United States Patent 5,508,276: A Detailed Analysis of Scope, Claims, and Patent Landscape
Introduction
United States Patent 5,508,276, titled "Duloxetine enteric pellets," is a significant patent in the pharmaceutical field, particularly concerning the formulation and delivery of the antidepressant drug duloxetine. This patent, now expired, was crucial for the development and marketing of Cymbalta, a drug owned by Eli Lilly and Co.
Background of the Invention
The patent, filed by Eli Lilly and Co., addresses the need for a superior enteric formulation of duloxetine. Enteric coatings are designed to protect the drug from the acidic environment of the stomach, ensuring it is released in the intestines where it can be more effectively absorbed[1][4].
Scope of the Patent
Field of the Invention
The patent pertains to the field of pharmaceutical science, focusing on the formulation of duloxetine in the form of enteric pellets. This formulation is designed to enhance the stability and bioavailability of the drug[1].
Key Components
- Enteric Coating: The patent describes the use of hydroxypropylmethylcellulose acetate succinate (HPMCAS) as the enteric coating material. This coating protects the drug from gastric acid and ensures its release in the intestinal environment[1][4].
- Pellet Formulation: The duloxetine is formulated into pellets, which can be filled into capsules or compressed into tablets. This form allows for controlled release and improved patient compliance[1].
Claims of the Patent
The patent includes several claims that define the scope of the invention:
Independent Claims
- The patent claims a pharmaceutical composition comprising duloxetine or its pharmaceutically acceptable salts in the form of enteric pellets.
- It specifies the use of HPMCAS as the enteric coating material.
- The claims also cover the process of preparing these enteric pellets, including the steps of granulation, pelletization, and coating[1].
Dependent Claims
- These claims further detail the composition, including the presence of other excipients such as bulking agents, lubricants, and coloring agents.
- They also specify the methods of manufacturing, including extrusion, compression, and sugar coating processes[1].
Patent Landscape
Expiration and Generic Launch
The patent for duloxetine enteric pellets expired in July 2014. This expiration, along with the expiration of other related patents, paved the way for the launch of generic versions of Cymbalta. The generic launch date was estimated to be around April 20, 2023, considering all exclusivities and patent expirations[2].
Related Patents
- Treatment of Fibromyalgia: Other patents, such as US6596756, cover the use of duloxetine for treating fibromyalgia. These patents have also expired, contributing to the broader generic landscape[2][4].
- Taste Masked Compositions: Patents like the one filed by Wockhardt Ltd. (US8758779) describe taste-masked pharmaceutical compositions of duloxetine, which are another aspect of the drug's formulation[4].
Legal Activities and Exclusivities
The patent landscape of Cymbalta includes various legal activities and exclusivities that have impacted its generic launch. For instance, pediatric exclusivity and new indication exclusivities have played a role in delaying the generic launch. However, all these exclusivities have now expired[2].
Impact on the Pharmaceutical Industry
Innovation and Competition
The expiration of this patent and related ones has opened up the market for generic competition. This competition can drive down prices and increase access to the medication, which is beneficial for patients. However, it also reduces the incentives for innovation by the original patent holder, as the revenue from the patented drug decreases[3].
Generic Entry Strategies
Generic manufacturers can seek FDA approval before the patent expiration by filing a Paragraph IV certification, which challenges the validity or enforceability of the patent. This strategy was employed for Cymbalta, with several ANDA (Abbreviated New Drug Application) filings and subsequent approvals[2].
Key Takeaways
- Patent Scope: The patent covers the formulation of duloxetine in enteric pellets using HPMCAS.
- Expiration: The patent expired in July 2014, allowing for generic competition.
- Related Patents: Other patents cover different aspects of duloxetine, such as treatment indications and taste-masked compositions.
- Legal Activities: Various legal activities and exclusivities have influenced the generic launch timeline.
- Industry Impact: The expiration has increased competition and access to the medication but may reduce innovation incentives.
FAQs
What is the main focus of United States Patent 5,508,276?
The main focus of this patent is the formulation of duloxetine in the form of enteric pellets to enhance its stability and bioavailability.
What is the significance of the enteric coating in this patent?
The enteric coating, made from HPMCAS, protects the drug from gastric acid and ensures its release in the intestinal environment, where it can be more effectively absorbed.
When did the patent for duloxetine enteric pellets expire?
The patent expired in July 2014.
How has the expiration of this patent affected the pharmaceutical market?
The expiration has allowed for the launch of generic versions of Cymbalta, increasing competition and reducing prices, but it may also reduce the incentives for innovation by the original patent holder.
What are the implications of Paragraph IV certifications for generic manufacturers?
Generic manufacturers can use Paragraph IV certifications to challenge the validity or enforceability of the patent, allowing them to seek FDA approval before the patent expiration.
How do exclusivities impact the generic launch of a drug?
Exclusivities, such as pediatric exclusivity and new indication exclusivities, can delay the generic launch by extending the period during which the original patent holder has exclusive rights to the market.
Sources
- US5508276A - Duloxetine enteric pellets - Google Patents
- Cymbalta patent expiration - Pharsight
- Patent Claims and Patent Scope - Hoover Institution
- Pharmaceutical composition of duloxetine - Justia Patents
