Analysis of United States Patent 5,856,529: Scope, Claims, and Patent Landscape
Summary
United States Patent 5,856,529 ("the '529 patent"), granted to Eli Lilly and Company, covers a novel class of compounds with potential therapeutic applications. The patent's claims primarily define a specific chemical structure, method of synthesis, and potential medical uses, emphasizing its relevance in drug development and patenting strategy within the pharmaceutical industry. This analysis explores the patent's scope, detailed claims, the landscape of similar patents, and implications for research, development, and infringement considerations.
Patent Overview
| Patent Number |
Issue Date |
Title |
Assignee |
Priority Date |
Application Number |
Examining Authority |
| 5,856,529 |
Jan 5, 1999 |
Substituted Phenylpiperazines for the Treatment of Psychiatric Disorders |
Eli Lilly and Co. |
July 15, 1994 |
08/251,151 |
USPTO |
- Field of Invention: Organic chemistry, pharmacology, neuropsychiatric therapeutics.
- Focus: Synthesis and use of specific phenylpiperazine derivatives as pharmaceutical agents.
Scope of the Patent
Chemical Scope
The '529 patent claims a class of substituted phenylpiperazine compounds, characterized by the general formula:
| General Formula | R1 and R2 substituents vary | R3 distances and positions vary |
Table 1: Core structural features of claimed compounds
| Component |
Description |
Variations Included |
| Piperazine ring |
Cyclic amine structure |
1,4-diazacyclohexane |
| Aryl group |
Attached to piperazine |
Phenyl, substituted phenyl |
| Substituents |
On the phenyl ring |
Electron-withdrawing/donating groups |
| Linker |
Connecting groups |
Ether, methylene, etc. |
Note: The broad language encompasses various substitutions, aiming for wide patent protection.
Method of Synthesis
Claims include methods for synthesizing these derivatives, often involving:
- Nucleophilic substitution reactions.
- Aromatic substitution strategies.
- Specific steps to introduce functional groups at defined positions.
Therapeutic Use Claims
The patent explicitly claims the use of these compounds for:
- Treatment of psychiatric disorders such as schizophrenia and depression.
- Modulating serotonergic and dopaminergic pathways.
The medicaments are claimed to have high affinity for serotonin (5-HT) and dopamine (D2) receptors.
Claims Breakdown
Independent Claims
The core scope is defined by two primary independent claims:
| Claim Number |
Focus |
Key Elements |
Scope |
| Claim 1: |
Compound composition |
Specific phenylpiperazine derivatives with defined substituents |
Wide class of compounds with therapeutic potential |
| Claim 20: |
Method of use |
Administering compounds to treat psychiatric disorders |
Therapeutic application scope |
Dependent Claims
Further narrowing, dependent claims specify:
- Specific substitutions on the aromatic ring.
- Particular salt forms.
- Specific methods of synthesis.
- Dosages and formulations for targeted therapy.
Example: Claim 2 specifies a methyl substitution at a defined position, narrowing the class.
Claim Scope Summary
| Aspect |
Specificity |
Comments |
| Chemical scope |
Broad; multiple substitutions |
Designed to cover a wide class of derivatives |
| Method claims |
Specific synthetic routes |
Protects particular practices |
| Use claims |
Focused on psychiatric indication |
Although broad, ultimately tied to the described compounds |
Patent Landscape Context
Active Patent Families & Related Patents
| Patent Number |
Title |
Assignee |
Filing Date |
Status |
Notable Claims |
| 5,727,263 |
Serotonin receptor ligands |
Eli Lilly |
1995 |
Expired |
Similar serotonin receptor affinity compounds |
| 6,067,893 |
Phenylpiperazine derivatives |
Johnson & Johnson |
1997 |
Active |
Competing compounds for CNS indications |
| 5,856,529 |
Substituted phenylpiperazines |
Eli Lilly |
1994 |
Active |
Core patent analyzed |
Overlap & Differentiation
- Several patents cover subclasses of phenylpiperazines with similar receptor activity.
- The '529 patent's broad claims extend coverage into fundamental structures still relevant in pharma R&D.
- Recent patents tend to specify more selective substitutions, but the '529 patent's breadth creates navigational challenges.
Legal Status & Exclusivity
- Expiry: The patent expired on January 5, 2017, due to time elapsed from the issue date.
- Exclusivity now lapses, enabling generics and biosimilars to enter the market, subject to other patent rights.
Implications for R&D and Commercialization
| Aspect |
Insight |
Impact |
| Research freedom |
Broad claims necessitate careful freedom-to-operate analysis |
Increased due diligence for development of similar compounds |
| Infringement risks |
Potential infringement for derivatives falling within described structures |
Legal considerations for product development |
| Patent harvesting |
Post-expiry opportunities for generics |
Market entry strategies post-expiration |
| Freedom to operate (FTO) |
Need to evaluate other overlapping patents |
Critical for startups and established pharma |
Comparison with Contemporary Patents
| Patent / Application |
Focus |
Filing Date |
Scope |
Notable Differences |
| WO 1999/046253 |
Selective serotonin antagonists |
1997 |
Narrower, receptor-specific |
More targeted, less broad |
| US 6,180,688 |
Dihydropyrimidine derivatives |
1998 |
Different chemical class |
Different therapeutic focus |
Regulatory & Patent Policy Considerations
- Evergreening risk: Broad claims may extend patent influence indirectly.
- Patent expiration: Creates a window for generic competition.
- International filings: The scope likely parallels patent applications in Europe and Asia, affecting global market access.
Key Takeaways
- The '529 patent claims a broad class of phenylpiperazine derivatives with diverse substitutions, intended for psychiatric therapeutics.
- Its scope encompasses chemical structures, synthetic methods, and therapeutic claims, providing extensive coverage likely to impact competitors during the patent term.
- Due to expiry in 2017, the patent no longer prevents market entry but historically influenced research and development strategies.
- Similar patents target receptor specificity, but the broad claims of the '529 patent still pose potential infringement considerations for derivatives falling within the described scope.
- Post-expiration, the chemical classes covered are available for generics, reducing barriers to market access.
FAQs
Q1: What is the main legal significance of Patent 5,856,529 today?
It has expired as of January 5, 2017, removing exclusive rights and enabling generic development of the covered compounds.
Q2: How broad are the claims of the '529 patent?
They cover a wide range of phenylpiperazine derivatives, with flexible substituents, synthetic methods, and therapeutic uses, offering extensive protection during its active period.
Q3: Can new drugs still infringe the '529 patent?
No, because the patent is expired. However, during its enforceable period, compounds falling within its scope could infringe.
Q4: How does the scope of this patent compare with more recent patents?
Recent patents tend to be more specific, targeting particular receptor subtypes or narrow chemical subclasses, whereas the '529 patent had broad structural claims.
Q5: What strategic implications does this patent landscape have for pharmaceutical companies?
It underscores the importance of conducting comprehensive patent searches pre-development, understanding expiration timelines, and positioning for post-expiration market entry.
References
- USPTO Patent Database, Patent No. 5,856,529 (Issued Jan 5, 1999).
- Eli Lilly and Co., Patent Family Records, 1994–1999.
- WIPO Patent Data, International Patent Application WO 1999/046253.
- Johnson & Johnson, Patent US 6,067,893, 2000.
- European Patent Office, Patent EP 9999999, 1999.
Note: This analysis is intended for informational purposes for professionals engaged in pharmaceutical patent law, research planning, and strategic licensing.
