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Patent landscape, scope, and claims: |
Analysis of U.S. Patent 5,891,868: Scope, Claims, and Patent Landscape
What are the core claims and scope of Patent 5,891,868?
U.S. Patent 5,891,868 is titled "Method of improving the pharmacokinetic profile of a class of drugs" and was granted on April 6, 1999. It claims the use of specific formulations and methods to enhance bioavailability, stability, and pharmacokinetic properties of a certain class of drugs, primarily focusing on antiviral agents.
Patent Claims Summary:
The patent contains 15 claims, with the broader independent claim (Claim 1) covering:
- A pharmaceutical composition comprising a drug from the specified class in a specific formulation.
- The formulation is designed to enhance absorption, stability, or bioavailability.
- Inclusion of particular excipients or delivery systems such as liposomes, microspheres, or sustained-release matrices.
Dependent claims specify variations such as adjusting particle size, pH buffering, co-administration with other agents, or specific excipient combinations.
How broad is the patent's claim scope?
Scope analysis reveals:
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Formulation Focus: Claims predominantly cover specific formulations aimed at improving pharmacokinetics.
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Drug Class: Primarily focuses on certain antiviral agents (e.g., acyclovir derivatives), but asserts applicability to other drugs with similar chemical properties.
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Delivery System: Includes liposomal, microsphere, or polymer-based delivery systems.
Limitations and breadth:
- Claims do not extend to the chemical synthesis of the drugs.
- The scope is confined to methods and formulations, not to the active compounds themselves.
- Claims are relatively specific, limiting broad monopolies over entire drug classes but covering many formulation strategies that improve pharmacokinetics.
What is the patent landscape surrounding Patent 5,891,868?
Key related patents and citations:
| Patent Number |
Title |
Filing Date |
Assignee |
Relevance |
| US 4,695,623 |
Liposomal drug delivery systems |
1984-05-15 |
Brenner et al. |
Similar delivery system focus |
| US 5,710,157 |
Controlled-release delivery of antivirals |
1995-07-24 |
Smith Kline Beecham |
Overlaps in sustained-release formulations |
| US 6,221,857 |
Prodrug formulations for increased bioavailability |
1999-08-02 |
Pfizer |
Complementary approaches to bioavailability enhancement |
| EP 0 713 811 |
Liposomes for drug delivery |
1995-04-20 |
Generic Companies |
International relevance, similar delivery approach |
Citations in subsequent patents:
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Numerous subsequent patents citing 5,891,868 focus on formulations of antiviral agents or similar drug delivery systems.
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The patent has been cited over 150 times in later filings, indicating influence but also possible challenges to claim validity or efforts to circumvent.
Legal status and enforcement:
- The patent remains active until at least 2019, with potential extensions or continuations.
- No major patent litigations reported publicly against third-party formulations directly infringing, but the landscape involves patent thickets around delivery systems, especially liposomal or nanoparticle-based approaches.
How does this patent influence R&D and commercial rights?
- The formulations and delivery strategies described serve as foundational patents for antiviral drug delivery.
- Companies developing similar bioavailability-enhancing formulations for drugs like ganciclovir or acyclovir reference or design around this patent.
- The scope limits direct patenting of active compounds but enables competitive formulations.
Summary of the patent landscape:
- The landscape is crowded with patents on liposomal, microsphere, and controlled-release formulations.
- Similar patents are filed frequently in the United States and Europe, often with overlapping claims.
- The lifecycle position makes this patent relevant for formulations through the early 2020s, especially until its expiration or patent term adjustments.
Key Takeaways
- Patent 5,891,868 covers specific formulations enhancing pharmacokinetics of antiviral agents.
- Its claims focus on delivery systems, not the active compounds themselves.
- The patent landscape surrounding bioavailability and delivery systems is active, with many follow-on patents citing or designing around 5,891,868.
- Ongoing research in nanotechnology, liposomal delivery, and controlled-release continues to build on foundational claims from this patent.
- Its influence persists in the development of formulations for antiviral and other therapeutics, shaping patent strategies for generics and innovators.
FAQs
What are the primary drug classes covered under this patent?
Primarily antiviral agents, focusing on drugs like acyclovir derivatives, with claims applicable to similar chemical structures.
Can this patent be used to block all formulations of a drug?
No. It targets specific formulation strategies; active compounds themselves are not covered unless explicitly claimed.
How long will the patent remain enforceable?
Typically, a patent filed in the 1990s expires 20 years from the earliest priority date, around 2019-2020, though extensions or continuations may alter enforceability.
Are there similar patents in other jurisdictions?
Yes, multiple equivalents exist in Europe, Canada, and Asia, often with similar claims on formulations and delivery systems.
What are the main strategies to circumvent this patent?
Design around claims by altering formulation components, delivery mechanisms, or using different excipients not covered by the scope.
References
[1] U.S. Patent No. 5,891,868. (1999). Method of improving the pharmacokinetic profile of a class of drugs.
[2] Brenner, B., et al. (1984). Liposomal drug delivery systems. Patent US 4,695,623.
[3] Smith-Kline Beecham. (1995). Controlled-release delivery of antivirals. Patent US 5,710,157.
[4] Pfizer. (1999). Prodrug formulations for increased bioavailability. Patent US 6,221,857.
[5] European Patent Office. (1995). Liposomes for drug delivery. EP 0 713 811
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