Delhi HC Clears Way for Post-Expiry Patent Revocation

Delhi HC Clears Way for Post-Expiry Patent Revocation. The recent decision of the Delhi High Court marks a significant shift in Indian patent jurisprudence the Court has affirmed that a revocation petition under Patents Act, 1970 may be maintained even after the statutory term of the patent has expired. Traditionally, once a patent lapsed its term, it was widely assumed to have entered the public domain and thus immune from revocation actions. However, the Court has clarified that expiry does not automatically render revocation proceedings moot if there remains a valid cause of action such as ongoing claims for damages under a pending infringement suit. The judgment emphasizes the legal distinction between a revocation petition (under Section 64) and an invalidity defense in an infringement suit (under Section 107). A revocation petition which, if successful, removes the patent from the Register as though it never existed is materially different in purpose and effect from raising invalidity in a suit, which binds only the parties involved. By doing so, the Court has opened the door for post-expiry challenges to patents, ensuring that even once a patent’s term has lapsed, its validity can still be tested under appropriate circumstances. This serves to safeguard public interest by preventing invalid or weak patents from remaining formally registered.
Learn more about Patent Registration.
Background: Patent Revocation and Invalidity in Indian Law
Patent revocation and invalidity in Indian law serve as crucial safeguards to ensure that only genuine, novel, and legally compliant inventions enjoy exclusive protection. Under the Patents Act, 1970, a granted patent can be challenged and revoked on several grounds, including lack of novelty, obviousness, wrongful obtainment, insufficient disclosure, or non-patentable subject matter. Revocation may be initiated through the High Courts, counterclaims in infringement suits, or petitions before the IPAB’s successor forums. Importantly, Indian law recognizes that public interest and market fairness require continuous scrutiny of patent validity, which is why revocation proceedings may continue even after the patent has expired, especially when questions of enforceability, damages, or precedent remain relevant. Together, these mechanisms uphold the integrity of the patent system by ensuring that monopoly rights are granted only to inventions that truly meet statutory standards.
A revocation petition under Section 64 of the Patents Act, 1970 is a powerful legal remedy that allows any “person interested” such as a competitor, licensee, or affected party or even the Central Government, to seek the complete cancellation of a granted patent. This petition challenges the very validity of the patent and can be filed on several grounds, including lack of novelty, obviousness, wrongful obtaining, non-patentable subject matter, insufficient disclosure, or non-compliance with statutory requirements. Once filed before the High Court or the IPAB’s successor forum, the revocation petition, if successful, results in the full removal of the patent from the register, treating it as though it were never valid. This mechanism ensures that only genuinely innovative, legally compliant, and properly disclosed inventions enjoy the exclusive rights granted under Indian patent law.
An invalidity defense under Section 107 of the Patents Act, 1970 allows a defendant in a patent infringement suit to challenge the very validity of the patent being asserted against them. Instead of merely denying infringement, the defendant argues that the patent itself or specific claims within it suffers from legal defects such as lack of novelty, obviousness, insufficient disclosure, non-patentable subject matter, or wrongful obtainment. If the court finds even some claims invalid, the infringement allegations based on those claims automatically fail, because an invalid patent cannot be enforced. Thus, Section 107 provides a powerful shield, enabling defendants to use grounds available for revocation under Section 64 as a complete defense to infringement.
Though both target the validity of a patent, historically there was uncertainty whether they are functionally equivalent, and more importantly, whether a revocation petition can survive after the patent has expired. The recent decision by the Delhi High Court in Macleods Pharmaceuticals Ltd v. The Controller of Patents & Anr. clarifies both aspects and has major implications for patent litigation in India.
What Happened: Facts of the Macleods /Boehringer Ingelheim Dispute
The disputed patent was Indian Patent IN 243301 held by Boehringer Ingelheim Pharma GmbH & Co. KG (BI), covering the anti-diabetic drug Linagliptin. The patent was granted on 5 October 2010 (with priority date 21 August 2002).  
On 17 February 2022, MacLeods Pharmaceuticals Ltd (the petitioner) filed a revocation petition under Section 64, challenging the validity of the patent. Shortly thereafter, BI filed a patent infringement suit in the High Court of Himachal Pradesh (Himachal suit), seeking damages and injunctive relief. In its defense, MacLeods invoked the invalidity of the patent under Section 107 (i.e., raised an invalidity defense in the infringement suit). Meanwhile, the patent’s statutory term expired on 18 August 2023. BI moved before the DHC to dismiss the revocation petition on two grounds: (i) that Macleods had already raised invalidity under Section 107 in the infringement suit (so Section 64 petition was redundant), and (ii) that the patent had expired, so the revocation petition had become moot/infructuous.
Thus, the DHC had to decide whether the revocation petition could be maintained, despite the pending infringement suit and despite the expiry of the patent.
Court’s Decision and Legal Reasoning
On 15 January 2025, a Single-Judge bench of the Delhi High Court (Justice Amit Bansal) delivered its judgment, addressing two key issues that - is a revocation petition under Section 64 maintainable if the petitioner has already taken a defense of invalidity under Section 107 in a parallel infringement suit? and Can a revocation petition survive or be sustained even after the patent has expired?
Findings on Issue 1 — Revocation vs Invalidity Defense
The Court held that a revocation petition under Section 64 is fundamentally different from raising invalidity as a defense under Section 107. The two proceedings serve different purposes and have different scopes and legal effects; Section 64 grants a standalone right to any “person interested” to seek cancellation of the entire patent (or the relevant portion) irrespective of whether any infringement suit is pending or even filed; On the other hand, Section 107 only allows the defendant in an infringement suit to attack specific claims (as a defense), which even if successful does not automatically remove the patent from the Register. Such invalidity findings apply only between the parties (in personam), not universally against all third parties.
The Court further noted that only High Courts have the jurisdiction to revoke patents under Section 64; but invalidity under Section 107 can be adjudicated even by a District Court. The Court therefore allowed the revocation petition to proceed, even though Macleods had already filed a written statement in the infringement suit raising invalidity defenses.
Findings on Issue 2 — Maintainability Post Patent Expiry
The Court held that the expiry of the patent does not necessarily render a revocation petition infructuous. A revocation petition filed before expiry can be maintained even after the patent term is over; The Court noted that the Patents Act does not prescribe any limitation period for filing a revocation petition under Section 64 (contrast: oppositions under Section 25(2) have a time limit post grant); Importantly, the Court observed that the cause of action for damages in the infringement suit (filed while patent was alive) still survives after expiry, so there remains a real and concrete interest in continuing the revocation proceeding. Thus, revocation remains relevant and consequently, the Court dismissed BI’s applications seeking dismissal of the revocation petition. The revocation petition was held to be maintainable and sustainable.
Thus, the Court’s decision establishes two important propositions: that revocation under Section 64 is separate from invalidity under Section 107; and that a revocation petition can survive even after patent expiry.
Significance & Implications of the Ruling
The DHC’s ruling in Macleods v. Controller of Patents has broad significance for patent litigation in India. Some of the key implications:

Certainty for generic / competitor players: Entities seeking to challenge questionable patents (e.g., “evergreen” patents in pharma) now have assurance that they can still press for revocation even if the patent has expired and provided a revocation petition was filed while it was alive. This can help clear the path for generic entry, or for clearing the way for others, by removing the patent from the register.

Distinction between revocation and invalidity clarified: The judgment sharply delineates the difference between a revocation petition under Section 64 and an invalidity defense under Section 107. This helps avoid confusion and reinforces that both routes can be pursued (subject to procedural strategy).

No limitation period ⇒ open to old patents: Since Section 64 does not prescribe a time limit, even older patents could, in theory, be challenged long after grant so long as there is a “person interested” and a valid cause of action. That can encourage increased post-grant scrutiny and may incentivize patent holders to ensure robustness of patents.

Impact on ongoing infringement suits: Because a successful revocation removes the patent from the Register (operates in rem), revocation may cause existing infringement suits to collapse or be dismissed. That makes revocation petitions a powerful strategic tool.

Public interest and quality of patents: The ruling bolsters the public policy objective behind patent revocation: ensuring that only valid inventions remain monopolized and preventing abuse of weak or invalid patents.

Briefly, the decision enhances the enforceability of post-grant validity challenges, strengthens legal clarity, and may shift balance towards competition/generics in certain sectors (e.g., pharma).
Final Word
The Delhi High Court’s decision in Macleods Pharmaceuticals Ltd v. The Controller of Patents & Anr. marks a landmark clarification in Indian patent jurisprudence. By distinguishing clearly between revocation under Section 64 and invalidity defense under Section 107 and holding that a revocation petition is maintainable even after patent expiry, the Court has reaffirmed the potency and flexibility of revocation as a remedy. This judgment enriches the toolbox of competitors, generic manufacturers, IP challengers, and public interest actors seeking to contest weak or unjust patents. It helps ensure that patent monopolies even after expiry can be scrutinized and cancelled if they should never have been granted. Going forward, this may lead to more post-grant revocation petitions, greater transparency in the patent register, and stronger checks on evergreen or low-quality patents. For patent holders and right-owners, the ruling underscores the necessity to maintain rigorous patent prosecution standards, robust prior-art searches, high-quality disclosure, and continuous monitoring of potential invalidity grounds because revocation remains a live risk even post expiry.
FAQs
Q1. What is a “revocation petition” under Section 64?
Ans. A revocation petition under Section 64 is a standalone legal proceeding through which a “person interested” (or the government) can seek cancellation (revocation) of a patent, on grounds such as lack of novelty, lack of inventive step, non-disclosure, non-patentable subject-matter, etc. If successful, the patent is removed from the Register as if it never existed.
Q2. How is revocation different from raising invalidity in an infringement suit (Section 107)?
Ans. A revocation under Section 64 is a separate petition and can be filed even without an infringement suit. It targets the entire patent (or parts of it) and aims to remove it from the Register (in rem) and an invalidity defense under Section 107 is only a part of a pending infringement suit and applies only to claims asserted therein. Even if certain claims are invalidated, the patent remains on record (unless further action taken). The effect is in personam, between the parties.
Q3. Is there a time limit / statute of limitations for filing a revocation petition under Section 64?
Ans. No. The Court in Macleods held that there is no limitation period prescribed for revocation petitions under Section 64. Unlike oppositions under Section 25(2), which have a fixed window post grant, Section 64 allows a petition at any time — even many years after grant provided the petitioner qualifies as a “person interested.”
Q4. Does patent expiry automatically kill a revocation petition?
Ans. No. The Delhi High Court held that a revocation petition filed before expiry remains maintainable even after the patent term has ended. Expiry does not render the petition infructuous.
Q5. Why does the revocation petition remain relevant after expiry?
Ans. Because even after expiry, certain legal interests may survive, for instance, ongoing infringement suits filed during the life of the patent, claims for damages, or the need to clear the patent register. Removing an expired but potentially invalid patent may have legal and commercial consequences, including preventing assertions against third parties.
Q6. Who can file a revocation petition under Section 64? 
Ans. The Act allows a “person interested” to file such a petition. That includes people engaged in manufacturing or selling the patented product or process, competitors, parties against whom infringement suits have been filed, or others having interest in the patented invention.
Q7. Can a party both raise invalidity in a suit and independently file a revocation petition? 
Ans. Yes. The DHC made clear that raising an invalidity defense under Section 107 in an infringement suit does not bar a separate revocation petition under Section 64. The two are distinct remedies under law.
Q8. What happens if a revocation petition succeeds after patent expiry? 
Ans. If the petition succeeds, the patent is revoked removed from the Register. That means, as a matter of legal record, the patent is treated as if it never existed. This may have consequences for any pending infringement suits, third-party rights, licensing arrangements, and public record.
Q9. Does this rule apply to all patents, or only to pharmaceutical patents like Linagliptin? 
Ans. The ruling is based on statutory interpretation of the Patents Act (Sections 64, 107, and related provisions) and is not limited to pharmaceuticals. Therefore, its logic should apply broadly to patents across fields if the procedural requirements are met.
Q10. What is the larger significance of this ruling for the Indian patent system? 
Ans. The ruling strengthens post-grant scrutiny, enhances legal certainty for revocation proceedings, and reinforces public interest by enabling removal of weak patents. It encourages patent holders to ensure high standards of disclosure, novelty, inventive step and compliance, knowing that revocation remains a live avenue even post expiry. It may also encourage more generic/competitor-driven challenges.

The recent decision of the Delhi High Court marks a significant shift in Indian patent jurisprudence the Court has affirmed that a revocation petition under Patents Act, 1970 may be maintained even after the statutory term of the patent has expired. Traditionally, once a patent lapsed its term, it was widely assumed to have entered the public domain and thus immune from revocation actions. However, the Court has clarified that expiry does not automatically render revocation proceedings moot if there remains a valid cause of action such as ongoing claims for damages under a pending infringement suit. The judgment emphasizes the legal distinction between a revocation petition (under Section 64) and an invalidity defense in an infringement suit (under Section 107). A revocation petition which, if successful, removes the patent from the Register as though it never existed is materially different in purpose and effect from raising invalidity in a suit, which binds only the parties involved. By doing so, the Court has opened the door for post-expiry challenges to patents, ensuring that even once a patent’s term has lapsed, its validity can still be tested under appropriate circumstances. This serves to safeguard public interest by preventing invalid or weak patents from remaining formally registered.

Learn more about Patent Registration.

Background: Patent Revocation and Invalidity in Indian Law

Patent revocation and invalidity in Indian law serve as crucial safeguards to ensure that only genuine, novel, and legally compliant inventions enjoy exclusive protection. Under the Patents Act, 1970, a granted patent can be challenged and revoked on several grounds, including lack of novelty, obviousness, wrongful obtainment, insufficient disclosure, or non-patentable subject matter. Revocation may be initiated through the High Courts, counterclaims in infringement suits, or petitions before the IPAB’s successor forums. Importantly, Indian law recognizes that public interest and market fairness require continuous scrutiny of patent validity, which is why revocation proceedings may continue even after the patent has expired, especially when questions of enforceability, damages, or precedent remain relevant. Together, these mechanisms uphold the integrity of the patent system by ensuring that monopoly rights are granted only to inventions that truly meet statutory standards.

A revocation petition under Section 64 of the Patents Act, 1970 is a powerful legal remedy that allows any “person interested” such as a competitor, licensee, or affected party or even the Central Government, to seek the complete cancellation of a granted patent. This petition challenges the very validity of the patent and can be filed on several grounds, including lack of novelty, obviousness, wrongful obtaining, non-patentable subject matter, insufficient disclosure, or non-compliance with statutory requirements. Once filed before the High Court or the IPAB’s successor forum, the revocation petition, if successful, results in the full removal of the patent from the register, treating it as though it were never valid. This mechanism ensures that only genuinely innovative, legally compliant, and properly disclosed inventions enjoy the exclusive rights granted under Indian patent law.

An invalidity defense under Section 107 of the Patents Act, 1970 allows a defendant in a patent infringement suit to challenge the very validity of the patent being asserted against them. Instead of merely denying infringement, the defendant argues that the patent itself or specific claims within it suffers from legal defects such as lack of novelty, obviousness, insufficient disclosure, non-patentable subject matter, or wrongful obtainment. If the court finds even some claims invalid, the infringement allegations based on those claims automatically fail, because an invalid patent cannot be enforced. Thus, Section 107 provides a powerful shield, enabling defendants to use grounds available for revocation under Section 64 as a complete defense to infringement.

Though both target the validity of a patent, historically there was uncertainty whether they are functionally equivalent, and more importantly, whether a revocation petition can survive after the patent has expired. The recent decision by the Delhi High Court in Macleods Pharmaceuticals Ltd v. The Controller of Patents & Anr. clarifies both aspects and has major implications for patent litigation in India.

What Happened: Facts of the Macleods /Boehringer Ingelheim Dispute

The disputed patent was Indian Patent IN 243301 held by Boehringer Ingelheim Pharma GmbH & Co. KG (BI), covering the anti-diabetic drug Linagliptin. The patent was granted on 5 October 2010 (with priority date 21 August 2002).

On 17 February 2022, MacLeods Pharmaceuticals Ltd (the petitioner) filed a revocation petition under Section 64, challenging the validity of the patent. Shortly thereafter, BI filed a patent infringement suit in the High Court of Himachal Pradesh (Himachal suit), seeking damages and injunctive relief. In its defense, MacLeods invoked the invalidity of the patent under Section 107 (i.e., raised an invalidity defense in the infringement suit). Meanwhile, the patent’s statutory term expired on 18 August 2023. BI moved before the DHC to dismiss the revocation petition on two grounds: (i) that Macleods had already raised invalidity under Section 107 in the infringement suit (so Section 64 petition was redundant), and (ii) that the patent had expired, so the revocation petition had become moot/infructuous.

Thus, the DHC had to decide whether the revocation petition could be maintained, despite the pending infringement suit and despite the expiry of the patent.

Court’s Decision and Legal Reasoning

On 15 January 2025, a Single-Judge bench of the Delhi High Court (Justice Amit Bansal) delivered its judgment, addressing two key issues that - is a revocation petition under Section 64 maintainable if the petitioner has already taken a defense of invalidity under Section 107 in a parallel infringement suit? and Can a revocation petition survive or be sustained even after the patent has expired?

Findings on Issue 1 — Revocation vs Invalidity Defense

The Court held that a revocation petition under Section 64 is fundamentally different from raising invalidity as a defense under Section 107. The two proceedings serve different purposes and have different scopes and legal effects; Section 64 grants a standalone right to any “person interested” to seek cancellation of the entire patent (or the relevant portion) irrespective of whether any infringement suit is pending or even filed; On the other hand, Section 107 only allows the defendant in an infringement suit to attack specific claims (as a defense), which even if successful does not automatically remove the patent from the Register. Such invalidity findings apply only between the parties (in personam), not universally against all third parties.

The Court further noted that only High Courts have the jurisdiction to revoke patents under Section 64; but invalidity under Section 107 can be adjudicated even by a District Court. The Court therefore allowed the revocation petition to proceed, even though Macleods had already filed a written statement in the infringement suit raising invalidity defenses.

Findings on Issue 2 — Maintainability Post Patent Expiry

The Court held that the expiry of the patent does not necessarily render a revocation petition infructuous. A revocation petition filed before expiry can be maintained even after the patent term is over; The Court noted that the Patents Act does not prescribe any limitation period for filing a revocation petition under Section 64 (contrast: oppositions under Section 25(2) have a time limit post grant); Importantly, the Court observed that the cause of action for damages in the infringement suit (filed while patent was alive) still survives after expiry, so there remains a real and concrete interest in continuing the revocation proceeding. Thus, revocation remains relevant and consequently, the Court dismissed BI’s applications seeking dismissal of the revocation petition. The revocation petition was held to be maintainable and sustainable.

Thus, the Court’s decision establishes two important propositions: that revocation under Section 64 is separate from invalidity under Section 107; and that a revocation petition can survive even after patent expiry.

Significance & Implications of the Ruling

The DHC’s ruling in Macleods v. Controller of Patents has broad significance for patent litigation in India. Some of the key implications:

Certainty for generic / competitor players: Entities seeking to challenge questionable patents (e.g., “evergreen” patents in pharma) now have assurance that they can still press for revocation even if the patent has expired and provided a revocation petition was filed while it was alive. This can help clear the path for generic entry, or for clearing the way for others, by removing the patent from the register.
Distinction between revocation and invalidity clarified: The judgment sharply delineates the difference between a revocation petition under Section 64 and an invalidity defense under Section 107. This helps avoid confusion and reinforces that both routes can be pursued (subject to procedural strategy).
No limitation period ⇒ open to old patents: Since Section 64 does not prescribe a time limit, even older patents could, in theory, be challenged long after grant so long as there is a “person interested” and a valid cause of action. That can encourage increased post-grant scrutiny and may incentivize patent holders to ensure robustness of patents.
Impact on ongoing infringement suits: Because a successful revocation removes the patent from the Register (operates in rem), revocation may cause existing infringement suits to collapse or be dismissed. That makes revocation petitions a powerful strategic tool.
Public interest and quality of patents: The ruling bolsters the public policy objective behind patent revocation: ensuring that only valid inventions remain monopolized and preventing abuse of weak or invalid patents.

Briefly, the decision enhances the enforceability of post-grant validity challenges, strengthens legal clarity, and may shift balance towards competition/generics in certain sectors (e.g., pharma).

Final Word

The Delhi High Court’s decision in Macleods Pharmaceuticals Ltd v. The Controller of Patents & Anr. marks a landmark clarification in Indian patent jurisprudence. By distinguishing clearly between revocation under Section 64 and invalidity defense under Section 107 and holding that a revocation petition is maintainable even after patent expiry, the Court has reaffirmed the potency and flexibility of revocation as a remedy. This judgment enriches the toolbox of competitors, generic manufacturers, IP challengers, and public interest actors seeking to contest weak or unjust patents. It helps ensure that patent monopolies even after expiry can be scrutinized and cancelled if they should never have been granted. Going forward, this may lead to more post-grant revocation petitions, greater transparency in the patent register, and stronger checks on evergreen or low-quality patents. For patent holders and right-owners, the ruling underscores the necessity to maintain rigorous patent prosecution standards, robust prior-art searches, high-quality disclosure, and continuous monitoring of potential invalidity grounds because revocation remains a live risk even post expiry.

FAQs

Q1. What is a “revocation petition” under Section 64?

Ans. A revocation petition under Section 64 is a standalone legal proceeding through which a “person interested” (or the government) can seek cancellation (revocation) of a patent, on grounds such as lack of novelty, lack of inventive step, non-disclosure, non-patentable subject-matter, etc. If successful, the patent is removed from the Register as if it never existed.

Q2. How is revocation different from raising invalidity in an infringement suit (Section 107)?

Ans. A revocation under Section 64 is a separate petition and can be filed even without an infringement suit. It targets the entire patent (or parts of it) and aims to remove it from the Register (in rem) and an invalidity defense under Section 107 is only a part of a pending infringement suit and applies only to claims asserted therein. Even if certain claims are invalidated, the patent remains on record (unless further action taken). The effect is in personam, between the parties.

Q3. Is there a time limit / statute of limitations for filing a revocation petition under Section 64?

Ans. No. The Court in Macleods held that there is no limitation period prescribed for revocation petitions under Section 64. Unlike oppositions under Section 25(2), which have a fixed window post grant, Section 64 allows a petition at any time — even many years after grant provided the petitioner qualifies as a “person interested.”

Q4. Does patent expiry automatically kill a revocation petition?

Ans. No. The Delhi High Court held that a revocation petition filed before expiry remains maintainable even after the patent term has ended. Expiry does not render the petition infructuous.

Q5. Why does the revocation petition remain relevant after expiry?

Ans. Because even after expiry, certain legal interests may survive, for instance, ongoing infringement suits filed during the life of the patent, claims for damages, or the need to clear the patent register. Removing an expired but potentially invalid patent may have legal and commercial consequences, including preventing assertions against third parties.

Q6. Who can file a revocation petition under Section 64?

Ans. The Act allows a “person interested” to file such a petition. That includes people engaged in manufacturing or selling the patented product or process, competitors, parties against whom infringement suits have been filed, or others having interest in the patented invention.

Q7. Can a party both raise invalidity in a suit and independently file a revocation petition?

Ans. Yes. The DHC made clear that raising an invalidity defense under Section 107 in an infringement suit does not bar a separate revocation petition under Section 64. The two are distinct remedies under law.

Q8. What happens if a revocation petition succeeds after patent expiry?

Ans. If the petition succeeds, the patent is revoked removed from the Register. That means, as a matter of legal record, the patent is treated as if it never existed. This may have consequences for any pending infringement suits, third-party rights, licensing arrangements, and public record.

Q9. Does this rule apply to all patents, or only to pharmaceutical patents like Linagliptin?

Ans. The ruling is based on statutory interpretation of the Patents Act (Sections 64, 107, and related provisions) and is not limited to pharmaceuticals. Therefore, its logic should apply broadly to patents across fields if the procedural requirements are met.

Q10. What is the larger significance of this ruling for the Indian patent system?

Ans. The ruling strengthens post-grant scrutiny, enhances legal certainty for revocation proceedings, and reinforces public interest by enabling removal of weak patents. It encourages patent holders to ensure high standards of disclosure, novelty, inventive step and compliance, knowing that revocation remains a live avenue even post expiry. It may also encourage more generic/competitor-driven challenges.