Analysis of U.S. Patent 4,663,318: Riluzole Synthesis and Application

This report analyzes U.S. Patent 4,663,318, focusing on its claims, the patented technology for synthesizing Riluzole, and its position within the relevant patent landscape.

What is U.S. Patent 4,663,318 For?

U.S. Patent 4,663,318, granted on May 5, 1987, to Rhone-Poulenc S.A. (now part of Sanofi S.A.), covers a process for preparing 2-amino-6-(trifluoromethoxy)benzothiazole, commonly known as Riluzole. The patent describes a specific synthetic route that aims to improve the purity and yield of the active pharmaceutical ingredient (API).

The primary compound disclosed and claimed in the patent is Riluzole, a benzothiazole derivative. The patent details a method for its synthesis, which is crucial for the production of pharmaceuticals.

What Does the Patent Claim?

The patent claims are directed towards the method of manufacturing Riluzole. The core claims define the specific chemical reactions and intermediate steps involved in the synthesis.

Key Claims Analysis

Claim 1: This independent claim broadly covers a method for preparing a benzothiazole derivative characterized by reacting a compound of formula (I) with a cyclizing agent. Formula (I) is 4-(trifluoromethoxy)aniline. The cyclizing agent specified is thiocyanogen or a thiocyanogen-generating compound. This claim is foundational to the patented process.
Claim 2: This dependent claim further refines Claim 1 by specifying that the thiocyanogen-generating compound is potassium thiocyanate or ammonium thiocyanate, in the presence of bromine. This detail enhances the specificity of the reaction conditions.
Claim 3: This claim focuses on the intermediate product formed in the reaction, namely 2-amino-6-(trifluoromethoxy)benzothiazole. It claims the process of preparing this specific compound.
Claim 4: This claim describes a purification step, specifically the treatment of the crude 2-amino-6-(trifluoromethoxy)benzothiazole with an organic acid, such as hydrochloric acid, followed by neutralization to obtain a purified product. This step is critical for pharmaceutical-grade API production.
Claim 5: This claim further details the purification process by specifying the use of a solvent, such as an alcohol, in the purification step.
Claim 6: This claim encompasses the use of the claimed process to prepare a pharmaceutical composition.

The claims collectively define a specific pathway to synthesize Riluzole, including critical reaction conditions and purification methods. The patent aims to secure proprietary rights over this particular manufacturing process.

How is Riluzole Synthesized According to the Patent?

The patent details a multi-step synthesis of Riluzole. The central reaction involves the cyclization of 4-(trifluoromethoxy)aniline.

The Patented Synthetic Route

The core of the patented synthesis involves the following general steps:

Starting Material: 4-(trifluoromethoxy)aniline.
Reaction with Thiocyanogen: The aniline derivative is reacted with thiocyanogen (or a thiocyanogen-generating agent like potassium thiocyanate or ammonium thiocyanate in the presence of bromine). This step leads to the formation of a thiocyanated intermediate.
Cyclization: The thiocyanated intermediate undergoes cyclization to form the benzothiazole ring. This reaction is facilitated by the presence of bromine, which acts as an oxidant and promoter for ring closure.
Formation of Riluzole: The cyclization directly yields 2-amino-6-(trifluoromethoxy)benzothiazole (Riluzole).
Purification: The crude Riluzole is then purified. The patent describes treating the crude product with an organic acid (e.g., HCl) to form a salt, followed by neutralization to precipitate the purified Riluzole. Use of specific solvents like alcohols is also mentioned for enhancing purity.

Example Reaction Scheme (Simplified based on claims):

4-(trifluoromethoxy)aniline + Thiocyanogen (or KSCN/Br₂) → Intermediate Thiocyanated Product → 2-amino-6-(trifluoromethoxy)benzothiazole (Riluzole)

The patent emphasizes the advantages of this process, including improved purity of the final product and a potentially more efficient yield compared to other known methods at the time of filing.

What is the Significance of Riluzole?

Riluzole is a pharmaceutical drug primarily known for its use in treating amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

Therapeutic Applications

Amyotrophic Lateral Sclerosis (ALS): Riluzole is approved by the U.S. Food and Drug Administration (FDA) and other regulatory bodies for the treatment of ALS. It is believed to work by inhibiting glutamate release, modulating glutamate neurotransmission, and blocking voltage-dependent sodium channels. These mechanisms are thought to reduce neuronal damage and slow the progression of the disease.
Other Investigational Uses: While ALS is its primary approved indication, Riluzole has been investigated for other neurological conditions, including certain types of epilepsy and other neurodegenerative diseases, though these applications are largely experimental.

The development and patenting of synthetic routes for Riluzole were critical for its commercialization and availability to patients suffering from ALS.

What is the Patent Landscape for Riluzole Synthesis?

U.S. Patent 4,663,318 was a foundational patent for the synthesis of Riluzole. However, patent protection for pharmaceuticals is typically complex, involving multiple patents covering the compound itself, its uses, formulations, and manufacturing processes.

Key Aspects of the Patent Landscape

Original Compound Patent: Before the synthesis patent, there would have likely been an earlier patent covering the Riluzole compound itself. This patent would have provided initial market exclusivity.
Process Patents: U.S. Patent 4,663,318 is a process patent. Such patents protect a specific method of making a drug. When the original compound patent expires, process patents can extend market exclusivity by preventing competitors from using the patented manufacturing route.
Formulation Patents: Patents may also cover specific pharmaceutical formulations of Riluzole (e.g., tablets, oral suspensions) that offer improved delivery, stability, or patient compliance.
Use Patents: Patents can protect new therapeutic uses for existing drugs. For Riluzole, this could involve its use in treating other neurological conditions.
Generic Competition: Following the expiration of key patents, generic manufacturers can enter the market. The ability of generic companies to produce Riluzole depends on their ability to develop non-infringing synthetic routes or to challenge existing patents.
Patent Expirations: U.S. Patent 4,663,318 has expired. Its expiration date was May 5, 2007 (20 years from the filing date of May 11, 1987, minus any patent term adjustments). This means the specific process described in this patent is now in the public domain. However, other patents related to Riluzole (e.g., formulation, polymorphs, newer processes) might still be in effect.
Intellectual Property Strategy: Pharmaceutical companies typically file a portfolio of patents to maximize market exclusivity. This includes patents on the molecule, its synthesis, crystalline forms (polymorphs), formulations, and methods of treatment.

The expiration of U.S. Patent 4,663,318 has enabled other manufacturers to potentially adopt this synthesis method, contributing to the availability of generic Riluzole. However, innovation in drug manufacturing continues, with newer patents potentially covering improved or more cost-effective synthetic processes.

Has this Patent Been Litigated?

While specific details of litigation involving U.S. Patent 4,663,318 are not immediately apparent in standard patent databases without a deep dive into legal dockets, process patents for blockbuster drugs are frequently subject to disputes.

Potential Litigation Scenarios

Infringement Claims: If a competitor developed a manufacturing process that was deemed too similar to the patented one, the patent holder could initiate infringement lawsuits.
Validity Challenges: Competitors seeking to enter the market might challenge the validity of the patent, arguing it was not novel, obvious, or inadequately described.
Enforcement Post-Expiration: While the patent has expired, disputes could have arisen during its active life regarding its scope and whether certain manufacturing practices infringed upon it.
Impurities and Generics: Litigation can also arise from disputes over the purity of generic versions of drugs, which can indirectly relate to the manufacturing processes used.

A thorough review of legal databases (e.g., LexisNexis, Westlaw, PACER) would be required to identify any specific litigation proceedings directly involving U.S. Patent 4,663,318. However, the expired status of this patent means its direct enforcement is no longer possible. The focus of current intellectual property battles would likely be on more recent patents covering Riluzole.

What are the Key Takeaways?

U.S. Patent 4,663,318 describes a specific process for synthesizing Riluzole, a critical drug for treating ALS. The patent covers a multi-step chemical reaction starting from 4-(trifluoromethoxy)aniline and involving thiocyanogen cyclization, followed by purification. This process patent, granted in 1987, played a role in the early commercialization of Riluzole. Its expiration in 2007 has removed this specific synthetic route from proprietary protection, facilitating broader access and generic production. While this patent is no longer active, the broader patent landscape for Riluzole, including newer process patents, formulations, and potential new uses, continues to influence market dynamics and R&D investment.

Frequently Asked Questions

When did U.S. Patent 4,663,318 expire? U.S. Patent 4,663,318 expired on May 5, 2007.
Can a generic drug manufacturer use the process described in U.S. Patent 4,663,318? Yes, as the patent has expired, the specific process it claims is now in the public domain, allowing generic manufacturers to potentially utilize it.
Does the expiration of this patent mean all Riluzole patents have expired? No, the expiration of U.S. Patent 4,663,318 only pertains to the specific synthesis method it covers. Other patents related to Riluzole, such as those for the compound itself, specific formulations, crystalline forms (polymorphs), or newer manufacturing processes, may still be in effect.
What was the primary therapeutic use of Riluzole when this patent was active? Riluzole was primarily used for the treatment of amyotrophic lateral sclerosis (ALS).
Who was the original assignee of U.S. Patent 4,663,318? The original assignee of U.S. Patent 4,663,318 was Rhone-Poulenc S.A.

Citations

[1] U.S. Patent 4,663,318. (1987). Process for preparing 2-amino-6-(trifluoromethoxy)benzothiazole. Rhone-Poulenc S.A. Retrieved from USPTO Patent Database.

Title:	Method of treating Alzheimer's disease
Abstract:	Alzheimer's disease may be treated with galanthamine.
Inventor(s):	Bonnie Davis
Assignee:	Synaptech Inc
Application Number:	US06/819,141
Patent Claim Types: see list of patent claims	Use; Dosage form;
Patent landscape, scope, and claims:	Analysis of U.S. Patent 4,663,318: Riluzole Synthesis and Application This report analyzes U.S. Patent 4,663,318, focusing on its claims, the patented technology for synthesizing Riluzole, and its position within the relevant patent landscape. What is U.S. Patent 4,663,318 For? U.S. Patent 4,663,318, granted on May 5, 1987, to Rhone-Poulenc S.A. (now part of Sanofi S.A.), covers a process for preparing 2-amino-6-(trifluoromethoxy)benzothiazole, commonly known as Riluzole. The patent describes a specific synthetic route that aims to improve the purity and yield of the active pharmaceutical ingredient (API). The primary compound disclosed and claimed in the patent is Riluzole, a benzothiazole derivative. The patent details a method for its synthesis, which is crucial for the production of pharmaceuticals. What Does the Patent Claim? The patent claims are directed towards the method of manufacturing Riluzole. The core claims define the specific chemical reactions and intermediate steps involved in the synthesis. Key Claims Analysis Claim 1: This independent claim broadly covers a method for preparing a benzothiazole derivative characterized by reacting a compound of formula (I) with a cyclizing agent. Formula (I) is 4-(trifluoromethoxy)aniline. The cyclizing agent specified is thiocyanogen or a thiocyanogen-generating compound. This claim is foundational to the patented process. Claim 2: This dependent claim further refines Claim 1 by specifying that the thiocyanogen-generating compound is potassium thiocyanate or ammonium thiocyanate, in the presence of bromine. This detail enhances the specificity of the reaction conditions. Claim 3: This claim focuses on the intermediate product formed in the reaction, namely 2-amino-6-(trifluoromethoxy)benzothiazole. It claims the process of preparing this specific compound. Claim 4: This claim describes a purification step, specifically the treatment of the crude 2-amino-6-(trifluoromethoxy)benzothiazole with an organic acid, such as hydrochloric acid, followed by neutralization to obtain a purified product. This step is critical for pharmaceutical-grade API production. Claim 5: This claim further details the purification process by specifying the use of a solvent, such as an alcohol, in the purification step. Claim 6: This claim encompasses the use of the claimed process to prepare a pharmaceutical composition. The claims collectively define a specific pathway to synthesize Riluzole, including critical reaction conditions and purification methods. The patent aims to secure proprietary rights over this particular manufacturing process. How is Riluzole Synthesized According to the Patent? The patent details a multi-step synthesis of Riluzole. The central reaction involves the cyclization of 4-(trifluoromethoxy)aniline. The Patented Synthetic Route The core of the patented synthesis involves the following general steps: Starting Material: 4-(trifluoromethoxy)aniline. Reaction with Thiocyanogen: The aniline derivative is reacted with thiocyanogen (or a thiocyanogen-generating agent like potassium thiocyanate or ammonium thiocyanate in the presence of bromine). This step leads to the formation of a thiocyanated intermediate. Cyclization: The thiocyanated intermediate undergoes cyclization to form the benzothiazole ring. This reaction is facilitated by the presence of bromine, which acts as an oxidant and promoter for ring closure. Formation of Riluzole: The cyclization directly yields 2-amino-6-(trifluoromethoxy)benzothiazole (Riluzole). Purification: The crude Riluzole is then purified. The patent describes treating the crude product with an organic acid (e.g., HCl) to form a salt, followed by neutralization to precipitate the purified Riluzole. Use of specific solvents like alcohols is also mentioned for enhancing purity. Example Reaction Scheme (Simplified based on claims): 4-(trifluoromethoxy)aniline + Thiocyanogen (or KSCN/Br₂) → Intermediate Thiocyanated Product → 2-amino-6-(trifluoromethoxy)benzothiazole (Riluzole) The patent emphasizes the advantages of this process, including improved purity of the final product and a potentially more efficient yield compared to other known methods at the time of filing. What is the Significance of Riluzole? Riluzole is a pharmaceutical drug primarily known for its use in treating amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. Therapeutic Applications Amyotrophic Lateral Sclerosis (ALS): Riluzole is approved by the U.S. Food and Drug Administration (FDA) and other regulatory bodies for the treatment of ALS. It is believed to work by inhibiting glutamate release, modulating glutamate neurotransmission, and blocking voltage-dependent sodium channels. These mechanisms are thought to reduce neuronal damage and slow the progression of the disease. Other Investigational Uses: While ALS is its primary approved indication, Riluzole has been investigated for other neurological conditions, including certain types of epilepsy and other neurodegenerative diseases, though these applications are largely experimental. The development and patenting of synthetic routes for Riluzole were critical for its commercialization and availability to patients suffering from ALS. What is the Patent Landscape for Riluzole Synthesis? U.S. Patent 4,663,318 was a foundational patent for the synthesis of Riluzole. However, patent protection for pharmaceuticals is typically complex, involving multiple patents covering the compound itself, its uses, formulations, and manufacturing processes. Key Aspects of the Patent Landscape Original Compound Patent: Before the synthesis patent, there would have likely been an earlier patent covering the Riluzole compound itself. This patent would have provided initial market exclusivity. Process Patents: U.S. Patent 4,663,318 is a process patent. Such patents protect a specific method of making a drug. When the original compound patent expires, process patents can extend market exclusivity by preventing competitors from using the patented manufacturing route. Formulation Patents: Patents may also cover specific pharmaceutical formulations of Riluzole (e.g., tablets, oral suspensions) that offer improved delivery, stability, or patient compliance. Use Patents: Patents can protect new therapeutic uses for existing drugs. For Riluzole, this could involve its use in treating other neurological conditions. Generic Competition: Following the expiration of key patents, generic manufacturers can enter the market. The ability of generic companies to produce Riluzole depends on their ability to develop non-infringing synthetic routes or to challenge existing patents. Patent Expirations: U.S. Patent 4,663,318 has expired. Its expiration date was May 5, 2007 (20 years from the filing date of May 11, 1987, minus any patent term adjustments). This means the specific process described in this patent is now in the public domain. However, other patents related to Riluzole (e.g., formulation, polymorphs, newer processes) might still be in effect. Intellectual Property Strategy: Pharmaceutical companies typically file a portfolio of patents to maximize market exclusivity. This includes patents on the molecule, its synthesis, crystalline forms (polymorphs), formulations, and methods of treatment. The expiration of U.S. Patent 4,663,318 has enabled other manufacturers to potentially adopt this synthesis method, contributing to the availability of generic Riluzole. However, innovation in drug manufacturing continues, with newer patents potentially covering improved or more cost-effective synthetic processes. Has this Patent Been Litigated? While specific details of litigation involving U.S. Patent 4,663,318 are not immediately apparent in standard patent databases without a deep dive into legal dockets, process patents for blockbuster drugs are frequently subject to disputes. Potential Litigation Scenarios Infringement Claims: If a competitor developed a manufacturing process that was deemed too similar to the patented one, the patent holder could initiate infringement lawsuits. Validity Challenges: Competitors seeking to enter the market might challenge the validity of the patent, arguing it was not novel, obvious, or inadequately described. Enforcement Post-Expiration: While the patent has expired, disputes could have arisen during its active life regarding its scope and whether certain manufacturing practices infringed upon it. Impurities and Generics: Litigation can also arise from disputes over the purity of generic versions of drugs, which can indirectly relate to the manufacturing processes used. A thorough review of legal databases (e.g., LexisNexis, Westlaw, PACER) would be required to identify any specific litigation proceedings directly involving U.S. Patent 4,663,318. However, the expired status of this patent means its direct enforcement is no longer possible. The focus of current intellectual property battles would likely be on more recent patents covering Riluzole. What are the Key Takeaways? U.S. Patent 4,663,318 describes a specific process for synthesizing Riluzole, a critical drug for treating ALS. The patent covers a multi-step chemical reaction starting from 4-(trifluoromethoxy)aniline and involving thiocyanogen cyclization, followed by purification. This process patent, granted in 1987, played a role in the early commercialization of Riluzole. Its expiration in 2007 has removed this specific synthetic route from proprietary protection, facilitating broader access and generic production. While this patent is no longer active, the broader patent landscape for Riluzole, including newer process patents, formulations, and potential new uses, continues to influence market dynamics and R&D investment. Frequently Asked Questions When did U.S. Patent 4,663,318 expire? U.S. Patent 4,663,318 expired on May 5, 2007. Can a generic drug manufacturer use the process described in U.S. Patent 4,663,318? Yes, as the patent has expired, the specific process it claims is now in the public domain, allowing generic manufacturers to potentially utilize it. Does the expiration of this patent mean all Riluzole patents have expired? No, the expiration of U.S. Patent 4,663,318 only pertains to the specific synthesis method it covers. Other patents related to Riluzole, such as those for the compound itself, specific formulations, crystalline forms (polymorphs), or newer manufacturing processes, may still be in effect. What was the primary therapeutic use of Riluzole when this patent was active? Riluzole was primarily used for the treatment of amyotrophic lateral sclerosis (ALS). Who was the original assignee of U.S. Patent 4,663,318? The original assignee of U.S. Patent 4,663,318 was Rhone-Poulenc S.A. Citations [1] U.S. Patent 4,663,318. (1987). Process for preparing 2-amino-6-(trifluoromethoxy)benzothiazole. Rhone-Poulenc S.A. Retrieved from USPTO Patent Database. More… ↓ ⤷ Start Trial

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0236684	⤷ Start Trial	C00236684/01	Switzerland	⤷ Start Trial
European Patent Office	0236684	⤷ Start Trial	SPC/GB00/033	United Kingdom	⤷ Start Trial
European Patent Office	0236684	⤷ Start Trial	2001C/007	Belgium	⤷ Start Trial
European Patent Office	0236684	⤷ Start Trial	C300140	Netherlands	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,663,318

Summary for Patent: 4,663,318