The Delhi High Court, in Boehringer Ingelheim Pharma GmbH & Co. KG v. Controller of Patents & Anr., considered the maintainability of revocation proceedings under the Patents Act, 1970 in relation to a patent covering the pharmaceutical compound Linagliptin. The dispute arose from a revocation petition filed by Macleods Pharmaceuticals seeking revocation of the patent granted to Boehringer Ingelheim. The appellant challenged the maintainability of the revocation proceedings on the grounds that the respondent had already raised an invalidity defence under Section 107 in a related infringement suit and that the revocation petition could not continue after the patent had expired by efflux of time.

The Court rejected both contentions and upheld the maintainability of the revocation petition. The Court observed that a revocation petition under Section 64 of the Patents Act and an invalidity defence under Section 107 operate in different legal contexts. While an invalidity defence serves as a defence in an infringement suit and operates inter partes, a revocation petition seeks cancellation of the patent from the register and therefore operates in rem.

The Court further held that the expiry of a patent does not render a revocation petition infructuous. It observed that revocation, if granted, would invalidate the patent from the date of grant, and therefore parties accused of infringement retain a legitimate interest in challenging the validity of the patent even after its expiry, particularly in relation to claims for damages during the period when the patent remained in force.

Accordingly, the Court dismissed the appeal and affirmed that revocation proceedings may continue notwithstanding the expiry of the patent or the existence of an invalidity defence in an infringement action.

Source: Boehringer Ingelheim Pharma Gmbh and Co vs The Controller Of Patents & Anr. [LPA 129/2025] Delhi High Court