DCT
1:24-cv-00065
Eagle Pharma Inc v. Slayback Pharma LLC
Key Events
Amended Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Eagle Pharmaceuticals, Inc. and Eagle Sub1 LLC (Delaware)
- Defendant: Slayback Pharma LLC and Azurity Pharmaceuticals, Inc. (Delaware)
- Plaintiff’s Counsel: McCarter & English, LLP; Latham & Watkins LLP
- Case Identification: 1:24-cv-00065, D. Del., 06/12/2025
- Venue Allegations: Venue is alleged to be proper in the District of Delaware because both Defendant entities are incorporated in Delaware and therefore reside in the district.
- Core Dispute: Plaintiff alleges that Defendants’ VIVIMUSTA® product, a generic bendamustine hydrochloride injection, infringes two patents related to stable, non-aqueous liquid formulations of the drug.
- Technical Context: The technology concerns pharmaceutical formulations designed to solve the known instability of the chemotherapy drug bendamustine in aqueous solutions, thereby providing a ready-to-use liquid product that avoids the need for time-sensitive reconstitution of a lyophilized powder.
- Key Procedural History: The complaint notes that Defendant Slayback has been involved in prior patent litigation with Plaintiff concerning related patents in the same family as the patents-in-suit. Plaintiff also alleges providing Defendants with notice of the asserted patents on the respective days they were issued.
Case Timeline
| Date | Event |
|---|---|
| 2010-01-28 | Priority Date (’783 & ’214 Patents) |
| 2022-12-07 | FDA grants approval for Defendants' VIVIMUSTA® product |
| 2023-12-19 | U.S. Patent No. 11,844,783 Issues |
| 2023-12-20 | Plaintiff sends letter to Defendant Slayback regarding the ’783 Patent |
| 2024-01-16 | U.S. Patent No. 11,872,214 Issues |
| 2024-01-16 | Plaintiff sends letter to Defendant Slayback regarding the ’214 Patent |
| 2025-06-12 | Plaintiff files Second Amended Complaint |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 11,844,783 - "Formulations of Bendamustine" (Issued Dec. 19, 2023)
The Invention Explained
- Problem Addressed: The patent’s background section states that bendamustine, an active ingredient in cancer treatments, exhibits rapid degradation in aqueous solutions. Commercially available products at the time were lyophilized (freeze-dried) powders that required reconstitution before administration, a process described as “clinically inconvenient” and having “implications of chemical instability.” (’783 Patent, col. 1:49-65).
- The Patented Solution: The invention provides long-term, storage-stable liquid formulations of bendamustine that are non-aqueous. The solution comprises bendamustine, a pharmaceutically acceptable fluid containing polyethylene glycol (PEG) and/or propylene glycol (PG), and a “stabilizing amount of an antioxidant” such as thioglycerol. (’783 Patent, Abstract; col. 3:1-7). This combination is described as creating a ready-to-use formulation that is substantially free of impurities after at least 15 months of storage. (’783 Patent, col. 2:20-26).
- Technical Importance: The development of a stable, ready-to-use liquid formulation of bendamustine aimed to improve clinical convenience and safety by eliminating the need for on-site reconstitution of a lyophilized powder. (Compl. ¶29; ’783 Patent, col. 1:63-65).
Key Claims at a Glance
- The complaint asserts infringement of at least independent Claim 1. (Compl. ¶62).
- The essential elements of Claim 1 of the ’783 Patent, a method of treatment, include:
- Providing a liquid bendamustine-containing composition with a bendamustine concentration from about 20 mg/mL to about 60 mg/mL.
- The composition contains a “pharmaceutically acceptable fluid consisting of polyethylene glycol” and optionally other specified solvents like propylene glycol or ethanol.
- The composition contains a “stabilizing amount of an antioxidant.”
- The total impurities from degradation are less than about 5% peak area response as measured by HPLC after at least 15 months of storage at 5° C to 25° C.
- The method includes the steps of diluting the composition and intravenously administering it to a human.
- The complaint alleges infringement of "one or more claims, including at least claim 1," thereby reserving the right to assert other claims. (Compl. ¶62).
U.S. Patent No. 11,872,214 - "Formulations of Bendamustine" (Issued Jan. 16, 2024)
The Invention Explained
- Problem Addressed: The ’214 Patent shares a common specification with the ’783 Patent and addresses the same problem of bendamustine’s instability in aqueous solutions and the clinical inconvenience of reconstituting lyophilized powders. (’214 Patent, col. 1:49-65).
- The Patented Solution: The ’214 Patent also describes a long-term, storage-stable, non-aqueous liquid formulation of bendamustine comprising the drug, a PEG/PG-based fluid, and an antioxidant. (’214 Patent, Abstract). The claims of the ’214 patent are directed to the composition itself contained within a sterile vial, rather than a method of using it.
- Technical Importance: The invention provides a stable, ready-to-use bendamustine product in its final container, intended to simplify the process for healthcare providers and reduce the risk of preparation errors or degradation. (Compl. ¶29; ’214 Patent, col. 1:63-65).
Key Claims at a Glance
- The complaint asserts infringement of at least independent Claim 1. (Compl. ¶73).
- The essential elements of Claim 1 of the ’214 Patent, a product claim, include:
- A sterile vial containing a liquid bendamustine-containing composition.
- The composition contains about 100 mg of bendamustine at a concentration from about 25 mg/mL.
- The composition contains a “pharmaceutically acceptable fluid consisting of polyethylene glycol” and optionally other specified solvents.
- The composition contains a “stabilizing amount of antioxidant.”
- The total impurities from degradation are less than about 5% peak area response as measured by HPLC after at least 15 months of storage at 5° C to 25° C.
- The complaint alleges infringement of "one or more claims, including at least claim 1," reserving the right to assert other claims. (Compl. ¶73).
III. The Accused Instrumentality
- Product Identification: The accused product is VIVIMUSTA® (bendamustine hydrochloride injection) 100 mg/4 mL (25 mg/mL), an NDA product for which Defendant Azurity is the current holder. (Compl. ¶¶3, 6).
- Functionality and Market Context: VIVIMUSTA® is an alkylating drug indicated for the treatment of chronic lymphocytic leukemia and indolent B-cell non-Hodgkin lymphoma. (Compl. ¶¶29, 65). The complaint alleges, based on the product’s Approved Labeling, that each milliliter of VIVIMUSTA® contains 25 mg of bendamustine hydrochloride, 5 mg of monothioglycerol (an antioxidant), 39.45 mg of absolute alcohol (ethanol), and polyethylene glycol 400. (Compl. ¶50). It is marketed as a ready-to-use injection that is diluted for intravenous infusion. (Compl. ¶63). The complaint alleges VIVIMUSTA® relies on bioavailability and/or bioequivalence data from Plaintiff's own BELRAPZO® product. (Compl. ¶2).
IV. Analysis of Infringement Allegations
No probative visual evidence provided in complaint.
’783 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| providing a liquid bendamustine-containing composition comprising bendamustine... wherein the bendamustine concentration... is from about 20 mg/mL to about 60 mg/mL | The Approved Labeling for VIVIMUSTA® states the dosage strength is 25 mg/mL. | ¶48 | col. 3:20-25 |
| a pharmaceutically acceptable fluid consisting of polyethylene glycol and optionally one or more of propylene glycol, ethanol, benzyl alcohol and glycofurol | The VIVIMUSTA® Approved Labeling states it contains polyethylene glycol ("PEG") and "absolute alcohol" (ethanol). | ¶49 | col. 3:35-54 |
| and a stabilizing amount of an antioxidant | The VIVIMUSTA® Approved Labeling states it contains 5 mg of monothioglycerol, which the shared specification identifies as an antioxidant in a stabilizing amount. | ¶57 | col. 4:5-25 |
| wherein the total impurities... is less than about 5% peak area response... after at least about 15 months at a temperature of about 5 °C. to about 25 °C. | VIVIMUSTA® relies on stability data for Plaintiff's BELRAPZO® product and was approved by the FDA for a 24-month shelf life, allegedly satisfying the stability limitation. | ¶¶45-46 | col. 3:8-15 |
| diluting the liquid bendamustine containing composition; and intravenously administering the diluted composition to the human. | The VIVIMUSTA® Approved Labeling allegedly instructs healthcare professionals to dilute the product in an infusion bag and administer it intravenously to patients. | ¶63 | col. 2:15-17 |
’214 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| A sterile vial containing a liquid bendamustine-containing composition comprising about 100 mg of bendamustine... wherein the bendamustine concentration... is from about 25 mg/mL | VIVIMUSTA® is marketed in a 100 mg/4 mL vial, which contains 100 mg of bendamustine at a concentration of 25 mg/mL. | ¶74 | col. 3:20-25 |
| a pharmaceutically acceptable fluid consisting of polyethylene glycol and optionally one or more of propylene glycol, ethanol, benzyl alcohol and glycofurol | The VIVIMUSTA® Approved Labeling states it contains polyethylene glycol ("PEG") and "absolute alcohol" (ethanol). | ¶49 | col. 3:35-54 |
| and a stabilizing amount of antioxidant | The VIVIMUSTA® Approved Labeling states it contains 5 mg of monothioglycerol, which the shared specification identifies as an antioxidant. | ¶57 | col. 4:5-25 |
| wherein the total impurities... is less than about 5% peak area response... after at least about 15 months at a temperature of about 5 °C. to about 25 °C. | VIVIMUSTA® was approved for a 24-month shelf life, which the complaint alleges satisfies the stability limitation set forth in the claim. | ¶¶45-46 | col. 3:8-15 |
- Identified Points of Contention:
- Scope Questions: The complaint dedicates significant attention to the use of sodium hydroxide in the manufacturing of VIVIMUSTA®. (Compl. ¶¶50-56). This raises the question of whether the accused product's formulation falls outside the scope of the claim term "a pharmaceutically acceptable fluid consisting of polyethylene glycol and optionally..." The "consisting of" transition phrase is legally restrictive, typically meaning the element includes only the listed ingredients.
- Technical Questions: The central technical dispute foreshadowed by the complaint is the role and status of sodium hydroxide. The complaint alleges it is used only as a pH adjuster for the raw material PEG, is used only in a "quantity sufficient," is not used in every batch, and is "consumed by such use and/or is otherwise not a component of VIVIMUSTA®." (Compl. ¶¶53-55). This raises the factual question of whether sodium hydroxide or its reaction products are present in the final, marketed VIVIMUSTA® product and whether it constitutes an unlisted component of the claimed "fluid."
V. Key Claim Terms for Construction
- The Term: "a pharmaceutically acceptable fluid consisting of..."
- Context and Importance: This term appears in the independent claim of both asserted patents and its construction will be critical. The closed-ended "consisting of" language is highly restrictive. If a court determines that the VIVIMUSTA® fluid contains an additional, unlisted component, it may preclude a finding of literal infringement. Plaintiff's pre-emptive arguments regarding sodium hydroxide signal that the composition of this "fluid" is a primary point of anticipated dispute. (Compl. ¶¶50-56).
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification describes the fluid as being "suitable for pharmaceutical use" and lists several potential components. (’783 Patent, col. 2:52-55). A party might argue that common, unlisted processing aids used to prepare one of the listed components to pharmaceutical grade, and which are consumed or have no material effect on the final composition, do not violate the "consisting of" limitation.
- Evidence for a Narrower Interpretation: The claim explicitly uses "consisting of," followed by a specific list: "polyethylene glycol and optionally one or more of propylene glycol, ethanol, benzyl alcohol and glycofurol." (’783 Patent, Claim 1). This language itself is strong evidence for a narrow interpretation that excludes any other substance from being part of the "pharmaceutically acceptable fluid." The specification further provides specific examples of fluid mixtures, all of which are composed solely of the claimed components. (’783 Patent, col. 3:40-54).
VI. Other Allegations
- Indirect Infringement: The complaint alleges inducement of infringement based on Defendants' marketing of VIVIMUSTA® and its Approved Labeling, which allegedly instructs and encourages healthcare professionals to perform the claimed method steps of diluting and intravenously administering the product to treat leukemia. (Compl. ¶¶63, 66).
- Willful Infringement: Willfulness is alleged based on Defendants' purported knowledge of the patents-in-suit and their relevance to VIVIMUSTA®. The complaint alleges this knowledge arises from Plaintiff sending notice letters to Defendant Slayback on the issue dates of the respective patents, Defendants' alleged monitoring of Plaintiff's patent portfolio, and Slayback's involvement in prior litigation with Plaintiff over related patents. (Compl. ¶¶67-68, 76-77).
VII. Analyst’s Conclusion: Key Questions for the Case
This dispute appears to center on highly specific questions of chemical composition and claim construction, rather than the general function of the accused product. The key questions for the court will likely be:
- A core issue will be one of definitional scope: How will the court construe the restrictive claim term "a pharmaceutically acceptable fluid consisting of..."? Specifically, does the use of sodium hydroxide as a processing aid for one of the fluid's raw materials add an unlisted component to the final fluid, thereby taking the accused product outside the literal scope of the claims?
- A key evidentiary question will be one of chemical fact: What is the composition of the final, marketed VIVIMUSTA® product? Does it contain sodium hydroxide or its reaction products in any amount, or is the substance, as Plaintiff alleges, fully consumed during manufacturing and not a "component" of the final fluid?