DCT
2:23-cv-00399
Par Pharmaceutical Inc v. Mankind Pharma Ltd
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Par Pharmaceutical, Inc. (New York) and Endo Par Innovation Company, LLC (Delaware)
- Defendant: Mankind Pharma Limited (India)
- Plaintiff’s Counsel: Dechert LLP
- Case Identification: 2:23-cv-00399, E.D. Tex., 09/01/2023
- Venue Allegations: Venue is alleged to be proper on the basis that the Defendant is a foreign corporation and may be sued in any judicial district in which it is subject to the court’s personal jurisdiction.
- Core Dispute: Plaintiff alleges that Defendant’s generic varenicline tartrate tablets are manufactured using a method that infringes a patent related to the purification of varenicline tartrate to remove carcinogenic impurities.
- Technical Context: Varenicline tartrate, the active ingredient in the smoking cessation drug CHANTIX®, was recalled by its original manufacturer due to unsafe levels of nitrosamine impurities, creating a market for a purified, FDA-compliant version.
- Key Procedural History: The complaint notes that the original brand-name product was withdrawn from the market in 2021 due to nitrosamine impurities. Plaintiff alleges it developed the patented technology to solve this problem and was the first to receive FDA approval for a low-nitrosamine generic. The patent-in-suit issued less than a month before the complaint was filed. The complaint states that Plaintiff sent pre-suit notice letters to Defendant and seeks to shift the burden of proof to Defendant under 35 U.S.C. § 295, arguing that Defendant's manufacturing process occurs in India and has not been disclosed.
Case Timeline
| Date | Event |
|---|---|
| 2021-07-XX | Pfizer withdraws CHANTIX® from the market |
| 2021-08-11 | FDA approves Plaintiff Par's ANDA for varenicline tablets |
| 2022-03-11 | '524 Patent earliest priority date |
| 2023-08-01 | FDA approves Defendant Mankind's ANDA for varenicline tablets |
| 2023-08-08 | U.S. Patent No. 11,717,524 issues |
| 2023-09-01 | Complaint filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 11,717,524 - "Varenicline Compound and Process of Manufacture Thereof"
The Invention Explained
- Problem Addressed: The patent addresses the unacceptable level of nitrosamine impurities found in the varenicline tartrate active pharmaceutical ingredient (API) used in the smoking cessation drug CHANTIX®, which led to the product's market withdrawal. ('524 Patent, col. 1:50-57; Compl. ¶17).
- The Patented Solution: The patent discloses a process for manufacturing substantially pure varenicline by removing nitrosamine impurities. The core of the patented solution is an "acid-base treatment" where the varenicline free base is converted into a salt using an acid. This process exploits a chemical difference: the varenicline forms a salt and dissolves in an aqueous layer, while the unprotonated nitrosamine impurities remain in a separate organic solvent layer, allowing them to be physically separated and removed. ('524 Patent, col. 21:20-30; Fig. 11).
- Technical Importance: This purification method provided a technical solution to the critical safety issue that forced a billion-dollar drug off the market, thereby enabling the production of varenicline tablets that meet FDA safety standards for nitrosamine levels. (Compl. ¶¶16, 31).
Key Claims at a Glance
- The complaint asserts infringement of at least independent claim 1. (Compl. ¶43).
- The essential elements of independent claim 1 are:
- A method of making a varenicline tartrate tablet comprising less than 50 ppm of nitrosamine impurities, the method comprising:
- (a) mixing varenicline free base with tartaric acid to form varenicline tartrate
- (b) means for reducing the nitrosamine impurities to less than 50 ppm per tablet as measured by LC-ESI-HRMS Method;
- wherein the means comprises an acid-base treatment.
- The complaint reserves the right to assert other claims. (Compl. ¶55).
III. The Accused Instrumentality
Product Identification
- Defendant Mankind’s generic varenicline tartrate tablets in 0.5 mg and 1 mg dosage strengths, sold for smoking cessation (the "Accused Tablets"). (Compl. ¶37).
Functionality and Market Context
- The Accused Tablets are a generic version of the smoking cessation drug formerly sold as CHANTIX®. The complaint alleges that for Mankind to have obtained FDA approval, its tablets must meet the FDA's acceptable daily intake limit for nitrosamine impurities, which is 18.5 parts per million (ppm). (Compl. ¶¶20, 39). The complaint includes a table of FDA laboratory analysis showing that Plaintiff Par's product had nitrosamine levels of 3 ppm, while Pfizer's recalled product and another generic had levels ranging from 27-474 ppm. This table is presented to support the assertion that achieving the required low impurity level is a significant technical challenge. (Compl. p. 10).
IV. Analysis of Infringement Allegations
The complaint alleges that Defendant infringes the ’524 Patent by making, using, selling, or importing the Accused Tablets, which are alleged to be made by the patented process. (Compl. ¶¶51-53). A central premise of the complaint is that Plaintiff is unaware of any other commercially viable method to produce varenicline tartrate tablets that meet the FDA's strict nitrosamine impurity limits. (Compl. ¶39).
U.S. Patent No. 11,717,524 Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| A method of making a varenicline tartrate tablet comprising less than 50 ppm of nitrosamine impurities... | The complaint alleges that to receive FDA approval, Mankind's Accused Tablets must have nitrosamine impurity levels below the FDA's limit of 18.5 ppm, which is less than the claimed 50 ppm. | ¶39, ¶55B | col. 2:1-5 |
| (a) mixing varenicline free base with tartaric acid to form varenicline tartrate | The complaint alleges the API in the Accused Tablets is varenicline tartrate, as confirmed by the FDA's website, and infers this step is used in its manufacture. | ¶39, ¶55A | col. 13:1-4 |
| (b) means for reducing the nitrosamine impurities to less than 50 ppm per tablet as measured by LC-ESI-HRMS Method; | Plaintiff alleges it is "highly likely" that Mankind uses the patented methods because it is unaware of any other commercially viable methods to achieve the required low impurity levels. Mankind's process is not publicly known. | ¶39, ¶56 | col. 70:5-9 |
| wherein the means comprises an acid-base treatment. | This allegation is based on the same inference that Mankind must be using the patented method, which discloses an "acid-base treatment" as the structure corresponding to the "means for reducing" function. | ¶39, ¶56 | col. 70:10-12 |
- Identified Points of Contention:
- Evidentiary Questions: The primary point of contention is factual: what manufacturing process does Mankind actually use? The complaint relies on inference, alleging that since the Accused Tablets meet FDA impurity standards, they must be made using the patented process. This raises the question of whether Plaintiff's allegations are sufficient without direct evidence and whether its attempt to invoke 35 U.S.C. § 295 to shift the burden of proof will succeed.
- Technical Questions: A core technical question is whether alternative, non-infringing, and commercially viable methods exist for reducing nitrosamine impurities in varenicline tartrate to FDA-mandated levels. The viability of Mankind's defense may depend on its ability to present such an alternative process.
V. Key Claim Terms for Construction
- The Term: "means for reducing the nitrosamine impurities..."
- Context and Importance: This term, recited in claim 1(b), is a means-plus-function limitation governed by 35 U.S.C. § 112(f). Its scope is not its literal language but is instead defined by the corresponding structure described in the patent's specification and equivalents thereof. The infringement analysis for this element will depend entirely on whether Mankind’s undisclosed purification process uses a structure that is the same as or equivalent to what is disclosed in the ’524 Patent. Practitioners may focus on this term because the structure it covers—the "acid-base treatment"—is the technological core of the invention.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification discloses that the "acid-base treatment" can be performed with a wide variety of organic and inorganic acids, including "tartaric acid, fumaric acid, lactic acid, malic acid, malonic acid, hydrochloric acid, succinic acid, oxalic acid, citric acid, and mixtures thereof." (’524 Patent, col. 13:39-43). This could support a construction where the "acid-base treatment" is not limited to a single embodiment but covers a general class of purification processes using acid-base chemistry.
- Evidence for a Narrower Interpretation: A party seeking a narrower scope may argue that the "corresponding structure" is limited to the specific embodiments and process flow diagrams detailed in the patent. For example, one could argue the structure requires the specific sequence of steps shown in Figure 11, including the use of methylene dichloride as the organic solvent and sodium carbonate for basification. (’524 Patent, Fig. 11; col. 15:60-67).
VI. Other Allegations
- Indirect Infringement: The complaint alleges that to the extent Mankind does not directly infringe, it knowingly induces infringement by others with full knowledge of the ’524 patent. (Compl. ¶58).
- Willful Infringement: The willfulness allegation is based on alleged pre-suit knowledge. Plaintiff alleges it sent Mankind a "First Notice Letter" on August 4, 2023, and a "Second Notice Letter" on August 11, 2023, advising Mankind of the patent and the infringement allegations. The complaint alleges that despite this notice, Mankind has begun to offer the Accused Tablets for sale. (Compl. ¶¶38, 42, 47, 57, 60).
VII. Analyst’s Conclusion: Key Questions for the Case
- A primary issue will be one of evidentiary access and burden of proof: Given that the accused method occurs in a confidential process in India, the case will likely feature an early and critical dispute over whether Plaintiff’s inferential allegations are sufficient to proceed and whether the court will apply 35 U.S.C. § 295 to shift the burden to Defendant to prove its process is non-infringing.
- A second key question will be one of technical alternatives: Assuming discovery proceeds, the case will turn on whether Mankind’s purification process is distinct from the patented "acid-base treatment." The existence of a commercially viable, alternative, and non-infringing method for removing nitrosamine impurities would fundamentally undermine Plaintiff's core theory of infringement.
- A final question will be one of claim scope: The construction of the means-plus-function term "means for reducing the nitrosamine impurities" will be dispositive. The central legal battle will be to define the scope of the corresponding "acid-base treatment" structure disclosed in the patent, which will determine whether Mankind’s process falls inside or outside the patent's boundaries.