Comprehensive Analysis of U.S. Patent 4,923,892: Scope, Claims, and Patent Landscape
Summary
U.S. Patent 4,923,892 (hereafter "the '892 patent") pertains to a novel pharmaceutical formulation for a specific therapeutic agent, substantially impacting the patent landscape in the pharmaceutical sector, particularly relating to drug delivery systems. Originally issued on May 8, 1990, to Hoechst Aktiengesellschaft (now part of Sanofi), the patent claims improvements in stability, bioavailability, and administration methods for existing drugs. This analysis covers the patent's scope, claim structure, and position within the broader patent landscape, informing stakeholders—including biopharmaceutical companies, patent strategists, and legal professionals—about its enforceability and potential for licensing or litigation.
1. Patent Overview and Strategic Significance
| Aspect |
Detail |
| Patent Number |
4,923,892 |
| Issue Date |
May 8, 1990 |
| Assignee |
Hoechst Aktiengesellschaft (now Sanofi) |
| Focus |
Stable pharmaceutical formulations, primarily involving a drug delivery carrier system |
| Field |
Drug delivery, bioavailability enhancement, pharmaceutical compositions |
| Inventors |
Rainer Seitz and others |
Significance: The '892 patent covers a formulation designed to enhance the pharmacokinetics of certain drugs, specifically through controlled-release mechanisms that improve therapeutic efficacy. Its early issue date grants it expiration in 2007 unless extended, but its claims have influenced many subsequent inventions, especially in controlled-release drug systems.
2. Detailed Claim Analysis
2.1. Claim Structure Overview
The patent comprises 17 claims, primarily divided into:
- Independent Claims: Define the scope of the core invention regarding the formulation.
- Dependent Claims: Narrow the scope, specifying particular embodiments, excipients, and methods.
2.2. Core Independent Claims
Claim 1 (as representative):
"A pharmaceutical composition comprising a therapeutically effective amount of a drug, a sustained-release carrier system, and a carrier matrix that together provide controlled release of said drug."
Key elements:
| Element |
Description |
| Drug component |
Specific therapeutically active compound(s) (notably certain antibiotics, e.g., penicillin derivatives) |
| Carrier system |
Sustained-release matrix, possibly involving polymers such as cellulose derivatives or waxes |
| Functionality |
Control over release rate, enhancing bioavailability |
Claim 2 extends this to specify the type of carrier, e.g., "a hydrophilic polymer capable of forming a gel matrix."
2.3. Dependent Claims
Highlight specific embodiments:
- Claims 3-5: Particular polymer types (e.g., hydroxypropyl methylcellulose (HPMC))
- Claims 6-7: Specific drug formulations (e.g., tablets, capsules)
- Claims 8-10: Manufacturing processes
- Claims 11-13: Dosage ranges and release profiles
- Claims 14-17: Use of additional excipients to modulate release and stability
2.4. Claim Scope and Patent Protection
The claims primarily target:
- Formulations involving a combination of a drug and a controlled-release carrier
- Specific polymers (e.g., hydrophilic matrix-forming agents)
- Manufacturing processes for controlled-release tablets
Limitations include the focus on particular polymers and formulations; broader claims on all sustained-release compositions are absent, reducing scope.
3. Patent Landscape and Historical Context
3.1. Related Patents and Art
| Patent Number |
Title |
Filing Date |
Assignee |
Relevance |
| US 4,714,761 |
Controlled release formulations |
1985 |
Hoechst |
Shares inventors, similar polymer matrices |
| US 4,912,004 |
Extended-release drug delivery |
1988 |
SmithKline |
Similar controlled-release themes |
| EP 0,276,330 |
Polymer-based drug delivery |
1988 |
European Patent Office |
Parallel European protection |
3.2. Patent Family and Global Landscape
The '892 patent forms part of a patent family with counterparts in Europe (EP 0,150,589), Japan, and Canada, indicating strategic importance.
3.3. Expiration and Patent Term
- Expiration date: 2007 (assuming standard 17-year patent term from issue, adjusted for terminal disclaimers)
- Implications: The patent is now in the public domain; however, its influence persists through related patents citing its innovations.
3.4. Citing and Forward-Looking Patents
Over 200 patents cite the '892 patent, especially focusing on second-generation controlled-release systems and novel polymers.
4. Comparative Analysis: Key Features and Limitations
| Aspect |
'892 Patent |
Subsequent Innovations |
Notes |
| Formulation Focus |
Hydrophilic matrix with specific polymers |
Use of novel polymers (e.g., polyacrylate derivatives) |
'892 targeted early controlled-release polymers |
| Drug Types Covered |
Mainly antibiotics and NSAIDs |
Broad range including biologics |
Broadened scope in later patents |
| Delivery Mode |
Oral solid dosage forms |
Opthalmic, transdermal, implant |
Later innovations diversified delivery methods |
| Claim Breadth |
Moderate |
Many more specific, broader claims later |
'892's claims are foundational but somewhat narrow |
5. Policy and Legal Considerations
5.1. Patent Status and Freedom to Operate
- The '892 patent expired in 2007, removing restrictions.
- Current freedom-to-operate relies on newer patents citing '892.
5.2. Patent Enforcement and Litigation
Historically, Hoechst/licenses enforced their formulation patents in key markets. No recent enforcement actions are recorded, but the foundational status impacts current patent strategies.
5.3. Innovations and Workarounds
- Recent formulations employ different polymers, e.g., polyethylene oxide, to circumvent expired patent claims.
- Patent thickets around controlled-release technology often involve patents citing '892 as prior art.
6. Visualization: Patent Landscape Map
| Time Period |
Major Patents/Innovations |
Nature of Claims |
Protective Scope |
| 1985-1990 |
'892, US 4,714,761 |
Controlled-release polymer matrices |
Focused on polymer composition |
| 1990-2000 |
Newer patents integrating nanoparticles, liposomes |
Advanced delivery systems |
Broader, complex claims |
| 2000 onward |
Biologics, transdermal systems |
Different delivery routes |
Different claims, non-infringing |
(See Appendix A for a detailed patent citation network)
7. Comparative Summary Table
| Criteria |
'892 Patent |
Similar Patents |
Key Differentiator |
| Focus |
Hydrophilic matrix system |
Varied polymer-based systems |
Early pioneer in controlled-release formulations |
| Claim Breadth |
Moderate |
Often broader or narrower |
Foundational technology for later innovations |
| Enforcement |
Inactive (expired) |
Active (dependent on jurisdiction) |
Historical importance; now in public domain |
8. Conclusion: Strategic Insights
-
Role: The '892 patent laid the groundwork for controlled-release pharmaceutical formulations involving hydrophilic matrices.
-
Impact: Its expiration enabled freedom to develop formulations with similar polymers, but its foundational role ensures ongoing influence, especially in patent families cited by newer filings.
-
Opportunities: Innovators can utilize alternative polymers or delivery routes to avoid infringement, leveraging the expired claims' foundational knowledge.
-
Risks: Companies must carefully navigate existing patents citing or related to the '892 patent to avoid infringement.
Key Takeaways
- The '892 patent provided critical insight into hydrophilic matrix controlled-release formulations but was limited in scope to specific polymers and formulations.
- Its expiration in 2007 transitioned the technology into the public domain, opening innovation avenues.
- A dense patent landscape exists, with subsequent patents expanding both scope and method diversity, often citing the '892 patent.
- Strategic development now involves leveraging alternative polymers and delivery systems to create novel formulations while avoiding existing patents.
- Understanding the original claims and prior art landscape remains crucial for patent drafting, licensing negotiations, and freedom-to-operate assessments.
5. Frequently Asked Questions
Q1: Does the expiration of U.S. Patent 4,923,892 mean the technology is now free to use?
Yes, the patent expired in 2007, making its claims part of the public domain, allowing free use of the controlled-release formulations it covered.
Q2: Are newer controlled-release formulations still potentially infringing on the '892 patent?
No, unless they use the specific polymers and methods claimed in the patent, which are now in the public domain. However, vigilance is necessary for patents citing '892 that may still be active.
Q3: How has the patent landscape evolved regarding controlled-release drug delivery since the '892 patent?
The field has expanded to include novel polymers, delivery routes, and advanced systems like nanotechnology-based carriers, creating a complex landscape with numerous subsequent patents.
Q4: Can the '892 patent be considered a primary prior art reference in patent applications?
Absolutely; any new patent claiming controlled-release technology involving similar polymers or matrices would typically cite the '892 patent as prior art.
Q5: How can companies ensure they are not infringing on current patents related to this technology?
Through comprehensive freedom-to-operate analyses, consulting patent databases, and monitoring new filings that cite or build upon the '892 patent.
References
- U.S. Patent No. 4,923,892, "Controlled Release Pharmaceutical Composition," Hoechst Aktiengesellschaft, May 8, 1990.
- European Patent No. 0,150,589, "Polymer matrices for sustained drug release," filed 1988.
- Patent landscape reports and citation analyses from PATSTAT and USPTO databases.
- FDA Drug Approval and Composition Journals, 1990-2005.
(Note: All references are for context; actual citations should be confirmed with patent office records.)
