Amneal Pharmaceuticals Inc v. Nivagen Pharmaceuticals Inc

1. Case Identification

• Case #: IPR2025-00731
• Patent #: 11,925,661
• Filed: April 11, 2025
• Petitioner(s): Amneal Pharmaceuticals, Inc.
• Patent Owner(s): Nivagen Pharmaceuticals, Inc.
• Challenged Claims: 1-20

2. Patent Overview

• Title: Ready-to-Use Potassium Phosphates in Sodium Chloride Injection
• Brief Description: The ’661 patent relates to sterile, ready-to-use (RTU) aqueous potassium phosphate solutions for phosphorus replacement therapy. The solutions comprise potassium phosphate and sodium chloride within specific concentration ranges for phosphorus, potassium, and aluminum, and are formulated to a specific pH range.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are anticipated and/or obvious over Nivagen-1

• Prior Art Relied Upon: Nivagen-1 (Application # 2022/0110969).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the ’661 patent is not entitled to its priority date, making its parent application, Nivagen-1, prior art under 35 U.S.C. §102(a)(1). Nivagen-1 was asserted to disclose every limitation of the challenged claims. Specifically, Nivagen-1 taught a sterile RTU aqueous solution comprising potassium phosphates and sodium chloride, with a phosphorus concentration of 15 mmol/100 mL (the upper limit of the claimed range), an aluminum content of less than 50 mcg/L, and a pH between 6.2 and 6.8. Petitioner contended that disclosure of the range endpoint anticipates the claim, or at minimum renders it obvious. Nivagen-1 was also shown to disclose the claimed molar ratios of phosphate species, stability after storage, and packaging in flexible multilayer polyolefin containers, thereby anticipating or rendering obvious all challenged composition, product, and method claims.

Ground 2: Claims 1-8, 11-13, and 17-20 are obvious over the CMP Art and Terlevich, optionally in view of Ogawa

• Prior Art Relied Upon: The CMP Art, consisting of CMP-PCT (WO 2020/081118) and CMP-FDA (an FDA drug label); Terlevich (a 2003 journal article); and optionally Ogawa (a 2013 journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that CMP-PCT taught a concentrated, sterile potassium phosphate composition designed to solve prior art particulate formation issues. However, the CMP-PCT solution required dilution before administration. Terlevich taught the clinical benefits of using a premixed, RTU potassium phosphate solution ("Phosphates Polyfusor") at a concentration suitable for direct infusion (10 mmol/100 mL), which falls within the ’661 patent’s claimed range. The combination of CMP-PCT and Terlevich thus rendered obvious a sterile, RTU potassium phosphate solution. The CMP-FDA label and general knowledge supplied the addition of sodium chloride for tonicity. To meet the low aluminum limitation, Petitioner asserted that CMP-PCT already taught using ultra-low levels (0.2-0.3 ppm) and that Ogawa further taught that aluminum should be kept below 50 ppb (50 mcg/L) to completely prevent particle formation.
  • Motivation to Combine: A POSITA would combine the stable, low-particulate formulation of CMP-PCT with the convenient and safer RTU administration method taught by Terlevich. The goal would be to create a product that is both stable on the shelf and easy for clinicians to use, reducing preparation errors. A POSITA would be further motivated to apply Ogawa's findings to the CMP-PCT formulation to enhance its stability by minimizing aluminum-induced precipitation.
  • Expectation of Success: Creating an RTU solution by diluting the CMP-PCT concentrate to the well-known concentration taught in Terlevich was presented as a simple and predictable step. All components were known to be compatible, and the practice of formulating RTU parenteral solutions was routine.

Ground 3: Claims 9-20 are obvious over the Ground 2 Art and Nevakar

• Prior Art Relied Upon: The combination of references from Ground 2, further in view of Nevakar (Application # 2019/0290602).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground addressed claims requiring specific packaging, such as a flexible multilayer polyolefin container (claim 9) and a secondary metallized overwrap (claim 10). Petitioner argued the Ground 2 art combination resulted in a stable RTU solution, and Nevakar taught packaging for such ready-to-administer compositions. Nevakar disclosed the use of flexible IV bags, including multilayer polyolefin containers with volumes between 100-1,000 mL, further enclosed in a metallized overwrap to enhance long-term stability.
  • Motivation to Combine: A POSITA, having formulated the RTU solution taught by the Ground 2 art, would seek an optimal container system to ensure long-term stability, a key goal of CMP-PCT. Nevakar provided exactly such a system, teaching that its multilayer containers and metallized overwraps were well-suited for RTU solutions and prevent moisture and oxygen ingress. A POSITA would combine these known technologies to improve the shelf-life and integrity of the final product.
  • Expectation of Success: Packaging a finished RTU solution into a commercially available, specialized container system as taught by Nevakar was argued to be a routine step with a high expectation of success.

4. Key Technical Contentions (Beyond Claim Construction)

• Lack of Written Description Support for Priority Claim: A central contention of the petition was that the ’661 patent is not entitled to its claimed priority date. Petitioner argued the parent ’001 application failed to provide written description support for the claimed phosphorus concentration range of "between 1.5 mmol/100 mL and 15 mmol/100 ml." The parent application allegedly disclosed only a single concentration for its RTU solutions: 15 mmol/100 mL. Petitioner asserted the lower limit of 1.5 mmol/100 mL was new matter added in the application that led to the ’661 patent, thus making the patent’s effective filing date September 5, 2023, and rendering its own parent application (Nivagen-1) prior art.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §314(a) and the Fintiv factors is unwarranted. The petition asserted that the co-pending district court litigation is in its infancy, with no scheduling order entered, no discovery conducted, and no trial date set. Petitioner noted the presiding judge grants over 70% of motions to stay pending IPR and has an average time to trial of three years, well after a Final Written Decision (FWD) would issue. Petitioner also stipulated under Sotera not to pursue in litigation any grounds raised or reasonably available. Finally, Petitioner argued that denial under §325(d) is improper because the prior art asserted in the petition is different from the art considered during prosecution.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of Patent 11,925,661 as unpatentable.