PTAB

IPR2025-00893

Sun Pharmaceutical Industries Inc v. Nivagen Pharmaceuticals Inc

Log In
Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Lyophilized compositions of phenobarbital sodium salt
  • Brief Description: The ’076 patent relates to storage-stable pharmaceutical products comprising lyophilized (freeze-dried) phenobarbital sodium compositions. The claims are directed to specific dosage amounts, high purity levels (no less than 98% phenobarbital sodium), and low levels of specific degradation impurities after storage under defined conditions.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are obvious over PIF, Parker, and West-Ward.

  • Prior Art Relied Upon: PIF (a 2011 Pharmaceutical Interview Form for Nobelbar), Parker (Application # 2017/0143719), and West-Ward (a 2015 DailyMed drug label).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the combination of these references taught all elements of the challenged claims. PIF disclosed Nobelbar, a commercially available, high-purity, sterile, lyophilized phenobarbital sodium product in single-use vials, demonstrating its storage stability. Parker taught that phenobarbital sodium is susceptible to hydrolysis, which forms the specific toxic impurities recited in the claims (PEAU, 2EPMM, and PBG), and that stability testing under accelerated conditions (e.g., 40° C. for 6 months) is standard for monitoring such degradation. West-Ward disclosed commercially available phenobarbital sodium injections in dosages (65 mg, 130 mg) that fall within the claimed ranges.
    • Motivation to Combine (for §103 grounds): Petitioner asserted a person of ordinary skill in the art (POSA) would combine these teachings to develop a stable, highly pure, lyophilized phenobarbital sodium product. A POSA would have started with a known successful product like Nobelbar (from PIF), understood the specific degradation pathways and testing protocols from Parker, and formulated the product in well-known, clinically relevant dosages as taught by West-Ward and Parker. Lyophilization was a well-known and obvious technique to enhance the stability of a drug known to degrade in the presence of water.
    • Expectation of Success (for §103 grounds): A POSA would have had a high expectation of success because PIF already demonstrated a commercially successful lyophilized product, lyophilization was a routine method for improving stability, and the combination involved optimizing known parameters like dosage and purity, which is standard pharmaceutical development.

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

  • Prior Art Relied Upon: The ’608 Publication (Application # 2021/0085608).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that the ’608 patent application, which published on March 25, 2021, is prior art under 35 U.S.C. §102 and anticipates all challenged claims. The core of this argument is that the ’076 patent is not entitled to its claimed priority date earlier than June 30, 2022. The parent applications ("Original Applications") allegedly lacked written description support for the full scope of the challenged claims because they expressly excluded compositions containing organic solvents and were strictly limited to amorphous phenobarbital sodium. Because the challenged claims are broader and are not so limited, they are only entitled to the filing date of the continuation-in-part application that introduced this new matter. Since the ’608 Publication published more than a year before this effective priority date, it qualifies as prior art. Petitioner contended the ’608 Publication expressly discloses all limitations, including storage-stable lyophilized compositions, single-use vials, claimed dosages, high purity, and impurity levels below the claimed thresholds after accelerated stability testing (40° C. for 6 months).
    • Key Aspects: This ground hinges on breaking the patent's priority chain by demonstrating that the Patent Owner broadened the claims beyond the scope of the original disclosure.

  • Additional Grounds: Petitioner asserted an additional ground that claims 1-20 are obvious over the ’608 Publication in view of the ordinary knowledge of a POSA. This argument relied on the same priority date challenge and contended that to the extent any minor claim element was not explicitly disclosed in the ’608 Publication, it would have been obvious to a POSA to implement.

4. Key Technical Contentions (Beyond Claim Construction)

  • Lack of Written Description and Priority Date Entitlement: The central technical contention underpinning Ground 2 is that the ’076 patent is not entitled to its earliest claimed priority date. Petitioner argued that the parent applications provided a narrow disclosure, teaching an invention limited to amorphous phenobarbital sodium that expressly excluded organic solvents, which were described as undesirable. The challenged claims of the ’076 patent are broader, encompassing crystalline forms and compositions with organic solvents. Petitioner argued this expansion constitutes new matter, resetting the critical date for prior art purposes to the filing date of the later continuation-in-part application (June 30, 2022).

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under §314(a) or §325(d) would be inappropriate. The petition asserted that the primary prior art references for its challenges (PIF and the ’608 Publication) were not substantively considered during the original prosecution. While a reference related to the PIF product was part of a third-party submission, the Examiner did not address or discuss it. Furthermore, the Examiner did not identify the ’608 Publication—the Patent Owner’s own prior publication—as prior art. Thus, the petition presents new arguments and art that were not before the Examiner.

6. Relief Requested

  • Petitioner requests the institution of an inter partes review and the cancellation of claims 1-20 of Patent 11,878,076 as unpatentable.