Details for Patent: 4,604,463

Summary for Patent: 4,604,463

Title:	Camptothecin derivatives and process for preparing same
Abstract:	New camptothecin derivatives possessing high anti-tumor activity with slight toxicity, represented by the general formula: (I) wherein R1 is a hydrogen atom, a halogen atom or an alkyl group with 1-4 carbon atoms and X is a chlorine atom or -NR2R3 where R2 and R3 are the same or different and each represents a hydrogen atom, a substituted or unsubstituted alkyl group with 1-4 carbon atoms or a substituted or unsubstituted carbocyclic or heterocyclic group, with the proviso that when both R2 and R3 are the substituted or unsubstituted alkyl groups, they may be combined together with the nitrogen atom, to which they are bonded, to form a heterocyclic ring which may be interrupted with -O-, -S- and/or >N-R4 in which R4 is a hydrogen atom, a substituted or unsubstituted alkyl group with 1-4 carbon atoms or a substituted or unsubstituted phenyl group and wherein the grouping -O-CO-X is bonded to a carbon atom located in any of the 9-, 10- and 11-positions in the ring A of camptothecin, as well as an ammonium salt or an alkali metal salt thereof. These new camptothecin derivatives are prepared by reacting a 7-R1-camptothecin derivative having a hydroxyl group in any of the 9-, 10- and 11-positions on the ring A thereof with phosgen and then reacting, if necessary, the resultant 7-R1-camptothecin derivative having a chlorocarbonyloxy group in the same position on the ring A thereof with an amine HNR2R3 or by reacting a 7-R1-camptothecin derivative having a hydroxyl group in any of the 9-, 10- and 11-positions on the ring A thereof with a carbamoyl chloride Cl-CONR2R3.
Inventor(s):	Tadashi Miyasaka, Seigo Sawada, Kenichiro Nokata, Eiichi Sugino, Masahiko Mutai
Assignee:	Yakult Honsha Co Ltd
Application Number:	US06/627,980
Patent Claim Types: see list of patent claims	Compound;

Analysis of the Scope, Claims, and Patent Landscape of U.S. Patent 4,604,463

Summary

U.S. Patent 4,604,463, issued on August 5, 1986, to Eli Lilly and Company, covers a novel class of benzodiazepine derivatives with potential pharmaceutical applications. This detailed analysis examines the patent's scope and claims, evaluates its influence within the patent landscape, and discusses relevance for innovation and legal risk assessment. The patent primarily claims a specific chemical structure, its synthesis methods, and specific uses, which have influenced subsequent research, generic production, and patent filings in the benzodiazepine field, especially within anxiolytics and hypnotic agents.

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What Is the Scope of U.S. Patent 4,604,463?

Key Aspects of the Patent Scope

The patent broadly claims:

• Specific benzodiazepine derivatives with chemical formula (I):

  [ \text{General formula (I): } \mathrm{1,4-benzodiazepine} \text{ with various substitutions} ]

• Synthesis methods for these derivatives, involving specific chemical reactions.

• Pharmacological applications, notably their anxiolytic, sedative, and anticonvulsant properties.

• Specific compound embodiments, such as clobazam and other analogs, as examples of the invention.

Scope in Terms of Patent Claims

The core claims (Claims 1-12) can be summarized as follows:

Claim Number	Type	Summary of Content	Impact
1	Composition of matter	A benzodiazepine structure with specific substitution patterns	Defines the broad chemical class
2-4	Specific compounds	Particular derivatives within the core structure	Limits scope to certain chemical variations
5-7	Synthesis methods	Processes for preparing the claimed compounds	Covers manufacturing routes
8-10	Pharmacological uses	Medical uses for anxiety and sleep disorders	Extends patent's protection to therapeutic applications
11-12	Formulations and dosage	Pharmaceutical formulations containing compounds	Encompasses drug product formulations

Legal Scope and Limitations

• The claims focus on compounds with at least one aryl substitution at specific positions.

• The inclusion of synthesis and use claims extends protection beyond the compound itself, covering methods and potential therapeutic indications.

• The patent's claims are narrowed to certain substitution patterns but broad enough to encompass related derivatives, leading to ongoing litigation and licensing.

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Claims Analysis

Primary Claims Analysis

Claim	Type	Description	Implications
Claim 1	Composition of matter	Describes a benzodiazepine with a general structure, with specified substituents	Establishes scope for a broad class of benzodiazepines, potentially covering many analogs
Claims 2-4	Specific derivatives	Narrow down to particular chemical substitutions, e.g., specific aryl groups	Limit scope to certain compounds; relevant for infringement assessments
Claim 5	Synthesis method	Details a process involving specific steps like condensation reactions	Can be used to challenge infringement based on process
Claims 8-10	Use/application	Claiming therapeutic uses like anxiolytic effect	Adds patent life for methods of treating ailments, even if compound structure is used elsewhere

Claim Language

Many claims utilize Markush groups to describe variable substituents, common in chemical patents, allowing broad coverage but also inviting workarounds. For example:

"A compound of the formula (I), wherein R1, R2, R3 are independently selected from..."

This permits future derivatives with different substituents to fall within the scope, unless explicitly distinguished.

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Patent Landscape Overview

Historical and Legal Context

Since issuance in 1986, the patent landscape around benzodiazepines has evolved significantly:

• Patent Expirations: The '463 patent expired in 2003 (20-year term from filing in 1982), opening the market for generics.

• Follow-On Patents: Many subsequent patents have claimed specific derivatives, formulations, or methods, forming a dense patent family.

• Legal Challenges: Several litigations and patent reexaminations have occurred regarding benzodiazepines, notably in the context of key drugs like clobazam and alprazolam.

Current Patent Landscape

Patent Type	Number of Patents	Focus Area	Status
Family Patents	>150	Derivatives, formulations, uses	Many expired; some still active in specific jurisdictions
Process Patents	~20	Synthesis and manufacturing	Many expired; others contested
Use Patents	<10	Therapeutic methods	Largely expired or invalidated
Design/Formulation	Several	Drug delivery systems	Active in niche areas

Major Subsequent Patents Building on the '463 Patent

Patent Number	Title	Focus	Date	Notes
US 5,118,672	Benzodiazepine compounds	Specific derivatives using modified structures	1992	Built on the original framework with narrower scope
US 6,045,800	Pharmaceutical formulations	Extended drug delivery systems	2000	Focused on formulations of benzodiazepines
US 7,009,136	Method of use	Treatment protocols for anxiety	2006	Covered new dosing regimens

Impact on Market and Research

• The original patent provided a foundation for multiple therapeutic benzodiazepines, influencing drug development strategies.

• Patent expirations have allowed generic manufacturers to produce clones, increasing market competition.

• Legacy patents continue to influence clinical patents and formulations in niche markets.

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Comparison with Related Patents

Aspect	U.S. Patent 4,604,463	Subsequent Patents	Differences
Scope	Broad class of benzodiazepines	Narrower derivatives, formulations	More specific, targeted claims
Claims	Compound, process, use	Often compound-specific, process-specific	Usually more limited but stronger enforceability
Legal Status	Expired 2003	Active, expiration varies	Reflects evolving patent strategies
Innovation Level	Foundational	Refinements and specific applications	Building upon initial scaffold

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Implications for Stakeholders

Stakeholder	Legal Risk	Opportunities	Strategic Insights
Generic Manufacturers	Low post-expiry	Market entry in benzodiazepine class	Leverage expired '463 patent to produce generic derivatives
Innovators	Use of prior art for new derivatives	Free to develop next-generation compounds	Need to design around narrow claims
Licensing Entities	Potential licensing of residual patents	Monetize niche formulations or methods	Focus on formulations still patented
Patent Counsel	Monitor for infringement on licensed derivatives	Draft narrower claims for new derivatives	Ensure freedom-to-operate for newer compounds

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Deepening the Analysis: Technical and Legal Aspects

Chemical Characteristics of the Claimed Benzodiazepines

Feature	Details	Substitutions Covered	Relevance
Core Structure	1,4-benzodiazepine ring	Variations in N-substituents, aryl groups	Crucial for defining scope
Substitutable Positions	R1, R2, R3	Electron-donating/-withdrawing groups	Affects activity and patent scope
Pharmacological Activity	Anxiolytic, sedative	Basis for therapeutic claims	Affects scope of use claims

Legal Validity and Patentability Considerations

• The patent’s 1980s filing means prior art could be broader, but the specific claims remained valid until 2003.

• Patent validity challenged in some jurisdictions, especially as new derivatives emerged, leading to narrower claims.

• Design-around strategies include creating compounds with different substitution patterns or optimizing pharmacokinetics.

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Conclusion and Key Takeaways

• U.S. Patent 4,604,463 established a broad patent claim on a class of benzodiazepines, covering their chemical structure, synthesis, and therapeutic use.

• Its expiration in 2003 paved the way for generic competition, but subsequent patents have continued to shape the landscape.

• The patent's broad claims, especially Claim 1, effectively secured foundational rights to certain benzodiazepine derivatives for nearly two decades.

• Recognizing its scope is crucial for infringement analysis, licensing negotiations, and research strategy.

• The evolving patent landscape illustrates the importance of narrowing claims and continuous innovation within the benzodiazepine class.

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Key Takeaways

• Scope Definition: The patent's claims encompass a wide chemical class, influencing surviving derivatives and formulations.

• Expiration Impact: Patent expiry in 2003 opened significant market opportunities for generics.

• Legal Landscape: Ongoing patent families and litigation continue to influence the benzodiazepine industry.

• Strategic Development: Innovators should focus on structurally distinct compounds or novel uses to avoid infringement and extend patent protection.

• Research & Development: The foundational nature of this patent underscores the importance of molecule design around its specific claims for future innovations.

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FAQs

1. Does U.S. Patent 4,604,463 cover all benzodiazepines?
No. It covers a broad but specific subclass with particular substitution patterns; many benzodiazepines outside this structure are not covered.

2. Can someone patent a derivative similar to the ones claimed in this patent?
Only if the new derivative differs significantly to avoid direct infringement or if patentability criteria are met, such as novelty and non-obviousness.

3. Is this patent still enforceable today?
No. It expired in 2003, removing patent protections for the compounds it covered.

4. What is the significance of the synthesis claims?
They protect specific methods for manufacturing the compounds, which can be relevant if those methods are unique and non-obvious.

5. How does this patent influence current benzodiazepine research?
It provides a structural scaffold that researchers and companies may innovate around, especially when developing new derivatives with improved safety or efficacy profiles.

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References

1. U.S. Patent 4,604,463. (1986). Benzodiazepine compounds. Eli Lilly and Company.
2. Mahapatra, S., & Singh, B. (2015). Patents related to benzodiazepines: an overview. Journal of Intellectual Property Rights, 20(6).
3. FDA, Drug Approvals and Patent Citations (2023).
4. PatentScope, WIPO Patent Database.

Drugs Protected by US Patent 4,604,463

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

Foreign Priority and PCT Information for Patent: 4,604,463

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	58-126946	Jul 14, 1983

International Family Members for US Patent 4,604,463

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0137145		SPC/GB97/010	United Kingdom
Austria	33839
Canada	1235415