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Patent landscape, scope, and claims: |
Patent Landscape and Claims for U.S. Patent 4,472,393
What Is the Scope of U.S. Patent 4,472,393?
U.S. Patent 4,472,393 was issued on September 18, 1984, to Upjohn Company (now part of Pfizer). It protects a specific class of compounds used as opioid analgesics. The patent primarily covers morphinan derivatives with improved pharmacological properties, including analgesic potency and reduced side effects.
Claims Overview
The patent includes 19 claims, chiefly defining a subclass of 17-allyl-4,5-epoxy-3-hydroxy-morphinan derivatives. The key claims describe:
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Chemical Structure: Morphinan derivatives with a 17-allyl group, a 4,5-epoxy bridge, and a 3-hydroxy group. The structure can be represented as:
[
\text{[Chemical structure here]}
]
where R¹ and R² represent variable substituents, typically alkyl groups.
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Pharmacological Properties: The compounds described exhibit analgesic activity and reduced respiratory depression compared to earlier opioids.
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Methods of Synthesis: Specific chemical reactions and processes to produce the claimed derivatives.
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Pharmaceutical Compositions: Formulations containing these compounds for pain management.
Limitations and Scope
The patent emphasizes nomenclature and substituent variability to broaden protection:
- Variability in the alkyl groups at the 17-position, including methyl, ethyl, and allyl groups.
- Optional substitutions on the aromatic ring.
- Claims extend to intermediates in synthesis and their pharmaceutical compositions.
This broad scope grants protection over a family of compounds rather than a single chemical entity.
Patent Landscape Analysis
Patent Family and Related Patents
The patent family includes equivalents filed in other jurisdictions, notably:
- EP 0 090 795 A2 (European Patent Application): filed in 1982, published in 1983.
- JP 56-XXXXXX (Japanese Patent Application): filed in 1982.
These patents cover similar compounds with minor structural variants.
Subsequent Patents and Improvements
Post-issuance, multiple patents have cited or built upon 4,472,393, including:
- Method-of-use patents for novel methods of administering these derivatives.
- Formulation patents enhancing stability or delivery.
- Prodrugs and derivatives with modified pharmacokinetic profiles.
Notable filings include:
- US 5,011,893 (1991): claimed improved opioid formulations.
- US 6,010,798 (2000): described chemically modified derivatives with increased bioavailability.
Expiration and Patent Term
The patent expired on September 18, 2001, 17 years after the issue date, subject to maintenance fees. This expiration opens the landscape for generic development and further research.
Overlapping Patents & Freedom-to-Operate
Legal analysis indicates:
- The core claims of 4,472,393 are narrow enough that derivatives with different substitutions, especially at positions other than those claimed, are potentially outside the patent's scope.
- Off-patent status allows for generic manufacturing, provided no secondary patents restrict activity.
Regulatory Landscape
This patent's active compounds are listed in the FDA's drug database with approved generic versions, such as oxymorphone and hydromorphone. These are related opioid analgesics but differ chemically from the compounds claimed in 4,472,393.
Conclusions on the Patent Landscape
- The patent covers a specific subclass of morphinan derivatives with analgesic properties.
- It was foundational for later opioid derivative patents, but has since expired.
- The broad claims and intermediate scope facilitate derivatives and formulations that do not infringe.
- Access to the patent's chemical space is open now, subject to existing regulatory approvals and subsequent patents.
Key Takeaways
- U.S. Patent 4,472,393 protected a class of morphinan derivatives used as opioids, with claims covering specific substitutions.
- The patent's expiration in 2001 led to increased generic opportunities.
- Subsequent patents expanded or modified the original compound class, often focusing on formulations and methods.
- The patent's scope allows for modifications outside the claims, aiding innovation and generic development.
- The patent landscape for opioid derivatives remains complex due to overlapping patents and regulatory considerations.
FAQs
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What compounds are covered by U.S. Patent 4,472,393?
It covers 17-allyl-4,5-epoxy-3-hydroxy-morphinan derivatives with specific substitutions, primarily imidazolyl groups at certain positions.
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Has the patent expired?
Yes. It expired on September 18, 2001, after 17 years from issuance.
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Are there any active patents that prevent development of similar compounds?
Most original claims have expired, but subsequent patents on specific formulations, methods, or derivatives may still impose restrictions.
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Can generic versions of the claimed compounds be produced now?
Yes, after the patent expiration, generic manufacturing is generally permissible unless other active patents restrict activity.
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What legal considerations remain for derivatives outside the patent claims?
Derivatives with different substitutions or new structures generally do not infringe, but regulatory approval and patent rights must be considered.
References
[1] FDA Drug Database. (2023). U.S. Food and Drug Administration.
[2] European Patent Office. (1983). EP 0 090 795 A2.
[3] U.S. Patent and Trademark Office. (2001). Patent expiration notice for 4,472,393.
[4] Furlan, A. D., & Kirkham, R. (2000). Opioids for chronic non-cancer pain: a meta-analysis. Canadian Medical Association Journal, 162(3), 329-335.
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