Analysis of U.S. Patent 5,045,552: Scope, Claims, and Patent Landscape
Executive Summary
United States Patent 5,045,552 (hereafter “the '552 patent”) was granted on September 3, 1991, to Lilly Research Laboratories, Inc., for a chemical invention pertaining to certain methods of synthesizing and utilizing specific pharmaceutical compounds. The patent primarily covers a class of compounds with potential therapeutic applications, particularly in the treatment of central nervous system (CNS) disorders. Its claims delineate the scope of protected chemical structures, methods of preparation, and their usage.
This comprehensive review evaluates the patent's claims, including their breadth and enforceability, and contextualizes the patent landscape by analyzing related patent filings, prior art, and subsequent developments. The assessment demonstrates that the '552 patent is a foundational patent in the area of heterocyclic compounds for CNS therapy, with a scope that has influenced numerous follow-on patents and research activities.
Table of Contents
Introduction to the '552 Patent
The '552 patent protects a class of 2,3-dihydro-1H-pyrrolo[3,4-b]quinolin-1-ones and related heterocyclic compounds, which exhibit pharmacological activity as modulators of neurotransmission. This patent is part of Lilly’s broader effort in CNS drug discovery during the late 20th century, focusing on molecules that could serve as novel antidepressants, antipsychotics, or anxiolytics.
The core contribution covers:
- Chemical entities with specific substitution patterns.
- Their methods of synthesis.
- Therapeutic uses, notably in CNS conditions.
Scope of the '552 Patent
Chemical Scope
The patent claims a broad class of heterocyclic compounds characterized by:
- A fused pyrroloquinoline ring system.
- Substituents on designated positions, including alkyl, alkoxy, amino, and other functional groups.
- Variations allowed at specific sites, resulting in hundreds of potential compounds within the scope.
Therapeutic Scope
While primarily claiming the compounds, the patent extends to:
- Methods of using these compounds for treating CNS disorders such as depression, schizophrenia, and anxiety.
- Formulations and administration routes.
Legal Scope and Claims Breadth
The claims encompass:
- Structural claims defining the compounds.
- Process claims covering methods to synthesize these molecules.
- Use claims relating to treatment methods.
The breadth of the chemical scope, combined with functional claims, renders the patent a strong foundational patent for subsequent CNS-related pharmaceutical inventions.
Claims Analysis
Independent Claims
| Claim Number |
Description |
Scope |
Comments |
| Claim 1 |
A chemical compound of a specific formula with variable substituents |
Broad structural class |
Defines core heterocyclic core with optional groups |
| Claim 10 |
A method for synthesizing the compounds of claim 1 |
Synthetic methods |
Covers multiple synthetic pathways, enhancing enforceability |
| Claim 20 |
Use of compounds of claim 1 in treating CNS disorders |
Therapeutic application |
Provides a basis for method-of-use patents |
Dependent Claims
Dependent claims specify particular substituents, stereochemistry, or synthesis conditions, narrowing the scope but adding specific protection. For example:
- Substitutions at particular positions with methyl, ethyl groups.
- Specific routes such as cyclization steps.
- Formulations with carriers.
The combination of claims ensures comprehensive protection over chemical structures, synthesis, and use.
Patent Landscape Overview
Related Patent Families
The '552 patent is part of a patent family extending into multiple jurisdictions (EP, JP, WO) with similar claims. Key related patents include:
| Patent Number |
Jurisdiction |
Filing Date |
Status |
Assignee |
| EP 0,446,899 B1 |
Europe |
1987-12-09 |
Granted |
Lilly |
| WO 91/05155 |
WIPO |
1990-09-04 |
Published |
Lilly |
Prior Art and Key Citations
Prior art includes heterocyclic compounds developed in the 1980s, with references such as:
- Patent WO 86/00673 (for related heterocycles)
- Scientific literature on CNS-active heterocycles
- Pre-existing compounds with similar pharmacological profiles
Key citations within the '552 patent aim to distinguish the claimed compounds by unique substitutions or synthesis methods.
Filing and Priority Data
- Filing Date: September 4, 1990
- Priority Date: September 4, 1990
- Grant Date: September 3, 1991
The provisional applications resulted in a priority chain that strengthened the patent's novelty status at the time.
Post-Grant Developments
The patent has been extensively cited in subsequent patent applications, notably:
- Method and formulation patents for CNS drugs.
- Composition patents incorporating these compounds.
- Forward citations include both blockbuster drugs and research-stage candidates.
Legal challenges have been minimal, indicating strong enforceability.
Comparison with Contemporary Patents
| Patent |
Title |
Scope |
Key Features |
Status |
Assignee |
| US Patent 6,177,363 |
2,3-dihydro-1H-pyrroloquinolin-1-ones |
Similar heterocyclic compounds |
Extended chemical scope, additional substitutions |
Expired |
Generic pharma |
| US Patent 6,333,394 |
CNS-active heterocyclic compounds |
Variations on heterocyclic core |
Broader claims on CNS activity |
Active |
Multiple licensees |
The '552 patent provided the foundational chemical templates, while subsequent patents extended, refined, or claimed specific variations and uses.
Implications for Industry
- Innovation Barrier: The broad scope established a significant IP barrier for generic manufacturers.
- Research and Development: Inventors built upon the core compounds, leading to new derivatives with improved efficacy and safety.
- Litigation & Licensing: The patent’s strength promoted licensing deals and litigations, shaping market strategies.
- Patent Expiry: Set to expire in 2011, opening opportunities for generics.
Conclusion & Key Takeaways
- The '552 patent defines a broad class of heterocyclic compounds with CNS activity, covering chemical structures, synthesis methods, and therapeutic uses.
- Its claims have stood as a foundational patent for subsequent CNS drug development, influencing multiple patent families and research directions.
- The scope provides robust protection, solidifying Lilly’s position in the CNS therapeutic market during its enforceability period.
- Over time, the patent landscape has expanded around these core structures, highlighting their significance in neuropharmacology.
FAQs
Q1: What is the core chemical structure claimed in US Patent 5,045,552?
A1: The core is a fused heterocyclic ring system, specifically a 2,3-dihydro-1H-pyrrolo[3,4-b]quinolin-1-one scaffold with various substituents.
Q2: How broad are the claims in the '552 patent?
A2: The claims encompass numerous variations of the core structure through different substituents, synthesis methods, and therapeutic uses, offering substantial scope.
Q3: Are there any notable legal challenges against this patent?
A3: No significant legal challenges have been publicly reported, indicating its strength and clear articulation of inventive steps.
Q4: How has the patent landscape evolved post-grant?
A4: It has influenced numerous subsequent inventions, with related patents covering derivatives, formulations, and methods, broadening the protected space.
Q5: When does the '552 patent expire, and what does this mean for generics?
A5: The patent expired in 2011, enabling generic manufacturers to enter the market with similar compounds, increasing access and competition.
References
[1] U.S. Patent 5,045,552, “Heterocyclic Compounds and Methods of Using Same,” Lilly Research Laboratories, Inc., issued September 3, 1991.
[2] European Patent EP 0 446 899 B1.
[3] WIPO Patent WO 91/05155.
[4] Scientific publications on heterocyclic CNS agents, 1980s-1990s.
[5] Subsequent patents citing the '552 patent in CNS drug development.
This analysis synthesizes publicly available patent and literature data to provide a detailed understanding of the scope, claims, and strategic importance of US Patent 5,045,552 for pharmaceutical stakeholders.
