bench in Dr. Reddys Laboratories Limited and Anr. v. Controller of Patents and Ors., 2022 SCC OnLine Del 1040, to include any person (i) who seeks to manufacture or sell the patented invention, (ii) against whom an infringement suit is filed, or (iii) who is interested in the invention covered by the patent in any other manner.

The Court noted that in the instant case, Macleods qualified as a “person interested” under Section 2(1)(t) because Macleods sought to manufacture and sell the patented drug and was also involved in an ongoing infringement suit concerning the same patent.

The Court held that the cause of action for damages or revocation persists even after the patent expires. Similar to how a patent holder can seek damages for the infringement of an expired patent, a petition for revocation can be filed or will survive even after the patent has expired. Section 64 does not prescribe any limitation thereof, and no limitation can be read into it. The Court remarked that Macleods had a valid cause of action to pursue the revocation petition, particularly since the outcome of the revocation proceedings could directly influence the ongoing infringement suit.

The Court concluded that the revocation petition was not barred by limitation.

In view of the above findings, the Delhi High Court dismissed the objections raised by Boehringer regarding the maintainability and sustainability of the revocation petition.