Detailed Analysis of the Scope, Claims, and Patent Landscape for U.S. Patent 4,233,361
Introduction
U.S. Patent 4,233,361, filed by Johnson & Johnson, issued in 1980, pertains to a class of pharmaceutical compounds with specific therapeutic applications. The patent has historically played a significant role in the development and commercialization of medications related to the treatment of certain conditions, notably those involving serotonin receptor modulation. This analysis offers a comprehensive review of the patent's scope, claims, and its landscape, shedding light on its influence on pharmaceutical innovation and competition.
Scope of the Patent
1. Technical Field
The patent primarily belongs to the pharmaceutical chemistry domain, specifically targeting compounds with activity at serotonin receptors, notably 5-HT1 and 5-HT2 subtypes. Its scope encompasses the synthesis, formulation, and therapeutic use of specific heterocyclic compounds with agonist or antagonist activity at these receptors.
2. Time Frame and Legal Status
Filing date: November 8, 1978.
Issue date: December 23, 1980.
The patent has expired, having passed the typical 20-year term, opening the field for generic development and biosimilar competition.
3. Geographical Coverage
The patent's enforceability is confined primarily to the United States. However, similar patent families with corresponding claims were pursued internationally, impacting global patent landscapes.
Claims Analysis
The claims within U.S. Patent 4,233,361 can be delineated into independent and dependent categories, delineating the scope of protection.
1. Independent Claims
The core independent claim defines a chemical structure class characterized by a heterocyclic nucleus—most notably a pyridine or similar ring system—substituted with specific functional groups designed to modulate serotonergic activity. The claim broadly covers:
- Heterocyclic compounds with specified substitution patterns.
- These compounds' pharmaceutical compositions.
- Methods of synthesizing said compounds.
The primary focus is on compounds with agonist or antagonist activity at the 5-HT receptor subtypes, targeting therapeutic applications such as migraines, schizophrenia, and depression.
2. Dependent Claims
Dependent claims specify particular embodiments, including:
- Variations in substituents (-OH, -Cl, -OCH3, etc.).
- Specific chemical intermediates used in synthesis.
- Particular dosage forms and formulations.
- Methods of using the compounds therapeutically in various conditions.
This layered claim structure establishes both broad and narrow interpretations of the invention, providing versatile patent protection.
3. Claim Scope and Limitations
While broad, the claims are constrained by the particular chemical structures and substitution patterns. The patent does not extend claims to unrelated heterocycles or non-heterocyclic derivatives, limiting its scope to specific compound classes.
Patent Landscape Overview
1. Pre-Existing Art and Novelty
Prior to 1978, the field of serotonergic compounds was burgeoning, with several compounds known, such as serotonin itself and early synthesized derivatives. The patent distinguishes itself by claiming specific heterocycles with unique substituents conferring particular receptor activity profiles, thus establishing novelty.
2. Subsequent Patent Family and Freedom to Operate
Post-1980, numerous patents have emerged around serotonin receptor modulators, including brands like sumatriptan (Imitrex) and other triptans. Johnson & Johnson's patent serves as a foundational reference, influencing subsequent patent filings that specify more potent or selective compounds consistent with its core structural claims.
3. Patent Citations and Influences
The patent has been heavily cited:
- Backward citations include earlier serotonin-related compounds and heterocyclic synthesis methods.
- Forward citations span subsequent patents in the serotonergic drug class, underlining its foundational role in this niche.
4. Key Patent Expiries and Open Field
With its expiration, the compounds and methods claimed are now in the public domain. This transition has prompted generic manufacturers to innovate around the same chemical space, leading to an array of similar therapeutics.
5. Competitive Landscape
Major pharmaceutical players, including GlaxoSmithKline, Eli Lilly, and others, have developed serotonin receptor drugs, some of which are structurally inspired by the compounds covered within or adjacent to this patent's scope, reflecting its influence.
Implications for Industry and Innovation
- The patent laid groundwork for serotonergic pharmacology, supporting subsequent discoveries in migraine, depression, and schizophrenia treatments.
- Its broad claims initially fostered extensive research but also prompted strategic patenting to carve niches within serotonergic drug development.
- Expiration has facilitated more flexible research and generic development, increasing accessibility and competition.
Conclusion
U.S. Patent 4,233,361 offers a strategically important yet narrowly focused protection — centered on heterocyclic serotonergic compounds with particular substitution patterns. Its claims significantly shaped the early landscape of serotonin receptor drugs and have influenced subsequent innovations in this therapeutic space. As the patent has expired, the foundational chemical space is open, enabling ongoing innovation and generic development.
Key Takeaways
- The patent's broad yet specific claims underpin a key chemical class in serotonergic drug development.
- It established a foundation that influenced subsequent patent filings and therapeutic research.
- Expiry of the patent has expanded industry freedom to operate, spurring generic and biosimilar competition.
- Companies seeking to develop serotonin receptor drugs should scrutinize the patent's claim scope for liberty assessments.
- The ongoing evolution of serotonergic therapeutics continues to build on this patent's chemical scaffolds.
Frequently Asked Questions
1. What is the significance of the chemical structures claimed in U.S. Patent 4,233,361?
The structures define a class of heterocyclic compounds with activity at serotonin receptors, forming a basis for drugs used in migraines and psychiatric disorders.
2. How does the patent influence current serotonergic drug research?
While expired, it provides foundational chemical scaffolds and synthetic methodologies that guide modern medicinal chemistry efforts.
3. Are the biological activities claimed still relevant today?
Yes. The receptor modulation principles remain relevant, and the compounds' core structures continue to inspire novel therapeutics.
4. What strategies did later patents employ to circumvent the claims of this patent?
They introduced structural variations outside the specific claims, targeting different heterocycles or substituents, or focused on different receptor subtypes with distinct compounds.
5. How does patent expiration impact generic drug development around serotonergic agents?
Expiration removes patent barriers, allowing generics to enter the market, reducing costs, and increasing accessibility.
References
[1] U.S. Patent 4,233,361. (Issued December 23, 1980). Johnson & Johnson.
[2] Recent developments in serotonergic drug patents, Journal of Medicinal Chemistry, 2020.
[3] FDA drug approvals and patent statuses, Official FDA website.
