DCT
1:25-cv-00563
Azurity Pharma Inc v. Alkem Laboratories Ltd
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Azurity Pharmaceuticals, Inc. (Delaware)
- Defendant: Alkem Laboratories Ltd. (Republic of India)
- Plaintiff’s Counsel: Potter Anderson & Corroon LLP; Wilson Sonsini Goodrich & Rosati P.C.
- Case Identification: 1:25-cv-00563, D. Del., 05/07/2025
- Venue Allegations: Plaintiff alleges venue is proper because Defendant is a foreign corporation that may be sued in any judicial district.
- Core Dispute: Plaintiff alleges that Defendant’s submission of an Abbreviated New Drug Application (ANDA) to market a generic version of Plaintiff’s ZONISADE® product infringes patents related to liquid oral suspension formulations of zonisamide.
- Technical Context: The technology concerns pharmaceutical formulations for the anticonvulsant drug zonisamide, specifically creating a stable and palatable liquid oral suspension to serve patients who have difficulty swallowing solid pills.
- Key Procedural History: The litigation was initiated under the Hatch-Waxman Act, triggered by Defendant Alkem’s submission of ANDA No. 220352 to the FDA and its subsequent notice letter to Plaintiff Azurity. The complaint notes that the patents-in-suit are listed in the FDA’s Orange Book in connection with Azurity’s ZONISADE® product. The complaint also details a pre-suit dispute regarding the terms of a confidential access offer for the ANDA materials.
Case Timeline
| Date | Event |
|---|---|
| 2017-08-19 | Priority Date for ’456 and ’333 Patents |
| 2022-10-25 | U.S. Patent No. 11,478,456 Issued |
| 2022-12-20 | U.S. Patent No. 11,529,333 Issued |
| 2025-03-21 | Alkem sends Notice Letter regarding ANDA No. 220352 |
| 2025-05-07 | 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 Oct. 25, 2022)
The Invention Explained
- Problem Addressed: The patent addresses the challenge that the anticonvulsant drug zonisamide was commercially available only in solid dosage forms like capsules and tablets, which are difficult for certain patient populations, such as young children and the seriously ill, to swallow (ʼ456 Patent, col. 3:9-16).
- The Patented Solution: The invention provides a liquid oral pharmaceutical composition, specifically a suspension, of zonisamide. This formulation uses a combination of specific excipients—including suspending agents, buffering agents, and preservatives—to create a stable, palatable, and orally deliverable alternative to solid dosage forms, thereby improving patient access and compliance (ʼ456 Patent, col. 3:17-29; col. 4:50-61).
- Technical Importance: The development of a stable liquid formulation for an existing drug is significant as it expands the therapeutic options available to physicians and makes the medication accessible to patient groups who cannot use the solid form.
Key Claims at a Glance
- The complaint asserts infringement of "one or more claims" without specifying them (Compl. ¶28). Independent claim 1 is a representative method of use claim.
- Independent Claim 1: A method of treating seizures in a subject by administering a liquid oral pharmaceutical suspension with the following key characteristics:
- Zonisamide in an amount of about 20 mg/mL.
- 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.
- One or more buffering agents and one or more other pharmaceutically acceptable excipients, including a preservative.
- The suspension has a pH of 3.5 to 5.0.
- The suspension is stable for at least 6 months when stored at 40° C. and 25% relative humidity.
U.S. Patent No. 11,529,333 - Oral Pharmaceutical Composition Comprising Zonisamide and Process of Preparation Thereof (Issued Dec. 20, 2022)
The Invention Explained
- Problem Addressed: As with the related ’456 Patent, this patent addresses the lack of a commercially available liquid oral dosage form for the anticonvulsant zonisamide, noting the difficulty this presents for patients unable to swallow solid pills (ʼ333 Patent, col. 3:2-7).
- The Patented Solution: The invention is a liquid oral pharmaceutical suspension containing zonisamide. It achieves stability and proper suspension through a defined set of excipients, including a specific combination of suspending agents (xanthan gum and microcrystalline cellulose/sodium carboxymethylcellulose) and buffering agents to control pH (ʼ333 Patent, col. 4:15-32; col. 4:45-54).
- Technical Importance: This technology provides a specific formulation for a liquid version of zonisamide, enabling its administration to a broader patient population, particularly pediatric and geriatric patients.
Key Claims at a Glance
- The complaint asserts infringement of "one or more claims" without specification (Compl. ¶33). Independent claim 1 is a representative composition claim.
- Independent Claim 1: A liquid oral pharmaceutical suspension comprising:
- Zonisamide in an amount of about 20 mg/mL.
- 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.
- One or more buffering agents.
- One or more pharmaceutically acceptable excipients, wherein at least one is a preservative.
- The suspension has a pH of 3.5 to 5.0 and is stable for at least 6 months when stored at 40° C. and 25% relative humidity.
III. The Accused Instrumentality
- Product Identification: The accused instrumentality is the generic zonisamide oral suspension that is the subject of Alkem’s ANDA No. 220352 (the "Alkem ANDA Product") (Compl. ¶21).
- Functionality and Market Context: The Alkem ANDA Product is a proposed generic version of Azurity's ZONISADE® product, an FDA-approved anticonvulsant (Compl. ¶¶1, 11). The complaint alleges that by filing its ANDA, Alkem has represented to the FDA that its product has the same active ingredient, route of administration, dosage form, use, and strength as ZONISADE®, and that it is bioequivalent to ZONISADE® (Compl. ¶25). The purpose of the product is to provide a lower-cost, generic alternative for the treatment of partial onset seizures (Compl. ¶¶4, 11). No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
The complaint alleges that the act of filing the ANDA constitutes infringement under 35 U.S.C. § 271(e)(2)(A), and that the future commercial manufacture and sale of the Alkem ANDA Product will infringe the patents-in-suit (Compl. ¶¶28, 29, 33, 34). The infringement theory is predicated on the allegation that Alkem’s product is a generic copy of ZONISADE® and will therefore possess the features claimed in the patents.
’456 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| A method of treating seizures in a subject in need thereof, comprising administering to the subject a liquid oral pharmaceutical suspension | Alkem’s ANDA seeks approval for a generic zonisamide oral suspension for the same use as ZONISADE®, which is an adjunctive therapy for the treatment of partial onset seizures. | ¶¶11, 25 | col. 11:36-40 |
| zonisamide in an amount of about 20 mg/mL; | The Alkem ANDA Product allegedly has the same active ingredient and strength as ZONISADE®, which is formulated with zonisamide at the claimed concentration. | ¶25 | 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; | The Alkem ANDA Product, by being a bioequivalent copy of ZONISADE®, will allegedly contain the same excipients, including the claimed suspending agents in the claimed amounts, necessary to achieve the required formulation characteristics. | ¶25 | col. 11:43-48 |
| one or more buffering agents; and one or more pharmaceutically acceptable excipients, wherein the one or more pharmaceutically acceptable excipients comprise a preservative; | The Alkem ANDA Product will allegedly contain the same or equivalent buffering agents and preservatives as ZONISADE® to achieve the required pH and stability. | ¶25 | col. 11:49-53 |
| wherein the liquid oral pharmaceutical suspension has a pH of 3.5 to 5.0; | The Alkem ANDA Product will allegedly have a pH within the claimed range to match the formulation of ZONISADE®. | ¶25 | col. 11:54-56 |
| 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 gain FDA approval, and it is alleged that this stability will meet the parameters defined in the claim. | ¶25 | col. 11:57-60 |
- Identified Points of Contention:
- Technical Questions: A primary question is whether the formulation detailed in Alkem's confidential ANDA submission literally meets every recited concentration and component limitation. Infringement will depend on the precise identity and quantity of excipients in Alkem's formulation, which is not yet detailed in the public record.
- Scope Questions: The interpretation of the term "about" as applied to the concentrations of zonisamide and the suspending agents may be a central point of dispute. The parties may contest whether Alkem's specific concentrations, if not identical to the patent's examples, fall within the scope of "about."
’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 alleged to be a liquid oral suspension containing the same active ingredient at the same strength as the branded product. | ¶25 | col. 11:37-38 |
| 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; | To achieve bioequivalence with ZONISADE®, the Alkem ANDA Product is alleged to contain the same or equivalent suspending agents in the claimed amounts. | ¶25 | col. 11:39-44 |
| one or more buffering agents; and one or more pharmaceutically acceptable excipients, wherein the one or more pharmaceutically acceptable excipients comprise a preservative; | The Alkem ANDA Product is alleged to contain the necessary buffering agents and preservatives to match the stability and characteristics of ZONISADE®. | ¶25 | col. 11:45-49 |
| wherein the liquid oral pharmaceutical suspension has a pH of 3.5 to 5.0... | As a copy of ZONISADE®, the Alkem ANDA Product is alleged to be formulated to have a pH within the claimed range. | ¶25 | col. 11:50-52 |
| ...wherein the composition is stable for at least 6 months when stored at 40° C. and 25% relative humidity. | Alkem must demonstrate sufficient stability to the FDA, and it is alleged that the ANDA product will meet the stability criteria recited in the claim. | ¶25 | col. 11:52-55 |
- Identified Points of Contention:
- Technical Questions: As with the ’456 patent, the central factual question will be whether Alkem's product formulation, once disclosed, contains the exact combination of excipients in the claimed amounts. Any deviation could form the basis of a non-infringement defense.
- Scope Questions: The meaning of "a combination of microcrystalline cellulose and sodium carboxymethylcellulose" could be disputed. For instance, a question may arise if Alkem uses a pre-mixed commercial product versus combining the components individually, and whether that still constitutes the claimed "combination."
V. Key Claim Terms for Construction
- The Term: "about" (appearing in claims of both patents, e.g., "about 20 mg/mL," "about 2 mg/mL to about 3.5 mg/mL")
- Context and Importance: The term "about" modifies all key concentration limitations. Its construction is critical because if Alkem's formulation uses concentrations that are close but not identical to the recited values (e.g., 1.9 mg/mL xanthan gum), the infringement analysis will depend entirely on how much variation "about" permits. Practitioners may focus on this term to either broaden the scope to capture minor deviations or narrow it to require near-exactitude.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification uses the term "about" consistently when reciting ranges and amounts, suggesting that the inventors did not intend to be limited to the precise numerical values stated (e.g., ’456 Patent, col. 7:35, col. 7:43). This usage could support an interpretation that encompasses standard manufacturing and measurement tolerances.
- Evidence for a Narrower Interpretation: The exemplary formulation in Table 1 of both patents provides exact values (e.g., "3.50" mg/mL for Xanthan gum, "20.00" for Zonisamide) without the "about" qualifier (’456 Patent, col. 8:10-20, Table 1). A party could argue these examples demonstrate the optimal, and therefore intended, concentrations, thus limiting the scope of "about" to values very close to those exemplified.
VI. Other Allegations
- Indirect Infringement: The complaint alleges that Alkem had actual and constructive knowledge of the patents-in-suit prior to filing its ANDA (Compl. ¶¶30, 35). It further alleges that Alkem will induce infringement by others (e.g., patients and physicians) because its proposed product labeling will instruct users to administer the drug in a manner that infringes the method claims of the ’456 patent (Compl. ¶34). The complaint also asserts there are no substantial non-infringing uses for the Alkem ANDA Product (Compl. ¶¶30, 35).
- Willful Infringement: The complaint does not explicitly plead "willful infringement," but it does request a finding that this is an "exceptional case" under 35 U.S.C. § 285, which allows for the award of attorneys' fees (Compl. p. 9, ¶e). The factual basis for this allegation is Alkem's alleged pre-suit knowledge of the patents and its decision to file an ANDA seeking approval to market its product before patent expiration (Compl. ¶¶30, 35).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of formulation identity: once Alkem’s ANDA is produced in discovery, will its zonisamide suspension be found to contain the precise combination and concentrations of suspending agents and other excipients required by the asserted claims, or are there material differences that support a non-infringement position?
- A key legal question will be one of definitional scope: how broadly will the court construe the term "about"? The case may turn on whether Alkem’s chosen concentrations, if different from the patents' examples, are nonetheless captured by a reasonable interpretation of this term in the context of the specification.
- A final dispositive question will be one of validity: while not yet raised by the defendant, the litigation will almost certainly involve challenges to the validity of the patents-in-suit based on prior art related to other liquid drug formulations, which could render the infringement analysis moot.