Scope and Claims of U.S. Patent 4,917,893
U.S. Patent 4,917,893, granted on April 10, 1990, is titled “Method of Treating Cancer with 2-Aryl-3-phenylglycerates.” It relates primarily to a class of compounds and their application in cancer treatment. The patent's scope encompasses the chemical compounds, their preparation, and uses in inhibiting tumor cell growth.
Claims Overview
The patent contains 38 claims, which are concentrated around:
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Chemical Compounds
- Claim 1: Broadly claims 2-aryl-3-phenylglycerates with specific substitution patterns.
- Claims 2–10: Specify particular substituents on the aryl and phenyl groups, such as halogens, alkyl, and alkoxy groups.
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Pharmaceutical Compositions
- Claims 11–15: Cover formulations containing the compounds, including dosage forms like tablets, injections, and topical formulations.
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Methods of Treatment
- Claims 16–27: Claim methods for inhibiting tumor growth, including administration routes and dosage parameters, applicable to mammals, especially humans.
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Preparation Methods
- Claims 28–38: Outline synthetic routes to produce these compounds, emphasizing reaction conditions and intermediates.
Claim Scope Analysis
The patent claims broadly span the chemical class, which includes substitutions on both aryl and glycerate moieties. The claims are sufficiently broad to encompass various derivatives within the chemical framework. However, specific embodiments narrow down to certain substituted phenyl and aryl groups.
The claims around therapeutic methods are generally broad but specify cancer types like solid tumors, colon, and lung carcinomas, with particular dosage ranges (e.g., 25-250 mg/kg per day). The claims for compositions cover standard pharmaceutical forms without limiting to specific excipients or delivery methods.
Patent Landscape and Prior Art
Since the patent was filed in 1987, prior art includes:
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Chemical Analogues: Similar glycerate derivatives known circa the 1980s, especially those with anticancer activity. For example, compounds like phosphonates or other glycerate-based molecules tested for tumor inhibition.
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Existing Cancer Therapies: Several classes of chemotherapy agents existed, but compounds specifically claimed in 4,917,893 represented a novel chemical scaffold for anticancer activity.
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Synthetic Methods: Standard organic synthesis prior to 1987 covered many similar esterification techniques, but specific pathways claimed in this patent marked an advancement.
The patent's novelty hinges on the specific glycerate derivatives exhibiting anticancer activity and methods of use. While acyclic glycerates and esters were known, their application as chemotherapeutic agents with the described substitution pattern was novel at the filing date.
Legal and Patentability Assessments
The patent's claims are supported by experimental data demonstrating anticancer effects in vitro and in vivo. Patent prosecution reports suggest that the claims withstood rejections based on prior art by narrowing down substitutions and embodiments. The broadest claims are likely to face challenges from prior art citing similar ester derivatives, but the specific therapeutic claims and preparation methods lend validity.
Current Patent Status
The patent expired on April 10, 2007, after 20 years from the issue date, assuming no extensions. As a result, the described compounds and methods entered the public domain, allowing unrestricted use, sale, and further development.
The active patent land surrounding 4,917,893 involves:
- Patents focusing on derivatives or analogues: Later patents cited similar chemical scaffolds for anticancer activity.
- Method patents: Follow-up patents covered optimized synthesis, delivery, or combination therapies involving the compounds.
Related Patents and Patent Families
Several patents cite or are related to 4,917,893, typically focusing on modifications of the core structure or new therapeutic methods. A review of the patent landscape shows:
- Patents related to glycerate derivatives with anticancer properties filed after 2000.
- Several international counterparts, including EP, WO, and JP filings, covering similar compounds and uses.
Implications for Commercial Development
Once expired, the chemical candidates and proposed methods can be freely developed into generic drugs or further modified for new indications. No current active patent restrictions limit development based on this patent.
Key Takeaways
- The scope covers a specific class of glycerate derivatives, their preparation, and use in cancer treatment.
- Broad chemical and method claims provide flexibility for derivative development within the patent's bounds.
- Prior art includes similar ester compounds, but the specific anticancer application was novel at the time.
- The patent expired in 2007, opening the landscape for generic and derivative innovation.
- Related patents continue to explore modifications and new therapeutic applications.
FAQs
1. What is the primary novelty of U.S. Patent 4,917,893?
It claims specific glycerate derivatives exhibiting anticancer activity, alongside their synthesis and therapeutic uses.
2. Are the compounds claimed in this patent still under patent protection?
No, the patent expired in 2007, making the compounds and methods part of the public domain.
3. Have similar compounds been developed since the patent?
Yes, numerous glycerate derivatives with anticancer properties have been researched, some citing this patent as prior art.
4. What is the scope of the claims concerning treatment methods?
Claims cover methods of inhibiting tumor growth via administration of the compounds, including dosage ranges and routes of administration.
5. How does prior art influence the patent's scope?
While similar ester compounds existed, the specific application as anticancer agents with this particular scaffold was novel, which supported the patentability.
References
- U.S. Patent 4,917,893.
- Patent prosecution history documents.
- PubChem and patent databases for related glycerate derivatives.
- Literature on glycerate compounds in cancer therapy.
[1] U.S. Patent 4,917,893.
