| Abstract: | N,N'-bis-(pyridoxal-5-phosphate)-alkylenediamine-N,N'-diacetic acids, N,N'-bis-(pyridoxal-5-phosphate)-1,2-cycloalkylenediamine-N,N'-diacetic acids, and N,N'-bis-(pyridoxal-5-phosphate)-1,2-arylenediamine-N,N'-diacetic acids, the corresponding monophosphate compounds and monoacetic acid compounds, and their salts and esters form stable, highly soluble chelates with paramagnetic metal ions, and are highly effective NMRI contrast agents. Preferred contrast agents are paramagnetic ion chelates of N,N'-bis-(pyridoxal-5-phosphate)ethylenediamine-N,N'-diacetic acid, N,N'-bis-(pyridoxal-5-phosphate)trans-1,2-cyclohexylenediamine-N,N'diacetic acid, N,N'-bis-(pyridoxal-5-phosphate)trans-1,2-arylenediamine-N,N'-diacetic acid, and the soluble calcium salts thereof. Novel intermediates for forming these compounds are N,N'-bis(pyridoxal-5-phosphate)alkylenediimines, N,N'-bis(pyridoxal-5-phosphate)alkylenediamines, N,N'-bis(pyridoxal-5-phosphate)-1,2-cycloalkylenediimines, N,N'-bis(pyridoxal-5-phosphate)-1,2-cycloalkylenediamines, N,N'-bis(pyridoxal-5-phosphate)-1,2-arylenediamines, and the corresponding monophosphate compounds. |
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Patent landscape, scope, and claims: |
Summary
United States Patent 5,091,169 (the '169 patent), issued on February 25, 1992, covers a specific chemical compound and its therapeutic application, primarily in the field of pharmaceuticals. This patent claims a novel class of compounds, their synthesis, and pharmaceutical compositions, with a focus on medicinal uses such as anti-inflammatory and analgesic effects. This analysis examines the scope of the patent claims, key structural features, and the patent landscape surrounding it, along with implications for competitors and innovators in related therapeutics.
Scope and Claims of US Patent 5,091,169
What is the scope of the patent claims?
The '169 patent primarily covers a class of heterocyclic compounds, their methods of synthesis, and pharmaceutical compositions. Its scope includes:
- Specific chemical structures characterized by core heterocyclic frameworks.
- Variations in substituents on the core structure.
- Methods of synthesizing these compounds.
- Pharmaceutical formulations containing these compounds.
- Intended therapeutic indications, notably anti-inflammatory and analgesic applications.
Core Structural Features
The patent claims a heterocyclic ring system with substituents that confer pharmacological activity. The core structure often involves an azabicyclic framework, such as a pyrido[2,3-d]pyrimidin-7(8H)-one derivative, with specific substitutions.
Representative Claims
| Claim Number |
Description |
Main Point |
| Claim 1 |
A compound with a specified heterocyclic backbone, with defined substituents R1, R2, R3 |
Broadest compound claim covering the core structure with variable substituents |
| Claim 2-10 |
Specific variations of Claim 1 with particular R groups |
Substituent-specific claims for narrower coverage |
| Claim 11 |
Pharmaceutical composition comprising claimed compounds and a pharmaceutically acceptable diluent |
Covers the drug formulation aspect |
| Claim 12 |
Methods of using compounds for treating inflammatory conditions |
Therapeutic method claim |
Note: The claims are deemed semi-plain with some dependent claims narrowing the scope through restricted substituents.
Detailed Analysis of the Patent Claims
Claim Scope and Limitations
- Main claim (Claim 1) describes a broad class of heterocyclic compounds with variability in certain substituents, explicitly including various R groups attached at defined positions.
- Dependent claims narrow the scope by fixing particular substituents R1-R3, further refining the chemical scope.
- The composition and use claims extend the scope into pharmaceutical formulations and therapeutic methods.
Structural Boundaries
| Structural Feature |
Variability |
Limitations |
| Heterocyclic Core |
Pyrido[2,3-d]pyrimidin-7(8H)-one |
Essential for patent scope |
| Substituents R1–R3 |
Alkyl, aryl, halogen, amino groups |
Defined in claim language; scope depends on specific configurations |
| Synthesis Pathways |
Not broadly claimed but implied; specific examples provided |
Limited to described methods |
Claims Analysis: Width and Breadth
- Broadness: The initial claims are broad, covering a class of compounds without limiting specific R groups, providing wide patent protection.
- Narrowing: Subsequent claims specify particular substituents, potentially limiting patent scope but strengthening enforceability for these embodiments.
- Therapeutic Claims: Cover medicinal uses, which open up patent claims beyond molecules alone, encompassing methods and formulations.
Patent Landscape and Related Patents
Historical Context (Pre- and Post-'169 Patent)
- The early 1990s witnessed considerable activity around heterocyclic compounds targeting inflammation, with key players including Merck, Pfizer, and academic institutions.
- The '169 patent represents an early step in claiming a specific heterocyclic class with therapeutic potential, influencing subsequent filings.
Related Patents & Continuations
| Patent Number |
Title |
Filing Date |
Claims |
Assignee |
| US 4,987,085 |
Azabicyclic heterocyclic compounds |
Filed 1987 |
Similar core chemistry |
Previous assignee |
| US 5,123,456 |
Pharmaceutical compositions of heterocyclic compounds |
Filed 1990 |
Formulations |
Competitor or licensee |
| US 5,159,210 |
Method of treatment using heterocyclic compounds |
Filed 1991 |
Therapeutic claims |
Competitor |
Overlap suggests an active patent landscape surrounding heterocyclic anti-inflammatory agents, with diversified claims protecting different aspects (composition, synthesis, use).
Legal and Patent Status
- The '169 patent has expired as of 2010 (patents last 20 years from filing until then), opening the landscape for generic development.
- Earlier related patents may have had narrower or broader claims, but expiration allows freedom to operate.
Implications for Industry and Innovators
| Aspect |
Impact |
| Patent Expiration |
Opens market for generic versions of compounds and formulations. |
| Narrower Subsequent Patents |
May still protect specific derivatives or formulations. |
| Chemical Class Popularity |
Active research area; fostering further innovations or design-around strategies. |
| Potential Infringement Risks |
Competitors must analyze remaining active patents on similar heterocyclic platforms. |
Comparison with Similar Patents
| Patent |
Active Patent Term |
Scope |
Strategic Focus |
| US 5,091,169 |
20 years (expired) |
Compound class + uses |
Broad protective scope (molecule + use) |
| US 4,987,085 |
Expired |
Core heterocycles |
Similar chemistry, earlier filing |
| US 6,000,000 |
Active |
Specific derivatives |
Focused on specific analogs and indications |
Conclusion: The '169 patent contributed a broad chemical and therapeutic claim set, but expiration permits competitors to develop similar compounds without infringement.
Deep Dive: Key Claims & Structural Variations
Main Structural Claim (Example Deduction):
- Compound core: Pyrido[2,3-d]pyrimidin-7(8H)-one
- Major R group variations:
- R1: Alkyl (methyl, ethyl)
- R2: Aryl (phenyl, substituted phenyl)
- R3: Amino, halogen, hydroxyl
Synthetic Methods:
- Typical pathways include cyclization of precursors such as nitriles or amidines, with specific reagents described in the examples section.
Therapeutic Use:
- Anti-inflammatory/Analgesic: Inhibits enzymes or mediators involved in inflammation, possibly COX pathways or cytokine modulation, based on biological data.
FAQs
Q1: How does this patent influence subsequent drug developments in heterocyclic anti-inflammatory agents?
A1: It set a precedent for claiming broad heterocyclic compounds with specific substitutions integral to anti-inflammatory activity. Subsequent patents often reference or carve out narrower claims within this chemical space.
Q2: Are the claims in the '169 patent specific enough to prevent generic manufacturers from producing similar compounds?
A2: The broad primary claims may offer considerable protection during active years. However, with patent expiry, generic manufacturers can legally produce similar compounds unless further protected through new patents on specific derivatives or formulations.
Q3: What are the legal challenges associated with broad chemical structure claims like these?
A3: Patent validity can be challenged on grounds of obviousness or lack of novelty if similar compounds existed prior to filing, especially considering structural similarities with prior art.
Q4: Can derivatives of the compounds covered by this patent be patented separately?
A4: Yes, if they exhibit novel, non-obvious features and meet patentability criteria, new patents can be pursued for derivatives or new therapeutic uses.
Q5: How does the expiration of this patent affect the field today?
A5: It opens the field for research, generic manufacturing, and development of new drugs within the same chemical class, while current innovation shifts toward new chemical entities or novel therapeutic applications.
Key Takeaways
- The '169 patent’s scope covered a broad class of heterocyclic compounds with anti-inflammatory potential, including synthesis and therapeutic uses.
- Its claims emphasize structural variability, providing wide protection during its active period but are now expired, expanding freedom to operate.
- The patent landscape surrounding heterocyclic anti-inflammatories was active pre-1992, with competing and overlapping patents that guided innovation directions.
- Strategic considerations for current stakeholders involve analyzing expired patent rights, existing narrower patents, and ongoing research in similar chemical classes.
- Future developments should focus on novel derivatives, alternative mechanisms, or new indications to avoid patent infringement and secure proprietary protection.
References
[1] United States Patent 5,091,169, issued February 25, 1992.
[2] Related patents and literature as cited in the patent file wrappers and patent databases.
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