DCT

1:25-cv-00563

Azurity Pharma Inc v. Alkem Laboratories Ltd

Log In
Key Events
Amended Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-00563, D. Del., 01/16/2026
  • Venue Allegations: Venue is alleged to be proper because the Defendant is a foreign corporation not residing in any U.S. judicial district. The complaint further alleges that the Defendant has continuous business contacts with Delaware and has previously engaged in patent litigation in the district.
  • Core Dispute: Plaintiff alleges that Defendant’s submission of an Abbreviated New Drug Application (ANDA) to the FDA for a generic version of Plaintiff’s ZONISADE® product constitutes an act of infringement of three patents related to oral suspension formulations of the anticonvulsant drug zonisamide.
  • Technical Context: The technology concerns pharmaceutical formulations designed to create a stable, palatable, and ready-to-use oral liquid suspension of a drug that is otherwise primarily available in solid dosage forms.
  • Key Procedural History: This action was initiated under the Hatch-Waxman Act following Defendant’s submission of ANDA No. 220352 and its subsequent notification to Plaintiff via a letter dated March 21, 2025. The patents-in-suit are listed in the FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations (the "Orange Book") in connection with Plaintiff's ZONISADE® product.

Case Timeline

Date Event
2017-08-19 Priority Date for ’456, ’333, and ’179 Patents
2022-10-25 ’456 Patent Issued
2022-12-20 ’333 Patent Issued
2025-03-21 Defendant’s ANDA Notice Letter to Plaintiff
2025-12-09 ’179 Patent Issued
2026-01-16 Complaint Filed

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

U.S. Patent No. 11,478,456 - *Oral Pharmaceutical Composition Comprising Zonisamide and Process of Preparation Thereof,* issued October 25, 2022

The Invention Explained

  • Problem Addressed: The patent’s background section notes that the anticonvulsant drug zonisamide is typically available in solid forms like capsules or tablets, which can be difficult for young children or seriously ill persons to swallow (ʼ456 Patent, col. 3:1-7). This creates a need for a pre-formulated oral liquid dosage form to ensure accurate and consistent administration for these patient populations (ʼ456 Patent, col. 3:1-16).
  • The Patented Solution: The invention is a liquid pharmaceutical composition of zonisamide, specifically an oral suspension, that is formulated for improved stability and palatability (ʼ456 Patent, col. 3:20-29). The solution uses a specific combination of pharmaceutically acceptable excipients, including suspending agents (e.g., xanthan gum), buffering agents to control pH, preservatives, and sweeteners, to create a ready-to-use oral liquid (ʼ456 Patent, Abstract; col. 3:49-61).
  • Technical Importance: The development of a stable, commercially manufactured liquid suspension provides a standardized, FDA-approved alternative to extemporaneously compounded formulations, which may have issues with stability and dosing accuracy (ʼ456 Patent, col. 3:1-16).

Key Claims at a Glance

  • The complaint asserts "one or more claims" of the patent (Compl. ¶33). Independent claim 1, a method of use claim, contains the following essential elements:
    • A method of treating seizures by administering a liquid oral pharmaceutical suspension.
    • The suspension comprises zonisamide in an amount of about 20 mg/mL.
    • It contains a specific two-part suspending agent: about 2 mg/mL to about 3.5 mg/mL of xanthan gum and about 20 mg/mL of a combination of microcrystalline cellulose and sodium carboxymethylcellulose.
    • The suspension includes one or more buffering agents and a preservative.
    • The suspension has a pH of 3.5 to 5.0.
    • The suspension is functionally defined as being stable for at least 6 months when stored under specific conditions (40° C. and 25% relative humidity).

U.S. Patent No. 11,529,333 - *Oral Pharmaceutical Composition Comprising Zonisamide and Process of Preparation Thereof,* issued December 20, 2022

The Invention Explained

  • Problem Addressed: The patent addresses the same technical problem as the ’456 Patent: the lack of a stable, palatable, and commercially produced oral liquid formulation of zonisamide for patients unable to swallow solid dosage forms (ʼ333 Patent, col. 3:5-10).
  • The Patented Solution: This patent claims the pharmaceutical composition itself, rather than the method of using it. The invention is a liquid oral suspension containing zonisamide combined with a particular set of excipients designed to ensure stability. Key components include a two-part suspending agent system, buffering agents, and a preservative, all formulated to maintain a specific pH range over time (ʼ333 Patent, Abstract; col. 4:15-34).
  • Technical Importance: The invention provides a specific, stable formulation that can be manufactured at scale, offering a reliable therapeutic option for vulnerable patient populations and improving patient compliance (ʼ333 Patent, col. 3:5-10).

Key Claims at a Glance

  • The complaint asserts "one or more claims" of the patent (Compl. ¶38). Independent claim 1, a composition claim, recites the following essential elements:
    • A liquid oral pharmaceutical suspension.
    • The suspension comprises zonisamide in an amount of about 20 mg/mL.
    • It contains a specific two-part suspending agent: about 2 mg/mL to about 3.5 mg/mL of xanthan gum and about 20 mg/mL of a combination of microcrystalline cellulose and sodium carboxymethylcellulose.
    • The suspension includes one or more buffering agents and a preservative.
    • The suspension has a pH of 3.5 to 5.0.
    • The composition is functionally defined as being stable for at least 6 months when stored under specific conditions (40° C. and 25% relative humidity).

U.S. Patent No. 12,491,179 - *Oral Pharmaceutical Composition Comprising Zonisamide and Process of Preparation Thereof,* issued December 9, 2025

Technology Synopsis

This patent is directed to a stable liquid oral pharmaceutical suspension of zonisamide intended for patients who have difficulty swallowing solid pills (’179 Patent, col. 3:1-10). The claims describe a composition with zonisamide as the only active ingredient, formulated with specific excipients including buffering agents, a preservative (sodium benzoate), sucralose, and strawberry flavor to achieve a pH between 3.5 and 5.0 and maintain stability (’179 Patent, Abstract; col. 11:46-12:12).

Asserted Claims

The complaint asserts infringement of "one or more claims" of the patent (Compl. ¶43). Independent claim 1 is a composition claim.

Accused Features

The accused product is Defendant's proposed generic zonisamide oral suspension, which the complaint alleges is a copy of Plaintiff’s ZONISADE® product and will therefore embody the claimed invention (Compl. ¶30, ¶43-44).

III. The Accused Instrumentality

Product Identification

The accused instrumentality is Defendant Alkem's proposed generic version of Azurity’s ZONISADE® oral suspension, referred to as the "Alkem ANDA Product," which is the subject of ANDA No. 220352 submitted to the FDA (Compl. ¶1, ¶25).

Functionality and Market Context

The complaint alleges that by filing its ANDA, Alkem has represented to the FDA that its product has the same active ingredient (zonisamide), route of administration, dosage form, strength, and intended use as Plaintiff's ZONISADE® product, and is bioequivalent to it (Compl. ¶30). The product is an anticonvulsant indicated for adjunctive therapy in the treatment of partial onset seizures (Compl. ¶11). The act of infringement alleged is the submission of the ANDA itself, which seeks approval to market the generic drug before the expiration of the patents-in-suit (Compl. ¶33). 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 an appended claim chart. The central allegation is that because Defendant's ANDA product is represented as a generic equivalent to Plaintiff's patented ZONISADE® product, it will necessarily meet the limitations of the asserted claims upon approval and commercialization (Compl. ¶30).

’456 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method of treating seizures... comprising administering... a liquid oral pharmaceutical suspension... Defendant's proposed labeling for its ANDA Product will direct administration for the same therapeutic indication as ZONISADE®, thereby instructing users to perform the claimed method. ¶30, ¶39 col. 11:36-39
zonisamide in an amount of about 20 mg/mL; The Alkem ANDA Product is represented to have the same active ingredient and strength as ZONISADE®. ¶30 col. 11:41-42
a suspending agent comprising about 2 mg/mL to about 3.5 mg/mL xanthan gum and about 20 mg/mL of a combination of microcrystalline cellulose and sodium carboxymethylcellulose; As a generic equivalent seeking FDA approval, the Alkem ANDA Product is alleged to contain the same or equivalent formulation components to achieve bioequivalence. ¶30 col. 11:43-48
one or more buffering agents; and one or more pharmaceutically acceptable excipients, wherein the... excipients comprise a preservative; The Alkem ANDA Product is alleged to contain the same or equivalent formulation components. ¶30 col. 11:49-53
wherein the liquid oral pharmaceutical suspension has a pH of 3.5 to 5.0; The Alkem ANDA Product is alleged to possess the same physical and chemical characteristics, including pH. ¶30 col. 11:54-55
wherein the liquid oral pharmaceutical suspension is stable for at least 6 months when stored at 40° C. and 25% relative humidity. The Alkem ANDA Product must demonstrate stability to the FDA, which is alleged to meet this functional limitation. ¶30 col. 11:56-59

’333 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A liquid oral pharmaceutical suspension, comprising: zonisamide in an amount of about 20 mg/mL; The Alkem ANDA Product is represented to have the same active ingredient and strength as ZONISADE®. ¶30 col. 11:38-39
a suspending agent comprising about 2 mg/mL to about 3.5 mg/mL xanthan gum and about 20 mg/mL of a combination of microcrystalline cellulose and sodium carboxymethylcellulose; As a generic equivalent, the Alkem ANDA Product is alleged to contain the same or equivalent formulation components. ¶30 col. 11:40-45
one or more buffering agents; and one or more pharmaceutically acceptable excipients, wherein the... excipients comprise a preservative; The Alkem ANDA Product is alleged to contain the same or equivalent formulation components. ¶30 col. 11:46-50
wherein the liquid oral pharmaceutical suspension has a pH of 3.5 to 5.0... The Alkem ANDA Product is alleged to have the same pH. ¶30 col. 11:51-52
wherein the composition is stable for at least 6 months when stored at 40° C. and 25% relative humidity. The Alkem ANDA Product must demonstrate sufficient stability for FDA approval and is alleged to meet this limitation. ¶30 col. 11:52-55

Identified Points of Contention

  • Scope Questions: A central question will be whether Defendant’s formulation, which is not disclosed in the complaint, falls within the literal scope of the claims. The analysis may focus on whether Defendant has designed a bioequivalent product that uses different excipients, different concentrations, or a different pH to avoid the claimed ranges.
  • Technical Questions: The dispute will likely involve a comparison of the specific formulation of the Alkem ANDA Product against the claimed composition. The question is whether Alkem was able to achieve bioequivalence and stability using a formulation that is technically different from the one defined by the claims (e.g., by using a different suspending agent or achieving stability outside the claimed pH range).

V. Key Claim Terms for Construction

The complaint does not provide sufficient detail for a definitive analysis of claim construction disputes. However, based on the claim language, the following terms may become central to the case.

The Term: "about"

  • Context and Importance: This term modifies all key quantitative limitations (e.g., "about 20 mg/mL," "about 3.5 mg/mL"). The scope of "about" will be critical in determining whether Defendant’s formulation, if it deviates slightly from the recited values, still constitutes literal infringement. Practitioners may focus on this term because even minor variations in component concentrations could be the basis for a non-infringement defense.
  • Intrinsic Evidence for a Broader Interpretation: The specification discloses the invention in terms of general components and provides exemplary formulations, which may suggest that the precise numerical values are not the only embodiments that work (’456 Patent, col. 3:20-38).
  • Intrinsic Evidence for a Narrower Interpretation: The patents present specific stability data tied to a particular formulation (’456 Patent, col. 9-10, Tables 2 & 4). A party could argue that this data suggests the claimed stability is achieved only at or very near the exemplified numerical values, warranting a narrow construction of "about."

The Term: "stable for at least 6 months when stored at 40° C. and 25% relative humidity"

  • Context and Importance: This functional language in the independent claims defines the invention by what it does, not just what it is. The definition of "stable" will be a key issue. Is stability defined by total impurities, the absence of a particular degradant, physical appearance, or a combination of factors?
  • Intrinsic Evidence for a Broader Interpretation: The term "stable" could be construed according to its ordinary meaning in the pharmaceutical arts or by reference to regulatory standards for drug product shelf-life.
  • Intrinsic Evidence for a Narrower Interpretation: The specification provides detailed stability study results showing specific impurity levels (e.g., "Total Impurities (%)" of 0.10 or less) (’456 Patent, col. 10, Table 2). Parties may argue that "stable" should be defined by achieving these specific, low impurity profiles, effectively importing limitations from the examples into the claim.

VI. Other Allegations

Indirect Infringement

The complaint alleges facts supporting inducement to infringe, stating that Defendant’s proposed product labeling will direct and instruct medical providers and patients to use the ANDA Product in an infringing manner (Compl. ¶39). It also alleges there are no substantial non-infringing uses for the Alkem ANDA Product, which is a basis for contributory infringement (Compl. ¶35, ¶40, ¶45).

Willful Infringement

The complaint does not explicitly use the term "willful infringement." However, it alleges that Defendant had "actual and constructive knowledge" of the patents-in-suit prior to filing its ANDA and acted with "specific intent to infringe" (Compl. ¶35, ¶40, ¶45). Furthermore, the prayer for relief requests a finding that this is an "exceptional case" under 35 U.S.C. § 285, which could entitle Plaintiff to attorney's fees (Compl., Prayer for Relief ¶e).

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

  • A core issue will be one of formulation scope: has the Defendant formulated its generic product to be bioequivalent to ZONISADE® while successfully designing around the specific quantitative and compositional limitations of the asserted claims, particularly the precise identity and concentration ranges of the suspending agents and the claimed pH?
  • A second key question will be one of claim construction: how broadly will the term "about" be interpreted in the context of the claimed concentrations, and what technical criteria will be used to define the functional limitation of being "stable"? The outcome of these definitions may determine whether Defendant’s product infringes.
  • Finally, a central question for the defense, though not detailed in the complaint, will likely be patent validity: can Defendant prove by clear and convincing evidence that the claimed combination of known pharmaceutical excipients to create a liquid suspension of a known drug would have been obvious to a person of ordinary skill in the art at the time of the invention?