The Differing Scope Of Revocations And Invalidity Defences In India

Challenges to patents through revocation petitions can be filed independently or as counterclaims in infringement suits. In infringement suits, a defending party has the option to file a revocation petition or argue that the patent itself is invalid. Many questions arise in these contexts, and the Delhi High Court recently had occasion to clarify precisely some of these, concluding that the scope and effect of a revocation petition filed under Section 64 (which deals with revocation) are different from an invalidity defence raised under Section 107 of the Patents Act (‘the Act’).

In Macleods Pharmaceuticals Ltd. vs. The Controller of Patents & Anr. (I.A. 7635/2024 and I.A.46685/2024 IN C.O.(COMM.IPD-PAT)38/2022), the Court addressed two issues: firstly, whether a revocation petition is maintainable if the petitioner has filed a written statement, taking defence of the patent’s invalidity under Section 107 in an infringement suit; and secondly, whether a revocation petition can be filed or sustained (if already filed) after the patent has expired.

Background

Macleods Pharmaceuticals Ltd. (‘the petitioner’) filed a revocation petition against Boehringer Ingelheim Pharma GmbH & Co. KG’s (‘the respondent’) Patent IN 243301 in respect of the anti-diabetic drug ‘Linagliptin’ on February 17, 2022. The revocation petition was filed just before the commercial launch of the petitioner’s generic product on February 22, 2022. Thereafter, on February 19, 2022, the respondent filed an infringement suit against the petitioner before the High Court of Himachal Pradesh. The term of the patent expired on August 18, 2023.

In the meantime, the respondent submitted several applications. The first application sought to dismiss the revocation petition on grounds that the petition was filed 12 years after the patent was granted. The second application requested the revocation petition to be transferred to the High Court of Himachal Pradesh to be consolidated with the Himachal Suit. The third application contended that since the patent expired in 2023, the revocation petition was now moot and should be dismissed. Subsequently, the petitioner filed a transfer petition before the Supreme Court seeking the transfer of the Himachal suit to the Delhi High Court, which is pending.

The Delhi High Court’s decision

In its detailed analysis, the Delhi High Court observed that the scope of a revocation petition under Section 64 and the defence of invalidity under Section 107 are different for the following reasons:

1. A revocation petition can be filed either as a stand-alone or by a counter-claim in an infringement suit, and only a High Court has the authority to entertain such petitions. On the other hand, patent infringement suits and defences under Section 107 can be adjudicated by a District Court.
2. Once a revocation petition is successful, the patent is effaced from the Register of Patents as if it never existed, whereas a finding of invalidity of claims under Section 107 requires a defendant to take additional steps under Section 71(1) of the Act for rectification of the register. Hence, a finding of invalidity by itself would not result in the removal of the patent from the register.
3. In a revocation proceeding, if the patent is deemed invalid, the patentee may amend the complete specification instead of having the patent revoked. On the other hand, based on the defence taken under Section 107 of the Patents Act, a court cannot direct the patentee to amend the claims.
4. Once a patent is revoked by the High Court, it would operate in rem, and the patentee would not be able to assert the patent or claims against any third party. On the contrary, the findings in an infringement suit between contesting parties operate in persona and will only bind the contesting parties.
5. A party has the choice to either file a revocation petition or a counterclaim in a pending suit, and there is no limitation in the Act that restricts this choice.

Based on these reasons, the court concluded that a defence of invalidity in an infringement suit does not equate to a revocation of the patent; hence, the present revocation petition is maintainable.

On the issue of revocation after the patent’s expiry, the court said that the expiration of the patent term does not render the infringement suit infructuous, as the cause of action and damages still survive. The court further observed that the petitioner had a valid cause of action to continue with the revocation petition, and the patent’s expiration did not make the petition irrelevant, considering its possible effect on the ongoing infringement case.

Given these findings, the Delhi High Court dismissed the objections taken by the respondent concerning the maintainability and sustainability of the revocation petition.

Conclusion

This decision clarifies the different legal consequences and procedures of filing an invalidity defence under Section 107 of the Patents Act and filing a revocation petition under Section 64 of the Patents Act. Additionally, it affirms that if an infringement lawsuit seeking damages is still pending, a revocation petition can be maintained even after the patent has expired. For parties defending themselves in infringement suits or seeking to file revocations against patent holders, this decision offers considerable clarity on strategy, timing, and maintainability.