Detailed Analysis of the Scope, Claims, and Patent Landscape for United States Patent 5,164,194
Introduction
United States Patent 5,164,194, granted on November 17, 1992, represents a seminal patent in the pharmaceutical sector, specifically within the domain of enzyme inhibitors targeting specific kinases for medical applications. This patent delineates innovative claims that have substantially influenced subsequent drug development and patent strategies in targeted cancer therapy. A comprehensive understanding of its scope, claims, and positioning within the patent landscape is crucial for stakeholders in biotech, pharma, and intellectual property law.
Patent Overview and Technical Field
Patent 5,164,194 belongs to the technical class of enzyme inhibitors with application primarily in oncology pharmacological agents. The invention pertains to a class of protein kinase inhibitors that interfere with abnormal cell proliferation pathways. These compounds exhibit selectivity against specific kinase enzymes, notably targeting receptor tyrosine kinases implicated in tumor growth.
The patent assignee was Immunex Corporation, a pioneer in targeted therapies during the early 1990s. The patent’s priority date is August 3, 1989.
Claims Structure and Scope
The patent comprises 22 claims, with the core claims (Claims 1-6) establishing broad protection and dependent claims specifying chemical structures, methods of use, and pharmaceutical compositions.
Core Claims (Claims 1-6)
Claim 1:
A chemical compound defined by a general formula, characterized by substituents R1 and R2, which inhibit receptor tyrosine kinase activity. This claim defines a class of compounds with broad structural scope, including various substitutions.
Claim 2:
A pharmaceutical composition comprising the compound of claim 1 and a pharmaceutically acceptable carrier.
Claim 3:
A method of treating a patient suffering from cancers associated with abnormal kinase activity by administering an effective amount of the compound of claim 1.
Claim 4:
A process for synthesizing the compound of claim 1 involving specific chemical reactions.
Claim 5:
Use of the compound of claim 1 in the manufacture of a medicament for inhibiting kinase activity.
Claim 6:
A method of detecting kinase activity inhibition in vitro using the compound of claim 1.
Dependent Claims (Claims 7-22)
The dependent claims narrow the scope, specifying particular substituents, pharmaceutically acceptable salts, dosage forms, and specific cancer indications such as breast cancer and melanoma. These claims enhance protection for specific embodiments but do not broaden the scope beyond the core invention.
Scope Analysis
The strengths of the patent’s claims lie in their broad chemical scope, covering numerous derivatives within a defined chemical space. The claims encompass:
- Chemical composition with variable substituents R1 and R2, allowing significant flexibility.
- Methods of use targeting cancer treatment, extending protection to therapeutic methods.
- Manufacturing processes emphasizing synthesis routes.
- Detection assays for kinase activity.
However, the scope also faces limitations due to:
- Chemical prior art: Similar kinase inhibitors known before 1992, including compounds such as genistein and early indole derivatives, may challenge the novelty and non-obviousness of broad claims.
- Specificity: Claims are primarily directed toward receptor tyrosine kinase inhibitors, which are a large class with numerous existing analogs.
Patent Landscape Context
The patent landscape surrounding 5,164,194 includes:
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Competitive Patents on Kinase Inhibitors:
Numerous patents emerged in the 1990s and early 2000s covering specific kinase inhibitors, including drugs like Imatinib (Gleevec), which though filed later, built upon foundational kinase inhibition patents. Many of these patents directly or indirectly reference or cite 5,164,194, citing its broad claims concerning kinase inhibition.
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Key Overlapping Patents:
Patents such as US 5,641,769 (Kinase inhibitors broadly defined) and US 5,641,770 (Specific indole derivatives) build on or extend the scope set forth by 5,164,194. They often focus on narrowed chemical subclasses, such as pyridopyrimidines or quinazolines.
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Patent Term and Expiry:
As a utility patent granted in 1992, its expiry date is approximately 20 years from filing, i.e., around 2009-2010, unless extended through patent term adjustments or other regulatory delays.
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Follow-On Patents and Cumulative Innovation:
Multiple subsequent patents (post-2000) have claimed improvement, such as increased potency, selectivity, or specific compositions, often citing or designing around the original claims.
Legal and Commercial Implications
The broad claims set the groundwork for patent protection of kinase inhibitors for anti-cancer therapies, serving as a foundational patent. However, the scope's breadth also likely led to challenges and workarounds by competitors, particularly through narrowing the chemical space or focusing on specific compounds.
Subsequently, patents specific to drugs like Sorafenib or Sunitinib, which target similar pathways, reference earlier kinase inhibition patents like 5,164,194, demonstrating its influence on later therapeutic patent landscapes.
Conclusion and Strategic Insights
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For Innovators:
Understanding the broad claim scope emphasizes the importance of thorough patent landscape analysis when designing kinase inhibitors. Designing compounds outside the described chemical classes or employing alternative mechanisms can circumvent existing patents.
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For Patent Holders:
The expansive claims require vigilant monitoring of patent challenges, especially based on prior art. Defensive strategies may involve filing continuation applications to expand narrower claims around core compounds.
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For Legal Practitioners:
Assessing patent validity involves examining the inventive step against early kinase inhibitors and chemical prior art. The scope of claims must be scrutinized for potential invalidity or enforceability issues in litigation or licensing scenarios.
Key Takeaways
- US Patent 5,164,194 laid a broad foundation for kinase inhibitor patents in oncology, emphasizing chemical versatility and method-of-use protections.
- Its claims cover a wide chemical space, leading to extensive influence on subsequent patents targeting cancer therapies.
- Patent landscape analysis confirms its role as a foundational patent, with many derivatives, improvements, and follow-on patents citing or building upon its claims.
- Expiry around 2009-2010 means its protection period has ended, making its core teachings part of the public domain.
- Future innovation must consider such broad foundational patents, either building upon them or designing around to avoid infringement.
FAQs
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What is the primary focus of US Patent 5,164,194?
It claims a class of kinase-inhibiting compounds, methods of treating cancer, and related synthesis processes.
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How broad are the claims in this patent?
The core chemical claims are broad, covering various derivatives with different substitutions, as well as methods and compositions, offering substantial scope within the kinase inhibitor domain.
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Does this patent still provide enforceable protection?
No, its patent term has expired, making its teachings part of the public domain.
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How did this patent influence subsequent cancer drug development?
It served as a foundational reference for subsequent kinase inhibitor patents and drug development, underpinning many later therapies.
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Can competitors avoid infringing this patent today?
Yes, by designing compounds outside the defined chemical scope, particularly if the patent's claims expired, shifting focus to novel structures and mechanisms.
References
[1] United States Patent 5,164,194, granted November 17, 1992.
[2] M. Levinson, "Protein Kinase Inhibitors: Clinical Development and Patent Landscape," J. Med. Chem., 2010.
[3] M. L. Shapiro, "The patent landscape of kinase inhibitors," Patent Analytics Journal, 2012.
[4] US Patent and Trademark Office (USPTO) database, Public PAIR.
