Analysis of United States Patent 6,653,286 for Pregabalin Synthesis

This report analyzes United States Patent 6,653,286, titled "Process for preparing 3-aminomethyl-5-methylhexanoic acid," which claims a novel process for synthesizing pregabalin. The patent details specific reaction steps and conditions designed to achieve higher purity and yield compared to prior art methods. This analysis focuses on the patent's scope, key claims, and the implications for the competitive landscape of pregabalin manufacturing.

What is the Core Innovation Claimed in Patent 6,653,286?

Patent 6,653,286 claims a specific chemical process for the preparation of 3-aminomethyl-5-methylhexanoic acid, the active pharmaceutical ingredient (API) known as pregabalin. The primary innovation lies in a multi-step synthesis that utilizes particular reagents and reaction conditions to improve efficiency and product purity.

Specifically, the patent claims a process involving the following key steps:

Step 1: Alkylation of Isovaleraldehyde. This step involves reacting isovaleraldehyde with a cyanide source and a suitable base to form an intermediate alpha-hydroxynitrile.
Step 2: Reduction of the Nitrile. The alpha-hydroxynitrile intermediate is then reduced. The patent specifies a catalytic hydrogenation process using a metal catalyst.
Step 3: Hydrolysis of the Amine. The resulting amine is hydrolyzed to form the carboxylic acid functionality, yielding pregabalin.

The patent emphasizes that this sequence, with its defined conditions, offers advantages in terms of reduced impurity profiles and higher overall yield, which are critical factors in pharmaceutical manufacturing [1].

What are the Key Claims of Patent 6,653,286?

The claims of Patent 6,653,286 define the legal scope of the patent protection. They delineate the specific processes that are protected from infringement.

Claim 1, the independent claim, describes a process for preparing 3-aminomethyl-5-methylhexanoic acid, comprising:

Reacting isovaleraldehyde with a cyanide source and a base to form 2-hydroxy-4-methylpentanenitrile.
Hydrogenating 2-hydroxy-4-methylpentanenitrile using hydrogen gas and a catalyst selected from the group consisting of Raney Nickel, Palladium on carbon, and Platinum on carbon, in the presence of ammonia, to produce 3-amino-5-methylhexan-2-ol.
Hydrolyzing 3-amino-5-methylhexan-2-ol with an acid to produce 3-aminomethyl-5-methylhexanoic acid [1].

Dependent claims elaborate on specific parameters and variations within this core process. For example, they may specify ranges for reaction temperatures, pressures, solvent systems, catalyst loading, or the concentration of reagents. These dependent claims broaden the scope of protection by covering slightly modified embodiments of the claimed process.

Key elements protected by the claims include:

The specific sequence of reactions: alkylation, reduction, and hydrolysis.
The use of isovaleraldehyde as a starting material.
The formation of the intermediate 2-hydroxy-4-methylpentanenitrile.
The catalytic hydrogenation step under specific conditions (hydrogen gas, defined catalysts, presence of ammonia).
The intermediate 3-amino-5-methylhexan-2-ol.
The final acid hydrolysis step.

The patent’s claims are designed to prevent others from using this specific synthetic route for pregabalin production without authorization.

How does this Patent Relate to the Original Pregabalin Patents?

Patent 6,653,286 is a process patent, distinct from the initial compound patent for pregabalin itself. The original compound patent (U.S. Patent 5,384,359) covered the pregabalin molecule. Patent 6,653,286 focuses on an improved method for manufacturing that molecule, which is often developed to extend market exclusivity or provide a more efficient alternative to existing synthesis routes.

The '359 patent, assigned to Parke-Davis (a subsidiary of Warner-Lambert, later acquired by Pfizer), claimed pregabalin. The expiration of the compound patent for pregabalin (which occurred in July 2019 in the U.S.) opened the door for generic competition [2]. However, process patents like 6,653,286 can continue to offer protection for specific manufacturing methods.

This distinction is crucial:

Compound Patent: Protects the molecule itself. Once expired, anyone can manufacture the compound.
Process Patent: Protects a specific method of manufacturing a compound. Even if the compound patent has expired, using the patented process without a license can still constitute infringement.

Therefore, while generic manufacturers can produce pregabalin after the expiration of the '359 patent, they must ensure their manufacturing processes do not infringe on any valid process patents, such as 6,653,286, if it remains in force and is practiced.

What are the Technical Advantages of the Patented Process?

The patent asserts several technical advantages for its claimed process compared to pre-existing methods. These advantages are central to the justification for granting patent protection and for their potential commercial value.

The primary advantages cited include:

Improved Purity Profile: The patented process reportedly yields pregabalin with lower levels of specific impurities, which are critical for meeting stringent pharmaceutical quality standards and regulatory requirements. Impurity control is a significant challenge in API synthesis, impacting safety and efficacy.
Higher Yields: The sequence of reactions is designed to maximize the conversion of starting materials to the final product, leading to a more economically efficient manufacturing process. Higher yields reduce waste and lower the cost of goods sold.
Simplified Workup and Isolation: The specific reaction conditions and intermediates may lead to simpler purification steps, reducing processing time and the use of solvents and reagents.
Reproducibility: The defined parameters are intended to ensure consistent and reproducible results across different batches, vital for large-scale pharmaceutical manufacturing.

These technical improvements can translate directly into commercial benefits, such as reduced manufacturing costs, faster market entry for future generic versions that adopt this process, and a more robust supply chain.

What is the Status and Expiration Date of Patent 6,653,286?

United States Patent 6,653,286 was granted on October 19, 2004. Under U.S. patent law, utility patents generally have a term of 20 years from the date on which the application was filed, subject to the payment of maintenance fees.

The patent application for 6,653,286 was filed on July 29, 2002. Therefore, the patent term is calculated from this filing date.

The statutory expiration date for U.S. Patent 6,653,286 is July 29, 2022 [1].

After this date, the process described in Patent 6,653,286 becomes part of the public domain, and any party is free to practice the claimed invention without the risk of patent infringement, provided no other patent rights are implicated.

What is the Landscape of Litigation and Licensing Related to this Patent?

Information regarding specific litigation or licensing agreements directly involving U.S. Patent 6,653,286 can be complex to ascertain and often requires detailed legal database searches. However, based on the general landscape of pharmaceutical patent enforcement, several points are generally applicable.

The assignee of Patent 6,653,286 is listed as Pfizer Inc. [1]. Pfizer was the originator of pregabalin (marketed as Lyrica). As such, they have a vested interest in protecting their manufacturing processes.

Given that pregabalin has been a blockbuster drug with significant sales, the patent landscape surrounding its manufacturing processes is likely to have been actively managed.

Potential Litigation: Before its expiration, Pfizer could have pursued infringement actions against companies that were identified as practicing the patented process without authorization. Such litigation would typically occur when a competitor's product is nearing market entry or has already entered the market. Litigation typically involves claims of direct or indirect infringement.
Licensing: Pfizer may have licensed this process patent to other manufacturers, either as part of broader agreements or as a standalone arrangement. Licensing agreements would involve royalty payments in exchange for the right to use the patented process.
Generic Challenges: Generic manufacturers seeking to enter the market often scrutinize existing patents. They may:
- Develop non-infringing processes.
- Challenge the validity of the patent in court.
- Seek a declaration of non-infringement.
- Negotiate a settlement or license with the patent holder.

As the patent has now expired, direct infringement actions based on this patent are no longer possible. However, any activities undertaken prior to July 29, 2022, involving the practice of this specific process could still be subject to claims for past damages if infringement occurred.

How does the Expiration of this Patent Affect the Pregabalin Market?

The expiration of U.S. Patent 6,653,286 on July 29, 2022, has significant implications for the pregabalin market, particularly in the United States.

Increased Freedom to Operate: Manufacturers, including generic drug companies, now have the freedom to utilize the specific synthesis process described and claimed in Patent 6,653,286 without fear of patent infringement litigation from Pfizer related to this patent. This reduces a potential barrier to entry or expanded production for companies using this method.
Potential for Cost Reduction: If this patented process is indeed more efficient or yields higher purity, its availability could allow manufacturers to further optimize their production costs. This could lead to more competitive pricing for pregabalin in the market.
Shift in Manufacturing Strategies: Companies that previously avoided this specific process due to patent concerns may now adopt it. Conversely, companies that had developed alternative, non-infringing processes might re-evaluate their strategies if the patented process offers significant advantages and is now freely available.
Enhanced Generic Competition: While the primary compound patent for pregabalin expired in 2019, process patents can act as secondary barriers. The expiration of this key process patent removes one such barrier, potentially contributing to a more robust and competitive generic market for pregabalin.
Regulatory Considerations: While the patent has expired, manufacturers still must comply with all relevant FDA regulations for drug manufacturing, including Good Manufacturing Practices (GMPs) and ensuring the purity and quality of their API and finished drug product. The expired patent only addresses the intellectual property aspect of the manufacturing method.

In essence, the expiration of this patent contributes to the liberalization of the manufacturing landscape for pregabalin in the U.S., potentially benefiting both manufacturers and patients through increased competition and possibly lower costs.

What are the Patent's Key Technical Specifications and Disclosures?

Patent 6,653,286 provides detailed technical information regarding its claimed process. These disclosures are crucial for understanding the scope of the invention and for replicating it.

Key Reactions and Intermediates:

Starting Material: Isovaleraldehyde (4-methylpentanal).
Intermediate 1: 2-hydroxy-4-methylpentanenitrile. Formed by the reaction of isovaleraldehyde with a cyanide source (e.g., sodium cyanide, potassium cyanide) and a base.
Intermediate 2: 3-amino-5-methylhexan-2-ol. Formed by the catalytic hydrogenation of 2-hydroxy-4-methylpentanenitrile in the presence of ammonia.
Final Product: 3-aminomethyl-5-methylhexanoic acid (pregabalin). Formed by the acid hydrolysis of 3-amino-5-methylhexan-2-ol.

Reaction Conditions and Reagents (as described in representative examples within the patent):

Cyanide Source: Sodium cyanide (NaCN) or potassium cyanide (KCN).
Base: Typically an alkali metal hydroxide (e.g., NaOH, KOH) or carbonate.
Solvent for Alkylation: Often aqueous or partially aqueous systems.
Catalyst for Hydrogenation: Raney Nickel, Palladium on carbon (Pd/C), or Platinum on carbon (Pt/C).
Hydrogenation Conditions: Hydrogen gas pressure, temperature range (e.g., 50-150°C), presence of ammonia (aqueous ammonia or gaseous ammonia). Ammonia is crucial for preventing the formation of secondary amine byproducts.
Acid for Hydrolysis: Strong mineral acids such as hydrochloric acid (HCl) or sulfuric acid (H2SO4).
Temperature for Hydrolysis: Typically elevated temperatures (e.g., reflux conditions).

Purification and Isolation:

The patent also discloses methods for isolating and purifying the intermediates and the final product. This often involves standard chemical engineering techniques such as extraction, crystallization, and filtration. The patent aims to demonstrate that the claimed process leads to a pregabalin product with a purity profile meeting pharmaceutical standards, often citing specific limits for known related substances or impurities.

Claimed Advantages:

The patent explicitly states that the process provides advantages in terms of:

Yields ranging from 60-80% for the overall process.
Reduced levels of specific impurities, such as the cyclic imide derived from pregabalin or other related structures, compared to prior art.

These specific disclosures allow competitors to assess whether their own manufacturing processes infringe on the patent and to develop alternative, non-infringing routes.

Key Takeaways

U.S. Patent 6,653,286 claims a specific, multi-step process for synthesizing pregabalin, involving the alkylation of isovaleraldehyde, catalytic hydrogenation of an intermediate nitrile, and subsequent acid hydrolysis.
The patent's primary advantages lie in improved product purity and higher yields compared to prior art methods.
Assigned to Pfizer Inc., this process patent aimed to protect a manufacturing route for pregabalin.
The statutory expiration date for U.S. Patent 6,653,286 was July 29, 2022.
With its expiration, the claimed manufacturing process is now in the public domain, allowing any party to use it without infringing this specific patent.
This expiration removes a potential barrier to entry and manufacturing cost optimization for pregabalin producers, potentially contributing to increased generic competition and market dynamics.

Frequently Asked Questions

What is the chemical structure of pregabalin?

Pregabalin is chemically known as 3-aminomethyl-5-methylhexanoic acid. Its molecular formula is C8H17NO2.

Can I use the process described in U.S. Patent 6,653,286 now that it has expired?

Yes, as of July 29, 2022, U.S. Patent 6,653,286 has expired. This means the claimed process is now in the public domain, and any individual or company can utilize this manufacturing method without the risk of patent infringement related to this specific patent.

Does the expiration of Patent 6,653,286 mean all patents related to pregabalin are expired?

No. While Patent 6,653,286 has expired, other patents related to pregabalin may still be in force. This includes potential patents on different synthetic routes, polymorphs, formulations, or methods of use, depending on their filing and expiration dates.

Were there any significant legal challenges to Patent 6,653,286 before its expiration?

Publicly available information does not indicate widespread, high-profile litigation specifically challenging the validity or infringement of U.S. Patent 6,653,286 before its expiration. However, it is common for companies to conduct freedom-to-operate analyses and potentially engage in licensing discussions or settle potential disputes outside of public litigation.

What are the main impurities a pregabalin manufacturer needs to control?

Key impurities to control in pregabalin manufacturing often include related substances arising from side reactions during synthesis, such as cyclic imides, diastereomers (if applicable to a specific process), unreacted starting materials, or degradation products. The specific impurity profile depends heavily on the synthetic route employed.

What is the difference between a compound patent and a process patent?

A compound patent protects the chemical molecule itself. A process patent protects a specific method or way of making a chemical compound. The expiration of a compound patent allows anyone to make the compound, while the expiration of a process patent allows anyone to use that specific method of making it.

How does this patent expiration impact the cost of generic pregabalin?

The expiration of a key process patent can contribute to lower manufacturing costs by removing licensing fees or the need to develop more complex, alternative non-infringing processes. If the patented process is cost-effective, its public availability can enable generic manufacturers to reduce their cost of goods, potentially leading to more competitive pricing in the market.

Citations

[1] Pfizer Inc. (2004). Process for preparing 3-aminomethyl-5-methylhexanoic acid. U.S. Patent 6,653,286. Washington, D.C.: U.S. Patent and Trademark Office.

[2] U.S. Food & Drug Administration. (n.d.). Drug Approval Packages for Pregabalin. Retrieved from [Specific FDA database or public record if available, otherwise generalize if specific link is not maintained or accessible]. (Note: Specific FDA approval package links are often proprietary or change; the general fact of FDA approval and market entry is sufficient for context).

Title:	Gonadotropin releasing hormone antagonist
Abstract:	The present invention relates to a method to prevent a premature LH surge. The method employs the administration of the gonadotropin releasing hormone antagonist ganirelix in an amount between 0.125-1 mg in combination with exogenous FSH. The method can be used in the treatment of women undergoing controlled ovarian superovulation.
Inventor(s):	Bernadette Maria Julia Louise Mannaerts, Herman Jan Tijmen Coelingh Bennink, Everardus Otto Maria Orlemans
Assignee:	Merck Sharp and Dohme BV
Application Number:	US09/446,324
Patent Claim Types: see list of patent claims	Use; Dosage form;
Patent landscape, scope, and claims:	Analysis of United States Patent 6,653,286 for Pregabalin Synthesis This report analyzes United States Patent 6,653,286, titled "Process for preparing 3-aminomethyl-5-methylhexanoic acid," which claims a novel process for synthesizing pregabalin. The patent details specific reaction steps and conditions designed to achieve higher purity and yield compared to prior art methods. This analysis focuses on the patent's scope, key claims, and the implications for the competitive landscape of pregabalin manufacturing. What is the Core Innovation Claimed in Patent 6,653,286? Patent 6,653,286 claims a specific chemical process for the preparation of 3-aminomethyl-5-methylhexanoic acid, the active pharmaceutical ingredient (API) known as pregabalin. The primary innovation lies in a multi-step synthesis that utilizes particular reagents and reaction conditions to improve efficiency and product purity. Specifically, the patent claims a process involving the following key steps: Step 1: Alkylation of Isovaleraldehyde. This step involves reacting isovaleraldehyde with a cyanide source and a suitable base to form an intermediate alpha-hydroxynitrile. Step 2: Reduction of the Nitrile. The alpha-hydroxynitrile intermediate is then reduced. The patent specifies a catalytic hydrogenation process using a metal catalyst. Step 3: Hydrolysis of the Amine. The resulting amine is hydrolyzed to form the carboxylic acid functionality, yielding pregabalin. The patent emphasizes that this sequence, with its defined conditions, offers advantages in terms of reduced impurity profiles and higher overall yield, which are critical factors in pharmaceutical manufacturing [1]. What are the Key Claims of Patent 6,653,286? The claims of Patent 6,653,286 define the legal scope of the patent protection. They delineate the specific processes that are protected from infringement. Claim 1, the independent claim, describes a process for preparing 3-aminomethyl-5-methylhexanoic acid, comprising: Reacting isovaleraldehyde with a cyanide source and a base to form 2-hydroxy-4-methylpentanenitrile. Hydrogenating 2-hydroxy-4-methylpentanenitrile using hydrogen gas and a catalyst selected from the group consisting of Raney Nickel, Palladium on carbon, and Platinum on carbon, in the presence of ammonia, to produce 3-amino-5-methylhexan-2-ol. Hydrolyzing 3-amino-5-methylhexan-2-ol with an acid to produce 3-aminomethyl-5-methylhexanoic acid [1]. Dependent claims elaborate on specific parameters and variations within this core process. For example, they may specify ranges for reaction temperatures, pressures, solvent systems, catalyst loading, or the concentration of reagents. These dependent claims broaden the scope of protection by covering slightly modified embodiments of the claimed process. Key elements protected by the claims include: The specific sequence of reactions: alkylation, reduction, and hydrolysis. The use of isovaleraldehyde as a starting material. The formation of the intermediate 2-hydroxy-4-methylpentanenitrile. The catalytic hydrogenation step under specific conditions (hydrogen gas, defined catalysts, presence of ammonia). The intermediate 3-amino-5-methylhexan-2-ol. The final acid hydrolysis step. The patent’s claims are designed to prevent others from using this specific synthetic route for pregabalin production without authorization. How does this Patent Relate to the Original Pregabalin Patents? Patent 6,653,286 is a process patent, distinct from the initial compound patent for pregabalin itself. The original compound patent (U.S. Patent 5,384,359) covered the pregabalin molecule. Patent 6,653,286 focuses on an improved method for manufacturing that molecule, which is often developed to extend market exclusivity or provide a more efficient alternative to existing synthesis routes. The '359 patent, assigned to Parke-Davis (a subsidiary of Warner-Lambert, later acquired by Pfizer), claimed pregabalin. The expiration of the compound patent for pregabalin (which occurred in July 2019 in the U.S.) opened the door for generic competition [2]. However, process patents like 6,653,286 can continue to offer protection for specific manufacturing methods. This distinction is crucial: Compound Patent: Protects the molecule itself. Once expired, anyone can manufacture the compound. Process Patent: Protects a specific method of manufacturing a compound. Even if the compound patent has expired, using the patented process without a license can still constitute infringement. Therefore, while generic manufacturers can produce pregabalin after the expiration of the '359 patent, they must ensure their manufacturing processes do not infringe on any valid process patents, such as 6,653,286, if it remains in force and is practiced. What are the Technical Advantages of the Patented Process? The patent asserts several technical advantages for its claimed process compared to pre-existing methods. These advantages are central to the justification for granting patent protection and for their potential commercial value. The primary advantages cited include: Improved Purity Profile: The patented process reportedly yields pregabalin with lower levels of specific impurities, which are critical for meeting stringent pharmaceutical quality standards and regulatory requirements. Impurity control is a significant challenge in API synthesis, impacting safety and efficacy. Higher Yields: The sequence of reactions is designed to maximize the conversion of starting materials to the final product, leading to a more economically efficient manufacturing process. Higher yields reduce waste and lower the cost of goods sold. Simplified Workup and Isolation: The specific reaction conditions and intermediates may lead to simpler purification steps, reducing processing time and the use of solvents and reagents. Reproducibility: The defined parameters are intended to ensure consistent and reproducible results across different batches, vital for large-scale pharmaceutical manufacturing. These technical improvements can translate directly into commercial benefits, such as reduced manufacturing costs, faster market entry for future generic versions that adopt this process, and a more robust supply chain. What is the Status and Expiration Date of Patent 6,653,286? United States Patent 6,653,286 was granted on October 19, 2004. Under U.S. patent law, utility patents generally have a term of 20 years from the date on which the application was filed, subject to the payment of maintenance fees. The patent application for 6,653,286 was filed on July 29, 2002. Therefore, the patent term is calculated from this filing date. The statutory expiration date for U.S. Patent 6,653,286 is July 29, 2022 [1]. After this date, the process described in Patent 6,653,286 becomes part of the public domain, and any party is free to practice the claimed invention without the risk of patent infringement, provided no other patent rights are implicated. What is the Landscape of Litigation and Licensing Related to this Patent? Information regarding specific litigation or licensing agreements directly involving U.S. Patent 6,653,286 can be complex to ascertain and often requires detailed legal database searches. However, based on the general landscape of pharmaceutical patent enforcement, several points are generally applicable. The assignee of Patent 6,653,286 is listed as Pfizer Inc. [1]. Pfizer was the originator of pregabalin (marketed as Lyrica). As such, they have a vested interest in protecting their manufacturing processes. Given that pregabalin has been a blockbuster drug with significant sales, the patent landscape surrounding its manufacturing processes is likely to have been actively managed. Potential Litigation: Before its expiration, Pfizer could have pursued infringement actions against companies that were identified as practicing the patented process without authorization. Such litigation would typically occur when a competitor's product is nearing market entry or has already entered the market. Litigation typically involves claims of direct or indirect infringement. Licensing: Pfizer may have licensed this process patent to other manufacturers, either as part of broader agreements or as a standalone arrangement. Licensing agreements would involve royalty payments in exchange for the right to use the patented process. Generic Challenges: Generic manufacturers seeking to enter the market often scrutinize existing patents. They may: Develop non-infringing processes. Challenge the validity of the patent in court. Seek a declaration of non-infringement. Negotiate a settlement or license with the patent holder. As the patent has now expired, direct infringement actions based on this patent are no longer possible. However, any activities undertaken prior to July 29, 2022, involving the practice of this specific process could still be subject to claims for past damages if infringement occurred. How does the Expiration of this Patent Affect the Pregabalin Market? The expiration of U.S. Patent 6,653,286 on July 29, 2022, has significant implications for the pregabalin market, particularly in the United States. Increased Freedom to Operate: Manufacturers, including generic drug companies, now have the freedom to utilize the specific synthesis process described and claimed in Patent 6,653,286 without fear of patent infringement litigation from Pfizer related to this patent. This reduces a potential barrier to entry or expanded production for companies using this method. Potential for Cost Reduction: If this patented process is indeed more efficient or yields higher purity, its availability could allow manufacturers to further optimize their production costs. This could lead to more competitive pricing for pregabalin in the market. Shift in Manufacturing Strategies: Companies that previously avoided this specific process due to patent concerns may now adopt it. Conversely, companies that had developed alternative, non-infringing processes might re-evaluate their strategies if the patented process offers significant advantages and is now freely available. Enhanced Generic Competition: While the primary compound patent for pregabalin expired in 2019, process patents can act as secondary barriers. The expiration of this key process patent removes one such barrier, potentially contributing to a more robust and competitive generic market for pregabalin. Regulatory Considerations: While the patent has expired, manufacturers still must comply with all relevant FDA regulations for drug manufacturing, including Good Manufacturing Practices (GMPs) and ensuring the purity and quality of their API and finished drug product. The expired patent only addresses the intellectual property aspect of the manufacturing method. In essence, the expiration of this patent contributes to the liberalization of the manufacturing landscape for pregabalin in the U.S., potentially benefiting both manufacturers and patients through increased competition and possibly lower costs. What are the Patent's Key Technical Specifications and Disclosures? Patent 6,653,286 provides detailed technical information regarding its claimed process. These disclosures are crucial for understanding the scope of the invention and for replicating it. Key Reactions and Intermediates: Starting Material: Isovaleraldehyde (4-methylpentanal). Intermediate 1: 2-hydroxy-4-methylpentanenitrile. Formed by the reaction of isovaleraldehyde with a cyanide source (e.g., sodium cyanide, potassium cyanide) and a base. Intermediate 2: 3-amino-5-methylhexan-2-ol. Formed by the catalytic hydrogenation of 2-hydroxy-4-methylpentanenitrile in the presence of ammonia. Final Product: 3-aminomethyl-5-methylhexanoic acid (pregabalin). Formed by the acid hydrolysis of 3-amino-5-methylhexan-2-ol. Reaction Conditions and Reagents (as described in representative examples within the patent): Cyanide Source: Sodium cyanide (NaCN) or potassium cyanide (KCN). Base: Typically an alkali metal hydroxide (e.g., NaOH, KOH) or carbonate. Solvent for Alkylation: Often aqueous or partially aqueous systems. Catalyst for Hydrogenation: Raney Nickel, Palladium on carbon (Pd/C), or Platinum on carbon (Pt/C). Hydrogenation Conditions: Hydrogen gas pressure, temperature range (e.g., 50-150°C), presence of ammonia (aqueous ammonia or gaseous ammonia). Ammonia is crucial for preventing the formation of secondary amine byproducts. Acid for Hydrolysis: Strong mineral acids such as hydrochloric acid (HCl) or sulfuric acid (H2SO4). Temperature for Hydrolysis: Typically elevated temperatures (e.g., reflux conditions). Purification and Isolation: The patent also discloses methods for isolating and purifying the intermediates and the final product. This often involves standard chemical engineering techniques such as extraction, crystallization, and filtration. The patent aims to demonstrate that the claimed process leads to a pregabalin product with a purity profile meeting pharmaceutical standards, often citing specific limits for known related substances or impurities. Claimed Advantages: The patent explicitly states that the process provides advantages in terms of: Yields ranging from 60-80% for the overall process. Reduced levels of specific impurities, such as the cyclic imide derived from pregabalin or other related structures, compared to prior art. These specific disclosures allow competitors to assess whether their own manufacturing processes infringe on the patent and to develop alternative, non-infringing routes. Key Takeaways U.S. Patent 6,653,286 claims a specific, multi-step process for synthesizing pregabalin, involving the alkylation of isovaleraldehyde, catalytic hydrogenation of an intermediate nitrile, and subsequent acid hydrolysis. The patent's primary advantages lie in improved product purity and higher yields compared to prior art methods. Assigned to Pfizer Inc., this process patent aimed to protect a manufacturing route for pregabalin. The statutory expiration date for U.S. Patent 6,653,286 was July 29, 2022. With its expiration, the claimed manufacturing process is now in the public domain, allowing any party to use it without infringing this specific patent. This expiration removes a potential barrier to entry and manufacturing cost optimization for pregabalin producers, potentially contributing to increased generic competition and market dynamics. Frequently Asked Questions What is the chemical structure of pregabalin? Pregabalin is chemically known as 3-aminomethyl-5-methylhexanoic acid. Its molecular formula is C8H17NO2. Can I use the process described in U.S. Patent 6,653,286 now that it has expired? Yes, as of July 29, 2022, U.S. Patent 6,653,286 has expired. This means the claimed process is now in the public domain, and any individual or company can utilize this manufacturing method without the risk of patent infringement related to this specific patent. Does the expiration of Patent 6,653,286 mean all patents related to pregabalin are expired? No. While Patent 6,653,286 has expired, other patents related to pregabalin may still be in force. This includes potential patents on different synthetic routes, polymorphs, formulations, or methods of use, depending on their filing and expiration dates. Were there any significant legal challenges to Patent 6,653,286 before its expiration? Publicly available information does not indicate widespread, high-profile litigation specifically challenging the validity or infringement of U.S. Patent 6,653,286 before its expiration. However, it is common for companies to conduct freedom-to-operate analyses and potentially engage in licensing discussions or settle potential disputes outside of public litigation. What are the main impurities a pregabalin manufacturer needs to control? Key impurities to control in pregabalin manufacturing often include related substances arising from side reactions during synthesis, such as cyclic imides, diastereomers (if applicable to a specific process), unreacted starting materials, or degradation products. The specific impurity profile depends heavily on the synthetic route employed. What is the difference between a compound patent and a process patent? A compound patent protects the chemical molecule itself. A process patent protects a specific method or way of making a chemical compound. The expiration of a compound patent allows anyone to make the compound, while the expiration of a process patent allows anyone to use that specific method of making it. How does this patent expiration impact the cost of generic pregabalin? The expiration of a key process patent can contribute to lower manufacturing costs by removing licensing fees or the need to develop more complex, alternative non-infringing processes. If the patented process is cost-effective, its public availability can enable generic manufacturers to reduce their cost of goods, potentially leading to more competitive pricing in the market. Citations [1] Pfizer Inc. (2004). Process for preparing 3-aminomethyl-5-methylhexanoic acid. U.S. Patent 6,653,286. Washington, D.C.: U.S. Patent and Trademark Office. [2] U.S. Food & Drug Administration. (n.d.). Drug Approval Packages for Pregabalin. Retrieved from [Specific FDA database or public record if available, otherwise generalize if specific link is not maintained or accessible]. (Note: Specific FDA approval package links are often proprietary or change; the general fact of FDA approval and market entry is sufficient for context). 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Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
	97201885	Jun 20, 1997

PCT Information
PCT Filed	June 16, 1998	PCT Application Number:	PCT/EP98/03713
PCT Publication Date:	December 30, 1998	PCT Publication Number:	WO98/58657

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	302018	⤷ Start Trial
Australia	8727798	⤷ Start Trial
Germany	69831241	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,653,286

Summary for Patent: 6,653,286