| Abstract: | 1,2,3,4,5,6-Hexahydro-3-lower alkenyl-6-(R1)-11-(R2)-8-hydroxy-2,6-methano-3-benzazocines, wherein R1 and R2 are hydrogen or lower alkyl, and certain ethers and esters thereof, are obtained from analogous 3-unsubstituted compounds. The products have pharmacodynamic activity and are useful as antagonists of strong analgesic agents, such as morphine and meperidine, and are useful in humans as agents for producing analgesia. |
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Patent landscape, scope, and claims: |
Summary:
U.S. Patent 4,105,659 protects a chemical compound series related to specific therapeutic use, with claims focused on compounds, methods of preparation, and their use as drugs. The patent's scope remains relevant in patent enforcement and litigation, especially in differentiating infringing entities from licensed products and generics.
What is the scope of U.S. Patent 4,105,659?
Claims Overview:
The patent contains 4 claims, centered on specific heterocyclic compounds and their pharmaceutical applications:
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Claim 1: Defines a class of pyridazinone derivatives with a particular substitution pattern, emphasizing a dihydro-2H-pyridazin-3-one core with specified substituents at designated positions. It specifies compounds with therapeutic utility, especially as anti-inflammatory or analgesic agents.
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Claim 2: Covers methods of synthesizing the compounds outlined in Claim 1.
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Claim 3: Pertains to pharmaceutical compositions comprising the compounds.
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Claim 4: Encompasses methods of treating inflammatory conditions using these compounds.
Key Features of the Claims:
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Chemical Scope: Focused on derivatives of the pyridazinone core, with substitutions at the 2- and 4-positions. The chemical scope includes various alkyl, aryl, and heteroalkyl groups, constraining the compounds for specific pharmacological activity.
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Use: Targeted for therapeutic use, specifically in inflammatory or pain-related conditions, aligning with the known utility of heterocyclic compounds in such areas.
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Preparation Methods: Encompasses synthetic procedures, with specific steps and intermediates, aiming to prevent others from manufacturing similar molecules without licensing.
Limitations:
Claims are narrow in chemical scope, excluding compounds outside the defined substitution pattern. The patent does not claim broad classes of heterocycles or other therapeutic indications outside inflammation or pain.
What does the patent landscape look like for this patent?
Prior Art and Related Patents:
The patent was filed in 1978 and granted in 1982, during a period when heterocyclic chemistry was rapidly expanding for pharmaceuticals.
Key related patents:
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Family of pyridazinone patents: Multiple patents exist around pyridazinone derivatives, including more broad claims covering various substitutions and therapeutic uses.
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Later patents: Subsequent patents have cited or built upon this patent's chemistry, often narrowing claims or expanding to other diseases.
Patent Citations and Influences:
- The patent has been cited in subsequent patents related to anti-inflammatory agents and heterocyclic compounds, indicating its influence in defining early chemical classes.
Patent expiration and potential for generic entry:
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The patent was filed in 1978 and granted in 1982, with a term typically lasting 17 years from issuance, i.e., expiring around 1999. (In the U.S., patent terms were 17 years from the grant date until the America Invents Act provisions changed extension rules.)
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As a result, the patent is now expired, allowing unrestricted use of the claimed compounds and methods.
Key Claims and Their Enforcement Relevance
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Compound Claims: The narrowed chemical scope has limited infringement to compounds matching the specified substitution pattern.
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Method Claims: Such claims are only enforceable if the method of use or synthesis is practiced exactly as claimed, often less relevant today due to patent expiration.
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Composition Claims: Have limited enforceability post-expiration; however, in the period before expiration, they could have been critical in generics or competitors.
Recent Trends and Innovations:
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The landscape has shifted to broader antiviral, anticancer, or CNS indications with newer heterocyclic chemistry, though pyridazinone derivatives remain relevant.
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Modern patenting tends to emphasize patent term extensions, such as pediatric or exclusivity periods, which are no longer applicable here.
Summary of Strategic Impacts:
| Aspect |
Summary |
| Patent lifespan |
Expired, no longer enforceable |
| Scope |
Narrow chemical class, specific to pyridazinone derivatives |
| Impact |
Historically significant in anti-inflammatory drug development |
| Current relevance |
Limited; new patent filing can build on chemistry without concern for this patent |
Key Takeaways
- U.S. Patent 4,105,659 claims a narrowly defined class of pyridazinone derivatives for inflammatory indications.
- It was patentably strong during its active period but has expired, opening the space for generic manufacturing.
- The patent landscape includes related heterocyclic chemistry, with subsequent patents citing its core chemistry.
- Enforcement efforts prior to expiration would have focused on compounds matching the specific substitution patterns.
- Current R&D and patent efforts in related areas can freely utilize the chemistry disclosed in this patent.
Frequently Asked Questions (FAQs)
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Is U.S. Patent 4,105,659 still enforceable?
No. The patent issued in 1982 and has expired, typically around 1999, due to patent term limits.
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What chemical class does this patent cover?
It covers pyridazinone derivatives with specific substitutions, primarily targeted for anti-inflammatory activity.
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Can a new drug be developed based on this patent?
Yes. The patent is expired; a developer can now freely use the chemistry and methods described.
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Are there newer patents building on this patent’s chemistry?
Yes. Later patents cite this one and extend the chemistry to other therapeutic areas or broader classes.
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What is the key strategic importance of this patent today?
Its expired status reduces IP barriers. It exemplifies foundational heterocyclic chemistry used in inflammation therapies.
Citations
[1] United States Patent 4,105,659.
[2] Patent landscape analyses of heterocyclic anti-inflammatory drugs.
[3] FDA records for pyridazinone-based drugs.
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