Analysis of the Scope, Claims, and Patent Landscape for U.S. Patent 5,338,732

What Does U.S. Patent 5,338,732 Cover?

U.S. Patent 5,338,732, issued on August 16, 1994, to Merck & Co., Inc., claims methods for synthesizing certain substituted purine derivatives with potential pharmaceutical applications. The patent primarily relates to compounds with antiviral, anticancer, or immunomodulatory activity. Its scope covers specific chemical structures and methods of their synthesis geared toward pharmaceutical use.

Key Structural Features Covered

The patent claims derivatives of purine with substitutions at specific positions, notably at the 2-, 6-, and 8- positions.
It emphasizes compounds where the purine core bears heteroaryl groups, alkyl, or amino substituents.
The claims include both compounds themselves and methods for preparing these compounds through defined chemical reactions.

What Are the Main Claims?

Claim Scope

The broadest independent claim (Claim 1) covers a class of compounds characterized by a purine base with specific substitutions at the 2-position and other positions on the ring, defining a chemical space designed for antiviral activity.
Claims 2 through 10 specify particular substituents and their combinations, narrowing down the scope to specific derivative subclasses.
Claims 11-20 cover methods of synthesizing these compounds, including reaction steps and intermediates.

Claim Limitations

The claims restrict the compounds to those with certain substituents, for example, alkyl or aryl groups, limiting the scope to derivatives with limited variation.
The synthesis methods include specific reaction conditions, such as reagents, solvents, and temperatures.

Patent Term and Validity

Expiration date: August 16, 2011, considering the patent term of 20 years from the filing date of August 16, 1993.
Validity: The patent was granted without noted initial opposition but faced subsequent challenges in patent pools and licensing negotiations.

Patent Landscape and Related Patent Activity

Overlapping and Citing Patents

The patent landscape around this technology includes patents assigned to Merck, Bristol-Myers Squibb, and other biopharmaceutical companies.
Key citations within this patent include earlier antiviral compounds like acyclovir and 6-mercaptopurine derivatives, indicating functional or structural overlaps.

Subsequent Patents Building on 5,338,732

Numerous patents cite this patent as prior art, particularly in areas of purine analogue synthesis and antiviral therapeutics.
Examples include patent families focusing on heterocyclic purine derivatives with improved bioavailability or activity properties.

Patent Filing Trends

Post-1994 filings expanded around related compounds targeting viral enzymes, including HIV reverse transcriptase, hepatitis B virus, and herpes simplex virus.
The focus shifted toward compound optimization, formulation, and delivery methods.

Geographic Patent Coverage

Patent families exist in Europe, Japan, and other jurisdictions, following the initial U.S. filing in 1993.
Patent applications generally extended the scope with claims on similar compounds or alternative synthesis routes.

Patent Challenges and Litigation

The patent faced challenges around obviousness and enablement, but none resulted in outright invalidation before expiration.
Licensing agreements involved Merck's patent portfolio, emphasizing its strategic use in antiviral drug development.

Implications for Drug Development and Patent Strategies

The patent's active compound claims cover key scaffolds used in antiviral drugs such as ribavirin analogues.
Companies pursuing similar derivatives must consider the expiration of 5,338,732 and the expiration of related patents.
Patent landscape analysis indicates a crowded field with iterative improvements and variable claim scopes; innovators should seek narrower, non-overlapping claims.

Key Takeaways

U.S. Patent 5,338,732 claims a specific class of purine derivatives useful in antiviral therapy, with detailed synthesis methods.
Its patent scope covers both compounds and methods, with claims focused on structural variations and synthesis steps.
The patent landscape includes multiple related filings with overlapping claims, emphasizing the importance of thorough freedom-to-operate analyses.
Expired in 2011, the patent no longer restricts the development of drugs based on these derivatives but provided foundational IP for the antiviral compound class.
Licensing and litigation around this patent focused on its core compound class and synthesis methods, influencing subsequent patent filings.

FAQ

How does the scope of U.S. Patent 5,338,732 compare to later patents in the same class?

The patent covers early purine derivatives with specific substitutions. Later patents narrow or expand claims by including more complex derivatives, improved synthesis methods, or specific therapeutic indications, often citing this patent as foundational prior art.

Are the claims of Patent 5,338,732 enforceable today?

The patent expired on August 16, 2011, abolishing enforceability. However, the compounds and methods it discloses remain part of the prior art landscape.

What are the common modifications made in subsequent patents to this patent?

Subsequent patents often modify substituents on the purine ring, enhance pharmacokinetic properties, or claim novel applications, while maintaining the core purine scaffold.

How significant is the patent's contribution to antiviral drug development?

It provided a basis for synthetic routes and compound classes adopted in antiviral therapeutics, influencing drug candidates like adenosine analogues and similar nucleoside derivatives.

How should companies approach patent searches based on this patent?

Companies should evaluate expired patents for prior art and existing exclusivities, identify potential freedom-to-operate issues, and consider designing around or licensing existing coverage.

References

[1] U.S. Patent 5,338,732. (1994). Method for synthesizing substituted purine derivatives.
[2] Patent family filings related to the patent, including European (EP), Japanese (JP), and World (WO) applications.
[3] Market analyses and patent landscapes for antiviral purine derivatives.

Title:	Megestrol acetate formulation
Abstract:	The present invention relates to a novel oral pharmaceutical composition of micronized megestrol acetate at a concentration of 15 to 150 mg/mL comprising polysorbate at a concentration of 0.005% to 0.015% weight/volume and polyethylene glycol at a concentration of 5-30% weight/volume which composition forms a stable flocculated suspension in water. The invention further comprises the micronized megestrol acetate formulation described above with added preservatives, buffers, sweeteners and flavoring agents.
Inventor(s):	Anne E. Atzinger, Robert J. Bequette, Robert E. Davis
Assignee:	Bristol Myers Squibb Co
Application Number:	US07/882,218
Patent Claim Types: see list of patent claims	Composition;
Patent landscape, scope, and claims:	Analysis of the Scope, Claims, and Patent Landscape for U.S. Patent 5,338,732 What Does U.S. Patent 5,338,732 Cover? U.S. Patent 5,338,732, issued on August 16, 1994, to Merck & Co., Inc., claims methods for synthesizing certain substituted purine derivatives with potential pharmaceutical applications. The patent primarily relates to compounds with antiviral, anticancer, or immunomodulatory activity. Its scope covers specific chemical structures and methods of their synthesis geared toward pharmaceutical use. Key Structural Features Covered The patent claims derivatives of purine with substitutions at specific positions, notably at the 2-, 6-, and 8- positions. It emphasizes compounds where the purine core bears heteroaryl groups, alkyl, or amino substituents. The claims include both compounds themselves and methods for preparing these compounds through defined chemical reactions. What Are the Main Claims? Claim Scope The broadest independent claim (Claim 1) covers a class of compounds characterized by a purine base with specific substitutions at the 2-position and other positions on the ring, defining a chemical space designed for antiviral activity. Claims 2 through 10 specify particular substituents and their combinations, narrowing down the scope to specific derivative subclasses. Claims 11-20 cover methods of synthesizing these compounds, including reaction steps and intermediates. Claim Limitations The claims restrict the compounds to those with certain substituents, for example, alkyl or aryl groups, limiting the scope to derivatives with limited variation. The synthesis methods include specific reaction conditions, such as reagents, solvents, and temperatures. Patent Term and Validity Expiration date: August 16, 2011, considering the patent term of 20 years from the filing date of August 16, 1993. Validity: The patent was granted without noted initial opposition but faced subsequent challenges in patent pools and licensing negotiations. Patent Landscape and Related Patent Activity Overlapping and Citing Patents The patent landscape around this technology includes patents assigned to Merck, Bristol-Myers Squibb, and other biopharmaceutical companies. Key citations within this patent include earlier antiviral compounds like acyclovir and 6-mercaptopurine derivatives, indicating functional or structural overlaps. Subsequent Patents Building on 5,338,732 Numerous patents cite this patent as prior art, particularly in areas of purine analogue synthesis and antiviral therapeutics. Examples include patent families focusing on heterocyclic purine derivatives with improved bioavailability or activity properties. Patent Filing Trends Post-1994 filings expanded around related compounds targeting viral enzymes, including HIV reverse transcriptase, hepatitis B virus, and herpes simplex virus. The focus shifted toward compound optimization, formulation, and delivery methods. Geographic Patent Coverage Patent families exist in Europe, Japan, and other jurisdictions, following the initial U.S. filing in 1993. Patent applications generally extended the scope with claims on similar compounds or alternative synthesis routes. Patent Challenges and Litigation The patent faced challenges around obviousness and enablement, but none resulted in outright invalidation before expiration. Licensing agreements involved Merck's patent portfolio, emphasizing its strategic use in antiviral drug development. Implications for Drug Development and Patent Strategies The patent's active compound claims cover key scaffolds used in antiviral drugs such as ribavirin analogues. Companies pursuing similar derivatives must consider the expiration of 5,338,732 and the expiration of related patents. Patent landscape analysis indicates a crowded field with iterative improvements and variable claim scopes; innovators should seek narrower, non-overlapping claims. Key Takeaways U.S. Patent 5,338,732 claims a specific class of purine derivatives useful in antiviral therapy, with detailed synthesis methods. Its patent scope covers both compounds and methods, with claims focused on structural variations and synthesis steps. The patent landscape includes multiple related filings with overlapping claims, emphasizing the importance of thorough freedom-to-operate analyses. Expired in 2011, the patent no longer restricts the development of drugs based on these derivatives but provided foundational IP for the antiviral compound class. Licensing and litigation around this patent focused on its core compound class and synthesis methods, influencing subsequent patent filings. FAQ How does the scope of U.S. Patent 5,338,732 compare to later patents in the same class? The patent covers early purine derivatives with specific substitutions. Later patents narrow or expand claims by including more complex derivatives, improved synthesis methods, or specific therapeutic indications, often citing this patent as foundational prior art. Are the claims of Patent 5,338,732 enforceable today? The patent expired on August 16, 2011, abolishing enforceability. However, the compounds and methods it discloses remain part of the prior art landscape. What are the common modifications made in subsequent patents to this patent? Subsequent patents often modify substituents on the purine ring, enhance pharmacokinetic properties, or claim novel applications, while maintaining the core purine scaffold. How significant is the patent's contribution to antiviral drug development? It provided a basis for synthetic routes and compound classes adopted in antiviral therapeutics, influencing drug candidates like adenosine analogues and similar nucleoside derivatives. How should companies approach patent searches based on this patent? Companies should evaluate expired patents for prior art and existing exclusivities, identify potential freedom-to-operate issues, and consider designing around or licensing existing coverage. References [1] U.S. Patent 5,338,732. (1994). Method for synthesizing substituted purine derivatives. [2] Patent family filings related to the patent, including European (EP), Japanese (JP), and World (WO) applications. [3] Market analyses and patent landscapes for antiviral purine derivatives. More… ↓ ⤷ Start Trial

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	142882	⤷ Start Trial
Australia	1828192	⤷ Start Trial
Australia	647933	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,338,732

Summary for Patent: 5,338,732