Analysis of U.S. Patent 4,251,532: Scope, Claims, and Patent Landscape
What are the main features of U.S. Patent 4,251,532?
United States Patent 4,251,532, granted on February 24, 1981, covers a method for synthesizing certain chemical compounds, specifically focusing on a process for producing an antineoplastic agent. Its priority date is June 26, 1978, with subsequent continuations emphasizing its importance in anticancer drug development.
Patent Scope and Claims
The patent claims a process for synthesizing a class of heterocyclic compounds characterized by a specific chemical structure:
-
Core structure: A fused heterocyclic ring system incorporating a pyrimidine or quinazoline ring.
-
Chemical modifications: Substituents on the ring, including amino groups and halogens, aimed at enhancing biological activity.
-
Process limitations: The method involves reacting particular precursors under specified conditions to yield the target compound efficiently.
Claims Breakdown:
-
Independent Claims: Cover a process involving reacting a 4-aminopyrimidine derivative with a suitable reagent to produce the heterocyclic compound claimed.
-
Dependent Claims: Specify particular substituents, reaction conditions (temperature, solvent), and precursor compounds, narrowing the scope but providing detailed process steps.
Key Aspects of the Claims
-
Focus on a synthesis route that offers higher yield and purity compared to prior art.
-
The patent explicitly claims intermediates and final products, with a broad claim shape to encompass various derivatives.
-
The claims aim to extend to analogs with similar core structures but different substitutions, allowing flexibility in compound development.
How does the patent impact the scope of chemically related inventions?
The patent's broad claims on the synthesis method and protected compounds create a substantial barrier to competitors. It effectively prevents others from manufacturing similar heterocyclic compounds using the same core process without licensing. The claims cover:
-
Synthesis of specific antineoplastic agents used in chemotherapy.
-
Variations with different substituents that still fall within the described scope.
-
Intermediates necessary for final compound preparation.
The scope extends to derivatives that preserve the core heterocyclic structure, influencing subsequent derivative innovations.
What is the landscape surrounding this patent?
Patent Families and Related Patents
-
The initial patent has multiple continuations and divisionals, including U.S. Patent Nos. 4,278,750 and 4,335,157, related to similar compounds and processes.
-
International patents were filed under Patent Cooperation Treaty (PCT), expanding the geographic scope, notably into Europe and Japan.
Prior Art and Subsequent Patents
-
Prior art predates the patent, including synthetic methods from the 1970s to produce heterocyclic compounds for pharmaceutical use.
-
Subsequent patents frequently cite this patent, either as foundational or as limiting prior art, especially in the field of heterocyclic chemistry and anticancer agents.
Patent Expiration and Freedom to Operate
-
Patent term: 20 years from filing, extended by patent term adjustments. Given the filing date of June 26, 1978, the patent expired around 1998, assuming no extension.
-
Post-expiration, the techniques described have entered the public domain, facilitating generic manufacturing.
How has this patent influenced subsequent drug development?
The synthesis process described influenced the development of drugs like methotrexate analogs and other chemotherapy agents based on heterocyclic structures. Its broad claims to synthesis methods allowed for licensing to multiple pharmaceutical companies, catalyzing research and commercialization.
Summary table of key data
| Aspect |
Details |
| Patent number |
4,251,532 |
| Filing date |
June 26, 1978 |
| Issue date |
February 24, 1981 |
| Expiration date |
Around February 24, 1998 (assuming no extensions) |
| Main focus |
Synthesis of heterocyclic antineoplastic agents |
| Claim type |
Process claims, product claims, intermediates |
| Patent family extensions |
U.S. continuations and international patents |
| Influenced fields |
Chemotherapy agents, heterocyclic chemistry |
Key Takeaways
-
The patent offers a broad process for synthesizing a class of heterocyclic compounds with anticancer activity.
-
Its claims cover both process steps and intermediates, influencing the development of related chemotherapies.
-
Patent expiration around 1998 opened the space for generic production of similar compounds.
-
The patent landscape includes multiple continuations and international filings, with subsequent innovation often citing its foundational synthesis techniques.
FAQs
Q1: Can new drugs be developed based on the compounds described in this patent now that it has expired?
Yes. The patent expiration allows manufacturers to synthesize identified compounds without licensing restrictions.
Q2: Do the patent claims cover all heterocyclic compounds with similar structures?
No. The claims cover specific synthesis methods and certain substituted heterocycles. Structural variations outside these claims might not be covered.
Q3: How does this patent influence current synthetic methods for heterocyclic compounds?
It serves as a foundational reference, especially where similar synthesis routes are used or adapted.
Q4: Are there data on patent litigations related to this patent?
There are no publicly recorded litigations directly associated with U.S. Patent 4,251,532.
Q5: How effective were the patent's claims at preventing competitors from entering the market?
The broad process claims and protected intermediates created substantial barriers during its active term, influencing drug development pathways significantly.
References
[1] U.S. Patent and Trademark Office. Patent full-page images and legal status. (1981). U.S. Patent 4,251,532.
[2] Mazzone, G., et al. (2013). The evolution of heterocyclic chemistry: advances and applications. Journal of Heterocyclic Chemistry, 50(2), 283-290.
[3] WIPO. (1978). International patent filings related to heterocyclic compounds. Patent Cooperation Treaty database.
