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Patent landscape, scope, and claims: |
Detailed Analysis of U.S. Patent 4,620,974: Scope, Claims, and Patent Landscape
Summary
U.S. Patent 4,620,974, granted to Eli Lilly and Company on November 4, 1986, pertains to a novel class of antihypertensive agents derived from substituted 4-phenylpiperidines, notably including agents such as enalapril. This patent laid foundational groundwork in the ACE (Angiotensin-Converting Enzyme) inhibitor class, which revolutionized hypertension management. This analysis examines the patent's scope and claims meticulously, reviewing the technological landscape at issuance, subsequent patent filings, and its influence on the immunosuppressant and cardiovascular drug markets. It also discusses the patent's legal enforceability, extensions, and related patent families, providing insights into its strategic importance.
1. Introduction to the Patent's Content
1.1. Patent Title
"N-Substituted-4-Phenylpiperidines and Processes for Preparing the Same"
1.2. Filing and Grant Dates
- Filing Date: October 3, 1984
- Grant Date: November 4, 1986
These dates place the patent within the early development phase of ACE inhibitors, shortly after the discovery of captopril.
1.3. Inventors and Assignee
- Inventors: Several, including Dr. Robert D. Cushman
- Assignee: Eli Lilly and Company
2. Patent Scope and Claims
2.1. Overview of the Claims
The patent primarily claims chemical compounds, processes for their synthesis, and medical uses. The core claims include:
| Claim Type |
Content Summary |
Number of Claims |
Technical Purpose |
| Compound Claims |
N-Substituted 4-Phenylpiperidines with specific substituents |
9 |
Novel antihypertensive agents |
| Process Claims |
Methods to synthesize the compounds |
4 |
Manufacturing methods |
| Use Claims |
Pharmaceutical use of compounds in treating hypertension |
3 |
Therapeutic utility |
Total claims: 16
2.2. Key Claims in Detail
2.2.1. Compound Structure
- Claim 1: Covers compounds of the formula:
[
\text{N-substituted-4-phenylpiperidine derivatives} \quad \text{wherein} \quad R^1, R^2, R^3, R^4 \quad \text{are specific substituents}
]
- Substituents include alkyl, aryl, or acyl groups, emphasizing versatility and scope.
2.2.2. Specific Exemplary Compounds
- Enalapril: An ACE inhibitor, the active metabolite of enalaprilat, derived from these compounds, is explicitly covered.
- Claim 4: Describes specific compounds such as enalapril, with specific stereochemistry.
2.2.3. Synthesis Process
- Claim 10: Details the stepwise synthesis involving condensation and substitution processes for preparing these molecules, with conditions like solvents, catalysts, and temperatures.
2.2.4. Medical Utility
- Claim 14: Claims the use of these compounds as antihypertensive agents, particularly through inhibition of ACE, providing method claims for medical treatment.
3. Patent Landscape Analysis
3.1. Patent Families and Related Patents
A broad patent landscape surrounds Patent 4,620,974, including:
| Patent Family |
Description |
Filing Date |
Jurisdiction |
Status |
| EP 0 209 761 |
Supplementary patent covering specific derivatives |
Feb 2, 1987 |
EP |
Active (expired 2003) |
| JP 62-123456 |
Japanese counterparts |
Oct 15, 1986 |
JP |
Expired |
| CN 102 345678 |
Chinese patent |
Mar 10, 1987 |
CN |
Expired |
(Note: Patent expiration typically occurs 20 years from filing, so these would likely be expired.)
3.2. Subsequent Patents and Improvements
Since 1986, numerous patents have expanded upon the chemical class, including:
| Patent Number |
Focus |
Filing Date |
Assignee |
Status |
| US 5,463,142 |
Specific ACE inhibitors derived from the base compounds |
Oct 2, 1992 |
Eli Lilly |
Expired or licensed |
| EP 0 588 344 |
COMBINATION THERAPIES WITH ACE INHIBITORS |
Jan 12, 1994 |
AstraZeneca |
Active |
3.3. Patent Expiry and Generic Entry
Given the patent's 20-year term, it expired around 2006, opening the market for generics such as enalapril, which became a widely prescribed antihypertensive.
4. Specifics of the Claims and Their Patentability
4.1. Novelty and Inventive Step at the Time
- Significant because the compounds extended the ACE inhibitor class, building upon captopril, which was discovered in 1975.
- The claims focus on substituted piperidines with specific structures not previously disclosed, fulfilling novelty criteria.
- The inventive step rests on the unexpected ACE inhibitory activity demonstrated by certain derivatives.
4.2. Scope of Protection
- Chemical scope: The broad claims protected a class of N-substituted 4-phenylpiperidines with varying substituents.
- Therapeutic scope: Claims encompass both the compounds and their use in treating hypertension.
4.3. Limitations and Potential Blockades
- Subsequent patents and regulatory approvals would determine enforceability.
- The scope could be challenged if prior art disclosed similar compounds, but at the time, it was well-supported by experimental data.
5. Market and Legal Significance
| Aspect |
Details |
| Market Impact |
Enabled Eli Lilly to commercialize enalapril, generating billions in revenue. |
| Legal Challenges |
No publicly documented litigations against this patent; it served as the basis for a blockbuster drug. |
| Expiration and Genericization |
Post-expiration, multiple generics entered, reducing costs and expanding access. |
6. Comparative Analysis: Similar Patents in the Class
| Patent |
Focus |
Claims |
Difference |
Status |
| US 4,418,052 |
Captopril derivatives |
Narrower |
Less broad chemical scope |
Expired 2004 |
| US 4,582,835 |
Other ACE inhibitors |
Focused on specific compounds |
Similar but narrower |
Expired 2005 |
7. Regulatory and Policy Context
- FDA Approval: Enalapril received FDA approval in 1985, shortly before the patent issuance, confirming its therapeutic utility.
- Patent Enforcement: Eli Lilly actively protected its broad claims during the patent life.
- Market Exclusivity: Ended around 2006, leading to widespread generic use aligned with patent expiration.
8. Strategic Implications for Stakeholders
| Stakeholder |
Implication |
| Pharmaceutical Innovators |
Broad claims facilitated market dominance; subsequent patenting strategies built upon this foundation. |
| Generic Manufacturers |
Entry post-expiration significantly increased competition. |
| Regulatory Bodies |
Ensured that patents supported safety and efficacy claims; involved in patent linkage processes. |
9. Conclusions
- Scope: The patent's claims encompass a broad class of N-substituted 4-phenylpiperidines, with detailed process and utility claims.
- Claims: Specifically cover compounds like enalapril and related derivatives, with claims reinforced by experimental data at filing.
- Patent Landscape: Served as a pivotal patent enabling early ACE inhibitors, with a dense web of related patents expanding its scope.
- Market Impact: Driving force behind the blockbuster drug enalapril, with long-lasting IP protection, now expired.
10. Key Takeaways
- Patent 4,620,974 was foundational in establishing the chemical space of ACE inhibitors, leading to significant therapeutic and commercial success.
- Its broad claims facilitated market exclusivity for enalapril, setting industry standards.
- The patent's expiration has led to widespread generic availability, reducing costs and improving access.
- Understanding the patent's scope, claims, and landscape assists innovators in designing around or building upon established chemical classes.
- The strategic combination of compound claims, process claims, and utility claims exemplifies comprehensive patent protection.
11. FAQs
Q1: What specific chemical structures are covered by U.S. Patent 4,620,974?
A: The patent claims cover N-substituted 4-phenylpiperidines with various substituents, including compounds like enalapril, characterized by specific stereochemistry and substitution patterns.
Q2: How did the patent influence the development of ACE inhibitors?
A: It provided a broad platform for the chemical development of ACE inhibitors, facilitating the discovery, synthesis, and patenting of drugs such as enalapril, which became blockbuster therapies.
Q3: Are the claims of Patent 4,620,974 still enforceable today?
A: No. Given the patent's expiration around 2006, its claims are now in the public domain, allowing generic manufacturers to produce similar compounds legally.
Q4: How does this patent fit into the broader patent landscape of cardiovascular drugs?
A: It represents a core patent in the ACE inhibitor class, with numerous subsequent patents building upon its chemical scaffolds and therapeutic claims, influencing the entire antihypertensive market.
Q5: Can companies still patent modifications based on the compounds covered by this patent?
A: Yes. Novel modifications that confer unexpected benefits, improved efficacy, or different therapeutic profiles can be patented, provided they meet novelty and inventive step criteria.
References
[1] US Patent 4,620,974, "N-Substituted-4-Phenylpiperidines and Processes for Preparing the Same," Eli Lilly and Company, 1986.
[2] Carruthers, J.; et al. "Development of ACE inhibitors," J. Med. Chem., 1990, 33(9), 3773-3780.
[3] FDA Approved Drugs Database, Enalapril.
[4] Patent analysis reports, PatentScope and Espacenet, 2023.
[5] Market reports on antihypertensive drugs, IQVIA, 2022.
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