DCT

1:11-cv-01171

Senju Pharmaceutical Co Ltd v. Apotex Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:11-cv-01171, D. Del., 11/28/2011
  • Venue Allegations: Venue is alleged based on Defendants' business activities within Delaware and their consent to jurisdiction in a previous, related litigation in the same district.
  • Core Dispute: Plaintiffs allege that Defendants' submission of an Abbreviated New Drug Application (ANDA) to the FDA for a generic gatifloxacin ophthalmic solution constitutes an act of infringement of a reexamined patent covering the drug's formulation.
  • Technical Context: The technology concerns aqueous formulations for ophthalmic antibiotics, focusing on overcoming challenges related to the drug's low solubility and corneal permeability at a physiologically comfortable pH.
  • Key Procedural History: The asserted patent was the subject of prior litigation between the same parties, where several original claims were found invalid. Following that decision, Plaintiffs initiated an ex parte reexamination at the USPTO, which resulted in the cancellation of some original claims, the amendment of another, and the issuance of new claims, which are the subject of the current lawsuit.

Case Timeline

Date Event
1998-08-21 '045 Patent Priority Date
2001-12-25 '045 Patent Issue Date
2007-07-19 Apotex files ANDA No. 79-084 for generic gatifloxacin ophthalmic solution
2007-10-17 Apotex notifies Plaintiffs of its ANDA filing
2010-06-21 D. Del. finds original claims 1-3 and 6-9 of '045 Patent invalid in prior case
2011-02-25 Plaintiffs file request for reexamination of the '045 Patent
2011-08-19 Apotex receives final FDA approval for its ANDA
2011-10-25 USPTO issues reexamination certificate for the '045 Patent with amended/new claims
2011-11-28 Complaint Filing Date

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

  • Patent Identification: U.S. Patent No. 6,333,045, "Aqueous Liquid Pharmaceutical Composition Comprised of Gatifloxacin," issued December 25, 2001 (as reexamined October 25, 2011).

The Invention Explained

  • Problem Addressed: The patent's background describes the difficulty in creating an effective ophthalmic solution using the antibiotic gatifloxacin. Specifically, gatifloxacin has very low solubility at a near-neutral pH suitable for eye drops, which can cause irritation if the pH is adjusted to acidic or alkaline ranges to dissolve the drug ('045 Patent, col. 2:5-14). Additionally, ensuring the drug effectively passes through the cornea is a persistent challenge in ophthalmic drug design ('045 Patent, col. 1:27-34).
  • The Patented Solution: The invention is a specific formulation that adds the chelating agent disodium edetate to an aqueous gatifloxacin solution. The patent teaches that this combination solves the identified problems by improving gatifloxacin's solubility at a physiologically acceptable pH, enhancing its corneal permeability, preventing the precipitation of drug crystals during storage, and preventing discoloration ('045 Patent, Abstract; col. 1:55-58; col. 2:11-17).
  • Technical Importance: This formulation technology enables a stable, effective, and non-irritating gatifloxacin eye drop, which is critical for patient compliance and therapeutic success in treating eye infections.

Key Claims at a Glance

  • The complaint asserts independent claims 6 (as amended) and 12 (newly added during reexamination), as well as dependent claims 13, 14, 15, and 16 (Compl. ¶36).
  • Independent Claim 6 (method claim):
    • A method for raising corneal permeability of an aqueous pharmaceutical Gatifloxacin eye drop solution
    • comprising Gatifloxacin or its salt
    • having a pH of from above 5 to about 6
    • containing from about 0.3 to about 0.8 w/v% Gatifloxacin or its salt
    • which comprises incorporating about 0.01 w/v% disodium edetate into said Gatifloxacin eye drop solution
  • Independent Claim 12 (composition claim):
    • An aqueous liquid pharmaceutical eye drop composition
    • which comprises from about 0.3 to about 0.8 w/v% Gatifloxacin or its salt
    • about 0.01 w/v% disodium edetate
    • and wherein the aqueous liquid pharmaceutical composition has a pH of from about 5 to about 6

III. The Accused Instrumentality

Product Identification

  • The accused instrumentality is the "gatifloxacin ophthalmic solution" that is the subject of Defendant Apotex's Abbreviated New Drug Application (ANDA) No. 79-084 (Compl. ¶28, ¶36).

Functionality and Market Context

  • The complaint alleges that Apotex's product is a generic version of Plaintiffs' branded gatifloxacin ophthalmic solutions, which are marketed under FDA-approved New Drug Applications (NDAs) (Compl. ¶26, ¶28). The filing of the ANDA is a statutory act of infringement under 35 U.S.C. § 271(e)(2), signifying Apotex's intent to commercially manufacture, use, and sell the generic drug in the United States upon approval, which it received on August 19, 2011 (Compl. ¶31, ¶36).

IV. Analysis of Infringement Allegations

The complaint does not provide a detailed element-by-element infringement analysis or a claim chart. The infringement allegation is statutory, based on Defendant's filing of ANDA No. 79-084 for a gatifloxacin ophthalmic solution which Plaintiffs allege is claimed in the '045 Patent (Compl. ¶36, ¶39).

No probative visual evidence provided in complaint.

  • Identified Points of Contention:
    • Scope Questions: A central question will be whether the specific formulation detailed in Apotex's confidential ANDA filing falls within the scope of the asserted claims, particularly the specific concentration and pH ranges added during reexamination. The interpretation of the term "about" will be critical to this analysis. For instance, does Apotex's formulation, as described in its ANDA, have a "pH of from about 5 to about 6" and contain "about 0.01 w/v% disodium edetate"?
    • Technical Questions: The dispute will likely focus on the precise chemical composition of Apotex's generic product. Discovery will be needed to determine the exact concentrations of gatifloxacin and disodium edetate, the product's pH, and the presence of any other excipients that might be relevant to the infringement analysis.

V. Key Claim Terms for Construction

  • The Term: "about 0.01 w/v% disodium edetate"

  • Context and Importance: This limitation appears in both asserted independent claims 6 and 12 and defines a specific concentration of a key ingredient. Because this term was introduced during reexamination to narrow the claims, its construction will be pivotal. Infringement may turn entirely on whether the concentration in Apotex's product is close enough to 0.01% to be considered "about" that value.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The specification discloses a broader preferred range of disodium edetate from "0.005 to 0.1 w/v %" and an even more preferred range of "0.01 to 0.1 w/v %," which may support an interpretation of "about 0.01%" that covers a scope beyond the exact number ('045 Patent, col. 2:58-61).
    • Evidence for a Narrower Interpretation: Parties may argue that selecting "about 0.01%" during reexamination, in the face of prior art that invalidated broader claims, was a deliberate and specific choice. The patent's own data in Table 4 shows distinct results for different concentrations (0.001%, 0.005%, 0.01%, 0.05%), which could be used to argue that 0.01% is a critical, not arbitrary, value ('045 Patent, col. 4:10-23).

  • The Term: "a pH of from about 5 to about 6"

  • Context and Importance: This pH range, also added during reexamination, is a critical parameter for both the method and composition claims. Similar to the concentration term, the meaning of "about" in this context could either capture or exclude Apotex's formulation.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The specification describes a general pH range of 5 to 8, with a preferred range of 5.5 to 7.5 ('045 Patent, col. 2:61-63). A party could argue this context informs a more flexible reading of the claimed "about 5 to about 6" range.
    • Evidence for a Narrower Interpretation: A party could contend that the patentee's decision to claim the narrow "about 5 to about 6" range, despite disclosing broader ranges, was a specific amendment to overcome prior art and should be construed narrowly. The patent includes examples with specific pH values within or near this range, such as 5.5 and 6.0, which may be cited to anchor the interpretation ('045 Patent, col. 4:40, col. 5:45).

VI. Other Allegations

  • Indirect Infringement: The complaint seeks a declaration that future commercialization of the ANDA product will constitute induced or contributory infringement under 35 U.S.C. § 271(b) and (c) (Compl. ¶47). This allegation is predicated on the idea that Apotex, by selling the product with its labeling and instructions, would actively encourage and enable direct infringement by end-users like doctors and patients.
  • Willful Infringement: The complaint does not use the word "willful," but it establishes a basis for such a claim by alleging that Apotex has been aware of the '045 patent since at least 2007 due to the prior litigation (Compl. ¶18, ¶30). The allegation that Apotex continued its efforts to market a generic version even after the patent was reexamined and new claims were issued could be used to support a finding of post-suit willfulness, potentially making the case "exceptional" and justifying an award of attorneys' fees as requested in the prayer for relief (Compl., Prayer ¶E).

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

  • A core issue will be one of claim scope after reexamination: Can the term "about," as it applies to the specific concentration and pH limitations added during reexamination, be interpreted to cover the precise formulation described in Apotex's confidential ANDA, or did the patentee surrender broader scope during reexamination to secure the claims?
  • A key evidentiary question will be one of factual correspondence: Does the chemical composition of Apotex's FDA-approved generic product—specifically its disodium edetate concentration and pH level—fall squarely within the numerical ranges of the asserted claims? The outcome of the case will likely depend on the answer to this narrow, technical question.
  • A central legal question will be the impact of the prior litigation and reexamination history: To what extent will the arguments and claim amendments made by the patentee to overcome the initial invalidity judgment and secure the reexamined claims now limit its ability to prove infringement against Apotex's product under the doctrine of equivalents?