DCT

1:25-cv-01382

Vifor Fresenius Medical Care Renal Pharma Ltd v. Gland Pharma Ltd

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Complaint
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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-01382, D. Del., 11/13/2025
  • Venue Allegations: Venue is alleged to be proper in Delaware. For defendants Somerset Therapeutics and Odin Pharmaceuticals, this is based on their incorporation in Delaware. For foreign defendants Gland Pharma, Qilu Hainan, and domestic defendant Qilu Pharma, venue is based on alleged acts of patent infringement directed at Delaware, systematic and continuous business contacts, and having previously consented to or been subject to personal jurisdiction in the district in prior patent cases.
  • Core Dispute: Plaintiffs allege that Defendants' filing of Abbreviated New Drug Applications (ANDAs) to seek FDA approval for generic versions of Plaintiffs' KORSUVA® (difelikefalin) injection constitutes an act of patent infringement under the Hatch-Waxman Act.
  • Technical Context: The technology concerns synthetic peptide amides that act as kappa opioid receptor agonists, developed to treat conditions such as pruritus (itching) in patients with chronic kidney disease, while minimizing central nervous system side effects.
  • Key Procedural History: The lawsuit was initiated in response to Defendants sending Plaintiffs Paragraph IV Certification Letters, which asserted that the patents-in-suit are invalid, unenforceable, and/or would not be infringed by the manufacture and sale of their proposed generic products. This action under 35 U.S.C. § 271(e)(2) triggers a 30-month stay of FDA approval for the Defendants' ANDAs, unless the litigation is resolved sooner.

Case Timeline

Date Event
2006-11-10 Earliest Priority Date ('963, '305, '399, '270, '596 Patents)
2007-05-10 Earliest Priority Date ('564, '937, '007, '766, '894, '131, '536 Patents)
2008-07-22 U.S. Patent 7,402,564 Issued
2010-05-11 U.S. Patent 7,713,937 Issued
2010-06-01 U.S. Patent 7,727,963 Issued
2012-07-10 U.S. Patent 8,217,007 Issued
2012-08-07 U.S. Patent 8,236,766 Issued
2013-07-16 U.S. Patent 8,486,894 Issued
2013-09-17 U.S. Patent 8,536,131 Issued
2016-05-10 U.S. Patent 9,334,305 Issued
2016-06-07 U.S. Patent 9,359,399 Issued
2018-07-10 U.S. Patent 10,017,536 Issued
2018-11-27 U.S. Patent 10,138,270 Issued
2020-10-06 U.S. Patent 10,793,596 Issued
2025-09-29 Vifor receives Somerset Paragraph IV Certification Letter
2025-09-30 Vifor receives Qilu Paragraph IV Certification Letter
2025-10-02 Vifor receives Gland Paragraph IV Certification Letter
2025-11-13 Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 7,402,564 - “Synthetic Peptide Amides”

  • Issued: July 22, 2008

The Invention Explained

  • Problem Addressed: The patent describes a need for therapeutic agents that act on kappa opioid receptors to treat a variety of conditions, including pain and inflammation. A significant challenge with such agents is the potential for undesirable central nervous system (CNS) side effects, which can occur if the drug crosses the blood-brain barrier (’564 Patent, col. 2:1-5; ’564 Patent, col. 2:56-65).
  • The Patented Solution: The invention provides a class of synthetic peptide amides designed to be selective kappa opioid receptor agonists that exhibit low potential for crossing the blood-brain barrier (’564 Patent, abstract). This peripheral selectivity is intended to allow the compounds to exert their therapeutic effects on tissues outside the CNS, thereby avoiding or reducing the CNS-related side effects associated with other opioid agonists (’564 Patent, col. 2:56-65; ’564 Patent, col. 5:6-15).
  • Technical Importance: This approach represented an effort to decouple the peripheral therapeutic benefits of kappa opioid agonists from their centrally-mediated side effects, potentially creating a new class of safer and better-tolerated drugs for conditions like peripheral pain or pruritus.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 (Compl. ¶79).
  • The essential elements of claim 1, a composition of matter claim, include:
    • A synthetic peptide amide having the formula: Xaa₁-Xaa₂-Xaa₃-Xaa₄-G
    • or a stereoisomer, mixture of stereoisomers, pharmaceutically acceptable salt, hydrate, or N-oxide thereof;
    • wherein Xaa₁, Xaa₂, Xaa₃, Xaa₄, and G are defined by extensive Markush groups of specific chemical structures and amino acid residues (’564 Patent, col. 84:19-67).

U.S. Patent No. 7,713,937 - “Synthetic Peptide Amides and Dimeric Forms Thereof”

  • Issued: May 11, 2010

The Invention Explained

  • Problem Addressed: Similar to the ’564 Patent, this patent addresses the need to develop kappa opioid receptor agonists that act peripherally to avoid CNS side effects (’937 Patent, col. 2:1-5; ’937 Patent, col. 2:62-67).
  • The Patented Solution: The invention relates to synthetic peptide amides, including monomeric and dimeric forms, which are designed as selective kappa opioid receptor agonists with poor penetration of the blood-brain barrier (’937 Patent, abstract). The inclusion of dimeric structures—two peptide monomers joined by a linker—provides an alternative chemical scaffold for achieving the desired therapeutic profile (’937 Patent, col. 14:14-27).
  • Technical Importance: By introducing dimeric forms, the invention expanded the chemical space available for developing peripherally-acting kappa opioid agonists, potentially allowing for compounds with different potency, solubility, or pharmacokinetic properties compared to monomeric versions.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 (Compl. ¶88).
  • The essential elements of claim 1, a composition of matter claim, include:
    • A synthetic peptide amide having the formula: Xaa₁-Xaa₂-Xaa₃-Xaa₄-G
    • or a stereoisomer, mixture of stereoisomers, pharmaceutically acceptable salt, hydrate, N-oxide or isomorphically crystalline forms thereof;
    • wherein Xaa₁, Xaa₂, Xaa₃, Xaa₄, and G are defined by extensive Markush groups of specific chemical structures and amino acid residues, which partially overlap but also differ from those in the ’564 Patent (’937 Patent, col. 138:39-67).

U.S. Patent No. 7,727,963 - “Synthetic Peptide Amides”

  • Issued: June 1, 2010
  • Technology Synopsis: This patent claims a specific synthetic peptide amide, identified as D-Phe-D-Phe-D-Leu-D-Lys-[N-epsilon-(4-amidino-homopiperazine amide)], or a pharmaceutically acceptable salt thereof (’963 Patent, col. 81:13-23). This is the compound known as difelikefalin.
  • Asserted Claims: At least claim 1 (Compl. ¶97).
  • Accused Features: The difelikefalin acetate active ingredient in the Defendants' proposed generic products is alleged to be the compound claimed in the ’963 Patent (Compl. ¶96).

U.S. Patent No. 8,217,007 - “Synthetic Peptide Amides”

  • Issued: July 10, 2012
  • Technology Synopsis: This patent claims methods of treating, inhibiting, or preventing a kappa opioid receptor-associated disease or condition. The method involves administering an effective amount of a specific synthetic peptide amide (difelikefalin) (’007 Patent, col. 81:24-46).
  • Asserted Claims: At least claim 1 (Compl. ¶106).
  • Accused Features: The proposed use of the generic products to treat moderate-to-severe pruritus, as will be described on the product labels, is alleged to infringe this method-of-use patent (Compl. ¶105).

U.S. Patent No. 8,236,766 - “Uses of Synthetic Peptide Amides”

  • Issued: August 7, 2012
  • Technology Synopsis: This patent claims a method for treating specific conditions, including pruritus, by administering a synthetic peptide amide from a claimed Markush group (’766 Patent, col. 158:11-37).
  • Asserted Claims: At least claim 1 (Compl. ¶115).
  • Accused Features: The intended use of the Defendants' generic products for treating pruritus is alleged to infringe the claimed method (Compl. ¶114).

U.S. Patent No. 8,486,894 - “Synthetic Peptide Amides and Dimeric Forms Thereof”

  • Issued: July 16, 2013
  • Technology Synopsis: This patent claims methods of treating a kappa opioid receptor-associated disease by administering a compound from a broad Markush group (’894 Patent, col. 140:11-40).
  • Asserted Claims: At least claim 1 (Compl. ¶124).
  • Accused Features: The intended use of the generic products, containing difelikefalin, is alleged to fall under the claimed method of treatment (Compl. ¶123).

U.S. Patent No. 8,536,131 - “Synthetic Peptide Amides and Dimers Thereof”

  • Issued: September 17, 2013
  • Technology Synopsis: This patent claims methods of treating or preventing pain, pancreatitis, or pruritus by administering a compound from a Markush group (’131 Patent, col. 110:24-51). The claims were later corrected to cover only pancreatitis and pruritus.
  • Asserted Claims: At least claim 1 (Compl. ¶133).
  • Accused Features: The proposed use of the generic products for pruritus is alleged to infringe the claimed method (Compl. ¶132).

U.S. Patent No. 9,334,305 - “Synthetic Peptide Amides and Dimers Thereof”

  • Issued: May 10, 2016
  • Technology Synopsis: This patent claims a method of treating a kappa opioid receptor-associated disease or condition by administering a compound from a Markush group, with specific definitions for the constituent parts of the peptide amide (’305 Patent, col. 107:15-46).
  • Asserted Claims: At least claim 1 (Compl. ¶142).
  • Accused Features: The use of the difelikefalin-containing generic product is alleged to infringe the claimed method of treatment (Compl. ¶141).

U.S. Patent No. 9,359,399 - “Synthetic Peptide Amides”

  • Issued: June 7, 2016
  • Technology Synopsis: This patent claims a method of treating pruritus by administering a compound from a Markush group that includes difelikefalin as an exemplary embodiment (’399 Patent, col. 83:4-10; ’399 Patent, col. 83:43-52).
  • Asserted Claims: At least claim 1 (Compl. ¶151).
  • Accused Features: The intended use of the generic products for treating pruritus is alleged to infringe the claimed method (Compl. ¶150).

U.S. Patent No. 10,017,536 - “Synthetic Peptide Peptides and Dimers Thereof”

  • Issued: July 10, 2018
  • Technology Synopsis: This patent claims methods of treating pruritus in patients with chronic kidney disease, end-stage renal disease, or on dialysis by administering a specific compound, difelikefalin (’536 Patent, col. 108:3-11; ’536 Patent, col. 108:44-50).
  • Asserted Claims: At least claim 1 (Compl. ¶160).
  • Accused Features: The proposed use of the generic products for treating pruritus in hemodialysis patients is alleged to directly map onto the claimed method (Compl. ¶159).

U.S. Patent No. 10,138,270 - “Synthetic Peptide Amides”

  • Issued: November 27, 2018
  • Technology Synopsis: This patent claims methods of treating pruritus in human patients with specific kidney-related conditions, including chronic kidney disease and end-stage renal disease, by administering a specific compound (difelikefalin) as a hydrochloride salt (’270 Patent, col. 82:48-60).
  • Asserted Claims: At least claim 1 (Compl. ¶169).
  • Accused Features: The active ingredient in the accused products is difelikefalin acetate, which Plaintiffs allege will infringe claims directed to the hydrochloride salt, potentially under the doctrine of equivalents (Compl. ¶168; Compl. ¶169).

U.S. Patent No. 10,793,596 - “Synthetic Peptide Amides”

  • Issued: October 6, 2020
  • Technology Synopsis: This patent claims methods of treating pruritus in specific patient populations (e.g., associated with chronic liver disease) by administering a specific compound, difelikefalin, in a pharmaceutical composition (’596 Patent, col. 80:9-25; ’596 Patent, col. 80:55-61).
  • Asserted Claims: At least claim 1 (Compl. ¶178).
  • Accused Features: The intended use of the generic products to treat pruritus is alleged to infringe the claimed methods (Compl. ¶177).

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities are the generic drug products for which Defendants Gland Pharma, Somerset Therapeutics, and Qilu Pharma have filed Abbreviated New Drug Applications (ANDA Nos. 220916, 220939, and 220919, respectively) (Compl. ¶28; Compl. ¶32; Compl. ¶36).

Functionality and Market Context

  • The proposed generic products are injectable solutions containing the active ingredient difelikefalin acetate, in a dosage of 0.05 mg base/1.3 mL (Compl. ¶25; Compl. ¶28). They are intended to be generic versions of Plaintiffs’ drug KORSUVA®, which is approved for the treatment of moderate-to-severe pruritus associated with chronic kidney disease in adult patients undergoing hemodialysis (Compl. ¶25). The complaint alleges that the Defendants' ANDA submissions include data purporting to show that their proposed products are bioequivalent to KORSUVA® (Compl. ¶78). The filing of the ANDAs represents a commercial effort to enter the market for this therapeutic indication upon patent expiry or a favorable court ruling.

No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint does not provide a detailed, element-by-element infringement analysis or include claim chart exhibits. Instead, it presents a general theory of infringement for each asserted patent, which is standard practice for initial complaints in Hatch-Waxman litigation.

The infringement theory for composition-of-matter claims (e.g., in the ’564, ’937, and ’963 patents) is that the act of filing an ANDA for a product containing difelikefalin constitutes infringement under 35 U.S.C. § 271(e)(2), because difelikefalin allegedly falls within the scope of the claimed chemical structures (Compl. ¶78; Compl. ¶87; Compl. ¶96).

The infringement theory for method-of-use claims (e.g., in the ’007, ’766, and other patents) is that the Defendants will induce infringement by others (e.g., doctors and patients) by seeking approval to market their generic products with a label that instructs users to administer the drug for the patented therapeutic purpose (e.g., treating pruritus) (Compl. ¶79; Compl. ¶106).

  • Identified Points of Contention:
    • Scope Questions: A principal dispute for the composition claims will likely be whether difelikefalin falls within the literal scope of the broad Markush groups recited in patents like the ’564 and ’937. For method-of-use claims, a key question will be whether the specific indication on the Defendants' proposed labels is coextensive with the methods claimed in the patents. For instance, the ’270 Patent claims administration of a hydrochloride salt, whereas the accused product is an acetate salt, which raises an immediate question of literal infringement versus reliance on the doctrine of equivalents (Compl. ¶168).
    • Technical Questions: The core of the dispute, as indicated by the Defendants' Paragraph IV letters, will involve questions of validity and non-infringement (Compl. ¶30). Defendants may argue that their specific difelikefalin formulation or salt form is chemically distinct from what is claimed. Furthermore, they are expected to challenge the validity of the asserted claims based on prior art, particularly given the large number of patents in the family covering similar chemical space and uses.

V. Key Claim Terms for Construction

  • The Term: The Markush group definitions for "Xaa₁-Xaa₄" and "G" in Claim 1 of the '564 and '937 patents.
  • Context and Importance: These terms define the metes and bounds of the claimed chemical genus. Whether the Defendants' difelikefalin compound infringes these composition claims will depend entirely on whether its specific structure falls within the definitions provided in these extensive lists of chemical moieties.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: Plaintiffs may argue that the terms should be given their plain and ordinary meaning as understood by a person of ordinary skill in the art of medicinal chemistry. They may point to the long list of possible substituents and structures in the claim language itself as evidence that the inventors intended to claim a broad class of compounds (’564 Patent, col. 84:19-67).
    • Evidence for a Narrower Interpretation: Defendants may argue that the specification's specific examples and embodiments should guide the interpretation of the claims more narrowly. For instance, they could argue that while the claim language is broad, the specification only enables or describes a smaller subset of compounds, or that statements made during prosecution limit the scope of these terms to exclude difelikefalin.
  • The Term: "treating" (from method-of-use claims, e.g., Claim 1 of the '007 patent)
  • Context and Importance: In method-of-use claims, the definition of "treating" is critical for determining infringement. The dispute will center on whether the instructions on the Defendants' proposed drug labels direct a use that falls within the scope of the patented method of "treating" a specific condition like pruritus.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: Plaintiffs may argue that "treating" should be interpreted broadly to include any administration of the drug for its indicated purpose, which would encompass prophylaxis, palliation, or amelioration of the condition, as is common in the art. The specification may provide broad language, for example, referring to "prophylaxis and treatment" of diseases (’007 Patent, abstract).
    • Evidence for a Narrower Interpretation: Defendants may attempt to narrow the term by tying it to specific outcomes or patient populations described in the specification's clinical examples. For example, they might argue the patented "treatment" requires achieving a specific level of efficacy or applies only to a subset of patients not fully covered by their proposed label, though this is often a difficult argument to win.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced infringement for the method-of-use patents. It asserts that by creating and seeking approval for a product with a label that instructs medical professionals and patients to use the drug in an infringing manner (i.e., to treat pruritus), the Defendants possess the specific intent to encourage infringement (Compl. ¶82; Compl. ¶91; Compl. ¶100).
  • Willful Infringement: The complaint does not use the term "willful infringement." However, it alleges that Defendants had knowledge of the patents-in-suit "since at least the date" they submitted their ANDAs, which included Paragraph IV certifications against those patents (Compl. ¶80). Based on this alleged knowledge, Plaintiffs request a declaration that the case is "exceptional" under 35 U.S.C. § 285, which would entitle them to an award of attorneys' fees (Compl. ¶60, Prayer WW-XX).

VII. Analyst’s Conclusion: Key Questions for the Case

  1. Chemical Scope and Validity: A primary issue for the numerous composition-of-matter claims will be twofold: first, whether the specific chemical structure of difelikefalin acetate falls within the literal scope of the broad Markush groups claimed in the earlier patents; and second, whether those broad claims are valid over the prior art that existed at the time of invention.
  2. Method Claim Infringement and Label Scope: For the many method-of-use patents, the central question will be whether the specific indications and instructions on the Defendants' proposed ANDA labels will induce infringement of the claimed methods of treating pruritus, particularly for the specific patient populations and salt forms recited in later patents like the '536 and '270.
  3. Patent Family Redundancy: With twelve patents asserted from a large, overlapping family, a significant question for the court will be to parse the distinct contribution of each patent's claims. The Defendants will likely argue that many of the later claims are invalid for obviousness-type double patenting over the earlier patents, which will require a detailed analysis of the claim scope and disclosure history of the entire patent portfolio.
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