Detailed Analysis of the Scope, Claims, and Patent Landscape for U.S. Patent 4,923,892
Introduction
U.S. Patent No. 4,923,892, granted on May 8, 1990, represents a significant patent in the pharmaceutical sector, particularly within the domain of controlled-release drug formulations. Its scope encompasses novel invention claims directed at specific pharmaceutical compositions, methods of manufacturing, and therapeutic applications which have influenced subsequent patent filings and research within the drug delivery landscape. This analysis systematically dissects the patent's claims, scope, and its position within the broader patent landscape.
Background and Patent Overview
The patent, assigned to SmithKline Beecham (now GlaxoSmithKline), primarily covers a sustained-release oral pharmaceutical composition. The invention aims to improve pharmacokinetic profiles, patient adherence, and dosing convenience for drugs requiring controlled release over extended periods.
The patent's key technical thrust includes a specific matrix formulation that modulates drug release rates, composed of a combination of hydrophilic polymers, plasticizers, and active pharmaceutical ingredients (APIs). This formulation is distinguished by its ability to maintain therapeutic plasma levels over prolonged periods with minimal fluctuation.
Claims Analysis
U.S. Patent 4,923,892 contains a layered set of claims subdivided into independent and dependent claims, with the primary focus on the composition and method of manufacture of the controlled release formulation.
Independent Claims
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Claim 1: Defines an oral sustained-release pharmaceutical composition comprising an active pharmaceutical ingredient dispersed within a matrix formed from specific hydrophilic polymers, such as hydroxypropyl methylcellulose (HPMC), in a specified weight ratio, which provides sustained drug release over a defined period.
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Claim 2: Details the process for manufacturing the composition, emphasizing the blending, granulation, and tablet compression steps, emphasizing specific process parameters to ensure uniform dispersion of the API within the matrix.
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Claim 8: Extends the composition to include a plasticizer, emphasizing its role in modulating the matrix's mechanical properties and drug release kinetics.
Dependent Claims
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Incorporate specifications such as the inclusion of particular polymers, ranges of polymer-to-API ratios, specific plasticizers (e.g., glycerol or propylene glycol), and dissolution profiles under standardized conditions (e.g., USP testing methods).
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Additional dependent claims specify variations such as multilayer formulations, alternative tablet shapes, or coating techniques to modify release profiles.
Scope of the Claims
The scope of the patent is primarily centered on:
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The composition: A hydrophilic polymer-based matrix containing specific ratios of API, designed for controlled release.
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The manufacturing process: Detailed methods ensuring reproducibility and the integrity of the controlled-release matrix.
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The application and variations: Flexibility to incorporate different APIs or polymer combinations, provided they meet the specified criteria.
The claims are relatively narrow within the realm of sustained-release formulations, differentiating from earlier patents by the specific polymer ratios, manufacturing methods, and the inclusion of particular excipients that optimize the release profile.
Patent Landscape Context
Prior Art and Influence
At the time of filing, the patent addressed the limitations observed in earlier controlled-release formulations, such as inconsistent release and manufacturing difficulties. Key prior art included:
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U.S. Patent No. 4,340,583: Focused on hydrophilic matrices utilizing HPMC for controlled release but lacked detailed process parameters.
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U.S. Patent No. 4,683,262: Covered delayed-release matrices, differing in release mechanisms.
The '892 patent distinguished itself by its specific formulation ratios and manufacturing steps, leading to its allowance and subsequent influence.
Subsequent Patents and Citation Trends
Post-1990, numerous patents cite this document, reflecting its foundational role:
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Extended-release formulations: Many follow-up patents build upon its polymer matrix concept, refining drug release profiles.
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Process improvements: Several patents introduce novel manufacturing techniques (e.g., hot-melt extrusion, coating strategies) that cite the '892 patent as prior art.
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Polymer innovations: Recent patents explore alternative hydrophilic polymers or combination matrices inspired by the formulations described herein.
The patent remains a critical reference point in the controlled-release drug patent landscape, influencing both academic research and industrial formulations.
Legal Status and Patent Expiry
The patent, filed in 1988, expired in 2008, opening the field for generic manufacturers and further innovation. Its expiration has gained significance in the context of patent lapses allowing broader accessibility to the formulations or similar compositions.
Implications for Stakeholders
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Pharmaceutical developers: The claims delineate a clear breadth of innovation, informing design-around strategies and regulatory considerations.
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Patent counsel: The scope cautions against infringing on key polymer ratios or manufacturing processes within similar formulations.
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Researchers: The patent's detailed composition and process claims serve as a technical baseline for developing next-generation controlled-release systems.
Conclusion
U.S. Patent 4,923,892 offers a precise and narrowly defined scope of claims centered on hydrophilic matrix formulations for controlled drug release, which significantly impacted subsequent patent filings and drug development efforts. Its robust claims on composition and process have set standard benchmarks within the sustained-release drug formulation domain, though its expiration facilitates broader generic and innovative pursuits.
Key Takeaways
- The patent's claims focus on specific polymer ratios for sustained-release oral formulations, serving as a fundamental reference point.
- Its detailed process claims promote manufacturing reproducibility and product consistency.
- The patent landscape reveals broad adoption and citation, underscoring its influence on subsequent innovations.
- Patent expiration opens opportunities for generic development and further technical advancements in controlled-release pharma.
- Stakeholders should consider both its technical scope and legal status when designing or entering the field.
FAQs
1. What is the primary technological advancement claimed in U.S. Patent 4,923,892?
It claims a specific hydrophilic polymer matrix composition and manufacturing process enabling controlled release of an active pharmaceutical ingredient over an extended period.
2. How does this patent influence current controlled-release drug formulations?
It provides foundational formulations and process parameters, serving as a reference for designing modern sustained-release systems and guiding patent strategies.
3. Are the specific polymer ratios claimed in the patent still considered innovative after expiry?
Post-expiry, such specific formulations are considered prior art, allowing third-party manufacturers to produce similar compositions without infringing the patent.
4. Can the methods described in the patent be applied to any drug?
The claims specify particular polymers and ratios; adapting to other drugs requires additional validation but the core formulation principles offer a useful template.
5. Are there any known litigation or patent disputes related to this patent?
No significant litigation records are publicly associated with this patent, but its expired status reduces the likelihood of enforcement issues.
References
[1] U.S. Patent No. 4,923,892.
[2] Prior art references including No. 4,340,583 and 4,683,262.
