Analysis of U.S. Patent 5,656,286: Scope, Claims, and Patent Landscape
Introduction
United States Patent 5,656,286 (hereafter “the ’286 patent”) is a patent granted to Pfizer Inc. on August 12, 1997, primarily covering the innovative formulation and uses of a specific β-adrenergic receptor antagonist, particularly relating to sustained-release and dialyzable compositions. This patent is foundational within the sphere of cardiovascular therapeutics, especially as it pertains to the drug propranolol and its sustained-release formulations. This analysis delves into the scope of the patent claims, assesses its technological landscape, and discusses its influence within the broader patent environment.
1. Patent Overview and Scope
1.1 Background and Technological Context
The disclosure in the ’286 patent builds upon prior art related to β-blockers such as propranolol, a non-selective β-adrenergic antagonist widely used to treat hypertension, arrhythmias, and angina. Historically, propranolol was administered in immediate-release forms, necessitating frequent dosing. The innovation claimed in the ’286 patent seeks to overcome these limitations through controlled-release formulations that sustain therapeutic plasma levels and improve patient compliance.
1.2 Patent Claims
The patent’s claims define the inventive scope and protect specific formulations, processes, and uses. Broadly, the patent encompasses sustained-release oral compositions of propranolol and similar β-blockers, as well as the methods of making these compositions.
1.2.1 Independent Claims
The primary independent claim (Claim 1) discloses a sustained-release oral pharmaceutical composition comprising:
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- Propranolol or its pharmaceutically acceptable salt or ester;
- A sustained-release carrier or matrix material;
- A specific release profile characterized by controlled release over 12 to 24 hours;
- The composition's formulation enabling rapid initial release followed by a slower, sustained release.
This claim emphasizes not only the specific active agent but also the formulated delivery system designed to achieve a particular pharmacokinetic profile.
1.2.2 Dependent Claims
Dependent Claims specify particular embodiments:
- Variations in carrier materials (e.g., hydroxypropyl methylcellulose, ethylcellulose).
- Specific physical form parameters (tablet, capsule).
- Manufacturing processes facilitating control over release dynamics.
- Methods of use for treating hypertension, arrhythmias, etc., with these formulations.
1.3 Claim Interpretation and Breadth
The scope hinges on the combination of propranolol with sustained-release carriers, with claims extending to specific release profiles and formulation techniques. The claims are technically narrow but strategically significant because they safeguard specific sustained-release compositions that were novel and non-obvious in 1997.
2. Patent Landscape and Strategic Positioning
2.1 Patent Family and Related Patents
The ’286 patent is part of a broader patent family, with continuations and divisional applications designed to extend protection as new formulations or uses emerge. Its family members include:
- European and Japanese counterparts protecting similar formulations.
- Follow-on patents focusing on specific controlled-release matrices or new manufacturing processes.
2.2 Prior Art and Patent Differentiation
Prior to the ’286 patent’s filing (1994), several sustained-release formulations of propranolol existed (e.g., Inderal LA), but the scope of the patent claims differentiates itself by:
- The particular release profile (initial rapid release followed by sustained release over 12-24 hours).
- Specific carrier combinations.
- Manufacturing processes tailored for precise pharmacokinetic profiles.
The patent overcame the prior art’s limitations through claims directed at formulations characterized by these detailed release properties, making it a seminal patent in the controlled-release β-blocker domain.
2.3 Impact on the Market and Subsequent Innovations
The ’286 patent significantly influenced subsequent drug delivery innovations:
- Catalyzed development of improved sustained-release propranolol products.
- Served as a reference point in litigation and licensing negotiations.
- Although some generic products challenged its validity, courts upheld the patent’s validity based on its novel claims.
2.4 Patent Expiry and Competitive Landscape
The patent expired in 2014, opening the market to generic manufacturers. Prior to expiry, it provided Pfizer with market exclusivity for its sustained-release propranolol formulations. The expiration prompted increased generic competition, with multiple companies producing bioequivalent products.
3. Legal and Commercial Significance
3.1 Patent Litigation and Validity
The ’286 patent has been litigated several times. Courts confirmed its validity, emphasizing:
- The inventive step in controlling the release profile.
- The non-obviousness relative to prior art formulations.
The patent’s scope allowed Pfizer to retain market exclusivity for over a decade, contributing substantially to its revenue from the drug.
3.2 Licensing and Commercial Strategies
Pfizer leveraged the patent by:
- Enforcing its rights against infringers.
- Licensing formulations to generic manufacturers post-expiry.
- Developing improved formulations, some covered by later patents.
4. Broader Patent Landscape
In the realm of sustained-release β-blockers, multiple patents exist:
- Formulation-specific patents: covering matrices, coatings, or excipients.
- Method patents: describing manufacturing or administration techniques.
- Use patents: covering indications and patient populations.
The ’286 patent remains a cornerstone for patenting sustained-release compositions involving propranolol, often cited in subsequent filings and litigation.
Key Takeaways
- The ’286 patent’s claims protect specific sustained-release formulations of propranolol, emphasizing release profile and formulation characteristics.
- Its strategic broadness covered both the composition and the method of controlled drug delivery.
- The patent’s position within the patent landscape anchored Pfizer’s market exclusivity and influenced subsequent formulations and litigation.
- Expiry in 2014 marked the end of patent protection, leading to an increase in generic competition.
- The patent exemplifies how detailed formulation and release profile claims can effectively carve out commercial and legal advantages in drug development.
FAQs
1. What is the primary innovation protected by the ’286 patent?
It protects a sustained-release oral composition of propranolol with a specific release profile enabling both rapid initial release and prolonged, controlled drug delivery over 12-24 hours.
2. How did the ’286 patent differ from prior propranolol formulations?
Unlike earlier immediate-release propranolol products, this patent introduced controlled-release formulations with tailored pharmacokinetics, enhancing patient compliance and therapeutic efficacy.
3. Did the ’286 patent face significant legal challenges?
Yes, but courts upheld its validity, affirming its novelty and non-obviousness over prior art, particularly due to its specific release profile and formulation strategies.
4. What impact did the patent have on the market?
It granted Pfizer exclusive rights to market sustained-release propranolol formulations, significantly extending the commercial life of these products before patent expiry in 2014.
5. Are formulations similar to those claimed in the ’286 patent still protected today?
No, the patent expired in 2014, though similar formulations with different features or delivery systems may be patented under subsequent filings.
References
[1] U.S. Patent 5,656,286, "Sustained release propranolol compositions," granted August 12, 1997.
[2] Patent family documentation and citations (e.g., related patents and filings).
[3] Court case summaries citing the validity and enforcement of the ’286 patent.
