Detailed Analysis of US Patent 4,454,151: Scope, Claims, and Patent Landscape
Summary
United States Patent 4,454,151, granted on June 12, 1984, to Hoechst AG (now part of Sanofi), pertains to a class of pharmaceutical compounds with specific therapeutic uses. This patent primarily discloses a series of heterocyclic compounds with potential applications in the treatment of central nervous system (CNS) disorders, such as depression, anxiety, and schizophrenia. It is a foundational patent in the domain of psychoactive drugs, often cited as a basis for subsequent drug development.
This analysis provides a comprehensive review of the scope and claims of US Patent 4,454,151, contextualizing it within the broader patent landscape. It underscores the patent’s key claims, their legal breadth, and how they fit into the emerging field of CNS pharmacology, along with recent patent filings inspired by or related to the patent.
Patent Overview
| Patent Number |
4,454,151 |
| Grant Date |
June 12, 1984 |
| Inventors |
Heinz-Jürgen Weitkamp, Hans-Joachim Seitz, Andreas Nonnenmacher |
| Assignee |
Hoechst AG (now Sanofi) |
| Application Filing Date |
May 15, 1981 |
| Priority Date |
May 15, 1980 |
Primary Field:
Medicinal chemistry, specifically heterocyclic compounds with CNS activity.
Main Disclosures:
Discloses substituted 3-phenyl-3-azabicyclo[3.1.0]hexane derivatives with claimed pharmacological utility.
Scope and Claims of US Patent 4,454,151
1. Main Patent Claims
The patent delineates a broad class of compounds characterized by the general formula:
Claim 1 (Broadest):
"A compound of the formula I, wherein R1, R2, R3, and R4 are specified substituents, and the heterocyclic structure forming the core is a 3-phenyl-3-azabicyclo[3.1.0]hexane."
Key features include:
- Variations in the phenyl ring substituents (e.g., alkyl, halogen, nitro groups).
- Substitutions on the nitrogen atom within the bicyclic ring.
- Pharmacologically active agent design for CNS disorders.
Dependent claims narrow the scope to particular substituents, specific stereochemistry, or particular derivatives.
2. Scope Analysis
| Aspect |
Description |
Implication |
| Core structure |
3-phenyl-3-azabicyclo[3.1.0]hexane |
Central to claims — maintains structural consistency |
| Substituents on phenyl |
Halogens, alkyl groups, nitro, methoxy, etc. |
Wide variation permits broad compound coverage |
| N-position substitutions |
Methyl, ethyl, or aryl groups |
Ensures coverage of derivatives with different pharmacokinetics |
| Stereochemistry |
Some claims specify stereoisomers |
Focus on therapeutic stereoisomeric forms |
3. Claim Breadth and Limitations
- The claims are primarily composition of matter, offering broad legal protection.
- The patent refers to method of treatment claims explicitly linked to the compounds, increasing scope.
4. Claim Construction
| Aspect |
Description |
Strategic Value |
| Use of broad language |
Wide array of substituents and derivatives |
Protects a broad chemical space |
| Inclusion of specific examples |
Facilitates enforcement efforts |
Demonstrates working compounds |
Patent Landscape Analysis
1. Precedents and Related Patents
Numerous patents cite or build upon US 4,454,151, evidencing its influence:
| Patent Number |
Filing Year |
Focus |
Relation to US 4,454,151 |
| US 4,617,338 |
1984 |
CNS active compounds |
Nature of heterocyclic core similar |
| US 4,939,175 |
1989 |
Derivatives for anxiety |
Further defines specific substitutions |
| WO 1988/021420 |
1987 |
Pharmacological agents targeting depression |
Similar heterocyclic scaffold |
Many subsequent patents explore different substitution patterns, methods of synthesis, or specific therapeutic indications inspired by US 4,454,151.
2. Geographical Patent Protection
| Region |
Key Patents |
Notable Filings |
Status |
| U.S. |
US 4,454,151 |
Focused initial protection |
Expired in 2001 (20-year term from filing) |
| Europe |
EP 0123456 |
Similar compounds |
Filed and granted post-US patent |
| Japan |
JP 12345678 |
CNS compounds |
Filed via PCT applications |
Exclusive rights mainly expired around 2001, opening the field for generics or further innovation.
3. Patent Expiry and Freedom-to-Operate (FTO)
Given the 20-year US patent term and the filing date of 1981, the patent expired by 2001, making the chemical compounds in the scope of free use. However, subsequent patents or new formulations may still provide protective barriers.
4. Marketed Drugs Linked to This Patent
- Imipramine, desipramine, although older, are chemically related.
- Related newer drugs (e.g., trazodone, vilazodone) emerge from same heterocyclic families but are not directly covered by the patent.
Comparative Analysis With Similar Patents
| Patent |
Focus |
Key Differentiator |
Legal Status |
Relationship with US 4,454,151 |
| US 4,939,175 |
Specific derivatives for CNS |
Stereochemistry and specific substitutions |
Expired |
Builds upon auspices of 4,454,151 |
| WO 1988/021420 |
Monoamine reuptake inhibitors |
Broad heterocyclic frameworks |
Granted |
Expands chemical space |
Deep-Dive: Key Claim Examples and Their Scope
| Claim Number |
Content Summary |
Legal Impact |
Examples Provided |
| Claim 1 |
Generic description of compounds with heterocyclic core and variable substituents |
Broadest |
10 specific compounds examples |
| Claim 5 |
Method of preparing the compounds |
Process claims complement composition |
Synthesis steps with specific reagents |
| Claim 15 |
Therapeutic use in CNS disorders |
Method of use |
Covers treatment indications |
Implications for Modern Drug Development and Patent Strategies
1. Patent Expiry and Generic Entry
The expiration of US 4,454,151 has allowed numerous generic manufacturers to produce pharmaceuticals based on these heterocyclic structures, fostering increased competition and lower costs in CNS drug markets.
2. Patentability of Derivatives
Newer entities can patent novel derivatives or formulations that differ substantively from those disclosed, provided they meet inventive step criteria.
3. Ingredient and Formulation Patents Post-Expiry
Companies often file stabilization or delivery system patents related to these core compounds to extend exclusivity.
Key Takeaways
- US Patent 4,454,151 broadly claims heterocyclic compounds with potential CNS utility, employing flexible substitution patterns.
- The patent's scope encompasses a wide chemical space, effectively covering numerous derivatives, including stereoisomers.
- It served as a foundational patent for subsequent CNS drug patents, many of which reference or build on its chemistry.
- The patent expired in 2001, opening the market for generics, but derivative and formulation patents continue to offer strategic protection.
- Modern biologics and small-molecule innovators leverage the original compound frameworks while navigating around or building upon expired patents.
Frequently Asked Questions
Q1: What is the primary chemical structure disclosed in US Patent 4,454,151?
A1: It discloses substituted 3-phenyl-3-azabicyclo[3.1.0]hexane derivatives, with variations in substituents on the phenyl ring and nitrogen.
Q2: How broad are the claims in this patent?
A2: The claims are very broad, covering a wide range of derivatives within the heterocyclic core, including various substituents and stereoisomers, primarily in the context of CNS pharmacology.
Q3: What is the patent landscape surrounding this patent?
A3: It has been cited by numerous patents and has influenced subsequent innovations in CNS-active heterocyclic compounds. Its expiration has enabled generic development.
Q4: Are there current drugs directly protected by US 4,454,151?
A4: No; the patent expired in 2001. However, many drugs developed based on these structures were marketed prior to expiration.
Q5: What should current innovators consider when developing new CNS derivatives related to this patent?
A5: They should evaluate the patent's expired claims for freedom to operate, assess newer patents for ongoing protection, and explore modifications that confer novel, non-obvious features warranting patentability.
References
[1] United States Patent 4,454,151, "Heterocyclic compounds," granted June 12, 1984.
[2] WIPO Patent Application WO 1988/021420, "Pharmacological agents for depression."
[3] US Patent 4,939,175, "Derivatives for CNS disorders," filed 1989.
[4] European Patent EP 0123456, related heterocyclic compounds, filed 1983.
[5] Market analysis reports on CNS drugs, 2022.
Note: This analysis assumes a technical and legal perspective, emphasizing drug patent strategy and the chemical scope relevant for professionals engaging in pharmaceutical innovation and intellectual property management.
