United States Drug Patent 6,303,146: Scope, Claims, and Landscape Analysis
Patent 6,303,146, titled "Processes for preparing N-(4-substituted phenyl)-N'-(2,3-dihydro-1,4-benzodioxin-5-yl)urea compounds," was granted to Warner-Lambert Company LLC on October 16, 2001. The patent covers specific synthetic processes for producing a class of urea compounds, primarily targeting the therapeutic agent known as Pioglitazone. Pioglitazone is an antidiabetic medication used to improve glycemic control in adults with type 2 diabetes mellitus.
What is the Primary Subject of Patent 6,303,146?
The patent's core subject is the synthesis of N-(4-substituted phenyl)-N'-(2,3-dihydro-1,4-benzodioxin-5-yl)urea compounds. This generic chemical structure is exemplified by Pioglitazone, which is 5-[[4-[2-(5-ethylpyridin-2-yl)ethoxy]phenyl]methyl]-1,3-thiazolidine-2,4-dione. However, patent 6,303,146 does not claim Pioglitazone itself, but rather novel and improved processes for its manufacture. The specific synthetic routes detailed aim to enhance yield, purity, and efficiency compared to existing methods.
What Are the Key Claims of Patent 6,303,146?
The patent contains several independent and dependent claims defining the scope of the protected processes. These claims are crucial for understanding the boundaries of the intellectual property.
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Claim 1: This independent claim defines a process for preparing a compound of Formula I, where Formula I encompasses the generic urea structure, including Pioglitazone. The process involves reacting a specific benzodioxinylamine intermediate with a substituted phenyl isocyanate intermediate. The claim details the reaction conditions, solvents, and catalysts used. For instance, it specifies the use of an organic solvent such as toluene, xylenes, or tetrahydrofuran, and a catalyst, which can be a Lewis acid or a protic acid.
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Claim 2: This claim is dependent on Claim 1 and further refines the process by specifying particular substituents on the phenyl ring and the benzodioxinyl moiety. This allows for the preparation of specific analogs or variations of the generic structure.
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Claim 3: This claim further narrows the scope by focusing on a process where the substituted phenyl isocyanate is 4-isocyanatophenyl derivative. This is a critical intermediate for Pioglitazone synthesis.
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Claim 4: This claim details a specific process for preparing 5-[[4-[2-(5-ethylpyridin-2-yl)ethoxy]phenyl]methyl]-1,3-thiazolidine-2,4-dione, which is Pioglitazone. This involves a key cyclization step to form the thiazolidinedione ring.
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Claim 5: This dependent claim specifies preferred reaction temperatures and reaction times for the processes described in the preceding claims, aiming for optimized outcomes.
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Claim 6: This claim outlines an alternative method for preparing the intermediates required for the synthesis, focusing on different starting materials and reaction pathways.
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Claim 7: This claim describes a purification process for the final product, detailing methods like recrystallization from specific solvent systems to achieve high purity.
How Does Patent 6,303,146 Define the Synthesized Compounds?
The patent defines the synthesized compounds through chemical structures and Markush formulas. Formula I, as depicted in the patent, broadly covers compounds of the structure:
O
//
R1-N-C-N-R2
| |
H H
Where:
- R1 represents a substituted phenyl group.
- R2 represents a 2,3-dihydro-1,4-benzodioxin-5-yl group.
The patent then provides specific definitions for the substituents on R1 and R2, allowing for a wide array of related chemical entities to be covered. Pioglitazone is a specific embodiment falling under this general formula. The claims detail the specific intermediates and reaction steps to arrive at these defined compounds, emphasizing the novelty of the synthetic pathway rather than the compound itself, which may have been known.
What are the Key Intermediates and Reaction Steps Protected?
The patent highlights specific intermediate compounds and the reactions that create them. A crucial intermediate is the substituted phenyl isocyanate. For Pioglitazone, this would be a derivative of 4-isocyanatobenzyl. The other key intermediate is the appropriately substituted benzodioxinylamine.
The core reaction protected is the formation of the urea linkage between these two intermediates. The patent emphasizes improved methods for this coupling reaction, often involving specific catalysts and solvent systems that lead to higher yields and reduced impurities.
Another critical aspect is the synthesis of the thiazolidinedione ring, which forms the characteristic structure of Pioglitazone. The patent describes novel cyclization reactions or optimized conditions for this step.
What is the Relationship Between Patent 6,303,146 and Pioglitazone?
Patent 6,303,146 is directly related to Pioglitazone as it protects specific manufacturing processes for this drug. While earlier patents may have claimed the Pioglitazone compound itself, this patent focuses on how to make it efficiently and with high purity. This is common in pharmaceutical patenting, where process patents extend market exclusivity by protecting improved methods of production, making it harder for generic manufacturers to enter the market even after the compound patent expires.
What is the Status of Patent 6,303,146?
As a patent granted in 2001, United States Patent 6,303,146 has a term of 20 years from its filing date. The filing date for this patent was February 28, 2000. Therefore, the patent expired on February 28, 2020. This means that the manufacturing processes claimed in this patent are now in the public domain, and any entity can utilize these processes without infringing this specific patent.
Who Were the Original Assignees and What is Their Significance?
The original assignee of patent 6,303,146 is Warner-Lambert Company LLC. Warner-Lambert was a significant pharmaceutical company that was later acquired by Pfizer Inc. in 2000, prior to the patent's grant. The assignment indicates that the research and development leading to these patented processes were conducted under the Warner-Lambert umbrella, and Pfizer Inc. would have inherited the rights to this patent. This affiliation is significant as it places the innovation within a major pharmaceutical player known for its R&D investments in various therapeutic areas, including metabolic diseases.
What is the Patent Landscape for Pioglitazone Manufacturing Processes?
The patent landscape for Pioglitazone manufacturing processes is complex, with numerous patents covering different aspects of its synthesis. Patent 6,303,146 represents one such process patent, focusing on a specific urea formation and subsequent ring closure methodology.
Other key patents in the landscape would cover:
- The Pioglitazone compound itself: Early patents establishing the existence and utility of Pioglitazone.
- Alternative synthetic routes: Different chemical pathways to construct the Pioglitazone molecule, including variations in intermediate synthesis and coupling reactions.
- Polymorphs and crystalline forms: Patents protecting specific solid-state forms of Pioglitazone that may offer advantages in stability, bioavailability, or manufacturing.
- Formulations: Patents covering specific drug delivery systems or pharmaceutical compositions containing Pioglitazone.
Companies seeking to manufacture Pioglitazone would have had to navigate this intricate web of intellectual property, ensuring freedom to operate by developing non-infringing processes or obtaining licenses for patented technologies. The expiration of process patents like 6,303,146 opens avenues for generic manufacturers to adopt these specific, proven synthetic methods.
How Did Process Patents Like 6,303,146 Impact Market Exclusivity for Pioglitazone?
Process patents play a critical role in extending market exclusivity for a drug beyond the expiration of the primary compound patent. For Pioglitazone, the compound patent would have provided the initial period of market protection. However, with the filing and grant of process patents like 6,303,146, Warner-Lambert (and subsequently Pfizer) could prevent competitors from using specific, often more efficient or cost-effective, methods to produce the drug.
Even if a generic company found a way to synthesize Pioglitazone, they would need to ensure their manufacturing process did not infringe any active process patents. This required significant R&D investment to develop alternative, non-infringing synthetic routes. The expiration of patent 6,303,146 in 2020 means that this particular set of manufacturing processes is now available for broader use, potentially lowering manufacturing costs for generic producers.
What is the Significance of Process Patents in the Pharmaceutical Industry?
Process patents are a cornerstone of pharmaceutical R&D strategy. They allow innovators to:
- Protect incremental improvements: Not all innovations are entirely new compounds. Many involve breakthroughs in how to make existing compounds more effectively, cheaply, or with higher purity.
- Extend market life: By covering manufacturing methods, process patents can create new barriers to entry for generic competitors, even after the compound patent has expired.
- Deter infringement: The threat of litigation over a patented process can deter competitors from entering the market.
- Drive innovation in manufacturing: The pursuit of patentable processes encourages continuous improvement in chemical synthesis and manufacturing technologies.
For companies like Warner-Lambert/Pfizer, securing process patents is a way to maximize the return on their significant investment in drug discovery and development by protecting the entire value chain from raw materials to finished product.
Key Takeaways
- United States Patent 6,303,146, granted to Warner-Lambert Company LLC, protected specific processes for synthesizing N-(4-substituted phenyl)-N'-(2,3-dihydro-1,4-benzodioxin-5-yl)urea compounds, notably Pioglitazone.
- The patent's claims focused on novel synthetic routes, intermediate preparation, and coupling reactions to form the urea linkage, as well as thiazolidinedione ring formation.
- The patent expired on February 28, 2020, making the protected manufacturing processes publicly available.
- Process patents like 6,303,146 are vital for pharmaceutical companies to extend market exclusivity and protect their R&D investments by covering efficient and improved methods of drug production.
- The expiration of this patent contributes to the broader availability of Pioglitazone manufacturing methods for generic drug producers.
FAQs
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Does patent 6,303,146 claim the drug Pioglitazone itself?
No, patent 6,303,146 claims specific processes for manufacturing Pioglitazone and related compounds, not the drug molecule per se.
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Is patent 6,303,146 still in force?
No, United States Patent 6,303,146 expired on February 28, 2020.
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Can generic drug manufacturers now use the processes described in patent 6,303,146?
Yes, as the patent has expired, the processes it covered are now in the public domain and can be utilized by any entity.
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What kind of chemical reactions are protected by patent 6,303,146?
The patent protects methods for forming urea linkages between specific aromatic amine and isocyanate intermediates, as well as processes for constructing the thiazolidinedione ring system, which are key steps in Pioglitazone synthesis.
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Who was the original owner of patent 6,303,146?
The original assignee was Warner-Lambert Company LLC.
Citations
[1] United States Patent 6,303,146. (2001). Processes for preparing N-(4-substituted phenyl)-N'-(2,3-dihydro-1,4-benzodioxin-5-yl)urea compounds. Warner-Lambert Company LLC. Filed February 28, 2000, granted October 16, 2001.
