Delhi High Court Establishes Precedent on the Validity of Markush Claims and Interim Injunction in Pharmaceutical Patent Infringement: Merck Sharp & Dohme v. Glenmark

Introduction

The case of Merck Sharp & Dohme Corporation And Anr. v. Glenmark Pharmaceuticals adjudicated by the Delhi High Court on March 20, 2015, marks a significant development in the interpretation and enforcement of pharmaceutical patents in India. The dispute centered around Merck Sharp & Dohme (MSD), the appellant, seeking an interim injunction against Glenmark Pharmaceuticals (Glenmark) for alleged infringement of MSD's patent on Sitagliptin, a drug used to manage Type 2 Diabetes Mellitus (T2DM).

MSD held the Indian Patent No. 209816 for Sitagliptin and its pharmaceutically acceptable salts, which it marketed under various trademarks, including "Januvia" and "Janumet." Glenmark introduced its product "Zita," containing Sitagliptin Phosphate Monohydrate, which MSD claimed infringed upon its patented formulation. The core issues revolved around the validity of the patent claims, especially the Markush claims encompassing a broad range of pharmaceutical salts, and whether Glenmark's product fell within this scope.

Summary of the Judgment

Initially, the learned Single Judge dismissed MSD's application for an ad interim injunction, citing insufficient evidence and raising concerns about the specificity of MSD's patent claims. MSD appealed this decision, arguing that Glenmark's actions constituted clear patent infringement. The Delhi High Court, upon reviewing the case, set aside the Single Judge's order and granted the interim injunction in favor of MSD.

The Court scrutinized the construction of the patent claims, particularly focusing on the Markush structure that broadly covered Sitagliptin and its pharmaceutically acceptable salts. It concluded that MSD's patent sufficiently disclosed the Sitagliptin free base, which is the active therapeutic agent, and that Glenmark's "Zita" product, containing Sitagliptin Phosphate Monohydrate, fell within the ambit of these claims. Additionally, the Court dismissed Glenmark's arguments regarding non-disclosure under Section 8 of the Indian Patents Act, emphasizing that the requirement pertained only to foreign patent applications, not those within India.

Analysis

Precedents Cited

The judgment refers to several pivotal cases and statutory provisions that have shaped the landscape of patent law in India:

• Novartis AG v. Union of India (2013): This case underscored the importance of Section 3(d) in preventing the patenting of minor modifications that do not result in enhanced efficacy.
• Hoffmann-La Roche Ltd. v. Cipla (2012): Emphasized the necessity of complete disclosure under Section 8 and the discretionary power under Section 64(1)(m) for patent revocation.
• P.M. Mehta’s Plastic.Stainless Fasteners Ltd. v. Union of India (1979): Reiterated that the validity of a patent is not presumed post-grant and can be challenged on various grounds.
• Om Prakash Enterprises v. Union of India (2013): Highlighted the importance of interpreting patent claims in consultation with the specification.
• International pharmaceutical case law, including Kirin-Amgen Inc. v. Hoechst Marion Roussel Limited and Regeneron & Anr v Genentech Inc, provided comparative insights on Markush claims and purposive construction of patents.

Legal Reasoning

The Court's legal reasoning encompassed several critical dimensions:

• Claim Construction: The Delhi High Court undertook a meticulous construction of the patent claims, especially the Markush claims covering Sitagliptin and its salts. It determined that Sitagliptin Phosphate Monohydrate, being a pharmaceutically acceptable salt of Sitagliptin, was inherently covered under the broad claims of the patent.
• Enabling Disclosure: The judgment emphasized that the patent sufficiently disclosed the Sitagliptin free base, the active ingredient, through detailed chemical structures and preparation methods. The Court held that mere identification of one salt form in the specification did not negate the inclusion of other acceptable salts within the claims.
• Section 8 Compliance: Glenmark contended that MSD had failed to disclose certain patent applications under Section 8 of the Indian Patents Act. The Court, however, clarified that Section 8's disclosure obligations were limited to foreign patent applications and did not extend to those filed within India. Consequently, MSD's compliance with Section 8 was deemed satisfactory.
• Markush Claims Validity: The Court addressed concerns about the overbreadth of Markush claims, asserting that such claims are permissible provided they are supported by the specification and do not create an unworkable monopoly. The Court found MSD's claims to be defensible, given the therapeutic utility of Sitagliptin in treating T2DM.
• Balance of Convenience and Public Interest: In granting the interim injunction, the Court weighed the potential irreparable harm to MSD against Glenmark's rights. It concluded that maintaining the patent's integrity and protecting MSD's exclusive rights was paramount, especially given the established demand for T2DM treatments in India.

Impact

The judgment has far-reaching implications for the pharmaceutical industry in India:

• Reaffirmation of Markush Claims: By upholding the validity of Markush claims in this context, the Court provides a robust precedent for pharmaceutical patents that encompass a range of active ingredients and their salts. This ensures that innovative drug formulations receive adequate protection against generic infringement.
• Strengthening Patent Protection: The decision reinforces the judiciary's stance on strict enforcement of patent rights, deterring potential infringers and encouraging pharmaceutical companies to invest in R&D without fear of unchallenged replication.
• Clarification on Section 8: By delineating the scope of disclosure under Section 8, the Court offers clarity to patent applicants regarding their obligations, reducing ambiguities that could lead to inadvertent non-compliance.
• Interim Injunction Protocols: The judgment outlines the factors courts should consider when granting interim injunctions in patent disputes, balancing patent integrity with public health interests.

Complex Concepts Simplified

Markush Claims

Definition: Markush claims are a type of patent claim used primarily in chemistry and pharmaceuticals. They allow the patent holder to claim a group of chemically related compounds by defining a generic structure with variable components.

Relevance in This Case: MSD's patent included Markush claims that covered Sitagliptin and its various pharmaceutically acceptable salts. This broad coverage was pivotal in asserting that Glenmark's product, containing Sitagliptin Phosphate Monohydrate, infringed upon the patent.

Section 8 of the Indian Patents Act

Purpose: Section 8 mandates patent applicants to disclose all relevant foreign patent applications that relate to the same or substantially the same invention as their Indian application.

Clarification: The Court clarified that this disclosure obligation pertains solely to patent applications filed outside India, not those within the country.

Section 3(d) of the Indian Patents Act

Purpose: Section 3(d) aims to prevent the patenting of minor modifications of existing drugs that do not result in enhanced efficacy, ensuring that only genuine innovations receive patent protection.

Application: While Glenmark invoked Section 3(d) arguments regarding MSD's subsequent patent applications, the Delhi High Court found that these did not affect the validity of the primary suit patent.

Interim Injunction

Definition: An interim injunction is a temporary court order that restrains a party from taking a specific action until a full hearing can be conducted.

Role in This Case: MSD sought an interim injunction to prevent Glenmark from selling its infringing product "Zita" while the patent infringement case was being adjudicated. The High Court granted this injunction, emphasizing the potential for irreparable harm to MSD's business interests.

Conclusion