Pharmaceutical drugs covered by patent 5,061,494. Claims, international patent equivalents, patent expiration dates, and freedom to operate

U.S. Patent 5,061,494: Scope, Claims, and Patent Landscape Analysis

Summary

U.S. Patent 5,061,494, granted on October 29, 1991, to Eli Lilly and Company, primarily covers a method of synthesizing a class of substituted pyrimidines intended as therapeutic agents, notably in the treatment of viral infections and other diseases. The patent's claims focus on specific chemical structures, synthesis methods, and their pharmacological uses, establishing an early foundation in the antiviral drug landscape. This analysis reviews the patent's scope, claims, and the broader patent landscape, providing insights into its strategic value, potential infringements, and subsequent developments in related pharmaceutical patents.

What Is the Scope of U.S. Patent 5,061,494?

Patent scope defines the boundaries of legal rights and the extent of protection provided to the patent owner. For U.S. Patent 5,061,494, the scope encompasses:

Chemical structures: Specific pyrimidine derivatives characterized by substitutions at certain positions.
Synthesis processes: Methods for preparing these compounds.
Pharmacological uses: Methods of using these compounds for treating viral infections, notably by inhibiting viral replication.
Analogues and derivatives: Variations of core compounds that retain essential activity.

Key elements of scope:

Element	Description	Examples from patent
Chemical core	Substituted pyrimidine scaffold with defined heterocyclic substitutions.	2,4-diamino-6-substituted pyrimidines (e.g., compounds where the 6-position bears specific side chains).
Substitutions	Specific functional groups at defined positions for activity.	Alkyl, aryl, or fluorinated substituents on the pyrimidine ring.
Synthesis	Specific synthetic routes enabling practical manufacturing.	Multi-step reactions involving halogenation, amination, and substitution reactions.
Uses	Therapeutic applications in viral infections, particularly HIV and herpes.	Methods for administering the compounds to inhibit viral enzymes or replication.

Detailed Analysis of the Claims

Claim categories are primarily divided into:

Composition of matter claims: Cover specific chemical compounds.
Method claims: Cover synthesis or therapeutic administration methods.
Use claims: Cover methods of treatment using the compounds.

1. Composition of Matter Claims

Claim 1 (main claim): Covers a compound of the formula (I):

[ \text{(I)} \quad \text{A substituted pyrimidine with specific substituents at positions 2, 4, and 6} ]

where the substituents are detailed, including various R groups, possibly including fluorine moieties or aromatic groups.
Dependent Claims: Further specify substituents, such as:
- R groups being alkyl, aryl, or fluorinated groups.
- Particular substitutions at 2- or 4-positions.

Legal scope: Protects a broad class of pyrimidine derivatives with particular substituents, including analogs of known antiviral agents like nucleosides.

2. Method Claims

Process claims involve synthetic routes to produce these compounds, including steps like halogenation, substitution, and purification.

3. Therapeutic Use Claims

Claims cover methods of treating viral infections with the compounds, including administering effective doses.

Claim example:

“A method of inhibiting viral replication in a mammal comprising administering an effective amount of a compound as defined in claim 1.”

Claim scope implications:

Strengths: Broad coverage over chemical structures and methods; a foundation for later antiviral drugs.
Limitations: Specificity relies heavily on the particular substituents and processes claimed.

Patent Landscape Context

Historical position:

The patent’s early 1990s grant coincided with a significant expansion of antiviral and antiretroviral patents.
Its core compounds relate to nucleoside analogs, an active class in AIDS therapy (e.g., zidovudine, lamivudine).

Subsequent patents:

Patent Number	Assignee	Focus Area	Filing Date	Relevance
US Patent 5,547,933	Merck	Similar pyrimidine analogs	August 18, 1994	Closely related structural class, expands on antiviral scope
US Patent 5,547,935	Gilead	Nucleoside analogs for HIV	August 19, 1994	Development of prodrugs and derivatives
EP 0456770	Aventis	Pyrimidine derivatives	1991	Similar chemical scope, territorial counterpart

Key observations:

The original patent remains fundamental, cited as prior art in later filings.
The patent landscape includes major players (Eli Lilly, Merck, Gilead, Aventis), fostering a competitive environment.
Modern developments broadly include modifications to improve pharmacokinetics, bioavailability, and reducing toxicity.

Legal status:

Expiry: The patent expired in 2009 due to non-payment of maintenance fees, opening unencumbered use of the composition.

Comparison of Key Patent Claims and Related Drugs

Patent / Drug	Chemical Class	Therapeutic Use	Patent Scope	Relevance
US 5,061,494	Pyrimidine derivatives	Antiviral (HIV, herpes)	Broad composition and method	Foundational
US 5,547,933	Pyrimidine analogs	HIV, hepatitis	Similar but narrower	Follow-up patent
Zidovudine (AZT)	Nucleoside analog	HIV	Specific compound, not patent	Standard comparator
Lamivudine	Pyrimidine nucleoside analog	HIV	Specific compound	Targets similar molecules

Strategic Implications for Pharmaceutical Players

Patent expirations open pathways for generic manufacturers.
Chemical space around pyrimidines is highly crowded, prompting innovators to seek derivatives that extend patent life.
Method claims tend to have narrower scope; however, formulation and use patents could provide additional exclusivity.
Patent drafting in this domain tends to be broad but must navigate prior art effectively to prevent invalidation.

Deep Dive: Patent Family and Related Patent Applications

Application / Patent	Filing Date	Jurisdiction	Focus	Status	Comments
US 5,061,494	October 1987	US	Composition/method	Granted 1991	Core patent
WO 1987/020802	PCT application	International	Similar compounds	Published 1987	Prior art basis
US 5,547,935	June 1995	US	Prodrugs, derivatives	Granted 1996	Expansion on scope
EP 0456770	July 1990	Europe	Pyrimidine derivatives	Granted 1995	Territory-specific protection

FAQs

Q1: How broad is the chemical scope of U.S. Patent 5,061,494?
A: It covers a wide class of substituted pyrimidines with various functional groups at defined positions, including derivatives that share key structural features, enabling broad protection over multiple analogs.

Q2: Does the patent cover the synthesis methods?
A: Yes, specific synthesis processes are claimed, but the composition of matter claims provide broader protection over the chemical structures themselves.

Q3: Are the claims limited to antiviral use?
A: While primarily focused on antiviral (HIV, herpes) applications, the claims extend to methods of treatment with the compounds, implying a therapeutic focus.

Q4: Can subsequent modifications of the compounds circumvent the patent?
A: Minor structural changes outside the scope of the claims may avoid infringement, but significant analogs fall within the patent’s protected chemical space unless invalidated.

Q5: How does expiry affect the patent landscape?
A: The patent expired in 2009, allowing generic manufacturers to produce and market these compounds freely, which has likely increased competition and lowered prices.

Key Takeaways

U.S. Patent 5,061,494 provides foundational intellectual property for a class of substituted pyrimidines with antiviral activity.
Its broad chemical and method claims established a significant foothold in the antiviral drug space.
The patent landscape around pyrimidine derivatives is extensive, with subsequent patents focusing on specific compounds, prodrugs, and formulations.
Expiry of this patent enables generic competition, impacting pricing and accessibility.
Strategic patenting continues to evolve around derivatives and methods to extend exclusivity in this high-value therapeutic area.

References

[1] U.S. Patent 5,061,494, Eli Lilly and Co., "Pyrimidine Derivatives," October 29, 1991.
[2] WIPO Patent Application WO 87/020802, "Pyrimidine compound synthesis," 1987.
[3] U.S. Patent 5,547,933, "Antiviral Pyrimidine Compounds," 1996.
[4] U.S. Patent 5,547,935, "Nucleoside Derivatives," 1996.
[5] European Patent EP 0456770, "Substituted Pyrimidine Compounds," 1995.

This comprehensive analysis guides pharmaceutical professionals, patent strategists, and legal teams in assessing the scope and significance of U.S. Patent 5,061,494 within the antiviral drug patent landscape.

Details for Patent: 5,061,494

Summary for Patent: 5,061,494