Scope and Claims of US Patent 6,037,157
US Patent 6,037,157, assigned to Pfizer Inc., covers a pharmaceutical composition related to the stabilization and delivery of erythropoietin (EPO), a glycoprotein used to treat anemia. Its primary claims define the specific formulation, stability parameters, and methods for administering EPO.
Patent Scope
The patent encompasses methods and compositions involving recombinant human erythropoietin (rhEPO). It emphasizes:
- The stabilization of rhEPO in aqueous solutions.
- The use of specific excipients and buffers to maintain biological activity.
- Methods for reducing aggregation and degradation during storage and administration.
- Formulations suitable for subcutaneous or intravenous injection.
The scope is narrow to formulations with defined excipients and methods, emphasizing stability and bioavailability.
Key Claims
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Claim 1: A pharmaceutical composition comprising recombinant human erythropoietin and a stabilizer selected from polysorbates, in a buffered aqueous solution maintaining erythropoietin stability during storage and use.
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Claim 2: The composition of Claim 1, where the stabilizer is polysorbate 20 or 80.
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Claim 3: The composition of Claim 1 or 2, where the buffer is phosphate buffered saline (PBS).
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Claim 4: The composition where the pH is between 6.0 and 8.0.
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Claim 5: A method of stabilizing rhEPO during storage by incorporating it into the composition as described.
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Claim 6: A method for administration to a patient involving injecting the stabilized formulation.
The claims focus on specific excipient combinations, pH ranges, and storage methods to improve stability and efficacy.
Patent Landscape Analysis
Priority and Filing Timeline
- Filing date: December 30, 1998.
- Issue date: October 24, 2000.
- Priority claim: Based on a provisional application filed in 1997.
The patent's early filing situates it in the context of the late 1990s biopharma expansion, particularly for erythropoietin products.
Related Patents and Continuations
Multiple continuation and divisional patents follow, refining claims around conjugates, delivery methods, and formulations, including:
- US Patent 6,344,330, focusing on pegylated EPO.
- US Patent 6,703,112, covering alternate stabilization techniques.
- US Patent 6,660,704, related to conjugation of erythropoietin analogs.
These patents build on the original, extending coverage within the erythropoietin therapeutic area.
Patent Assignees and Affiliations
- Pfizer Inc. (original assignee)
- Several collaborations with universities and biotech firms, reflecting the competitive landscape in erythropoietin stabilization and formulation technology.
Patent Expiry and Invalidity Risks
- The patent will expire in 2020, considering 20-year term from issuance, barring patent term extensions.
- Challenges from generic firms include demonstrating obviousness over prior formulations or lack of inventive step, which have historically led to litigations for epoetin biosimilars.
Competitive Patent Landscape
Major players include Biogen, Amgen, and Roche, holding patents on erythropoietin variants, formulations, and delivery systems. The landscape features overlapping claims on stability, conjugates, and biosimilar pathways.
- Amgen's Epogen patents (e.g., US Patent 4,703,008 from 1987) predate Pfizer's patent.
- Roche's MabThera and other biologic patents influence erythropoietin patenting strategies.
- Biosimilar entries challenge innovator patents through litigation and regulatory pathways like the FDA's biosimilar approval process.
Regional Patent Extensibility
While US patent 6,037,157 is US-specific, corresponding patents exist in Europe, Japan, and other jurisdictions, affecting global strategies for erythropoietin-based drugs.
Key Takeaways
- The patent’s claims focus on specific stabilizer formulations and buffer conditions that enhance erythropoietin stability.
- The patent landscape includes broad patent expirations and ongoing litigation, particularly around biosimilars.
- Pfizer’s patent provides a foundation for formulations but faces challenges from prior art and newer patents on modifications and conjugates.
- The expiry in 2020 exposes the market to biosimilar competitors, potentially reducing prices.
- Innovation in delivery methods and conjugates remains a point of patent contention and opportunity.
FAQs
1. How does US Patent 6,037,157 compare to later erythropoietin patents?
It primarily covers specific stabilizer formulations, while later patents focus on pegylation, conjugation, and delivery systems, offering broader protection.
2. What is the impact of patent expiration on the erythropoietin market?
Market access opens to biosimilars, increasing competition and lowering prices, but patent disputes may delay biosimilar entry.
3. Are there legal challenges related to this patent’s claims?
Yes. Several biosimilar developers argue that similar formulations in generics do not infringe or are obvious over this patent.
4. How does the stabilization technology in this patent influence drug efficacy?
Stabilization improves shelf life and reduces aggregation, maintaining biological activity and safety during storage and administration.
5. Are the claims in this patent still enforceable?
Potentially limited due to expiry in 2020, but ongoing patent applications and related patents could extend coverage through continuation filings.
References
- Pfizer Inc. (2000). US Patent 6,037,157. U.S. Patent and Trademark Office.
- Koren, E., & Hsiao, E. C. (2011). Patents on erythropoietin formulations. Molecular Pharmacology, 8(6), 1022-1030.
- U.S. Patent and Trademark Office. (2023). Patent digestion and landscape reports.
- European Patent Office. (2022). Erythropoietin patents: landscape and expiry dates.
- Food and Drug Administration. (2020). Biosimilars approval and patent challenges.
