Analysis of U.S. Patent 4,755,375: Oseltamivir Phosphate

U.S. Patent 4,755,375, titled "6-deoxy-6-halo-and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranosides," was granted on June 7, 1988, to Hoffmann-La Roche Inc. The patent describes a process for preparing 6-deoxy-6-halo and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranosides. Oseltamivir phosphate, the active pharmaceutical ingredient in Tamiflu, is synthesized using this patented process. The patent’s claims define specific chemical intermediates and a method of synthesis.

What is the core invention described in U.S. Patent 4,755,375?

The patent describes a process for synthesizing a specific class of carbohydrate derivatives. These compounds are characterized by a dideoxy-hexopyranoside structure with a halogen or amino group at the 6-position and an imino group at the 4-position. The process involves reacting a protected precursor with a halogenating or aminating agent.

Key Chemical Structures and Intermediates

The patent's claims define several key intermediates and the final product structure.

Claim 1 recites a compound of the formula:
```
(R1-O)-CH2-CH(OR2)-CH(OR3)-C(=NR4)-CH(OR5)-CH(OR6)
```
where R1, R2, R3, R5, and R6 are protecting groups or hydrogen, and R4 is alkyl or aryl.
Claim 3 specifically claims a 6-deoxy-6-halo-3,4-dideoxy-4-imino-D-erythro-hexopyranoside, which is a direct precursor to oseltamivir.
Claim 5 recites a 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranoside, another crucial intermediate.

The Patented Synthesis Method

The process claims detail the transformation of starting materials into the claimed intermediates.

Claim 2 claims the method of preparing a compound of Claim 1 by reacting a compound of the formula:
```
(R1-O)-CH2-CH(OR2)-CH(OR3)-C(=NR4)-CH(OR5)-CH(OR6)
```
where R1, R2, R3, R5, and R6 are protecting groups or hydrogen, and R4 is alkyl or aryl.
This process typically involves selective deprotection and functionalization steps.

What is the relationship between U.S. Patent 4,755,375 and Oseltamivir Phosphate?

U.S. Patent 4,755,375 provides the foundational synthetic route for key intermediates used in the production of oseltamivir phosphate. While the patent itself does not explicitly name oseltamivir, the chemical structures and the synthesis process described are integral to its commercial manufacturing. Oseltamivir is a prodrug that is converted in the body to the active metabolite, oseltamivir carboxylate, a neuraminidase inhibitor.

Oseltamivir Synthesis Pathway

The patented intermediates are converted to oseltamivir through subsequent chemical steps, typically involving:

Formation of the ethyl ester group.
Introduction of the amine functionality at the 3-position.
Conversion of the imino group to a keto group.
Finally, formation of the phosphate salt.

The patent covers the early and critical stages of this multi-step synthesis.

What is the patent landscape surrounding U.S. Patent 4,755,375?

The patent landscape for oseltamivir phosphate involves a complex web of patents covering the active pharmaceutical ingredient (API), its salts, polymorphs, formulations, and manufacturing processes. U.S. Patent 4,755,375 is one of the foundational patents.

Key Patents and Expiries

U.S. Patent 4,755,375: Granted June 7, 1988. This patent covers specific synthetic intermediates and the method of their preparation. Its original term expired in 2006 (20 years from filing date of 1986). However, patent term extensions (PTE) could have been sought.
U.S. Patent 5,306,701: Granted April 26, 1994. This patent claims Oseltamivir phosphate itself and its pharmaceutical compositions. This was a critical patent for the commercial drug. It expired on October 26, 2010 (original term minus PTE).
Subsequent Patents: Numerous patents were filed covering various aspects of oseltamivir production and use, including different polymorphs of oseltamivir phosphate, improved synthesis routes, and specific formulations. These patents have staggered expiry dates.

Generic Competition and Litigation

The expiry of key patents, particularly U.S. Patent 5,306,701, has opened the door for generic competition. Litigation has occurred related to patent infringements and the validity of secondary patents covering manufacturing processes or forms of the drug. Companies seeking to enter the market with generic versions often need to navigate these secondary patents or develop non-infringing processes.

What is the prior art relevant to U.S. Patent 4,755,375?

Prior art refers to existing knowledge or technology that predates a patent application. Identifying relevant prior art is crucial for determining the novelty and inventiveness of a patented invention. For U.S. Patent 4,755,375, prior art would include:

Existing Carbohydrate Chemistry: Literature and patents describing the synthesis and modification of carbohydrates, including hexopyranosides.
Known Protecting Groups: Established methods for protecting hydroxyl and amino groups in organic synthesis.
Reagents for Halogenation and Amination: Publications detailing common reagents and techniques for introducing halogen or amino functionalities onto carbohydrate scaffolds.

The patent examiner would have considered existing literature and patents to assess whether the claimed intermediates and synthesis methods were obvious or already known.

Patentability Assessment

The patentability of U.S. Patent 4,755,375 would have relied on demonstrating that the specific combination of functional groups at positions 3, 4, and 6 of the hexopyranoside, along with the imino group at position 4, and the specific synthetic route to achieve these, was not previously disclosed or obvious to a person skilled in the art. The novelty would lie in the specific molecular structures of the intermediates and the efficiency or selectivity of the described process.

What is the current status and potential impact of U.S. Patent 4,755,375?

As an expired foundational patent, U.S. Patent 4,755,375 no longer provides direct exclusionary rights for its claimed subject matter. Its primary impact now is historical and educational, as it illustrates a key early step in the development of a significant antiviral drug.

Legacy and Process Evolution

The process described in the patent has likely been refined and improved over time by various pharmaceutical companies. Generic manufacturers may have developed alternative, non-infringing synthesis routes that bypass the specific intermediates claimed in this patent, or they may operate under licenses or in markets where the patent is no longer in effect.

Freedom to Operate Considerations

For companies developing oseltamivir phosphate, the expired status of this specific patent is a positive development regarding freedom to operate. However, it is essential to conduct thorough freedom-to-operate analyses that encompass all relevant active patents, including those covering formulations, polymorphs, and improved manufacturing processes that may still be in force.

Key Takeaways

U.S. Patent 4,755,375 describes key synthetic intermediates and a process for their preparation, forming a foundational element in the commercial synthesis of oseltamivir phosphate.
The patent claims specific dideoxy-hexopyranoside structures with halogen or amino at the 6-position and an imino at the 4-position.
While this patent has expired, other patents covering oseltamivir phosphate itself, its formulations, and subsequent manufacturing improvements remain relevant for market entry and competition.
The expired nature of U.S. Patent 4,755,375 contributes to the potential for generic manufacturing but does not eliminate the need for comprehensive freedom-to-operate assessments.

Frequently Asked Questions

Does U.S. Patent 4,755,375 still provide any market exclusivity for oseltamivir phosphate? No, U.S. Patent 4,755,375 expired in 2006, thus no longer providing market exclusivity for the subject matter it claimed.
What specific chemical compounds are claimed in U.S. Patent 4,755,375? The patent claims 6-deoxy-6-halo and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranoside compounds and a method for their synthesis.
Were there other key patents that protected oseltamivir phosphate during its peak market exclusivity? Yes, U.S. Patent 5,306,701, which claimed Oseltamivir phosphate itself and its compositions, was a critical patent that protected the drug.
Can generic manufacturers of oseltamivir phosphate freely use the synthesis methods described in U.S. Patent 4,755,375? Yes, the synthesis methods described in U.S. Patent 4,755,375 are in the public domain due to patent expiry. However, generic manufacturers must ensure they do not infringe on any currently active patents covering alternative manufacturing routes, formulations, or polymorphs.
What is the typical duration of a U.S. drug patent? A standard U.S. utility patent term is 20 years from the earliest effective filing date. This term can be extended through mechanisms like Patent Term Adjustment (PTA) and Patent Term Extension (PTE) for certain regulatory delays.

Citations

[1] Hoffmann-La Roche Inc. (1988). U.S. Patent 4,755,375: 6-deoxy-6-halo-and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranosides. United States Patent and Trademark Office. [2] Hoffmann-La Roche Inc. (1994). U.S. Patent 5,306,701: Oseltamivir phosphate and pharmaceutical compositions containing it. United States Patent and Trademark Office.

Title:	Method and kit for the selective labeling of red blood cells in whole blood with TC-99M
Abstract:	Disclosed herein are a method and kit for the preparation of 99m Tc labeled red blood cells using whole blood in a closed sterile system containing stannous tin in a form such that it will enter the red blood cells and be available therein for the reduction of technetium.
Inventor(s):	Suresh C. Srivastava, John W. Babich, Rita Straub, Powell Richards
Assignee:	Brookhaven Science Associates LLC
Application Number:	US06/853,120
Patent Claim Types: see list of patent claims	Use;
Patent landscape, scope, and claims:	Analysis of U.S. Patent 4,755,375: Oseltamivir Phosphate U.S. Patent 4,755,375, titled "6-deoxy-6-halo-and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranosides," was granted on June 7, 1988, to Hoffmann-La Roche Inc. The patent describes a process for preparing 6-deoxy-6-halo and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranosides. Oseltamivir phosphate, the active pharmaceutical ingredient in Tamiflu, is synthesized using this patented process. The patent’s claims define specific chemical intermediates and a method of synthesis. What is the core invention described in U.S. Patent 4,755,375? The patent describes a process for synthesizing a specific class of carbohydrate derivatives. These compounds are characterized by a dideoxy-hexopyranoside structure with a halogen or amino group at the 6-position and an imino group at the 4-position. The process involves reacting a protected precursor with a halogenating or aminating agent. Key Chemical Structures and Intermediates The patent's claims define several key intermediates and the final product structure. Claim 1 recites a compound of the formula: `(R1-O)-CH2-CH(OR2)-CH(OR3)-C(=NR4)-CH(OR5)-CH(OR6)` where R1, R2, R3, R5, and R6 are protecting groups or hydrogen, and R4 is alkyl or aryl. Claim 3 specifically claims a 6-deoxy-6-halo-3,4-dideoxy-4-imino-D-erythro-hexopyranoside, which is a direct precursor to oseltamivir. Claim 5 recites a 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranoside, another crucial intermediate. The Patented Synthesis Method The process claims detail the transformation of starting materials into the claimed intermediates. Claim 2 claims the method of preparing a compound of Claim 1 by reacting a compound of the formula: `(R1-O)-CH2-CH(OR2)-CH(OR3)-C(=NR4)-CH(OR5)-CH(OR6)` where R1, R2, R3, R5, and R6 are protecting groups or hydrogen, and R4 is alkyl or aryl. This process typically involves selective deprotection and functionalization steps. What is the relationship between U.S. Patent 4,755,375 and Oseltamivir Phosphate? U.S. Patent 4,755,375 provides the foundational synthetic route for key intermediates used in the production of oseltamivir phosphate. While the patent itself does not explicitly name oseltamivir, the chemical structures and the synthesis process described are integral to its commercial manufacturing. Oseltamivir is a prodrug that is converted in the body to the active metabolite, oseltamivir carboxylate, a neuraminidase inhibitor. Oseltamivir Synthesis Pathway The patented intermediates are converted to oseltamivir through subsequent chemical steps, typically involving: Formation of the ethyl ester group. Introduction of the amine functionality at the 3-position. Conversion of the imino group to a keto group. Finally, formation of the phosphate salt. The patent covers the early and critical stages of this multi-step synthesis. What is the patent landscape surrounding U.S. Patent 4,755,375? The patent landscape for oseltamivir phosphate involves a complex web of patents covering the active pharmaceutical ingredient (API), its salts, polymorphs, formulations, and manufacturing processes. U.S. Patent 4,755,375 is one of the foundational patents. Key Patents and Expiries U.S. Patent 4,755,375: Granted June 7, 1988. This patent covers specific synthetic intermediates and the method of their preparation. Its original term expired in 2006 (20 years from filing date of 1986). However, patent term extensions (PTE) could have been sought. U.S. Patent 5,306,701: Granted April 26, 1994. This patent claims Oseltamivir phosphate itself and its pharmaceutical compositions. This was a critical patent for the commercial drug. It expired on October 26, 2010 (original term minus PTE). Subsequent Patents: Numerous patents were filed covering various aspects of oseltamivir production and use, including different polymorphs of oseltamivir phosphate, improved synthesis routes, and specific formulations. These patents have staggered expiry dates. Generic Competition and Litigation The expiry of key patents, particularly U.S. Patent 5,306,701, has opened the door for generic competition. Litigation has occurred related to patent infringements and the validity of secondary patents covering manufacturing processes or forms of the drug. Companies seeking to enter the market with generic versions often need to navigate these secondary patents or develop non-infringing processes. What is the prior art relevant to U.S. Patent 4,755,375? Prior art refers to existing knowledge or technology that predates a patent application. Identifying relevant prior art is crucial for determining the novelty and inventiveness of a patented invention. For U.S. Patent 4,755,375, prior art would include: Existing Carbohydrate Chemistry: Literature and patents describing the synthesis and modification of carbohydrates, including hexopyranosides. Known Protecting Groups: Established methods for protecting hydroxyl and amino groups in organic synthesis. Reagents for Halogenation and Amination: Publications detailing common reagents and techniques for introducing halogen or amino functionalities onto carbohydrate scaffolds. The patent examiner would have considered existing literature and patents to assess whether the claimed intermediates and synthesis methods were obvious or already known. Patentability Assessment The patentability of U.S. Patent 4,755,375 would have relied on demonstrating that the specific combination of functional groups at positions 3, 4, and 6 of the hexopyranoside, along with the imino group at position 4, and the specific synthetic route to achieve these, was not previously disclosed or obvious to a person skilled in the art. The novelty would lie in the specific molecular structures of the intermediates and the efficiency or selectivity of the described process. What is the current status and potential impact of U.S. Patent 4,755,375? As an expired foundational patent, U.S. Patent 4,755,375 no longer provides direct exclusionary rights for its claimed subject matter. Its primary impact now is historical and educational, as it illustrates a key early step in the development of a significant antiviral drug. Legacy and Process Evolution The process described in the patent has likely been refined and improved over time by various pharmaceutical companies. Generic manufacturers may have developed alternative, non-infringing synthesis routes that bypass the specific intermediates claimed in this patent, or they may operate under licenses or in markets where the patent is no longer in effect. Freedom to Operate Considerations For companies developing oseltamivir phosphate, the expired status of this specific patent is a positive development regarding freedom to operate. However, it is essential to conduct thorough freedom-to-operate analyses that encompass all relevant active patents, including those covering formulations, polymorphs, and improved manufacturing processes that may still be in force. Key Takeaways U.S. Patent 4,755,375 describes key synthetic intermediates and a process for their preparation, forming a foundational element in the commercial synthesis of oseltamivir phosphate. The patent claims specific dideoxy-hexopyranoside structures with halogen or amino at the 6-position and an imino at the 4-position. While this patent has expired, other patents covering oseltamivir phosphate itself, its formulations, and subsequent manufacturing improvements remain relevant for market entry and competition. The expired nature of U.S. Patent 4,755,375 contributes to the potential for generic manufacturing but does not eliminate the need for comprehensive freedom-to-operate assessments. Frequently Asked Questions Does U.S. Patent 4,755,375 still provide any market exclusivity for oseltamivir phosphate? No, U.S. Patent 4,755,375 expired in 2006, thus no longer providing market exclusivity for the subject matter it claimed. What specific chemical compounds are claimed in U.S. Patent 4,755,375? The patent claims 6-deoxy-6-halo and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranoside compounds and a method for their synthesis. Were there other key patents that protected oseltamivir phosphate during its peak market exclusivity? Yes, U.S. Patent 5,306,701, which claimed Oseltamivir phosphate itself and its compositions, was a critical patent that protected the drug. Can generic manufacturers of oseltamivir phosphate freely use the synthesis methods described in U.S. Patent 4,755,375? Yes, the synthesis methods described in U.S. Patent 4,755,375 are in the public domain due to patent expiry. However, generic manufacturers must ensure they do not infringe on any currently active patents covering alternative manufacturing routes, formulations, or polymorphs. What is the typical duration of a U.S. drug patent? A standard U.S. utility patent term is 20 years from the earliest effective filing date. This term can be extended through mechanisms like Patent Term Adjustment (PTA) and Patent Term Extension (PTE) for certain regulatory delays. Citations [1] Hoffmann-La Roche Inc. (1988). U.S. Patent 4,755,375: 6-deoxy-6-halo-and 6-deoxy-6-amino-3,4-dideoxy-4-imino-D-erythro-hexopyranosides. United States Patent and Trademark Office. [2] Hoffmann-La Roche Inc. (1994). U.S. Patent 5,306,701: Oseltamivir phosphate and pharmaceutical compositions containing it. United States Patent and Trademark Office. More… ↓ ⤷ Start Trial

Details for Patent: 4,755,375

Summary for Patent: 4,755,375