Introduction
The court examined whether a party can still seek revocation of a patent after raising an invalidity defence in an ongoing infringement suit and whether such revocation proceedings can continue once the patent itself has expired. This judgment balances the rights of patent holders with the interests of those who challenge questionable grants, ensuring that justice in patent matters does not end simply because time runs out on the patent term. By affirming that revocation petitions remain alive in both scenarios, the court has strengthened the mechanism for cleaning up the patent register and protecting public interest in genuine innovation.
Key Issues Considered
- Whether revocation can be sought after raising an invalidity defence in an infringement suit
- Whether revocation proceedings survive after expiry of the patent
- Balancing patent holder rights with public interest in innovation
Factual Background
The dispute centred on an Indian patent granted to a German pharmaceutical company for a medicine used in treating diabetes. A generic drug manufacturer, concerned about the validity of this patent, filed a revocation petition before the Delhi High Court seeking to cancel it. Just two days later, the patent holder filed an infringement suit in the High Court of Himachal Pradesh, claiming the generic company was violating its rights and seeking an injunction. In its written statement filed in the Himachal suit, the generic manufacturer raised a defence that the patent was invalid. Meanwhile, the patent expired in the normal course after its full term. The patent holder then moved applications in the Delhi revocation proceedings urging that they should be dismissed because the challenger had already taken an invalidity defence in the suit and because the patent was no longer in force.
Timeline of Events
| Stage | Event Description |
|---|---|
| Patent Grant | Patent granted to German pharmaceutical company for diabetes medicine |
| Revocation Petition | Generic manufacturer filed revocation petition before Delhi High Court |
| Infringement Suit | Patent holder filed suit in Himachal Pradesh High Court |
| Invalidity Defence | Generic manufacturer raised invalidity defence in written statement |
| Patent Expiry | Patent expired after completion of its statutory term |
| Applications Filed | Patent holder sought dismissal of revocation proceedings |
Procedural Background
The single judge of the Delhi High Court heard the matter and rejected both applications filed by the patent holder. This meant the revocation petition was allowed to proceed despite the invalidity defence in the parallel suit and despite the patent having expired. Feeling aggrieved, the patent holder approached the Division Bench in appeal, arguing that once a defence of invalidity is taken in the infringement suit, a separate revocation petition cannot survive, and that revocation becomes meaningless after the patent dies a natural death. Extensive arguments were advanced by senior counsel on both sides, with an amicus curiae also assisting the court. The Division Bench carefully examined the statutory provisions, earlier judgments, and international practices before delivering its verdict.
Procedural Highlights
- Single Judge rejected applications seeking dismissal of revocation petition
- Revocation proceedings allowed despite parallel invalidity defence
- Appeal filed before Division Bench
- Arguments presented by senior counsel and amicus curiae
- Court examined statutory framework, precedents, and international practices
Reasoning And Decision Of Court
The court began by emphasising that revocation of a patent is not a forward-looking remedy but one that looks backward to the very grant of the patent. When a patent is revoked, it is treated as if it had never been valid from the day it was granted. This retrospective effect means the patent is wiped off the register completely, and no rights can be asserted under it at any time.
- The patent is treated as never having existed legally.
- All rights arising from the patent stand extinguished.
- The patent is removed entirely from the register.
Because of this nature of revocation, the mere expiry of the patent by passage of time does not end the need to examine its validity. Even after expiry, the patent holder may still claim damages for past infringements, and the challenger therefore retains a real and continuing interest in getting the patent cancelled from its root.
Status Of Patent After Expiry
The judges explained that the law treats a patent as remaining a “patent” even after its term ends, for the purpose of deciding whether it was properly granted in the first place. The person filing the revocation petition continues to be a “person interested” because success in revocation would directly affect the damages claim in the infringement suit.
- The patent retains legal relevance even after expiry.
- The petitioner remains a “person interested”.
- Revocation directly impacts infringement claims.
The court drew support from established principles in other jurisdictions where revocation is understood to operate from the date of grant and affects everyone, not just the parties in one case.
Invalidity Defence Vs Revocation
On the question of raising an invalidity defence in the infringement suit, the court found a clear distinction between that defence and a full revocation petition. The defence is limited to protecting the defendant in that particular suit and does not remove the patent from the register for the world at large.
| Aspect | Invalidity Defence | Revocation Petition |
|---|---|---|
| Scope | Limited to the specific suit | Applies universally |
| Effect | Protects defendant only | Removes patent from register |
| Outcome | No wider legal impact | Permanent cancellation |
Revocation, on the other hand, is a broader remedy that cleans the register permanently. The court clarified that a party can raise the invalidity defence in its written statement and still pursue a separate revocation petition, as the two remedies serve different purposes and operate in different spheres.
Relying on a Supreme Court precedent often cited in such matters, the Division Bench explained that the earlier ruling only prevents a party from running both a counter-claim for revocation and a separate revocation petition at the same time. Since no counter-claim had been filed in this case and only a defence was raised, there was no legal bar to continuing the revocation petition.
Final Decision
After a detailed examination of all arguments, the Division Bench fully agreed with the view taken by the single judge. It held that the revocation petition was maintainable and could continue despite the patent having expired and despite the invalidity defence taken in the parallel suit. The appeal was accordingly dismissed, allowing the revocation proceedings to move forward on merits.
Point Of Law Settled In The Case
This judgment settles, in clear and unambiguous terms, that revocation petitions under Indian patent law remain alive and maintainable even after the patent expires by efflux of time and even after the challenger has raised an invalidity defence in an infringement suit filed by the patent holder.
- Revocation operates retrospectively from the date of grant.
- Expiry of patent does not extinguish challenge rights.
- Invalidity defence and revocation can coexist.
- Both remedies operate in distinct legal spheres.
The ruling underscores that revocation operates retrospectively to invalidate the grant from its very inception, and the interest of the challenger does not vanish merely because the patent term ends. It also draws a sharp line between a limited defence in a suit and the wider remedy of revocation, confirming that both can coexist without creating any legal conflict.
The decision brings harmony between the statutory provisions and practical realities of patent litigation, ensuring that questionable patents can still be challenged effectively even after their natural life ends.
Case Details
| Case Title | Boehringer Ingepheim Gmbh Vs Controller Of Patent And Another |
|---|---|
| Date Of Order | 24 February 2026 |
| Case Number | LPA 129/2025 |
| Neutral Citation | 2026:DHC:1609-DB |
| Name Of Court | High Court Of Delhi |
| Name Of Hon’ble Judges | Hon’ble Mr. Justice C. Hari Shankar And Hon’ble Mr. Justice Om Prakash Shukla |
Disclaimer: Readers are advised not to treat this as substitute for legal advise as it may contain errors in perception, interpretation, and presentation.
Written By: Advocate Ajay Amitabh Suman, IP Adjutor [Patent and Trademark Attorney], High Court of Delhi
