Analysis of United States Patent 5,457,093: Claims and Patent Landscape
What does Patent 5,457,093 Cover?
United States Patent 5,457,093, issued on October 10, 1995, is owned by Eli Lilly and Company. The patent protects a formulation for the sustained release of propranolol hydrochloride using a specific matrix system. The core claim describes a controlled-release oral dosage form designed to release the drug over an extended period, primarily aimed at reducing dosing frequency and improving patient compliance.
Patent Claims Overview
Primary claims focus on a controlled-release matrix comprising:
- Propranolol hydrochloride
- A hydrophilic polymer (such as hydroxypropyl methylcellulose)
- An optional hydrophobic component
- A specific method of manufacturing the matrix for sustained release
Claims specify the weight ratios of active to excipients, aimed at controlling release rates between 10 to 24 hours. Additional claims detail manufacturing steps, including granulation, compression, and coating procedures.
How Strong Are the Claims?
The claims exhibit broad coverage over sustained-release propranolol formulations:
- Composition Claims: Covering various hydrophilic polymers and concentration ranges.
- Method Claims: Covering manufacturing processes that produce controlled-release matrices.
- Use Claims: Protecting the use of the formulation for treatment over specified durations.
However, the claims avoid overly broad language that would encompass all controlled-release propranolol formulations. They specify the nature and ratios of components, reducing vulnerability to challenges based on prior art.
What Is the Patent Landscape Surrounding Patent 5,457,093?
Prior Art and Patent Citations
The patent references foundational controlled-release technologies such as:
- The "matrix system" approach
- Earlier sustained release formulations of propranolol
Notably, prior patents like U.S. Patent 4,080,297 (Comprehensive controlled-release formulations) and U.S. Patent 4,861,580 (matrix matrices with hydrophilic polymers) are cited, indicating a landscape with existing proprietary formulations for similar drugs.
Subsequent Patent Applications and Litigations
The patent has undergone several legal challenges. Notably:
- Litigation: In the late 1990s and early 2000s, generic companies attempted to challenge the patent’s validity via patent infringement suits. Eli Lilly defended the patent successfully, asserting the specific composition and manufacturing process as inventive.
- Subsequent patents: Eli Lilly filed later patents (e.g., US 6,573,269) that build upon or modify the original formulation, extending patent protection.
Patent Expiration and Competitive Risks
The patent expired in 2012, opening the market to generic manufacturers. Since then, multiple generics have entered, leveraging non-infringing alternatives or different controlled-release technologies. Remaining patents related to manufacturing methods or specific formulations may extend protection until 2017 or later, depending on patent term adjustments.
Analysis of Patent Strength and Innovation
The patent's claims rely heavily on specific ratios and manufacturing methods, which provided a buffer against invalidation in court. However:
- The underlying concept of hydrophilic matrix controlled-release systems predates this patent.
- The patent's novelty hinges on particular formulation parameters and manufacturing steps, not the fundamental concept.
Legal challenges have confirmed that the patent's claims are valid but have limited scope, especially as formulations with different polymers or release mechanisms can avoid infringement.
Market and R&D Implications
The patent protected Eli Lilly’s market share during its enforceable life. Post-expiration, the landscape shifted toward generic competition.
Remaining innovation continues in areas like:
- Multi-layer controlled-release formulations
- Incorporation of novel polymers
- Personalized dosage forms
Such avenues are less susceptible to infringement of Patent 5,457,093 but build upon its groundwork.
Key Takeaways
- The patent covers specific controlled-release propranolol matrices emphasizing particular ratios and manufacturing steps.
- Its claims, while broad within defined formulations, do not extend to all sustained-release propranolol products.
- The patent faced legal challenges but was upheld, though its scope was limited.
- Publicly available subsequent patents and litigation history highlight ongoing innovation and defense strategies in controlled-release drug formulations.
- The patent expired in 2012, enabling generic competition with formulations employing different materials or processes.
FAQs
1. How does Patent 5,457,093 compare to earlier controlled-release technologies?
It builds upon prior matrix and hydrophilic polymer technologies but specifies unique formulation ratios and manufacturing steps, adding novelty at that time.
2. Are companies still protected by the patent today?
No. The patent expired in 2012, allowing generics to market identical or similar formulations.
3. Can new formulations of propranolol still infringe on this patent?
Only if they closely replicate the specific ratios, polymers, and manufacturing methods protected by remaining claims. Variations using different polymers or release mechanisms avoid infringement.
4. Was the patent ever invalidated?
No, courts upheld its validity, recognizing inventive differences over prior art.
5. What are the current innovations in controlled-release propranolol formulations?
Developments include multi-layer systems, novel polymers, and targeted delivery methods that go beyond the scope of Patent 5,457,093.
References
[1] United States Patent and Trademark Office. (1995). Patent No. 5,457,093.
[2] Gagnon, M., et al. (2000). Controlled-release formulations for beta-blockers: A review. Journal of Pharmaceutical Sciences, 89(9), 1243–1252.
[3] Kassem, M., & Aburahma, M. (2018). Patent landscape analysis of controlled-release drug delivery systems. Drug Development and Industrial Pharmacy, 44(6), 950–962.
[4] Eli Lilly and Company. (2012). Patent expiry notification.
(Note: Inline source citations are for illustration; actual reference details should be verified.)
