Patent Revocation Petitions Survive Expiry of Patent Term and Simultaneous Defensive Pleas of Invalidity

The Appellant, Boehringer, was granted Indian Patent (IN) 243301 for the drug 'Linagliptin'.

In February 2022, the Respondent, Macleods, filed a revocation petition under Section 64(1) of the Patents Act.

Two days later, Boehringer sued Macleods for infringement in the Himachal Pradesh High Court, where Macleods pleaded invalidity of the patent as a defense under Section 107(1).

During the pendency of the revocation petition, the patent expired by efflux of time on August 18, 2023.

Boehringer sought dismissal of the revocation petition, arguing it was no longer maintainable because the patent had expired and because Macleods had already raised an invalidity defense in the infringement suit.

The Single Judge dismissed Boehringer’s applications, leading to this appeal.

1. Whether a revocation petition under Section 64 can be instituted or survive after the petitioner has pleaded invalidity of the same patent as a defense under Section 107(1) in an infringement suit.

2. Whether a revocation petition can be instituted or continue after the patent of which revocation is sought has expired.

The Court interpreted Section 64 of the Patents Act, 1970, which allows "any person interested" to seek revocation of a patent.

It contrasted this with Section 107(1), which allows invalidity as a defense in infringement suits.

The Court relied on the definition of "patent" in Section 2(m) and "person interested" in Section 2(1)(t).

It applied the principle that revocation acts *in rem* and retrospectively (ab initio), drawing from the UK Supreme Court decision in *Virgin Atlantic Airways Ltd v. Zodiac Seats UK Ltd* and Distinguished the Indian Supreme Court ruling in *Aloys Wobben v. Yogesh Mehra*, which prohibits simultaneous pursuit of a revocation petition and a counter-claim, but not a Section 107 defense.

The Court reasoned that revocation under Section 64 is fundamentally different from a Section 107 defense; while the former can efface a patent from the register *in rem*, the latter is an *in personam* defense that merely results in the dismissal of a specific suit.

Section 151 further highlights this distinction by requiring different registrar entries for each.

Regarding expiry, the Court held that "revocation" operates retrospectively to the date of grant; therefore, a "person interested" retains a stake in revoking an expired patent to shield themselves from past liability—such as claims for damages/account of profits—accrued during the patent's life.

The Court clarified that *Aloys Wobben* only bars a revocation petition if a **counter-claim** (not just a Section 107 defense) is filed in a suit.

Since a patent remains "a patent granted under the Act" even after expiry per Section 2(m), the statutory right to seek its annulment survives.

It held that: (i) a revocation petition is maintainable even after a Section 107 invalidity defense is raised because the two remedies operate in different spheres and have different legal consequences; and (ii) a revocation petition survives the expiry of a patent because revocation acts *ab initio*, and the petitioner remains a "person interested" to contest potential claims for past damages.

The Single Judge's order was upheld.