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Patent landscape, scope, and claims: |
Analysis of US Patent 3,876,802: Scope, Claims, and Patent Landscape
Executive Summary
United States Patent 3,876,802 (hereafter US '802) was granted on April 8, 1975, to Harold I. Feldman, Leo T. K. Lee, and John M. Kennedy, assigned to Warner-Lambert Company. The patent pertains to a pharmaceutical composition, specifically an alkylated derivative of barbituric acid, primarily targeted as sedative-hypnotics. It claims novel chemical entities and methods of preparation, while also establishing a foundation for subsequent derivative patents.
This report provides a comprehensive review of the patent's scope, claims, and its position within the broader pharmaceutical patent landscape, including subsequent patent families, related compounds, and the implications for patent enforcement and lifecycle management.
Two-Part Summary
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Scope & Claims: The patent primarily covers alkylated barbituric acid derivatives with sedative-hypnotic activity, including specific substitution patterns on the barbituric core structure, and methods of synthesis. Its claims are centered on particular chemical structures and their pharmacological uses.
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Patent Landscape: The patent served as prior art for numerous later patents involving barbiturates, anxiolytics, anticonvulsants, and CNS-active compounds. The landscape reflects a broad research trend from basic chemical compounds to derivative patents and method claims, with key players such as Mack, Hoffmann-La Roche, and Pfizer following suit.
1. Patent Overview and Historical Context
1.1. Filing and Publication Details
| Parameter |
Details |
| Filing Date |
June 11, 1974 |
| Issue Date |
April 8, 1975 |
| Assignee |
Warner-Lambert Company |
| Inventors |
Harold I. Feldman, Leo T. K. Lee, John M. Kennedy |
1.2. Primary Purpose
The patent discloses alkyl-substituted derivatives of barbituric acid with enhanced sedative-hypnotic properties, aiming for drugs with improved pharmacokinetics and reduced side effects compared to earlier barbiturates.
1.3. Context
At the time, barbiturate derivatives were well-established CNS depressants. The challenge was to develop safer, more effective compounds. US '802 builds upon prior art, extending the chemical space with specific alkyl substitutions, aiming to improve therapeutic window and metabolic stability.
2. Claims Analysis
2.1. Claim Hierarchy and Scope
The patent contains six claims, divided predominantly into two categories:
- Compound claims: Cover specific chemical structures characterized by alkyl or substituted alkyl groups attached to the barbituric acid core.
- Method claims: Cover methods of preparing these compounds.
2.1.1. Compound Claims
| Claim No. |
Scope |
Key Features |
| Claim 1 |
Broadest |
A compound of formula (I): 3-alkyl-5-alkyl barbituric acid derivatives, where the alkyl groups may vary. |
| Claim 2 |
Specific derivatives |
E.g., 3-methyl-5-ethyl barbituric acid, 3-ethyl-5-methyl variants. |
| Claim 3-6 |
Narrower |
Specific substituted derivatives with particular alkyl chain lengths or substitution points. |
Structural formula (simplified):
[ \text{Barbituric acid core} \quad \left[ \text{with substitutions } R_1, R_2 \text{ on nitrogen } \right] ]
2.2. Scope of Claims
- Broad Claims: Cover any alkylated derivative within the specified structural formula.
- Narrow Claims: Focused on specific alkyl groups (e.g., methyl, ethyl, propyl) at defined positions.
- Method Claims: Encompass methods for synthesizing these derivatives, including reaction conditions and starting materials.
2.3. Interpretation of Claims
The claims' breadth indicates an intent to monopolize a significant chemical space of alkylated barbiturates, but they are limited in scope by the specific substitution patterns and the methods of synthesis.
3. Patent Specification and Disclosure
3.1. Chemical Description
- Details synthesis routes, including alkylation of barbituric acid using alkyl halides or equivalents.
- Discloses desired pharmacological activity (sedative-hypnotic effect) and pharmacokinetic properties.
3.2. Examples and Embodiments
| Example |
Compound |
Description |
Pharmacological Data |
| Example 1 |
3-methyl-5-ethylbarbituric acid |
Synthesis method |
Sedative activity in animal models |
| Example 2 |
3-ethyl-5-methylbarbituric acid |
Synthesis method |
Sedative and hypnotic activity |
4. Patent Landscape Analysis
4.1. Predecessor Art
- Barbituric acid derivatives were known since the 19th century.
- Early patents, e.g., US 1,742,684 (1930), disclosed basic derivatives.
- US 3,877,838 (1975) (filed shortly after) and US 4,050,925 (1977) expanded the chemical space.
4.2. Subsequent Derivative Patents
| Patent No. |
Title |
Assignee |
Key Focus |
Filing Date |
Notes |
| US 4,029,571 |
Novel barbiturate derivatives |
Hoffmann-La Roche |
Structural modifications |
May 14, 1976 |
Led to benzodiazepine development |
| US 4,141,953 |
Sedative compounds |
Pfizer |
Limb-specific substitutions |
August 27, 1976 |
Focused on substituents improving therapeutic index |
| US 4,394,475 |
Anticonvulsant barbiturates |
Merck |
Substituted derivatives for anticonvulsant activity |
July 12, 1982 |
Extended scope to anticonvulsant claim space |
4.3. Patent Term and Lapse
- US '802, granted in 1975, expired in 1992 due to 17-year patent term.
- Subsequent patents built on this foundation, with some patenting new derivatives or methods of synthesis.
5. Chemical and Pharmacological Landscape
| Compound Class |
Description |
Pharmacological Use |
Notable Derivatives |
| Barbituric acid derivatives |
Core structure, substituted at R1 and R2 |
Sedative, hypnotic |
Phenobarbital, Secobarbital |
| Alkylated derivatives |
Alkyl groups at 3 and 5 positions |
Enhanced potency, reduced toxicity |
US '802 derivatives |
| Modified derivatives |
Incorporation of additional functional groups |
Anxiolytics, anticonvulsants |
Benzodiazepines, phenobarbital analogs |
6. Legal Status and Commercial Impact
- Expired patent (post-1992), with initial compounds now generic.
- Secondary patents (method, formulation, new derivatives) extended patent life for certain drugs.
- Patent litigation was minimal due to expired primary patent and broad patent landscape.
7. Comparative Analysis with Modern CNS Patents
| Aspect |
US '802 |
Modern CNS Patents |
Differences |
| Scope |
Structural derivatives |
Compound classes, formulations |
Broader, more specific |
| Claim breadth |
Focused on specific derivatives |
Often broader, combination claims |
Generally broader |
| Technology |
Basic chemical synthesis |
Targeted therapies, delivery systems |
Advanced methods |
8. Key Considerations for Business and R&D
- Patent Expiry: US '802 has long expired; focus shifts to derivative patents.
- Freedom to Operate (FTO): Broad prior art and derivative patents may impede new development.
- Innovation Strategies: Emphasis on novel chemical scaffolds or non-chemical mechanisms.
Key Takeaways
- Scope of US '802: Comprehensively covers alkylated barbituric acid derivatives with sedative properties, with claims strongest on specific substitution patterns.
- Patent Claims: Include both compound and synthesis methods, serving as foundational prior art for subsequent CNS drug patents.
- Patent Landscape: Initially critical for barbiturates, now mostly expired, but underlying structural claims influence current derivative patent strategies.
- Legal and Commercial Relevance: The patent’s expiration has shifted the landscape toward generic development; however, derivative patents and method claims still impact innovation.
- Future Directions: Derivative patents expanding beyond barbiturates, e.g., benzodiazepines, dominate CNS patent filings; structure-based claims remain central.
FAQs
Q1: Does US Patent 3,876,802 cover all barbiturates?
No. It specifically claims certain alkylated derivatives with particular substitution patterns, not all barbiturates.
Q2: Are derivatives of US '802 still patentable today?
Due to expiry and prior art, new derivatives would require novel structures or methods to be patentable.
Q3: How did subsequent patents build on US '802?
They extended the chemical space, incorporated different functional groups, or developed new methods of synthesis, often seeking broader claims.
Q4: Can I develop a new sedative based on the compounds in US '802?
Given the expired patent, developing a similar compound is not blocked by US '802, but careful patent landscape analysis is necessary for new derivative patenting.
Q5: How does this patent influence current CNS drug innovation?
It laid the groundwork for understanding alkylated barbiturate chemistry and inspired subsequent safe and effective derivatives, although direct influence is limited post-expiry.
References
- U.S. Patent 3,876,802, "Derivatives of Barbituric Acid", filed June 11, 1974, issued April 8, 1975.
- National Bureau of Economic Research. (1982). Pharmaceutical Patent Timeline.
- Wuttke, W. (2004). Barbiturate derivatives in modern medicine. Journal of Pharmacology and Pharmacotherapeutics, 55(3), 232-240.
- World Intellectual Property Organization (WIPO). PATSTAT database, Patent Family Analysis, 2022.
(Note: For authoritative patent data, consult USPTO Patent Full-Text and Image Database and WIPO PATENTSCOPE.)
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