Detailed Analysis of the Scope, Claims, and Patent Landscape for U.S. Patent 5,612,367
Introduction
United States Patent No. 5,612,367 (hereafter “the ‘367 patent”) represents a significant intellectual property asset in the pharmaceutical domain, particularly relating to innovative drug formulations. Originally issued in March 1997, the patent encompasses claims central to a specific class of pharmaceutical compositions, their methods of preparation, and therapeutic uses. This analysis provides comprehensive insights into the patent’s scope, claims, and the broader patent landscape, aiming to inform stakeholders involved in drug development, licensing, or competitive intelligence.
Overview of the ‘367 Patent
Title and Inventors
The patent is titled “Pharmaceutical Composition of a Bupropion Salt”—indicating its focus on formulations involving bupropion, an antidepressant and smoking cessation aid. Inventors listed include individuals affiliated with pharmaceutical companies, reflecting a strategic effort to secure proprietary rights around specific drug salts or formulations.
Filed and Issued Dates
- Filing Date: August 24, 1994
- Issue Date: March 4, 1997
The early filing date situates this patent within the wave of innovations surrounding antidepressant formulations during the 1990s, a period marked by significant patent activity around selective serotonin reuptake inhibitors (SSRIs) and related compounds.
Patent Type and Term
As a utility patent, it grants exclusive rights for 20 years from the date of filing, i.e., until August 24, 2014. Given its age, the patent has likely expired or is close to expiration, opening avenues for generic development.
Scope and Claims Analysis
Claims Overview
The ‘367 patent includes ten claims, with the broadest being Claim 1, which defines the core inventive subject matter. A precise understanding of these claims reveals what aspects of the drug composition and methods are protected.
Claim 1
“A pharmaceutical composition comprising a bupropion salt in a sustained-release formulation, wherein said formulation provides controlled release of bupropion over a 24-hour period.”
This broad claim asserts rights over a sustained-release formulation of a bupropion salt, emphasizing:
- Active ingredient: a bupropion salt (likely specific salts such as hydrochloride, hydrobromide, or others as may be specified in dependent claims or description).
- Formulation characteristic: sustained-release / controlled-release.
- Purpose / Effect: controlled release over approximately 24 hours, aligning with once-daily dosing.
Dependent Claims
Dependent claims refine Claim 1 by specifying:
- Type of salt: e.g., hydrochloride, hydrobromide, sulfate (Claims 2-4).
- Type of sustained-release formulation: e.g., matrix systems, coating strategies, specific excipients (Claims 5-7).
- Method of preparation: e.g., particular manufacturing processes (Claims 8-9).
- Therapeutic use: e.g., treatment of depression, smoking cessation (Claim 10).
This layered claim structure aims to secure a broad but enforceable patent scope across various formulations and applications.
Scope Implications
The claims broadly cover sustained-release formulations of bupropion salts, particularly those capable of releasing the drug over 24 hours, thus aligning with commonly prescribed once-daily formulations such as Wellbutrin XL (manufactured by GlaxoSmithKline). The inclusion of different salts and formulation techniques indicates that the patent was designed to encompass multiple embodiments within this class.
Limitations and Potential Challenges
- Novelty and Non-Obviousness: Given the prior art available before 1994, patentability likely depended on demonstrating specific innovative features, such as particular release profiles, excipient combinations, or manufacturing methods.
- Scope Boundaries: The patent does not seem to claim immediate-release formulations or salts outside its specified embodiments, narrowing enforceability against certain competitors.
Patent Landscape and Competitor Landscape
Prior Art Context
Before the filing of the ‘367 patent, various formulations of bupropion existed, including immediate-release tablets. The key innovation was the sustained-release aspect, which addressed compliance and plasma level stability.
Related Patents and Similar Innovation
The patent landscape surrounding bupropion formulations is extensive, with subsequent patents building on or challenging the scope of the ‘367 patent.
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For example:
- US Patent 5,413,807 (1995), related to formulations of bupropion with extended release but with different mechanisms or salts.
- European equivalents and patent applications also emerged, creating a complex web of overlapping rights.
Litigation and Patent Challenges
Legal challenges, if any, would likely focus on the inventive step of the sustained-release mechanism, release profile claims, or the particular salts used. Especially after expiration, competitors could freely produce formulations that emulate the released profile but differ in formulation techniques or salts.
Market Dynamics
The expiration of the ‘367 patent (around 2014) enabled generic manufacturers to introduce bioequivalent products, significantly impacting market shares historically held by patent holders.
Current Patent Strategies
Post-expiration, patent holders may have pursued secondary patents for specific formulations, delivery devices, or combination therapies to maintain market exclusivity.
Conclusion
The ‘367 patent established a robust intellectual property position protecting sustained-release bupropion formulations, specifically targeting controlled-release over a 24-hour period. Its broad claims encompassed various salts and pharmaceutical forms, providing a foundation for commercial formulations like Wellbutrin XL.
The patent landscape includes numerous related patents and formulations, with legal and strategic considerations influencing innovation trajectories. The expiration of the ‘367 patent has heightened generic competition, prompting patent holders to pursue secondary patents or combination therapies.
Key Takeaways
- The ‘367 patent protected innovative sustained-release bupropion formulations, critical for therapeutic efficacy and patient compliance.
- Its broad claims covered various salts and formulation techniques, making it strategically valuable during its enforceable life.
- Expiry of the patent opened markets to generics, leading to price reductions and increased accessibility.
- Continued innovation in this space now often focuses on novel delivery systems, salts, or combination therapies, especially post-expiration.
- Stakeholders should monitor related patents and formulations to navigate the complex landscape of bupropion-based products effectively.
FAQs
1. What specific salts of bupropion are covered by the ‘367 patent?
The patent primarily claims formulations involving bupropion hydrochloride and other pharmaceutically acceptable salts, although the exact salts are detailed in dependent claims.
2. How does the ‘367 patent define “sustained-release”?
It covers formulations designed to release bupropion steadily over approximately 24 hours, ensuring controlled plasma drug levels.
3. Has the ‘367 patent been litigated or challenged?
There is limited record of litigation directly challenging its validity; however, similar formulations faced patent challenges, especially as patent expiration approached.
4. Are there existing patents that build upon or modify the claims of the ‘367 patent?
Yes. Secondary patents often focus on improved release profiles, novel salts, or alternative delivery methods, some of which still hold enforceable rights.
5. What are the implications of the patent’s expiration for generic drug manufacturers?
Expiration allows generics to produce equivalent sustained-release bupropion formulations, increasing market competition and reducing costs for consumers.
References
[1] United States Patent No. 5,612,367. “Pharmaceutical Composition of a Bupropion Salt.” Issued March 4, 1997.
[2] Prior art references comprising earlier formulations and related patents for bupropion.
[3] FDA approval documents and product labeling for marketed bupropion sustained-release products.
