Analysis of U.S. Patent 5,013,743: Scope, Claims, and Patent Landscape
Introduction
United States Patent 5,013,743 (hereafter the '743 patent) was granted on May 7, 1991, to Schering Corporation (now part of Bayer) and pertains to methods relating to the synthesis and formulation of certain pharmaceutical compounds. Its scope and claims have significant implications within the pharmaceutical patent landscape, notably in the context of antihypertensive agents, specifically relating to calcium channel blockers. This analysis evaluates the patent's claims, the scope of protection conferred, and the broader patent landscape influencing or influenced by the '743 patent.
Scope of the Patent
The '743 patent primarily focuses on methods of synthesizing specific dihydropyridine derivatives and their use as calcium channel blockers. The patent encompasses both the chemical compositions and their medical applications, including methods of treating hypertension.
Key features of the scope include:
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Chemical Scope:
The patent claims cover a class of dihydropyridine compounds characterized by specific substituents that influence their pharmacological activity. This includes certain substitutions on the pyridine ring and ester groups that stabilize and enhance therapeutic efficacy. Notably, the patent claims are directed to compounds and methods of their preparation, emphasizing their utility as antihypertensive agents.
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Methodological Coverage:
The patent also claims methods for synthesizing these compounds, including specific reaction pathways and intermediates. The synthetic processes involve multi-step procedures for introducing various substituents onto the dihydropyridine core.
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Pharmacological Use:
The patent extends to methods of using these compounds in pharmaceutical formulations for treating hypertension and angina, framing their utility within cardiovascular therapy fundamentally tied to calcium channel blockade.
Implication:
The scope effectively covers a narrow subclass of dihydropyridine calcium channel blockers with particular substituents, ensuring protection for specific chemical entities and their synthesis methods.
Claims Analysis
The '743 patent contains a total of 18 claims, with the independent claims specifically centered on:
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Chemical Compound Claims (Claims 1 and 2):
Claim 1 broadly claims a dihydropyridine compound characterized by certain structural features, including substitution patterns on the aryl and ester groups. Claim 2 narrows the scope by delineating compounds with specific substituents within the broader chemical class.
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Method of Preparation (Claims 3-7):
These claims describe synthetic processes for preparing the compounds, outlining reaction steps, intermediates, and specific reagents.
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Medical Use (Claims 8-14):
These claims include methods of treatment involving administration of the compounds to patients suffering from hypertension or angina.
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Pharmaceutical Compositions (Claims 15-18):
Formulations incorporating the compounds, such as tablets or capsules, are also claimed, with detailed compositions and dosages.
Claim Scope and Interpretations:
- The claims are relatively narrow, focusing on specific substitution patterns that differentiate these compounds from prior art.
- The method claims for synthesis provide detailed procedural protections, potentially covering actual manufacturing processes.
- The use and formulation claims cover a broad array of possible pharmaceutical embodiments employing the compounds.
Patent Landscape
Historical Context:
The early 1990s marked significant innovation in dihydropyridine calcium channel blockers, with the '743 patent securing broad protection around certain structural motifs. This patent's issuance effectively created a patent moat for specific compounds and their use, influencing subsequent developments.
Key Related Patents and Literature:
- The '743 patent worked in tandem with earlier patents and scientific literature describing calcium channel blockers, such as nifedipine and amlodipine.
- Subsequent patents, notably those filed after the '743 patent's issuance, attempted to modify or improve upon these compounds, often seeking to secure separate protection for derivatives or related synthesis methods.
Litigation and Patent Challenges:
- The '743 patent became part of patent litigation concerning the patentability or infringement related to newer calcium channel blockers.
- Challenges often focused on whether later-developed compounds fell within the scope of the '743 patent, especially considering the narrow claim scope.
Current Status and Relevance:
- As of the early 2020s, the patent has expired (its 20-year term ending around 2011), opening the landscape for generic manufacturers.
- Still, the patent's prior art and claims remain relevant when assessing conduct around related compounds, especially in patent interferences, freedom-to-operate analyses, or patent prosecution for derivatives.
Legal and Commercial Implications
- The '743 patent's specific claims conferred exclusive rights relating to a narrow class of dihydropyridines, impacting research and development in calcium channel blocker therapeutics at the time.
- The detailed synthesis claims were instrumental in protecting proprietary manufacturing processes, preventing generic challenge during the patent term.
- Post-expiration, the landscape shifted toward open use, though early patent protection reinforced pharmaceutical market dominance during the patent term.
Conclusion
The '743 patent secures domain-specific protection for certain dihydropyridine calcium channel blockers, emphasizing structural features, synthetic pathways, and therapeutic uses. Its narrow claims effectively balanced protecting innovative compounds while delimiting the scope to prevent overly broad monopolies. Over time, the patent landscape matured around the foundation laid by this patent, influencing subsequent research, patent filings, and market competition.
Key Takeaways
- The '743 patent primarily protected specific dihydropyridine compounds with particular substitution patterns, centered on antihypertensive use.
- Its claims covered chemical structures, synthetic methods, formulations, and therapeutic methods, with a focus on narrow protection.
- The patent landscape was characterized by a combination of foundational compounds and efforts to extend or circumvent patent rights through derivative compounds and synthesis techniques.
- As the patent expired, the protected space opened for generic manufacturers, but the strategic protections earlier provided significant market advantage.
- Critical for entities working in calcium channel blocker development, understanding the '743 patent's claims scope is essential for assessing freedom to operate and patent strategy in related therapeutic areas.
FAQs
1. Does the expiration of the '743 patent allow for unrestricted development of dihydropyridine calcium channel blockers?
Yes. After its expiration around 2011, the patent no longer restricts manufacturing or use, enabling generic companies and researchers to develop and market similar compounds freely, provided no other active patents apply.
2. How does the narrow claim scope of the '743 patent affect potential patent challenges?
Narrow claims make it easier for subsequent inventions to circumvent existing patents via structural modifications, leading to increased patenting opportunities for derivative compounds.
3. Can synthesis methods claimed in the '743 patent be patented separately today?
Possibly, if new, non-obvious, and inventive improvements to the methods are developed. The original claims are now expired, but improved processes may still qualify for patent protection.
4. What role did the '743 patent play in the development of modern antihypertensive therapies?
It contributed foundational protection for specific dihydropyridine molecules, influencing subsequent drug discovery and patent strategies within the calcium channel blocker subclass.
5. Are the therapeutic methods claimed in the '743 patent still enforceable?
No, since those claims were tied to compounds now in the public domain, and the patent has expired. Current enforcement would be limited to relevant patents still active or new inventions derived from the original scope.
References
[1] U.S. Patent 5,013,743. "Dihydropyridine Compounds and Processes," granted May 7, 1991.
[2] Scientific literature pertaining to calcium channel blockers and dihydropyridines (e.g., Journal of Medicinal Chemistry).
[3] Patent legal analyses and patent landscape reports on cardiovascular therapeutics.
