Sun Pharmaceutical Industries, Inc. v. Nivagen Pharmaceuticals, Inc.

1. Case Identification

• Case Number: IPR2025-00893
• Patent #: 11,878,076
• Filed: April 22, 2025
• Petitioner(s): Sun Pharmaceutical Industries, Inc.
• Patent Owner(s): Nivagen Pharmaceuticals, Inc.
• Challenged Claims: 1-20

2. Patent Overview

• Title: Lyophilized compositions of phenobarbital sodium salt
• Brief Description: The ’076 patent relates to storage-stable pharmaceutical products comprising lyophilized phenobarbital sodium. The claims are directed to specific dosages and purity levels, defined by minimal amounts of degradation products (impurities) after storage under specified conditions.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are obvious over PIF in view of Parker and West-Ward.

• Prior Art Relied Upon: Pharmaceutical Interview Form for Nobelbar (“PIF”); Application # 2017/0143719 (“Parker”); and the DailyMed label for a West-Ward Pharmaceutical product (“West-Ward”).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the combination of these references taught all elements of the challenged claims. PIF, a Japanese publication for the commercial product Nobelbar, disclosed a stable, lyophilized, high-purity phenobarbital sodium product for intravenous injection in single-use vials. Parker taught that phenobarbital sodium is susceptible to hydrolytic degradation, forming specific toxic impurities like phenylethylacetylurea (PEAU), 2-ethyl-2-phenylmalonamide (2EPMM), and alpha-phenylbutyrylguanidine (PBG). West-Ward disclosed commercially available phenobarbital sodium injections in standard U.S. dosages, including 65 mg and 130 mg. Petitioner asserted that a person of ordinary skill in the art (POSA) would look to these standard dosages and known degradation pathways when developing a stable formulation like the one suggested by PIF.
  • Motivation to Combine: A POSA would combine these references to develop a stable, highly pure, lyophilized phenobarbital sodium composition. The motivation was to increase stability and minimize known harmful impurities (taught by Parker) for a known effective drug, particularly for sensitive neonatal populations. Lyophilization (taught by PIF) was a well-known technique to prevent hydrolysis. A POSA would formulate the product in well-established, safe, and effective dosages (taught by West-Ward and Parker) as a matter of routine development.
  • Expectation of Success: A POSA would have a high expectation of success because PIF demonstrated that a stable, lyophilized phenobarbital sodium product was already commercially successful in Japan. Parker identified the specific impurities to monitor, and standard stability testing protocols (e.g., storage at 40°C for 6 months) were routine. Therefore, achieving the claimed low impurity levels was merely the expected result of applying known purification and stabilization techniques to a known drug.

Ground 2: Claims 1-20 are anticipated by the ’608 Application.

• Prior Art Relied Upon: Application # 2021/0085608 (“’608 application”).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground is predicated on a priority date challenge. Petitioner argued the ’076 patent is not entitled to its earliest claimed priority date of September 20, 2019. The original applications (’511 provisional and ’881 non-provisional) allegedly disclosed only amorphous phenobarbital sodium and expressly excluded compositions containing organic solvents, describing these features as advantageous. However, the challenged claims of the ’076 patent, which issued from a later continuation-in-part (’914 CIP application), are broad enough to encompass both crystalline and amorphous forms, as well as compositions containing organic solvents.
  • Key Aspects: Petitioner contended this broadening constitutes new matter, breaking the priority chain. Consequently, the challenged claims are only entitled to the June 30, 2022 filing date of the ’914 CIP application. The ’608 application, which published on March 25, 2021, and originated from the Patent Owner’s own ’881 application, thus became §102(a) prior art. Petitioner asserted that the ’608 application explicitly discloses all limitations of claims 1-20, including the specific dosages, the use of single-dose vials, the sterile and lyophilized nature, the purity levels, and the maximum impurity thresholds under the specified stability testing conditions.

Ground 3: Claims 1-20 are obvious over the ’608 Application and the ordinary knowledge of a POSA.

• Prior Art Relied Upon: ’608 application and the ordinary knowledge of a POSA.
• Core Argument for this Ground:
  • Prior Art Mapping: As an alternative to Ground 2, Petitioner argued that if any element of the challenged claims is not expressly disclosed in the ’608 application, it would have been obvious to a POSA. The ’608 application taught that its described compositions were "desirable" and had superior stability.
  • Motivation to Combine: A POSA would have been motivated to take the stable, lyophilized compositions disclosed in the ’608 application and optimize them using routine techniques. This includes aliquoting the product into standard single-use dosages (e.g., 65 mg, 100 mg, 130 mg) and conducting standard stability tests to confirm and ensure the low levels of impurities (PEAU, 2EPMM, PBG) and long-term shelf life (e.g., 24 months) recited in the claims.
  • Expectation of Success: Given that the ’608 application already disclosed compositions with high purity and stability, a POSA would reasonably expect that applying standard pharmaceutical development practices—such as well-known stability testing protocols and formulation of standard dosages—would successfully result in a product meeting all claim limitations.

4. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under §314(a) or §325(d) is unwarranted. The petition asserted that its grounds are not cumulative of art considered during prosecution, as the primary reference for Ground 1 (PIF) was not before the examiner.
• Furthermore, Petitioner argued that the examiner never identified the Patent Owner's own ’608 application as prior art, and thus the invalidating disclosures central to Grounds 2 and 3 were never addressed during prosecution.

5. Relief Requested

• Petitioner requests the institution of an inter partes review and the cancellation of claims 1-20 of the ’076 patent as unpatentable.