United States Patent 5,547,948: A Detailed Analysis of Scope, Claims, and Patent Landscape
Introduction
United States Patent 5,547,948, titled "Controlled release of steroids from sugar coatings," is a significant patent in the pharmaceutical industry, particularly in the realm of drug delivery systems. This patent, granted to Duramed Pharmaceuticals (now part of Teva Women's Health), involves a sugar coating composition for medicinal tablets, ensuring controlled release of steroids. Here, we delve into the scope, claims, and the broader patent landscape surrounding this invention.
Background of the Patent
The patent was applied for on July 25, 1996, and it addresses a critical issue in pharmaceutical formulation: the controlled release of steroids from sugar-coated tablets. The invention is designed to improve the stability and efficacy of steroid-containing medications, which is crucial for treatments such as hormone replacement therapy[2][4].
Scope of the Patent
The scope of the patent is defined by its claims, which outline the specific aspects of the invention that are protected. Here are the key elements:
Independent Claim
The independent claim of the patent describes a pharmaceutical composition where a solid unit dosage form is coated with a moisture barrier coating. This coating is essential for preventing moisture from affecting the stability of the steroid within the tablet[2][4].
Dependent Claims
Dependent claims further specify the composition and characteristics of the moisture barrier coating. For example, dependent claim 7 specifically mentions that the moisture barrier coating comprises ethylcellulose. These claims narrow down the scope to ensure that the patent covers a specific and novel application of the coating[2][4].
Claims Analysis
Original Claims and Revisions
The original patent application included one independent claim and 27 dependent claims. However, during the prosecution process, the patent examiner rejected these claims as obvious in light of prior art, specifically U.S. Patent No. 5,547,948 ("Barcomb")[4].
To overcome these rejections, the patent examiner suggested amendments to the claims. These amendments included requiring the tablet to be substantially free of inorganic excipients, which can cause cracking of the coating, and incorporating specific limitations from other claims into the independent claim[4].
Prosecution History Estoppel
The amendments made to the claims are crucial in understanding the scope of the patent. The doctrine of prosecution history estoppel prevents the patent holder from asserting that any abandoned territory during the amendment process constitutes an "equivalent" to the patented invention. This means that Duramed cannot claim infringement based on equivalents that were not specifically included in the amended claims[4].
Patent Landscape
Prior Art and Novelty
The patent landscape surrounding U.S. Patent 5,547,948 is influenced by prior art, particularly the "Barcomb" patent. The "Barcomb" patent teaches the use of coatings on tablets, which was considered relevant prior art during the examination of Duramed's patent application. The amendments made to Duramed's claims were necessary to distinguish their invention from this prior art[4].
Industry Impact
This patent has significant implications for the pharmaceutical industry, especially in the development of hormone replacement therapies. The controlled release of steroids from sugar-coated tablets improves the efficacy and stability of these medications, which is a critical factor in patient treatment and compliance.
Litigation and Infringement
Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, Inc.
A notable case involving this patent is the litigation between Duramed Pharmaceuticals and Paddock Laboratories. Paddock sought to manufacture and market a generic version of Duramed's product, Cenestin, which is a conjugated estrogen tablet. Duramed alleged patent infringement, arguing that Paddock's use of a polyvinyl alcohol (PVA) moisture barrier coating was equivalent to the ethylcellulose coating protected by their patent. However, the court ruled that Paddock's coating did not literally infringe Duramed's patent, and Duramed's reliance on the doctrine of equivalents was limited by the prosecution history estoppel[2][4].
Metrics for Measuring Patent Scope
Research on patent scope, such as the work by Marco, Sarnoff, and deGrazia, highlights the importance of metrics like independent claim length and independent claim count in assessing the breadth and clarity of patents. These metrics can indicate the complexity and specificity of the claims, which in turn affect the patent's validity and the likelihood of litigation[5].
Conclusion on Patent Scope and Claims
The scope and claims of U.S. Patent 5,547,948 are carefully defined to ensure the protection of a novel and useful invention in the pharmaceutical field. The amendments made during the prosecution process and the limitations imposed by prosecution history estoppel are critical in understanding the boundaries of this patent.
"A patentee's decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim."[4]
Key Takeaways
- Specific Claims: The patent includes specific claims about the composition and characteristics of the moisture barrier coating.
- Prosecution History: Amendments made during the prosecution process are crucial in defining the scope of the patent.
- Prior Art: The patent distinguishes itself from prior art, such as the "Barcomb" patent.
- Industry Impact: The patent has significant implications for hormone replacement therapies.
- Litigation: The patent was involved in a notable litigation case involving generic drug manufacturing.
FAQs
What is the main invention described in U.S. Patent 5,547,948?
The main invention is a sugar coating composition for medicinal tablets that ensures the controlled release of steroids.
What is the significance of the moisture barrier coating in this patent?
The moisture barrier coating, specifically ethylcellulose, prevents moisture from affecting the stability of the steroid within the tablet.
How did the prosecution process affect the claims of this patent?
The claims were amended to include specific limitations, such as the tablet being substantially free of inorganic excipients, to overcome prior art rejections.
What is prosecution history estoppel, and how does it apply to this patent?
Prosecution history estoppel prevents the patent holder from asserting that any abandoned territory during the amendment process constitutes an "equivalent" to the patented invention.
What was the outcome of the litigation between Duramed Pharmaceuticals and Paddock Laboratories?
The court ruled that Paddock's coating did not literally infringe Duramed's patent, and Duramed's reliance on the doctrine of equivalents was limited by the prosecution history estoppel.
Sources
- Drug Patent Watch: Summary for Patent: 5,547,948.
- Vlex: Duramed Pharm.s Inc. v. Paddock Laboratories Inc. - Case Law.
- USPTO: Patent Claims Research Dataset.
- Casetext: Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, 715 F.
- SSRN: Patent Claims and Patent Scope by Marco, Sarnoff, and deGrazia.
